LETTERS, &c 
 
 Let. 
 
 a 
 
LETTERS 
 
 FROM 
 
 DR. JAMES GREGORY 
 
 * r OF EDINBURGH, 
 
 .'& IN 
 
 ^7 
 
 DEFENCE OF HIS ESSAY 
 
 ON THE DIFFERENCE OF THE RELATION BETWEEN MOTIVE 
 
 AND ACTION AND THAT OF CAUSE AND 
 
 EFFECT IN PHYSICS: 
 
 WITH 
 
 REPLIES 
 
 BY THE 
 
 REV. ALEX. CROMBIE, LL. D, 
 
 LONDON : 
 
 Printed by A. J. Valpy, Tooke's Court, Chancery Lane. 
 
 PUBLISHED BY R. HUNTER, NO. 72, ST. PAUL'S 
 CHURCH YARD. 
 
 1819. 
 
PREFACE. 
 
 IT is proper to acquaint the reader with the circum- 
 stances, which have given occasion to the follow- 
 ing letters. In the year 1792, Dr. Gregory pre- 
 sented to the public an Essay in two volumes 8vo,* 
 in which he assumed the merit of disproving the 
 doctrine of Philosophical Necessity by Mathema- 
 tical evidence. His reasoning appeared to me 
 wholly fallacious ; and in an Essay, in defence of 
 this doctrine, published about a year afterwards, 
 I endeavoured to demonstrate the invalidity of 
 
 1 Dr. G., in his first Letter, has called his work, An Essay 
 on the difference between the relation of motive and action and 
 that of cause and effect in physics. The title is correct and 
 appropriate. I have therefore, in order to prevent misconcep- 
 tion, ventured to adopt it, in preference to that which appears 
 in the title page of the work itself, namely, Essays Philosophi- 
 cal and Literary, from which it would naturally be concluded, 
 that there are several Essays, and these also on a diversity of 
 subjects. 
 
 Let. b 
 
VI 
 
 his argument; and, at the same time, took the 
 liberty to reprehend the insolence, and the illibera- 
 lity, with which he treated his opponents. Soon 
 after the publication of my Essay, I was informed, 
 that it was Dr. Gregory's intention to reply to my 
 strictures ; and that I had reason to expect a se- 
 vere retort, for my animadversions on his work. 
 Neither pleased, nor alarmed, at this information, 
 I waited two or three years, in expectation of Dr. 
 Gregory's reply ; and at last concluded from his 
 silence, either that he had relinquished his intention, 
 or that my information must have been* incorrect. 
 My conclusion, however, was erroneous. After 
 the lapse of ten years, I received, in the month 
 of October 1803, the first letter of the following 
 series, accompanied with a short communication, 
 informing me, that his Answer to my animadver- 
 sions was nearly ready for the press, and that, as 
 soon as the Session of College was over, I might 
 expect to see it in print ; unless my reply to his 
 first letter should convince him of the justness of 
 my reasoning, or the invalidity of his own. He 
 assured me at the same time, that, if I could point 
 out any fallacy in his argument, his intended pub- 
 
Vlf 
 
 lication should be suppressed, that his error should 
 be acknowleged, and that I should have his per- 
 mission to make that acknowlegement public. He 
 requested also to know, whether I chose to have 
 the remainder of the letters transmitted to me "seri* 
 " atim" or all together. My reply, dated in January 
 1804, with a few additions and alterations, is here 
 submitted to the judgment of the reader. It was ac- 
 companied with a communication, expressing my 
 desire to avail myself of his offer, and to receive the 
 remaining letters, either individually or collect- 
 ively, as he might prefer. I had reason, therefore, 
 to expect, that these letters would be sent to me, 
 agreeably to Dr. Gregory's voluntary promise. I 
 had reason likewise to expect, either that the whole 
 would be published in the ensuing spring, or that 
 he would acknowlege his argument to be fallacious. 
 My expectations however were disappointed. 
 Neither were the remaining letters transmitted to 
 me, nor did Dr. Gregory publish his Defence, nor 
 did he acknowlege himself in any error, or retract 
 his argument. Conceiving myself justified in re- 
 quiring an explanation of this extraordinary proce- 
 dure, but unwilling to urge him to any precipitate 
 
Vlll 
 
 determination, I suffered five years more to elapse, 
 and Dr. Gregory was still silent ; nor was I fa- 
 voured with a perusal of the remainder of his 
 Defence. Of this conduct I found it difficult even 
 to conjecture any satisfactory explanation, without 
 resorting to the very unfavourable suspicion, that 
 my reply to his first letter had convinced him of 
 his error, but that he wanted the candour and 
 magnanimity to acknowlege it. 
 
 If he was persuaded, that his argument was 
 demonstrative, and his Defence unanswerable, it 
 is to be presumed, that, with this conviction, he 
 would have published his letters, as he gave me 
 reason to expect. If, on the contrary, he was con- 
 vinced, that his reasoning was fallacious, and that 
 his arguments were refuted by my first letter, it 
 became his duty, in conformity to his express 
 promise, candidly and explicitly to acknowlege 
 his error. On either supposition his conduct ap- 
 peared irreconcileable with his engagements, as 
 either clearly implied or positively expressed. I 
 took the liberty, therefore, in a letter, dated in 
 March 1809, to remind him of his promise, and 
 requested to be informed, whether he intended to 
 
IX 
 
 publish his Defence, or retract his argument. In 
 answer, I received six letters, and part of a seventh, 
 all printed, accompanied with a pretty long epistle, 
 giving me full permission to publish all, or any 
 part, of these letters, in answer to my strictures ; 
 assuring me, at the same time, of his " hearty 
 " inclination to proceed." It appeared to me, and 
 perhaps may appear to the reader, somewhat ex- 
 traordinary, that a work, which, the author had 
 signified, was nearly ready for the press, and 
 might be expected to appear in six months, and 
 of which, after the expiration of these six months 
 208 pages were actually printed, could not be 
 completed in five years afterwards, making every 
 allowance for the interruptions occasioned by 
 professional engagements, which few can feel more 
 sensibly than myself. 
 
 Having finished my replies to these letters, I 
 informed Dr. Gregory, that, as he had neither 
 published his answer, nor retracted his opinion, 
 one or other of which alternatives he had given me 
 reason to expect, it was my intention to avail my- 
 self of his permission to publish his letters with 
 my Replies. To this intimation I was favoured 
 
with an answer, in which he requested, that I 
 would either transmit to him the manuscript, before 
 it was sent to the printer, or the proof sheets, 
 one after another, as they proceeded from the 
 press. The former alternative, for obvious rea- 
 sons, was to be preferred; a manuscript copy 
 was accordingly sent to him, with an assurance, 
 that I should have pleasure in correcting any error 
 or mis-statement, into which I might inadvertently 
 have fallen, and in giving him an opportunity of 
 making any alteration, either in the matter, or 
 the manner, of his Defence, which he might deem 
 necessary. Dr. Gregory has been in possession of 
 my Replies for nearly five years, during which time 
 he has observed an entire silence. I am, therefore, 
 it is conceived, warranted in concluding, that he 
 considers his letters to be a full and satisfactory 
 answer to my animadversions. For, if my replies 
 have convinced him, that his argument is fallacious, 
 and that he erred in impeaching the veracity of his 
 opponents, it can scarcely be supposed, that he is 
 so devoid of all candour, as well as of that sacred 
 regard, which is due by every man to an express 
 and voluntary promise, as not to acknowlege that 
 
XI 
 
 his reasoning is false, and that his treatment of 
 Necessarians is illiberal and unjust. Nay, if he 
 has discovered, that his letters are not a valid and 
 satisfactory reply, but believes, that he is still 
 capable of offering a complete justification of his 
 reasoning and his conduct, it may, on this suppo- 
 sition, be fairly presumed, that he would have 
 revoked his permission to publish his Defence, and 
 requested me to wait for a farther communication. 
 Nor is it unreasonable to presume, that the space 
 of five years, during which time my Replies have 
 been in his possession, would have amply sufficed 
 for this purpose. . , 
 
 If Dr. Gregory should proceed, of which I 
 entertain no sanguine expectation, his future ob- 
 servations, if not composed of irrelevant matter, or 
 of groundless or frivolous complaints, shall receive 
 from me every possible attention. In the mean 
 time, the following letters will suffice to exhibit the 
 nature of his argument, and the character of his 
 Defence, of the validity of which the reader will 
 judge. 
 
 A. C. 
 
ERRATA ET CORRIGENDA. 
 
 p. 143 line 4, for you, read Urn. 
 
 p. 158 line 7, for Agebraic read Algebraic. 
 
 p. 272 line 20, for these conclusions read this conclusion. 
 
 p. 354 last line, for or read for. 
 
 p. 356 line 15, for respect read respects. 
 
FROM DR. GREGORY. 
 
 LETTER I. 
 
 SIR, 
 
 TEN years have now elapsed since you published 
 your Essay on Philosophical Necessity : one hundred 
 pages of which you have employed in discussing 
 my Essay on the Difference between the Relation of 
 Motive and Action, and that of Cause and Effect in 
 Physics. 
 
 In those pages you have treated not only my 
 argument, but myself personally, with very little 
 ceremony. Of that I do not complain ; and, far 
 from taking it amiss, have been highly gratified by 
 it. You will, of course, expect as little ceremony 
 from me, in the answer to that part of your Essay 
 which relates to my argument. Such an answer, 
 from me, you will probably see some time in the 
 course of next year ; perhaps in spring. 
 
 In one respect, however, I cannot think it right 
 to follow your example, or to deviate from that 
 plan, which, you know, I adopted with DR. 
 PRIESTLEY ; and mean invariably to pursue, in 
 every discussion, or controversy, that I may have 
 with men of science. 
 
 Let. A 
 
You know that I sent DR. PRIESTLEY a copy of 
 my Essay, long before it was published ; and 
 assured him, that if he could point out any error 
 in it, or state any objection to it which I could 
 not answer easily and completely, so as to convert 
 it into an illustration of my own mode of reason- 
 ing, I should instantly suppress my work, and 
 commit it to the flames ; and most gratefully ac- 
 knowledge my obligations to him for setting me 
 right, and his superiority in reasoning. Before I 
 published my Essay, I had made the same offer to 
 every Necessitarian of my acquaintance ; and had 
 received from several of them various objections to 
 my argument; none of which appeared to me 
 valid : nay, there was but' one person, who, after due 
 "consideration, and seeing my mode of answering 
 his objections, had such confidence in them, as to 
 allow me to publish them, with my answers sub- 
 joined. The objections of that Necessitarian, with 
 my answers to them, are published, at full length, 
 in, the Appendix to my Essay. 
 
 You know that DR. PRIESTLEY did not choose 
 to avail himself of my very candid and liberal offer. 
 You know also in what a strange unaccountable 
 manner DR. PRIESTLEY'S friend and brother Neces- 
 sitarian MR. COOPER behaved to me, after DR. 
 PRIESTLEY had put into his hands my Essay, with 
 a view, as I believe, that MR. COOPER might con- 
 sider and answer it. He (MR. COOPER) repeatedly 
 
I 
 
 promised to give me his objections to my argument, 
 but repeatedly broke his promise. 
 
 Perhaps you do not know that DR. PRIESTLEY, 
 when he received the copy of my Essay, with the 
 letter containing the offer which I have stated, ac- 
 knowledged the receipt of it in the following terms : 
 " I have this day and hour received your Essay on 
 Motives and Actions, together with a letter, which 
 does you the greatest honor." Now, if my conduct 
 towards DR. PRIESTLEY and other Necessitarians, 
 in giving them an opportunity to consider my argu- 
 ment before I published it, was upright and honor- 
 able, and such as one man of science owes to 
 another; must not the directly opposite conduct, 
 such as you have followed with respect to me, be 
 just the reverse ? 
 
 You must have seen, from various passages of 
 my Essay, that I even engaged, that if any person 
 who chose to answer it, or object to it, after it came 
 forth, would let me peruse his argument before it 
 was published, I should give him either an explicit 
 acknowledgment that I thought his reasoning valid, 
 (and my own of course erroneous,) or else should 
 give him my reasons for thinking his argument 
 fallacious, and my own valid ; and should allow 
 him to publish such acknowledgment, or reasons, 
 of mine, along with his own argument. (See and 
 compare my Essay, page 89. line 23. to p. 92. T. 
 
10. ; p. 456, 457 ; and Introduction, p. 271. to 283 ; 
 and p. 311. 1. 4. to p. 315. 1. 19.) 
 
 I could contrive no temptation, in my opinion, 
 stronger than such an offer on my part, to induce any 
 one, who bonafick engaged in the controversy, to act 
 candidly. Such an acknowledgment from me 
 would surely have been a matter of triumph to such 
 a person. Any uncandid or frivolous objections 
 from me would have been still more gratifying, by 
 incnntestabty establishing his superiority in argu- 
 ment, and making me justly, and on the evidence 
 of my own act and deed, an object of severe re- 
 proach and general contempt. 
 
 On the other hand, to neglect or reject such an 
 offer as I made, appears to me exactly equivalent 
 to a formal renunciation of all pretensions to candor 
 in the argument ; and to an avowal of a resolution 
 to steal an apparent and temporary victory, by 
 means which the person employing them knows 
 to be disingenuous and sophistical. 
 
 One great advantage of such a liberal communi- 
 cation of any objections or arguments which a per- 
 son engaged in a controversy intends to publish* 
 is, that it prevents the possiblity of any mistake, and 
 precludes the suspicion of any wilful misrepresenta- 
 tion, on his part, of the meaning, the assertions, or the 
 arguments of his opponent. I need not tell you 
 that such mistakes have been very common, and 
 that such wilful misrepresentations have been much 
 
more common, among controversial writers, and 
 that they are peculiarly disgraceful. 
 
 If you had allowed me to peruse, before you 
 published it, that part of your Essay which relates 
 to my argument, I could easily have prevented 
 you from falling into many such mistakes, with re- 
 spect to the very nature and general tenor of my ar- 
 gument, as well as with respect to many particular 
 propositions which you have stated as mine, and 
 have been at much pains to discuss and refute ac- 
 cordingly: as well as with respect to many particular 
 passages which you profess to quote either verbatim, 
 or faithfully in substance, from my work. 
 
 As you did not allow me to peruse your answer 
 to my argument before you published it, notwith- 
 standing the many strong and obvious considera- 
 tions which might have induced you to do me 
 that justice, I, though a zealous assertor of the 
 liberty of human actions, must believe that you had 
 other, motives, which you thought stronger, for pub- 
 lishing you work without allowing me to see it ; 
 and you, as an orthodox Necessitarian, must hold 
 that your motives for acting as you have done, 
 were irresistibly strong, and that you could not bona 
 jidc. have acted otherwise. I could only guess at 
 your motives, but you no doubt can state them with 
 precision and certainty. If you have no valid 
 objection, that is, no irresistible motive for conceal- 
 ing those motives, I wish you would mention what 
 
a 
 
 they are ; for the most natural and obvious suppo- 
 sition with respect to them, is not the most favor- 
 able to you ; namely, a strongly felt consciousness, 
 that, however ingenious and plausible your argu- 
 ments were, and however well suited to the taste, 
 and knowledge, and understanding of those whom 
 you expected to h?ive for readers and admirers, they 
 yet could not stand the brunt of my rigorous mode 
 of reasoning. 
 
 For my part, though I am no Necessitarian, but 
 on the contrary a firm believer in the liberty of 
 human actions, and in the self-governing power of 
 man, and have no douut that I could easily behave 
 towards you as you have done towards me, and 
 publish my answer to your remarks without allow- 
 ingyoutosee one word of it, or giving you an oppor- 
 tunity to prevent my doing you any injustice, by 
 mistaking or misrepresenting your assertions and 
 reasonings ; yet I do not choose to act in that man- 
 ner, not from caprice, because I think I have many 
 good motives for acting in the very opposite manner. 
 
 Of these motives, and of the relation between 
 them and my conduct towards you, or what you 
 will probably call the force of them, you shall (if 
 you please) soon have an opportunity of judging. 
 It is my wish and intention, if you will allow me, 
 to submit to your revision every sentence of my 
 answer to you before it is published. If agreeable 
 to you, you shall receive it section by section, 
 
rather than all at once : for it is at least possible that 
 your remarks on some parts or sections of it may 
 greatly modify, or altogether prevent, some of those 
 observations and reasonings which otherwise would 
 have followed them. Your remarks must at least 
 prevent any mistakes on my part with respect to 
 certain matters of fact, on which I mean to make 
 some observations. If you will have the goodness 
 to point out to me any defects or errors in the 
 reasonings and illustrations that I employ, I shall 
 consider your doing so as a very particular favor : 
 but such a request I cannot presume to urge any 
 farther than is agreeable to yourself. With respect 
 to certain points of fact about which it would be 
 peculiarly disgraceful to one or both of us to differ, 
 I shall expect with confidence, that you will give 
 me explicit answers to a few precise questions that 
 I shall propose. My claim to such explicit answers 
 from you, if not strictly speaking a matter of right, 
 at least approaches very near to it ; for it would be 
 wrong in you to refuse it : not only uncandid with 
 respect to me, but imprudent with respect to your- 
 self and your own cause. When 1 give you an 
 opportunity either to admit, or to deny and refute, 
 any supposed matter of fact, of which I conceive 
 I have good evidence already, and of which I mean 
 to avail myself in answering your remarks on my 
 Essay; if you do not refute, or at least expressly con- 
 tradict it, you must be understood to admit it. 
 
For example : Is it true that DR. PRIESTLEY read 
 and approved your remarks on my Essay ; and that 
 be advised, and even urged, you to publish them? 
 
 These things I believe, on the authority which 
 I shall state to you. Soon after your Essay was 
 published, and some months before I could pro- 
 cure a copy of it, my friend and quondam guardian, 
 the late MR. PROFESSOR THOMAS GORDON, of 
 King's College, Aberdeen, told me that your friend 
 MR. PATERSON, who was for some time, and for 
 aught I know still is, teacher of mathematics at the 
 Charter-house, had mentioned to him, that you 
 had become acquainted with DR. PRIESTLEY, and 
 had put your manuscript into his hands ; that he 
 (DR. PRIESTLEY) had signified to you his approba- 
 tion of the work, and advised you by all means to 
 publish it : that you objected the expense, which 
 the sale was not likely to reimburse : upon which 
 DR. PRIESTLEY said to you, that, if you had any 
 doubts of that kind, he would be at the expense of 
 paper and printing. 
 
 MR. GORDON, at my desire, introduced the 
 same subject more than once, in conversation with 
 MR. PATERSON ; who always gave precisely the 
 same account of it. 
 
 Some years afterwards, I received by a different 
 channel the same kind of information. A Reverend 
 Clergyman told me that MR. (or DR.) LINDSAY 
 
9 
 
 had mentioned to him, that DR. PRIESTLEY had 
 read your answer to me before it was printed ; had 
 approved of it highly, and had strongly urged you 
 to publish it. I presume therefore that the fact to 
 which I allude was no secret, at least among the 
 Dissenting Clergy in London and its neighbour- 
 hood. The probity and veracity of MR. GORDON, 
 MR. LINDSAY, and Mr. PATERSON, cannot be 
 disputed ; but they cannot be known to every per- 
 son who may be interested in the fact to which I 
 allude : I must therefore beg of you to say, whether 
 my information with respect to it is correct or not. 
 Allow me next to give you one or two specimens 
 of those questions, with respect to points of fact, 
 which have occurred to me, on considering your 
 mode of stating and answering my argument; 
 which questions no person but yourself either is in- 
 titled, or can be required, to answer. In your 
 353d page, you have given as a quotation from 
 my Essay, and even marked the passage with in- 
 verted commas at the margin, the common and well- 
 known mark of precise and literal quotation, a cer- 
 tain passage of my Essay, (page 226.), which you 
 give in the following words. "But," says he, (DR. 
 Gregory), "if a guinea should be offered to him 
 (the porter] for carrying it (the letter) in the direc- 
 tion of A B, and half a guinea for carrying it in 
 the direction A C, and let him be assured, that if 
 he earn the guinea, he cannot earn the half guinea ; 
 
10 
 
 and that if lie earn the half guinea, he cannot earn 
 the guinea; will he go in the direction of A B 
 or A C, or remain at rest in A ?" 
 
 Now I would ask you precisely the following 
 questions. 
 
 1st, Is there in my Essay such a sentence as 
 you here profess to have quoted from ft ? 
 
 2dly, Is it not the following passage of my Es- 
 say, which you have so inaccurately and imper- 
 fectly quoted. " Let our porter be offered a gui- 
 nea a mile for carrying the letter in the direction 
 A B ; and at the same time, let him be offered half 
 a guinea a mile for carrying it in the direction A 
 C ; and let him be assured that if he earn the gui- 
 neas, he cannot earn the half guineas ; and that if 
 he earn the half guineas, he cannot earn the guineas" 
 
 The difference between the case as stated by me, 
 and as stated by you, with the irresistible implica- 
 tion that your way of stating it was precisely the 
 same with mine, is great, and I should think must 
 be obvious to every person : the difference certainly 
 must be obvious to every person who had read my 
 Essay, and knew the nature of the dilemma, and 
 the argumentum ad absurdum, which I employed 
 for the purpose of that demonstration, which I un- 
 dertook to give. But to you, more than to any 
 other person, I should have thought the difference 
 between your way and my way of stating the case 
 must have appeared obvious and striking. 
 
11 
 
 Your answer to that part of my argument is found- 
 ed on your own peculiarity in the mode of stating 
 the case in question : and the very angry schooling, 
 which you have the goodness to give me on that 
 occasion, relates to your own wqy of stating the 
 case, not to mine. Your words are these : " Now 
 if the Essayist" (meaning me) " understood how 
 to state a similar case with regard to motives, he 
 has, to say the least, expressed it very inaccurately. 
 He supposes that a guinea is offered for travelling 
 A B, and half a guinea for performing the journey 
 A C ; but has he told us that the distance A B is 
 double A C, and that to render the motives equal, 
 a double reward is offered ? No. The ca-se he pro- 
 poses is extremely vague and indejinite. A, B, for 
 aught he has said, may bear any proportion to 
 A C. If it were not double the distance (cateris 
 paribus), the motives could not be equal, and the 
 stronger impulse would overcome the weaker. 
 The case, I say, is inaccurately stated." 
 
 The case is indeed very inaccurately stated by 
 you, in your Essay : but I cannot be justly blamed 
 for that ; for in my Essay, 1 had stated it as clearly 
 and precisely as any proposition in Euclid is 
 stated. The purpose of that case, as stated by me, 
 and indeed the object of the whole deductio adab- 
 surdum in the first part of my demonstration, or 
 first horn of my dilemma, is merely to show that 
 motives are occasionally separated from their respec- 
 tive corresponding actions ; that is, are applied 
 
12 
 
 sometimes without having any effect in point of 
 overt action ; to which kind of effect alone, and not 
 to any real or supposed effects on the mind or the 
 body of the person to whom they were applied, 
 such as promptitude, alacrity, eagerness, joy, grief, 
 strength or weakness, redness or paleness, all my 
 reasonings related, and were expressly declared to re- 
 late. 
 
 To make the case which I stated easily and ef- 
 fectually certain for the purpose of that illustration, 
 I took care to state the application of two motives 
 which were neither equal, nor directly opposed, so 
 that it might be easy to foresee, or rather impossi- 
 ble not to foresee, that one of them would be com- 
 pletely separated from its corresponding action, and 
 even to know, without the help of experiment, 
 which of the two would be so. For my purpose in 
 stating that case, and in the whole of that part of 
 my dilemma, it is perfectly indifferent, whether the 
 one or the other motive be separated from its effect 
 in point of overt action : it is enough and it is ne- 
 cessary for my purpose, that one of them be so. 
 That kind of separation is directly contrary to what 
 happens when different physical causes of motion 
 are applied at the same time to a lifeless body ; or 
 even to a living person, when by any means he is 
 deprived of the power of moving himself, or of se- 
 parating either of the causes of motion applied to 
 him from its proper effect. That kind of separation 
 
13 
 
 is the proof which I wanted, that the relation of 
 motive and action is not a constant conjunction, as 
 that of cause and effect in physics seems to be. 
 
 Even you, in the midst of all your angry school- 
 ing of me, for my supposed ignorance, and inac- 
 curacy in stating the case in question, do not pre- 
 tend, nor can you pretend, that the result would 
 be in fact different from what I have stated. You 
 have only employed a different word and phrase to 
 express the same matter of fact ; which does not in 
 the least alter the nature of the thing expressed ; 
 nor is it any addition to human knowledge ; nor 
 will it even enable you, or any other Necessitarian, 
 to escape for a moment from my dilemma. The 
 fact to which I allude, and about which happily 
 we agree, you express in the following words, the 
 stronger impulse would overcome the weaker. This 
 is only substituting the phrase, being overcome by a 
 stronger motive, for my phrase, being separated from 
 its proper action. 
 
 Your phrase I should think much less proper 
 than mine ; because it would be not only metapho- 
 rical, but ambiguous ; being generally employed in 
 a different sense, which you cannot fail to know, 
 and which, not withstanding an essential difference, 
 bears a strong affinity to that sense, which, in the 
 passage quoted from your Essay, you wish to ex- 
 press by it ; and such a sense, or meaning, as na- 
 turally makes a part of any discussion concerning 
 
14 
 
 the difference between the relation of motive and 
 action, and that of cause and effect in physics. 
 
 In every instance of the production of motion in 
 this globe, the impulse, or cause of motion, is al- 
 ways opposed by at least one force, often by many 
 forces ; I mean, even exclusively of what is called 
 the vis inerticE of the body whose motion we con- 
 template. Every body projected through the air 
 is resisted by the air ; if it is projected upwards, it 
 meets with resistance to its motion, both from the 
 air and from its own gravitation to the earth : a 
 ship under sail is resisted by the water, a very 
 dense medium : and in an adverse current is re- 
 sisted both by that dense medium, and by the pre- 
 vious motion of it in an opposite direction : a solid 
 body dragged along the ground meets with strong 
 resistance from what is called friction : when ten 
 pounds weight are put into one scale of a balance, 
 and only nine pounds into the other, the greater 
 w r eight descends, though it meets with resistance 
 from the nine pounds in the opposite scale. Now, 
 in all these cases, we are accustomed to say, that 
 the greater force overcomes the weaker ; and the ex- 
 pression, though metaphorical, cannot be deemed 
 very improper, as it is well and generally under- 
 stood ; being explained by its common use ana uni- 
 form application : but the meaning of it in all those 
 cases is widely different from that in which you 
 wish to use it; for in all those cases the/brce that 
 
15 
 
 is overcome has its full effect in weakening or lessen* 
 ing the sensible change in those lifeless bodies, 
 which would have been produced by those strong- 
 er causes applied if they had not been opposed. 
 The corresponding effect or result in cases such as 
 that one stated by NEWTON, in his first Corollary 
 from the the three laws of motion, is still more per- 
 ceptible : and the case which I had stated, and 
 which you have so strangely mistaken, is of that 
 kind. 
 
 I 'admit however that your expression may be 
 made perfectly intelligible, by a proper definition, 
 and sufficient illustration by means of proper in- 
 stances. But if this were done, it would immedi- 
 ately be necessary to contrive another expression in- 
 stead of being overcome, and uniformly to employ 
 it, to denote that thing which happens to the weaker 
 of two opposite forces applied at the same time to a 
 lifeless body. You must no doubt be sensible of 
 the impropriety of employing, for the purposes of 
 strict reasoning, the same word or phrase to express 
 different meanings : but perhaps you are not aware, 
 though, if you will try the experiment, you will soon 
 be convinced, that such an impropriety leads to 
 confusion, absurdity, and nonsense, as certainly 
 as using only one word to denote equal, greater, 
 and less, would confound the best reasonings of 
 mathematicians. 
 
 The phrase constant conjunction was not new, or 
 
16 
 
 contrived by me ; nor am I the person who first m- 
 troduced and employed it in the controversy about 
 Liberty and Necessity. Before I was born, it was 
 introduced and employed in that controversy by 
 DAVID HUME : it had been familiar to Philoso- 
 phers, especially to Metaphysicians, but most of 
 all to Necessitarians, and must have been well un- 
 derstood by them all. The purpose for which MR. 
 HUME introduced it, and the important and truly 
 scientific use which he made of it, must have at- 
 tracted the attention of men of science, both to the 
 expression itself, and to the relation expressed by 
 it. His object was to point out the essential differ- 
 ence between that constant conjunction of certain 
 causes with their respective effects, which is a mat- 
 ter of familiar and uniform observation, and that 
 necessary connection which some Philosophers sup" 
 posed to exist between causes and their effects. 
 
 MR. HUME'S expression, already become fami- 
 liar in the controversy, seemed to me just as well 
 adapted, on the one hand, to express the difference, 
 which I perceived, between the uniform connec- 
 tion of physical causes with their effects, and the 
 occasional and separable connection of motives 
 with the voluntary actions of men ; as, on the other 
 hand, to express the difference between that con- 
 stant conjunction, and the supposed necessary connec- 
 tion of physical causes with their effects. Even Me- 
 taphysicians and Necessitarians, though they had 
 
17 
 
 not thought of tracing the necessary consequences 
 of the notion of the relation of constant conjunction 
 in every case, had done so, most accurately and 
 faithfully, in one case, and had admitted as a truth, 
 the reference to which in that case it necessarily leads. 
 You yourself do so, and probably would treat with 
 great contempt, both the understanding and vera- 
 city of any man of science, who should declare 
 bona fide, as I have done, that he did not believe 
 that inference. Yet that inference is a just one, 
 only on the supposition that the relation of constant 
 conjunction, in my sense of this phrase, and in that 
 sense, in which it is true in physics, really subsists 
 between motives and actions. 
 
 You will understand, that I allude to the case 
 of equal and opposite motives, like equal weights in 
 the opposite scales of a balance : and this was illus- 
 trated by the ludicrous supposition of an hungry ass 
 placed between two equal, similar, and equally dis- 
 tant bundles of hay. A very little reflection, I am 
 sure, must convince you, that the result in that 
 case could not be what you and all other Necessitari- 
 ans profess to believe ; unless each of the opposite 
 motives were constantly conjoined with its effect : for 
 whenever one of them was separated from its effect, 
 the other would have its full effect, as if it had been 
 unopposed. The agent, in such a case, would 
 have no occasion to discover, or to fancy, an addi- 
 tional motive on one side, to enable or to deter- 
 Let* B 
 
18 
 
 mine him to act: the mere separation of the oppo- 
 site great motive would imply the necessity of his 
 doing so. And, if the stronger of unequal opposite 
 motives were ever separated from its correspond- 
 ing* action, the weaker remaining conjoined with its 
 action, the latter would necessarily prevail. In such 
 cases, a motive would be overcome (to use your own 
 language) by an equal, or even by a weaker motive. 
 But such overcoming, you and 'all Necessitarians 
 must certainly hold to be absurd and impossible ' 
 therefore, you must understand^ least, and, on some 
 occasions, believe, that constant conjunction of motives 
 and actions, which forms the basis of my reasoning 
 in the fast part of my dilemma. 
 
 I employed without scruple MR. HUME'S expres- 
 sion, because it appeared to me as clear and pre- 
 cise, and as little metaphorical, as any that could 
 be used to express the same notion. But my 
 reasoning depends on the notion, not on the word. 
 You are heartily welcome (if you please) to pro- 
 scribe the phrase constant conjunction, and banish it 
 for ever from the writings and conversation of men 
 of science. If it will afford you any gratification 
 or comfort, I shall employ your own word over- 
 coming, instead of MR. HUME'S expression. My 
 dilemma w r ould remain as obvious, and as irrefrag- 
 able, as ever. The relation of motive and action 
 must either be such, that a motive never is over- 
 come; or such, that a motive sometimes is overcome. 
 My algebraic symbol ~, will express the relation 
 
19 
 
 of never being overcome, just as clearly and precisely, 
 as it did the same notion, when expressed by the 
 words constant conjunction : and just as well as 
 any algebraic symbol expresses the notion which 
 it is uniformly employed to denote. From that 
 notion there will result the same axioms, which 
 may be expressed in the same algebraic formula?, 
 that you have already seen. From each of those 
 axioms stated as the major, and a certain sup- 
 posable case put, stated as the minor proposition 
 of a syllogism, may be deduced certain inferences, 
 which must be universally true, if that notion of 
 never being overcome ( fEf ) be just. 
 
 If those several cases and inferences were stated 
 (as easily may be \done) in the most general and 
 abstract terms, as of certain principles of change, with- 
 out expressing whether these are physical causes or 
 motives, applied to a certain subject, it would afford 
 you and other Necessitarians a good opportunity 
 to judge, whether you really feel the force of the 
 reasoning that I employ, or whether you have 
 bonajide any reason for mistrusting it. If you say 
 the inferences me false, you might be invited to try 
 them experimentally with respect to physical causes, 
 applied to a lifeless body ; but you would instantly 
 perceive, without having occasion to try the expe- 
 riments, that all the inferences are true. If you say 
 the inferences are all true, as following fairly and 
 necessarily from a just principle, you might be in- 
 vited to try them experimentally, by the application 
 
20 
 
 of motives to a living person : but you would have 
 no occasion to try the experiments, you would per- 
 ceive intuitively that every one of them must be 
 false. 
 
 Would you then give up, as false with respect to 
 motives and actions, that notion =H, whence those 
 false inferences followed as necessary conse- 
 quences; which notion, as a principle, appeared to 
 be true with respect to physical causes and lifeless 
 bodies, for as much as all the necessary inferences from 
 it were found to be true with respect to them ? 
 
 Or, would you attempt to set aside, and escape 
 from, the plain dilemma, that the relation of motive 
 and action must either be that expressed by = , or 
 not that? 
 
 Allow me, in the next place, seriously to call 
 your attention to the following very remarkable 
 passage, which occurs in the same page of your 
 Essay, (p. 353. from line 15th to the end). It is in 
 these words : " But, as it must be acknowledged 
 " that the porter will not move in that direction, ex- 
 " perience proving the fact ; then it follows, that the 
 "law of physical causes, and that of motives, do not co- 
 " incide ; and that the relation between motives and 
 " actions is not necessary, as between physical causes 
 " and their effects." This passage you have made 
 the subject of many severe and angry animadver- 
 
21 
 
 sions, and even of reproaches tome. The justness 
 of your animadversions on that very foolish and 
 absurd passage, I shall not dispute : it seems to 
 me to approach so near to nonsense, as neither to 
 require animadversion, nor to admit of justification 
 or excuse. But you, who, from the pains that you 
 have bestowed on it, may be supposed to under- 
 stand it fully, are better qualified than I am, to 
 judge what degree of attention is due to it. I must 
 only beg leave to ask you precisely, for what reason, 
 and on what authority, you have imputed it to me? 
 You have printed that passage in your Essay, 
 marked with inverted commas at the margin, imply- 
 ing that it was not only an account, faithful in sub- 
 stance, of what I had said, but an exact literal tran- 
 script of the words which I had employed. Nay, 
 from the manner in which you have introduced it, 
 subjoined to the former quotation, or what you 
 chose to give as a quotation r from my .Essay, ending 
 with the words, Will he go in the direction A B, or 
 A C, or remain at rest in A ? and from the follow- 
 ing words of your own, with which you preface the 
 passage at present in question, " He (Dr. Gregory,) 
 " answers, that if the principle in which Necessity is 
 "founded be true, he must move in the diagonal 
 " A D, and can move in no other direction ;" every 
 reader would naturally suppose, that this (preten- 
 ded) answer of mine was given, and immediately 
 subjoined, to that question, which, by the bye, is 
 
22 
 
 nut the question that I put, but only a part of it. 
 However, as your mode of stating my question, 
 though imperfect, does no material injustice to my 
 meaning, it is unnecessary to put any questions to 
 you about it, or to make it the subject of any re- 
 marks. 
 
 I am certain that there is not in that section of 
 my Essay any such sentence, as that at present in 
 question, which you profess to have quoted from 
 it : I am certain that there is nothing like it in that 
 section of my Essay : I am certain that I can jind 
 no such sentence, or any thing like it, in the whole of 
 my Essay, from end to end : I am certain that there 
 are several clauses in that pretended quotation of 
 yours widely different from any thing that I ever 
 thought, or intended to express, and even incon- 
 sistent with the mode and the subject of reasoning, 
 in that part of my Essay, (the first horn of my di- 
 lemma ;) and indeed inconsistent with the tenor of 
 my reasoning in the whole of my Essay : I am cer- 
 tain that some of the expressions which you have 
 imputed to me, are such as I did not generally, if 
 ever, employ, being such as I studiously avoided, 
 because 1 thought them either ambiguous, or incon- 
 sistent with those distinctions, and that strict mode of 
 reasoning, and above all, that peculiar dilemma on 
 which my demonstration is founded. For example, 
 you represent me as having said, (that is, having an- 
 swered to my own question,) that if the principle 
 
23 
 
 in which Necessity is founded be true, he (the por- 
 ter) must move in the diagonal A D, &c. It is im- 
 possible that I ever should have thought such an 
 absurd thing ; and, I should think, almost impos- 
 sible that I should have deliberately written and 
 printed, and revised my composition, without dis- 
 covering such a glaring absurdity. It also ap- 
 pears to me nearly impossible, that I should not 
 now be able to find that passage, if it really is, in 
 my Essay. 
 
 The principle in which Necessity is founded, I 
 presume, means the want of self-governing power 
 in a living person ; but surely no such inference, 
 as that of the porter necessarily going in the dia- 
 gonal A D, in the case put, can be derived from 
 that principle. Perhaps you may say, that the 
 principle in which Necessity is founded means the 
 pretended axiom, that every thing, especially every 
 event , must have a cause: but surely the necessary 
 inference in question could not follow from this 
 principle, but quite the contrary, that the porter 
 could not move in the diagonal A D, for as much 
 as there was no cause for his moving in that direc- 
 tion, and as there were two very sufficient causes 
 for his moving in one or other of two different di- 
 rections, namely, A B and A C. 
 
 That inference, which you represent me as hav- 
 ing deduced, in the case put, from the principle 
 in which Necessity is founded, follows necessarily 
 
24 
 
 from the principle of constant conjunction, and from 
 no other that I am acquainted with. This notion 
 of constant conjunction is not even essential to the 
 doctrine of Necessity ; it was introduced into the 
 controversy by MR. HUME ; and the doctrine of 
 Necessity had long been maintained, and may still 
 be maintained, without any regard to the principle 
 of constant conjunction. The supposed voluntary ac- 
 tions of men may be supposed to be absolutely and 
 irresistibly determined by motives not constantly 
 conjoined with their respective actions, just as their 
 belief always is by evidence, many kinds of which 
 are not constantly conjoined with the Correspond- 
 ing belief, and yet completely preclude all self-gov- 
 erning power, or liberty, with respect to belief. 
 
 If you will take the trouble to look into my Es- 
 say, you will see that, from end to end of it, I have 
 taken care to distinguish uniformly between the 
 fundamental principle of Necessity, as already ex- 
 pressed, and the principle of constant conjunction. 
 That distinction was necessary for my dilemma. 
 In that part of my Essay to which your pretended 
 quotations relate, I trace purely the necessary con- 
 sequences of the principle of constant conjunction. 
 
 You represent me as having said, that the porter 
 will not move in that direction, (the diagonal,) ex- 
 perience proving the fact. I do not remember to 
 have said this, or any think like it. I never heard 
 or dreamed of the experiment having been tried. 
 
25 
 
 I do not believe it ever was tried, or ever will be 
 tried. I am sure there is no occasion to try it ; and 
 I declared that I would not try it ; and gave my 
 reasons for that resolution. 
 
 You represent me as saying, then it follows that 
 the law of physical causes, and that of motives do not 
 coincide, &c. Where have I said this ? I do not re- 
 member ever to have used such a phrase. 
 
 You represent me also as saying, " that it fol- 
 " lowed from the same fact, (the porter not going in 
 " the diagonal,) that the relation between motives 
 " and actions is not necessary, as between physical 
 "causes and their effects." Where have I said this, 
 or any thing like it ? I do not remember ever to 
 have entertained such a thought, or drawn such an 
 absurd inference from the premises that you have 
 expressed ; and I remember well to have expressed 
 in my Essay a very different sentiment with respect 
 to the necessity of either of those relations ; a kind 
 of doubt whether the human faculties were ade- 
 quate to such an investigation. I am sure, at least, 
 it has nothing to do with the question about the 
 Liberty or Necessity of the supposed voluntary ac- 
 tions of men. The relation of motive and action 
 may be supposed strictly necessary, like those of 
 quantity contemplated by mathematicians, and 
 neither proceeding from the wise institution of the 
 Supreme Being, nor changeable by his power ; and 
 yet we might have either perfect self-governing 
 
26 
 
 power, or various degrees of it': provided only the 
 relation of motive and action was not a constant 
 conjunction ; for this effectually precludes any self- 
 governing power. 
 
 On the other hand, the relation of cause and ef- 
 fect in physics, with respect either to lifeless bodies, 
 or with respect to a living intelligent person, to whom 
 such physical causes shall be applied, may be sup- 
 posed not necessary, like those of geometry, but 
 strictly contingent, depending on the wise but ar- 
 bitrary appointment of the Deity : and yet there 
 could be no self-governing power, either in a life- 
 less or a living body, with respect to the changes 
 proceeding from such physical causes applied to 
 them, provided only the conjunction of those 
 causes with their effects was constant. 
 
 All these distinctions I kept in view, and fre- 
 quently expressed in the composition of my Essay ; 
 as you must have observed when you read it. 
 
 You may now perceive what different sentiments 
 and assertions you have imputed to me, and what 
 gross injustice you have done me, in half a page of 
 your Remarks on my Essay ; and in a passage 
 which you gave as not only a faithful, but a literal 
 quotation from my work. Such a passage can do 
 no harm to me, or my argument ; but may do much 
 harm to you, and your cause, if you cannot, or will 
 not, justify, or at least excuse it. You may be as- 
 sured, even from my sending you these papers, 
 
27 
 
 that I do not wish to do you any injustice. I 
 should be sorry, without absolute necessity, to 
 charge you with having wilfully forged that absurd 
 passage, which you give as a quotation from my 
 Essay, and for which you revile me so unmerciful- 
 ly. But severe as that censure is, and disgraceful 
 to a man of science, you cannot escape it, unless 
 you point out in my Essay those expressions and 
 sentiments, which I honestly and seriously disclaim, 
 to the best of my knowledge, memory, and belief. 
 Next, I beg leave to call your attention to what 
 you have said of my argument in the latter part of 
 your 357th, and former part of \our 358th page. 
 " The Essayist's argument obviously involves the 
 absurd hypothesis, that all causes, of whatever kind 
 they are, and in whatever circumstances they ope- 
 rate, must produce the same effects; and that, be- 
 cause motives and physical causes both act necessa- 
 rily, and are in this respect similar, their effects, 
 in every instance, should be not only similar, but 
 even identic. I might as well believe, that gra- 
 vity should produce a volition, or that anger should 
 attract iron. I might as well assert, that because 
 the physical body describes A D in the same time 
 in which it would describe either A B or A C, the 
 letter-carrier, under the influence of two contend- 
 ing motives, should run from A to D in the same 
 space of time as he would take to travel from A to 
 C. If a person should contend, that because cold 
 
28 
 
 necessarily congeals water, and beat necessarily dis- 
 solves ice, cold, therefore, should dissolve the lat- 
 ter, or heat congeal the former, we should be apt to 
 charge him with insanity or idiotism. But ridi- 
 culous as such an argument would appear, it is 
 not more irrational than to suppose, that, because 
 all causes act necessarily, they must therefore pro- 
 duce the same effects, whatever the causes may be, 
 and in whatever circumstances they may operate." 
 You have not given any part of this strange ac- 
 count of my mode of reasoning in the form of a li- 
 teral quotation from my Essay, and therefore I 
 cannot require of you to point out any such sen- 
 tences, or particular assertions, in my work, as I 
 thought myself entitled to do, with respect to those 
 pretended quotations which you had marked with 
 inverted commas. With respect to the passage 
 at present under review, I conceive that you are 
 answerable only for the truth of the substance and 
 general tenor of what you have said of me and my 
 argument : and I earnestly request of you, to point 
 out in what part of my Essay, in which horn of 
 my dilemma, in what argument, or in what illus- 
 tration that I have employed, have you found such 
 absurdities, and such nonsense, 'as involved, or ta- 
 citly assumed. I solemnly declare, not only that I 
 never assumed, or thought of assuming, such an 
 absurd hypothesis as you have imputed to me ; and 
 that I can find nothing like it, on considering, with 
 
29 
 
 the most scrupulous attention, the whole of my ar- 
 gument ; but further, that the absurd hypothesis in 
 question, far from being involved in my argument, 
 appears to me absolutely inconsistent with every 
 part of it. 
 
 Your remarks in that page of your book, and 
 in several of the preceding and the following pages, 
 relate to the first part of my dilemma, which pro- 
 ceeds solely on the assumed principle (assumed in 
 order to be refuted by a deductio ad absurdum) of the 
 constant conjunction of motive and action ; of X 
 with A, Y with B, Z with C, according to my al- 
 gebraical notation. Nothing is either said, or ta- 
 citly assumed, about the acting necessarily, any more 
 than about gravity producing volition, or anger at- 
 tracting iron ; and as to any involved supposition, 
 that all causes, of whatever kind they are, must pro- 
 duce the same effects, I have not only assumed, but 
 strongly and clearly expressed, the contrary suppo- 
 sition ; namely, that every motive applied was con- 
 stantly followed by its own proper effect, both in 
 quantity and quality ; just as happens with respect 
 to physical causes of motion in mechanical philo- 
 sophy, and as Necessitarians profess to believe 
 with respect to all motives, singly applied, and also 
 with respect to equal opposite motives. That such 
 is the tenor of my mode of reasoning, my axioms 
 of constant conjunction, and every part of my ar- 
 gument and illustrations, will amply testify. Yon 
 
30 
 
 -will no where find me stating X as conjoined with 
 B, Y with C, or Z with A. 
 
 As little, I believe, will you find any thing like 
 that absurd hypothesis which you impute to me, 
 involved in the second part of my dilemma; in which 
 I consider fully, and rigorously, the necessary con- 
 sequences resulting from the supposition, that mo- 
 tives may sometimes be separated from their re- 
 spective actions ; but nothing is said or insinuated m 
 that part of my dilemma, any more than in theybr- 
 mer, of all causes having the same effects, or even of 
 any one cause ever having any other but its own 
 proper effects. To me it appears impossible for any 
 person to have reasoned as I did, who had assumed 
 the absurd hypothesis which you have so strongly 
 expressed. You have not gone too far in saying, 
 that you should be apt to charge a person with in- 
 sanity or idiotism, who should contend for such an 
 absurd supposition as you have specified. I ad- 
 mit that if I had assumed in my Essay that absurd 
 supposition, I ought to have been sent to Bedlam 
 near twenty years ago. Allow me now to ask you, 
 what you think should have been done with your- 
 self ten years ago, when you printed and published 
 a serious and very angry answer to the argument 
 of a man, which you yourself declare to be as ir- 
 rational as the ravings of a madman or an idiot ? 
 You may consider also what must be thought of 
 
31 
 
 you, if my wgument involves no such absurd hypo- 
 thesis, or raving, as you have specified. 
 
 In your 373d page, you reproach me, in very 
 strong terms, with inaccuracy of thinking, and con- 
 founding two things totally distinct ; the action it- 
 self, and the inclination or promptitude with which 
 it is done. Now, let me beg of you to point out 
 any one passage in my Essay, wherein / have con- 
 founded those two things ; which, as you very justly 
 observe, are totally distinct. Supposing, in the 
 first place, for the sake of argument, that it is pos- 
 sible to confound two such different things, which, 
 to the best of my judgment, it is not ; I conceive 
 that the very peculiar plan, and nature of my argu- 
 ment, must have made it impossible for me to do it. 
 You know that I confined my attention strictly to 
 the motives applied, and to the overt actions pro- 
 ceeding from them, and conceived not only to in- 
 dicate their kind, but to measure their degree or 
 force. The reason of this mode of proceeding on 
 my part, I avowed explicitly from the first ; namely, 
 that my conclusions, which I gave as false at least, 
 if not absurd, but withal as necessary consequen- 
 ces of those principles which I undertook to dis- 
 prove by a deductio ad absurdum, might be brought 
 to the test of open unequivocal experiment, if this 
 should be thought necessary. In the whole course 
 of my Essay, I kept steadily in mind the necessity 
 of avoiding all appeals to consciousness, having 
 
32 
 
 bad much more than enough of experience to con- 
 vince me, that among metaphysicians engaged in 
 this controversy, such appeals were not to be trust- 
 ed. I cannot find in my Essay any passage, in 
 which the degree of inclination, or promptitude, or 
 alacrity, with which an action is performed, is even 
 blended with the consideration of the overt action 
 performed, or considered as a part of that action. 
 This, I presume, is all that you meant by confound- 
 ing those totally distinct things ; for as to mistaking 
 the one of them for the other, which may be sup- 
 posed to be meant by confounding them, it is evi- 
 dently impossible. 
 
 Moreover I never undertook to prove that such 
 things as the degree of inclination or promptitude 
 with which an action is done are voluntary, or that 
 our self-governing power extends to them. It 
 was impossible that I should ever have made such 
 an attempt, for two excellent reasons \first, Because 
 such facts could not be ascertained without appeals 
 to consciousness, which I distrust and reject; secondly, 
 Because I never thought, nor do I now believe, that 
 those things are voluntary. I am well convinced 
 that they are altogether involuntary, in any sense 
 that I can conceive to be given to the words, in- 
 clination, promptitude, or alacrity, in this discussion. 
 
 As to inclination, and its various degrees, far 
 from considering them as parts of the voluntary 
 action to which they relate, I conceive them to be- 
 
33 
 
 long to the motive from which that action proceeds. 
 If a porter is offered a guinea for doing an easy 
 piece of work, which he would have done cheer- 
 fully for a shilling, I can have no doubt that he 
 will feel a much greater inclination to earn the guinea 
 than he would have done to earn the shilling ; ajid, 
 as he will certainly do the work required, he may 
 with great truth and propriety be said to do that 
 action with a greater inclination. 1 see no reason 
 to think that he has any power over his degree of 
 inclination, in such a case, any more than he would 
 have over the degree or intensity of hunger or 
 thirst, if he were kept one, or two, or three days, 
 without food or drink ; or than he would have over 
 his own feelings if he were put to the torture. 
 Those differences of inclination are just what I al- 
 ways meant by different degrees, intensity, or force 
 of motives ; nor can I conceive, - that any motive 
 should be reckoned stronger than another of the 
 same kind, unless it was attended with a stronger 
 inclination to do the action proposed. I presume 
 you mean nearly the same by promptitude and aid- 
 crity ; and not merely the quickness, or shortness 
 of time, in which an action is performed. But if 
 you had in view any such meaning by promptitude, 
 it ought to be set aside in this discussion, by stat- 
 ing the case, that the porter shall befin his action 
 at a particular time, either instantly, or at an hour 
 that is specified ; and that he shall do his work, fot 
 Let. C 
 
34 
 
 example, carrying the letter, at the rate of three or of 
 four miles an hour, or as fast as he can ; and neith- 
 er quicker nor slower, sooner nor later. 
 
 If you can find any passage in my Essay, in 
 which I have taken into consideration those things 
 which I ought not to have done, and represented 
 as part of the voluntary action, what was cither part 
 of the motive, or an involuntary effect of it, it will be 
 highly necessary that you point it out, not for my 
 sake, but for your own. As matters stand at pre- 
 sent, it appears that you reproach me bitterly, not 
 mly for what I have not done, and couldnoth&ve done, 
 but for what you yourself have done. The whole of 
 your discourse, from the middle of your 373d to the 
 beginning of your 379th page, is employed in a bold, 
 but I think a very unsuccessful attempt, to confound, 
 or, as you call it, to distinguish those things which 
 you reproach me for confounding. This you have 
 done particularly, in considering, and endeavor- 
 ing to answer, my argument with raspect to unequal 
 opposite motives : in that case, even youseem to admit, 
 what every body knows to be true, that the overt ac- 
 tion, about which alone I mean to reason, and which 
 alone I conceive to be both subject to the self- 
 governing power, and capable of being ascertained 
 by open experiment, is just the same as if no 
 weaker opposing motive had been applied ; but you 
 say, page 376, " If I am placed in a situation where 
 1 am prompted, by very cogent motives, to one 
 mode of action, and restrained by others nearly as 
 
35 
 
 strong, and inclining to a different mode of action, 
 I do not prefer the former to the latter, with the same 
 degree of alacrity, as I should do, if the opponent 
 motives were less strong : just as a scale descends 
 with greater momentum, when opposed by only one 
 pound, than when opposed by twenty. The cases 
 are exactly parallel, and clearly show the similar 
 operations of motives and physical causes." 
 
 Again, in page 378. " If a Necessitarian were to 
 affirm, that, though motives were opposed by 
 motives, yet the inclination to prefer the stronger is 
 as great as if they were unopposed, the Essayist's 
 argument would be just ; but this no Necessitarian 
 ever maintained . If ten guineas are offered a porter 
 for carrying a letter eastward, and nine for carrying 
 it westward the same distance, he will not prefer 
 the one road to the other, with that promptitude, 
 which he would discover, if ten had been promised 
 for travelling one way, and only one for the other. 
 But the motive of one guinea, other circumstances 
 being equal, will turn the scale, and produce the 
 preference. This distinction, however, between the 
 action itself', and the greater or less alacrity with 
 which it is preferred, seems to have escaped the 
 attention of the Essayist ; and hence, I apprehend, 
 his error has arisen." 
 
 Whether these observations and reasonings be 
 just or erroneous, it is certain at least, that they are 
 yours, and not mine. It is certain also, that what 
 
36 
 
 you call the distinction between the action itself, 
 and the greater or less alacrity with which it is pre- 
 ferred, which you say seems to have escaped my 
 attention, consists in referring the overt action to 
 the stronger of two opposite motives, and in refer- 
 ring to the weaker of the two, as its proper effect, 
 the diminution of the alacrity with which the action 
 was performed. 
 
 Supposing, for the sake of argument, that in such 
 cases of unequal opposite motives, there is a dimi- 
 nution of the alacrity, with which the action is per- 
 formed, it will not in the least affect my argument. 
 But I do not believe, either that there is any such 
 diminution of alacrity in the case stated, or that in 
 any case Necessitarians meant that kind of invisible 
 effect of motives ; but, on the contrary the evident 
 external effect in point of overt action, about which 
 alone I undertook to reason. You have seen in my 
 book very ample extracts from the writings of DR. 
 PRIESTLEY, which strongly express his sentiments 
 on the subject. See, if you please, my appendix, 
 page 554, 5, & 6. 
 
 In all these various cases, of motives variously 
 applied and modified, and of actions referred to, 
 and proceeding from them, the overt actions alone 
 are uniformly represented, as indicating the kind 
 and measuring the degree of the motives from which 
 they proceeded. The various modifications of 
 the overt actions in kind, in degree, in repetition, 
 
37 
 
 and in the case of equal and opposite motives, 
 suspension of all action, are represented as corre- 
 sponding to the different circumstances of the mo- 
 tives applied. Not one word is said about the 
 overt action being the same, but only the degrees of 
 inclination, promptitude, alacrity, and ardor, with 
 which it is performed, being greater or less, accor- 
 ding to the circumstances of the motives applied in 
 respect of force or of opposition. I scarce think it 
 possible that so important a consideration, or ra- 
 ther, according to the tenor of your discourse, one 
 quite familiar to all Necessitarians, should have es- 
 caped the attention of DR. PRIESTLEY, when he 
 was deliberately discussing and illustrating that part 
 of the doctrine of Necessity, to which it imme- 
 diately relates. DR. PRIESTLEY has not even in 
 that part of his treatise, or in any part of it that I 
 can discover, stated the case of unequal, opposite 
 motives, and attempted to reconcile the result in 
 such cases with the doctrine of constant conjunction, 
 by shewing that the effect of the stronger motive, 
 was the production of the overt action corresponding 
 to it ; and that the no less constant and certain effect 
 of the 'weaker motive, consisted in diminishing the 
 inclination, alacrity, and promptitude, with which the 
 overt action was performed. I think it is impossi- 
 ble that DR. PRIESTLEY should have omitted any 
 thing so obvious and important, on that occasion, 
 if he had ever thought of it. I am certain there is 
 
38 
 
 no such thing in the writings of MR. HUME: but 
 indeed, if it is not to he found in the writings of 
 DR. PRIESTLEY, one of the most reeent and ve- 
 hement assertors of the doctrine of Necessity, it is 
 not to be expected that it shall be found in the wri- 
 tings .of any of his predecessors. All this, however, 
 is to be understood with a salvo jure to YOU and 
 DR. PRIESTLEY, and all other Necessitarians : if 
 you can shew me in the writings of any of them, 
 prior to my Essay, such a proposition or argument, 
 or such a mode of illustrating their own doctrine, I 
 shall most explicitly and cheerfully acknowledge 
 my mistake ; but in the mean time, that is, till such 
 a passage is pointed out to me, I cannot help 
 thinking, that that argument, which you ha\e stated 
 so diffusely, and repeatedly, and with so many 
 bitter reproaches to me for being ignorant of it, 
 was suggested by my peculiar mode of reasoning ; and 
 that it is neither more nor less, than a feeble and 
 preposterous attempt to evade one part of my ar- 
 gumentum ad absurdum, by substituting, in some 
 cases, instead of the voluntary overt action, about 
 which alone I undertook to reason, some other ef- 
 fects^ real wpretended, of certain motives applied ; 
 which effects never were supposed to be voluntary, 
 and never can be made the subject Q^open, unequi- 
 vocal experiment. 
 
 Before I quit this point, of your pretended, invi- 
 sible, impalpable effects of the weaker motives m 
 
lessening promptitude, alacrity, &c. when they are 
 overcome by stronger motives, which produce the 
 same overt actions, which they would do, if they 
 were absolutely unopposed, I must beg leave to ex- 
 plain to you more fully what I have already hinted, 
 namely, that I did not believe the weaker motives, 
 in the cases put, have any such effect as you have 
 assigned to them : and at least to give you my rea- 
 son for distrusting what you have asserted so con- 
 fidently, and also to propose one or two questions 
 to you, concerning what you think should be the 
 necessary consequence of your doctrine in certain 
 supposable cases. 
 
 I am encouraged to attempt to explain to you 
 my reasons for distrusting what you assert so 
 strongly, of the weaker and overcome motives les- 
 sening the inclination, promptitude, &c. with which 
 the actions corresponding to the stronger motives 
 are performed, by observing that you yourself have 
 given me great and decisive aid in that respect, 
 though perhaps unknowingly, and certainly with- 
 out any intention of affording me such assistance. 
 
 In your 367th page, you have stated explicitly 
 certain cases of the application of motives, and 
 even of unequal and opposing motives, about the 
 result to be expected in which, both in point of 
 overt action, and also in point of promptitude, and 
 alacrity, eagerness, ardor, &c. there can be no dif- 
 ference of opinion between you and me,, nor da I 
 
40 
 
 believe that the keenest assertors of the liberty of 
 human actions will differ, even for a moment, from 
 the most strenuous assertors of the doctrine of Ne- 
 cessity, with respect to the result to be expected in 
 those cases. Now, when 1 agree with you as to 
 them, I think you may consider that as a pledge of 
 my sincerity and veracity, in those cases with re- 
 spect to which I differ from you : more especially, 
 as I can state to you, precisely and clearly, a strong 
 and essential difference in the different cases, to 
 which difference of principle, my difference of opi- 
 nion, with respect to the result of the several cases 
 in question, uniformly corresponds. You must at 
 least see the necessity, either of shewing, that there 
 is no such difference as I conceive in the principle 
 involved in those several cases, or else of explain- 
 ing, how it comes to pass, that principles so widely 
 different should equally imply, or lead to the same 
 consequences. The passage in your 367th page 
 is in the following words : " I may appeal to any 
 Libertarian, if, when unequal motives are opposed 
 to each other, he does not yield to the stronger 
 with greater or less promptitude, according to their 
 superiority ; and if he would not more cheerfully 
 will an action, by which he would gain rive pounds, 
 and lose a shilling, than one, cceteris paribus, by 
 which he might gain five pounds, and lose four, 
 though in both cases he might prefer the gain to 
 the loss, and act in obedience to the superior mo- 
 tives." 
 
41 
 
 Here you have stated explicitly the case of a 
 person prompted by a certain motive, implying 
 that he would gain five pounds and lose a shilling, 
 and that of a person prompted by a motive, to do 
 an action, by which he would gain five pounds and 
 lose four pounds : / had avoided stating any cases of 
 this kind, in my Essay, not because I had not thought 
 of them, for I had thought much of them ; and con- 
 ceived that in due time they might be usefully em- 
 ployed for the purposes of illustration ; but because 
 they were not necessary for my demonstrative reason- 
 ing, and because I did not see, how it was possible, 
 to bring the result in such cases to the test of open 
 unequivocal experiment : and you know I had en- 
 gaged, that the result of my reasonings, in my 
 deductio ad absurdum, should be either intuit- 
 ively absurd, and literally impossible, like those 
 in similar arguments employed by geometers, 
 or else should be such, that they might be 
 tried experimentally. There is no law, divine or 
 human, nor any impediment, physical or moral, 
 that I know of, to hinder a philosopher, who thinks 
 it necessary, or worth his while, to offer a porter 
 five pounds for going a hundred yards due west, 
 and either one shilling or four pounds, at the same 
 time, for going a hundred yards due east, and to 
 assure him, that if he earn the five pounds, he can- 
 not earn the shilling or the four pounds, and that 
 if he earn either of these smaller suras, he cannot 
 
earn the live pounds. Bui no philosopher is en- 
 titled to say to a porter, you shall have five pounds 
 for going a hundred yards due west; but if you do 
 so, or if you do not go a hundred yards due east, 
 you shall lose four pounds, or you shall lose one 
 shilling;, for I will take one or other of these sums 
 from you whether you will or not. It evidently is 
 not impossible to make such an experiment, but it 
 is hardly advisable to try it ; for it would certainly 
 be deemed criminal, and punishable, in the eye o* 
 the law, as approaching very near to theft or rob- 
 bery. However, as I clearly understand the cases 
 which you state, though I will not be concerned in 
 trying the experiments, I shall tell you frankly 
 what I think would be the result, in full confidence 
 that you, without the help of any experiment, will 
 agree with me perfectly, as to every one of them. 
 The porter assured of getting five pounds for go- 
 ing a hundred yards, and of losing only one shil- 
 ling, (no matter whether by theft, or robbery, or 
 philosophical magic,) would do the work proposed, 
 with great promptitude, alacrity, &c. understanding 
 that he would clear four pounds nineteen shillings 
 for a very easy piece of work. He would do the 
 same work (the overt action) for the five pounds? 
 even though he knew that he was to lose, or to be 
 robbed of four pounds, because he would under- 
 stand that he would clear twenty shillings very 
 easily. But I conceive that his promptitude and 
 
43 
 
 alacrity, or, what I should call his joy and cheer- 
 fulness, would be considerably less than in the 
 former case. On the same principle, and for the 
 same reasons, I conceive, that if he were offered 
 five pounds for doing the work, and assured that 
 four pounds nineteen shillings of that sum would 
 immediately be taken from him, he would do the 
 work, because he would earn a shilling, which is 
 fully adequate payment for the easy work required 
 of him ; but in this case I conceive, that his promp- 
 titude, alacrity, &c. would be much less than in 
 any of the two preceding ; but in all the three, the 
 overt action, the relation of which to its motive, 
 and the difference between that relation and the 
 relation of cause and effect in physics, was the 
 subject of my Essay, would b& precisely the same, 
 in kind and degree, and in all of them, the relation 
 of motive and action would be " that for the sake 
 of which." 
 
 Next, I shall state another case, on the same 
 principles : I shall suppose the porter offered five 
 pounds for going a hundred yards due west, and 
 at the same time assured, that if he does so, five 
 pounds shall be taken from him. In this case, I 
 take it for granted that he would not go one step, 
 and that he would not feel any promptitude, alacrity, 
 or inclination to do the work proposed to him. I 
 presume you will agree with me in this opinion, and 
 also in thinking, that in every case where equal mo- 
 
44 
 
 tives were in this manner opposed to one another, the 
 result would, bonajide, be, the want or suspension of 
 all visible overt action, as well as of all invisible 
 promptitude, alacrity, or inclination to it. 
 
 As this kind of opposite motives is very different in 
 its nature and result from that kind which has ge- 
 nerally been considered by Necessitarians, and il- 
 lustrated by the balance with weights, equal or un- 
 equal, in the opposite scales, and by the ass be- 
 tween two bundles of hay, it is proper to employ a 
 peculiar word or phrase to express it, and distin- 
 guish it uniformly from the other more common 
 kind of opposite motives. I shall therefore beg 
 leave to call the former counteracting motives, but, 
 with a salvo jure and express permission to YOU, 
 DR. PRIESTLEY, and others, to substitute for coun- 
 teracting any other word that you think better, and 
 which fully mark the distinction between them and 
 common opposite motives. 
 
 I presume you will see at once, as I think I do 
 very clearly, that in the case of equal counteracting 
 motives producing suspension of overt action, no 
 very minute or Imaginary additional motive, on one 
 side, will be sufficient to turn the balance, and pro- 
 duce overt action corresponding to one of the great 
 counteracting motives, which it has always been 
 pretended w r as found or supposed by the agents in 
 every case of equal opposite motives ; and that no- 
 thing less would turn the scale and produce the 
 
45 
 
 overt action, but such a motive as would hare done 
 so, if neither of the equal counteracting motives had x 
 been applied : in short, that the result, even in point 
 of overt action, would correspond to the visible ef- 
 fects of weights in the opposite scales of a balance, 
 considering only the turn of the balance, or what 
 you call the preponderance of one scale, and expressly 
 setting aside the degree or quantity of that turn or 
 preponderance. 
 
 Further, if you will take the trouble to consider 
 again those cases which I have stated in the 21st 
 section of my Essay, page 448 to 451, those cases 
 which you have treated with such outrageous re- 
 proach and contempt, and to suppose not opposite 
 but counteracting motives to be applied to the per- 
 sons who wished to sell a vote, a horse, or an estate; 
 I beg leave to ask you precisely, whether you do 
 or do not think that the result would be what I 
 have stated ? For example, If a man were offered 
 fifty pounds for his horse by one person, and instead 
 of being offered for the same beast fifty pounds by 
 another person, were assured that he would in- 
 stantly lose that fifty pounds ; do you believe that, 
 in such circumstances, he would part with his 
 horse ? If an additional shilling, or even a guinea 
 of purchase-money were offered him for his horse, 
 and still fifty pounds, but no more, was to be taken 
 from him, if he sold his horse ; do you think that 
 additional motive would make him part with his 
 
40 
 
 horse, or, in your own language, make that scale 
 preponderate? But if he were offered, in addition 
 to the fifty pounds originally offered as the price of 
 his horse, fifty pounds more, or such a sum, though 
 less than fifty pounds, suppose only forty, as he 
 thought a reasonable price for his horse, and still 
 was assured that he was to lose only fifty pounds, 
 when he was to receive ninety or a hundred 
 pounds ; do you not think, as I do, that, in those 
 circumstances he would part with his horse, and 
 take the price offered him, though he must lay his 
 account with having fifty pounds of it immediately 
 taken from him ? Do you not also think the corre- 
 sponding result would take place in similar circum- 
 stances, in the worthy burgess selling his vote, or 
 the great proprietor selling his landed estate ? 
 
 Such cases as these appear so absurd and ex- 
 travagant, that many persons will think it foolish to 
 consider them strictly and minutely : but as they 
 are simple and perspicuous, and afford a strong il- 
 lustration of the point in question, I am not asham- 
 ed to consider them fully. Nor in truth are they 
 so remote from the business of common life as at 
 first may be thought. There are many real similar 
 cases, of great importance in human affairs, in all- 
 which cases, the result, I believe, corresponds to 
 what I have stated in those most simple but ima- 
 ginary cases. 
 
 Though individuals cannot make such experi- 
 
47 
 
 ments on one another, they have often been made 
 on a great scale by sovereigns and legislators. 
 Many taxes, especially those belonging to the class 
 of excise and customs, are counter a 'ding motives ap- 
 plied to manufacturers and merchants. A tithe 
 strictly taken in kind, or a great increase of rent, or 
 other penalty for ploughing up a meadow, are coun- 
 teracting motives applied to farmers. The fear of the 
 gallows or pillory, the whipping-post or the gaol, 
 are counteracting motives applied, I hope not to 
 the majority, but to a most respectable minority of 
 mankind. If the excise or custom-house duty to 
 be paid on the manufacture or importation of any 
 commodity be equal, or more than equal to the 
 profit which the manufacturer or merchant ex- 
 pects to make by it, it is understood, and common- 
 ly said to amount to a prohibition ; and I believe 
 such very high duties have sometimes been impos- 
 ed instead of direct prohibitions, on certain articles : 
 smaller duties are only discouragements to certain 
 branches of manufactures and commerce, and, I 
 believe, have sometimes been imposed with that 
 view, as much as with a view to raise a revenue. 
 The tenth part of the produce of land, taken rigor- 
 ously-in kind, must always be a discouragement to 
 high cultivation, especially to tillage, and all ex- 
 pensive improvements ; and is, ipso facto ^ an encou- 
 ragement to convert arable into meadow ground. 
 Sometimes it is equivalent to a prohibition to plough 
 
48 
 
 up meadows or woodlands ; just as a high penalty 
 or triple rent would be. 
 
 Presuming that there can be no difference of opi- 
 nion between you and me as to the fact of what 
 would certainly be the result in all the cases, real or 
 imaginary, that I have stated, I shall tell you why 
 I think the result would be different in the corre- 
 sponding cases of opposite, but not counteracting mo- 
 tives. The difference, I conceive, is this : in the 
 case of counteracting motives, the person loses a 
 certain part, or, if they be equal, the whole of what 
 he got, or expected to get. In the case of opposite mo- 
 tives, he only does not get all that was offered him. 
 The difference between losing and not getting ap- 
 pears to me as great and obvious as that between 
 something and nothing, or as that between nothing 
 and a negative quantity. Getting, not getting, lo- 
 sing, correspond respectively to -(-, o, , in com- 
 mon algebraical notation. 
 
 On the principles of " that for the sake of which," 
 and of the self-governing power of man, getting, 
 opposed by losing, will produce, in all cases, such re- 
 sults as Necessitarians prof ess to expect from getting, 
 opposed only by not getting. I am sure at least, 
 that any person who should act differently from 
 what I here suppose would be thought, by all men 
 of sense, to act very foolishly ; for example, a mer- 
 chant, or a farmer, who should import a foreign 
 commodity, or plough up a meadow, knowing that 
 
49 
 
 he must pay in customs, or in penalty, a sum equal 
 to all the profit he could make by such importation 
 or ploughing. But I do not think his conduct 
 would be more foolish than that of a man who 
 should remain inactive when under the influence 
 of two great opposite motives, because he found 
 them exactly equal* Yet such conduct, in such 
 circumstances, YOU, and all Necessitarians, main- 
 tain to be unavoidable ; and though I know it to 
 be false and ridiculously absurd in point of fact, I 
 admitted, and have fully shewn it to be a neces- 
 sary consequence of the principle of constant 
 conjunction of motive and action, which prin- 
 ciple implies the irresistible force of motives, and 
 the total want of self-governing power in man. 
 
 On the same principle too, I mean the difference 
 between losing and only not getting, I have no 
 scruple to declare, that I do not believe that a per- 
 son would feel any diminution of his promptitude, 
 inclination, or alacrity, from a weaker opposite mo- 
 tive, as he certainly would do from a weaker coun- 
 teracting motive, when overcome by a stronger. 
 
 One question more on this point I beg leave to 
 propose to you : If a person were offered 1000 gui- 
 neas for turning to the right* and 999 guineas for 
 turning to the left, and assured that he could earn 
 only one of these sums ; you believe, as much as I 
 do, that he would turn to the right as certainly, and 
 as completely, as if only the offer of 1000 guineas 
 Let. D 
 
50 
 
 on that condition had been made to him : but you 
 hold farther, that he would do so with a diminu- 
 tion of his promptitude, &c. proportioned to the 999 
 guineas, which you say he would lose, and which 
 I think he would not get, because he did not turn 
 lo the left. Again, if he were offered 1001 guineas 
 for turning to the left, and only 1000, as before, for 
 turning to the right, we agree in thinking that he 
 would turn to the left ; but you think, and I do not 
 think, that he would do so with a diminution of 
 his promptitude, &c. proportioned to the loss, or 
 the not getting the 1000 guineas, which he was of- 
 fered for turning to the right. Now if those differ- 
 ent effects of the opposite motives applied, I mean 
 the production of overt action, and the production 
 of invisible promptitude, are commensurable, when 
 the opposite motives are so nearly equal as to differ 
 only by one thousandth part, why are they not 
 commensurable when they are exactly equal ? If 
 1000 guineas were offered to the person for turning 
 to the right, and the same sum for turning to the 
 left, why does he not turn either to the right or to 
 the left, but only with a diminution of his prompti- 
 tude, alacrity, &c. proportioned to the 1000 guin- 
 eas which he would lose, or not get, by not turning 
 to the other side ? By acting in this manner, each of 
 the opposite motives would have its full effect, 
 according to your own principles, only their effects 
 would be of very different kinds, and the man 
 
51 
 
 would get 1000 guineas to boot; while by remain- 
 ing inactive, according to your own doctrine, he 
 loses 2000 guineas, and I, and every body, must 
 admit, (hat he does not get one farthing. 
 
 Substitute in these cases, 1000, 999, 1001 gui- 
 neas, stated as counteracting motives, implying that 
 the person is to lose as much, or almost as much 
 as he will get, and there can be no doubt, that when 
 the counteracting motives are equal he will remain 
 inactive, and when they are unequal he will act, 
 but with a diminution of his inclination, alacrity, 
 and promptitude, corresponding to the greatness 
 of the sum that he is to lose, or the smallness of the 
 balance that will ultimately remain in his favor. 
 
 When you shall have stated what you conceive 
 to be the principle of the difference of result, in so 
 many cases, between opposite and counteracting mo- 
 tives, I trust you will perceive that these consider- 
 ations afford an additional proof of what I had 
 demonstrated in my 1 0th section, that there is not, 
 and cannot he, in motives, any such absolute strength 
 or force as Necessitarians have supposed, and have 
 been accustomed to explain and illustrate by the 
 pretended result from the opposition of equal mo- 
 tives, like equal weights in the opposite scales of a 
 balance. 
 
 In your 2d section, from page 368 to 379 of 
 your book, you endeavor to invalidate the reason- 
 ing which I had employed in my 10th section, in 
 
52 
 
 order to show that the doctrine of constant con- 
 junction of motive and action is absurd, as - being 
 inconsistent with itself. This I conceive I have 
 demonstrated completely, by shewing, that in the 
 case of equal opposite motives, to one of which is 
 added another small motive, the effect in point of 
 overt action (the only kind of effect about which 
 I reasoned) is just the same in kind and degree 
 that it would be if there were no opposite motives; 
 while, according to the doctrine of Necessity, espe- 
 cially on the principle of constant conjunction, the 
 result of the application of equal opposite motives 
 would be the suspension of all overt action. This 
 I conceive to be exactly equivalent to the absurdity 
 of maintaining, in common algebra, that X 1^=0; 
 but that X-\-^~ Y=X ; or, in common arithme- 
 tic, that if 10 be deducted from 10, there will 
 remain 0, but that if 10 be deducted from 11, there 
 will remain 11. The ablest mathematicians in 
 Scotland, and the most zealous Necessitarians of 
 my acquaintance, some of whom are good mathe- 
 maticians, can find no error in that short and sim- 
 ple demonstration by a deduct io ad absurdum: but 
 you attack it boldly, and without ceremony; trust- 
 ing, I presume, to your petitio principii, which will 
 not be granted you, that the circumstances of 
 promptitude,mclination, alacrity, &c. a re to be regard- 
 ed as part of the effect of the motive applied, and 
 are such things as I and other assertors of the 
 
53 
 
 liberty of human actions, maintain to be voluntary, 
 and depending on the self-governing power of man. 
 Once for all, be assured, that my belief is, that 
 those things are involuntary, and that my undertak- 
 ing has no more relation to them than it has to the 
 effects of appetites, passions, and desires on the 
 circulation of the blood, the secretion of bile, and 
 insensible perspiration. 
 
 Now, on this principle, setting aside all regard 
 to such invisible effects of the motives applied, and 
 every effect of them, except the performing or sus- 
 pending, increasing or lessening overt action; I ask 
 you precisely, Do you perceive any error in that 
 part of my mathematical reasoning ? 
 
 Not only from the general tenor of your very 
 angry discourse, almost from end to end of that 
 part of it which relates to my Essay, but more par- 
 ticularly from your precise expressions, and your 
 algebraic formula: in your 377th page, it is plain, 
 either that you do not understand my argument, or 
 that you wish to pervert and misrepresent it. Your 
 words are these: " Let X represent ten pounds in 
 " one scale, Y ten pounds in another scale: let A 
 " represent the preponderance of the scale in which 
 " X is placed, B that of the scale in which Fis pla- 
 " ced; then 
 
 x r-o 
 
54 
 
 " which is absurd; therefore the preponderance is 
 " impossible. Is this conclusion agreeable to fact? 
 " Will not the addition of one pound to either scale 
 " produce the depression of that scale, as certainly 
 " as if there were none in the other?" 
 
 Those algebraic equations you give as exactly 
 similar to mine, and the last of them yon give as 
 absurd, which I acknowledge it to be; and you 
 give a corollary for it, " therefore the preponderance 
 " is impossible." But to this corollary you subjoin 
 two important questions, implying, that that which 
 you have shewn to be absurd and impossible with 
 respect to the balance, is yet true in point of fact 
 with respect to the use of that instrument. Most 
 men, I believe, and certainly all who know what 
 mathematical reasoning is, would have been startled 
 at such a corollary, and at matters of fact which 
 were certain, although they were absurd and impos- 
 sible. Even you, I think, if, instead of scolding 
 and reviling me, you had attended strictly to the 
 different principles and modes of reasoning adopted 
 by you and me, must have perceived the errors of 
 your own reasoning: nay, I am confident that you 
 will yet do so, if you will attend to the following 
 precise questions, and endeavor to give me explicit 
 answers to them one by one. 
 
 1. Are you aware, that the principle assumed by 
 me in my 10th section, from page 243 to 248 of my 
 Essay, was assumed by me, believing it to be false, 
 
55 
 
 and meaning to disprove it, by shewing that it 
 implied, by necessary consequence, an inference 
 that was palpably absurd? 
 
 2. Is not the principle stated in your 377th page 
 assumed by you as true and certain, and familiarly 
 known, with respect to the balance? 
 
 3. Are you aware, that my first and second 
 equations are given by me as notoriously false in 
 point of fact, but withal as precise mathematical 
 expressions of the application of equal opposite 
 motives, and the result of such application, accor- 
 ding to the doctrine of Necessity? 
 
 4. Are not your 1st and 2d equations (in your 
 377th page) given zsfair and precise mathematical 
 expressions of the case of equal weights put into 
 the opposite scales of a balance? 
 
 5. Are you aware that my 3d equation (in my 
 246th page) is given as absurd and impossible, but 
 withal as a precise mathematical eKpression of the 
 result in point of overt action, according to the 
 doctrine of Necessity, when any the smallest addi- 
 tional or imaginary motive concurs with one of two 
 great opposite motives; which result, though absurd 
 and impossible on that principle, is yet true in 
 point of fact, implying, that that principle is false, 
 and that the result, which is true in point of fact, 
 proceeds from the contradictory principle? 
 
 6. What fact, with respect to the motion of a 
 balance, do you mean to express by your 3d equa- 
 
56 
 
 tion, which you certainly give as absurd and impos- 
 sible, and which must be false in point of fact, if 
 your 1st and 2d equations are true, which I firmly 
 believe they are? Do you know of any instance in 
 which the visible tangible state of a balance is the 
 same with unequal as with equal weights in the 
 opposite scales, or more particularly, in which the 
 balance remains even, with a great weight in one 
 scale, and a small weight in the other; for this is 
 the state of the balance expressed both by your 2d 
 equation, X JTizO^O; and also in your 3d equa- 
 
 Y 
 
 tion, X -^rrrOEiO? As your meaning is so 
 obscure, even when you employ precise algebraical 
 symbols, I hope you will not think me unreason- 
 able, when I beg of you to express in common lan- 
 guage, and also to illustrate by arithmetical num- 
 bers, the two cases of weights put into the opposite 
 scales of a balance, which you mean to express by 
 your 2d and 3d equations. 
 
 That wonderful 3d equation mentioned in your 
 377th page is not enumerated among your errata: 
 you will therefore no doubt consider it as great 
 presumption in me to suppose that it is a mere error 
 of inadvertency, conveying a meaning very different 
 from what you intended. Yet from the whole 
 tenor of your discourse, expressed in common lan- 
 guage, in that paragraph, and in the one immediate- 
 ly following it, and especially from your last inter- 
 rogation, " Will not the addition of one pound to 
 
57 
 
 " either scale produce the depression of that scale, 
 " as certainly as if there were none in the other?" 
 in which you supposed there were ten pounds, the 
 same weight as in the first scale, before it received 
 the addition of one pound, I strongly suspect that 
 
 Y 
 
 you meant your 3d equation to have stood, X ~ 
 = X:E A; but that you fell into this unlucky mis- 
 take, in consequence of your not understanding alge- 
 braical notation, or knowing the precision and 
 force of it. 1 am not entitled to obtrude upon you 
 this unfavorable supposition ; more especially as the 
 equation which I have presumed to suggest to you, 
 as what you intended, is just as absurd and impos- 
 sible, and what you probably will think of more 
 consequence, is just as false in point of fact, as your 
 own 3d equation. I know of no case, nor do I 
 believe that you know of any, in which the result, 
 on putting unequal weights into the opposite scales 
 of a common balance, corresponds to that absurd 
 equation. If you do, I beg you will specify it 
 That absurd equation expresses, with the utmost 
 precision, the result, in point of overt action, of 
 unequal opposite motives, according to the doctrine 
 of Necessity, and accordingly I have used it in my 
 246th page, to express that result, and thereby to 
 shew, that the doctrine of constant conjunction is 
 absurd and impossible, as being inconsistent with 
 itself. If the same equation corresponded to and 
 expressed the result in the parallel case of unequal 
 
weights in the opposite scales of a balance, it would 
 be a demonstration, that our notion of the nature 
 of a balance, and the influence of weights upon it, 
 is not only fundamentally wrong, but absurd and 
 impossible. But that equation does not express the 
 result of unequal weights in the opposite scales of a 
 
 balance. This result is denoted clearly and precise- 
 
 v s 
 
 ly by the rational expression, X ^~^ ^; it 
 
 being understood, that X^AY^B. In plain 
 English, a balance with 10 pounds in each scale 
 remains even; but if an additional pound is put into 
 one of the scales, that scale descends or preponde- 
 rates ; but it does not go down so fast, or so far, as 
 it would have done, if there had been 1 1 pounds in 
 the one scale, and nothing in the other; and the 
 difference between the descent of it in these two 
 cases (I mean its visible tangible motion, and at last 
 its permanent posture, corresponding to overt 
 action in persons) is equal to the full effect of the 
 1.0 pounds, as appears experimentally, on taking 
 out the 10 pounds from the one scale, leaving, of 
 course, nothing in it, and 1 1 pounds in the other. 
 
 I do not ask you, whether, in my Essay, I have 
 expressed clearly and strongly the difference be- 
 tween the mere turn of a balance, to which Neces- 
 sitarians, in availing themselves of that favorite an- 
 alogy, seem chiefly or solely to have attended, and 
 the full effect of the greater weight, which, to the 
 best of my knowledge and belief, they had always 
 
59 
 
 overlooked ; for that important difference is fully 
 stated in my 1 3th section, and the whole tenor of 
 my plan and mode of reasoning in my Essay, and 
 most chiefly my 2d axiom of constant conjunction, 
 (page 172,) X Y=:A B 9 must shew, that I nei- 
 ther did nor could overlook that difference. But I 
 must ask you seriously, whether you think I have 
 done any injustice to Necessitarians, in expressing 
 my belief that they had overlooked that difference. 
 I thought so with great confidence, because I did 
 not remember ever to have met with any remarks 
 on that point in any of their writings which I had 
 read, or in the conversation of any of them with 
 whom I am acquainted, and with whom I have 
 often argued on the subject of Necessity. Fur- 
 ther, of the many learned and ingenious men 
 who perused my Essay before it was published, 
 several of whom were keen assertors of the doc- 
 trine of Necessity, not one seemed ever to have 
 thought of that difference before, and some of them 
 told me explicitly, that the observation was new to 
 them, and, as they believed, in the controversy. 
 Moreover, DR. REID, when mentioning the danger 
 and imperfection of analogy in reasonings, and 
 giving, as an instance of it, the analogy between the 
 motion of the balance and the voluntary determin- 
 ations of men, acknowledges it to be very striking, 
 though not perfect, and yet does not specify that 
 fundamental and unequivocal difference between 
 
60 
 
 them which I have pointed out. That, I think, In* 
 certainly would have done, if he had ever heard 
 or thought of it ; as he did the difference between a 
 dead horse under the influence of different physical 
 causes of motion, and a living horse under the in- 
 fluence of different motives. It was that observa- 
 tion of DR. REID, with respect to the difference 
 between a living and a dead horse, in certain sup- 
 posable cases of motion, which suggested to me the 
 mode of reasoning that I have employed in my 
 Essay. Lastly, I think if any person, whether an 
 assertor of the Liberty or of the Necessity of hu- 
 man actions, had ever thought of that great differ- 
 ence between the motion of a balance and the volun- 
 tary actions of men, which precludes all appeals to 
 consciousness, and all arbitrary hypotheses, and ena- 
 bles us to bring the question to the test of mathe- 
 matical reasoning and open experiments, he must 
 have fallen into the same train of thought that I 
 have done, and must have given occasion, long ago, 
 to such remarks as yours. 
 
 Nevertheless, strong as these considerations are, 
 they do not absolutely preclude the supposition that 
 the difference in question had been known, and at- 
 tended to, at least by some Necessitarians. If YOU 
 know of any of them who have attended to it, I beg 
 you will inform me of their names ; and refer me 
 particularly to the passages of their writings in 
 which they have mentioned it. I am certainly 
 
61 
 
 bound, in honor and candor, to acknowledge 
 my mistake in that respect as soon as the evidence 
 of it shall be laid before me : and I shall be happy 
 to do justice to those authors \vhohave anticipated 
 me in that important observation. 
 
 From the ease and freedom with which you 
 avail yourself of that observation, which I had the 
 vanity to think originally my own, and from the 
 gross terms of contempt and reproach in which you 
 revile me for my supposed ignorance of those things* 
 which I had stated the most strongly and expli- 
 citly, it may be presumed that the observation in 
 question was quite familiar to you : while yet the 
 use you make of the term preponderance of one 
 scale, which means exactly the same with what I 
 have called the turn of a balance, without regard to 
 the degree or quantity of that turn, and still more 
 your limiting the effect of the weaker and overcome 
 motive, to the production of certain invisible im- 
 palpable changes, the overt action being the same, 
 both in kind and degree, that it would have been if 
 no such weaker opposing motive had been applied, 
 must make it doubtful, whether even YOU had ever 
 heard of the difference in question before my Es- 
 say was published, and whether YOU understood 
 that difference when you published your Remarks 
 on my Essay. But to suppose you, not content 
 with reviling me for what I had done, and for 
 what I had not done, but, worst of all, to have re- 
 
62 
 
 viled me for not having done what I have done 
 most fairly and completely, is so unfavorable to 
 you, that I cannot state it, even in my own vindi- 
 cation, without taking- this decisive precaution to 
 prevent the suspicion of my doing you any injustice. 
 
 In my next letter to you, I shall take the liberty 
 to put some questions to you concerning your prin- 
 ciples, or mode of reasoning, especially about the 
 very peculiar mode that YOU Have adopted, of re- 
 futing and answering an argumentum ad absurdum. 
 According to my old-fashioned notions of these 
 things, all that you have said in answer to my rea- 
 soning, far from shaking it in any respect, appears 
 to me to be a kind of acknowledgment (a most un- 
 gracious one, I confess,) of the validity of my de- 
 monstration : and certainly I consider it as a good 
 proof and illustration of many things which I had 
 said of the conduct of the Assertors of the Doc- 
 trine of Necessity, and of the mode of reasoning 
 which they had employed. 
 
 You will understand, that either a faithful ab- 
 stract, or, according to circumstances, a full copy 
 of this letter, and of any others that I may have 
 occasion to write to you on the same subject, will 
 be prefixed to my intended publication ; unless 
 your answers shall convince me that my opinions 
 and reasonings, with respect to your argument, 
 are erroneous. 
 
 If your answers shall convince me that I am 
 
63 
 
 mistaken on those points to which I allude, my in- 
 tended publication shall be suppressed, and you 
 shall receive from me an explicit acknowledgment, 
 that I think your argument just and conclusive, 
 and my own fallacious ; and you shall be heartily 
 welcome to make that acknowledgment of mine as 
 
 O 
 
 public as you please. Further, I shall acknowledge 
 your arguments to be valid, if they be not such as 
 I should wish you, or any other Necessitarian, to 
 publish against me and my argument, and such as 
 I should consider as good illustrations of what I 
 have advanced. For reasons too obvious to men- 
 tion, I do not engage, as I did ten years ago, to 
 publish myself those objections to my argument 
 which I do not think conclusive ; but I engage most 
 solemnly to publish, in your own words, any ob- 
 jection or argument of yours which I shall think 
 requires an answer, and to subjoin my answer to 
 it. Thus you may be assured, that no injustice can 
 be done to you, or your mode of reasoning. In the 
 mean time, you are heartily welcome to show this 
 letter, or any others that you may receive from me, 
 to your friends and brethren Necessitarians. 
 
 
REPLY 
 
 TO LETTER I. 
 
 SIR, 
 
 YOUR letter I have perused with all the 
 attention of which I am capable. This, indeed, is 
 a duty, which I owe both to you, and to myself. 
 In reply, it shall be my study, as it is my earnest 
 desire, to pass over nothing, which you have offer- 
 ed, in the form of argument, and to answer to 
 every charge which you have thought proper to al- 
 lege. It is not victory, but truth, for which I am 
 solicitous to contend. I deem it necessary, at the 
 same time, to observe, that the controversy between 
 you and me is not, whether the doctrine of Neces- 
 sity be true or false, but simply, whether your rea- 
 soning be conclusive. These, you must perceive, 
 are distinct questions. For though it must be ad- 
 mitted, if your argument be demonstrative, that 
 our hypothesis is false, it does not follow converse- 
 ly, that this hypothesis must be true, because your 
 reasoning is fallacious. There are many persons, 
 
65 
 
 you well know, who reject the doctrine of Neces- 
 sity, yet pronounce your argument to be so- 
 phistical. 
 
 You introduce your letter with observing, that 
 I have treated not only your arguments, but your- 
 self personally, with little ceremony ; and, fearful 
 lest I should misapprehend the effect, which this 
 alleged treatment produced on your sentiments 
 and feelings, you studiously inform me, that 
 this unceremonious attack has been to you highly 
 gratifying. This declaration does not surprise me. 
 " Feelings hurt !" said Sir Fretful Plagiary smarting 
 under the lash of sarcastic " critics, feelings hurt ! 
 " no, quite the contrary ; I like it above all things. 
 " Another person would be vexed at this ; I am 
 " diverted. Ha! ha! ha!" As long as vanity and 
 pride inhabit the human breast, the risus Sardonius 
 will be no uncommon affectation ; but this is a sub- 
 ject, which forms no part of our present discussion. 
 
 That I have strictly examined your demonstra- 
 tion, and with freedom expressed my sentiments re- 
 specting it, is true. Dissimulation is odious ; and 
 I could not disguise my opinion of its charac- 
 ter. I wrote, be assured, as my conviction dic- 
 tated ; and, after a lapse of twenty-five years, I 
 have seen no reason to alter that conviction. If I 
 was disgusted with the prolixity, and the multi- 
 tude of your farraginous illustrations, and derided 
 some of them as inapposite and whimsical, the 
 Let. E 
 
66 
 
 emotions, which I expressed, were the emotions 
 of Necessity. If occasionally I assailed your ar- 
 gument with ridicule, I was prompted to it by the 
 conviction, that ridicule is not unsuitable to its 
 character. Besides, permit me to remind yon, 
 that no controvertist ever treated the arguments 
 of his opponents, or his opponents themselves, 
 with less ceremony, than Dr. Gregory. Had you, 
 after gravely employing the armour of reason, 
 playfully assumed the shaft of ridicule, directing it 
 against our hypothesis only, or our mode of defend- 
 ing it, your conduct would have required neither 
 correction, nor apology. But you did not confine 
 yourself to ridicule you proceeded to reproach ; 
 and there can scarcely be named a species of indig- 
 nity, which you have not offered to our arguments, 
 nay even to our characters. 
 
 But, Sir, I must take the liberty to enquire, what 
 you mean by observing that I have treated your 
 arguments with little ceremony. Are we to un- 
 derstand, that arguments, urged with extreme con- 
 fidence, and proudly asserted to possess all the 
 cogency of Mathematical evidence, nay ob- 
 truded without even the semblance of civility, 
 either to the reasoning, or to the characters, of your 
 adversaries, are not to be assailed with every 
 weapon, that either the rational faculty, or even ri- 
 dicule itself can furnish ? Sound argument, Sir, in- 
 vites examination: it challenges discussion, and 
 
67 
 
 confidently bids defiance to every species of attack. 
 And shall a mathematical demonstration shrink 
 from this proof? Is there any ordeal too severe, for 
 it to undergo? Aristophanes might succeed, in 
 turning the wisdom of Socrates into ridicule, and 
 exposing him, as a sophist, to the derision of a 
 giddy and licentious rabble ; but the wisdom of 
 the philosopher, combined with the wit of the 
 dramatist, would have assailed in vain a proposi- 
 tion in Euclid. A mathematical demonstration 
 dreads no weapon, and fears no assault. Like the 
 stately oak, gathering strength from the stormy 
 blast, it stands firm against every attempt to sap 
 its foundation, or to weaken its force. 
 
 Merses profundo, pulchrior evenit ; 
 Luctere, multa proruet integrum 
 Cum laude victorem. Hon. 
 
 Besides, Sir, you will pardon me for observing, 
 that after you had written two volumes, with the 
 avowed intention of not merely detecting the errors 
 of Necessarians, but of" exposing themselves to re- 
 proach and ridicule," nay farther, " of convicting 
 them of falsehood, the means of proving which 
 charge," you modestly remark, " had never occur- 
 red to any person before you' after this declara- 
 tion of your intention to expose not only our argu- 
 ment, but ourselves, as fit subjects of derision, you 
 surely are not the person, who ought to complain, 
 if his opponents attempt to turn his arguments 
 into ridicule. 
 
68 
 
 Perhaps you may answer, that I have vilified 
 your demonstration and unwarrantably treated it 
 with derision and contempt. It is replied, that I 
 have no where characterized it by any epithet, or 
 appellation, the applicability of which I have not 
 previously evinced by reason, and argument. I 
 have pronounced it fallacious, inconclusive, and 
 absurd ; but not, I trust, without sufficient evi- 
 dence. 
 
 You add, that I have treated yourself with little 
 ceremony. Have I disputed your veracity ? Have 
 ] questioned your honour ? Have I even insinu- 
 ated, much less asserted, the charge, that you are 
 a hypocrite, professing to believe, what you do not 
 believe? You will not affirm it. Yet this imputa- 
 tion you have presumed to cast on some of the 
 best of men, and most enlightened philosophers, 
 of the present age Sir, I have reprehended your 
 insolence, 1 have censured your vanity ; and I have 
 condemned, with no unjust severity of language, 
 as 1 conceive, your very uncandid and illiberal 
 spirit. I have said also, that in this controversy, 
 you have betrayed superlative inaccuracy of 
 thought, and that you have exhibited the semblance 
 of mathematical precision associated with a bewil- 
 dered and clouded intellect. But, whatever stric- 
 tures I have offered on your Essay, I have no 
 where confounded the philosopher with the man, 
 nor the man with the controvertist Have you ob- 
 
served the same distinction ? You must, indeed, be 
 blindly partial to yourself, if you will answer in 
 the affirmative. 
 
 You complain, that I did not submit my Essay 
 to your perusal, before it was printed, and remind 
 me of your conduct, as furnishing an example, 
 which it became me to follow. 
 
 In answer to this complaint, I observe, that I 
 did .lot depart from any general usage, nor vio- 
 late any established practice. It has not, I believe, 
 been customary with controversial writers, to sub- 
 mit their manuscripts to the examination of their 
 opponents. This, at least, I may venture to assert, 
 that, if such procedure has been generally adopted, 
 it has, to my knowledge, been distinguished by 
 many reputable exceptions I must, besides, can- 
 didly tell you, that the necessity, or propriety, of 
 this communication never once occurred to me. 
 I was not aware, that previously to the publication 
 of any controversial work, such ceremonial was 
 either indispensable, or was expected : and hence 
 the solicitations of several friends, by whose judg- 
 ment I was guided, prompted me to publish the 
 Essay, as soon as it was finished. 
 
 In the plenitude of your candour and charity, 
 you are pleased to insinuate, that this neglect of 
 mine may have arisen from a " desire to steal an 
 apparent and temporary victory." The contro- 
 vertist, whose chief object is not the discovery of 
 
70 
 
 truth but the defeat of his adversary, is prone to 
 believe, that others are actuated by motives, simi- 
 lar to those, by which he is himself governed ; a 
 liberal mind, conscious of the purity of its own 
 motives, judges charitably of the conduct of others. 
 I felt, be assured, no desire to steal a temporary 
 and apparent triumph. My sole intention was to 
 expose the invalidity of your demonstration ; and 
 had I not believed, that I should overturn your ar- 
 gument, to the complete conviction of every com- 
 petent judge, I should never have attempted, or at 
 least should not have published, an answer to 
 your Essay. And I must take the liberty to add, 
 that my having demanded the performance of your 
 promise either to retract your opinion, or to publish 
 your reply, furnishes no great proof of a desire on 
 my part to steal a temporary and apparent tri- 
 umph. You will be pleased to observe, that it is 
 now twenty-five years, since my Essay was pub- 
 lished : that of this period ten years elapsed, before 
 you informed me of your intention to reply. You will 
 recollect, that in your letter dated 18th Oct. 1803 
 intimating this intention, you expressly told me, 
 that either I might expect to see your defence early 
 in the year ensuing, it being then nearly ready for the 
 press, or that you would retract your opinion, if my 
 letter should convince you of any error in your de- 
 monstration. You will recollect also, that, though 
 you gave me reason to believe, that you would either 
 
71 
 
 renounce your argument, or publish your de- 
 fence in the ensuing spring, you neither retracted 
 your opinion, nor published your answer ; and that 
 I waited patiently for five years, before I called 
 upon you for the fulfilment of your promise. The 
 more natural conclusion therefore is, that he, who 
 engages to demonstrate the futility of his oppon- 
 ent's arguments, and assures him, that his work is 
 nearly ready for the press, yet does not publish, 
 after a lapse of more than twenty years from the 
 commencement of the controversy, and fifteen 
 years after the promised reply is nearly finished, 
 entertains strong apprehensions of the weakness of 
 his own cause. 
 
 If it is not so, I am highly gratified to think 
 that, since a discordance of opinion exists between 
 us, respecting the main question, your wishes, in 
 reference to this minor point at least, appear to 
 have been perfectly consentaneous with my own. 
 For, if it was my intention to steal an apparent and 
 temporary victory, you have kindly promoted the 
 attainment of my object, by allowing me to remain 
 in the quiet possession of that victory, for more than 
 twenty-five years. But with some readers, per- 
 haps, it may become a question, whether you were 
 reluctant to interrupt my triumph by the publica- 
 tion of your answer, fourteen years ago nearly ready 
 for the press, or whether this my reply to your first 
 letter did not arrest your intention, by convincing 
 
72 
 
 you of the fallacy of your argument, though you want- 
 ed the candour and the magnanimity to acknow- 
 ledge it. If you entertained no doubts of the va- 
 lidity of your demonstration, the presumption is, 
 that, after having printed six Letters, and part of 
 a seventh, you would have proceeded to publish, 
 as you gave me reason to expect, and evinced the 
 fallacy of my pretended refutation. 
 
 But, while I repel with scorn the imputation, 
 whether directly or obliquely advanced, that I in- 
 tended to steal a temporary victory, and while I 
 offer these observations as explanatory of my con- 
 duct, and to evince the incredibility of your un- 
 generous charge, I mean not to flatter you with a 
 confession, that I would have acted otherwise, in 
 implicit conformity to your example. Were I in- 
 clined to resort to the authority of precedent, I 
 might plead the sanction of much higher names 
 than Dr. James Gregory's, in justification of that 
 procedure, which, without reflecting on the subject 
 jnyself, I was prompted by the counsel of others 
 to adopt. But I bow to no authority, but that of 
 Reason, and, at her command, am ready to ac- 
 knowledge, that, though neither criminality, nor dis- 
 honouiyis imputable to every author, who may not, 
 previous] y to publication, submit his manuscript to the 
 perusal of his opponent, and though I cannot charge 
 myself with the violation of any established rule 
 whatever, or with any motive, which I am ashamed 
 
73 
 
 to confess, yet I am ready to acknowledge, that 
 such communications between controversial writ- 
 ers on metaphysical subjects, especially, recom- 
 mend themselves by the most cogent arguments. 
 And, when I assure you, that, should I ever be 
 engaged in another controversy of a similar nature, 
 I would act in conformity to my present declara- 
 tion, I trust, you will be persuaded, that your sus- 
 picions are at once ungenerous and unjust. I can- 
 not yet dismiss them without some farther obser- 
 vations. 
 
 You say, " As you did not allow me to per- 
 " use your answer to my argument, before you 
 " published it, not withstand ing the many strong and 
 " obvious considerations, which might have induced 
 " you to do me that justice, I, though a zealous as- 
 " serterof the liberty of human actions, must sup- 
 " pose, that you had other motives, which you 
 " thought stronger for publishing your work, with- 
 " out allowing me to see it ; and you, as an Ortho- 
 " dox Necessitarian, must hold, that your motives 
 " for acting as you have done, were irresistibly 
 "strong, and that you could not bona jidt have 
 " acted otherwise. I can only guess at your mo- 
 " tives ; but you, no doubt, can state them with 
 " precision and certainty. If you have no valid 
 " objections, that is, no irresistible motives, 1 wish, 
 " you would mention, what they are. For the 
 " most obvious and natural supposition with re- 
 
74 
 
 " spect to them, is not the most favourable to you, 
 " namely, a strong felt consciousness, that, how- 
 " ever ingenious and plausible your arguments 
 " were, and however well suited to the taste, and 
 " knowledge, and understanding of those, whom 
 " you expected to have for readers and admirers, 
 " they could not stand the brunt of my rigorous 
 " mode of reasoning." Your rigorous mode of 
 reasoning!!! O vanity, vanity! How miserably 
 dost thou darken the perceptions of the human 
 mind, blinding the understanding, and too fre- 
 quently corrupting the heart ! 
 
 A person, addicted to sarcasm, might be tempt- 
 ed to reply, that my Essay, not being, like your 
 Mathematical Demonstrations, intended for sage 
 Philosophers and Mathematicians of this and all 
 future generations, but merely for the profanum 
 vulgus, the illiterate herd of common readers, was 
 wisely accommodated, both in diction and senti- 
 ment, to inferior capacities. But I will not say 
 this. I shall only remark, that this passage of 
 your letter betrays more of puerility, vanity, and 
 arrogance, than can be easily reconciled with dig- 
 nity of mind, vigor of intellect, or the liberal and 
 enlightened spirit of philosophy. I forbear to 
 name the feelings, which it excites ; I shall only 
 say, that they have no affinity to indignation. So 
 far in regard to the vanity and rudeness of this ex- 
 traordinary passage. I cannot however entirely 
 
75 
 
 dismiss it, without adverting to the pointed and 
 truly humourous, allusion to our respective princi- 
 ples, which, wirii your characteristic pleasantry, 
 you so ingeniously introduce. 
 
 You say, that, though a zealous asserter of liberty, 
 you must believe, that I had other motives, which 
 I thought stronger, for not allowing you to peruse 
 my manuscript. So then, in the present instance, 
 you are a Necessarian, and believe, that I was go- 
 verned by the motive, which appeared to me to be 
 the strongest. How does this accord with a self- 
 determining will ? You add, that I, as an Ortho- 
 dox Necessarian, must hold, that my motives were 
 irresistibly strong, and that I could not have acted 
 otherwise. I do hold this, and maintain, that my 
 will was necessarily governed by the previous cir- 
 cumstances ; and that my volition to act, as I did, 
 as necessarily resulted from these circumstances, 
 as a physical effect from a physical cause. 
 
 But, permit me to ask, with what consistency 
 can you, as a Libertarian, desire to know, what my 
 motives were ? Nay, with what shadow of consis- 
 tency can you ascribe my conduct to motives at 
 all? It is vain to urge, that Libertarians do not 
 deny the influence of motives. The doctrine of 
 Liberty completely discards them. You do, in- 
 deed, in words admit their influence ; but your hy- 
 pothesis virtually excludes their agency What 
 should we think of the philosopher, who should 
 
76 
 
 tell us, that it is very true, that weights in a bal- 
 ance, are necessary for the preponderation of this, 
 or of that scale, that the weights have an effect, 
 that he never meant to dispute this but that, after 
 all, it is the self- preponderating tongue of the ba- 
 lance, which determines, whether the greater, or 
 the less weight, shall sink ? Should we not be justi- 
 fied in asserting, that his doctrine involves a palpa- 
 ble contradiction a monstrous absurdity ? Is it 
 less absurd to tell us, that motives have influence 
 in producing this, or that, action, but that after all, 
 it is a self-determining will, which decides, what 
 the action shall be, whether the greater, or the 
 less motive shall prevail ? If motives have not a ne- 
 cessary effect, condescend to inform us explicitly, 
 what effect they do have. If the will determines 
 the action, and the will is not determined by the 
 motive or state of mind, it would be of essential 
 service, if you would inform us, what effect the 
 motive produces. I confess, I have no concep- 
 tion of any agency, but necessary agency, and 
 therefore necessary effect. I can no more com- 
 prehend the effect produced by motives with a 
 self-determining will, than I can conceive the ef- 
 fect of weights, with a self-determining tongue of a 
 balance. 
 
 By maintaining then, that the will determines 
 its own volitions, you completely dissolve the con- 
 nection between motive and action. The motive 
 
77 
 
 may indeed, urge to this, or to that, action ; but, as 
 the will possesses a paramount authority over all 
 motives, and the action results from its sovereign 
 determination, to it, and to it only, must the action 
 be referred. For, whether I felt the motive to act 
 as I did, or to act as I did not, to be the stronger 
 motive it would have availed nothing in the di- 
 rection of my conduct ; the will would have deter- 
 mined for itself either this, or that, procedure. The 
 result, therefore, would be no better criterion of the 
 motive then predominant, than the shadow on a 
 sun-dial is of the weight of the atmosphere. The 
 motives to the two different modes of acting might 
 have been present to my mind ; but consistently 
 with the doctrine of Liberty, they would have de- 
 termined my conduct, just as much as supplication 
 addressed to the raging sea, or counsel offered to 
 a deaf man. 
 
 In short, as a consistent Libertarian, instead of 
 enquiring into the motives of my conduct, you 
 should have proposed some pertinent questions, 
 respecting my will. And, if you had enquired, why 
 1 willed to act, as I did, you would, by the very 
 question, have betrayed the falsity of your own hy- 
 pothesis, by resolving the determinations of the will 
 into the influence of motives. And to such an inter- 
 rogatory the only answer, which could have been 
 returned, consistently with the doctrine of Liberty, 
 would have been " I willed it, because I willed it. v 
 For, if a reason, cause, or motive be admitted for the 
 
78 
 
 determinations of the will, the hypothesis of Liberty 
 falls to the ground. 
 
 I maintain, therefore, that any suppositions, 
 which you may form, whether favourable, or unfa- 
 vourable, respecting the motives, by which my con- 
 duct was governed, or my will determined, are ut- 
 terly irreconcileable with your hypothesis. 
 
 It is in vain to urge, that your argument admits 
 and presumes the influence of motives. All influ- 
 ence, all agency, whether physical or moral, must 
 be a definite and necessary agency. We either 
 will, according to motives, or we do not. If mo- 
 tives are the causes of our volitions, Necessity fol- 
 lows ; if they are not, we have a self- determining 
 will 
 
 You enquire whether Dr. Priestley approved 
 my Essay : and whether it be true, that he offered, 
 rather than it should not be printed, as I feared the 
 expence, to undertake the risque himself. With 
 peculiar candour and modesty you are pleased to 
 add, that a refusal on my part to answer these 
 questions will be construed by you, as a confirma- 
 tion of the report. 
 
 Sir, I should do injustice to my own feelings, as 
 well as betray unpardonable indifference to so 
 flagrant a violation of the courtesies of common 
 life, if I omitted to reprehend this culpable exam- 
 ple of licentious curiosity, and rude presumption. 
 
 May I be permitted to ask, whence originates 
 
70 
 
 your right to propose such questions, or what au- 
 thority do you possess for demanding an account 
 of any private communications between Dr. Priest- 
 ley and me ? Are they necessarily involved in the 
 subject of dispute? Or will an answer to these 
 queries serve in any manner to determine the con- 
 troversy ? Or am I bound by any law, human or 
 divine, to reply to such interrogations ? Certainly 
 not. But, Sir, I will answer these questions, and 
 answer them fully. 
 
 When your Essay was published, I read it with 
 attention. Disgusted with the vanity, the inso- 
 lence, and the illiberal spirit, which it displays, dis- 
 satisfied also with your argumentation as fallacious 
 and inconclusive, I conceived, that to answer it 
 would be neither a useless, nor an arduous task. 
 Previously, however, to my attempting this, I was 
 desirous to have the opinion of some competent 
 judge, concerning what I had already written on 
 the subject of Necessity, and which I did not, at 
 that time, intend for publication. Accordingly I 
 took the liberty to send the manuscript to Dr. 
 Priestley, requesting his candid opinion of its cha- 
 racter. He returned me the following answer. 
 Sir, 
 
 " I have looked into your manuscript, 
 " and am much pleased with it. You seem to be 
 " perfectly master of your subject, which I am 
 " often surprised to perceive very ingenious men 
 
80 
 
 " are not; and should be glad to see your work in 
 "print, But you must he apprised, that there is 
 " little to be gotten by such things as these, and 
 " therefore there is nothing to tempt a bookseller 
 " I should like to see, what you have to say to Dr. 
 " Gregory ; but think, you would do better to in- 
 " troduce it into the body of your work, rather than 
 " into the Notes. I am, 
 
 Sir, 
 
 Yours sincerely, 
 J. PRIESTLEY. 
 Clapton, 
 
 20th Sept. 1792. 
 
 P. S. " I shall be happy to see you at my house, 
 " when I will deliver the manuscript to you." 
 
 When I had finished my answer to your Essay, 
 I sent it to Dr. Priestley, from whom I received 
 the following letter. 
 Dear Sir, 
 
 " I have looked through your papers, 
 " and think you have treated the subject with 
 " great acuteness and perpsicuity. I am con- 
 " fident, it will be of great use, and establish your 
 " character as a Metaphysician with all competent 
 "judges. I therefore earnestly wish it may be 
 '' published, and soon. But the demand for works 
 " of this kind is so small, that I fear the risque will 
 " be considerable. 
 
 " If you will fix any time for calling on me, I 
 
81 
 
 " shall be happy to see you, and talk further on 
 " this subject." 
 
 I am, 
 Dear Sir, 
 
 Your's sincerely, 
 
 J. PRIESTLEY. 
 Clapton, 
 12th Nov. 1792. 
 
 A few days afterwards, I waited on Dr. Priest- 
 Uy, and conversed with him some time concerning 
 the risque to be encountered in such publications. 
 My finances at that time were not adequate to the 
 loss, which might possibly have been incurred 
 by publishing the work ; and this circumstance I 
 frankly communicated to the Doctor. His answer 
 was expressed in terms too flattering for me to re- 
 peat, and he signified his desire, rather than the 
 Essay should not be published, to undertake the 
 risque himself. To this very friendly offer I ob- 
 jected. He then asked, if I was acquainted with 
 any bookseller. On my replying in the negative, he 
 requested, that I would leave the matter in his 
 hands, informing me at the same time, that he would 
 endeavour to make the necessary arrangements 
 with Mr. Johnson. In this proposal I acquiesced. 
 The manuscript, accordingly was, in a day or two 
 afterwards, delivered to the bookseller, whether 
 by Dr. Priestley or myself, I now forget. Your 
 Let. F 
 
82 
 
 curiosity on this subject is, I should hope, now 
 amply gratified. 
 
 Before I proceed to examine your complaints 
 and charges, I will state the proposition, which 
 you undertake to prove, in your own words. 
 
 " There is in mind a certain independent self- 
 " governing power, which there is not in body ; in 
 " consequence of which there is a great difference 
 " between the relation of motive and action, and 
 " that of cause and effect in physics ; and by 
 " means of which, a person, in all common cases, 
 " may at his own discretion act either according 
 " to, or in opposition to, any motive, or combina- 
 " tion of motives applied to him ; while body, in 
 " all cases, irresistibly undergoes the change cor- 
 " responding to the cause, or combination of causes 
 " applied to it." 
 
 After enunciating your proposition, you observe, 
 that the relation of motive and action must be ei- 
 ther a constant conjunction, or only an occasional 
 conjunction. " If the relation," you say, " of mo- 
 " tive and action, and that of cause and effect in 
 " physics, be a constant conjunction, the most ob- 
 " vious general necessary consequences must be 
 " such as may be expressed accurately by the fol- 
 " lowing algebraic formula, or canons of univer- 
 " sal application." 
 
83 
 
 X+Y-A+B 
 XY-AB 
 X r Y=A F B * 
 
 It is here necessary to observe, that, if X denote 
 the mere physical agent, or the external motive 
 simply, as the examples which you adduce of the 
 porter, the burgess, and the land-proprietor, evi- 
 dently imply, your expression denotes a principle 
 not true, either in matter, or in mind. This will 
 be fully proved hereafter ; no physical agent, and 
 no external motive, being uniformly conjoined re- 
 spectively with one and the same result. If, on the 
 other hand, X denotes, not merely the physical 
 agent, but ail the circumstances, contributing to 
 the effect, not the external motive simply, but all 
 the circumstances antecedent to the volition, then 
 X^A is universally true both in matter, and in 
 mind : but your examples are wholly foreign to 
 the expression, and inapplicable to the principle, 
 
 1 The symbol == denotes the relation of constant conjunction, 
 which seems to take place between a cause and its effect in phy- 
 sics, and between a motive and its action, according to Hume's 
 doctrine of Necessity. The signs, -j -- ,f\ signify respectively 
 the concurrence, the direct opposition, and the combination of 
 two causes, or motives. 
 
84 
 
 which is here implied. Thus, in ipso limine, you 
 assume a principle, which is not true, if your exam- 
 ples are pertinent ; and if your assumption be ad- 
 mitted your examples are entirely foreign to the 
 assumption. This subject will be resumed here- 
 after. In the mean time, every reader, who is ca- 
 pable of distinguishing between the physical agent 
 simply, considered as a cause, and all the circum- 
 stances contributing to the effect, as collectively 
 the cause, and also between the external motive 
 simply, and all the circumstances antecedent to 
 the volition, cannot fail to perceive the fallacy, with 
 which you are here chargeable. " 
 
 In the prosecution of your argument, you have 
 oftener than once remarked, that you have care- 
 fully abstained from all appeals to consciousness. * 
 In dismissing such references, you judged rightly. 
 In expressing, however, my concurrence with you 
 in this mode of proceeding, I would not be under- 
 stood to mean, that Necessarians decline such an 
 appeal : on the contrary, they are confident, that 
 nothing, but strict attention to what passes in his 
 mind, previously to any volition, is wanting,, to 
 convince any enquirer, that whether he wills to 
 act, or to forbear, he cannot will without a motive. 
 
 1 Consciousness, as you have correctly explained it, means 
 strictly the knowlege of what passes within us. It sometimes 
 however, denotes the faculty, by which this knowlege is ob- 
 tained. It is consciousness and memory which furnish the evi- 
 
85 
 
 But while the contending parties represent consci- 
 ousness, as delivering contradictory reports, all 
 appeals to her authority are evasive and nugatory. 
 I now proceed to examine your complaints of 
 misrepresentation, and injustice. With complaints 
 of this kind every person, acquainted with your 
 controversial productions must be sufficiently fa- 
 miliar. They are exhibited so often, that it would 
 excite no surprise, if they were treated with neglect, 
 not to say, derision, like the repeated complaint 
 of Horace's vagrant, or of the deceitful harlot, al- 
 ways lamenting the loss of her garter. You have 
 charged the learned gentleman, whose objections 
 
 dence, on which another very important power of the human 
 mind pronounces her decisions, I mean, the power of conscience. 
 This faculty has been named the moral sense ; and its office has, 
 in my apprehension, been entirely misunderstood by several 
 eminent philosophers. It has been represented as that power, 
 which distinguishes between virtue and vice. Were this the 
 place for such a discussion, it would be easy to shew, that this 
 opinion is not only unphilosophical, but dangerous, as well as 
 utterly irreconcileable with known facts. Reason distinguishes 
 between virtue and vice, as between truth and falsehood : and 
 in the discrimination of each the intellectual process is much 
 the same. The faculty of conscience possesses a judicial, (if I 
 may be allowed the metaphor) rather than a legislative author- 
 ity, approving our conduct, when we do, what we believe to be 
 right, and disapproving, when we act in a manner contrary to 
 our convictions of duty. 
 
 Nee natura potest justo secernere iniquum, 
 Dividit ut bona diversis, fugienda petcndis. HOK. 
 
86 
 
 to your argument are published in your Appendix, 
 you have charged him, at one time, with an un- 
 candid objection, and insinuation (which objection, 
 however, it would appear, two of your learned 
 friends approved) at another time, you accuse 
 him of wilful perversion of language then again 
 of intentional injustice to your argument then 
 again of wilful and deliberate misrepresentation of 
 your mode of reasoning. In your Censorian Let- 
 ter, you ofharged five of your medical colleagues, 
 with chicanery deceit falsehood, and other unhal- 
 lowed arts ; and this charge you alleged, as the 
 Royal College of Physicians remark, in terms 
 " rude, harsh, and offensive." You accuse an emi- 
 nent physician and professor, of misquotation, 
 and the substitution of other language for your own, 
 imputing to him " deliberate falsehood, and deter- 
 " mined knavery." You charge the members of the 
 Medical College with dissimulation. You assert, 
 that one and all of them had been guilty of a so- 
 lemn and deliberate violation of truth, imputing to 
 them the most flagrant, gross, and foul injustice to- 
 wards you. And these charges you advance, as 
 is remarked by the College, " in coarse, rude, and 
 " even sometimes grossly indecent language," com- 
 paring their conduct to that of " thorough-paced 
 " rogues, swearing off their companions at the Old 
 " Bailey." But the refutation of these charges by 
 that learned and respectable body was complete ; 
 
87 
 
 pointed and forcible was their retort. * After such 
 examples of your controversial habits, it will not 
 excite the reader's surprise, if I am included in 
 somewhat similar condemnation. The wonder 
 would be, if I were permitted to escape. 
 
 You complain, that I have done injustice to 
 your argument as expressed in pp. 225, 226, of 
 your Essay ; and that the " angry schooling" 
 which you represent yourself as having received, 
 relates to my peculiar mode of stating the case, 
 and not to yours. If I have done injustice to 
 your argument, it is certainly not that species of 
 injustice, which betrays any desire to steal an ap- 
 parent and temporary victory. I have extenuated 
 the error. According to my statement, you were 
 chargeable with supposing a case merely vague, 
 and indefinite ; whereas, according to your state- 
 ment, you are chargeable with a supposition, ut- 
 terly irreconcileable with your own argument, and 
 repugnant to the principles of the very corollary, 
 which constitutes the basis of your pretended de- 
 monstration. This is an, error of greater magni- 
 
 1 Sec " A narrative of the conduct of Dr. James Gregory to- 
 " wards the Royal College of Physicians of Edinburgh." The 
 insidious arts, which are there exposed, with facts of a much 
 graver name, it is neither my duty, nor my inclination to detail. 
 How far they are reconcileable with boasted sentiments of high 
 honour, and with lofty pretensions to uprightness, candour, 
 and liberality of conduct, a perusal of the narrative will enable 
 the reader to decide. 
 
38 
 
 tude, than mere want of precision. To the truth 
 of Newton's Corollary it is essential, that the two 
 distances > when the forces act separately, shall be 
 described in equal times. To such cases only is 
 the Corollary applicable. Of the times you have 
 said nothing ; you have left them undetermined. 
 I am aware, that, in some cases, they may be infer- 
 red ; and that therefore there is no necessity for 
 expressing them. The same body acted upon by 
 equal impulses, will, cateris paribus, necessarily 
 describe equal distances, in equal times : but you 
 have supposed the motives, or impulses equal, and 
 the distances unequal : for, according to your sup- 
 position, one and the same individual is impelled 
 to travel a mile in the direction A B by the motive 
 of a guinea ; and the same distance, in the direc- 
 tion A C, by the motive of half a guinea. 
 
 A B 
 
 C D 
 
 Your argument proceeds thus. If a principle of 
 constant conjunction exist between motives and 
 
89 
 
 actions, as between physical causes and effects, the 
 porter must either remain at rest at the point A, in 
 which case, two motives are separated from their 
 proper actions ; or if he take either of the two sides 
 A B or A C, one or other, of the two motives is se- 
 parated from its proper action ; he must therefore 
 take the diagonal. This is your argument. You 
 represent also our hypothesis to be such, that the 
 strength, as well as the kind of " the motives, or 
 " causes, of human actions may be as easily dis- 
 " covered, and as fairly measured, by the actions 
 " proceeding from them, as heat may be, by the ex- 
 " pansion of quick-silver." This you say, is our 
 hypothesis, the absurdity of which it is your pro- 
 fessed intention to demonstrate. Now, if the 
 strength of the motive is to be inferred from the 
 action, and conversely, as in physical causes and 
 effects, the one bearing to the other such propor- 
 tion, as to render them fit subjects of mathemati- 
 cal demonstration, and to admit the application 
 of Newton's Corollary, it must, I conceive, be evi- 
 dent to every intelligent reader, that you have sup- 
 posed a case, irreconcileable with your own pre- 
 mises, and to which Newton's Corollary is mani- 
 festly inapplicable. For, if the times must be 
 equal, as the corollary requires, then the distances 
 being equal, the forces must also be equal. But 
 by your supposition the impulses are unequal. If, 
 on the other hand, the equal distances, with un- 
 
90 
 
 equal forces necessarily imply unequal times, 
 Newton's Corollary is evidentl y inapplicable. Thus 
 it is manifest, that the case, which you suppose, 
 implies, that unequal impulses can make a body 
 describe equal distances in equal times ; or it ex- 
 cludes a principle, essential to the truth of Newton's 
 Corollary, namely, the equality of the times. 
 
 You will answer, I am aware, that your sole ob- 
 ject was to shew, that the porter would travel 
 somewhere between A B and A C, without profess- 
 ing to specify either the time, or the velocity, or 
 the precise direction. It is granted ; and I laid no 
 stress on the want of precision, with which your 
 supposition, as stated by me, is chargeable. But, 
 when you supposed a case in motives, as analo- 
 gous to one in physical causes, it was incumbent 
 on you to state one, precisely parallel : and that a 
 case more consistent with analogy might have been 
 stated, it requires but little penetration to perceive. 
 
 That my objection, however, to your supposed 
 case may not be misconceived, it may be neces- 
 sary to add, that I do not mean to deny, as a mat- 
 ter of fact, that a porter may be offered a guinea a 
 mile for travelling South, and half a guinea a mile, 
 for travelling Eastward. But I do mean to 
 affirm, that you, in stating such a case, have vio- 
 lated your own assumed premises, or precluded 
 the applicability of Newton's Corollary. Consist- 
 
91 
 
 ently with your representation of our hypothesis, 
 and the nature of your argument, it is as absurd to 
 suppose that two unequal motives, addressed to 
 one and the same individual, can produce, cceteris 
 paribus, the same result, as that two unequal phy- 
 sical causes, operating on the same subject, in the 
 same circumstances, can produce one and the same 
 effect. But let us dismiss this objection, and pro- 
 ceed to the argument. I pronounce it to be falla- 
 cious on the three following grounds. 1st. The 
 two cases, to which you refer as analogous, are to- 
 tally dissimilar. You suppose, that there are two 
 physical forces acting on the physical body, under 
 the combined operation of which, it describes the 
 diagonal ; and there is evidently only one motive, 
 one stimulating power, acting on the mind. Here 
 there is no analogy. You indeed inform us, that a 
 guinea is offered to him, if he travel Eastward, and 
 half a guinea if he travel Southward ; but you ad- 
 mit, at the same time, that only one of these mo- 
 tives can act ; for you acknowledge that the por- 
 ter sees, if he gain the one, he must forego the 
 other. It is obvious, therefore, that only one of 
 these motives can operate ; and consequently the 
 cases, which you state, are not analogous. In the 
 case of the physical body, the two forces are com- 
 bined ; in the case of the porter, by your own ad- 
 mission, the two motives are uncombinable. And 
 by what law a body acted upon by one force is to 
 
describe the diagonal of your parallelogram, I 
 must leave it to you to explain. Newton's Corol- 
 lary therefore is inapplicable. 
 
 In the second place, the moving or impelling 
 power acts, in the one instance on brute matter, 
 and is itself material : in the other, the motive is a 
 good presented to the contemplation of the porter, 
 and acts on an intelligent and sentient being. 
 Here again is a total dissimilarity. And, permit 
 me to ask, if the principle of constant conjunction 
 requires, that two causes, so different in their na- 
 ture, and operating on substances, wholly dissi- 
 milar, shall produce one and the same effect ? The 
 philosophical world has indeed been visited with 
 many absurd and paradoxical theories ; but no hy- 
 pothesis, no system, of which I ever either heard 
 or read, is so extravagantly false, as would be 
 this supposition. The cases, which you state as 
 similar, are as different as mind and matter, and 
 yet you argue, that, if the principle of constant con- 
 junction obtain in both, or the will be under the 
 government of fixed laws, the effects must be iden- 
 tical. In what system of philosophy this doctrine 
 is to be found, I have yet to learn. 
 
 Again your argument is inconsistent with it- 
 self. You suppose motives to be addressed to a 
 being capable, of reasoning, and foreseeing the con- 
 sequences of his conduct, for you represent him, 
 as perceiving, that he cannot possibly earn both 
 
93 
 
 rewards ; and yet to the truth of your conclusion 
 it is essential, that he have neither feelings, nor 
 passions, nor judgment, nor reason, in short, 
 that he should be a piece of inanimate matter. 
 Here there is a manifest inconsistency. Your in- 
 ference can be true, only on the supposition, that 
 your premises are false. If we maintained, that 
 motive and physical cause are one and the same, 
 that an intelligent being, and brute matter, are 
 one and the same, that an action and a physical 
 effect are one and the same, and that because 
 there subsists the same relation between motive 
 and action, as between a physical cause and its 
 effect, the results, or the consequents, of motive 
 and of physical cause, must therefore be identical, 
 your argument might then be admitted to be per- 
 tinent. But positions so false, as well as so ridi- 
 culous, neither make any part of our hypothesis, 
 nor do they belong to it, as legitimate deductions. 
 We believe, that actions result from motives, as 
 physical effects from physical causes. We believe, 
 that the same constant connection subsists between 
 a motive addressed to mind in a certain state, and 
 the consequent action, as between a physical cause, 
 operating in given circumstances, and the effect 
 produced. But we do not maintain, that, because 
 the connection is in both cases, necessary, the re- 
 sults are identical. Yet your argument proceeds 
 on the supposition, that agreeably to the doctrine 
 
94 
 
 of constant conjunction, necessity of operation 
 must imply identity of result. 
 
 In respect to the " angry schooling" of which 
 you complain, permit me to observe, that this 
 schooling, or whatever else you may term it, is 
 with greater justice required by your statement, 
 than by my representation of it. But, be not 
 offended, if I take the liberty to ask, what is 
 this angry schooling, of which you complain ? 
 The reader perhaps may anticipate some- 
 thing very wrathful and acrimonious. But he 
 needs not be alarmed. I have simply told you, 
 that you are chargeable with inaccuracy, and that 
 the case, which you propose, is very vague and in- 
 definite. This, it must be owned, is very rigid dis- 
 cipline ; this is extreme and unpardonable severity. 
 But to return. I will now suppose the case to 
 have been correctly stated ; your premises are still 
 radically vicious, and your argument sophistical. 
 Your object is to prove the falsity of our hype- 
 thesis by a deductio ad absurdum, that is, by shew- 
 ing, that its truth necessarily involves consequences 
 either false or absurd. Now, Sir, to the ac- 
 curacy of this, as well as to every other species of 
 argument, it is essentially necessary, that the pro- 
 position to be disproved shall be correctly and 
 precisely stated; and if the subject be of a moral, 
 or physical nature, that all the circumstances es- 
 sential to the point in question, be distinctly un- 
 
95 
 
 derstood, and fully exhibited. Any error here vi- 
 ciates the whole argument. Inattentive to these 
 important considerations, the controvertist often 
 subverts his own theory, or destroys what is merely 
 the product of his own fancy, while he flatters 
 himself, he overturns the hypothesis of his oppo- 
 nent. It is necessary also, that the principles and 
 demonstrations of one art or science be not incon- 
 siderately transferred to another, to which they are 
 wholly incongruous. Of this absurdity we have many 
 curious and ridiculous instances in the writings of 
 the schoolmen Misled by whimsical analogies, 
 and forgetting that things disparate cannot be 
 measured by a common standard, they employed 
 mathematical demonstrations, and physical facts 
 for the determination of moral and theological 
 controversies. Nothing can be conceived more 
 truly absurd Were a person now gravely to at- 
 tempt to prove, that the attraction of a purse of 
 gold, as exciting desire, is directly proportioned to 
 the quantity of gold, and inversely as the square of 
 the distance, he would deservedly become a sub- 
 ject of derision. And yet aningenious man, like Dr. 
 Gregory, might institute a very learned argument to 
 establish this proposition. He might begin perhaps 
 with telling us, (no matter whether to the point or 
 not) that the celebrated Kepler discovered, that 
 the attractions and motions of the heavenly bodies 
 are regulated by this law, that the squares of the 
 
96 
 
 times are proportioned to the cubes of the mean 
 distances. Then he might favour us with a long 
 quotation from Newton's Principia, and inform us, 
 that this great and immortal philosopher proved 
 that attraction is directly, as the quantity of matter, 
 and inversely as the square of the distance Then 
 by the help of a diagram and some algebraic for- 
 mulae of his own invention, he might demons- 
 trate, that, as a purse of gold is a physical body, 
 or rather an accumulation of physical bodies, and 
 man also a physical body, they are subject to the 
 grand law of attraction; and that this attraction, 
 operating on the eye of a miser, must necessarily 
 be proportioned directly to the quantity of gold, 
 and inversely as the square of its distance from 
 the eye, that, if the quantity be double any given 
 sum, the attraction, or excitement of desire must 
 be double ; and if the distance be half any given 
 distance, the attraction must be four times as great. 
 And perhaps he might go on to demonstrate, (for it 
 is impossible to say, what such a man might not 
 demonstrate) that, if there were two purses, one due 
 East, and the other due North, either of which he 
 might easily get, and if the doctrine of attraction, 
 and the combination of forces be true, (which, in 
 this case, would be the same with the doctrine of 
 Necessity) he would move with mathematical pre- 
 cision in the diagonal, and take neither All this, 
 I say, a man of Dr. Gregory's ingenuity might 
 
97 
 
 easily prove. Nay for aught I know (for wbat is 
 there, which genius will not accomplish ?) a person 
 profoundly skilled in Algebraic analysis, and an 
 adept at its application, might be able to furnish a 
 theorem, founded in the laws of centripetal and 
 centrifugal forces, by which might be mathemati- 
 cally ascertained the quantum of love, which Tom 
 Thumb, who, you are pleased to say, is the proto- 
 type of a true Necessarian in love matters, bore to 
 his mistress But I must return to the subject 
 more immediately before us ; and proceed to state 
 my objections to your demonstration. 
 
 On examining your argument with attention, 
 every reader of common discernment must per- 
 ceive, that it either presumes man to be nothing 
 else, than brute matter ; or, if it acknowledges him 
 to possess intelligence, it excludes the necessary 
 operation of that intelligence, implying a principle, 
 which philosophy disclaims, namely, that dissi- 
 milar agents, acting necessarily on dissimilar sub- 
 jects, must produce identical effects. New- 
 ton's Corollary, you well know, is applicable to 
 physical substances only; nor can it be applied 
 to man, unless on the supposition, that he is di- 
 vested of rationality, and incapable of foresight^ 
 that he is reduced to a mere physical substance, 
 and acted on by physical causes. Such your ar- 
 gument presumes man to be. Now, it is granted, 
 that, if the porter were mere inanimate matter, or 
 Let. G 
 
98 
 
 were under the operation of two physical powers, 
 nolens volens, he must describe the diagonal. But 
 is this the character, or this the condition of man ? 
 Or does our doctrine represent him, as such ? Does 
 not the hypothesis of Necessity consider man, as 
 a sentient, and intelligent being ? Does it not re- 
 solve his actions into the influence of motives 
 
 
 into his immediate perceptions of good and evil ? 
 Does it not maintain, that he cannot act without 
 a motive, and that his volitions are determined by 
 the predominant motive ? To suppose then, or to 
 attempt to prove, that, if our hypothesis be true, 
 the porter must take the diagonal, without any 
 motive whatever, is an egregious misconception of 
 the doctrine of Necessity. It is to suppose, that 
 man, according to our theory, is merely a piece of 
 brute matter, under no law, but that of physical 
 force. When a Necessarian asserts, either directly, 
 or indirectly, that man can act without a motive, 
 or that he is a being purely physical, or when you 
 can prove, that, if he is a necessary agent, he must 
 be a being purely physical, and therefore subject to 
 none, but physical laws, then indeed, but not be- 
 fore, will your argument be admitted to be a legi- 
 timate attempt at reductio ad absurdum. 
 
 If you admit, that man is a sentient and intelli- 
 gent being, your argument proceeds on the unphi- 
 losophical assumption, that dissimilar agents, act- 
 ing necessarily on dissimilar subjects, must pro- 
 
99 
 
 dnce one and the same effect. This assumption 
 you disclaim, but your reasoning presumes it ; for 
 it proceeds on the supposition, that if the two mo- 
 tives act necessarily on the mind of the porter, a 
 being possessed of reason and reflection, they 
 must, like two physical forces, acting on a physical 
 substance, impel him in the diagonal, in consis- 
 tence with the principle of Constant Conjunction. 
 Can any two substances be more different than 
 mind and matter ? any two agents be more unlike 
 to each other, than human perceptions, passions, 
 or appetites, and impelling physical forces ? Yet 
 from the effect of the latter, you reason to an iden- 
 tity of effect in the former, if they act necessarily. 
 
 It may be contended perhaps, that to admit, that 
 the porter will not travel in the diagonal, and to 
 assign intelligence as the cause, is, in truth, to ac- 
 knowlege a fact, inconsistent with our theory, and 
 at the same time to explain the cause, why the 
 porter is a free, and not a necessary agent. 
 
 It is answered. So far is the fact here admitted, 
 from being inconsistent with the truth of our hy- 
 pothesis, or the doctrine of Constant Conjunction, 
 that its contrary, namely the description of the 
 diagonal, would be utterly irreconcileable with 
 both. For we maintain, that, as no physical body 
 can move in this, or that, direction without a 
 cause, so no intelligent being can act in this, or 
 that way, without a motive. To travel in the dia- 
 
100 
 
 gonal there exists no motive, but there are cogent 
 reasons for restraining him from taking that 
 course. If our doctrine implied, as your argument 
 falsely presumes, that there exists no difference be- 
 tween brute matter, and an intelligent being, be- 
 tween motives addressed to mind, and forces 
 acting on body, then indeed your argument would 
 be conclusive ; and if the porter did not travel in 
 the diagonal, the fact would demonstrate our the- 
 ory to be false. But we distinguish between mat- 
 ter and mind, we distinguish also between their 
 effects ; we affirm, however, that in each the effects 
 are necessary. We acknowlege, therefore, the 
 fact, that the porter, not being purely a physical 
 subject, nor acted upon by purely physical causes, 
 will not take the diagonal, but we deny the admis- 
 sion to be inconsistent with the truth of our theory, 
 or the doctrine of Constant Conjunction. We ac- 
 knowlege your argument applicable, and your 
 conclusion just in physics ; but we affirm it to be 
 utterly inapplicable to mind. Our hypothesis, 
 therefore, leads to no falsity, unless on the unphi- 
 losophical presumption, that analogous agents, act- 
 ing on substances mutually dissimilar, must pro- 
 duce identical effects. Nor is it inconsistent with 
 the doctrine of Constant Conjunction, unless we 
 absurdly assume, that, because two physical causes 
 combine their operation, two motives must com- 
 bine theirs also, and that the theory of mind is de- 
 ducible from the theory of matter. 
 
101 
 
 Again We assign intelligence as the cause, 
 why the porter does not describe the diagonal ; but 
 we contend, that the effect of this intelligence is 
 definite, and necessary. Disprove this position, 
 and your argument is demonstrative. 
 
 We believe, that the convictions of the rational 
 faculty, or our judgments (to speak generally) are 
 not under our control, but are the necessary effect 
 of evidence. We believe also, that every man 
 pursues happiness, and shuns misery. This we 
 consider to be a law of our nature. No person 
 will choose pain, in preference to pleasure, unless 
 to escape from a greater evil, or to attain a higher, 
 than the present, good. Our views of good and 
 evil may be imperfect, and fallacious, our senti- 
 ments irrational, and our desires may be either im- 
 mediately, or ultimately injurious to our real inter- 
 est; but, while we believe (and that belief is a ne- 
 cessary effect) that any mode of conduct, or any 
 action, is on the whole, best, that action, that con- 
 duct, by a law of our nature we must pursue. 
 
 But it sometimes happens, that a controvertist in 
 the too eager pursuit of victory, does not clearly 
 perceive the necessary consequences of his own 
 reasoning ; and is not aware, that, while he is la- 
 bouring, as he flatters himself, successfully, to 
 overturn the theory of his opponent, he is only 
 furnishing an argument for the subversion of esta- 
 blished truths, or some favourite opinions of his 
 
102 
 
 own. In illustration of this fact, I will take the li- 
 berty to apply your reductio ad abmrdum to a pa- 
 rallel case. 
 
 It is impossible to foresee what paradoxes may 
 be started, or what standard truths in the rage for 
 speculation, may not be controverted ; but it has 
 never yet been denied by any intelligent man, 
 that the judgments of the human understanding 
 are the necessary result of evidence, that we have 
 no control over our convictions, and that we 
 must believe, or disbelieve, according to the evi- 
 dence before us. Now, let us suppose a question, 
 in which only probable evidence can be obtained, 
 and that the arguments on one side are either 
 double in number, or have double the strength of 
 those on the other. Will it be contended, that our 
 conviction is not necessary, because we do not 
 adopt the middle opinion? Yet this is a case pre- 
 cisely parallel. Let us take an example ; and with 
 your permission, I will employ your own dia- 
 gram. Of the numberless instances which might 
 serve for illustration, I shall adopt a case, which 
 immediately suggests itself, and which has been 
 among Theologians, a subject of considerable con- 
 troversy, I shall suppose the question to be whe- 
 ther Jephthah did, or did not, sacrifice his daughter. 
 Let the arguments in favour of the affirmative be, in 
 number four, and of the negative two, and these 
 singly of equal strength Let the former be repre- 
 
103 
 
 sented by A B, and the 
 latter by A C. Will it 
 be said that, if our judg- 
 ments necessarily re- 
 sult from evidence, the 
 person, to whom the 
 arguments are address- 
 ed, must take a sort of 
 middle opinion, between 
 the two, represented by 
 A D This cannot be : 
 
 D 
 
 B 
 
 a middle opinion is impossible He must believe, 
 either that Jephthah did, or that he did not, sacri- 
 fice his daughter. There is no medium. And, be- 
 cause he does not, nay cannot adopt the middle opi- 
 nion, in like manner as a physical body, acted on 
 by two contending forces, would describe the dia- 
 gonal, does it hence follow, that our judgments 
 are not the necessary effect of evidence? You your- 
 self will not affirm so unphilosophical a position : 
 yet your reductio ad absurdum goes to prove the 
 affirmative. Or does it follow, that a principle of 
 Constant Conjunction does not exist between evi- 
 dence and belief? Does it follow, that the same ar- 
 gument, addressed to the same state of mind, 
 dos not uniformly produce the same mental 
 
104 
 
 effect ? The similarity of this case to that of the 
 porter is too obvious to require illustration. 
 
 That there are cases, in which a middle opinion 
 is possible and probable, I am far from disputing : 
 and these cases resemble those, in which the in- 
 fluence of the opposite motives may be so combined, 
 as to produce an effect, which partakes of their 
 united influence. But in such cases, as that which 
 has now been supposed, the application of the ar- 
 gument demonstrates its fallacy. 
 
 I contend, therefore, that your reductio ad ab- 
 surdum is a mere sophism that, if applied to the 
 determinations of the rational faculty in all cases 
 of moral evidence, it would subvert an incontest- 
 able truth, namely, that belief is the necessary ef- 
 fect of evidence, and therefore, that by proving too 
 much,itinfactproves nothing. I affirm, that, though 
 the porter does not describe the diagonal, it is as ab- 
 surd to deny the necessary operation of motives, as 
 to dispute the necessary effect of arguments, be- 
 cause in the case now stated of contrary evidence, 
 the enquirer does not adopt a middle opinion. 
 Your argument, I repeat, is founded in error. It 
 proceeds on the indirect assumptions, 1st. That 
 motives and physical causes must produce, if they 
 act necessarily, an identical effect. And 2d. That 
 there is no difference between an intelligent agent, 
 and brute matter between a living philosopher, 
 (to use your, and Dr. Reid's, illustration) and a 
 
105 
 
 dead horse. Or, 3dly. If it admits this intelligence, 
 it involves the erroneous presumption, that, if mat- 
 ter and mind be each governed by definite laws, 
 analogous causes must, in each, produce identical 
 effects. 
 
 I am aware that you will disclaim these mon- 
 strous assumptions. You will tell me, that you 
 have even been at pains to disavow these egregi- 
 ous errors. You will tell me, that, on more than 
 one occasion, you have directed the attention of 
 your readers to the essential and striking differ- 
 ence, between a living, and a dead man. All this 
 is granted : but it may still be true, that you are 
 chargeable with these errors. You are not the 
 only controvertist, who has constructed an argu- 
 ment, which radically involved an opinion, which 
 he expressly disclaimed. You admit the distinc- 
 tion between a living philosopher and a dead man ; 
 and yet you argue, that, if the doctrine of Neces- 
 sity be true, that is, if each of these be governed by 
 fixed and definite laws, the effects of motives 
 on the one, and of physical forces on the other, 
 must be precisely identical, according to the prin- 
 ciple of Constant Conjunction. You say, that, 
 consistently with this principle, the porter must 
 describe the diagonal, like a human carcase, or a 
 block of wood, impelled or drawn by two contend- 
 ing forces. This, I conceive, is to confound mind 
 with matter. It is to confound identity of effect 
 
10(3 
 
 with necessity of operation. You forget, that it is 
 an axiom in physics, that the effect depends on 
 the previous circumstances, and that the addition 
 or abstraction of a new circumstance, or a new 
 agent, or that any change in the subject itself 
 must necessarily alter the effect also. Two con- 
 tending forces, acting in the direction of right an- 
 gles to each other, will make an inanimate being 
 describe your diagonal ; but, if we suppose this 
 being to be inspired with life, and to be endowed 
 with reason, sense, memory and imagination, and 
 that, instead of forces being applied to his body, 
 two opponent motives are addressed to his mind, 
 are we to expect, notwithstanding this change 
 both in the agents and in the subject, that the same 
 effect is still to be produced ? And if the same effect 
 is not produced, are we therefore to deny the 
 necessary relation, between the previous circum- 
 stances and the consequent effect ? Such conclu- 
 sion would be warranted by no system of philoso- 
 phy, with which I am acquainted. Necessity of 
 operation by no means implies identity of result. 
 
 " Be it so ;" you may reply, " it matters not to 
 "my argument. If he does not move in the dia- 
 " gonal, he must take one, or other, of the two 
 " sides ; and whichsoever he may take, it is clear, 
 " that one of the two motives is separated from its 
 " proper action, which is contrary to the principle 
 " of Constant Conjunction." 
 
107 
 
 This is your next argument. Now a Necessarian 
 contends, that the porter will obey the stronger 
 motive, and that, other circumstances being equal, 
 he will prefer the guineas to the half guineas, and 
 take the direction A B. You infer, therefore, that 
 our doctrine is false, because the motive prompt- 
 ing him to move in the line A C is separated from 
 its proper action. Here it is evident, you reason 
 from a false principle ; your argument involves a radi- 
 cal and palpable error. Permit me to ask, what you 
 mean by "a motive separated from its proper ac- 
 tion ;" for the expression seems to imply, that a 
 motive can be associated with only one action, 
 properly resulting from it. Now, as Necessarians, 
 we protest against such a doctrine, as unphiloso- 
 phical and false; while we censure the phrase- 
 ology as incorrect, and superlatively improper. 
 We affirm, that every effect must have a cause, and 
 every action a motive. But we deny, that a phy- 
 sical cause, considered simply as the agent, and 
 opposed to the subject or thing acted upon, has 
 any proper effect, or has one and the same effect 
 uniformly and constantly resulting from it ; as we 
 deny, that any motive, considered merely, as 
 something external, and distinct from the mind to 
 which it is presented, has any action, which can be 
 called proper to it, or exclusively connected with it. 
 That a cause, if by this term be implied all the 
 actual circumstances, that is, not only all those be- 
 
108 
 
 longing to the agent, but also those belonging- to 
 the subject, must uniformly produce one and the 
 same effect, we readily admit. In like manner, 
 that a motive, if by this term be implied not only 
 the external object, but also the state of mind, to 
 which it is addressed, must uniformly be followed 
 by one and the same action, we do not hesitate to 
 affirm. But that a motive, considered as the mere 
 external and inciting cause, has any one action, 
 which independently on the mind, to which it is 
 presented, is uniformly connected with it, or can 
 be called its proper action, we deny : as we deny 
 also, that any physical agent, produces any one 
 precise and uniform effect, independently on the 
 circumstances of the subject, on which it acts, or any 
 effect, which, in all circumstances, is uniformly the 
 same, and can be called its proper effect. 
 
 By the term cause, you must be aware, is some- 
 times meant simply the agent, or the thing acting, 
 as opposed to the subject, or the thing acted upon. 
 The effects, which these causes, or agents, produce, 
 are various, according to the nature and circum- 
 stances of the subject, on which they operate. 
 The term motive, in like manner, sometimes means 
 simply the external object presented to the mind, 
 without any reference to that state of mind, to 
 which it is presented. Now, every motive, like 
 every physical agent, possesses a certain degree of 
 intrinsic strength ; but, as the effect, produced by 
 
109 
 
 the physical agent, depends on the subject, on 
 which it acts, so the effect of the external motive, 
 whatever may be its intrinsic force, depends on 
 the state of mind, to which it is addressed. If by 
 the term cause be implied all the actual antecedent 
 circumstances (and this is strictly its meaning), 
 then to produce an example of the same antece- 
 dents not followed by the same consequents, is a 
 physical impossibility. 
 
 The same impulse, which moves a billiard ball 
 to the distance of a hundred feet, may not move a 
 cannon shot to the distance of six inches, or a cube 
 of the same weight even one inch out of its place. 
 The effect depends not on the agent only, but also 
 on the subject, on which it acts ; and whatever ef- 
 fect is produced, it is the necessary result of the 
 previous circumstances. But there would be an 
 impropriety in considering the motion of the billiard 
 ball to the distance of 100 feet, to be the only pro- 
 per effect of the impulse, as if the motion of the 
 cannon shot to the distance of six inches were not 
 equally its proper effect. So it is with the opera- 
 tion of motives. A motive addressed to one mind 
 is followed by a certain action ; addressed to 
 another mind, or the same miricl, in different 
 circumstances, is followed by another action : but 
 there woutd be as great impropriety in calling the 
 former of the two actions, in exclusion of the lat- 
 ter, its proper action, as there would be in calling 
 
no 
 
 the effect of the former impulse the proper effect, 
 in exclusion of the latter. Ten pounds, placed 
 in one scale, make it preponderate against an empty 
 scale. Twenty pounds, in the opposite scale, will 
 make that scale preponderate in turn. And the 
 preponderation of the latter scale is no less the 
 proper effect in the second instance, than the pre- 
 ponderation of the former scale was in the first. 
 So it is with motives. Haifa guinea may induce 
 a porter to travel ten miles in a given direction : 
 the motive of a guinea opposed to this will make 
 him, in preference, travel ten miles in a different 
 direction. An obedience however to the former 
 motive, how often soever repeated, is no more 
 the proper action, than is the compliance with 
 the greater motive in the second instance. 
 
 I maintain therefore, that the expression, which 
 you employ, evinces the erroneous conception, 
 that the doctrine of Constant Conjunction implies, 
 that one and the same motive, can produce only one 
 and the same action, and must uniformly generate 
 one and the same volition, to whatever mind it 
 may be addressed. This action you name its 
 proper action. The error here involved is of equal 
 magnitude, and equally palpable, as if you affirmed, 
 that one physical agent must unifomly produce 
 one and the same effect, whatever may be the na- 
 ture of the subject, on which it operates, or by 
 whatever force it may be opposed. 
 
Ill 
 
 The schoolmen say, that, whatever power the 
 agent has to act, yet the action can be received by 
 the patient no farther, than the capacity of the pa- 
 tient reaches. 
 
 If by the term cause be signified the agent only, 
 then from one and the same agency may result 
 a variety of effects, all equally proper ; as from the 
 same motive, considered as the mere external im- 
 pulse, may result a variety of actions all equally 
 necessary, and all equally proper to the motive, 
 according to the states of mind, to which it is ad- 
 dressed. 
 
 But if by the term cause be understood not only 
 the efficient cause, or the physical agent simply, 
 but these taken in connection with the circum- 
 stances or nature of the subject on which they act, 
 then from one and the same cause so considered 
 can result only one and the same possible effect : 
 just as from one and the same motive presented to 
 the same feelings, disposition, and general state of 
 mind can result only one and the same action. 
 And to call either of these the proper effect, or the 
 proper action is a mode of expression nnphiloso- 
 phical and incorrect ; for it evidently implies the 
 absurd supposition, that there might be perhaps 
 some other effect, or some other action, the former 
 of which is as impossible in matter, as we maintain 
 the latter to be impossible in mind. The notion 
 of Cause separated from Effect, considered as an ab- 
 
112 
 
 stract conception, includes a contradiction. Tin 
 terms Cause and Effect are correlative, the one ne- 
 cessarily implying the other. 
 
 You err therefore, if you suppose, as your expres- 
 sion implies, that, according to the principle of 
 Constant Conjunction, with any external motive, 
 whatever may be its general effect, there is uniform- 
 ly associated one proper or definite action, in 
 whatever circumstances, or to whatever mind it 
 may be presented. 
 
 But, when you speak of a motive being separat- 
 ed from its proper action, let us understand your 
 meaning to be, that it is separated from that action, 
 which, when acting singly it had produced, or 
 which it would still produce, if unopposed. 
 
 Now let this separation f be granted ; for we do 
 not dispute the fact : on the contrary, when the 
 term motive denotes the external object simply, 
 and does not include the passion, appetite, or 
 state of mind, to which it is addressed, in other 
 words all the moving circumstances, we not only 
 admit, but consider it as a confirmation of our hy- 
 pothesis, that the same motive, presented to differ- 
 ent minds, or to the same mind in different circum- 
 stances, produces different effects. You conceive 
 this to be completely subversive of our doctrine. 
 
 1 I have adopted Dr. G.'s expression, as significant of his con- 
 ception ; but am fully sensible of the impropriety of the one, and 
 the inaccuracy of the other. 
 
113 
 
 i 
 But, if it shall appear, that no other separation 
 
 takes place, between a given motive and a given 
 action, than between a given physical agent, and a 
 given effect in similar cases, and that the laws of 
 mind and the laws of matter are, in this respect, per- 
 fectly analogous, then it must follow, that, if the 
 doctrine of Necessity be untrue, the acknowleged 
 principles of physics are equally false. It must 
 follow, that, if a motive does not act necessarily, 
 because it does not uniformly produce the same 
 action, so neither does a physical agent act neces- 
 sarily, because it is not uniformly followed by one 
 and the same effect. The doctrine of physics, and 
 the hypothesis of Necessity, must therefore fall to- 
 gether. Though this argument has been, in some de- 
 gree, anticipated, I shall take the liberty to enforce 
 it by a few additional observations. 
 
 Let us suppose, that a ship, impelled by the 
 wind sails directly South, at the rate of five miles 
 an hour. The motion of the ship is the effect, or 
 as you perhaps might call it, is the proper effect of 
 the wind impelling her. The agency of the wind, 
 and the motion of the ship southwards, are here 
 conjoined, as cause and effect. Let us now sup- 
 pose, that, after she has sailed some time in this 
 direction, she is opposed by a current, running di- 
 rectly North, at the rate of seven miles an hour. 
 The ship, now, instead of running South, as before, 
 is carried backwards in a northerly course. Now, 
 Let. H 
 
114 
 
 if by the proper effect be understood, that effect, 
 which the wind would have produced, if it had 
 been unopposed, here is a separation of the phy- 
 sical agent from its proper effect. 
 
 Let us state another case. Let us suppose a 
 weight of five pounds to be placed in one scale of 
 a balance, which we shall call A, and that the 
 other scale, which we shall call B is empty. The 
 five pounds in A will preponderate, and raise the 
 other scale. Let us then put ten pounds in the 
 empty scale ; will A still continue to preponder- 
 ate? It will not. B will now descend* and the 
 five pound weight is now separated from that ef- 
 fect, which acting singly it would have produced. 
 Precisely analogous to this case are the two mo- 
 tives, addressed to the porter. He is offered half a 
 guinea a mile for travelling in the direction A 
 C, and this half guinea would determine his vo- 
 lition, if no greater offer were made to him ; just as 
 the five pound weight determines the depression of 
 its scale, while unopposed by an equal or greater 
 weight in the opposite scale. But the porter is 
 likewise offered a guinea a mile for travelling in the 
 direction A B. The greater offer therefore 
 produces the preference in favour of A B, just as 
 the greater weight in the scale B causes its pre- 
 ponderation. In this case, neither is the weaker 
 motive connected with its proper action, if by this 
 expression be meant that action, which would 
 
115 
 
 have resulted, if the motive had been unopposed, 
 nor on the other hand does the lighter weight 
 Cause that preponderation, which it had previously 
 produced against an empty scale. The cases ap- 
 pear to me precisely analogous. Your argument 
 therefore proves nothing against our hypothesis, 
 which it does not equally prove against the con- 
 nection between a physical agent, and its effect. 
 
 You may perhaps reply, that the weight, Jive 
 pounds, still produces its effect, as it counteracts 
 the heavier weight, and diminishes its momentum. 
 But I must remind you, that, according to your 
 own repeated declaration, it is the result only the 
 overt action simply, which is the point in question, 
 and which your argument professes to regard. 
 Now, the result will take place, as certainly in 
 both cases, as if the superior motive, and the greater 
 weight, had been allowed to operate unopposed; 
 
 My objection, therefore, to your argument is, 
 that it proves nothing, concerning the separation, 
 as you term it, of a given motive from a given ac- 
 tion, which it does not equally prove, concerning 
 the separation of a given physical agent from a 
 given effect. As far, therefore, as your argument 
 regards the question, respecting the result, or overt 
 act, the hypothesis of Necessity, with the acknow- 
 leged doctrine of physical causes and effects, 
 must either stand, or fall together. 
 
 Having now shewn, that your notion of the prin- 
 
116 
 
 ciple of Constant Conjunction, is imphilosophicai 
 and false, having shewn also, that your argu- 
 ment, if valid, would militate equally against the 
 established principles of physical science, as 
 against the doctrine of Necessity, I shall conclude 
 my examination of the second horn of your di- 
 lemma, with one observation, to which I beg leave 
 to request your attention. 
 
 If half a guinea per mile is offered to a porter 
 for carrying a letter in the direction A C, he will, 
 it is to be presumed, accept the offer ; and for the 
 same remuneration will, in the same circumstances, 
 continue to perform the same service. The same 
 motive will be conjoined with the same action. 
 But, if it should happen, that double this remun- 
 eration is offered to him for carrying a letter, the 
 same distance, in the direction A B, will he then 
 accept the former offer, and travel in the direction 
 AC? We may warrantably answer in the negative. 
 But is this deviation from his general conduct 
 contrary to the principle of Constant Conjunction ? 
 To affirm it would, I conceive, betray an ignorance 
 of the plainest principles of philosophical science. 
 The doctrine of Constant Conjunction implies, 
 that the same antecedents are uniformly followed 
 by the same consequents; but never can be under- 
 stood to mean, that, when the previous circum- 
 stances are changed, an identity of effect is still to 
 be expected. The porter, therefore, will prefer 
 
117 
 
 the guinea to the half guinea ; and will, in the 
 same circumstances, uniformly choose the higher 
 remuneration. Now, if you can prove, either by 
 reason, or by experience, that the porter, addressed 
 by the same motive, and placed in the same cir- 
 cumstances, will sometimes act in one way, and 
 sometimes in another, now preferring the guinea, 
 and now the half guinea, governed by a capricious 
 and self-determining will, you will then disprove 
 the doctrine of Necessity. You will then prove, 
 that the principle of Constant Conjunction is irre- 
 concileable with the conduct of the porter. But, 
 while in the same definite circumstances, he inva- 
 riably acts in the same manner, obeying the minor 
 motive, when no other is presented, but preferring 
 the guinea, whenever it is offered to him, it is evi- 
 dent, that fcis conduct is strictly consistent with 
 the principle of Constant Conjunction, the same 
 motive, presented to him in the same circumstances, 
 being uniformly followed by one and the same 
 action, as the same physical agent, acting in the 
 same circumstances on a physical substance, is in- 
 variably followed by one and the same effect. 
 
 You seem to triumph in my admitting, that the 
 stronger motive will overcome the weaker, which, 
 you observe, is equivalent to an admission, that 
 the weaker motive is separated from its proper ac- 
 tion. The impropriety of the expression proper ac- 
 tion has been already shewn, and the notion im- 
 
118 
 
 plied, by it has been evinced to be imphilosophical. 
 I shall therefore now only repeat, that, as the ef- 
 fect of every physical agent depends on the sub- 
 ject on which, and the circumstances wherein, it 
 operates, so the action, resulting from any external 
 motive, is various, according to the state of mind, 
 to which it is presented. The analogy is clear 
 and obvious. A labourer, for many years, may 
 have performed a certain service for a crown per 
 day, nay, farther, this same hire may be a sufficient 
 motive, to induce him to perform the same work, 
 for many years. But is it necessary to the truth 
 of the Necessarian hypothesis, as implying the 
 principle of Constant Conjunction, that the con- 
 nection between the motive and the action must 
 be perpetual, whatever change of circumstances 
 may take place ; or that, if the doctrine of Necesr 
 sity be true, he should not prefer the offer of half a 
 guinea per day for other work to him equally easy ? 
 Surely not. Were it so, it would be equally neces- 
 sary to the truth of physical science, that the same 
 agent, in whatever circumstances it may act, shall 
 be accompanied with the same effect. But we 
 know, that this is not the fact, nor is it essential to 
 the truth of physical science, as implying the prin- 
 ciple of Constant Conjunction, that it should be 
 the fact. It is equally unnecessary to the truth of 
 our hypothesis, as implying the same principle, 
 that the same motive, to whatever mind it may be 
 
119 
 
 addressed, shall generate the same action. We 
 contend, that the will is governed by the strongest 
 motives, but we do not maintain, that a motive, 
 which may be strong enough now to persuade me 
 to a certain action, will ten years hence, or in very 
 different circumstances, persuade me to the same 
 action. Nor, because such is our doctrine, is it 
 therefore false. 
 
 Horace tells us a story of a soldier in the Ro- 
 man army, who, while he was asleep, lost all his 
 money and provisions. Mad with rage, and ex- 
 asperated against the enemy, he undertook with 
 some others, the hazardous enterprise of storming 
 one of their forts, and succeeded. His heroic 
 bravery was, on his return, liberally rewarded. 
 Lucullus, the general, having a service of great 
 danger in contemplation, was desirous to engage 
 our hero in the execution of it. " Go, " said he, 
 "my brave fellow, go, and again signalise yourself." 
 " No, No," replied the other very coolly. " Let 
 " him go, who has lost his knapsack." Here the 
 pecuniary circumstances of the soldier, and his state 
 of mind, had undergone a change ; and the motives 
 which formerly governed his will, and would, if 
 the same circumstances recurred, again govern it, 
 cease to influence him. He therefore leaves the 
 enterprise to be executed by one, who might be in 
 the same situation, and actuated by the same 
 motives, as himself, when he lost his provisions. 
 
 You observe, that, in cases, where we say, that 
 
120 
 
 one force is overcome by another, the meaning of 
 the phrase is widely different from that, in which I 
 wish to use it, for " that in all those cases, the force, 
 " that is overcome, has its full effect in weakening 
 " or lessening the sensible change in those lifeless 
 " bodies, which would have been produced by 
 " those stronger causes applied, if they had not 
 " been opposed." 
 
 I answer, that the expression to overcome can 
 admit only one meaning. It denotes simply the 
 superior action of one force, or one motive, over 
 another ; and can have no reference to the strength 
 of the inferior force, or motive, as either diminished, 
 or not diminished. It refers to the effect or overt 
 action simply ; and without a misconstruction, or 
 abuse, of the term, cannot either embrace, or ex- 
 clude, the accessary idea, to which you refer 
 The purport of your observation shall be after- 
 wards considered. 
 
 From the 16th to the 19th page your remarks 
 proceed, as if I had objected to the phrase Con- 
 stant Conjunction. To what objection do you al- 
 lude? I have re-examined my Essay, and so far 
 from finding any objection to this expression, I 
 cannot discover, that I have mentioned it, with 
 either censure, or approbation. The words ap- 
 pear to me to denote very clearly all, that we 
 know of causation, or the connection between 
 cause and effect. 
 
121 
 
 You proceed thus. " If you say, the inferences 
 " are false, you might be invited to try them ex- 
 " perimentally, with respect to physical causes ap- 
 " plied to a lifeless body ; but you would instantly 
 " perceive, without having occasion to try the ex- 
 " periments, that all the inferences are true. If 
 " you say, the inferences are all true, as following 
 " fairly and necessarily from a just principle, you 
 " might be invited to try them experimentally by. 
 " the application of motives to a living person ; 
 " but you would have no occasion to try the ex- 
 " periment, you would perceive instantly, that 
 " every one of them must be false." 
 
 Permit me to ask, what would you think of that 
 person's philosophical acquirements, who should 
 maintain, that, because in given circumstances, 
 the concussion of two non-elastic balls was not 
 followed by the same effect, as that of two elastic 
 balls, the effect in the former case was not phy- 
 sically necessary, or that it was contrary to the 
 principle of Constant Conjunction, and that in 
 the same precise circumstances the result might 
 have been different? And, if he should institute a 
 mathematical demonstration, in order to prove the 
 absurdity of maintaining, that a principle of Con- 
 stant Conjunction between antecedents and conse- 
 quents obtained in both cases, the effects being differ- 
 ent, I know no person, who would be less scrupu- 
 lous than yourself, in charging him with unpar- 
 
122 
 
 d enable ignorance of the very first principles of 
 philosophical science. What would you say, if he 
 should also contend, that, if the muriate of Ammo- 
 nia act necessarily in congealing water at a cer- 
 tain temperature, it must likewise, by the same ne- 
 cessity, allay the heat of anger, or abate the fury of 
 revenge? What opinion would you form of his 
 judgment, if he even proceeded to affirm, that, 
 because mathematical evidence operates neces- 
 sarily and irresistibly on the human mind, it must 
 act with the same necessity, and produce the same 
 effect on a block of marble ? What then shall we 
 say of that " rigid mode of reasoning" which pro- 
 ceeds thus ? If two physical forces acting neces- 
 sarily, according to the principle of Constant Con- 
 junction, impel brute matter in the line of the dia- 
 gonal, two contending motives, addressed to the 
 porter, an intelligent being, if they act necessarily, 
 must according to the same principle, impel him 
 also in the diagonal. Yet this very absurdity 
 is involved in your argument. 
 
 We know, that a lifeless body, under the influ- 
 ence of two physical forces, not acting in direct 
 opposition to each other, will describe the third 
 side of a triangle, whose other two sides would be 
 described in equal times, if the two forces acted 
 separately. We acknowlege also, that an intelli- 
 gent being, addressed by the two motives proposed 
 to the porter, would not describe the diagonal. 
 
123 
 
 We admit, therefore, that your inference in such 
 cases is true in Physics, and false in Metaphysics- 
 true in regard to matter, and false in respect to 
 mind. But I desire to know, how this difference 
 in the results can furnish any argument against 
 our hypothesis. How does it serve to prove, that 
 the relation between motive and action is not as 
 necessary, as between a physical force, and its 
 effect. Different agents, as I have repeated again 
 and again, acting on different substances, produce 
 different effects ; but do we infer from this diversity 
 in physical cases, that the effects are not neces- 
 sary ? Or do you mean to assert, that the princi- 
 ple of Constant Conjunction, or that necessity of 
 operation, whatever be the subject or the agent, 
 implies identity of result ? You will not venture to 
 affirm this absurdity ; but it is involved in your ar- 
 gument. 
 
 We admit therefore the facts, but we deny your 
 conclusion We apply the corollary to physics, 
 and we find the inference, as you term it, just. 
 The body describes the diagonal. We apply it to 
 the porter ; and we find the inference, that he also 
 will describe the diagonal, false. But we maintain, 
 that this diversity of effect can avail you nothing, 
 till you have proved, one, or other, of these two 
 positions, either, that the doctrine of Necessity di- 
 vests man of his mental pow r ers, or that necessity of 
 operation, implying a principle of Constant Con- 
 
124 
 
 junction, whatever be the agents, or the subjects, 
 implies identity of effect. When you have esta- 
 blished one, or other, of these positions, your ar- 
 gument will be invincible. 
 
 But, in order to exhibit it in a still stronger light, 
 let us apply it to the decisions of the rational fa- 
 culty, and we shall see then, what a " wonder- 
 " working argument" this dilemma will be found. 
 In order to illustrate its full force and efficacy, I 
 shall state a case so familiar and intelligible, that 
 the meanest understanding shall easily com- 
 prehend it, a case perfectly adapted to the capaci- 
 ties of those, who, you imagine, would be the rea- 
 ders of my Essay. 
 
 I shall suppose, that some plain unlettered man, 
 possessed, however, of sufficient common sense 
 and reflection to be persuaded, that his belief and 
 disbelief are necessarily governed by evidence, or 
 that he cannot believe, or disbelieve, as he 
 pleases I shall suppose, that this person has, by 
 some accident or other, lost sight of a friend, with 
 whom he was walking in the vicinity of Edin- 
 burgh ; and that, coming to a place, where the road 
 divided, one division leading Southward and the 
 other Westward, he enquired of some persons, 
 whom he there met, whether they had seen such 
 a person, as answered to the description of his 
 friend. One of them tells him, that he had met 
 him walking Southward six others of equal ere- 
 
125 
 
 dibility assure him, that they had met him walking 
 Westward. The latter information, of course, ap- 
 pears to him to be probably the more correct. The 
 evidence is much stronger, and he naturally yields 
 to it. Nor, indeed, is it possible for him to with- 
 hold his conviction, the testimonies singly being 
 supposed of equal credibility. He is therefore 
 just about to follow him on the South road, when 
 you accidentally come up, and understanding the 
 case, remonstrate with him on the course, which 
 he is going to take. You tell him, that it is vain 
 to talk about strength of evidence as necessarily 
 leading to this or that belief that we possess a 
 self-convincing power, and that we may believe, as 
 we please, that our judgments are not governed by 
 arguments, or by testimonies ; for if it were so, if 
 evidence had any necessary effect on our convic- 
 tions, it would be physically impossible for him to be- 
 lieve, that his friend had taken either the South, or the 
 West road, and that he must conclude, according 
 to the principle of Constant Conjunction, by an 
 irresistible necessity, that his friend had travelled in 
 the diagonal, or somewhere between the South and 
 the West points. The plain man may reply, " That is 
 " impossible : for I cannot believe contrary to all 
 " evidence. Besides, there is a strong moral impro- 
 " bability, that my friend would travel in that di- 
 " rection, where he would have to encounter 
 " ditches, and fences and walls." " That is an er- 
 " ror," you reply ; "and I can prove it, aye, prove 
 
126 
 
 " by mathematical demonstration. I can shew, 
 " that, if evidence has a necessary effect on the 
 "judgment, you must, under the influence of the 
 " contending testimonies, believe, that your friend 
 " went neither South nor West, but in a direction 
 " between them ; and if you act, according to what 
 " I shall prove, that you must believe, you will 
 " also follow him in the line of the diagonal, what- 
 " ever ditches, or houses may be in your way aye, 
 " follow him as certainly, as ever a shot from the 
 " mouth of a cannon described a parabola." On his 
 expressing some amazement at this very extraor- 
 dinary opinion, you very pertinently tell him, that 
 his surprise is very natural, that you perceive he is 
 no philosopher, that you presume he had never 
 read Bacon's " Novum Organum" or " Newton's 
 Principia" or your Demonstration, for that there 
 the question was as clearly proved, as any proposi- 
 tion in Euclid. And, should you, in order to 
 strengthen the argument, exhibit your Algebraic 
 formula and he still remain unconvinced, it would 
 be an easy matter for you, to resolve his obstinacy/*" 
 or rather blindness, into his entire ignorance 
 of Algebraic Notation. You might say, " If you 
 " doubt the truth of my opinion, you have only to 
 " try it in physics, and you will find it correct. If 
 "you assert my opinion respecting counteracting 
 " testimonies to be true, your own conduct in the 
 "present instance proves it to be false." Would the 
 man be convinced by this argument? Is there any 
 
127 
 
 person, endowed with common discernment, who 
 would be persuaded by this sophistry, that the 
 convictions of the understanding are not the ne- 
 cessary result of evidence? Is there any man, 
 who is but moderately versed in metaphysical 
 science, who would be thus convinced, that a 
 principle of Constant Conjunction does not obtain 
 between evidence and belief, and that the same 
 evidence, addressed to the same state of mind, is 
 not uniformly conjoined with the same convic- 
 tion ? Your argument however would prove the 
 contrary. 
 
 This is sufficient to expose its fallacy. 
 
 But the brief and satisfactory answer to your 
 dilemma is this. Your inference in physics is 
 true ; in metaphysics it is false : true in respect to 
 matter, false in respect to mind ; but it does not 
 hence follow, that the doctrine of Necessity is false, 
 nor will this conclusion be admitted, until you have 
 proved, that if matter and mind be each governed 
 by definite laws, analogous causes must produce, 
 in,, both, identical effects; and until you have 
 proved also, that the doctrine of Constant Conjunc- 
 tion implies, that the same agent, acting on a va- 
 riety of different subjects, must produce in all, one 
 and the same effect. 
 
 You proceed to call my attention to the follow- 
 ing passage of my Essay. " But as it must be 
 " acknowleged, that the porter will not move in 
 
1*28 
 
 " that direction, experience proving the fact, then 
 " it follows, that the law of physical causes, and 
 " that of motives do not coincide, and that the re- 
 " lation between motives and actions is not neces- 
 " sary, as between physical causes and their ef- 
 " fects." This passage, 'which appears in my Es- 
 say, as a quotation from yours, I have made, yon 
 say, the " subject of many severe, and angry ani- 
 " madversions, and even of reproaches to you? 
 Now, Sir, I must observe, that, when a charge of 
 this nature is alleged, it should be substantiated by 
 evidence. I have a right therefore, it is conceived, 
 to require of you to point out the angry animad- 
 versions and reproaches, to which you allude. The 
 strictures, Sir, which I have offered, regard your 
 whole argument, and have no particular reference 
 to this passage. And, suffer me to ask, what are 
 these angry animadversions ? these severe re- 
 proaches ? I have said, that your demonstration is 
 founded in error that it is inconclusive and 
 that it involves the absurd hypothesis, that all 
 causes, of whatever kind they are, and in whatever 
 circumstances they operate, must produce the 
 same effect. And are these to be termed angry 
 animadversions? Or can they, with any sem- 
 blance of truth, be called severe reproaches ? 
 And, these strictures, I repeat, refer to your whole 
 argument. Were I to descend to a species of am- 
 plification both puerile and ridiculous, I should 
 
129 
 
 say, "I am certain, there are no such reproaches 
 " on account of this passage in any paragraph 
 " of my Essay ; I am certain there are no such 
 " reproaches in any section of my Essay : I am 
 " certain, there are no such reproaches, en ac- 
 " count of this passage in the whole of my Essay 
 " from end to end." 
 
 The passage in question was intended to express 
 your conclusion, as if delivered in your own 
 words, and not as a quotation from your Essay. 
 Now, Sir, though I am conscious, that it was my 
 intention to express your meaning correctly, and 
 though I am persuaded, that every candid and at- 
 tentive reader must perceive, that nothing else 
 could be my intention, nay, though I am prepared 
 to prove, that no injury has been offered to your 
 argument, either here, or elsewhere, I confess, 
 there may be an impropriety in delivering as your 
 words, what are not your words, even though cor- 
 rectly exhibiting your sentiments. That the pas- 
 sage in question does no material injury to your 
 meaning, you yourself explicitly admit, in the 
 following terms. " However, as your mode of 
 " stating my question, though imperfect, does no 
 " material injury to my meaning, it is unnecessary 
 " to put any question to you, about it, or to make 
 " it the subject of any remarks." After this ac- 
 knowlegement, who would not expect, that the 
 subject would be instantly consigned to oblivion ? 
 Let. I 
 
130 
 
 Yet, as if determined to carp at trifles, and to mag- 
 nify into importance things wholly insignificant, 
 you proceed to expatiate on it triumphantly through 
 several successive pages. You say, " I am certain, 
 " that there is not in that paragraph of my Essay 
 " any such sentence, as that, at present in ques- 
 " tion, which you profess to have quoted from it ; 
 " I am certain, there is nothing like it, in that sec- 
 " tion of my Essay : I am certain, that I can find 
 " no such sentence, or any thing like it, in the 
 " whole of my Essay, from end to end." Was 
 ever a climax so elegantly constructed ? Was ever 
 a negation so concisely expressed? We have a 
 beautiful progression from paragraph to section, from 
 section to one end, and from one end to the other end, 
 and from both ends to the whole. Who, in senten- 
 tious brevity, can d ispute the palm with Dr. Gregory ? 
 You proceed ; " I am certain, that there are 
 " several clauses, in that pretended quotation 
 " of yours, widely different from any thing, that 
 " I ever thought of, or intended to express, 
 " and even inconsistent with the mode, and the 
 " subject of reasoning in that part of my Essay 
 "(the first horn of my dilemma), and indeed 
 " inconsistent with the tenor of my reasoning 
 " in the whole of my Essay. I am certain, that 
 " some of the expressions, which you have im- 
 " puted to me, are such as I did not generally, 
 " if ever employ, being such as I studiously avoid- 
 
131 
 
 <c ed, because I thought them either ambiguous, or 
 *' inconsistent with those distinctions, and that 
 " strict mode of reasoning, and above all that pe- 
 " culiar dilemma on which my demonstration is 
 " founded. For example you represent me as hav- 
 " ing said, that is, having answered, to my own 
 " question, that if the principle, on which Necessity 
 " is founded, be true, the porter must move in, tfie 
 " diagonal A D. It is impossible, that I ever 
 " should have thought such an absurd thing ; and 
 " I should think almost impossible, that I should 
 " have deliberately written and printed and re- 
 " vised my composition without discovering such a 
 " glaring absurdity. It also appears to me nearly 
 4C impossible, that I should not now be able to find 
 " that passage, if it really is in my Essay." What 
 a multiplicity of words, to deny a simple fact! 
 With what an astonishing talent you are gifted, 
 for spreading a small portion of matter over an 
 immensity of surface ! 
 
 In answer I quote your own words (p. 226.): " I 
 " say, that if the doctrine of inertia of mind be true, 
 " and the constant conjunction of motive and action 
 " be true, he will go in the diagonal A D, and that 
 "it is folly for him to make a pretence of think- 
 " ing, and ridiculous to make any words about it ; 
 " for go he must in that precise direction, as sure 
 " as ever a projectile moved in a curve." You 
 
132 
 
 add, " I say, that, if the porter do not go in that 
 " direction, the doctrine in question is false." 
 
 I do not understand the meaning of common 
 language, if this does not imply, that, if the hypo- 
 thesis of Necessarians be true, the porter must go 
 in that direction, and no other. Yet you so con- 
 fidently affirm, that you never did, nay never 
 could, say such a thing, and that you have not 
 been able to find such a passage in your Essay, 
 that, when I read your disavowal of it, I felt com- 
 pletely at a loss, how to reconcile your positive 
 declaration with the passage just quoted. You 
 now inform me, that the inference, which I a- 
 scribe to you, follows not from the principle of Ne- 
 cessity, which, you say, is the want of a self-govern- 
 ing power, but from the principle of Constant 
 Conjunction. In answer, it is observed, that 
 Priestley and Hume, against whom chiefly your 
 argument is directed, consider the doctrine of Ne- 
 cessity, as founded in the Constant Conjunction of 
 certain antecedents and certain consequents, in 
 the moral and intellectual world. I did not con- 
 ceive, therefore, that my expression could be mis- 
 understood. But, as I am not disposed to con- 
 tend about words, let us say, " He (Dr. Gregory) 
 ** answers, that, if the principle of Constant Con- 
 " junction exists between motives and actions, as 
 " between physical causes and effects, the porter 
 " must mov* in the diagonal A D." This alter- 
 
133 
 
 ation in the form of the expression will not affect 
 the pertinence, or weaken the force, of my reply. 
 You yourself acknowlege, that it does no material 
 injury to your meaning. However, in order to 
 prevent all future misconception on this subject, as 
 well as to preclude all captious objections, let it 
 be distinctly understood, that, when I speak of the 
 doctrine of Necessity, I consider it, in reference 
 to your argument, as founded in the principle of 
 Constant Conjunction. 
 
 You proceed to state, that " the supposed volun- 
 " tary actions of men may be supposed to be ab- 
 " solutely and irresistibly determined by motives, 
 " not constantly conjoined with their respective 
 " actions, just as their belief always is by evidence, 
 " many kinds of which are not constantly eon-, 
 "joined with the corresponding belief, and yet 
 " completely preclude all self-governing power, or 
 liberty with respect to belief." 
 
 Here you admit, that we have no self-governing 
 judgment, and that belief is the necessary effect 
 of evidence ; but, assuming that the different kinds 
 of evidence do not always produce, what you call 
 correspondent belief, you infer, that the principle 
 of Constant Conjunction does not obtain between 
 evidence and belief. Hence, you say, it is possi- 
 ble, that our actions may be necessarily and irre- 
 sistibly the effect of motives, and yet Constant Con- 
 junction not exist between motive and action 
 
134 
 
 Mere you betray the same erroneous and unphilo- 
 sophical notion of this principle, in relation to evi- 
 dence and belief, which has been already exposed, 
 in respect to motive and action, as also, in refer- 
 ence to a physical agent and its effect. If the 
 same physical agent be uniformly productive of 
 one and the same effect, the same external motive 
 of one and the same action, the same argument of 
 one and the same conviction, the subjects, on 
 which they act, being respectively in the same cir- 
 cumstances, in short, if the same antecedents are 
 uniformly in all followed by the same consequents, 
 the principle of Constant Conjunction must then 
 be admitted to subsist in all. But you erroneously 
 conceive, that this principle cannot exist between 
 motive and action evidence and belief, unless 
 the same motive, to whomsoever presented, the 
 same argument, to whomsoever addressed, are 
 respectively followed by one and the same action 
 one and the same belief; or what you term the pro- 
 per action the corresponding belief. This notion 
 of the principle in question, I conceive to be un- 
 philosophical and false. A certain quantity of 
 caloric applied to a resinous substance will soften 
 and liquify it ; the same quantity, applied to moist 
 argillaceous earth, will desiccate and harden it. 
 Because the effect of the same agent on different 
 substances, is here different, do you deny the ex- 
 istence of Constant Conjunction between the an- 
 
J35 
 
 tecedents and the consequents? Why then do you 
 deny it in intellectual cases, because the same 
 motive, or the same argument, addressed to differ- 
 ent men, or the same man in different circumstan- 
 ces, does not produce one and the same action 
 one and the same conviction ? Produce an exam- 
 ple, in which the same motive, the same argu- 
 ment, addressed to the same state of mind, is not 
 followed by one and the same result, and your 
 notion will be allowed to be correct ; till then, it 
 must be pronounced unphilosophical and false. 
 
 When you assert, then, that a principle of Constant 
 Conjunction does not exist between evidence and 
 belief, though there is no self-governing judgment, 
 and thence infer, that motives might be supposed 
 irresistible, though the principle of Constant Con- 
 junction did not exist between motive and action; 
 you assert, as a truth, what is repugnant to truth, 
 and your argument from analogy leads to a con- 
 clusion, the very reverse of that, which you wish 
 to establish. The cases are precisely parallel. 
 As the same moral evidence is not always accom- 
 panied with the same belief, the conviction depend- 
 ing on the state of intellect, to which it is address 
 ed, so the same motive does not uniformly pro- 
 duce the same action ; the result being various, ac- 
 cording to the different views, sentiments, and dis- 
 positions, to which it may be presented. But, 
 while the same motive, the same evidence, present- 
 
136 
 
 ed to the same state of mind, are uniformly accom- 
 panied with one and the same action, one and 
 the same conviction, the same antecedents either 
 to the volition, or the belief, being uniformly con- 
 joined with the same consequents, the principle of 
 Constant Conjunction equally exists between mo- 
 tive and action, as between evidence and belief. 
 
 If you, however, can explain the numerous facts, 
 which might be adduced in confirmation of this 
 doctrine, consistently with the supposition, that 
 Constant Conjunction does not subsist between 
 evidence and belief ; or, if you can prove, that 
 the same evidence, addressed to the same state of 
 mind, is not uniformly conjoined with the same 
 belief, your supposition, that necessity may exist, 
 where the principle of Constant Conjunction is ab- 
 sent, and your assertion, that this is the fact, in re- 
 spect to evidence, and belief, will then be admitted 
 to be philosophical and correct. But, until you 
 have accomplished this, your parallel must be pro- 
 nounced to be subversive of your own argument, 
 and as rendering your complaint, with your ob- 
 jection, nugatory. 
 
 You proceed to observe, that " the relation of 
 " motive and action may be supposed strictly ne- 
 " cessary, like those of quantity, contemplated by 
 " Mathematicians, and neither proceeding from 
 " the wise institution of the Supreme Being, nor 
 " changeable by his power, and yet we might have 
 
137 
 
 " either perfect self-governing power, or various 
 " degrees of it, provided only the relation of mo- 
 " tive and action was not a constant conjunction. 
 " for this effectually precludes any self-governing 
 " power." 
 
 How the relation of a physical cause to its 
 effect, or of a motive to its action, could ever be- 
 come, or even justly be supposed to be, a necessary 
 relation, in the same strict sense, in which the re- 
 lations of number and quantity are necessary, is to 
 me wholly inconceivable. For, whether the con- 
 nection between them were the original and unalter- 
 able ordination of a Supreme Being, or whether it 
 were founded in certain uncornmunicated, inherent 
 and unchangeable properties in the subjects them- 
 selves, independent on any intelligent power, still 
 to deny the necessary relation, or to affirm, in any 
 given case, that the relation would cease to exist, 
 would be only to affirm an impossibility ; but to 
 deny a mathematical truth, is to affirm a contradic- 
 tion. If the sun rose and set, by powers inherent 
 in matter, and inseparable from it, to assert, that 
 he might not rise to-morrow, would be to assert a 
 physical falsehood ; but there would be no absur- 
 dity in the proposition : his not rising would be at 
 least conceivable. But to affirm, that a whole is 
 less than all its parts, or that two quantities, 
 each equal to another quantity, are not equal to 
 each other, is to affirm a contradiction. And I 
 
138 
 
 can no more conceive, how, on your supposition? 
 a self-governing power could exist, or how the 
 principle of Constant Conjunction could be ex- 
 cluded, than I can conceive, how the relation, 
 of antecedence and consequence between two phe- 
 nomena may be unalterably fixed, and yet the one 
 not followed by the other. Were the relation be- 
 tween a given motive and a given action immuta- 
 ble and eternal, like the relation between one 
 quantity and another, we should be warranted 
 in affirming, not merely that they were constantly 
 conjoined, but indissolubly connected. 
 
 You complain, that I have represented you, as 
 saying, that " the porter will not move in the diago- 
 " nal, experience proving the fact." This, you ob- 
 serve, you never said ; and with that peculiar ta- 
 lent for brevity and concentration, which displays 
 itself in every affirmation, negation, or illustration 
 of yours, you proceed to say, " I do not remem- 
 " ber to have said this, or any thing like it. I 
 " never heard of the experiment having been tried. 
 " I do not believe, it ever was tried. I am sure, 
 " there is no occasion to try it ; and I declared, 
 " that I would not try it ; and gave my reasons for 
 " that resolution." Amplification is a rhetorical 
 figure, in which every reader must acknowlege 
 your singular proficiency. 
 
 Permit me to ask, if you are sure, that there ex- 
 ists no occasion to try the experiment, and if you 
 
139 
 
 are convinced, that the porter will not take the di 
 agonal, whence arises this conviction, this certainty 7 
 but from experience? Will abstract reasoning as- 
 certain the fact ? Or is the truth to be inferred by 
 any metaphysical deduction ? Or do you mean to 
 deny, that your persuasion is not the result of ex- 
 perience ? If you do not, to what purpose is your 
 observation ? You state, that you never heard of 
 the experiment being tried ; and that there is no 
 occasion to try it. In this opinion we are agreed . 
 But I have no where said, that the experiment was 
 ever made: but that experience proves the fact. 
 Now, Sir, when you have learned the distinction 
 between experiment and experience (and you, who 
 profess to read and admire Bacon, should know' 
 this distinction), between knowlege acquired by 
 trial, and that which is attained by observation, 
 when you have learned this distinction, you will 
 then perceive, that your complaint is rather cap- 
 tious, than well founded, betraying at the same 
 time, inattention to a difference, which must be fa- 
 miliar to understandings, even of the lowest order. 
 You complain next, that I represent you, as 
 saying, that the law of phyical causes, and that of 
 motives, do not coincide. You ask, where you 
 have said this. I answer, that you have not used 
 these words ; but you have expressed the same sen- 
 timent, as I intended these words to convey, that 
 the same principle of inseparable conjunction, 
 
140 
 
 which obtains in physical causes and effects, does* 
 not obtain in motives and actions. And to carp 
 thus, at an expression, which by your own confes- 
 sion in no respect injures your argument, betrays 
 a spirit, which a good cause needs not, and which 
 a dignified mind would scorn to exhibit. 
 
 You complain next, (for there is no end to your 
 complaints, and they are all of the same stamp) 
 that I ascribe to you the opinion, that, because 
 the porter does not go in the diagonal, the relation 
 between motive and action is not necessary, as 
 between physical causes and their effects. Here 
 also you carp at words, and lose sight of the main 
 argument. I have used the term necessary through 
 the whole Essay, as applicable not only to the re- 
 lations of quantity and number, but to the relation 
 also between Cause and Effect in Physics founded 
 in the uniform and established constitution of 
 things ; and this usage is sanctioned by indisputa- 
 ble authority. But I dislike logomachies ; and 
 have no objection to any other term, which you 
 may prefer. Instead of necessary relation, let it 
 be, if you will, constant connection, inseparable con- 
 junction, or what you please. It will neither sub- 
 serve your argument, nor injure mine. 
 
 Your objections and complaints remind me of 
 an anecdote, told of Marmontel. Renault, the 
 president of the Academy, opposed Marmontel's 
 admission into the society ; or at least threatened 
 
141 
 
 to vote against him. Madame Geoffrin applied to 
 him in favour of Marmontel. On her return from 
 the President's house, she told her friend, that he 
 had offended the President. " What is my offence, 
 Madam T said he. " He has not told me, but I 
 believe, it is of your book, that he complains. I 
 shall however take care to know the cause." At 
 last the President informed her, why he was of- 
 fended. " Well, Madam, you have seen the Pre- 
 " sident again ;" said Marmontel: " has he told you, 
 " what has been my offence ?" "Yes, I know it now, 
 " but he forgives you : he is willing to forget it ; 
 " let us say no more about it." " At least, Madam, 
 " I ought to know, what this involuntary crime is, 
 " which he has the goodness to forget; I promise 
 " never to mention it ; Pray, let me know, what it 
 " is." " What it is ? Why always your book, and 
 " your rage foe citations. I think you have your 
 " book there." " Yes, Madam, there it is." " Let us 
 " see that song, which you have quoted among your 
 " drinking songs." " Here it is. 
 
 " Console me for a mistress, that's false." 
 
 " From whom had you this song T " From Geliote." 
 " Well then, Geliote has not given it you, such as 
 " it really is If 1 must tell you, you have left out 
 " an Oh" " An oh, Madam T " Yes, an oh. Is there 
 " not averse, which begins "What charms?" " Yes, 
 " Madam, 
 
 " WhaU^hanns, ye heavens, what beauty !" 
 
 " That's it : there's the fault. You should have 
 
142 
 
 " said, Oh ye heavens, what beauty /" " Why, Ma- 
 " dam, the sense is the same." " Yes, Sir ; but 
 " when you cite, you should cite correctly. What 
 " has he done to you, that you should deprive him 
 " of his oh F 
 
 Now, Sir, Marmontel may possibly have spoiled 
 the President's poetry ; but I am confident, that by 
 no citation, no statement, no expression of mine, 
 has your demonstration been injured. 
 
 Ydu conclude your laboured and tedious com- 
 plaints on this subject, with remarking what gross 
 injustice I have done you, in half a page of niy 
 Essay. When I read your letter, not stopping to 
 compare these complaints with either your work 
 or my own, and perceiving charge after charge of 
 shameful misrepresentation, I began to apprehend, 
 that I had in a variety of instances mis-stated your 
 argument. What was my surprise, when I found 
 the whole confined to eight or ten lines, unfortu- 
 nately given as your words, as they were intended 
 by me to express correctly your ideas What was 
 my surprise, when I found, that notwithstanding 
 your loud and reiterated complaints, I had, even 
 by your own confession, not materially injured 
 your argument! 
 
 In short, through the whole of your objections, 
 you appear not so much like an able reasoner, 
 overlooking trifles, seizing the main argument, 
 
143 
 
 and standing firm on solid ground ; as like a per- 
 son in the article of drowning, flouncing from 
 place to place, and catching at every straw to pre- 
 serve you above water. 
 
 You say, that I have unjustly imputed to you 
 the absurdity of maintaining, that all causes of 
 whatever kind must produce the same effects. In 
 answer, I observe, that I have not charged you 
 with maintaining this absurdity ; (for who in his 
 senses could assert so monstrous a position ?) but 
 I have affirmed, that your demonstration radically 
 involves this absurdity. 
 
 Having replied to your complaints, and having 
 evinced the fallacies of your argument, I will not 
 detain the reader, by stopping to expose the incon- 
 sistency, with which you are chargeable, in your at- 
 tempt to defend the application of Mathesis to a 
 metaphysical subject, 1 nor the erroneous and un- 
 warranted conclusion, which you have drawn 
 from Priestley's observation, respecting the conca- 
 tenation of causes and effects. Before I proceed, 
 however, to answer the remainder of your letter, 
 and to re-examine your argument in its Algebraic 
 dress, I will take the liberty to offer one or two 
 observations. 
 
 You inform the reader in your Essay (p. 103.) 
 that you mean to prove, " that motives are not 
 quantities." Now, Sir, if they are not quantities, 
 
 * See Essay, p. 86". 
 
144 
 
 desire to know, how they admit increase and di- 
 minution, of which you yourself acknowlege them 
 to be susceptible. Do you intend to prove, that 
 a guinea, a sovereign, or a shilling, are not quanti- 
 ties? that a crown is not double its half, and 
 half of its double ? I am exceedingly desirous to 
 see this demonstration, and request to be refer- 
 red to the page, or pages, in which it is exhibited. 
 Do you mean to prove, that love and hatred, joy 
 and grief, desire and aversion, do not admit degrees, 
 and that mankind have erred, and still err, in sup- 
 posing that there can be greater or less benevolence, 
 greater or less malignity, higher or lower hope ? 
 This would, indeed, be a singular discovery in the 
 philosophy of the human mind. That they are not 
 proper quantities, and therefore not fit subjects of 
 Mathematical demonstration, is allowed ; but that 
 they have quantity, as admitting increase and di- 
 minution, is one of those plain truths, which, as 
 far as I know, has never yet been controverted. 
 
 Again. " According to Mr. Hume's system," 
 you observe, " the motive should be considered 
 " as the cause of the action, not indeed directly 
 " without volition, or in opposition to it, but by 
 " means of it ; the motive first influencing the will, 
 " and producing volition, and this again producing 
 ' action. So that, in short, every volition, and ac- 
 if tion, may fairly be regarded as an effect, indicat- 
 *' ing the kind, and measuring the degree of its 
 
145 
 
 " cause, as much, and as certainly, as any change, 
 " commonly termed an effect, in inanimate nature." 
 (Essay p. 85.) 
 
 Here you assume as a fact, what the science of 
 physics, and that of metaphysics, equally reject as 
 such. On what authority, permit me to ask, do 
 you presume, that the kind of the cause is indi- 
 cated, and its degree measured, by the effect sim- 
 ply ? Is this one of those propositions, on which 
 as universally, or metaphysically true, you presume 
 to found the justification of your attempt ? Is the 
 simple effect in physics uniformly a correct mea- 
 sure of the degree of its cause, or an indication 
 of its kind ? Reflect a little, and you will per- 
 ceive your error. If you beheld a house lying in 
 ruins on the ground, would you in all such cases, 
 be able to determine from the mere effect, whether 
 it had fallen, by reason of its own instability, or 
 had been thrown down by a hurricane, or had 
 been demolished by human hands ? How could 
 you determine either the kind of the cause, or its 
 degree ? When, as the story is told, the bell of a 
 country parish church unexpectedly at midnight 
 began to ring, from the effect you, doubtless, 
 would have inferred the agency of human power, 
 and perhaps also the degree of that power. But 
 the fact would have proved your philosophy to 
 be false. An ass, tied to the bell rope by some 
 wags, would have borne testimony, that neither the 
 />/. K 
 
146 
 
 'kind, nor the degree, of the cause is always de- 
 ducible from the mere effect. 
 
 I acknowlege, that motives and their results, 
 may, in certain cases, be so far capable of measure- 
 ment, that from the greater, or less degree of the 
 action, we may infer a greater or less degree of 
 intensity in the motive, and conversely. If your por- 
 ter carries a burden ten miles for a guinea, we may 
 conclude, that he will carry it twenty miles for 
 two guineas, and five miles for half a guinea. 
 But do the service and the remuneration uniformly 
 bear the same definite ratio to each other? or 
 are we justified in deducing the quantum of the 
 one from that of the other in all cases ? Certainly 
 not. For, as a physical cause may be more 
 than sufficient to produce the effect, so a motive 
 may be greater, than suffices to produce the ac- 
 tion. If I see an insect lying crushed on the 
 ground, I cannot determine from the mere effect, 
 by which of the numerous adequate causes that 
 effect may have been produced, whether by the 
 foot of a man, for example, or the foot of a horse. 
 All that I know, is, that the cause must have been 
 sufficient to produce the effect, and that the one was 
 necessarily followed by the other. If I am told, 
 in like manner, that your porter carried a parcel 
 ten miles, I cannot determine whether he received 
 one guinea, or two guineas, or more, or whether 
 he carried it gratuitously, through friendship, or 
 
147 
 
 reluctantly by compulsion. All that I know is, 
 that the motive must have been adequate to the 
 action, and that from the application of the 
 motive the action necessarily followed. Thus it is 
 evident, that, as the degree of a physical cause is not 
 always to be measured, or its kind indicated, by 
 the simple effect, so it is equally clear, that the mere 
 action is not uniformly a correct exponent of the 
 motive, either in kind, or in degree. The cases are 
 precisely parallel. When you assume, then, that 
 both the kind, and the degree of a cause in physics 
 are to be universally inferred from the simple ef- 
 fect, and on this assumption ground your applica- 
 tion of Mathesis to the hypothesis of necessity, you 
 presume an error, an error too betraying extreme 
 inattention to the plainest, and most obvious facts. 
 You assume what is not true, that the simple effect 
 indicates the kind, and measures the degree of its 
 cause in physics, as it is not true, that the action is 
 invariable, a correct exponent either of the kind, or 
 the degree of the motive by which it is produced 
 I proceed now to reply to the remainder of your 
 Letter. 
 
 In discriminating the different kinds of oppo- 
 nent motives, it matters little, what designations 
 be employed but it is of supreme importance, 
 that the distinctive characters be clearly explain- 
 ed, and fully understood. 
 
 1st. When motives are opposed to each other, 
 
and yet in their operation are combinable, as in 
 the case of a parent prompted by anger to punish 
 a child, and restrained by affection, these motives 
 may be called counteracting combinable motives. 
 The effect partakes of each motive, and resembles 
 the result produced by the indirect action of two 
 physical forces on a physical body, which under 
 their combined operation describes the diagonal 
 of a parallelogram : or it may be compared to the 
 commixture of two liquids, producing a com- 
 pound, which partakes of the qualities, or proper- 
 ties of both. 
 
 2dly. Motives may be opposed to each other 
 which are incapable of combination. Thus the 
 porter may be prompted to travel Southward, by 
 the offer of a guinea per mile, and may have the 
 promise of half a guinea per mile for travelling 
 Westward : but the latter motive, though uncom- 
 binable with the former, subtracts nothing from its 
 efficacy. It is not a motive of disadvantage ; but 
 is clearly of a positive nature. There is a gain on 
 the one side, and no loss opposed to it, on the 
 other. The motives, though they come in com- 
 petition with each other, are of one and the same 
 kind. These I shall call opponent uncombinable 
 motives. 
 
 3dly. When motives directly counteract each 
 other, and are incapable of being combined, the wea- 
 ker destroying the force of the stronger, to the full 
 
149 
 
 amount of its own power, these may he called 
 counteracting and nncomhinahle motives. A per- 
 son, for example, may be prompted to enter into a 
 speculation in trade, hy the hope of a certain ad- 
 vantage, and may at the same time be restrained 
 by the certainty of incurring an equal, or a greater 
 loss. Here the opponent motives are directly 
 hostile to each other, positive and negative, like 
 plus and minus quantities in Algebra ; whereas, in 
 the second division, the motives may be regarded, 
 as of one character, and may be said to be both 
 positive, the important difference being, that both 
 cannot have effect. 
 
 To the distinction between these two classes of 
 motives, I would beg leave to request the particu- 
 lar attention of the reader The difference indeed, 
 between them is sufficiently obvious, and can hard- 
 ly fail to present itself to any reflecting mind. 
 Yet it is not a little remarkable, that in a work of 
 two volumes octavo, containing a profusion of illus- 
 tration, and an abundance of irrelevant matter, 
 the important distinction between these two clas- 
 ses of motive, seems to have been dismissed with 
 little or no attention. 
 
 You profess, indeed, to have considered the 
 theory of counteracting uncombinable motives ; 
 and you acknowlege, that the difference between 
 them, and opponent uncombinable motives, is as 
 great, as the difference between minus and plus* 
 
150 
 
 It must be matter of surprise then, that you omit- 
 ted to investigate the effects produced by the ap- 
 plication of such motives, and to apply your 
 demonstration to them also. But this application 
 would have involved you in a dilemma, whence no 
 efforts of human ingenuity could have availed to 
 extricate you. You assign, it is true, two reasons 
 for waiving the consideration of these motives. 
 You profess to have considered them, but you re- 
 served them for some future discussion. They were 
 to be brought forward " in due time." Twenty- 
 six years have since elapsed ; but the due time, it 
 would seem, has not yet arrived. They have not 
 yet been made the subjects of your Mathematical 
 argument. The second reason, you offer for post- 
 poning this discussion, appears evidently irrecon- 
 cileable with your own admission. You plead 
 as an excuse, that the application of this species 
 of motives cannot be brought to the test of expe- 
 rience. If this be the fact, it might serve as a 
 reason for dismissing them entirely from considera- 
 tion, but furnishes surely no sufficient apology for 
 delaying the discussion. But let us overlook the 
 weakness of this excuse. You plead as a reason 
 for omitting to examine them, that they cannot be 
 brought to the test of experience. How shall we 
 reconcile the validity of this excuse, with your 
 own positive acknowlegement, that they are 
 actually and repeatedly, nay daily and hourly, 
 
151 
 
 brought to this test? For you inform us, (p. 41.) 
 that they are not so remote from the business of 
 common life, as at first may be thought, " and 
 " that, though individuals cannot make such experi- 
 " ments on one another, they have been often made, 
 " on a great scale, by sovereigns and legislators' 
 " that taxes and tithes are counteracting motives," 
 and with your peculiar pleasantry, add, that " the 
 " fear of the gallows, or pillory, the whipping post, 
 " or the jail, are counteracting motives applied, as 
 " you (humbly) hope, not to the majority, but to 
 " a respectable minority of mankind." Now, Sir, 
 I beg leave to enquire, how you reconcile the 
 asserted difficulty of bringing them to the test of 
 experiment with the acknowleged fact, that we 
 experience them daily You acknowlege, that a 
 " tithe strictly taken in kind, or a great increase 
 " of rent, or other penalty for plowing up a 
 " meadow are counteracting motives, applied to 
 " farmers." Where then is the difficulty, or 
 where the necessity, of bringing them to the test 
 of formal experiment? Your excuse for omit- 
 ting the consideration of these motives is irre- 
 concileable with your own admission, at vari- 
 ance also with your professed intention to employ 
 them " in due time" for the purposes of illustra- 
 tion. 
 
 Before I proceed to examine your analytical 
 argument, there is one animadversion, to which I 
 
152 
 
 deem it necessary to reply. " You remark, that, 
 " after my inference, that the preponderance of the 
 " greater weight is impossible, I subjoin two impor- 
 " tant questions ; and that, what I have shewn to 
 " be absurd, and impossible, with respect to the 
 " balance, is yet true, with respect to the use of 
 " that instrument, in point of fact." 
 
 Here it is evident, that you have misunderstood 
 the purport of my reply. The inference is not 
 mine ; but is deducible from your argument. I 
 did not mean to say, that it would be absurd to 
 believe, that the greater weight would preponder- 
 ate, but to shew, that your argument would prove 
 such belief to be absurd, and that by disproving 
 the preponderance, it would disprove a known 
 fact. My object in employing your formula, and 
 retorting your argument is 1o prove, that whatever 
 absurdity your demonstration would fasten on the 
 doctrine of necessity, attaches with equal force to 
 an acknowleged principle in physics, and thus, 
 by proving too much, proves nothing. My words 
 are these, " in short you must acknowlege, either 
 u that there is no absurdity in the Necessarian 
 " hypothesis, or that an equal absurdity embarras- 
 44 ses the system of physics, and deny the most 
 " obvious and common phenomena." If there 
 be a typographical error in the notation, as I 
 acknowlege there is, and which, in the correction 
 of the press, escaped my attention, it is such an 
 
153 
 
 error, as any person, from the evident scope of my 
 argument, may easily correct. For, with the least 
 attention, he cannot fail to perceive, that it was my 
 design to retort your argument, and to shew, that 
 it would demonstrate an acknowleged fact to be 
 an absurdity. This, it is obvious, could not be 
 accomplished, unless by a faithful transcript of 
 your formula and a strict adherence to your mode 
 of reasoning. Accordingly, after stating the con- 
 clusion, as applied to two weights, I ask, (p. 377.) 
 " Is this conclusion agreeable to fact?" by which it 
 is meant to be enquired, whether your mathematical 
 deduction, as applied to two weights, instead of 
 two motives, namely, that the greater weight will 
 not preponderate, be agreeable to fact? And, 
 when I subjoin to the demonstration, as you name 
 it, the words, " which is absurd," I employ your 
 own expression, as applied to motives, contending, 
 that, if you conclude your argument, as applied to 
 motives in that form, and to that effect, you must 
 conclude it also, as applied to the two weights, in 
 the same form, and to the same effect. Had you 
 duly attended to the purpose of my retorting the 
 argument, it would have saved the necessity of 
 the numerous, and superfluous queries, in your 
 second letter, concerning the nature of a deduct 10 
 ad absurdum ; but you delight in dilatation, and I 
 ought not perhaps to regret, that I have furnished 
 scope for your favourite exercise. 
 
154 
 
 _ Your gracious and liberal supposition, that ray 
 error originated in my ignorance of common Alge- 
 braic Notation, may be dismissed without remark. 
 But, if you are solicitous to know, how far your 
 supposition is correct, I shall be proud to gratify 
 your curiosity, by referring you to the incontestable 
 evidence of Academical documents. In the mean 
 time, you will pardon me for observing, that your 
 admirable facility in accounting for the errors of your 
 opponents, on this, as on other occasions, and the 
 ease, with which you infer, that they differ from 
 you, because they are not conversant in Mathe- 
 matical science, are calculated only to excite a 
 smile. " They have not yet learned the common 
 symbols of Algebra : hence they comprehend not 
 the ingenuity of your argument. Let us now pro- 
 ceed to examine your demonstration. 
 
 After stating, as the doctrine of Necessity, that 
 when motives are exactly equal, action becomes 
 impossible, you suppose two equal motives, each 
 conjoined, when acting separately, with what you 
 term its proper action. Your first proposition 
 therefore is, 
 
 X=A-Y~B 
 
 the motive X being conjoined with the action A, 
 and the motive Y with the action B. You then 
 state these motives, as opposed to each other, in 
 which case, according to our hypothesis, no action 
 can take place, 
 
155 
 
 X Y-0-0 
 
 that is, the force of the one motive, destroying that 
 of the other, no effect is produced. You then 
 state, as the doctrine of Necessity, that the former 
 motive, though lessened by part of the latter, still 
 retains its whole force, and therefore produces its 
 full effect, as if unopposed, thus, 
 
 X J-X^A. 
 
 m 
 
 This you observe involves an absurdity. Let us 
 examine this argument, 1st. as purely mathematical, 
 and 2dly as applicable to certain physical causes, 
 and effects. 
 
 Mathematical demonstration has been defined 
 to be a series of axiohis, or of truths resolvable 
 into axioms. Every proposition, in a Mathema- 
 tical chain of reasoning, is a necessary deduc- 
 tion from some other proposition or link in that 
 chain, or from some necessary truth previously 
 demonstrated. Nor can that surely be called a 
 Mathematical demonstration, in which the con- 
 clusion is no deduction from any of the premises, 
 much less, where it is in direct contradiction to 
 these premises. That this is the character of your 
 third equation it requires not a moment's attention 
 to perceive. If X be equal to Y, by what axiom 
 do you prove, that X diminished by JT is equal to 
 
 zW 
 
 X ? If it is no deduction from either of the 
 preceding propositions, where is your proof: 
 
156 
 
 where your simple chain of evidence ? Is 
 a bare assertion to be deemed proof? It is 
 vain to urge, that the doctrine of necessity leads 
 to this absurdity : it was incumbent on you to 
 prove it ; you engaged to prove it mathematically. 
 To affirm that this, or that, hypothesis leads to 
 absurdity, whether that affirmation be expressed 
 by words, or Algebraic symbols, is surely not 
 argument, much less demonstration. But it would 
 seem, that, though you conceive, that the assertion, 
 that any proposition is absurd, is not a proof, no 
 sooner do you clothe the affirmation, in an Alge- 
 braic garb, than it becomes immediately a de- 
 monstration. There is a virtue, it would appear, 
 in these symbols, which Mathematicians, and men 
 of science have yet to learn. 
 
 Let us now examine it as applicable to certain 
 physical causes and effects. In order that the 
 reader may perfectly comprehend your argument, 
 it may be necessary in the first instance to exhibit 
 your application of it to a supposed casein motives. 
 Let it be supposed then, that the motive X, or a 
 guinea per mile, is sufficient to induce your porter 
 to travel Eastward, expressed thus X =A ; that 
 the motive Y, likewise a guinea per mile, is suffici- 
 cient to induce him to travel Westward, expressed 
 thus, Y ~B. Hence X B A~ Y EB. Then both 
 motives being presented at once, we have X Y 
 O O. Though the mode of notation be objec- 
 
157 
 
 tionable, we admit the proposition, which it is in- 
 tended to express ; for, the motives being equal to 
 each other, and all other circumstances being 
 supposed equal, there could be no ground of pre- 
 ference, and therefore no action, till some addi- 
 tional motive, or cause, of some kind, how r minute 
 soever, presented itself, to decide his choice. We 
 believe farther, that, if the porter were offered only 
 half a guinea a mile, for travelling Westward, and 
 a guinea a mile for travelling Eastward, that he 
 would prefer the latter. This, you say, is an ab- 
 surdity equal to maintaining, that, " if 10 be de- 
 " ducted from 10, there will remain ; but that, if 
 " 10 be deducted from 11, there will remain 11." 
 If there be any thing here beside mere assertion, I 
 frankly confess, that I have not penetration enough 
 to perceive it. Now, Sir, this assertion is either 
 intuitively true ; or it is not. If it be strictly self- 
 evident it is incapable of proof; and to demon- 
 strate an axiom is a singular attempt, in the history 
 of Mathesis. If it be not self-evident, permit me 
 to ask, where is your proof? Where are your major 
 and minor propositions, whence your conclu- 
 sion is drawn? But it would seem, that though 
 this affirmation of absurdity, when expressed by 
 common visible signs, be nothing but simple as- 
 sertion, it is no sooner arrayed in Algebraic dress, 
 than by some inexplicable process, it becomes " a 
 
158 
 
 %t sirnj>le chain of reasoning," a scientific proof, a 
 mathematical demonstration. 
 
 . 
 
 M 
 
 There must be, as has been already remarked 
 some strange and magical virtue in these Agebraic 
 symbols, combined with your newly invented cha- 
 racter, which can convert an affirmation into a 
 proof -- an assertion into a demonstration. For, 
 if there be any thing, beside a mere affirmation of 
 absurdity in your vaunted proof, I confess myself 
 entirely ignorant of the essential character of all 
 argument. 
 
 Let us now apply it to a case in physics, and 
 we shall not fail to perceive its superlative merit. 
 It proves, if it prove any thing, what no ordinary 
 Mathematician, would dare to attempt it proves 
 the absurdity of believing, that, if unequal weights 
 are placed in a pair of scales, the heavier will pre- 
 ponderate. *Thus, let X be equal to 10, depressing 
 the scale A ; Y= 10, depressing the scale B, each 
 weight acting unopposed. Then let the two 
 weights be placed, one in each scale, we shall then 
 have, according to your notation, X Y=O ^O, 
 no preponderance being produced. Then, let one 
 of the weights be diminished by ^ or ~, we be- 
 
159 
 
 lieve, that the other scale will preponderate. This 
 belief your argument proves to be an absurdity, as 
 great, as to believe, that X 21 =X. So then, if 
 
 M 
 
 you place ten pounds in each scale, and then take 
 two pounds from either of them, to believe, that the 
 other scale will preponderate, is to believe, that 10 
 10= ; but that 10 8=10 Here you are in a 
 dilemma. You must either deny the preponder- 
 ance of the heavier scale, or abandon your argu- 
 ment, as a palpable fallacy. There is no medium : 
 and you may choose either alternative. It is in- 
 deed, a thaumaturgic demonstration, which proves 
 a known fact to be impossible, and the belief of it, 
 an absurdity. 
 
 I think it necessary to add, as you seem 
 desirous of information, that when I use the term 
 promptitude, I have no allusion to the execution, 
 but merely to the alacrity, or ehearfulness, with 
 which the offer is accepted. Truth also compels 
 me to add, that, whether Hume, or Priestley have, 
 or have not, adverted to the distinction between 
 the mere overt act, and the ehearfulness, with which 
 it is undertaken, I perceive no merit whatever, in 
 your mode of reasoning. Be assured, Sir, if my 
 conviction were otherwise, I could have no rational 
 motive to dissemble it. 4 The pride of victory shall 
 never induce me in any question, much less in a 
 question of such moment as this, to disguise, or to 
 conceal, my real sentiments. 
 
160 
 
 I proceed now to examine your argument, pre- 
 sented to us in a form somewhat different, but still 
 involving the same error. It is, in truth, the self- 
 same argument, vamped up in a somewhat different 
 shape, and is again and again repeated in the Es- 
 say. The porter is now offered a hundred guineas 
 for travelling ten miles East, and an equal sum for 
 travelling the same distance West, the force of 
 which motives are expressed by X and Y. No 
 action takes place. An additional motive Z n: 
 ^ is offered, which produces a preference, and 
 the porter obeys the greater motive. 
 
 6 
 
 8 
 
 Yr=100z 
 XirlOOz 
 
 X-Y=:O 
 
 Y+z-Y=X+z 
 
 Y=0 
 
 X=O 
 
 lOOzO 
 
 Q. E. D. 
 
 This I believe to be a faithful transcript of your 
 Algebraic demonstration, that the doctrine of Ne- 
 cessity is false, as maintaining, that the additional 
 motive Z will beget a preference, and the conse- 
 quent action. If I have omitted a jot or tittle, not 
 even the Q. E. D. or adided any thing, I am not 
 
161 
 
 aware of it. The same formula, then, the same ar- 
 gument, if we substitute weights for motives, and 
 preponderance for preference, goes evidently to 
 prove a fact to be an impossibility, and the belief of 
 it, an absurdity. If you should reply, that your 
 argument regards the full effect, that the action 
 results as completely, as if its motive had been 
 unopposed, whereas the momentum of the greater i* 
 diminished by that of the less weight, it is answered, 
 that in your Essay, #nd in your letter also, you re- 
 peatedly declare, the mere overt act, and not any of 
 the accessory circumstances, such as promptitude, 
 alacrity, &c. to be the object 6f your attention. 
 This being the case y I am justified, as I conceive, 
 in applying your demonstration to the simple fact of 
 preponderance, without regarding the momentum, 
 as either greater or less : and I have shewn, that it 
 disproves too much, and therefore disproves no- 
 thing. But let us view it again as a scientific ar- 
 gument. You are pleased to dignify it with the 
 name of a Mathematical Demonstration ; and you 
 fail not to impress on my attention, that my ar- 
 guments, though you acknowlege their ingenuity, 
 are wholly incapable of resisting the " brunt" of 
 your " rigid mode of reasoning." 
 
 Now, Sir, demonstration, you well know, is 
 a chain of axioms, or of truths resolvable into de- 
 finitions, or axioms. Every step, in the progress of 
 the argument, is a necessary consequence of some 
 
162 
 
 preceding step, and attended, either mediately or 
 immediately, with all the intuitive certainty of a 
 self-evident truth. 
 
 When first we inspect this argument of yours, 
 we are irresistibly inclined to augur most favour- 
 ably of its character, presented as it is in a shape 
 so truly scientific. We perceive A A and B B, and 
 X X and Y Y, with + and and = all arranged with 
 the imposing formality of Mathematical precision. 
 We startle at the idea of controverting an argu- 
 ment, which appears clothed in all the certainty 
 of scientific demonstration. For, if Mathematical 
 evidence do not 'produce conviction, where shall 
 we find it ? But frontis nullajides, is at all times a 
 prudent maxim. Let us, therefore, inspect the 
 demonstration a little more narrowly. The first 
 equation X= Y expresses a supposition. Your se- 
 cond Y^IOOZ likewise expresses' a supposition. 
 Your third is a deduction from the first and se- 
 cond. Your fourth is a necessary inference from 
 the first. Now we come to the fifth equation ; 
 and what have we here ? How do we arrive at this 
 step ? Does the proposition express any axiom, or 
 self-evident truth ? No. Is it a legitimate deduc- 
 tion from any of the preceding equations ? No. 
 Is it a necessary inference from any proposition 
 previously demonstrated ? No. Is it the expression 
 of an acknowleged fact ? No. Is it a datum admit- 
 ted by your opponents ? No. What then is it ? 
 
163 
 
 Where have you found it ? Or, how comes it here? 
 These are questions for you to answer. The two 
 first propositions, are mere suppositions ; the third 
 is resolvable into a supposition, so likewise is the 
 fourth ; the fifth is a naked affirmation ; and thus 
 ends your Mathematical Demonstration. 
 
 You are pleased, indeed, gratuitously to inform 
 us, that your fifth equation, if such it can be named, 
 expresses accurately the necessary result of the 
 opposition of unequal motives, according to the 
 doctrine of Necessity, with the modification already 
 specified, that the strongest motives alone have 
 effect, as if unopposed. But is this assertion to be 
 received as proof? I have asked, and I ask again, 
 from which of the preceding propositions is your 
 fifth deduced ? If it be no deduction, and if Ma- 
 thematical demonstration be a chain of necessary in- 
 ferences, by what perversion of language is a mere 
 assertion to be called demonstration ? You inform 
 me, that the ablest Mathematicians in Scotland, 
 and the most zealous Necessarians of your ac- 
 quaintance, some of whom are good Mathema- 
 ticians, can find no error in your short argument, 
 and seem surprised, if not indignant, that I should 
 presume to attack it boldly. I do certainly venture 
 to attack it boldly, and have no hesitation in affirm- 
 ing, that it possesses nothing, but the semblance, 
 the vain form, of Mathematical demonstration. I 
 could produce some of the highest Mathematical 
 
164 
 
 authorities in this country, perfectly concurring in 
 my opinion. But, Sir; all this is idle and ridicu- 
 lous gossip. Neither the question itself, nor the 
 merit of your argument, can be determined by au- 
 thority. Reason, and this only, can decide the 
 point. Besides, there is really something inexpres- 
 sibly ludicrous, in referring your pretended demon- 
 stration to the examination of eminent Mathemati- 
 cians. To ask their opinion in a question, involv- 
 ing the simple operations of addition and subtrac- 
 tion, is like taking a sledge hammer to break an 
 egg, or the club of Hercules to brain a gnat. 
 
 It may be observed farther, that the question be- 
 longs not to the province of the Mathematician, 
 nor is it to be determined by the most profound 
 Mathematical science. It is a question in Meta- 
 physics, to the examination of which, therefore, 
 the mere Mathematician is wholly incompetent. 
 
 Having now, it is hoped, fully exposed the fal- 
 lacy of your argument, and having shewn that 
 your demonstration possesses not the shadow of 
 a claim to that dignified appellation, I shall dis- 
 miss, for the present, this part of the subject, with 
 one remark. It is, doubtless, your intention to 
 affirm, that your fifth equation accurately expresses 
 an absurdity, resulting from our hypothesis. In 
 this you err : for we neither maintain such jua ab- 
 surdity; nor is it deducible from our doctrine. 
 We admit, that if 100/. are opposed to the same 
 
165 
 
 sum, as uncombinable opponent motives, there 
 can be no preference, other circumstances being 
 equal, and therefore no action; and we believe, 
 that one pound added to either motive will pro- 
 duce a preference, and turn the scale : but is this 
 equivalent to affirming, that one pound is equal to 
 100/. or to 101/. ? We deny this, as we deny also, 
 that the force of the greater motive, as an incentive 
 to action, is weakened by the less, which your no- 
 tation would imply. Nor can we conceive a more 
 ridiculous sophism, than to tell the burgess, that, 
 because he was offered by A 100/. for his vote, and 
 by B 101 /., which latter sum he accepted, he had 
 received only one pound; for that 101/. 100/.= 
 to one pound. I repeat, that we deny the motive 
 to be weakened, as an incentive to action. Your 
 argument therefore proceeds on an assumption de- 
 nied by Necessarians, as it is repugnant to fact. 
 In all cases, where opponent uncombinable mo- 
 tives are concerned, there are two different voli- 
 tions, which, with their motives, it is necessary to 
 distinguish ; 1st. the motive, and the volition to 
 act; and 2d. the motive, and the volition to 
 prefer. The motive to act may be sufficiently 
 strong to produce action, where there exists no 
 motive to prefer. If your porter, for example, had 
 two new guineas presented to him, either of which 
 he might take as a gift, the motive to accept would 
 
166 
 
 would not be lessened by the value of the other. 
 The motive to accept therefore cannot possibly be 
 expressed by X Y=O ; but, while he was pon- 
 dering, which he should prefer, and while his in- 
 clinations were equally balanced, the equilibrium 
 may be properly denoted by this expression. To 
 destroy this equilibrium, the least conceivable mo- 
 tive would suffice. He might take one in prefer- 
 ence to the other because it accidentally first 
 caught his eye, because it lay the more conve- 
 nient to his hand, because it had the obverse pre- 
 sented to him ; in short, various causes or motives, 
 how whimsical soever, might produce a preference. 
 Now as X Y=O correctly expresses no prepon- 
 derance, or the equilibrium of equal weights in op- 
 posite scales, so the same expression will accu- 
 rately denote no determination, or the equilibra- 
 tion of the mind, antecedently to its volition to 
 choose. And, as the smallest weight, added to 
 either scale, will make it preponderate ; so the 
 smallest additional motive, real or conceived, will 
 produce a preference. These simple facts may, 
 agreeably to your notation, be expressed thus : 
 
 X Y=0^ 
 
 +*=* 
 
 N i\ 
 
 It is evident then, that, when you assume, that 
 
 X +*=*= P, or Preference. 
 
 N i\ 
 
strength, as incentives to action, and express this 
 by X Y, you assume a position contrary to fact, 
 and denied by Necessarians. It is evident also, 
 that, if your notion is correct, in regard to opponent 
 uncombinable motives, and your expression XY 
 applicable to them, it is an absolute contradiction 
 to suppose, that your notion and expression can 
 be correct, in respect to counteracting uncombinable 
 motives, between which, you yourself acknowlege, 
 there exists as great a differenee, as between plus 
 and minus. Yet to the latter of these only, as I 
 now proceed to shew, is your notation applicable. 
 Previously, however, let it be understood, that,, 
 agreeably to our hypothesis, the agent always acts 
 in. obedience to the strongest motive, or the motive 
 which appears to him to be the strongest, and 
 that a certain degree of strength of motive is neces- 
 sary to produce volition, and its consequent ac- 
 tion, just as a certain physical force is required to 
 conquer the inertia of matter and to generate mo- 
 lion. 
 
 I shall suppose, that your porter will carry a 
 parcel ten miles for five shillings,, and not for less. 
 A person, unacquainted with the hire, with which 
 the porter would be satisfied, offers him ten shil- 
 lings for this service. The porter will, of course, 
 undertake the journey, and with a degree of 
 promptitude and alacrity proportioned to the 
 unusually high remuneration. I shall suppose* 
 
168 
 
 however, that he is apprised, that, in performing 
 this journey, he must incur the extraordinary ex- 
 pence of two shillings, no matter in what way- 
 The strength of the motive is weakened ; he will 
 still, however, accept the offer ; for the balance is 
 a powerful motive ; and he will act in obedience 
 to it. Let us suppose, that he is informed, if he 
 undertake the service, that he must incur the 
 extraordinary expence of four^ shillings ; still he 
 will engage cheerfully to perform the journey. 
 Nay, though he should foresee the certain extraor- 
 dinary expence of five shillings, there will still re- 
 main a balance, sufficient to produce the desired 
 effect. If he were to foresee the expence of eight 
 shillings, he would decline the service. These 
 suppositions and results may, in your Algebraic 
 formula, be thus expressed : 
 
 X=5;EA By supposition 
 
 X+5= 1(A A. fortiori 
 X+5 '2=8EiA A. fortiori also 
 X+5 4=6EiA Afortiori 
 X+5 5 =5^ A By supposition 
 X-f 5 8=2ER or Refusal. 
 Thus it is evident, that a given motive, though 
 powerful enough to produce, if unopposed, a given 
 action, may be so far weakened by a counteracting 
 motive, as to become an insufficient stimulus to 
 excite to action. Thus also, it is evident, that all 
 counteracting motives, or those mutually destruc- 
 
169 
 
 tive, in whole or in part, resolve themselves into 
 one simple motive ; for the expressions, on the left- 
 hand side, are equivalent to the simple motives, 10, 
 8,6, 5, 2. To these cases, and to these only, therefore 
 is your notation applicable ; and if the difference be- 
 tween these and opponent uncombinable motives, be, 
 as you yourself admit, as great and as obvious, as 
 between plus and minus quantities, it follows, as a 
 necessary consequence, that, if your notation be 
 applicable, and your notion correct, in respect to 
 counteracting uncombinable motives, as I admit to 
 be true, your notion must be false, and your nota- 
 tion inapplicable, in regard to motives opponent and 
 uncombinable. Yet to these latter only is your 
 notation applied. The cases, which you propose 
 in p. 45 of your Letter, now naturally present 
 themselves. 
 
 If a man were offered fifty pounds for a horse, 
 and were assured, that he should lose as much, a& 
 soon as he had received the fifty pounds, you ask me, 
 if I believe, that, in such circumstances, he would 
 part with his horse. For noticing this, and seve- 
 ral other questions equally idle and unimportant, 
 I feel, that some apology is due to the reader. 
 But, if I should omit them, I might subject my- 
 self to the charge of suppressing Dr. Gregory's 
 learned illustrations, and his pertinent, profound 
 queries. It is answered then, that I am persuad- 
 ed, he would not accept the offer; because 50 
 
170 
 
 50z:O. You are of the same opinion. But here, 
 Sir, two queries naturally present themselves. If 
 your notation X YnO be applicable here, as it 
 evidently is, how can it be applicable to those 
 cases, to which you have confined it, in your 
 Algebraic argument, I mean, cases of opponent 
 uncombinable motives ? Is there not as great a 
 difference between these two classes of motives, as 
 between plus and minus quantities ? Let it not be 
 answered, that our hypothesis implies the posi- 
 tions, which you ascribe to us. We disclaim 
 them. We admit that X Y expresses no pre- 
 ference ; but we deny that it expresses the strength 
 of the motive, except in cases of counteracting 
 motives, as has been just now shewn. 2dly. If there 
 be a self-determining power, which can will without 
 a motive, which can prefer without a motive, where 
 the motives are equal ; nay where the motives are un- 
 equal, can prefer the weaker to the stronger ; why 
 may not this same power, by its own arbitrary voli- 
 tion, impel the man to sell the horse? Pray favour me 
 with an answer to this question, without involving 
 the contradiction, that this self-governing power is 
 at the same time governed by motives, or implying 
 a middle hypothesis, which, as shall be shewn 
 afterwards, is, if possible, still more absurd. 
 
 You ask, if I think he would sell him, if an 
 additional shilling, or even a guinea of purchase- 
 money were offered, and still fifty pounds, but no 
 
171 
 
 more, were taken from him ; and I answer in the- 
 negative. You ask next, if I think he would sell 
 him, if, in addition to the original fifty, he were of- 
 fered fifty pounds more, or any sum equivalent to 
 the value of the horse. I answer in the affirma- 
 tive, consistently with the principles which have 
 been just now illustrated. You ask, if I do not 
 think a corresponding result would take place, 
 in similar circumstances, in the worthy burgess 
 selling his vote, or the great proprietor selling his 
 estate. In answer, I observe, that, in all such 
 cases, no energy, no action can take place, unless 
 when the motive, remaining after the original mo- 
 tive has been diminished, by the strength of the 
 counteracting motive, is singly a sufficient motive 
 to action. One pound might possibly induce the 
 burgess to sell his vote ; but one guinea could be 
 no equivalent to the proprietor for his estate. 
 Your suppositions may be thus expressed : 
 
 XzzSO 
 
 Y=50 
 
 X 50^A By supp. 
 
 X-Y-OER 
 
 X Y -}~ TtF^Tfc^ R 
 
 By supp. 
 
 Having thus replied to your queries, too trifling 
 and too unimportant in every other respect, than 
 as serving to evince the applicability of your ex- 
 
172 
 
 pression X Y to counteracting uncombinable 
 motives, to which you have not applied it, and its 
 manifest inapplicability to opponent uncombinable 
 motives, to which you have applied it ; I con- 
 clude my examination of your boasted argument, 
 with expressing my conviction, that every intelli- 
 gent reader must perceive it to be wholly falla- 
 cious and inconclusive. The grounds, on which 
 I reject it, are these three. 1st. It proves too 
 much : it proves, that the preponderance of the 
 greater of two weights in a pair of scales, is im- 
 possible, and that to believe it is an absurdity. It 
 therefore proves nothing. 2dly. It proceeds on 
 a false assumption, and is therefore radically 
 vicious. It presumes, that of two opponent un- 
 combinable motives, one is weakened by the other, 
 as an incitement to action; a presumption repug- 
 nant to fact, as it is contrary likewise to the doc- 
 trine of necessity, confounding, at the same time, 
 opponent with counteracting uncombinable mo- 
 tives, things as distinct, as plus and minus quanti- 
 ties, or as profit and profit on one side, and profit 
 and loss on the other. 3dly. While it professes 
 to be a Mathematical demonstration, it violates the 
 very essence of all mathematical evidence ; which 
 consists of a chain of necessary truths and their 
 necessary consequences. Its conclusion X Y+ 
 J^=X is a mere affirmation; it is deduced from 
 neither of the premises : it is no necessary infe- 
 
1 73 
 
 rence no inference whatever, a gratis dictum? 
 and nothing else. In another form of your argu- 
 ment we have in like manner the gratuitous asser- 
 tionX+Z Y^X+Z, expressingno intuitive truth, 
 no acknowleged datum, no necessary deduction ; 
 but, on the contrary, directly contradictory to the 
 preceding propositions. Never, I am persuaded, 
 were the forms of scientific reasoning so egregious- 
 ly prostituted ; never was there exhibited a more 
 palpable violation of the acknowleged principles 
 of Mathematical evidence. 
 
 Before I finally dismiss the subject, I take the 
 liberty to subjoin one observation. I am not in- 
 clined to carp at trifles, nor to magnify every tri- 
 vial error into a matter of superlative importance ; 
 much less am I disposed to lay a mighty stress 
 on points, which do not essentially affect the ques- 
 tion. It is my desire rather to direct the attention 
 to the main argument, disdaining captious objec- 
 tions, and fruitless logomachies. But, as you 
 value yourself highly on your Mathematical preci- 
 sion, and particularly on your skill in Algebraic 
 analysis, kindly ascribing the presumed errors of 
 your opponents to their unacquaintance with the 
 forms and principles of Mathesis ; it will be pardon- 
 ed, I trust, if I take the liberty to ask, by what 
 axiom (for every step in Algebraic analysis must 
 be founded in some axiom) does your eighth equa- 
 tion, in the following investigation, proceed from 
 
174 
 
 Y^IOOZ 
 
 7 
 8 
 
 Surely, if equal quantities are subtracted from 
 equal quantities, or if X+Z be subtracted from 
 both sides of the equation, there remains not, as you 
 state, Y~O, but Y=:O. 
 
 I am far from offering this observation, as in 
 the least degree affecting the question ; but when 
 there is exhibited such a parade of Mathematical 
 demonstration, and when scientific precision is so 
 ostentatiously affected, an illegitimate deduction, 
 so palpable as this, admits, I conceive, no excuse. 
 
 I have a few observations to offer in answer to 
 the remainder of your Letter. 
 
 Whether you be, or be not, the original of that 
 distinction between the mere turn of the balance, 
 and the full effect of the greater weight, is of no 
 importance to the subject in question. But as you 
 ask my opinion, I will tell you frankly, that the 
 distinction is such, as, in my apprehension, could 
 escape no person of common penetration ; that it 
 was* not new to me, nor to several other Necessa- 
 rians, with whom I had conversed on the subject 
 
175 
 
 of this controversy; and that the merit of originality, 
 were it exclusively your own, is, in my opinion, 
 not worth claiming. From the solemnity of man- 
 ner, in which you introduce the subject, the air of 
 importance, in which you invest it, and the very 
 serious call to declare my sentiments, whether I 
 believe the idea to be yours, one would naturally 
 infer, that, instead of being a matter of compara- 
 tive insignificance, *it was a palmary argument, 
 decisive of the controversy. 
 
 You say, " From the ease and freedom, with 
 " which you avail yourself of that observation, 
 " which I had the vanity to think originally my 
 " own, and from the gross terms of reproach and 
 " contempt, in which you revile me for my sup- 
 " posed ignorance of those things, which I had 
 " stated the most strongly and explicitly, it may 
 4t be presumed, that the observation was quite 
 " familiar to you." 
 
 How far this charge of grossly reproaching and 
 reviling you is well or ill founded, and how far my 
 animadversions are just or unjust, can be ascer- 
 tained only by a comparison of that part of your 
 Essay witji my answer, as it respects the illustra- 
 tion by the example of the balance. The former 
 of these questions may be determined by inspect- 
 ing the language; the latter must be decided by 
 examining the arguments. Into the truth of your 
 charge I shall now briefly enquire. Whether its 
 
176 
 
 refutation will be complete, when the passages 
 are submitted to. the examination of the reader, it 
 would be presumption in me to anticipate. But 
 in candour, I feel it incumbent on me to acknow- 
 lege, that, indignant, as every liberal and honest 
 mind must be, at the contumelious sneers against 
 your opponents and their arguments, with which 
 your Essay abounds, the reproachful imputations, 
 which you have laboured to fasten on them as 
 philosophers, with the ungenerous and offensive 
 charges of deliberate falsehood, and consummate 
 hypocrisy, which you have alleged against their 
 characters as men,- indignant, I say, at this 
 conduct, I may have expressed my sentiments of 
 your Essay, with more asperity of language, and 
 with more of a sarcastic spirit, than the incredibi- 
 lity of your charges would warrant, or the tem- 
 perate genius of Philosophy would justify. The 
 proud and lofty tone also, in which you boast of 
 your argument as invincible, and as consigning 
 your opponents to defeat and disgrace, may have 
 drawn forth a few contemptuous and derisive 
 remarks, which some readers may disapprove, 
 but which few or none of those, who are acquaint- 
 ed with your controversial productions, will be 
 disposed harshly to condemn. 
 
 You endeavour to prove, that there is a differ- 
 ence, nay an infinite difference, between the tuni 
 of a balance and the effect of physical causes: you 
 
J77 
 
 do not, however, attempt to explain, wherein the 
 difference consists, between the turn of a balance, 
 and the determination of the will. You acknow- 
 lege it very difficult to express it in words ; but 
 affirm, that it must be obvious to the apprehen- 
 sion of the most vulgar, and most unlearned. 
 
 I answer in my Essay (p. 393), " If this differ- 
 " ence be so palpably evident, as to force itself on 
 " the conviction of the most obtuse understanding, 
 " it is somewhat surprising that the Essayist, who 
 " seems nowise deficient in words, should be 
 " unable either to define, or to describe it." I 
 then ask, if this be one of your demonstrations. 
 This may be called contemptuous, or it may be 
 sarcastical ; but are these " gross terms of re- 
 " proach f 
 
 I have asked, " must we renounce the hypothe- 
 " sis of necessity, because the vulgar disbelieve it? 
 " Nay, must we be pronounced unreasonable, 
 " because we will not assent to their decision 
 " without argument, or acknowlege the difference 
 " in question, on his or their affirmation, a differ- 
 " ence too, which he himself has not attempted to 
 " define ? In short, must we believe, merely be- 
 " cause Dr. Gregory believes ? Such arguments 
 " as these (meaning, arguments of mere authority) 
 " may be justly considered as suited only to the 
 " Nursery or the Vatican." 
 
 I have said (p. 413) that " the questions, which 
 Let. M 
 
178 
 
 <; you would propose to the porter concerning the 
 " balance, are precisely such, as a Necessarian 
 " would put, in order to prove his own hypothesis ; 
 " how, they make for his (the Essayist's) theory I 
 " am at a loss to conceive." I add " The illus- 
 " tration, which the Essayist employs is truly un- 
 " worthy of the smallest notice, and betrays an 
 " unpardonable ignorance of the question." I 
 have also said in a Note (p. 392), " Thy demon- 
 " strations are weighed in the balance, and found 
 " wanting." These are all the passages, in my 
 Essay, which I have been able to discover in re- 
 gard to the balance. With what propriety these 
 observations can be considered as couched in gross 
 terms of reviling and reproach, I must leave to the 
 judgment of the reader to determine. To his 
 decision I shall bow with submission. 
 
 I shall only add, that the severest reproach 
 against you, on the subject of the balance may be 
 extracted from your own Essay. It is that passage, 
 in which you insinuate, what you elsewhere boldly 
 and explicitly proclaim, I mean, the charge of 
 disingenuity and falsehood against those, who pro- 
 fess to believe the doctrine of Necessity a charge 
 not more illiberal towards us, than degrading to 
 yourself. No man, Sir, can read that passage, 
 without condemning the narrow and intemperate 
 spirit, which could indite an imputation, so rude 
 and offensive. To stigmatise us, as knaves and 
 
179 
 
 hypocrites, because we will not acknowlege the 
 force of your arguments, or the falsity of our own 
 hypothesis, shocks every generous and honest feel- 
 ing, and is to you surely an indelible reproach. 
 Yet, Sir, though you introduce this rude insinua 
 tion, when treating of the balance, I dismissed it 
 without animadversion. 
 
 I have now carefully re-examined the subject, as 
 a matter of argument, and I solemnly declare (I 
 hope you will believe me) that I have found 
 nothing in your letter, which can confirm your 
 reasoning or invalidate my refutation On the con- 
 trary, my conviction, that your demonstration ie 
 completely fallacious, has been strengthened by 
 this re-examination. 
 
 In regard to the manner, in which I have treated 
 your Essay, I shall only observe, that the proud 
 and ostentatious display of mathematical demon- 
 stration, the vanity, the arrogance, and the illiber- 
 ality, which pervade the work, the unbecoming 
 sneers at Necessarians and their opinions, with 
 the ungenerous charge of mala fates, urged too in 
 a manner the most ungracious and offensive, equally 
 unworthy of the gentleman and the philosopher^ 
 appeared to me then, as they appear now, to merit 
 the severest correction. Your parade of mathe- 
 matical demonstration I treat sometimes with gra- 
 vity, and sometimes with ridicule. Your frequent 
 attempts at humour and raillery can produce in 
 
180 
 
 your readers, but one sentiment, and one feeling. 
 That the temper and spirit of your Essay merits 
 reprehension, no candid reader, I am confident, 
 will deny. And it is that spirit, and that temper, 
 against which chiefly my strictures are directed : 
 and not against your argument, though this also 
 demands and receives correction. But enough on 
 this subject for the present : on some future oc- 
 casion I may be compelled to resume it. 
 
 This answer you have my permission to submit 
 to any friend of yours, whom you may think a 
 competent judge of the question, while I reserve 
 to myself the liberty to present it to the public in 
 its present state, or with additions and alterations, 
 as circumstances may require. 
 
 I am, Sir, 
 
 Your most obedient Servant, 
 
 ALEX*. CROMBIE. 
 
 Dated Jirst at Highgate, 10th Jan. 1804, now 
 at Greenwich, 1 3th Jan. 1819. 
 
FROM DR. GREGORY. 
 
 LETTER II. 
 SIR, 
 
 IN my former letter, I mentioned that I should 
 wish to put some questions to you, concerning 
 your principles of reasoning, and the mode of ar- 
 gument, which you have adopted, in order to con- 
 fute my supposed demonstration. The principles 
 which you have tacitly assumed, and the mode which 
 you have openly followed, for that purpose, appear 
 to me not only strange and wonderful, but directly 
 repugnant to the best known principles if Logic, and 
 to the uniform practice of Mathematicians. 
 
 I own I have not imagination enough, ever to 
 have thought of such a mode of answering a strict 
 argumentum ad absurdum : but if any person of a 
 more lively imagination had suggested to me such 
 a mode of reasoning, as barely supposeable, though 
 hardly possible ; or if you yourself had sent me a 
 copy of your argument, fairly printed and ready for 
 publication, and asked my opinion of it, I should 
 have declared, without hesitation, that it would be 
 highly gratifying to me to see it published ; and 
 that I should consider it as a complete proof and 
 
182 
 
 illustration of all that I had said unfavourably of 
 Necessitarians, either in point of reasoning or can- 
 dour, of probity or of veracity. At the same time, 
 I should have thought myself bound, if you had 
 put that confidence in me, to tell you explicitly what 
 I conceived to be the defects and the errors of your 
 mode of reasoning. You might then have judged 
 for yourself, whether it would be right for you to 
 publish an argument liable to such objections ; or 
 whether those objections appeared to you of such 
 weight, as to require any animadversion or 
 answer. 
 
 It is now too late to think of those things : bu^ 
 it is not too late to give you an opportunity of 
 judging of the force of the objections which I mean 
 to urge against your argument ; and of preventing 
 me from doing any injustice to you, or to your 
 mode of reasoning. 
 
 I shall tell you frankly, that I do not expect, or 
 think it possible, that we shall agree, either in our 
 ultimate conclusions, or as to certain principles of 
 reasoning which you have tacitly assumed. The 
 difference between us, on those points, seems fun- 
 damental and irreeoncileable ; but it is at least 
 easy, by an analysis of your argument, and by 
 your answers to a few precise questions which I 
 mean to put to you, to ascertain exactly on what 
 points we differ, and on what principles our very 
 different opinions are founded . When this is done, 
 
183 
 
 every man of science and candour will be enabled 
 to judge, with ease and certainty, whether you or 
 I are in the right. This decisive judgment, not your 
 conversion, is the object of my answer to you. 
 
 As a very needful preliminary to that work, and 
 even to the few precise questions that I mean to 
 put to you, I beg you will say, What you conceive 
 to be the nature and force of an argumtntum ad ab- 
 surdum ? What do you conceive to be essential to 
 the validity of such an argument ? What do you 
 conceive would be a valid objection to such an ar- 
 gument, or a refutation of it, if it were erroneous ? 
 More particularly Do you conceive that it is any 
 defect in it, or any valid objection to it, that those 
 inferences are false and absurd, and already known 
 to be so, which the person giving the demonstra- 
 tion deduces with much care and pains, often by a 
 long chain of reasoning, from that supposition 
 
 which he undertook to disprove? Are you 
 
 aware, that it is essential to a valid demonstration ad 
 absurdum, that the inferences deduced from the 
 supposition assumed, shall be notoriously false or 
 absurd ? and that they are expressly given as such ? 
 Are you aware, that if those inferences, shewn to 
 be necessary consequences of the supposition as- 
 sumed, were true, they would afford a proof that 
 that supposition was true, which the person rea- 
 soning maintained to be false, and undertook to 
 disprove ? -Are you aware, that it is only the 
 
184 
 
 proposition contradictory to the one assumed, 
 which the person reasoning undertakes to establish 
 as a truth ? 
 
 As it is of the utmost consequence that we 
 should fully understand one another, however much 
 we may differ, on all these points, T hope you will 
 not think it unreasonable in me to beg of you to 
 illustrate, by one or two good examples, what you 
 conceive to be a valid demonstration ad absurdum; 
 were it only that you may have an opportunity of 
 judging for yourself, by comparing mine with it, 
 whether mine agree with it in every essential particu- 
 lar ; or, if not, of pointing out what is the peculia- 
 rity, the defect, or the error of mine. I am sure 
 you will find, that, in both, a supposition is assu- 
 med in order to be disproved, by shewing that its 
 necessary consequences are false or absurd ; and 
 that such disproving of the supposition assumed is 
 conceived to be a complete proof, or demonstration, 
 of the proposition contradictory to it. Neither in 
 my argument, nor in the numberless demonstrations 
 of the same kind employed by geometers, will 
 you find any attempt to prove, or maintain as truths, 
 any of those inferences which are shewn to be 
 necessary consequences of the supposition assumed; 
 but on the contrary, the most explicit declaration, 
 that those inferences are notoriously false in point 
 of fact ; and that they are given as such. 
 
 You can be at no loss to find abundance of good 
 
185 
 
 instances of demonstrations ad abmrdum in the wri- 
 tings of geometers. It is a mode of reasoning, 
 which, from necessity, they have found themselves 
 often obliged to employ; and which both geo- 
 meters and logicians have uniformly acknowleged 
 to be just as valid as a direct demonstration. 
 
 Though any demonstration ad absurdum, to be 
 found in the writings of mathematicians, will serve 
 the purpose which at present I have in view, yet I 
 think it would be peculiarly proper, in order to 
 make the analogy between the examples taken 
 from their writings and my demonstration as per- 
 fect and striking as possible, to choose some of 
 their propositions, in which the thing to be ulti- 
 mately proved appears intuitively (I mean at first 
 sight) to be false or impossible ; and in which con- 
 sequently the supposition assumed, in order to be 
 disproved, by shewing that its necessary consequen- 
 ces are false or absurd, appears at first sight a self- 
 evident truth. I presume you, and all orthodox 
 Necessitarians, will admit that the proposition 
 which I undertake to demonstrate (1 mean the 
 self-governing power of man) is false at least, if 
 not absurd and impossible ; and that the contra- 
 dictory proposition (I mean the want of self-go- 
 verning power in man, and the absolute irresistible 
 force of motives, as well as of physical causes) is 
 almost a self-evident truth ; or at least is, bonajide, 
 believed by all who hold the true Necessitarian 
 
186 
 
 faith. The particular purpose of such illustrations 
 as I suggest to you, is to shew that an argument 
 adfalsum et absurdum is valid and conclusive, even 
 against such propositions as inaccurate thinking, 
 observing, or reasoning, may lead men to regard 
 as unquestionable truths. 
 
 Take, as an example of this kind, the compli- 
 cated proposition, comprehending two different 
 suppositions, that the circumference of one circle 
 can touch that of another in one point only, whe- 
 ther it be inwardly or outwardly. A person un- 
 used to strict mathematical reasoning would na- 
 turally suppose that circles might touch one ano- 
 ther, either inwardly or outwardly, along a consi- 
 derable part of their circumferences ; and that this 
 extent of their mutual contact would be greater or 
 less, according to the size of the circles, and their 
 proportion to one another : and if such a person 
 should endeavour to ascertain or illustrate the point 
 in question, by drawing representations of circles of 
 different sizes, and observing how they touched one 
 another, inwardly or outwardly ; he would think 
 that he had the evidence of his own senses for that 
 proposition which is disproved, implying that the 
 proposition contradictory to it is proved, by a short 
 and easy deductio adfalsum. 
 
 Take, as another instance, a case still stronger ; 
 a proposition which seems directly contrary both tc* 
 the evidence of our senses* and to common sense ; 
 
187 
 
 which yet may be completely established by a de- 
 monstration ad absurdum. It is proved, that an 
 hyperbola, and the right line formed by the inter- 
 section of its plane with a plane touching the sur- 
 face of the cone along the right line, where it is 
 cut by a plane passing through its vertex, must ap- 
 proach to one another. This point being esta- 
 blished, a person unused to strict reasoning would 
 immediately suppose that they must at last meet ; 
 and would consider this as a corollary, or a neces- 
 sary consequence of the former proposition, and 
 as a self-evident truth. Yet it is easily shewn, by 
 an argument ad absurdum, that the supposed self- 
 evident and necessary truth is false and impossible ; 
 and that the hyperbola and the right line in ques- 
 tion, though always coming nearer to one another, 
 and coming nearer than any assignable distance, 
 never can touch, though they should both be pro- 
 tracted ad infinitum. The simple and obvious con- 
 sideration, that if ever they did meet, the point of 
 their contact must be both in the plane touching 
 the cone, where it is cut by the vertical plane, and 
 in the surface of the cone itself, where it is cut by a 
 plane parallel to the vertical plane, is a proof of 
 that impossibility of their ever meeting. Would 
 you conceive this evident impossibility, implied as 
 a necessary consequence in the assumed supposi- 
 tion, that the hyperbola and its asymptote should 
 meet, to be any defect or error in that demonstra- 
 
188 
 
 tion ad f ahum ? or do you perceive any error irr 
 it ? or can you specify any supposeable defect or 
 error which should vitiate that or any similar de- 
 monstration? If so, will you state it precisely, that 
 we may see whether there be any such defect or 
 error in my demonstration. Or do you admit 
 that demonstration of the hyperbola and its asymp- 
 tote never meeting to be valid, and a complete 
 proof, that the supposed self-evident proposition, that 
 those two lines must meet at last, because they 
 were necessarily approaching to one another, is 
 false and impossible ? 
 
 If you know of any pseudo-demonstration or so- 
 phism in the form of an argumentum ad absurdum, 
 the fallacy of which you can detect, I wish you 
 would state it, with your detection and refutation 
 of it, in order to illustrate your mode of answering 
 my argument. If your answer be rational and 
 valid, as you profess to think it, such a parallel 
 instance will not onl y explain, but confirm and establish 
 your mode of reasoning. On the other hand, if 
 your mode of analysing and answering my argu- 
 ment be sophistical and disingenuous, which I think 
 it is, such an illustration will make even you per- 
 ceive and understand the weakness of your own 
 reasoning, and preclude all disputes about it. It 
 would be in vain to desire you to look for such a 
 sophism among the infinite number of propositions 
 which geometers have demonstrated by the argu- 
 
189 
 
 mentum ad absurdum : but some ingenious sophists 
 and sceptics have amused themselves, by giving 
 pretended demonstrations ad absurdum of proposi- 
 tions notoriously false. The best of these that I 
 can remember at present, is the sophism, (attribu- 
 ted to ZENO, but on what authority I know not,) 
 that two right lines inclined and approaching to 
 one another never can meet, though protracted ad 
 injinitum. If you do not know the proposition, 
 and the pseudo-demonstration of it, leading to the 
 necessary consequence, that one side of a triangle 
 would be equal to the other two, which is impos- 
 sible, your friend MR. PATERSON, I dare say, 
 can help you out. It would be an useful and 
 wholesome exercise to you, to endeavour to point 
 out the difference between that notorious sophism 
 and the valid demonstration with respect to the 
 hyperbola and its asymptote. In both, the argu- 
 mentum ad absurdum is employed; in both, the 
 proposition to be demonstrated appears at first 
 sight absurd and impossible; nay, the absurdity 
 and impossibility appear, at first sight, to be the 
 same in both : in both, the contradictory proposition, 
 assumed in order to be disproved, by shewing that 
 it implies by necessary consequences an inference 
 which is certainly impossible, appears, at first 
 sight, a self-evident truth : and lastly, in both 
 these arguments, the inference given as a necessary 
 consequence of the supposition assumed in order 
 
190 
 
 to be disproved, is false and impossible. Consider 
 then wherein consists the difference between the 
 valid demonstration relative to the hyperbola and 
 its asymptote, and the sophism with respect to the 
 two right lines. Wherein can it consist, but in the 
 chain of reasoning, which is very short in both, 
 but in the one is, and in the other is not, a series 
 of strictly necessary consequences. 
 
 There are some other preliminaries or general 
 principles of reasoning, about which I should wish 
 to come to a right understanding with you ; and 
 at least to know precisely your opinion : or, in 
 other and plainer words, to know whether you 
 have erred from ignorance and inadvertency, not 
 having read or attended to the very plain and 
 strong cautions, which I have stated in my Essay, 
 on those points to which I allude; or whether you 
 have duly considered them, and think them irra- 
 tional, and unworthy of regard in conducting, or 
 in answering, an argument ad absurdum ; or, lastly, 
 whether your conduct has proceeded from the 
 most wilful and systematic disingenuity, in pre- 
 tending to argue in defiance of the most familiar 
 and best established principles of reasoning, and 
 in a manner which, if it were rational, or could be 
 done bond Jide, would equally enable you, or any 
 person who chose to employ it, to refute not only 
 my argument, but every dilemma, and every argu- 
 ment ad absurdum, that ever was or ever can be 
 
^contrived by logicians or by geometers. If you will 
 take the trouble to look into my Essay, page 226. 
 line 25. to the end, and the whole of page 227. 
 and also page 244. and 245. you will see what 
 strong reasons there are for adopting the last and 
 most unfavourable of these suppositions ; reasons 
 absolutely irresistible, unless you shall choose for 
 yourself, and establish by competent proof, one 
 or other of the two preceding and more favourable 
 suppositions with respect to your own conduct. 
 You cannot now pretend to overlook, or not to 
 have known of, those cautions which I suggested, 
 and those laws of reasoning to which I allude. If 
 you think them wrong, and wish to set them aside, 
 it is surely incumbent on you to assign your rea- 
 sons for holding such a singular opinion, in defiance 
 of the precepts and the uniform practice of all who 
 have either taught or practised strict reasoning by 
 means of the dilemma and the argument ad ab- 
 surdum. 
 
 Do you think it rational or candid, in tracing 
 the necessary consequences of one supposition, for 
 example, that of constant conjunction, to assume 
 and blend with it a very different supposition ; for 
 example, the notion of " that for the sake of which ;" 
 and sometimes to consider the consequences of the 
 one, sometimes those of the other supposition? 
 If the object of a train of reasoning be to shew 
 that those two notions or suppositions, though 
 
702 
 
 similar in some respects, and in several cases 
 implying the same consequences, are yet, in other 
 respects, widely different, and, in numberless cases, 
 imply totally different consequences; which in 
 fact is the purpose of my argument ; is it a rational 
 or even a candid answer to any demonstration of a 
 necessary consequence following from the one 
 supposition, to say or to shew that it is not a ne- 
 cessary consequence of the other supposition ? The 
 supposition of constant conjunction is certainly 
 very different from the supposition of " that for 
 " the sake of which," but yet not more different 
 than the supposition of " that for the sake of 
 " which" is from the supposition of constant con- 
 junction. If a person, reasoning on the supposi- 
 tion of " that for the sake of which? should point 
 out clearly what the consequence would be in any 
 supposeable case ; for example, that my porter 
 (page 226.) would go in the direction A B, and 
 not in the direction AC or AD, or in any other 
 direction ; would it not be very absurd, and un- 
 candid, to say, in answer to that mode of reason- 
 ing, that he would not go in the direction A B or 
 A C, but must go in the direction A D ; because 
 if he did not go in this direction, one or other of 
 the two motives applied would have no effect in 
 point of overt action; which is contrary to the 
 supposition of constant conjunction? Would it 
 not be a fair reply to such an argument, if the 
 
193 
 
 person reasoning should say, that he had nothing 
 to do with the supposition of constant conjunction, 
 and was considering only the consequences of 
 " that for the sake of which ?" If so, what reply 
 should be given to a person who, in answer to an 
 argument tracing the necessary consequences of 
 constant conjunction, should maintain that those 
 consequences were not just inferences from this 
 principle, because they did not correspond to the 
 notion of " that for the salte. of which ?" 
 
 When these preliminaries are settled, which you 
 may observe are equivalent to fixing the general 
 principles, or the law, according to which the 
 merit or demerit of my argument must be decided, 
 it will be easy to determine what is to be thought 
 both of my Essay and of your mode of analysing 
 and answering it. 
 
 Let. N 
 
REPLY TO DR. GREGORY'S 
 
 SECOND LETTER. 
 
 SIR, 
 
 JL OUR second letter is introduced with a few pre- 
 liminary questions. You ask what I conceive to be 
 the nature, and force of an argumentum ad absur- 
 dam ; what I conceive to be essential to the validi- 
 ty of such an argument; and what I conceive 
 would be a valid objection to such an argument, 
 or a refutation of it, if it were erroneous. To 
 these queries, and to the misconception, in which 
 they seem to have originated, I have already had 
 occasion to advert : I will now answer them, and 
 as I proceed, illustrate my observations, by apply- 
 ing them to your argument, though much of this 
 subject has been already anticipated. 
 
 A deductio ad absurdum is that species of argu- 
 ment, by which we either prove a proposition to be 
 false, by shewing that its necessary consequences 
 are false, or that a proposition is true, by demon- 
 strating that its contrary involves an absurdity. 
 To the validity of this argument, as to every other 
 kind of demonstrative reasoning, it is essential that 
 
195 
 
 it consist of a chain of axioms, or their necessary 
 consequences. This may suffice, as a general 
 answer to your first and second general questions. 
 I proceed to the third, in answer to which I observe 
 that a deductio ad absurdum may be invalidated, by 
 shewing, 1st. That the principle, in which the 
 argument is founded, is false ; or 2dly. By shew- 
 ing, that the argumentative process is vicious ; or 
 3dly. That it disproves too much, and therefore 
 disproves nothing. 
 
 1st. The deductio ad. absurdum may be invalida 
 ted by shewing, that the principle, in which it is 
 founded, is false. You contend, for example, 
 that, if the doctrine of necessity be true, as imply- 
 ing a principle of Constant Conjunction between 
 motive and action, the porter, under the influence 
 of the two motives, must describe the diagonal. 
 This argument proceeds on the false assumption, 
 that, because two physical forces, acting indirectly 
 on brute matter, impel or attract it, in the line of 
 the diagonal, two uncombinable motives acting in 
 indirect opposition, on an intelligent being, placed 
 in the circumstances of your porter, must impel 
 him also in the diagonal, if the principle of Con- 
 stant Conjunction obtain between motive and ac- 
 tion. This assumption is false, and the argument 
 founded on it, fallacious. 
 
 Where the motives are combinable, as anger 
 moderated by affection, courage attempered with 
 
196 
 
 prudence, hope mingled with fear, the effect will 
 necessarily be of a mixt nature, according to our 
 hypothesis, and may not improperly be repre- 
 sented by the diagonal of your parallelogram. 
 But in the case supposed, it is an error to assume, 
 that, if a principle of Constant Conjunction exist 
 between motive and action, the effect of the two 
 motives on the mind of the porter must be identi- 
 cal with the effect of two physical forces acting 
 on a physical substance. 
 
 The second horn of your dilemma implies ano- 
 ther, and equally egregious, misconception of the 
 doctrine of Constant Conjunction. To the truth 
 of this dcctrine it is not necessary, that the same 
 agent, whether physical, or intellectual, shall uni- 
 formly produce one and the same effect, the result 
 depending on the subject on which, and the cir- 
 cumstances, wherein they operate. So far in re- 
 spect to your dilemma. 
 
 Your Algebraic deductio assumes a false princi- 
 ple, which radically viciates the whole argument. 
 It proceeds on the assumption, that in cases of 
 two opponent uncombinable motives^ the expres- 
 sion X -Y=O clearly and correctly denotes the 
 power, or impulse, by which the agent is prompt- 
 ed to act. This assumption has been shewn to 
 be false ; and the argument founded on it there- 
 fore fallacious. 
 
 2dly. The deductio ad absurdum may be invali- 
 
197 
 
 dated by shewing, that the argumentative process 
 is vicious. In every step it is required, that the 
 proposition there stated, be a necessary inference 
 from some one or other of the preceding proposi- 
 tions, or from some proposition previously demon- 
 strated. Your deductio ad absurdum is invalidated 
 by the introduction of a proposition, which is no 
 inference from any preceding proposition no ac- 
 knowleged datum, no intuitive truth, and is directly 
 contradictory to the antecedent equations. 
 
 Where you find your conclusion in your " short 
 " and simple argument," it exceeds, I apprehend, 
 all human sagacity to divine. Explain to us, I 
 intreat you, how it is deduced from either of the 
 other two propositions. If you cannot shew, that 
 it results necessarily from one of the premises, you 
 must either abandon the argument as fallacious, 
 or convince us, that Mathematical demonstration 
 is any thing, but a series, or chain, of necessary 
 truths. To ascribe an opinion to your opponents 
 is surely not a demonstration of the absurdity of 
 that opinion ; nor does scientific evidence admit 
 gratuitous propositions, as a medium of argument. 
 Two premises and no deduction you call a simple 
 demonstration. Euclid certainly knew nothing of 
 such deductiones ad absurdum. A demonstration, 
 terminating in an affirmation, deduced from none 
 of the premises, is like one of the ten command- 
 
198 
 
 ments, tacked to a proposition in Euclid, with an 
 ergo, " Thou shalt not commit adultery ;" " Thou 
 shalt not steal." Q. E. D. 
 
 3dly. The deductio ad absurdum may be invali- 
 dated by shewing that it disproves too much. 
 Your argument, which is intended to demonstrate, 
 that there is an absurdity in believing, that the 
 greater of two opponent uncombinable motives 
 will produce the action to which it prompts, would 
 demonstrate also, that there is an absurdity in 
 believing, that the greater of two weights in a pair 
 of scales will preponderate. My reasoning here 
 you seem completely to have misunderstood ; and 
 labouring under this misconception, you have with 
 an equal degree of inconsistency and rudeness, 
 charged me, at one time, with incapacity to com- 
 prehend your argument, at another time, with 
 only affecting to misunderstand it, and then again 
 have represented me, as displaying dexterity in 
 evading it. A little attention to the manner in 
 which your argument is retorted, by its application 
 to the balance, would have saved the necessity of 
 your several queries. 
 
 You are condescending enough to inform me, 
 that I shall have no difficulty in finding abun- 
 dance of good examples of deductio ad absurdum, 
 in the writings of geometers. Of this fact I have 
 the fullest conviction ; but I confidently affirm, 
 
199 
 
 that no example, similar to yours, is to be found 
 in the productions of any geometer, ancient or 
 modern. 
 
 You proceed to offer to my attention one or two 
 examples of deductio ad absurdum ; and, if I should 
 not be acquainted with the sophism of Zeno, you 
 kindly recommend the assistance of Mr. Paterson, 
 whom you are pleased to call my friend. This is 
 too mysterious for me to comprehend. The friend- 
 ship of that gentleman I possibly may possess, 
 though in course of nearly thirty years, we have 
 never met under the same roof above ten or twelve 
 times. Of his abilities, as a Mathematician, I know 
 nothing ; but of this I am sure, that he has too 
 much sagacity to pervert the forms, or outrage the 
 principles, of Mathematical science. 
 
 You desire me to consider, wherein consists the 
 difference between the valid demonstration, rela- 
 tive to the hyperbola and its assymptote, and the 
 sophism with respect to the right lines ; and you 
 ask, wherein can it consist, but in the chain of 
 reasoning, which is very short in both ; but in the 
 one is, and the other is not, a series of strictly ne- 
 cessary consequences. The difference does con- 
 sist in this ; and with such an example before you, 
 it is truly surprising, you did not perceive, that, 
 while you were describing the distinction between 
 a valid demonstration, in which there is a chain of 
 reasoning, and a paralogistic argument, in which 
 
200 
 
 there is not, you were clearly stating the difference 
 between demonstrative proof, and your deductio ad 
 absurdum. 
 
 You ask, if I think it " rational or candid, in 
 " tracing the necessary consequences of one sup- 
 " position, for example, that of Constant Conjunc- 
 " tion, to assume and blend with it a very different 
 " supposition ; for example, the notion of c that 
 " for the sake of which,' and sometimes the conse- 
 " quences of the one, sometimes those of the other." 
 
 To blend two distinct questions in any discus- 
 sion, necessarily creates perplexity, and not unfre- 
 quently leads into error ; nor do I hesitate to ac- 
 knowlege, that this mode of treating an argument, 
 whether it proceed from a dark and entangled in- 
 tellect, or from a deliberate intention to perplex 
 and confound, will not be adopted by any person, 
 who possesses penetration to discover truth, or ho- 
 nesty enough to avow his convictions. No man, 
 who has sagacity to discern the point in question, 
 and whose object is not to defeat an adversary, 
 will either load a question with extraneous matter, 
 or confound distinctions, which should be rigo- 
 rously observed. 
 
 But your question, it is pretty evident, conveys 
 no obscure insinuation, that I have treated your 
 reasoning in this manner, and that an investigation, 
 founded in the true principles, and conducted in 
 the genuine spirit, of philosophy, has, thr ought ig- 
 
201 
 
 norance or design, been perplexed and evaded in 
 my Essay. To a charge, whether direct, or ob- 
 lique, unsubstantiated by a tittle of evidence, a ne- 
 gation of its truth may claim to be regarded as a 
 sufficient reply. But, conscious as I am, that I 
 have studied to exhibit your argument, as it really 
 is, and, by the strictest and fairest principles of 
 reasoning, to expose its fallacy, I cannot content 
 myself with a bare denial of your insinuated 
 charge. I will, therefore, briefly state the general 
 scope of your argument, and of my answer, refer- 
 ring to our Essays, as the only evidence, to which 
 we can appeal, in corroboration of the accuracy of 
 my statement. 
 
 It is the aim of your work to shew, that there is 
 " something widely different" between the relation 
 of cause to effect, and that of motive to action. 
 With this view you profess to trace the consequen- 
 ces of physical forces, acting on a physical sub- 
 ject, and of motives, analogous to these forces, ad- 
 dressed to an intelligent agent. I follow you 
 closely in this investigation ; and the scope of my 
 answer is to shew, that, though the consequences, 
 in both cases, are not identical, but extremely dif- 
 ferent, as far as the first horn of your dilemma is 
 concerned, you are not justified in inferring, that 
 motive and action do not bear the same relation to 
 each other, as cause and effect : and I have ex- 
 
202 
 
 posed the error, which pervades this part of you*' 
 argument. In answer to the second horn of your 
 dilemma, I have shewn, that your notion of one 
 and the same motive being associated uniformly 
 with one and the same action as proper to it, is er- 
 roneous, and that the existence of such association 
 is not necessary to the truth of our hypothesis. I 
 have here shewn likewise, that no other separation 
 takes place between a given motive and a given 
 action, than is to be observed in physics, between a 
 given agent and a given effect, the result in both 
 cases depending not on the motive only, nor on the 
 physical agent only, but on the subjects on which, 
 and the circumstances, wherein they operate. 
 
 This is the general scope of my answer ; and 
 in conducting the argument, I have no where 
 mixed the two suppositions, to which you refer. 
 Their consequences I have examined distinctly 
 and separately ; by confounding them, I should 
 have entangled, and not simplified, my reasoning. 
 " If the object," you say, " of a train of reasoning be 
 " to shew, that those two notions, or suppositions, 
 " though similar in some respects, and in several in- 
 " stances implying the same consequences, are yet, 
 "in other respects, widely different, and in number- 
 " less cases implying totally different consequences, 
 " which, in fact, is the purpose of my argument, is it 
 " a rational, or even candid answer, to any demon- 
 " stration of a necessary consequence, following 
 
203 
 
 " from one supposition, to say, that it is not a ne- 
 " cessary consequence of the other supposition T 
 
 The candour of such an answer may for the pre- 
 sent be safely dismissed from our consideration. 
 Neither its presence, nor its absence, is concerned 
 in the supposed reply. The irrelevancy, and the 
 irrationality of such an answer I am ready to ac- 
 knowlege. If it bear, indeed, on the question in 
 any respect whatever, it tends rather to strengthen, 
 than to weaken, the argument of an adversary. 
 But to a person maintaining that, if motive have 
 the same relation to action, as cause to effect, the 
 application of motives to an intelligent agent, 
 must have the same effect, as the application of 
 physical forces to a physical agent, to such a per- 
 son it would be a sufficient refutation of his ar- 
 gument to shew, or rather to remind him of the 
 fact, that neither necessity of operation nor the 
 principle of Constant Conjunction implies identity 
 of result. You trace the necessary consequences 
 of the application of two physical forces You 
 consider next the application of two motives ; and 
 you infer, that, if the doctrine of Necessity, 
 as implying the principle of Constant Conjunction, 
 be true, the motives must produce the same effect 
 with the physical forces. I admit the diversity of 
 effect, acknowleging that the consequences] of 
 both suppositions are not the same ; but have I 
 ever offered this concession as an answer to your 
 argument? lacknowlege this necessary consequence 
 
204 
 
 of the one supposition respecting the physical 
 forces, but have I offered it, as a refutation of your 
 argument, that the same necessary consequence 
 does not follow from the application of the two 
 motives ? By no means. But I have contended 
 for this position, that the consequence of the mo- 
 tives may be necessary, though the porter does not 
 describe the diagonal. From difference of result 
 you infer difference of relation ; for on any other 
 supposition your argument has no intelligible ob- 
 ject. I contend on the contrary, that this differ- 
 ence can no more disprove Constant Conjunction 
 between motive and action, or evince, that the 
 consequences of the motives are not necessary, 
 than two different effects from two different phy- 
 sical causes can prove, that either the one, or the 
 other, effect is not necessary. And, when I ex- 
 amine the other horn of your dilemma, namely, 
 that, if he does not travel in the diagonal, one of 
 the motives, contrary to the doctrine of Constant 
 Conjunction is separated from its proper action, I 
 shew, that, as the principle of Constant Conjunction 
 does not require, that the same physical force, 
 on whatever subject, or in whatever circum- 
 stances, it may act, shall produce uniformly 
 the same effect, so this principle does not require, 
 that the same external motive, to whatever mind, 
 and in whatever circumstances it may be present- 
 ed shall produce one and the same action. I 
 have here shewn that your argument proceeds on a 
 
205 
 
 misconception of what the principle of Constant 
 Conjunction implies and I have shewn likewise, 
 that no other separation takes place between an 
 external motive, and a given action, than takes 
 place, in the case, which I have stated in respect 
 to the balance. But nowhere, I repeat, whether 
 examining the first, or the second horn, of your di- 
 lemma, have I offered so unmeaning an observa- 
 tion, so irrelevant an answer, as that the necessary 
 consequences of your first supposition are not true^ 
 because they are not^he necessary consequences of 
 the second. 
 
 You say, " The supposition of Constant Con- 
 junction is certainly very different from that for 
 " the sake of which ; but yet not more different than 
 " that for the sake of' which is from the supposition of 
 " Constant Conjunction.'" Is there any man, versed 
 in the common principles of the dialectic art, is 
 there a philosopher, a rhetorician, or metaphy- 
 sician, to whatever school or sect he may belong, 
 who will not acknowlege that this sentiment is lo- 
 gically conceived and concisely expressed ? A is 
 not more different from B, than B is from A, is truly 
 a curious and novel mode of stating a plain propo- 
 sition. I have always understood that the differ- 
 ence between A and B is the same, as the difference 
 between B and A. Profoundly conversant as you 
 are in Algebraic Notation, you will doubtless be 
 able to explain the difference between A - B and 
 
206 
 
 B~ A. No person, I well know, can make such 
 nice distinctions as Dr. Gregory ; and no person 
 can more easily fill a page, and with so little ex- 
 pence of thought. 
 
 But, for the sake of information, permit me' to 
 ask you as a Logician and Metaphysician (for 
 Metaphysics, you say, is your amusement), how 
 do you compare, so as to ascertain the points of 
 resemblance and dissimilarity between things 
 completely disparate, having no one common ac- 
 cident, quality or property? Hudibras was a 
 great Mathematician, and also profoundly skilled 
 in Metaphysics. His maxim was 
 
 " A just comparison still is 
 " Of things ejusdem generis" 
 
 How do you compare " Constant Conjunction" 
 with " that for the sake of which ;" an abstract 
 principle, an idea of pure intellection, with a 
 motive, a guinea, for example, a thing \vhether 
 considered, as the object of desire, or the desire 
 itself, having a real existence ? This I really do 
 not understand. I can conceive the relation be- 
 tween cause and effect, as comparable to the re- 
 lation between motive and action; and I can 
 conceive the connection between the two former 
 as capable of being compared with that, which 
 subsists, whatever be its character, between the 
 two latter. I can conceive a moving power im- 
 pelling a physical body, as comparable to a 
 
207 
 
 motive stimulating, and impelling the human mind. 
 But, how the abstract principle of Constant Con- 
 junction, a purely mental association, can be com- 
 pared with an external object, the porters guinea 
 for example, I cannot comprehend. Honestly 
 confessing my ignorance, I will thankfully receive 
 your information. Cur prave pudens nescire quam 
 discere malo ? 
 
 If the things compared be so essentially and 
 entirely dissimilar, that they have not one common 
 point of resemblance, we cannot sufficiently admire 
 the profundity, as well as the value of your obser- 
 vation, viz. that the things differ from each 
 other nay, that the one does not more differ from 
 the other, than that other does from it. 
 
 You proceed ; " If a person reasoning on the 
 " supposition of that for the sake of which should 
 " point out clearly, what the consequences would 
 " be in any supposable case, for example, that my 
 " porter would go in the direction A B, and not 
 " in the direction A C or A D, or in any other 
 " direction, would it not be very absurd and un- 
 " candid to say, that he would not go in the 
 " direction A B or A C, but must go in the di- 
 " rection A D, because, if he did not go in that 
 " direction, one or other of the two motives applied 
 " would have no effect in point of overt action, 
 " which is contrary to the supposition of constant 
 " conjunction? Would it not be a fair reply to 
 
208 
 
 " such an argument, if the person reasoning should 
 " say, that he had nothing to do with constant 
 " conjunction, and was considering only the con- 
 " sequences of that for the sake of which ?" 
 
 It is an easy thing for an author to deceive him- 
 self with indefinite and half-formed conceptions, 
 fancying, that he thoroughly understands, what is 
 really unintelligible, on any supposition, but the 
 falsehood of his own hypothesis. The first consi- 
 deration, that presents itself on reading this pas.- 
 sage is, that the principle of your supposition is 
 irreconcileable with your own theory. By reason- 
 ing on the supposition of that for the sake of which, 
 you must mean, reasoning on the supposition, of 
 a motive being applied to some intelligent agent : 
 for you say, that the proper and natural notion of 
 motive is, that for the sake of which. Now I am 
 at a loss to conceive, if motives have no determin- 
 ate and necessary effect on human volition, but 
 are either obeyed, on disobeyed, whatever may be 
 their absolute or relative strength, just as the self- 
 determining will pleases, I am at a loss, I say, 
 to conceive, how you or any man can reason con- 
 cerning their effect, or how it is possible for you, 
 or any person, to point out clearly, that your 
 porter, if he be like any other porter, would travel 
 in the direction A B. I am as incapable of con- 
 ceiving this, as I am of imagining, how any person 
 could ascertain, whether the greater or the less 
 
209 
 
 weight would preponderate, if the tongue of the 
 balance, like an independent and arbitrary will, 
 possessed the power of giving the preponderance 
 to either of the two weights. If the tongue of the 
 balance can make either the weight A, or the 
 weight B preponderate, the greater against the 
 less, or the less against the greater, how could 
 any human being clearly foresee the result ? And, 
 if the will can determine the volition either in 
 favour of this, or of that motive, I want much to 
 know, by what guide, what principle, you can 
 trace, and clearly prove, the consequence of the 
 application of two motives, nay how can you> 
 anticipate the result, with even the lowest degree 
 of moral certainty ? From what premises is your 
 deduction to be drawn? In what principle is 
 your reasoning founded ? By what train of ar- 
 gument do you arrive at your conclusion? Do 
 you refer to experience? You proceed on the 
 presumption, that, what has happened in regard 
 to motive and action, will in similar circumstances 
 happen again, and thus admit the principle of 
 Constant Conjunction. If the basis of your reason- 
 ing be not experience, I entreat you explicitly to 
 say, what it is, for I confess, that I am exceedingly 
 desirous to know it. Tell us, how you reason, 
 and how you reach your conclusion. You have 
 admitted a supposition, which no human sagacity 
 can reconcile with your own theory. You have 
 Let. O 
 
210 
 
 acknowleged a process to be practicable, which is 
 totally impracticable on any hypothesis but that of 
 Necessity. Men may deceive themselves by ambi- 
 guous terms, and half formed theories, but every 
 attempt to anticipate the conduct of others in given 
 circumstances, is a virtual acknowledgement of the 
 truth of Necessity, It is vain it is idle in the 
 extreme, to tell us, ^that you do not deny the 
 influence of motives. It is as absurd, as to say, 
 that you do not deny the influence of weights in a 
 pair of scales, and yet maintain the self-determin- 
 ing power of the tongue of the balance. But let 
 us dismiss this inconsistency, and return to the 
 question. 
 
 We shall suppose, that your reasoner, by some 
 inexplicable and inconceivable process, shall clearly 
 shew, that your porter will travel in the direction 
 A B, it would be neither pertinent, nor true, for 
 an opponent to return this answer, that the con- 
 clusion was false, being contrary to the doctrine 
 of Constant Conjunction; but, that in obedience to 
 the two motives combined, he must go in the di- 
 rection of the diagonal. This answer, I say, 
 would be neither pertinent, nor just. In the first 
 place, it would be irrelevant ; for, if the doctrine 
 of Constant Conjunction, in respect to the relation 
 of motive and action, were in dispute, and if it 
 were possible (as for the sake of argument, I shall 
 suppose it to be) to trace the consequence of any 
 
211 
 
 motive, or motives, without admitting this doctrine, 
 the other might with great propriety reply, that he 
 had nothing to do with the doctrine of Constant 
 Conjunction. 
 
 But the answer would not be merely irrelevant ; 
 it would also be false, betraying an ignorance, 
 in the respondent, of the very principle, for which 
 he professed to contend. For, if he concluded, 
 that because two physical forces, acting at right 
 angles to each other, might combine their power, 
 and impel a physical substance in the direction of 
 the diagonal, the two motives, addressed to the 
 porter, would also, according to the doctrine of 
 Constant Conjunction, impel him in the same direc- 
 tion, it would furnish the strongest possible evidence, 
 that he had yet to learn, what the doctrine of Con- 
 stant Conjunction means. 
 
 If so, you ask, " what reply should be given 
 " to a person, who,, in answer to an argument, 
 " tracing the necessary consequences of Constant 
 " Conjunction, should maintain, that those conse- 
 " quences are not just inferences, from this principle, 
 " because they did not correspond to the notion 
 " of* that, for the sake of which'" I answer, that 
 the reply might, with propriety be, that the answer 
 was neither relevant, nor just. If you, or any 
 other philosopher, mathematician, or metaphysi- 
 cian, in order to illustrate the doctrine of Constant 
 Conjunction, should demonstrate, that a body im- 
 
212 
 
 pelled by two indirect forces would describe the 
 diagonal A D, and if I, or any other person, not 
 being conversant in Newton s Principia, Bacon's 
 Novum Organum, Euclid's Demonstrations, or Alge- 
 braic Analysis, and not having in our possession 
 your Instrument a mentis, or any knowlege of 
 your demonstration, should deny this proposition, 
 because the porter, addressed by the two motives, 
 does not describe the diagonal, you might justly 
 reply, that you had nothing to do with motives, 
 and that you were tracing the principle of Con- 
 stant Conjunction, as exhibited in the application 
 of two physical forces to a physical substance. If 
 you yourself had duly attended to this distinction, 
 and not confounded the laws of matter, with the 
 laws of mind Constant Conjunction, as mani- 
 fested in the physical, with the same principle, as 
 exhibited in the intellectual world, you would have 
 avoided those errors, with which your argument is 
 palpably chargeable. 
 
 Having now answered your queries, permit me 
 to ask, where have I questioned the effect of the 
 two physical forces, because it differs from the 
 effect^of the two motives ? Where have I denied, 
 or disputed the effect of the motives, because it 
 differs from the effect of the forces ? No where. 
 I have admitted both results ; but I have affirmed, 
 that both are equally necessary, and that the princi- 
 ple of Constant Conjunction equally obtains in both, 
 
213 
 
 If you argue, on the principle of Constant Con- 
 junction, from the effect of the two forces, to an 
 identity of effect from the application of the two 
 motives, I maintain, that you mistake the doc- 
 trine of Constant Conjunction, and reason from 
 false principles. Then I am warranted in object- 
 ing, that you confound mind with matter ; and 
 that you might with less absurdity infer an identity 
 of effect from the respective agencies of two dis- 
 similar physical causes, on two dissimilar physical 
 substances. I am warranted in replying, that the 
 porter can no more move in the diagonal, to which 
 he has no motive, than a physical body in a direc- 
 tion, to which it has no impulse. The physical 
 forces acting on the physical substance may be 
 combined into one force ; but intelligence pre- 
 cludes the possibility of the combination of the 
 two motives. 
 
 Having now replied to this passage in your 
 letter, which under the appearance of great can- 
 dour, and superlative accuracy, proceeds on a 
 misconception both of the doctrine of Constant 
 Conjunction, and of my reasoning, and which 
 exhibits one of those specious sophisms, which as 
 often deceive the author, as the reader, I shall 
 take this opportunity of examining again the 
 foundation of your whole argument: and I am 
 inclined to believe, that on reconsidering the basis 
 
214 
 
 of your demonstration, you yourself will acknow- 
 lege, that it is unsound and fallacious. 
 
 When we contemplate the physical creation 
 around us, we behold a system of astonishing 
 regularity. We find the whole of inanimate nature 
 governed by determinate laws, and the same ef- 
 fects uniformly resulting from the same causes. 
 Even those sudden and violent changes, which 
 are not conformable to the general order of the 
 system, we justly regard as under the government 
 of the same universal and fixed laws. If the 
 volcano, the earthquake, or the hurricane interrupt 
 the wonted harmony of nature, whatever difficulty 
 w r e may experience in investigating their causes, 
 we never doubt for a moment, that these irregulari- 
 ties and convulsions are generated by the opera- 
 tion of the same laws, by which the universe is 
 governed. It is the general regularity of nature, 
 with the persuasion that it will continue unchanged, 
 which gives value to experience. It is this, which 
 enables man to avert the threatened evil, and to 
 secure the distant good. Deprive him of this 
 persuasion, and you reduce him to a state of irre- 
 mediable blindness, and aggravated misery. It is 
 experience, combined with the firm persuasion, 
 that the same antecedent circumstances will 
 continue to produce the same effect, which ena- 
 bles man to render the powers of nature, or the 
 
215 
 
 agency of proximate causes, subservient to his 
 pleasures, his comforts, and his necessities. 
 
 In contemplating the operations of nature, the 
 most inattentive observer must remark a similarity 
 existing amongst certain phenomena: and it is 
 this similarity, which constitutes the ground of 
 that intellectual process, which is called generalisa- 
 tion. As in common language we assign to like 
 substances a general name, reducing them all 
 under one class, so to all similar phenomena, or 
 similar processes in nature, we give one common 
 appellation. We observe, for example, a stone, 
 dropped from the hand, fall to the ground. We 
 observe a variety of similar individual facts. We 
 observe, that all bodies have a tendency to the 
 centre of the earth. We say, this takes place by 
 the law of gravitation. But does this explain the 
 phenomena ? Does it unfold the cause, or eluci- 
 date the principle ? By no means. Gravitation, as 
 a scientific term, is a mere generic name, to ex- 
 press a universal fact, narnely, the tendency of all 
 bodies towards the earth, or to a common centre. 
 The term itself explains nothing ; it solves not the 
 phenomena, as it unfolds not the cause by which 
 this tendency, as an effect, is produced. We may 
 investigate the rule, or ratio, according to which 
 this tendency takes place, and we may call this 
 the law of gravitation ; but the whole of this pro- 
 cess amounts to nothing more, than a mere state- 
 
216 
 
 ment of a universal fact. The same observation 
 may be extended to all general scientific terms, as 
 vegetation, oxydation, animalisation, &c. ; they de- 
 note certain general facts, or processes, observable 
 in certain bodies in certain circumstances ; and 
 when we speak of the laws, by which these are go- 
 verned, we signify nothing more, than the mode, or 
 manner, in which they are produced. The law does 
 not determine the fact, but is deduced from its 
 existence. It is not statutory ; but declarative. 
 Let us prosecute the investigation of secondary 
 causes to the extreme limit, we must ultimately rest 
 on facts. Beyond these we cannot proceed. 
 When we attempt to philosophise by explaining 
 one class of facts by the supposition of another 
 fact, we indulge in hypothesis. Gravitation, or 
 the tendency of all bodies to a common centre, is a 
 fact ; but, when we ascribe this tendency either to 
 impulse, or to attraction, as its cause, we then 
 become mere theorists. Of the principle of causa- 
 tion, or how one phenomenon proceeds from ano- 
 ther, as its cause, we know nothing. Facts only 
 are the objects of our perception ; and philosophy 
 does nothing more, than classify these facts, 
 assign names to the several species, and investigate 
 the mode, or rule, according to which they are 
 severally produced. 
 
 In examining the operations of nature, we uni- 
 formly experience the same previous circumstances 
 
217 
 
 accompanied with the same effects ; and that this 
 connection between antecedents and consequents 
 v continue to exist, is one of those convictions, 
 of which it is difficult, if not impossible, to give 
 any satisfactory explanation. The infant and the 
 man are equally governed by its influence; the 
 association of the two phenomena, as constantly 
 conjoined, is equally observable in both : the only 
 difference seems to be, that the former is unable to 
 speculate on the principle, the latter resolves his 
 conviction into experience. But why we believe, 
 that the course of nature will be the same to- 
 morrow, as it is to-day, we cannot satisfactorily 
 explain. We can merely say, that our own ex- 
 perience, and the experience of all men attesting, 
 that the order of nature has been uniformly main- 
 tained, as it now is, there must be some cause for 
 this uniformity, either in nature itself, or the ordin- 
 ations of its author, which will continue to act. 
 This is the only ground of our belief. Yet my 
 conviction, that the three angles of a triangle are 
 equal to two right angles is not stronger, or at 
 least does not operate more powerfully on my mind, 
 than the persuasion, that the sun will rise to- 
 morrow, or that a stone dropped from the hand 
 will fall to the ground. For, though I am con- 
 vinced, that the first proposition must be true, and 
 cannot possibly be false, and that the two last 
 Convictions may possibly be disappointed, yet the 
 
218 
 
 evidence on which they rest, is so powerful, as try- 
 exclude all doubt, or suspicion of their certainty, 
 
 Now, while the Atheist believes, that the con- 
 nection between any two phenomena, related to- 
 gether as cause and effect,- is a necessary and 
 indissoluble connection, and that the properties 
 of matter are inseparable from its nature by any 
 power, and essentially belong to it, a sounder and 
 more cautious philosophy maintains, that all, which 
 on this subject we are strictly authorised to assert 
 is, the Constant Conjunction of the two pheno- 
 mena ; but that this conjunction is indissoluble 
 we have no right to presume. All, that we are 
 warranted to affirm is, that this connection has 
 uniformly existed, and will most probably continue 
 to exist : but that it must eternally endure is an 
 opinion, which reason does not justify, and true 
 philosophy disclaims. 
 
 This principle of Constant Conjunction you 
 appear to me egregiously to misunderstand ; and 
 to this radical error, the several fallacies, which 
 pervade your whole argument, are clearly ascrib- 
 able. I have observed, that our notion of Constant 
 Conjunction is founded in experience. How do 
 we learn, that bodies gravitate? By experience. 
 How do we learn the effects of caloric, of cold, of 
 oxygen, of nitrogen ? By experience. Now, permit 
 me to ask, does experience of Constant Conjunc- 
 tion in. one species of facts, furnish us with any in- 
 
219 
 
 formation, by which we may anticipate the con- 
 junction or the result in another species of facts? 
 Will our knowlege, that the magnet and iron 
 mutually attract, enable me to say a priori that 
 the magnet and gold will also mutually attract? 
 Will our knowlege, tjiat acids dissolve metals, or 
 that there exists between them a chemical affinity, 
 enable me to anticipate the effect of an acid on a 
 vegetable substance ? Because we find the electric 
 fluid excited by the friction of glass, can we infer, 
 that it will be excited also by the friction of iron, 
 or of ice ? The effects, in such cases, are knowable 
 in no possible way, but by observation, and expe- 
 riment. Each class of facts stands upon its own 
 ground. Each .species of phenomena, whether 
 physical or intellectual, is governed by laws, partly 
 general, and partly also peculiar to itself; and 
 certain antecedent circumstances are in all 
 uniformly conjoined with certain consequent 
 effects. But we cannot reason from any two phe- 
 nomena as constantly conjoined, to the effect, 
 which may be produced, where the agents, or the 
 subjects, or the actual circumstances are different. 
 There is an absurdity even in the supposition. 
 Abstract, or analogical reasoning is here wholly 
 inapplicable, and cannot fail to involve us in error 
 Experience is our only infallible guide : and on 
 her authority we may confidently rely. 
 
 As in the phenomena of the physical, so 
 
220 
 
 also in thoe of the intellectual world, the 
 conjunction or connection between certain an- 
 tecedent and consequent circumstances, can be 
 ascertained by experience, and by experience only. 
 To attempt to investigate a priori, or by analo- 
 gical reasoning, the effect of a given motive, applied 
 to the human will, would be equally preposterous, 
 with an attempt to anticipate the effect of any 
 physical cause, antecedently to all experiment, or 
 observation. Nothing but experience can direct 
 us to a just conclusion. And, though in specu- 
 lating on the effect of motives, we cannot antici- 
 pate the result with the same certainty as in the 
 operation of physical causes, because it is more 
 difficult to learn all the actual circumstances, we 
 are not to infer from our uncertainty in such cases 
 the uncertainty of their operation. The uncertainty 
 is merely subjective, as Logicians term it, and not 
 objective. The event, in physical cases, sometimes 
 disappoints our expectation ; we do not, however, 
 on this account, dispute the principle of Constant 
 Conjunction, as existing between the antecedents 
 and consequents ; we merely conclude, that some 
 circumstance eluded our observation, and pro- 
 duced a result, different from that, which we were 
 led to anticipate. And, if this disappointment 
 occurs more frequently, in moral, than in phy- 
 sical cases, it is not, because the operation of the 
 antecedent circumstances is less certain, or less 
 
221 
 
 necessary, but because we are less acquainted 
 with them. The wind changed, this morning, 
 from North to South, and in the evening, shifted 
 back to the North- West. We cannot explore the 
 cause of this, though we may generally know the 
 theory of wind ; but, though we know not the 
 actual, and proximate circumstances, which 
 produced this change, do we doubt, for a moment, 
 that it was effected by the necessary operation of 
 previous circumstances. If we have repeated a 
 chemical experiment a hundred times with one 
 and the same effect, and if, in the next trial, the 
 same result does not follow, do we doubt the ne- 
 cessary connection between the antecedent circum- 
 stances, and the former results ? We merely infer, 
 that some new circumstance has entered, which 
 has eluded our notice, and disappointed our 
 expectation. In like manner, we may be ignorant 
 of the motive, which may have prompted any indi- 
 vidual to deviate from his usual line of conduct ; 
 but we are not hence warranted to infer, that this 
 deviation was not necessarily conjoined with the 
 antecedent circumstances. 
 
 It has been observed, that the effect of motives, 
 as of physical causes, is to be learned only from 
 experience, and that to reason from the result in 
 any given case of cause and effect, to the result in 
 another case, where the subjects are wholly dissi- 
 milar, would betray the most palpable ignorance 
 
of the first principles of philosophical science. To 
 apply the principle of Constant Conjunction in 
 one set or class of phenomena, to determine the 
 result in a different class, or to infer identity of 
 consequents, where the antecedents are not iden- 
 tical, is an egregious misconception of what the 
 doctrine of Constant Conjunction means. Every 
 department of nature has its own peculiar laws ; 
 and hence every science has its own peculiar prin- 
 ciples. These laws, these principles must be 
 carefully distinguished. We should laugh at the 
 man, who as an ingenious writer observes, should 
 talk of the musical principles of physic, the medi- 
 cinal principles of the law, or the grammatical 
 principles of astronomy. What judgment then 
 shall we form of that person's metaphysical 
 sagacity, who confounds mind with matter, who 
 reasons from the effect of two physical forces on a 
 brute substance to an identity of effect from two 
 motives applied to the mind of an intelligent being, 
 and who ventures to affirm, that, if the principle of 
 Constant Conjunction exist between motive and 
 action, the two motives must produce one and the 
 same effect with the two physical forces? You 
 surely must know, that identity of effect is to be 
 anticipated in those cases only, in which the pre* 
 vious circumstances are precisely identical. Are 
 the antecedent circumstances, in the two supposi- 
 tions under consideration, the same, nay in any 
 
'223 
 
 respect identical ? Is a motive a physical force ? 
 Is the porter inanimate matter ? Are the agents 
 the same, or even reducible to the same species ? 
 The theory of motives, like every other theory, is 
 to be established only by experience and observa- 
 tion. Th^ effect of any given motive is not deduci- 
 ble a priori ; no physical fact can enable you to 
 infer it, nor will mathematical reasoning aid you 
 in the investigation. The theory of body will not 
 solve the phenomena of mind. 
 
 It has been asked, and I ask again, how do you 
 learn the effect of any physical cause ? Is it not by 
 experience? by an induction of facts? And will 
 the knowlege of the connection subsisting between 
 any two phenomena in any one department of the 
 physical world enable you to ascertain, without 
 experience, the conjunction, subsisting between two 
 other phenomena in a different department ? This 
 will not be affirmed. Is it not by experience, and 
 by a similar process of induction of generals from 
 particulars, that the effect of any moral or intel- 
 lectual agency is to be learned ? How is the effect 
 of love, or of hatred, of hope or of despair, of 
 kno\vlege or of ignorance, wisdom or folly to be 
 learned, but from experience? Would a perfect 
 acquaintance with all the physical causes and 
 effects, which have existed since the world was 
 made, enable you to anticipate with even the low- 
 est degree of probability, the effect, which may be 
 
224 
 
 produced by the predominance of any passion in 
 the human mind ? You have ascertained, I shall 
 suppose, the effect of two indirect forces acting on 
 a physical substance, and you know, that under 
 their agency it will describe the third side of a 
 triangle, of which the other two sides are described 
 by the body impelled by the two forces separately, 
 in the same time. You know nothing, I shall 
 suppose, of the effect of the two motives presented 
 to your porter, or of a greater and less motive pre- 
 sented to any man in similar circumstances. The 
 case, I shall suppose, is quite new- Would you 
 be justified in saying, that, if a principle of Constant 
 Conjunction obtains between motive and action, 
 as between cause and effect, the same consequence 
 must result from the application of the two motives, 
 as from the agency of the two forces ? Yet this is 
 a specimen of your rigorous mode of reasoning, of 
 which, you assure us, we cannot sustain the 
 brunt. If it be allowed that the effect of any 
 given agency, in one department of the natural- 
 world, will not enable you to anticipate -the effect 
 of a different agency, in a different department ; 
 much less, surely, can it enable you to anticipate 
 the effect of any moral or intellectual cause. This 
 can be learned, as all facts are, by experience, and 
 by that only. Produce facts then, or the testi- 
 mony of experience, to warrant your conclusion, 
 that the porter will describe the diagonal (for from 
 
225 
 
 facts, or experience only can a just conclusion be 
 drawn), and we will submit to your inference, that 
 according to the hypothesis of Necessity, as im- 
 plying the principle of Constant Conjunction, he 
 will travel in that direction. Prove, that though 
 the effect of every physical cause must be learned 
 by observation, the effect of motives may be as- 
 certained by analogy, without direct experience, 
 and we will then allow, that your inference, that 
 the porter will take the diagonal, may be just ; 
 or, if you can shew, that the uniform conjunction 
 of any agent and its effect in one department of 
 nature, will enable you to anticipate with certainty 
 the effect of a given agent in a different depart- 
 ment, and that the doctrine of Constant Conjunc- 
 tion implies this certainty, it will then also be 
 admitted, that your inference may be just, and that 
 the porter, under the influence of the two motives, 
 must take the diagonal. 
 
 But while it is an established truth, that the 
 effect of motives, like that of physical causes, is to 
 be learned by experience only ; and while we find 
 that, other circumstances being equal, the porter 
 uniformly prefers the greater motive, and that his 
 travelling in the direction A B, as an effect, is con- 
 stantly conjoined with the greater motive, as the 
 cause ; we have the same evidence, the same au- 
 thority for maintaining the existence of Constant 
 Conjunction between tfce motive and the action, in 
 
226 
 
 the same circum stances, as between any physical 
 cause and its effect. Prove, that he will sometimes 
 prefer the less to the greater motive, or resist both 
 motives, other circumstances remaining the same, 
 and you will then accomplish, what you have as 
 yet unsuccessfully attempted ; you will then 
 prove, something more than you intended to prove, 
 namely, that no connection subsists between mo- 
 tive and action. For I maintain, that between 
 motive and action there exists either a constant 
 and necessary connection, or no connection what- 
 ever. Contingent agency, or contingent effect, 
 absolutely considered, can have no existence : the 
 terms express nothing but our ignorance of the 
 cause. Whatever acts, must act necessarily. In 
 the same circumstances, it can produce no other 
 than one effect. Or, if you can shew, that the 
 doctrine of Constant Conjunction requires, that 
 one and the same physical agent shall uniformly 
 produce one and the same effect, whatever be the 
 subject on which, and the circumstances wherein, 
 it operates, then you may infer, that a principle of 
 Constant Conjunction does not exist between 
 motive and action ; because the porter, though he 
 may for many years have travelled Westward for 
 half a guinea per mile, will prefer a guinea for 
 travelling Southward. But until you have proved 
 this, and as long as the preference now mentioned 
 uniformly obtains, your argument must be rejected, 
 
227 
 
 as a mere fallacy, founded in a misconception 
 of what the doctrine of Constant Conjunction 
 means. 
 
 I am fully aware, that the error, which your 
 argument involves, is so egregious and palpable, 
 that you are at pains to disclaim it ; but it is not 
 the less true, that it is implied in your reasoning. 
 You set out with observing, that a body acted 
 upon by two physical forces, not directly contrary 
 tp each other, will describe the diagonal of a 
 parallelogram, of which the distances described 
 by the body in one and the same time, under the 
 agency of the two forces acting separately, form 
 the two adjacent sides. Then you suppose two 
 motives, one a guinea, and the other half a guinea 
 per mile, offered to a porter the former, if he will 
 travel in the direction A B, and the latter, if he will 
 go in the direc- A B 
 
 tion A C. You 
 contend, that if 
 the doctrine of 
 Necessity be true, 
 as implying a 
 
 principle of Con- C " D 
 
 stant Conjunction, " he will go in the diagonal 
 " A D, and that it is folly for him to make a pre- 
 " tence of thinking, and ridiculous to make any 
 " words about it, for go he must in that direction." 
 Nay, that this assertion of yours may neither be 
 
228 
 
 misunderstood nor forgotten, you emphatically 
 add, " And further, I say, that if the porter 
 "do not go in that direction, the doctrine in 
 " question must be false." Now, I must con- 
 fess myself utterly devoid of all discernment 
 and common sense, as well as ignorant of the 
 meaning of the plainest terms, if this argument 
 does not involve the very absurdity, which you 
 disclaim. You reason from the effect of two 
 physical forces on a physical body, to the effect of 
 the two motives addressed to the porter ; and con- 
 tend, that, if Constant Conjunction subsist be- 
 tween motive and action, the same effect will be 
 produced in both these cases. You might, with 
 much greater truth, maintain, that b'ecause the 
 chemical combination of two given liquids pro- 
 duces a tertium quid, partaking of the qualities 
 and properties of each, a similar combination of 
 two different liquids will, in every other case also, 
 produce a compound, resembling in its effects 
 each of the component parts. Your argument 
 then, it is evident, implies the very absurdity, 
 which you are anxious to disavow, and which I 
 have endeavoured to expose. That the doctrine of 
 Constant Conjunction warrants no such conclu- 
 sion, I have already shewn ; and I affirm, that no 
 person, who understands this doctrine, could 
 possibly institute such an argument. To reason, 
 on the principle of Constant Conjunction from the 
 
229 
 
 effect of the two physical forces, to the effect of 
 the two motives, is to confound matter with mind ; 
 and involves an error more egregious, than if you 
 argued from the effect of the vitriolic acid on iron 
 to an identity of effect from the agency of the 
 atmosphere on gold, or from results in music to 
 deductions in masonry. To employ a fact in 
 physics to ascertain a fact in mind, is to violate 
 the first principles of philosophical science. 
 
 I would now, before the subject is finally dis- 
 missed, impress on your attention this simple, but 
 important, observation, that the doctrine of Con- 
 stant Conjunction implies this principle, and this 
 only, that the same antecedents, both in the natural 
 and moral world, are uniformly conjoined with the 
 same consequents, which conjunction is knowable 
 by no other means, than by experience. But it is 
 an egregious misconception of it to suppose, as 
 your argument presumes, that this doctrine im- 
 plies, because the two physical forces combine 
 their operation, producing a certain effect, the two 
 motives shall combine their agency also, and pro- 
 duce an identical effect. This supposition in- 
 volves the error, which has been sufficiently ex- 
 posed, namely, that the effect of certain moral 
 antecedents, if constantly conjoined with certain 
 consequents, may be ascertained by analogy, with- 
 out the aid of positive and direct experience, and 
 that analogous causes, if Constant Conjunction 
 
230 
 
 obtain between antecedents and consequents, must 
 produce identical effects. 
 
 You say, that it was the observation of Dr. 
 Reid, with respect to the difference " between a 
 " living, and a dead horse, in certain supposable 
 " cases of motion, which suggested to you, your 
 " mode of reasoning in your Essay." That the 
 error, which viciates the whole of your argument, 
 should have escaped your penetration, may not 
 perhaps create surprise. That Dr. Reid should 
 conceive (if he did so conceive) this difference to 
 be an argument against Necessity, is indeed a sub- 
 ject of wonder. Would he have disputed, do 
 you suppose, the necessary effect of evidence on 
 human belief, because a demonstration of Euclid 
 does not produce the same effect on a living man, 
 and on a dead horse ? 
 
 I repeat then, and it may, I trust, be repeated 
 with confidence, that your argument is radically 
 vicious, and your conception of Constant Con- 
 junction entirely false. Your demonstration makes 
 no geater impression on the doctrine of necessity, 
 than if you were to attempt a refutation of New- 
 ton's Corollary, by shewing, that the porter, ad- 
 dressed by the two motives, will uniformly take 
 one of the sides, and not the diagonal of the 
 parallelogram. For it is no less absurd to reason 
 from the effect of physical forces to the effect of 
 motives, than to argue conversely; or, because 
 
231 
 
 the results are respectively different, to deny, in 
 either case, the existence of Constant Conjunction 
 between antecedents and consequents. 
 
FROM DR. GREGORY. 
 
 LETTER III. 
 
 SIR, 
 
 1 ROM end to end of that chapter of your Essay, 
 in which you profess to analyse and answer my 
 argument, you have thought fit to revile me in the 
 grossest and most outrageous terms of reproach and 
 contempt ; yet in the very first section of that 
 chapter you have prefaced the first specimen of 
 your expressions of reproach and contempt by & pro- 
 fession of modesty, and diffidence of your own mode 
 of reasoning ; which appears strikingly inconsistent 
 with the whole tenor of your subsequent discourse. 
 The incongruity is indeed so glaring, and irre- 
 sistibly leads to some strong surmises so un- 
 favourable to you and your cause, that I should 
 think it uncandid and unjust to publish any re- 
 marks on it, without first calling your attention to 
 it, and giving you an opportunity, and earnestly 
 begging of you to consider with attention, and 
 either to reconcile, if you can, those seeming in- 
 consistencies, or, if they cannot be reconciled, at 
 
233 
 
 least to account for them, and to explain them in 
 the manner which you think least unfavourable to 
 yourself. For this purpose, I have transcribed 
 the first paragraph of that part of your Essay 
 which relates to me. " Among the numerous 
 " supporters of the Libertarian hypothesis has 
 " appeared of late Dr. Gregory of Edinburgh. 
 " This gentleman has assailed the system of Ne- 
 " cessity in a manner somewhat new. It would be 
 " presumption in me to depreciate his metaphysical 
 " talents, or to pronounce those arguments futile, 
 " which in the judgment of many, perhaps, I shall 
 " not be able to overturn : but I cannot help ob- 
 " serving, that his Essay discovers, throughout, 
 " extreme vanity, arrogance, and ostentation ; qua- 
 " lities highly offensive, and generally character- 
 " istic of a weak and little mind. And notwith- 
 " standing the boasted logical precision of this 
 " mathematical champion, his reasoning appears 
 " to me vague, impertinent, and inconclusive ; his 
 " illustrations are inapposite, sometimes disgusting- 
 " ly tedious, and seemingly not so much calcula- 
 " ted to elucidate the subject, as intended to excite 
 " our wonder at the author's extensive knowlege. 
 " But I will not animadvert on the Doctor's Essay 
 "in the general, hut proceed to examine his argu- 
 " ments in detail." (Cromb&s Essay, page 326, 
 327.) 
 
 I can well believe that my illustrations may 
 
234 
 
 often have appeared to you and your brethren 
 disgustingly tedious : for that minute detail of all 
 the circumstances of the several cases stated, and 
 that strict attention to all the differences, which, 
 while I admitted the similarity in many respects 
 between the relation of motive and action and 
 that of cause and effect in physics, it was my pur- 
 pose to shew existed between these two relations, 
 must have been very disagreeable to you all. That 
 minute detail of things, which you had considered 
 and stated only in the most vague and general 
 manner, and that strict attention to differences, 
 which you had overlooked, are just the reverse of 
 that mode of viewing the subject, which makes us see, 
 in the most striking manner, that similarity, which I 
 acknowlege as fully as you can do, and prevents us 
 from seeing those differences, for which I contend, 
 and which you deny. Some very general prin- 
 ciples of human nature, which I therefore presume 
 to be, on the whole, the best for mankind, and 
 certainly useful even in science, though not all 
 that is useful, and even necessary, for strict philo- 
 sophical investigation ; those principles which are 
 well pointed out by BACON, whose words I 
 quoted in my Essay ; make it more easy, and more 
 agreeable, to attend to resemblances, than to ob- 
 serve the differences, among the things that we 
 contemplate: but when this natural propensity 
 has been long indulged, and become habitual on 
 
235 
 
 any subject, the opposite mode of proceeding 
 becomes peculiarly laborious, and intolerably dis- 
 agreeable. I scarce think it would be going too 
 far to say, that, to many persons, it becomes 
 almost or altogether impossible : I am convinced, 
 at least, it -would be absolutely impossible to many 
 persons, without the help of some of those instru- 
 ments mentis, as they are emphatically termed by 
 BACON, which enable men to acquire new notions, 
 and new trains of thought ; to perceive new rela- 
 tions, to correct their, former notions, to break 
 their former trains of thought, and to perceive 
 differences where formerly they suspected none. 
 Not only the peculiar mode of reasoning that I 
 employed, but even the algebraic notation by sym- 
 bols, and the " instant ice particulars earumquc 
 " series et or dines,'" which I introduced at so great 
 length into my Essay, were intended to be such 
 instrument a mentis. I am aware, that the first 
 attempts to use those instruments could not fail to 
 be awkward, imperfect, and disagreeable to every 
 person, especially to those who had long indulged 
 opposite habits : but to those who found that the 
 first use of those instruments was not only to 
 detect an error of the grossest kind in their 
 favourite system of philosophy, but at the same time 
 to convict themselves of the most foolish vanity, 
 disingenuity, and falsehood, in professing a belief 
 which they did not entertain ; the use of such 
 
236 
 
 instruments, the instruments themselves, and the 
 author or inventor of them, must all have been 
 objects of utter abomination. 
 
 Though I thus give you credit for thinking my 
 illustrations disgustingly tedious, I do not think 
 you entitled to equal credit when you profess to 
 think them inapposite. The pains which you have 
 taken (to the best of my judgment very unsuccess- 
 fully) to set them aside, and to explain them away, 
 and to shew that they were not apposite, and did 
 not warrant the conclusions which I drew from 
 them, afford, if not a complete proof, at least a 
 very strong presumption, first, that they were not 
 inapposite; secondly, that you did not think them 
 so. 
 
 Still less can I think you entitled to credit, 
 either in point of justness of thought or of sincerity, 
 when you say, that my illustrations are seemingly 
 not so much calculated to elucidate the subject, 
 as intended to excite your wonder at the author's 
 extensive knowlege. This is, at best, putting 
 the most unfavourable construction on what 1 have 
 done. Consider the object and purpose of my 
 Essay ; consider the very title of it ; not what you 
 have (perhaps inadvertently) represented it in the 
 title of the first section of your third chapter, An 
 Essay in defence of Philosophical Liberty, but An 
 Essay on the difference between the relation of Mo- 
 tive and Action and that of Cause and Effect in 
 
237 
 
 Physics : consider the plan of my Essay, in which 
 I formally renounce all appeals to consciousness, 
 and every kind of proof, except demonstrative rea- 
 soning by necessary consequences, and the decision 
 of all questions of fact by open unequivocal experi- 
 ment. Consider fully all these things, and then 
 say whether my illustrations, however disgustingly 
 tedious you may think them, can fairly be referred 
 to that contemptible vanity to which you are pleased 
 to impute them; or whether they are in any respect 
 improper or unnecessary. 
 
 Still less can I give you credit for really think* 
 ing my reasoning vague, impertinent, and inconclu- 
 sive. The reasoning which I employed is precisely 
 the same in kind with that which had been employed 
 by Necessitarians. The difference between the use 
 that they made of it, and that which I have made 
 of it, is chiefly this: They applied it only to a few 
 of many supposable cases ; and most confidently to 
 that one of equal and opposite motives : but I 
 apply it to a great many supposable cases. They 
 apply it to some cases in which the result will be 
 the same, on the principle of the necessity and on 
 that of the liberty of human actions : I apply it to 
 cases in which the result must be different, on those 
 two suppositions. They apply it chiefly to one case, 
 (that of equal opposite motives,) in which, by an 
 appeal to consciousness, and by certain arbitrary 
 hypotheses, gratuitously assumed by them, they 
 
238 
 
 think they can evade, or explain away, that in- 
 ference of their own reasoning, which, if brought 
 to the test of open unequivocal experiment, would 
 overturn their whole doctrine at once : I consider 
 many cases, and many inferences from the same 
 principles of reasoning, which admit of no appeals 
 to consciousness, which cannot be explained away 
 by gratuitous hypotheses, and in which the result 
 is not only different on the principle of Necessity 
 from what it is on the supposition of the Liberty 
 of human actions, but also different, according to 
 the relation of motive and action, and according 
 to that of cause and effect in physics. And lastly, 
 they have employed, without any minute investi- 
 gation or analysis, a principle of reasoning, which 
 they suppose to be simple, precise, and undeni- 
 able : but I have endeavoured to analyse that 
 principle ; to shew that it is vague in its meaning ; 
 in some meanings true, in others false ; and that 
 they themselves, in their reasonings, have often 
 blended or confounded the different things denoted 
 by it in its different meanings. But of this no man 
 living can testify more amply than yourself: for 
 in your attempt to answer my reasoning, which 
 was founded on one principle, or one meaning, ex- 
 pressed by the word cause, namely, that of constant 
 conjunction, you have availed yourself of another 
 principle, and another meaning of the term cause, 
 namely, " that for the sake of which /' which I 
 
239 
 
 conceive to be the proper and natural notion of 
 motive ; and not only different from, but absolutely 
 inconsistent with the notion or principle of constant 
 conjunction ; as appears by tracing the necessary 
 consequences of the latter supposition. These 
 consequences, in numberless cases, are glaringly 
 and ridiculously inconsistent with that result, 
 which every person of competent understanding 
 and knowlege expects, with confidence, to find 
 from the application of motives ; according to the 
 natural and just notion of the relation of motive 
 and action. You are welcome to take your choice 
 of two suppositions; and these are the only two 
 that can be made with respect to your own con- 
 duct, in attempting to refute my reasonings pro- 
 ceeding on the principle of Constant Conjunction, 
 by urging considerations founded upon the principle 
 of " that for the sake of which." Either supposi- 
 tion, with respect to you, will answer my purpose. 
 You must either have done it inadvertently, not 
 perceiving the great difference between the two 
 notions, or principles, which you have blended in 
 your discourse ; or you must have done it delibe- 
 rately and wilfully, knowing that those principles 
 were different, but yet thinking that they might 
 rationally, and without impropriety, be blended 
 together, and assumed as a complicated supposition 
 or principle of reasoning: just as in physics we 
 assume the inertia of bodv combined with a cen- 
 
240 
 
 tripetal and with a projectile force ; or as we, who 
 believe in the liberty of human actions, admit both 
 the influence of motives, and their occasional 
 conjunction with, and separation from, their pro- 
 per corresponding actions, and also the self-govern- 
 ing power of man; and from these complicated 
 suppositions, in numberless cases, deduce con- 
 clusions, or foresee the result, with a degree of 
 probability approaching very near to certainty. 
 
 Further, it. is impossible not to distrust your 
 sincerity in those opprobrious expressions of con- 
 tempt and reproach which you so liberally bestow 
 upon my argument, for this strong reason : as 
 soon at least as you had an opportunity of seeing, 
 and judging of, my Essay, but probably even 
 sooner, you must have known, that, in the course 
 of many years, it had been submitted to the deli- 
 berate consideration, and most rigorous criticism, 
 of many men of the greatest talents, the most ex- 
 tensive knowlege, and the highest eminence in 
 various branches of science : you must have known 
 that it had been submitted to the revision of every 
 Necessitarian with whom I was acquainted. In 
 particular, you must have known that I submitted 
 it to the revision of DR. PRIESTLEY, and that he 
 put it into the hands of MR. COOPER. You must 
 have known what a candid and liberal offer I 
 made to all those persons, on the supposition that 
 they could point out any error in my reasoning. 
 
241 
 
 You know that MR. COOPER promised, repeatedly, 
 to give me his objections to it, and even said he 
 thought he should have little difficulty in doing so; 
 and yet that he broke that promise, which was 
 voluntary on his part, and made after he had 
 perused my Essay ; and that he never condescended 
 to inform me of his reasons for breaking his 
 promise. All these things I stated explicitly, and 
 strongly: and you could have no reason to doubt 
 my veracity, in the account which I gave of 
 them. As little could you doubt my veracity, 
 when I declared that none of the persons, who 
 had revised my Essay, had given me any objec- 
 tions to it, but such as I could easily answer, 
 so as to convert them into illustrations of my 
 own argument; and that only one of them had 
 such confidence in his own objections, as to allow 
 me to publish them, even without his name, with 
 my reply to them subjoined. You certainly could 
 not regard as a forgery of mine, or as in any 
 measure misrepresented by me, the objections of 
 that one Necessitarian, which, with his permission, 
 are printed in my appendix. You certainly eanr 
 not doubt, even from the tenor of his own objec- 
 tions, that he was eagerly desirous to discover and 
 to point out some defect or error in my reasoning. 
 You must have perceived that he was not very 
 scrupulous in the means which he employed for 
 that purpose ; such as wandering very far from 
 let. Q 
 
242 
 
 the point which 1 undertook to discuss, from the 
 propositions which I professed to have demonstra- 
 ted, and from the mode of reasoning which I 
 employed ; giving his own account, and that one 
 very unfavourable to me, of what I had stated ; 
 and even imputing to me such things as I not only 
 had never stated or assumed, but had expressly 
 disclaimed. Can you suppose that that person, 
 or that MR. COOPER, or that any Necessitarian 
 who read my Essay, should have failed to perceive, 
 or should have been unwilling to point out to me, 
 that my reasoning was vague, impertinent, and 
 inconclusive, and my illustrations inapposite, and 
 sometimes disgustingly tedious, if they had perceived 
 such faults in my Essay ? Can. you conceive that 
 it was reserved for you to discover faults so glaring, 
 and which, if real, must have been obvious to every 
 reader even of the meanest capacity ? In another 
 point of view; Does it not indicate a very extra- 
 ordinary degree of vanity and arrogance in you, to 
 suppose that you had discovered at once such mon- 
 strous faults in my argument, in which so many 
 of the ablest men that ever this country produced 
 could find no error whatever? 
 
 But supposing, for the sake of argument, that, 
 by your uncommon sagacity, and superior talents 
 in every respect, you had discovered those mon- 
 strous faults in my argument, which others, who 
 had examined it carefully, could not perceive ; 
 
243 
 
 how could you suppose that, in the judgment of 
 many, or even in the judgment of any, you perhaps 
 should not be able to overturn such a futile argument? 
 Such faults as you profess to have found in it, if 
 real, must be fatal to it; and must even preclude 
 all doubt or dispute about it. The dullest, as well 
 as the acutest of reasoners, though they might not 
 have perceived such faults in it themselves, must 
 have at once perceived the force of them when you 
 pointed them out. If you believed what you have 
 said unfavourably of my argument, in the first 
 paragraph of your chapter relating to it, or if you 
 believed that your own mode of answering an ar- 
 gumentum ad absurdum, by declaring vehemently 
 that those inferences were notoriously and ridicu- 
 lously false or absurd, which were given as such, 
 was valid and rational, you could not, even for a 
 moment, have doubted, that every person of compe- 
 tent understanding must perceive your argument to 
 be valid, and mine disgracefully futile. It is right 
 to tell you explicitly, why T call upon you at least 
 to account for, if you cannot reconcile, such 
 strange inconsistencies in your own discourse. 
 The unworthy expedient of affecting violent passion 
 to hide the want of argument, and of indulging in 
 declamation and invective to supply that want, is 
 common, and well understood. In a viva voce 
 debate it has often been employed by a skilful, 
 but uncandid and very impudent orator, to brow- 
 
244 
 
 beat and silence his opponent. This good purpose 
 no disputant can expect it to serve in a scientific 
 discussion or controversy, carried on deliberately, 
 by writing and printing. Yet many examples, 
 some of them very recent and notorious, shew 
 that the same unworthy expedient is now and then 
 tried by writers, as well as by orators. In some 
 such cases, and very particularly in your own, a 
 strong suspicion arises, that all that blustering and 
 affectation of passion, is employed in hopes that the 
 person on whom it is bestowed will regard it with 
 such contempt as not to deign to make any reply 
 to it. This is the only good purpose that it can 
 serve ; for, if the person on whom it is employed 
 shall choose to answer such a publication, it gives 
 him advantages great as his heart can wish. If 
 your purpose in all your outrageous reviling of me 
 was only to prevent me from making any reply to 
 your reasoning, I thank you for the compliment, 
 and tell you frankly that you would have succeeded 
 in your purpose, if my argument had related solely 
 to the philosophical question announced in the 
 title of it: but the corollary resulting from my 
 demonstration of that difference, 1 mean the infer- 
 ence with respect to the mala Jides of those who 
 had professed to believe in the doctrine of Neces- 
 sity, placed me in a very peculiar situation, and 
 imposed on me the indispensable obligation of either 
 acknowleging the error of my argument, and 
 
245 
 
 the injustice of that severe corollary ; or else of 
 shewing that both my argument, and that corollary, 
 were perfectly just. For this purpose your argu- 
 ment, and especially your abuse of me, which 
 you probably thought was to mortify me greatly, 
 were not only acceptable, but inestimable. But, 
 before I can with propriety make that use of it, I 
 must give you this fair opportunity of preventing 
 me from doing you any injustice. 
 
REPLY 
 
 TO LETTER III. 
 
 oL OUR third Letter is introduced \vith an at- 
 tempt to convict me of inconsistency. This, with 
 you, is no uncommon endeavour. You will not 
 be persuaded, that your opponents can possibly 
 think unfavourably of your argument. Nay, you 
 will not be persuaded, that they believe in their 
 own doctrine. Dissent from your demonstration 
 seems, with you, to be another name for dish> 
 genuity. You observe, there is " a glaring incon- 
 " gruity between my expressions of contempt for 
 " your mode of reasoning, and my professions of 
 " modesty and diffidence of my own." 
 
 If there be any expressions of diffidence in the 
 introductory part of my answer, irreconcileable 
 with the opinion which I have delivered, respecting 
 your demonstration, they may be accounted for, 
 on the supposition, that the contagio malt, by per- 
 using your Essay, had not yet exerted its influence. 
 But I perceive no inconsistency in a writer's de- 
 claring his conviction of the invalidity of an ar- 
 gument, in the strongest terms, and, at the same 
 
247 
 
 time, expressing 1 a doubt, whether he may be able 
 to expose its fallacy, to the satisfaction of every 
 reader. 
 
 You employ some pages in endeavouring to 
 account for your illustrations appearing offensively 
 tedious " to me and my brethren ;" and the account, 
 which you give, is strictly in your own manner. 
 It requires not the signature of your hand to shew, 
 who is its author. Now, how obtuse soever our 
 judgments may be, I cannot help observing, that 
 we have perspicacity enough to see, that your in- 
 strumenta mentis may indeed have furnished you 
 with " notions and trains of thought," distin- 
 guished by novelty (for they are certainly new) 
 but by no other quality, which can serve to recom- 
 mend them. After acquainting us with the neces- 
 sity of being possessed of these imtrumenta mentis, 
 you are pleased with singular courtesy, superla- 
 tive modesty, and all that liberality by which you 
 are so eminently distinguished, to acquaint me 
 that the first use of these instrumenta mentis was 
 " not only to detect an error of the grossest kind 
 " in our favourite system of philosophy, but at the 
 " same time (mark the words) to convict us of the 
 " most foolish vanity, disingenuity, and falsehood ;" 
 and you say " that the use of such instruments, 
 " the instruments themselves, and the author or in- 
 " ventor of them, must all have been objects of 
 " utter abomination to us." 
 
248 
 
 The unparalleled rudeness, and outrageous illi- 
 berality, of this passage, require no comment. 
 How little to be envied, how little to be respected 
 is that spirit, which could dictate sentiments, so 
 abhorrent to every principle of candour, and cha- 
 rity. " To convict us of the most foolish vanity, dis~ 
 "ingenuity, and falsehood." Sir, " no schooling" 
 which you have received, or can receive from me, 
 is an adequate chastisement for this insolent 
 violation of those principles, which become the 
 man, the philosopher, and the gentleman, 
 
 It gratifies me, however, to observe, that you do 
 not doubt ray sincerity, when I declare, that I 
 consider your illustrations to be disgustingly te- 
 dious. You have acknowleged, indeed, that in 
 this opinion I am not singular. One gentleman, 
 " a man of superior talents, and great erudition, 
 " and extensive general knowlege, peculiarly well 
 " versed in metaphysics, and much used to close 
 " and accurate reasoning" appears likewise by 
 your own confession to have been tired, and dis- 
 gusted with them. 1 
 
 But, though you give me credit, for thinking 
 your illustrations offensively tedious, you do not 
 consider me entitled to equal credit, when I pro- 
 fess to think your illustrations inapposite. Your 
 reason for doubting the sincerity of my decla- 
 ration, is so singular, and extraordinary, that it 
 
 1 See Introduction to Dr. G/s Essay, p. 158. 
 
249 
 
 demands the particular attention of the reader. 
 The pains, you say, which I have taken (" to the 
 " best of your judgment very unsuccessfully") to set 
 your illustrations aside, to explain them away, 
 and to shew, that they were not apposite, afford, 
 if not a complete proof, at least a very strong pre- 
 sumption, 1st. that they are not inapposite, and 
 2dly. that I did not think them so. It is difficult to 
 imagine the ground, or conjecture the principle, 
 on which some of your opinions are formed. If 
 your presumption here be well founded, or if your 
 conclusion be just, it would appear, that the pains, 
 which a controvertist employs, to evince the irre- 
 levancy of an illustration, or the invalidity of an 
 argument, proves 1st. that the illustration is per- 
 tinent, and the argument conclusive, and 2dly. that 
 he himself believes them to be so. I should like 
 to see, I must own, the process of reasoning, ex- 
 hibited in due form, by which these singular con- 
 clusions are deduced. I should like to see it pre- 
 sented in the shape of a syllogism, that we might 
 clearly perceive, how the pains taken to overturn 
 an argument, or to set aside an illustration, evince 
 the writer's insincerity, or how they prove, that he 
 believes that to be pertinent, which he affirms to be 
 irrelevant. It is possible I may misconceive the 
 principle, as well as the purport of your observation, 
 but it seems to me, that, by parity of reasoning, the 
 pains, which you have taken (" to the best of my 
 
250 
 
 "judgment, very unsuccessfully") to prove the ar- 
 guments for Necessity fallacious, " afford, if not a 
 " complete proof, at least a very strong presump- 
 " tion, 1st. that they are not fallacious, and 2dly. that 
 " you do not think them so." Will you admit 
 these conclusions ? They appear to follow a for- 
 tiori, if your deduction is just. The pains, which 
 you have employed, have been much greater, and 
 your attempt, I presume, much less successful. 
 
 I shall now leave the reader to judge of the va- 
 lidity of your reasons for doubting my sincerity, 
 and proceed to observe, that, if you will take the 
 trouble to revise your own work, and my answer, 
 you will certainly find, that almost all your illus- 
 trations I have passed over in silence, and for this 
 reason, because I deemed them irrelevant, and in- 
 sufferably tedious. Your argument I was at pains 
 to examine; but your illustrations, in general, I 
 deemed unworthy of notice. They form such an 
 assemblage of heterogeneous and discordant ma- 
 terials, that they resemble more the vagaries of a 
 fever-struck brain, the cegri somnia, than the 
 elucidations of a calm and unclouded intellect. 
 Whatsoever seems casually to have presented 
 itself to your fancy, as if you were incapable of 
 taste, discrimination or selection, you have crowd- 
 ed into the group, and forced into the service of 
 your mathematical demonstration. There exists 
 scarcely an object, whether high or low, in nature, 
 
251 
 
 or in art, which you have not seized, as an illus- 
 tration from " a fresh hen's egg, hatched in 
 " three weeks, with a degree of heat, equal to 100 
 " of Fahrenheit," to " a sturdy oak, growing from 
 " an acorn, in Windsor forest," and " a drachm of 
 " bark, with ten grains of calx of iron, taken daily, 
 " for the recovery of strength." ' But, as a sample 
 of your illustrations, I select the following passage; 
 and let the candid reader judge, how far they 
 merit the censure, which I have ventured to pro- 
 nounce. " A mass of iron exposed to heat, a 
 " ship under sail, a cannon ball, when shot from a 
 " cannon, wort in Papin's digester, an egg placed 
 " in a common oven, an acorn planted in a very 
 " moist soil in the torrid zone, a man, who has 
 " just drank a quantity of brandy, a fellow, who 
 " is offered a sum of money, on condition, that he 
 " drink a certain quantity of brandy, and who is 
 " willing to earn the money, on that condition, 
 " though otherwise not disposed to drink brandy, 
 " which, though shameful, is a real case, and not 
 " a very uncommon one, are all subjects, suscep- 
 " tible of change, and all have certain causes, and 
 " principles of change applied to them." a This 
 specimen of illustration (and it is far from being 
 a solitary one) I submit to the judgment of the 
 impartial and intelligent reader. To his tribunal 
 
 1 . ii. p. 283. 
 a . ii. p. 292. 
 
252 
 
 I appeal, and by his decision I shall cheerfully 
 abide. 
 
 But the truth is, you seem determined to believe, 
 that it is quite impossible, I should think unfavour- 
 ably of your Essay. You seem resolved to ques- 
 tion my veracity, when I offer an opinion, in 
 disparagement of your demonstration. Accord- 
 ingly, you proceed to inform me, that you cannot 
 give me credit for thinking your reasoning vague, 
 impertinent, and inconclusive. In answer, I can 
 only repeat my solemn asseveration, that, the 
 more I examine your argument, the more I am 
 convinced, that nothing was ever presented to the 
 public, more vague, or more inconclusive. Why 
 will you not believe me? 
 
 You distrust my sincerity (for there is no limit 
 to your unbelief) in " those opprobrious ex- 
 " pressions of contempt, and reproach, which" you 
 say, " I so liberally bestow on your argument." 
 To this exaggerated charge a reply has been 
 already offered. I shall, therefore, now only re- 
 mark, that it has been delivered as my opinion, 
 that your reasoning is fallacious, inconclusive 
 absurd. Are these the opprobrious reproaches to 
 which you refer, as liberally bestowed on your 
 argument ? If they are, it must excite the surprise 
 of every candid and attentive reader, who has 
 perused your Essay, to hear these epithets exag- 
 gerated into " opprobrious reproaches," when he 
 
253 
 
 reflects, that these same terms are repeatedly ap- 
 plied by yourself to the arguments of your oppo- 
 nents ; and when he considers further, that you 
 have loaded their moral characters with the most 
 contumelious imputations. I am fully aware, that 
 to retort a charge, though it should silence an 
 adversary, is no vindication of error; and that 
 rudeness offered will not justify rudeness retaliated. 
 But I may be permitted to remark the fact, to 
 which I have alluded ; and also to observe, that 
 I do not consider the epithets, applied to your 
 argument, as " opprobrious reproaches ;" nor am I 
 acquainted with any substitutes for these terms, 
 which would express my conviction of the fallacy, 
 and absurdity of your reasoning. But your object, 
 it would seem, by your repeated complaints, and 
 exaggerated representations, in your controversial 
 writings, is either to excite the sympathy of your 
 readers, or to rouse an odium or prejudice against 
 your opponents. 
 
 Your reason for doubting my sincerity, when I 
 pronounce your arguments fallacious, inconclusive, 
 and absurd, I shall deliver in your own words. 
 You say, " As soon at least, as /had an oppor- 
 " tunity of seeing, and judging of your Essay, but 
 " probably even I must have known sooner, that, in 
 " the course of many years it had been submitted 
 " to the deliberate consideration, and most rigor- 
 " ous criticism, of many men of the greatest talents, 
 
254 
 
 " the most extensive knowlege, and the highest 
 " eminence in various branches of science." There 
 is certainly more of vanity, than of accuracy in this 
 statement. If there be not, I desire to know, what 
 makes it probable, that I had learned, that your 
 Essay had been submitted to the criticism of men 
 of science, before I saw it On what ground do 
 you advance this assertion? Be not deceived; 
 self-flattery is self-deception. I never heard of 
 your Essay, till it was accidentally put into my hand 
 by a friend, whom I found reading it, and who 
 immediately lent it to me : nor had I ever a copy 
 of it, which I could call my own, till I received 
 the first of your series of letters, ten years after its 
 publication. 
 
 You say I must have known, that it had been 
 submitted to the revision of every Necessitarian, 
 with whom you were acquainted. " In particular" 
 you say " I must have known that you submitted 
 " it to the revision of Dr. Priestley, and that he 
 " had put it into the hands of Mr. Cooper." All 
 this I knew on your authority, after perusing your 
 Essay ; nor did I ever question the truth of your 
 statement. 
 
 Then comes your argumentum ad verecundiam, 
 of all logical arguments, in my judgment, far the 
 weakest. It is seldom resorted to,- unless by 
 those who are compelled to employ it, as their 
 last resource. 
 
255 
 
 Highly dissatisfied, that I should presume to 
 think or speak disrespectfully of your Essay, or even 
 to point out a single fallacy in a work, which you 
 had submitted to men of pre-eminent talents, you 
 proceed to charge me with vanity and arrogance. 
 You say, " /could have no reason to doubt your 
 " veracity, when you declared that none of the 
 " persons, who had revised your Essay, had given 
 " you any objections to it, but such as you could 
 " easily answer, so as to convert them into illustra- 
 " tions of your own argument." 
 
 That yon firmly believed, you could easily 
 answer their objections, I do not entertain the 
 shadow of doubt. I know well your confidence 
 in your Mathematical skill ; I am fully sensible, 
 how highly you estimate your own powers. But 
 conceit is not science, arrogance is not wisdom, 
 and the semblance of accuracy is widely different 
 from accuracy itself. I know also, your fancied 
 dexterity in converting the arguments of your 
 opponents to your own purpose. What you have 
 said of one gentleman's objections you have said 
 also of mine. You have been pleased to inform 
 me likewise in one of your Letters that you can 
 make an excellent use of my reply to your first 
 letter, and in the most polite manner condescend 
 to thank me for it. You acquaint us also in your 
 Introduction, that the Essay was submitted to 
 several literary men, who would not suffer you to 
 
256 
 
 publish their objections, though " this offer you 
 " had made to them all, as you were truly desirous 
 " to have the advantage of some of the many admir- 
 " able illustrations, which their objections afforded." 
 
 In what a deplorable situation are Necessarians 
 placed ! They cannot, it seems, assail your de- 
 monstration, without wounding their own cause. 
 They cannot lift a weapon against you, but with 
 consummate dexterity you turn it against them- 
 selves. Sad infatuation ! fatal blindness ! that 
 they should write, and write, and write, solely to 
 defeat their own purpose. They must be the most 
 perverse, as well as the most wretchedly blind, of all 
 human beings, sunk in ignorance, buried in worse 
 than Cimmerian darkness. Oh for a ray of your 
 Mathematical science, to illumine their benighted 
 minds. But alas! this ray has shed its influence in 
 vain. They have seen the glory of your demon- 
 stration, and it has been to them, like " the light 
 " shining in darkness." 
 
 In prosecuting your argument ad verecundiam, 
 you tell me, that I must have perceived, that one 
 of your unconverted friends, one of the men of 
 science whom you consulted, and who it seems 
 
 did not agree with you, who actually refused 
 
 his assent to a Mathematical demonstration, " was 
 " not very scrupulous in the means, which he 
 " employed for detecting some defect, or error, in 
 " your reasoning." This gentleman you place 
 
257 
 
 under the same condemnation with myself: for 
 you have charged me also, with not being very 
 scrupulous about the means, which I have em- 
 ployed to refute your argument. Either you 
 must be peculiarly unfortunate in meeting with 
 such opponents, or your complaints must resem- 
 ble those of the two characters, described by the 
 poet. 
 
 Nota refert meretricis acumina ssepe catellam 
 Saepe periscelidem raptam sibi flentis, uti mox 
 Nulla fides damnis, verisque doloribus adsit ; 
 Nee semel arrisus triviis attollere curat 
 Fracto crure planuin, licet illi plurima manet 
 Lachryraa. 
 
 But what were the means, which he employed 
 to overturn your argument ? " Wandering very 
 " far from the point, which you undertook to dis- 
 <( cuss, from the propositions, which you professed 
 " to have demonstrated, and from the mode of 
 " reasoning, which you employed, giving his own 
 " account, and that one very unfavourable to you, 
 " of what you had stated, and even imputing to 
 " you, such things, as you not only had never 
 " stated or assumed, but had explicitly disclaim- 
 " ed." Here again, he and I have the misfortune 
 to be concluded in the same condemnation ; for it 
 seems, I have been found guilty of the very same 
 offence. But I have reclaimed against your judg- 
 ment, and refer the cause to a superior tribunal. 
 In the mean time, I see no reason to alter the 
 
258 
 
 opinion, which I have already delivered, that, 
 how explicitly soever you may disclaim some 
 opinions, which I have ascribed to you, they 
 necessarily adhere to your argument. I do not 
 mean to affirm that .you believe these opinions, 
 (for who could believe such absurdities) but I 
 maintain, that your demonstration essentially in- 
 volves them. , 
 
 Now comes the close of the argument ad vere- 
 cundiam, sufficient to overwhelm any human being 
 with shame, who is not an obdurate Necessarian. 
 You say " Can you suppose, that person, or that 
 " Mr. Cooper, or that any Necessitarian, who 
 " read my Essay, should have failed to perceive, 
 " or should be unwilling to point out to me, that 
 " my reasoning was vague, impertinent and incon- 
 " elusive, and my illustrations inapposite/ and 
 " sometimes disgustingly tedious? Can you con- 
 " ceive, that it was reserved for you to discover 
 " faults so glaring, and which, if real, must have 
 " been obvious to every reader? Does it not dis- 
 " cover a very extraordinary degree of vanity and 
 " arrogance in you, to suppose, that you had dis- 
 " covered at once such monstrous faults,' in my 
 " argument, in which so many of the ablest men, 
 " that this country ever produced could find no 
 " error whatever?" Here indeed is the argument 
 ad verecundiam exhibited in all its energy. Who 
 would not blush for differing from the learned 
 
259 
 
 men, who could find no error in your demonstra- 
 tion ! The only support, which a humble indivi- 
 dual like me can have, under the oppressive weight 
 of so heavy an argument, is a circumstance, which 
 for the moment, seems to have escaped your atten- 
 tion, namely, that some of these same learned men 
 did not consider your demonstration to be a demon- 
 stration, that they entertained nearly the same 
 opinion of it with myself, and thought your reason- 
 ing fallacious. This keeps one in countenance. 
 It furnishes something like a shield of defence. 
 But, while I appeal to the judgment of some of 
 those philosophers, those able men, to whom you 
 refer, and who rejected your demonstration, I 
 would appeal also to a still higher tribunal. Give 
 me leave to ask, in the name of common sense, to 
 what purpose is all this empty parade this idle 
 vanity, this pompous reference to the judgment of 
 others? Do you mean to answer argument by 
 authority ? Do you mean to affirm, that, because 
 you submitted your Essay to the examination of 
 learned men, who did not tell you, that your 
 reasoning was inconclusive I am forsooth, on this 
 account, in repugnance to my own convictions, to 
 believe and say, that your reasoning is not incon- 
 clusive? Is this philosophy? Is it reason, or 
 common sense ? Does Bacon, whom you so often 
 quote, and whose authority you cannot revere 
 more than I do, recommend such procedure ? He 
 
260 
 
 does not ; but if he did, I should not hesitate to 
 protest against so irrational an injunction. The 
 man, who will not reason, is a bigot ; and he, who 
 dares not reason, is a slave. Unless then you mean 
 to tell me, that I ought to see as other men see, hear 
 as they hear, and believe as they believe, let me ask, 
 to what useful purpose, in the name of reason, is this 
 frothy appeal to the judgment of others concerning 
 your Essay ? Is it possible to read such observa- 
 tions, and think respectfully of that mind from 
 which they proceed ? They are utterly unworthy 
 of any serious attention. 
 
 The opinion of Dr. Priestley concerning your 
 work, and that also of several of your own 
 friends I know well : and if Dr. Priestley or Mr. 
 Cooper, did not answer your argument, it was 
 not, be assured, because they believed it to be un- 
 answerable. Why Mr. Cooper, who is to me an 
 entire stranger, did not send you his promised 
 objections, I do not know. His opinion of your 
 Essay he has given to the world ; and in this 
 opinion he is by no means singular. 
 
 In answer to the last paragraph of your letter, 
 I observe, that the faults, which I profess to find 
 in your Essay, are in the judgment of many as 
 well as myself, fatal to your argument. That my 
 reasoning would convince every reader, I had 
 neither the folly, nor the vanity to suppose. In 
 metaphysical discussions, even, where the ques- 
 
261 
 
 tion is less difficult, than the present, concordance 
 of sentiment is not to be expected. 
 I am, 
 
 Sir, 
 
 Yours, &c. 
 
FROM DR. GREGORY. 
 
 LETTER IV. 
 
 SIR, 
 
 JLN several parts of your chapter relating to me, 
 you have thought fit to assert that I have said, 
 that all Necessarians are insane, or fools, or lunatics. 
 In what part of my Essay have you found any 
 such proposition asserted by me? or any thing 
 that can be construed or tortured into such a 
 meaning? Nothing can be farther from my 
 thoughts than such an opinion of them ; nor any 
 thing more inconsistent with the whole tenor of 
 my argument, and especially with that conclusion, 
 or corollary, 'on which I laid great stress, and 
 which I well know has given great offence ; that 
 none of them really believe that doctrine which 
 they all profess to believe. My belief of that un- 
 favourable conclusion with respect to them (as 
 you must know if you read my Essay) was founded 
 on the consideration, that their own actions, and 
 their judgments and expectations of the actions of 
 others, in all cases in which the result in point of 
 overt action was different according to the doctrine 
 of Necessity and that of the Liberty of human 
 
203 
 
 actions, uniformly corresponded to the latter prin- 
 ciple: or, in other words, that not one of them 
 admitted, or professed to admit, or thought it 
 necessary to try experimentally, any one of those 
 inferences which I had shewn to be necessary 
 consequences of their own doctrine ; while yet 
 they could show no error in my supposed deduction 
 by necessary consequences: but only saw plainly 
 that all of them must be false as matters of fact. 
 
 Examine my Essay from end to end, as rigor- 
 ously as you please, and you will find that I do 
 not undertake to convict Necessarians of folly or 
 lunacy, but only of disingenuity, and a contemp- 
 tible sort of vanity, that led them to think it an 
 honourable distinction from the vulgar, to profess 
 an opinion contrary to the common sense of man- 
 kind ; and to pretend to believe a sophism, which 
 they had unknowingly contrived for themselves, 
 and were unable to detect. 
 
 I beg leave, in particular, to call your attention 
 to the account which you have been pleased to 
 give (in your 394th page) of the 14th section* of 
 my Essay. You ^discuss it in somewhat less than 
 three lines, containing the following words. " Sec- 
 " tion 14 contains one very important piece of 
 " information, namely, that all Necessarians are 
 
 " insane." As you have taken notice of that 
 
 section of my Essay in its regular numerical order 
 between the 13th and the 15th, I cannot suppose 
 
264 
 
 that there is any error, either of your own or of 
 the printer's, in the number of that section, of which 
 you give so short and pithy an account; which 
 otherwise I should have been irresistibly led to 
 suspect : for certainly there is no section in my 
 Essay, or in any Essay ever yet written, which 
 corresponds less to that strange account which 
 you have given of its contents. 
 
 The real contents of it, as you will see on turning 
 to my Book, are fairly expressed in the follow- 
 ing words " Observations on an ancient paradox, 
 " with respect to the notion of Motive, founded 
 " on the analogy between Agent and Motive, and 
 " the ambiguity of common language. Analogy 
 " between it and the modern philosophical doctrine 
 " of Necessity :" -nor is there, in the whole of 
 that section, one expression, or one word, that 
 you, or any person, can be supposed to understand 
 as an " information that all Necessarians" or that 
 any Necessarians, " are insane" I should have 
 been utterly at a loss to guess what you could 
 mean by such a gross falsification of the substance 
 of that most inoffensive section of my. Essay, if 
 your own paragraph immediately subjoined to it 
 (the first of your 395th page) had not in some 
 measure explained to me what purpose your mis- 
 representation of the import of that section was 
 intended to serve. I am aware that you have 
 marked, in your table of Errata, three important 
 
265 
 
 corrections of that one paragraph ; for which cor- 
 rections I shall give you due credit : but, in .the 
 first place, I must consider that paragraph, as it 
 must be read and understood by every person who 
 peruses your Essay. It is in the following words 
 " If this be the fact, that Necessarians are, in 
 " truth, lunatics, as Dr. Gregory has oftener than 
 " once affirmed them to be, what shall we think 
 " of that person's understanding who has written 
 " two volumes of profound metaphysics to convince 
 " them of an error ? Of the several reproachful 
 " appellations, which the Essayist has liberally 
 " bestowed on his adversaries, there is one mono- 
 " syllabic term which he has occasionally applied 
 " to them, not unsuitable to his character who 
 " reasons with a madman." 
 
 I judge (but it is to be understood with a salvo 
 jure to you, who I trust will have the goodness to 
 set me right if I am mistaken, or if you think I do 
 you any injustice,) that your misrepresentation of 
 the general tenor of my Essay, and in particular 
 of the contents of my 14th section, was intended 
 to give you an opportunity to disppse of your wit- 
 ticism, on the supposed folly or madness of a man 
 who should attempt to reason with madmen. As 
 neither the whole tenor, nor any particular passage, 
 of my Essay, could ever have suggested to you so 
 bright a thought, I presume that bright thought, 
 which was evidently too good to be lost or sup- 
 
266 
 
 pressed, had suggested to you the necessity of 
 giving such an account of what I had said in my 
 Essay. As to the witticism itself, I am highly 
 pleased with it ; and shall be happy to see a great 
 many more such witticisms of your's, even at my 
 own expense. 
 
 In your table of Errata, you desire your reader 
 to make the following corrections in the paragraph 
 of your Essay which contains that witticism. 
 
 1st, For oftener than once, to read by implication. 
 So then, I have not oftener than once affirmed that 
 Necessarians are in truth lunatics, but only have 
 affirmed that by implication. This, I presume, 
 means, that I had insinuated that such was the 
 case. As this is your own deliberate correction of 
 what you had at least as deliberately written and 
 printed, you will not, I trust, think me unreason- 
 able, when I require of you to specify the passage 
 or passages in my Essay, in which I have insinuat- 
 ed, or affirmed by implication, that Necessarians 
 are lunatics : for such insinuation is as foreign from 
 my thoughts, and as repugnant to any thing that 
 I remember to., have written or printed, as the 
 repeated affirmation of the same proposition. 
 
 In your table of Errata, you desire your reader, 
 for reproachful appellations liberally bestowed, (by 
 me on my adversaries,) to read indecent and in- 
 directly. I cannot remember any indecent or re- 
 proachful appellations, either liberally or indirectly 
 
207 
 
 \ 
 
 bestowed by me on my Necessarian adversaries 
 There appears to me something hard to be under- 
 stood in the expression indecent appellations in- 
 directly bestowed : but certainly you are the fittest 
 person in the world to explain your own expres- 
 sion ; and I trust you will do so, if, on mature 
 consideration, you shall think it has any rational 
 meaning. You will 'also, I trust, have the good- 
 ness to illustrate your explanation of that obscure 
 sentence, and at the same time to prove the truth 
 of your deliberate assertion of my having bestowed 
 indecent appellations on my adversaries ; no mat- 
 ter whether they were bestowed liberally, or only 
 indirectly. I need not point out to you, that the 
 only proper evidence of such unworthy conduct on 
 my part will be the fairly quoting, in my own words, 
 such indecent appellations, or expressions, in my 
 Essay, and giving precise references to the pages 
 and lines in which they occur. If your own ex- 
 pressions with respect to me, several of which I 
 have already quoted to you in this Letter, be not 
 indecent and reproachful in a very high degree, 
 perhaps those which I have employed in my Es- 
 say will be thought so by you ; for they are widely 
 different from those which you have, not by im- 
 plication, but oftener than once, not indirectly, but 
 most liberally, bestowed upon me. When those 
 expressions of mine, which you profess to censure, 
 as indecent at least, if not reproachful, are fairly 
 
268 
 
 stated, and compared with your own expressions 
 in regard to me, either as originally printed, or as 
 deliberately corrected by yourself, it will appear 
 at once which of us has bestowed indecent or re- 
 proachful appellations on his adversary. At pre- 
 sent, it appears to me, that your censure on that 
 subject is extravagantly unjust, and groundless, 
 with respect to me ; but would be perfectly just, 
 and well merited, if applied to yourself. 
 
 On comparing that paragraph last quoted from 
 your Essay, (the first of your 395th page,) with 
 your three important corrections of it stated in 
 your table of Errata, it is evident that not one of 
 those errors could have been made by the printer. 
 They must therefore have been errors of your own 
 making : errors of which you were not sensible in 
 writing and revising your composition, or even in 
 reading the proof-sheets of your Essay ; but of 
 which you afterwards became sensible. Whether 
 you became sensible of them purely by your own 
 deliberate consideration of what you had printed, 
 or were made sensible of them by the admonitions 
 of some other person, who had read your Essay as 
 well as mine, it is not for me to determine ; 
 but it may be worth your while to mention how 
 you became sensible of those errors, and why you 
 made the corrections which we find in your table 
 of Errata. If your assertions with respect to me, 
 as originally printed, were true, you could not have 
 
269 
 
 thought them errors ; and you ought not to have 
 altered them, or softened your expressions of cen- 
 sure with respect to me ; on whom, in that case, 
 they would have been well bestowed. Your cor- 
 rections of that curious paragraph imply, that you 
 had either discovered of yourself, or had been made 
 sensible by others, that your assertions with respect 
 to me were false, and your censures unjust. Those 
 corrections appear to me neither more nor less than 
 an attempt to escape the censure which your false 
 and unjust account of what I had written must have 
 brought upon you, by secretly, and as it were by 
 stealth, eating up your own words, without explicitly 
 achwwleging and retracting what you knew to be 
 false, and unjust with respect to me ; which you 
 still allowed to remain glaring on your page. But 
 even if you had cancelled that leaf, and suppressed 
 every word of that paragraph under review, the 
 falsity of your assertions, and the injustice of your 
 proceedings with respect to me, would still have 
 been glaring. The same assertion with respect to 
 me, namely, that I declared all Necessarians to be 
 insane, and particularly that this is asserted in my 
 14th section, remains on your preceding page 
 (394th) unretracted, uncorrected, unsoftened in any 
 degree. No notice is taken of that extravagant 
 assertion in your table of Errata. You seem not 
 to have discovered, or to have been informed, that 
 there was a perfect incongruity in allowing one of 
 
270 
 
 those paragraphs to stand unconnected and un- 
 noticed in your Errata, when you endeavoured, 
 in those Errata, to itnsay the same things which you 
 had asserted in your very next paragraph. 
 
 You will also, I hope, have the goodness te 
 mention what " monosyllabic term" I have occasion- 
 ally applied to my adversaries, " not unsuitable to 
 " his character who reasons with a madman" and to 
 favour me with a precise reference to some, at least, 
 of the pages and lines, in which I have applied to 
 them any such " monosyllabic term :" for as your as- 
 sertion is altogether repugnant to my long-esta- 
 blished opinion of Necessitarians, and also to the 
 uniform tenor of my Essay, I suspect your asser- 
 tion to be a purejiction of your own, like those in 
 the same paragraph which in your table of Errata 
 you have endeavoured to eat up ; and that the 
 whole of your paragraph, the first of your 395th 
 page, is intended falsely to impute to me, what 
 you well knew I never had asserted, but what I 
 have no doubt you earnestly wish I had asserted. 
 
REPLY TO DR. GREGORY'S 
 
 FOURTH LETTER. 
 
 SIR, 
 
 JL ou introduce your fourth letter with requiring, 
 that I should specify the passages, in which you 
 have insinuated, that Necessarians are insane; 
 and you expatiate with characteristic prolixity on 
 my table of Errata, dealing out, at the same time, 
 your wonted charges of falsehood, and injustice 
 charges with you so common, in every controversy 
 in which you have been engaged, that they neither 
 excite surprise, nor provoke indignation. From 
 the tone of confidence, in which your requisition 
 is expressed, a reader, unacquainted with your 
 peculiar manner, would naturally conclude, that- 
 you had never never once insinuated the charge 
 against Necessarians, which I have iinputed to 
 you. What your private opinion of us may be, I 
 do not profess to know; nor do I hold myself 
 responsible for any contrariety (I say not, inten- 
 tional) which may subsist, between your senti- 
 ments and your expressions. But I repeat, what 
 has been elsewhere asserted, that you have indi- 
 
272 
 
 rtctly, and I now add, oftener than once, repre- 
 sented Necessarians as insane. 
 
 The first instance, in which you insinuate this 
 offensive imputation against those who believe in 
 the doctrine of necessity, I shall exhibit to the 
 reader, in your own words. You observe, (Introd. 
 p. 119) " that, if a person were to declare, 
 " that he believes his legs to be made of straw, 
 " and his posteriors of glass, he would not maintain 
 " an opinion, more repugnant to good sense, than 
 " the doctrine of Necessity, when fairly and strictly 
 " examined." Now, as it will not be doubted, 
 that a man, believing that certain parts of his body 
 are composed of the materials here specified, would 
 be regarded as insane, and that his opinion would 
 be considered as a proof of his insanity, it follows, 
 I presume, as a necessary consequence, that a 
 man holding an opinion equally extravagant, 
 equally repugnant to common sense, is also in- 
 sane : Does not your observation justify these 
 conclusions ? 
 
 In pages 305, 6, 7, of your Essay, you tell us, 
 that it appears from an epistle of Seneca's, " that 
 " there were philosophers, in ancient times, who 
 " maintained, that the virtues (which are confes- 
 " sedly motives, or principles of action) were living 
 " creatures, and literally moved, and impelled men 
 " to act in a certain way." You then proceed to 
 give us the arguments from Seneca, on both sides 
 
273 
 
 of this question ; and observing, " that there can 
 "be no occasion to enter into the merits of this 
 " controversy," you say " I presume, if any person, 
 " in the present age, were to assert the opinion, 
 " which Seneca combats so acutely, he would 
 " instantly be pronounced insane." " Yet," you 
 add " it is a speculation, or system, that cor- 
 " responds perfectly to the modern doctrine of the 
 " Necessity of human actions, both in principle, 
 " and style of reasoning." Now, methinks, it 
 does not require much twisting or torturing, to 
 construe this into a charge of insanity against 
 Necessarians. The inference is neither doubtful, 
 nor constrained. Were a man to maintain, that 
 virtues are living creatures, he must be "pronounced 
 insane. Necessarians maintain an opinion perfectly 
 correspondent to this, in principle, and style of rea- 
 soning. Ergo, the inference is pretty clear Ne- 
 cessarians must be pronounced insane. You ask 
 (p. 333.) " If a Mathematician should assert, that he 
 " had constructed a plain triangle, of such curious 
 " proportions, that one side of it was longer than 
 " the other two, and that the three angles of it 
 " were greater than two right angles, and should 
 " undertake to assign a reason for these differences 
 " between his triangle, and all others, and even 
 " demonstrate these strange properties of his trian- 
 " gle," you ask " what would men of science think 
 " of him? or, if a chemist should tell us, that ha 
 Let. S 
 
274 
 
 " had discovered a new fossil, or contrived a new 
 " metal, of such wonderful properties, that, though 
 " it was perfectly inert, and very ponderous, yet 
 " a ball of it projected obliquely to the horizon, 
 " went in a straight line, and with a uniform velo- 
 " city, what should we think of such a chemist ? 
 " It is plain, that both the Mathematician, and the 
 " chemist must be mad." Now, Sir, if these 
 observations are to be transferred to the Neces- 
 sarian, and his hypothesis (and unless so under- 
 stood, they are irrelevant, and nugatory) it is 
 pretty evident, that, if the Mathematician were 
 insane, and the Chemist insane, the Necessarian, 
 whose doctrine you represent, as equally extrava- 
 gant and absurd, must be equally insane. These 
 are the passages, which, in my apprehension, con- 
 vey the indirect charge, which I have ascribed to 
 you. 
 
 The conduct of a practical Necessarian, accord- 
 ing to your conception of his character, is that of 
 an idiot, or a lunatic. After representing him, 
 as " hopping through the world, with one boot off, 
 " and the other on, like Prince Prettyman," you 
 inform your readers, that, " if he escaped the lash 
 " of the law, (which you assure us, you would not 
 " answer for) he would soon be examined by a 
 " commission of lunacy, and instantly pronounced 
 " non compos mentis." 
 
 I have said, that you have indirectly bestowed 
 
275 
 
 indecent appellations on your Necessarian oppo- 
 nents. You find it difficult, it would appear, to 
 understand the meaning of my expression, and 
 refer to me for an explanation of its import, " if it 
 " has any meaning." In the hurry of composition, 
 and the eagerness to censure, it seems to have 
 escaped you, that your own reply furnishes ample 
 evidence, that no explanation is necessary. If 
 the expression conveys no meaning, permit me to 
 ask, how you found it to be significant? If the 
 sentence, or expression be mere words, implying 
 nothing, or if the sentiment be so involved in 
 obscurity, as not to be understood, whence, or 
 how, was it, that you did understand it? Your 
 denial of the charge, which the expression conveys, 
 is irreconcileable with your doubt, that the expres- 
 sion " has any meaning." Will Dr. Gregory be 
 continually at variance with himself? That a 
 charge may be indirectly alleged, or an appellation 
 obliquely bestowed, is one of those plain truths, 
 which, I did not imagine, would be controverted. 
 You find it difficult, it would seem, to comprehend 
 this.- For the sake then of illustration, let us take 
 the following example. When Juvenal says, 
 
 Quis calum terris non misceat, et mare calo, 
 Si fur displiceat Verri, homicida .Miloni ; 
 Clodius accuset machum, Catilina Cethegwn V 
 
 will it be doubted, that he indirectly, or by impH- 
 
276 
 
 cation, brands Verres with the appellation of 
 thief, Milo with that of murderer, Clodius with the 
 appellation of adulterer, and Catiline with that of 
 conspirator? Or, when Thersites says of Aga- 
 memnon, that " he had not so much brain, as a piece 
 of ear wax," and of Diomede, " that the sun would 
 borrow of the moon, when he kept his word," are 
 not the imputations of fatuity and . falsehood as 
 clearly, though indirectly alleged, as if the two in- 
 dividuals had been each stigmatised by the ap- 
 plication of one direct term ? 
 
 But let us select an example from one of your 
 own productions. You accuse an eminent phy- 
 sician, and professor at Edinburgh, of misquotation, 
 and you say, " I protest peremptorily against all 
 " such tricks, and all proceedings founded on them, 
 " as deliberate falsehood, and determined knavery ." 
 It will not, I presume, be doubted, that though 
 certain odious appellations are not here directly 
 applied to the learned professor, the implication 
 is strong, and not to be misunderstood. (See Dr. 
 Gregorys Defence, p. 112.) 
 
 But enough of this nibbling and captious criti- 
 cism. The animadversion might have been dis- 
 missed, as unworthy of notice. 
 
 To substantiate the charge, which has been al- 
 leged against you, I may refer to the passages, which 
 have been already quoted. You have told us fur- 
 ther, that your demonstration carries with it all the 
 
277 
 
 evidence of Mathematical certainty ; and that the 
 false inferences, deducible from our theory, you 
 have demonstrated by the strictest Algebraic de- 
 duction. In connection with this declaration, you 
 ask, what is the most favourable judgment, that 
 we can form of the conduct of one, who, in point of 
 reasoning, acts more irrationally, than a lunatic, by 
 refusing to admit as true, or even probable, an in- 
 ference strictly deducible from the principles, which 
 he asserts. " The most natural, and obvious sup- 
 " position would be, either, that he was incapable 
 " of reasoning, or else, that he did not believe the 
 " principles, he maintained." Is not this telling us, 
 in tolerably plain ter s, that, if we reject your 
 demonstration, we are chargeable with either 
 fatuity, or hypocrisy ? The ground of conviction 
 is obvious. Necessarians maintain certain prin- 
 ciples. Dr. Gregory has mathematically proved 
 that certain inferences result from these principles. 
 Necessarians deny the inferences. The conclusion 
 is evident. 
 
 It is true, that you have not, in express terms, 
 designated Necessarians by the contumelious ap- 
 pellations, to which I allude, but the inference of 
 their applicability is too obvious to be mistaken. 
 And let me remind you of a just observation made 
 by Mr. Hume, in his letter to Dr. Campbell, that 
 " there is very little more delicacy, in telling a man 
 " that he speaks nonsense, by implication than in 
 " {saying so directly." 
 
278 
 
 The charge of disingenuity and falsehood you 
 urge against us frequently and expressly. You 
 tell Dr. Priestley, that your Essay was written, 
 " not merely as a demonstration, that the doctrine 
 " of Necessity is erroneous and absurd, but as a 
 " proof, as complete, and decisive, as ever was or 
 " can be given, of malajides ; that few, if any of 
 "those, who asserted it, had really believed it; 
 " and consequently, that most, if not all the as- 
 " sertors of it, had been guilty of a most shameful 
 " imposition on mankind." Farther evidence it is 
 unnecessary to adduce. 
 
 The imputation of falsehood, you say, must pre- 
 clude the idea of insanity. In this opinion I con- 
 cur with you. These two charges, however, you 
 have evidently, in my apprehension, alleged 
 against us ; with what consistency, it is not my 
 business to explain. 
 
 You seem delighted with the witticism, as you 
 are so kind as to term it, respecting the folly of 
 him, who reasons with a madman. My animad- 
 versions are so rarely favoured with your appro- 
 bation, that, when you express yourself, as " much 
 " pleased" with any of them, I naturally feel a sen- 
 timent of self-congratulation. This sentiment, 
 however, is, I am sorry to say, painfully repressed 
 by my conscious deficiency in that acuteness and 
 penetration, which can discern any characters of 
 wit, in the remark, which seems to have yielded to 
 
279 
 
 you a very high gratification But my vanity is 
 flattered, because you acknowlege yourself pleased 
 with it. 
 
 Principibus plcnuisse viris non ultima lam est. 
 " To please great men is not the meanest praise." 
 
 Whether the correction of the Errata originated 
 with the printer's reader, or with myself, or with 
 any other person, is a subject of speculation, 
 which, from the importance, you have given to it, 
 seems to be of far too great magnitude to be discus- 
 sed at present If your ingenuity should not suc- 
 ceed in solving this grave and momentous enquiry, 
 on some future occasion I may be induced to give 
 you full information. I shall only in the mean time 
 remark, that, if agreeably to Hume's observation, 
 there exists but little difference, between a direct, 
 and an implied imputation, the correction of the 
 Erratum, by inserting the word indirectly, might 
 have been spared as immaterial. Your candid 
 construction of my intention, with the repetition of 
 your wonted charge, are dismissed without reply. 
 
 In the concluding paragraph of your 4th Letter, 
 you hope, I will have the goodness to mention, 
 what monosyllabic term you have applied to 
 Necessarians, not unsuitable to his character, who 
 reasons with a madman. Here I have formally 
 done you injustice ; but the charge is substantial- 
 ly true. You have no where in express terms 
 
280 
 
 applied the name to Necessarians ; but you have 
 affirmed oftener than once, what is essentially 
 equivalent, that no man would think as we think, 
 and profess to believe as we profess, if he were 
 not either incapable of reasoning, or devoid of 
 veracity, that is, either a fool or a hypocrite. 
 The former is, doubtless, the more eligible alter- 
 native. 
 
FROM DR. GREGORY. 
 
 LETTER V. 
 
 SIR, 
 
 JLROBABLY you have not been aware of the in-* 
 consistency into which you fell, in the last and 
 most outrageous part of your Philippic against me, 
 (page 425 of your Essay,) in which you repeat 
 your assertion, that I have attempted to prove that 
 all Necessarians are either fools or lunatics, and 
 express your contempt for that pretended attempt 
 of mine ; and yet, in the same sentence, reproach 
 me, in the most virulent terms, for endeavouring 
 to fix an indiscriminate imputation of dishonesty on 
 my adversaries ; and especially on DR. PRIEST- 
 LEY. But it is necessary to quote your own 
 words : 
 
 " His attempt to prove, that all Necessarians 
 " are either fools or lunatics, can only provoke a 
 "smile; but when he endeavours to fix an indis- 
 " criminate imputation of dishonesty on his adver- 
 " saries, because, forsooth, they will not think as 
 " he thinks, when we hear him, with unexampled 
 
282 
 
 " illiberality and petulance, assailing the most 
 " distinguished Philosopher of the age, and calling 
 " on ' him to vindicate his character, not merely 
 " in point of understanding as a philosopher, but 
 " in point of probity and veracity as a man,' lan- 
 " guage fails us to chastise such insolence, in 
 " terms of sufficient sharpness or severity." This 
 sentence you have illustrated by the following 
 marginal note : " See his vile and scandalous 
 " attack on Dr. Priestley, (Vol. I. p. 284. Introd.) 
 " whose splendid talents, and great moral worth, 
 " combined with the most indefatigable zeal for 
 " the advancement of truth and virtue, far tran- 
 " scend any panegyric in my power to bestow." 
 
 It far surpasses the utmost efforts of my imagi- 
 nation to conceive, how any person, however keen 
 in controversy, or violent in passion, or disin- 
 genuous in conduct, should endeavour to fix on 
 his adversaries, at once, both the imputation of 
 folly or lunacy, and that, still worse, of dishonesty. 
 After the most deliberate consideration, it still 
 appears to me, as it did on first reading your 
 Essay, that the one imputation, whether established 
 by proof, or assumed gratuitously, must preclude 
 the other ; just as certainly as, in a court of jus- 
 tice, the evidence of insanity prevents a conviction 
 for felony ; or as complete evidence of deliberate 
 malice, and wilful murder, sets aside the plea of 
 insanity. In fact, you will find by the whole 
 
<283 
 
 tenor of my Essay, that my imputation of what 
 you call dishonesty, and I call generally malajides, 
 or sometimes disingenuity, in those who profess to 
 believe the doctrine of Necessity, was founded on 
 the observation, that none, of them, as far as I 
 knew, or could learn by information from 
 others, had ever shewn any signs of folly, or 
 lunacy, with respect to the practical application 
 of their own doctrine to the voluntary actions of 
 mankind, in those cases in which the result, in 
 point of overt action, must be different, on the prin- 
 ciple of Necessity, from what it almost certainly 
 will be on that of the Liberty of human actions. 
 The case of equal and opposite motives, and the 
 pretended result of it, the suspension of all action, 
 they themselves had set aside, or explained away 
 in such a manner, that it was .impossible for me to 
 regard their profession of belief in that result as any 
 proof of insanity in them. I was not even entitled 
 to consider it as any evidence of malajides in them ; 
 though it irresistibly excited in me a strong suspi- 
 cion of such disingenuity. I should think even you 
 would admit, that the constantly employing a gra- 
 tuitous hypothesis, to account for the uniform in- 
 consistence of the result, in point of overt action, 
 with the principle assumed, and asserted to be 
 true, is at least unphilosophical, and somewhat aus- 
 picious ; more especially as no such gratuitous hy- 
 pothesis is needed, on account of the failure of the 
 
284 
 
 result of a similar application of causes to lifeless 
 bodies, such as the balance; and as no such 
 hypothesis would be admitted, or even thought 
 worthy of discussion, in any reasonings with respect 
 to the changes produced in subjects that are not 
 supposed to have any self-governing power. 
 
 Consider fairly what your own conduct has been 
 in that outrageous, or, as I think it may justly be 
 called, vile and scandalous attack upon me, and in 
 the manner in which you have quoted some few, 
 suppressing all the rest, of the words of my second 
 letter to DR. PRIESTLEY ; which letter is printed 
 at full length in the Introduction to my Essay ; 
 and in the use which you have made of that imper- 
 fect quotation of what I had written. 
 
 You have taken care to suppress what went 
 before, and what came after ; the knowlege of 
 which preceding and following context was indis- 
 pensably necessary, to enable your readers, or any 
 person not previously well acquainted with the 
 tenor of my Essay, as well as of my conduct to- 
 wards DR. PRIESTLEY personally, to judge whe- 
 ther that strong expression of mine was unnecessary, 
 or in any respect improper. Far from thinking 
 that that expression, seemingly so improper, was 
 a vile and scandalous attack on DR. PRIESTLEY-, I 
 should have thought, and I am convinced every 
 judicious and candid person would have thought, 
 my Essay a vile, scandalous, and insidious attack 
 
285 
 
 on Di*r PRIESTLEY, and on his Brethren, assertors 
 of the doctrine of Necessity, if I had not given 
 them all, and him especially, the strongest possible 
 warning of the nature of the reasoning that I had 
 employed, of the conclusion established by 
 evidence, which I had every reason to believe de- 
 monstrative, and irresistible, in opposition to their 
 favourite doctrine ; and of the very unfavourable 
 corollary, or additional inference, with respect to 
 themselves, and their disingenuity in professing a 
 belief that they never entertained : which corollary 
 results so plainly and obviously from my primary 
 conclusion, that every reader must have perceived 
 it, even if I had carefully avoided pointing it out, 
 or expressing any distrust of the sincerity of those 
 who had professed to believe that opinion, which 
 I undertook to refute. Surely even you must 
 admit that it would be absurd in itself, and dis- 
 graceful and insulting to those philosophers, to 
 suppose them to believe and admit, or even to doubt, 
 and think it necessary to try experimentally, those 
 inferences which I had shewn to be necessary 
 consequences of their own doctrine. You know 
 well what reasons I had for believing that my ar- 
 gument was just and conclusive; particularly, 
 that, in the course of many years, it had been 
 submitted to the revision of all the ablest and best 
 informed men of my acquaintance, especially such 
 
as held the opinion opposite to mine, none of whom 
 could find any error in it. 
 
 All these things are fully explained in my Essay 
 itself; a copy of which, in print, DR. PRIESTLEY 
 had received from me, two years before that letter 
 was written, from which you have selected the 
 strong expressions at present under discussion. 
 Along with, the copy of my Essay, DR. PRIESTLEY 
 received from me a letter, expressed in the most 
 polite and respectful terms; in which I assured 
 him, that if he could point out any error in my 
 reasoning, or give me any objection to it which I 
 could not answer completely, so as to convert it 
 into an illustration of my own argument, I should 
 acknowlege his objection to be valid, and commit 
 my work to the flames. I should think even you 
 must admit, that this conduct, on my part, was 
 candid, and right in every respect, and just what 
 I owed to DR. PRIESTLEY. As, in two years, he 
 gave me no objections to my argument, and indeed 
 took no further notice of my work, and as his friend 
 MR. COOPER, to whom he chose to commit it, 
 after repeatedly promising to give me his objections 
 to it, had never done so ; and as from the tenor of 
 DR. PRIESTLEY'S letter to me, written immediately 
 on receiving my Essay, as well as from that of 
 MR. COOPER'S two letters to me, I doubted whether 
 DR. PRIESTLEY had read my Essay, or even 
 
287 
 
 whether he knew enough of the plan and nature of 
 my reasoning, to be aware, that if he, or his friend 
 MR. COOPER, could not, or would not, point out 
 some error in it, which many men, at least their 
 equals, probably much their superiors, in under- 
 standing and knowlege, could not discover in it, 
 they would, by the publication of my Essay, be 
 convicted of having disingenuously professed a 
 belief which they did not entertain, as well as of a 
 most extravagant error in reasoning : I therefore 
 thought it incumbent on me, once more, to write 
 to DR. PRIESTLEY, to inform him how his friend 
 MR. COOPER had trifled with me ; to tell him the 
 nature and plan of my reasoning ; to illustrate that 
 general account of it by a supposable particular case* 
 exactly parallel to the real one, and very minutely 
 detailed ; to warn him, in the most explicit terms, 
 of the very unfavourable inference, with respect to 
 himself and his brethren, to which they would be 
 exposed, unless he or they could point out some 
 error in my argument ; but, at the same time, to 
 assure him, that I should be very sorry to do him 
 any injustice, or even to fail in that respect to him, 
 to which his character, and his zeal and activity 
 in the pursuits of physical science, well entitled 
 him ; to point out to him, that for him not to answer 
 and refute such a charge, as was necessarily implied 
 in my argument, after he had had ample time to 
 consider it, was to acquiesce in it ; and, finally, to 
 
288 
 
 repeat my offer, to acknowlege his superiority in 
 reasoning, to thank him for the very great favour 
 he should do me, and to suppress my work, if he 
 could detect any error or fallacy in it, and to pub- 
 lish, either in the Introduction or in the Appendix 
 to my Essay, any remarks on it, or objections to 
 it, with which he, or his friend MR. COOPER, 
 should favour me, and which I should not think 
 valid. 
 
 The whole context of that letter of mine to DR. 
 PRIESTLEY must have been as well known to you 
 as the few words of it which you have quoted ; 
 and which, if they had been all that I addressed to 
 DR. PRIESTLEY, would have been highly improper 
 and indecent ; and completely disgraceful, not to 
 him, but to myself. The same words, taken along 
 with the full context of my discourse, appear to 
 me strictly candid, and honourable to us both. 
 If, on mature consideration, you think so too, I 
 hope you will have the candour to say so, and to 
 acknowlege the injustice you have done me, in 
 that most reproachful paragraph of your Essay. 
 But if you shall choose to adhere to your original 
 invective, which I presume will be the case, I 
 wish you would take the trouble to analyse a little 
 your ozen opinion, real or pretended, of me and my 
 conduct, as expressed in that paragraph of your 
 Essay. I need not tell you, that a complicated, 
 perhaps a confused proposition, may appear plan- 
 
sible, or almost self-evident, when expressed in 
 general terms, and without being distinguished, or 
 resolved into its constituent parts ; which proposi- 
 tion, when duly analysed, will be found to contain, 
 or imply, so many things, that are either false, 
 frivolous, or vague, that the whole, composed of 
 such parts, must be either incredible or nugatory. 
 
 For example ; Do you seriously believe, and 
 mean to assert, that it is impossible for any person, 
 even for a philosopher, to be guilty of disingenuity 
 and falsehood, by professing to believe a sophism 
 which he really did not believe, but was unable to 
 detect? 
 
 Do you mean to say, that such disingenuity and 
 falsehood with respect to a philosopher's own 
 thoughts and belief, can never be hurtful in science, 
 and especially in the science of the human mind, 
 most of the facts relating to which must ultimately 
 be established by a kind of appeal to consciousness, 
 or by strict attention to our own thoughts ? Do 
 you mean to say, there is no evidence, and no pre- 
 sumption of disingenuity, on one side or the other, 
 when different philosophers, or different persons, 
 whether philosophers or not, after attending, or 
 professing to attend, strictly and candidly, to their 
 own thoughts, on a plain and familiar, but inter- 
 esting subject, give directly contradictory accounts 
 or testimonies of their thoughts and belief with re- 
 spect to that subject? 
 
 Let. T 
 
290 
 
 Do you think such contradictions can be ac- 
 counted for in a fair and satisfactory manner, on 
 the supposition of a real unalterable difference in 
 the mental constitutions of different individuals of 
 mankind ; implying, that all of them who contra- 
 dict one another the most directly, are equally 
 candid and sincere in what they assert, but that 
 the point in dispute between them never can be 
 settled by any competent evidence, and is, bona 
 jidc, beyond the reach of the human faculties ? 
 
 If you mean to assert any or all of these pro- 
 positions, I trust you will have no objections to 
 say so explicitly, and to specify precisely what 
 your creed is, with respect to those general 
 preliminary points or principles, which must be 
 settled one way or another, before you or any 
 person can be entitled to say that I did either 
 right or wrong, wisely or foolishly; in attempting 
 to convict of disingenuity and falsehood those 
 philosophers who had professed their belief in 
 the doctrine of Necessity. If you admit that 
 philosophers may be guilty of disingenuity and 
 falsehood in the account which they give of their 
 own belief with respect to certain controverted 
 points in the philosophy of the human mind, and 
 that such disingenuity may be hurtful, by corrupt- 
 ing science, and retarding its progress, and that 
 direct contradiction among different philosophers, 
 with respect to their belief on points of familiar and 
 
291 
 
 interesting thought, or immediate consciousness, 
 and daily experience, affords, if not complete evi- 
 dence, at least a 'very strong presumption of such 
 disingenuity, on one side or the other ; and if you 
 admit that the human faculties are competent to 
 the investigation and decision of such a question, 
 implying, that those faculties are uniform in their 
 nature and operation in all mankind who have 
 attained competent judgment and knowledge; aU 
 which suppositions are possible, and I think nowise 
 unfavourable to you ; then I would proceed to ask 
 you, 
 
 Do you think it would be right to discover on 
 which side, in any such controversy, the falsehood 
 lay, and to detect, and expose to just censure, 
 those who have been guilty of it ? 
 
 Or do you think such falsehood, though pernici- 
 ous in science, ought to be carefully concealed, and 
 never corrected, and that those who have been guilty 
 of it ought to be treated with profound respect ? 
 
 If you admit that such falsehood ought to be dis- 
 covered and corrected, and that those who have 
 employed it ought to be exposed to just censure, 
 which, I presume, 772 ust be your opinion, and pro- 
 bably also would be your practice, with respect to 
 those whose doctrine and professed belief is adverse 
 to yours, if you should find any evidence of such 
 misconduct on their part ; then I would ask you, 
 
 What kind of evidence do you think would be 
 
293 
 
 as a direct demonstration ? Or, in other words, Do 
 you admit the axiom of logic, that a proposition 
 directly contradictory to one that is false must be 
 true? 
 
 Do you think a philosopher may rationally and 
 candidly refuse his assent to such a demonstration, 
 without shewing some error in it ? 
 
 If you admit the general principles implied in 
 these queries, then I would ask you, 
 
 Do you think DR. PRIESTLEY or his friends 
 have any peculiar or personal exemption from those 
 rigorous laws of human thought, or principles of 
 reasoning and conduct, which, from the earliest 
 ages of science, have been considered as universal 
 and indefeasible ? 
 
 Supposing, for the sake of argument, Du. 
 PRIESTLEY, and his brethren, assertors of the 
 doctrine of Necessity, to be, bonajide, so completely 
 exempted from those laws of human thought which 
 have generally been deemed essential to all strict 
 demonstrative reasoning, that they can really be- 
 lieve a principle or doctrine, and yet perceive in- 
 tuitively that the necessary consequences of it are 
 ridiculously false and absurd ; Do you think they 
 would be fit to be reasoned with ? Or on what 
 principles, and in what manner, ought one to at- 
 tempt to reason with them ? 
 
 Supposing, still, that such is their peculiar si- 
 tuation and exemption, was it not incumbent on 
 
. 292 
 
 sufficient to establish such an unfavourable conclu- 
 sion, with respect to men who professed and called 
 themselves philosophers ? 
 
 Do you think it would be rational or proper to 
 admit of appeals to consciousness in such a dis- 
 cussion, either for or against the suspected philo- 
 sophers ? 
 
 Or do you think it would be right to set aside, 
 as I have done, all appeals to consciousness, as 
 incompetent and unavailing? 
 
 t)o you think, that the same kind of evidence 
 which is held sufficient to convict a witness of per- 
 jury in a court of justice, I mean deliberate inconsis- 
 tency, would be sufficient to convict such philoso- 
 phers of d is ingenuity ? 
 
 Do you think, that it would be inconsistency in 
 those philosophers, if they should perceive at once, 
 and intuitively, the falsity of many practical infer- 
 ences, shewn to be necessary consequences of their 
 own doctrine, in certain supposable cases, which 
 might easily be brought to the test of open unequi- 
 vocal experiment ? 
 
 Do you know of any higher evidence in science 
 than demonstrative reasoning, founded on axioms, 
 or self-evident necessary truths, and proceeding, by 
 necessary consequences at every step, to the ultimate 
 conclusion which it was intended to prove ? 
 
 Do you admit, that an argumenium ad absurdum, 
 supposing it to be good of its kind, is just as valid 
 
294 
 
 them to plead their privilege in that respect, when 
 I invited, and most strongly urged them, either to 
 admit my conclusions, which seemed to be fairly 
 and strictly deduced from their own doctrine, or 
 else to shew that there was some error in my de- 
 duction ; and when I warned them, that unless 
 they did the one or other of these things, they must 
 ipso facto, I mean, by their silent acquiescence in evi- 
 dence seemingly complete and decisive against 
 them, incur the most unfavourable censure, and 
 be at last loudly called upon to vindicate their 
 character, not only in point of understanding as 
 philosophers, but in point of probity and veracity as 
 men ? Is not your own Essay, I mean especially 
 that part of it which relates to me and my Essay, 
 a complete proof that I was right in that opinion, 
 and that you soon found it necessary to attempt 
 (what you never can accomplish) such a vindica- 
 tion of your great master, and of his doctrine? Is 
 not DR. PRIESTLEY'S own conduct, in professing 
 to approve of your Essay, and urging you to print 
 it,, knowing, as he must have done, whatever you 
 may do, that it is composed in open violation of the 
 most familiar and best established principles of rea- 
 soning, as well as with consummate disingenuity 
 towards me, a very strong additional proof of the 
 same thing? Is not that conduct of DR. PRIEST- 
 LEY complete evidence, that he was not (as he pre- 
 tended, and I did not believe) perfectly indifferent 
 
295 
 
 to such charges as that of mala fides ; and that he 
 too felt the irresistible necessity of getting his cha- 
 racter, if possible, vindicated, per fas autnefas ? 
 
 As neither DR. PRIESTLEY himself, nor any of 
 his meanest parasites, ever did, or ever will main- 
 tain, that he has any such exemption from the 
 common laws of human thought and moral conduct, 
 and as, in all probability, he and his flatterers also 
 will regard such a supposition, not as a compliment, 
 but as an insult, it may be thought improper, as 
 well as needless in me, to have considered so 
 minutely that strange supposition. I have done 
 so, for this reason ; it appears to me, that it is only 
 on some such supposition, not openly avowed, or 
 expressed in words, but tacitly assumed as one of 
 their principles of judgment, that DR. PRIESTLEY, 
 or his flatterers, can have even a pretence for blam- 
 ing me on account of my procedure towards him. 
 If his principles of reasoning were the same 
 with those of other men ; if, like other men, he 
 might be supposed, not only subject to error, but 
 capable of disingenuity and falsehood ; if, in him, 
 as in other men, deliberate inconsistency, espe- 
 cially perceiving intmtwdy> so as to supersede the 
 necessity of any experiment, the falsity of the ne- 
 cessary consequences of that doctrine, which he 
 not only had professed to believe in general, but 
 had illustr ated by precise examples, and had -as- 
 serted with the greatest arrogance, and very strong 
 
206 
 
 expressions of contempt for those who differed in 
 opinion from him ; if such inconsistency would be 
 evidence of falsehood on his part, and if such false- 
 hood would be disgraceful to himself, and perni- 
 cious to the interests of science; I cannot conceive 
 what reason or pretence he, or any parasite of his, 
 can have to blame me for giving him a fair oppor- 
 tunity, and even inviting and urging him, in the 
 strongest manner, to prevent such a charge from 
 being brought against him, if he thought it unjust, 
 or even the proof of it incomplete. 
 
 He had in his possession complete evidence, I 
 mean myjfirst letter to him, that I did not wish to 
 do him any injustice. My patient forbearance for 
 two years, and my second letter to him, the purport 
 of which you have so grossly misrepresented, by 
 suppressing more than ninety-nine parts in the hun- 
 dred of its contents, and indeed the whole tenor of 
 it, must have afforded him additional, and, of 
 itself, complete evidence, that my sentiments to- 
 wards him remained the same : that I was most 
 anxious to preclude even the possibility of my 
 doing him any injustice, and that I was, to the 
 last, willing to acknowlege his superiority in rea- 
 soning, and to suppress my work, if he could shew 
 me any error in my argument. The nature and 
 plan of my mode of reasoning were fully explained 
 to him; and illustrated by a very apposite example, 
 which he could not fail to understand, as well as 
 
297 
 
 to perceive the irresistible force of the necessary 
 inference to which it led. 
 
 It was explained to him, that my argument was 
 given as a demonstration, of the strictest kind ; 
 beginning with self-evident necessary truths ; pro- 
 ceeding, by necessary consequences at every step, 
 to the ultimate conclusion which I undertook to 
 establish; and leading also, irresistibly, to that 
 unlucky corollary at which you pretend to take 
 such grievous offence; but which I thought myself 
 bound, in point of candour, probity, and veracity, 
 to point out to DR. PRIESTLEY in the plainest 
 manner. 
 
 He must have perceived, even from that brief 
 account of the nature of my argument, what you 
 know I acknowlege most explicitly in my publi- 
 cation, that my Essay must be either that strict 
 demonstration which I supposed it, or else stark 
 nonsense of the most extravagant kind. Supposing 
 it to be nonsense in itself, as well as unjust to him 
 and his brethren, it must have been easy for him 
 to discover where my error lay, and to point it out 
 to me in such a manner as to preclude all doubt 
 or dispute about it. Any error in such an argu- 
 ment must be gross and palpable. 
 
 He was fully informed of the reasons I had for 
 believing that there was no error in my argument t 
 not my own opinion alone, formed after the most 
 deliberate consideration, nor yet the concurrent 
 
298 
 
 opinion of many of the ablest and best informed 
 men in this country, and of his friend DR. PRICE, 
 but the strange conduct, to say no worse of it, of 
 all the ablest and keenest assertors of the doctrine 
 of Necessity with whom I was acquainted, some 
 of them good mathematicians ; not one of whom 
 would acknoivlege the validity of my argument, 
 and yet not one of them could point out any error 
 in it ; nor give me any objections to it, but such 
 as I should most gladly have published, with my 
 answers to them, in illustration of my own mode 
 of reasoning. 
 
 DR. PRIESTLEY was informed of the strange 
 conduct of his friend and proxy MR. COOPER, to 
 whom he had sent the copy of my Essay, that'he 
 received from me; which MR. COOPER seems to 
 hav.e read, and to have thought, at first, he could 
 easily answer; at least he told me so, and promised 
 to give me his answer; and even repeated that 
 promise some months afterwards ; but never kept 
 it, or gave me any reason for his not keeping it, 
 the second time that he made it. 1 informed DR. 
 PRIESTLEY of this conduct of his friend MR. 
 COOPER ; which, however strange it may appear 
 to many persons, appeared neither unaccountable 
 nor wonderful to me, after what I had experienced 
 from some of his Brethren Necessitarians. I told 
 DR. PRIESTLEY, explicitly, what interpretation I 
 put upon it, namely, that MR. COOPER, on mature 
 
299 
 
 consideration, could contrive no objections, which 
 he himself thought valid, or decently tenable, 
 against my argument. 
 
 In these circumstances, it seemed to me perfectly 
 candid, and not unreasonable, to invite and urge 
 DR. PRIESTLEY to consider my argument, which so 
 nearly concerned himself, and either acknowlege 
 it to be valid, or show the error of it, so as to pre- 
 vent my doing him any injustice by publishing it. 
 
 Surely it must have been very easy for DR. 
 PRIESTLEY, or MR'. COOPER, to have pointed out 
 the errors of my argument, and of my conduct, if 
 they had been liable to such objections as those 
 which you have urged against them. MR. COOPER 
 could have had no occasion to break his promise, 
 and shrink from that discussion which he himself 
 had voluntarily undertaken, if I had declared that 
 all Necessitarians were lunatics ; if I had imputed 
 to them, or asserted that any of them had main- 
 tained, or admitted, those absurd inferences which 
 I had shown to be necessary consequences of their 
 own doctrine ; and if an argumentum ad absurdum 
 could be answered and refuted by reviling the au- 
 thor of it, and declaring vehemently that those in- 
 ferences were false or absurd, which he had given 
 as such, but, withal, as necessary consequences of 
 that supposition which he undertook to disprove, 
 in order to prove the proposition directly contra- 
 dictory to it. 
 
300 
 
 To me it appears abundantly plain, that neither 
 DR. PRIESTLEY nor MR. COOPER, nor any man, 
 however keen a Necessitarian, who had, or ex- 
 pected ever to have, any credit, either in point of 
 understanding and knowlege, or in point of probity 
 and veracity, would ever have attempted or pre- 
 tended to give such an answer to my argument, 
 or would ever have put his name to such a publi- 
 cation. 
 
 To me it appears abundantly marvellous, not 
 that DR. PRIESTLEY should be well pleased to see 
 my argument misrepresented, and myself reviled 
 in the grossest manner, by an author superior to 
 all vulgar considerations of truth and reason, or 
 even of credibility ; but that he should forfeit any 
 pretensions, he himself might have, to candour 
 and veracity, by expressing his approbation of such 
 a work, and urging you to publish it, and after- 
 wards approving of your conduct in doing so, 
 without first allowing me to peruse it, and to have 
 an opportunity of either acknowleging the validity 
 of your argument, and the error of my own, or 
 else of pointing out to you what I conceived to be 
 erroneous, disingenuous, or unjust to me, in your 
 reasoning. For the truth of that marvel, however, 
 you must answer, not I : nor can you blame me, 
 for giving you full credit for veracity in that respect; 
 but remember that the chief object of these Letters 
 to you is, not to remonstrate with you on the tin- 
 
301 
 
 reasonableness, disingenuity, and injustice of your 
 conduct towards me ; nor yet to tell you all the 
 remarks which 1 mean to make on that part of 
 your Essay which relates to my argument ; but 
 only to give you an opportunity of explaining, 
 correcting, or vindicating, if you think you can do 
 it, those parts of your answer to my argument 
 which are to be the subjects of my remarks. Though 
 perfectly willing, and, as you shall soon find, 
 equally able, to dissect and anatomise you secundum 
 artem, I am very unwilling, for my own sake as 
 much as yours, to do you any injustice. You 
 shall have the same opportunity that DR. PRIEST- 
 LEY had, of seeing what I mean to publish against 
 you, with the assurance that it shall be suppressed, 
 and committed to the flames, if you can show any 
 error in my reasoning. You shall also have an 
 opportunity of preventing me from doing you any 
 injustice, by mistaking your meaning on any point, 
 or putting any interpretation on your conduct, 
 which interpretation, however obvious, you might 
 think unfavourable or unjust. 
 
 I hope you will make a better use of these 
 opportunities than DR. PRIESTLEY did of similar 
 opportunities given by me to him. If you do not, 
 it must at least appear that the fault is your's, not 
 mine. 
 
REPLY 
 
 TO LETTER V. 
 
 JL N reference to the charges, which I have repre- 
 sented you as alleging against us, you observe; 
 " It far surpasses the utmost efforts of my imagin- 
 " ation to conceive, how any person, however 
 " keen in controversy, or violent in passion, or 
 " disingenuous in conduct, should endeavour to 
 " fix on his adversaries at once both the imputation 
 " of folly, or lunacy, and that still worse, of dis- 
 " honesty." And you observe, that the one im- 
 putation must preclude the other, which observation 
 you proceed to illustrate. 
 
 It requires, I presume, no extraordinary effort 
 of imagination to conceive, that a polemic, " keen 
 " in controversy, and violent in passion," may 
 allege against his opponents inconsistent charges. 
 Nor would it be a difficult task to prove the exis- 
 tence of such inconsistency by positive facts, or to 
 unfold the causes, by which it is produced One 
 or two examples will present themselves to our 
 attention, before we shall have examined the re- 
 mainder of your defence. 
 
303 
 
 The charge of dissimulation and falsehood is so 
 frequently repeated, and so expressly urged, that 
 it cannot have escaped the recollection of the 
 reader. In evidence of the other opprobrious impu- 
 tation, I must refer to the passages, which have 
 been extracted from your Essay. (See p. 272.) That 
 fatuity and falsehood are often combined in one 
 character, is admitted to be true, even to a com- 
 mon adage. If I have misconceived the import o^ 
 the passages, to which I allude, by assigning to 
 them an application, which they do not warrant- 
 ably bear, and misrepresenting you, as alleging 
 inconsistent charges against Necessarians, I feel it 
 my duty to express my sincere regret, and at the 
 same time to assure you, that the error, if there 
 be any, was wholly unintentional. A reference 
 to the extracts will convince the impartial reader, 
 that there exist strong grounds, if not decisive 
 evidence, for rny allegation against you. 
 
 You complain of my conduct as reprehensible 
 in quoting " some few, and suppressing all the 
 " rest, of the words of your second Letter to Dr. 
 " Priestley." I am desirous to know, and request, 
 that you will specify, what I have suppressed, 
 which can even extenuate, much less justify, your 
 rude and illiberal attack. Your charge of deliber- 
 ate falsehood, and consummate hypocrisy, alleged 
 against Necessarians in general, must be pro- 
 nounced highly discreditable to your character 
 
304 
 
 both as a philosopher, and as a man. Some of 
 your friends, it would seem, felt it their duty to 
 remonstrate with you, against such illiberal and 
 injurious imputations. One gentleman, in parti- 
 cular, whose sentiments and character you admire, 
 admonished you of the impropriety of imputing 
 falsehood to an adversary, not only on account of 
 the odious nature of the charge itself, but also 
 because he doubted the truth of your offensive 
 conclusion But you would not listen to counsel. 
 You were determined your adversaries should as- 
 sent to your argument, or be branded with the 
 most dishonourable of all imputations. Accord- 
 ingly, while you are dealing this illiberal charge 
 around you, Dr. Priestley, in common with other 
 Necessarians, is particularly assailed. You tell 
 him, " that your Essay is given, not merely as a 
 " demonstration, that the doctrine of Necessity is 
 " erroneous and absurd, but as a proof (as com- 
 " plete, and decisive, as ever was or can be given 
 " of mala fides in any case) that few, if any, of those, 
 " who asserted it, had really believed it, and 
 " consequently, that most or all of the asserters 
 " of it had been guilty of a shameful imposition on 
 " mankind!' You tell him, that " in your Essay he 
 " will find himself loudly called upon to vindicate his 
 " character, not merely in point of understanding, as 
 " a philosopher, but in point of probity and veracity, 
 " as a man!' Now, I wish to be informed, what 
 
305 
 
 you have said, which I have suppressed, that can 
 extenuate, much less justify this opprobrious attack. 
 You are pleased to lay a mighty stress on your 
 having apprised him of your mode of reasoning, 
 and your intended assault. Pray, Sir, does the 
 intimation of an odious charge render that charge 
 less offensive, or less reprehensible ? Is there any 
 tribunal, human, or divine, where so weak a de- 
 fence would be deemed a vindication? Would 
 the act of the homicide be justifiable, because he 
 had forewarned his victim of his intention, and the 
 mode of effecting it ? Or, if the intimation should 
 enable the latter to frustrate the purposes of the as- 
 sassin, would Dr. Priestley's objections have 
 availed to repel your charge? Would they have 
 shared a better fate, than the arguments of your 
 other opponents ? Would they not, like them, have 
 been pronounced by Dr. Gregory to be " admira- 
 ' ble illustrations" of the validity of his reasoning? 
 
 You may, perhaps, reply, that you not only 
 apprised Dr. Priestley of your intended charge, 
 and your mode of proving it, but that you have 
 actually proved it. Refer me, I beseech you, to 
 that part of your Essay, where this proof is to be 
 found. How have you proved it? By evincing 
 the falsity of our hypothesis ? Be it granted, for 
 the sake of argument. Is the falsity of our doctrine, 
 and the truth of your imputation, one and the 
 same thing ? Is a demonstration, if it must be so 
 Let. U 
 
306 
 
 called, that the Necessarian hypothesis is absurd, 
 a demonstration also, that Dr. Priestley was 
 chargeable with disingenuity and falsehood ? Are 
 the propositions identical ? or will one proof serve 
 for both especially, as you maintain, that Dr. 
 Priestley was a man, who, " there is reason to 
 " think had little taste for Mathematical reasoning, 
 " or indeed strict reasoning of any kind T You 
 cannot be so deficient in penetration, as not to 
 perceive the distinction. This defence would not 
 avail you. 
 
 But it will be denied by every competent judge 
 of the question, that your argument does prove the 
 falsity of our doctrine It is vicious in its principle, 
 and wholly fallacious. Nor can I sufficiently 
 express my amazement, that an argument, so re- 
 pugnant to the clearest principles of scientific 
 reasoning, and metaphysical science, should ever 
 have been regarded by you, as a Mathematical de- 
 monstration. Were it such, where is the man, 
 who would venture to reject it, knowing, that he 
 might as well refuse his assent to a proposition of 
 Euclid. Firmly as I believed, and do still believe, 
 in the doctrine of Necessity, I felt no interest, in 
 maintaining it, any farther, than I love and ad- 
 mire, what I conceive to be truth. This hypo- 
 thesis, however, I had not publicly advocated, 
 and had therefore neither character nor interest 
 involved in the controversy. Say then, what 
 
307 
 
 rational motive you conceive I had, to dispute 
 the accuracy of your demonstration? Nay, how 
 is it possible to dispute a conclusion deduced with 
 mathematical precision from incontrovertible pre- 
 mises? The supposition is inadmissible. Yet we 
 find not only, that Necessarians still reject your 
 conclusion but that several Libertarians deny your 
 argument to be a demonstration. Can that then 
 he demonstrative evidence, which produces un- 
 certainty, nay even dissent ? Can that be demon- 
 stration whieh leaves a vestige of doubt, on any 
 rational mind? It is truly observed by one of 
 your correspondents, "that his remaining uncon- 
 " vinced by it was some ground of suspicion 
 " against it, since he could discover nothing in his 
 " situation, or sentiments, that should lead him to 
 " suspect, he had imbibed any invincible prejudice 
 " against it; and, if it were solid, he thought that, 
 " notwithstanding any degree of prejudice, it ought 
 " to produce infallibly the same degree and facility 
 " of conviction, that results from a theorem in 
 " Geometry." The observation is pertinent, and 
 would convince any man, but the author of the 
 demonstration, that the argument cannot possibly 
 be demonstrative. Who ever heard of a man dispu- 
 ting the truth of a demonstration in Euclid ? The 
 very fact therefore, that this demonstration of yours 
 was actually rejected by many, and doubted by 
 others, should have taught you its true and genuine 
 
308 
 
 character It should have taught you to doubt its 
 validity. It should have taught you to speak with 
 less arrogance, and in a humbler tone, of its su- 
 perlative merit. It should have taught you, above 
 all, to treat your opponents with more liberality, 
 and to abstain from offensive, and injurious impu- 
 tations. 
 
 I do not mean to affirm, that no case can occur, 
 in which a person might be in some degree justified 
 in imputing mala Jides to his adversaries ; but I 
 contend, without fear of contradiction, that such 
 cases are as different from yours, as truth from 
 error, wisdom from folly. With your permission I 
 will put a case which might possibly warrant such 
 a charge. I shall suppose, that a controversy has 
 existed among philosophers and men of science for 
 several ages, and that the learned world, during 
 that period, have been nearly equally divided in 
 their opinions respecting it. I shall suppose, that 
 all at once up starts some great philosophical and 
 mathematical genius, who shews demonstrably, 
 that one of the two hypotheses is not merely false, 
 but absurd, and that he proves this, to the entire 
 satisfaction of every man of science in the world, 
 nay of every man capable of reasoning, one single 
 person only excepted. I shall suppose, that this 
 person still maintained his former opinion, and still 
 persisted in his favourite error. Now, in such a 
 case, I admit, there would be considerable ground 
 
309 
 
 for suspecting his veracity. But even here, I con- 
 fess, I should hesitate to charge him with mala 
 fides. If I understood, that his interest was con- 
 nected with the belief of this error, if I were cer- 
 tain, that his conduct, in general, was not regulated 
 by the strict principles of morality and religion, 
 my suspicions of his insincerity would amount 
 nearly to conviction. But, if I knew him to be a 
 man, strictly honest and conscientious in all his 
 actions, if I knew him to be impressed with a sense 
 of religion, and a love of truth, how extraordinary 
 soever his conduct might appear, and how inexpli- 
 cable soever on the common principles of human 
 reasoning, I should impute his dissent to any cause, 
 rather than to deliberate falsehood or disingenuity. 
 If I knew nothing of his character, I ought to 
 judge favourably of his motives -It may be safe to 
 know without judging ; but not to judge without 
 knowing This is one of the strongest cases, 
 which can well be supposed How widely dif- 
 ferent is the effect produced by your demon- 
 stration I doubt much, if it has produced a 
 single convert to your hypothesis But let us re- 
 turn to our case. 
 
 I have supposed, that this philosopher and ma- 
 thematician has thrown such a light on the subject 
 of controversy, that a truth once obscure and con- 
 testable, shines forth with all the lustre of demon- 
 strative evidence. I have supposed, that no man 
 has rational grounds for questioning the accuracy 
 
310 
 
 of his argument, and that the world is completely 
 enlightened by his reasoning. I will even suppose, 
 that he is justified in charging the dissenting soli- 
 tary individual with mala fides. But what should 
 we say, what should we think of him, were he to 
 charge all those, who have existed on this globe, 
 from the creation of man, to the present hour, and 
 who never heard of his argument, with dissimula- 
 tion and falsehood? 
 
 Is there an individual, possessed of the least 
 portion of common charity is there a man, who 
 entertains the smallest regard to truth and candour, 
 who would not reprobate the imputation, as ab- 
 horrent to every sentiment of justice, repugnant 
 to one of the first duties, which reason inculcates, 
 and religion prescribes ? Yet such has been your 
 conduct. You not only charge those with disin- 
 genuity and deliberate falsehood, who shall ex- 
 amine your argument, and reject your conclusion, 
 but the major part, if not all, of those, who have 
 ever believed in the doctrine of Necessity. Im- 
 pressed with a conviction of the validity of your 
 argument, and its irresistible force, hurried away 
 by intemperate feeling, and precipitate judgment, 
 you may find some apology for stigmatising us, 
 who have rejected your demonstration, as thorough- 
 paced dissemblers, but forbear, we intreat you, to 
 load with reproaches those departed spirits, who 
 were never visited with the light of your demon- 
 
311 
 
 stration, nor could assent to an argument, which 
 they had never heard. Designate us, on whom 
 the beams of your genius have shone in vain, and 
 who love darkness rather than light, by any de- 
 grading appellation, which language may supply ; 
 but spare, we beseech you, spare those, in whose 
 ears never vibrated the sound of your demonstra- 
 tion. 
 
 Permit me to offer one remark farther. Though I 
 am extremely unwilling to disturb your self-com- 
 placency, or to lessen you one tittle in your own 
 estimation, I must take the liberty to observe, 
 that of all men,^ that I know, you seem to me to 
 be the least qualified to form a correct opinion of 
 other men's belief, and therefore least justified in 
 charging them with disingenuity, or falsehood. 
 I have presumed to say, that I think your reason- 
 ing false. You do not believe me. I have said, 
 your argument is inconclusive, You do not believe 
 me. I have ventured to state it as my opinion, 
 that your illustrations are frequently inapposite. 
 You do not believe me. Now all these opinions 
 of your Essay I bona Jide maintain, yet you will 
 not be persuaded, that I really hold any one of 
 them. To judge of the sincerity of other men's 
 belief, seems to be one of those offices, to which 
 your mental constitution is peculiarly ill adapted. 
 
 You say, " If on mature consideration you* 
 
312 
 
 " think, that the words in question, taken along 
 " with the full context of my discourse, appear to 
 "you, strictly candid, and honourable to me and 
 " Dr. Priestley, I hope, you will have the candour 
 " to acknowlege it." Thus called upon, to express 
 my opinion, I should merit the severest reprehen- 
 sion, were I to dissemble my real sentiments. It 
 is not my disposition to do you, or any person, in- 
 justice; and if I have, in any instance injured 
 your argument, or mis-stated your meaning, which, 
 I am conscious, I have not intentionally done, I 
 shall feel a pride in acknowleging it. Your man- 
 ner of treating your opponents, in this, and every 
 other controversy, must be admitted by your best 
 friends, to be too strongly characterised by inso- 
 lence and an intemperate spirit, displaying almost 
 a total destitution of that liberality, which is the 
 soul of greatness, and the friend of truth. And I 
 candidly confess, that, indignant at the rude and 
 offensive imputations, which you laboured to fasten 
 on your Necessarian opponents, I may have re- 
 torted upon you, with a degree of sharpness and 
 acrimony, which a temperate and calm revision of 
 my work would probably have softened. This 
 candid confession, will, I trust, furnish you with a 
 satisfactory proof of my sincerity on the present 
 occasion. You will, therefore, I hope, believe 
 me, when I declare, that after a most attentive per- 
 
313 
 
 usal of your letter to Dr. Priestley, I can perceive 
 nothing, which it contains, that can, in the least 
 degree, justify your attack. 
 
 But I must not dismiss the subject, without 
 adverting to the example, which, it appears to 
 me, you have furnished, of an author, endeavour- 
 ing to fix on his adversaries inconsistent charges. 
 You have, in your Essay, imputed to Dr. Priestley 
 a deficiency of talent for Mathematical demonstra- 
 tion, and have represented him, as a person, who 
 " had little taste for strict reasoning of any kind." 1 
 You have represented him also, as being " insen- 
 " eible to argument." You have charged him, at 
 the same time, with disingenuity, in professing to 
 believe in the hypothesis of Necessity. These im- 
 putations, one with the other, it appears to me 
 difficult, if not impossible, to reconcile. If he 
 was really deficient in capacity for comprehending 
 strict reasoning of any kind, and was, in truth, 
 insensible to argument, I should apprehend, that 
 his intellectual impenetrability would serve to 
 acquit him of disingenuity and falsehood. If, on 
 the contrary, he clearly perceived the validity of 
 those arguments, by which his hypothesis was 
 refuted, he might incur the charge of dissimulation 
 and falsehood, but must be absolved, I apprehend, 
 from the imputation of insensibility to argument, 
 
 1 See Introduction, p. 302. 
 
314 
 
 or of a deficiency of talent for strict reasoning. lit 
 short insensibility to argument must acquit him 
 of disingenuity ; and disingenuity must absolve 
 him from the charge, that he was insensible to 
 argument. It must be admitted then, I conceive; 
 as a fact, how problematical soever it may seem to 
 you, that it is possible for a controvertist to allege 
 against his opponents inconsistent charges. 
 
 You ask me, if I seriously believe, and mean to 
 assert, that it is impossible for any person, even 
 for a philosopher, to be guilty of disingenuity and 
 falsehood, by professing to believe a sophism, which 
 he really did not believe, but was unable to detect. 
 
 This question regards a point too clear to be 
 obscured, and too simple to be perplexed by any 
 casuistry. Veracity is the conformity of words to 
 thoughts. If a philosopher professes to believe 
 that, which he does not believe, whatever specious 
 sophistry he may oppose to his own conviction, he 
 is chargeable with a violation of moral truth. But 
 no man can be guilty of falsehood, who believes, 
 what he professes to believe. His conviction may 
 be founded in error ; its basis may be a sophism ; 
 but error is not falsehood ; and while that error, 
 or that sophism, has escaped his detection, and 
 while he firmly believes, what he professes to be- 
 lieve, he may claim the merit of sincerity, as much 
 as he, whose opinion is correct, and whose decla- 
 ration is consonant with that opinion. No error 
 
315 
 
 can appear to me more palpable than the doctrine 
 of Transubstantiation ; but I should deem myself 
 guilty of a flagrant breach of charity, if I imputed 
 mala fides to all those, who have believed, or may 
 still believe, that tenet. A person, professing to 
 believe, what he does not believe, whether that 
 belief be well or ill founded, is guilty of false- 
 hood. 
 
 You ask me, whether I think, that such disin- 
 genuity and falsehood can be hurtful to science, 
 I answer in the affirmative. 
 
 You ask, whether " / mean to say, there is no 
 *' evidence and no presumption of disingenuity on 
 " one side, or the other, when different philosophers, 
 " or different persons, whether philosophers or not, 
 " after attending, or professing to attend, strictly 
 " and candidly, to their own thoughts, on a plain 
 " and familiar, but interesting subject, give directly 
 " contradictory accounts, or testimonies of their 
 " thoughts and belief, with respect to that subject." 
 In answer, it is observed, that there are some 
 objects of consciousness so obvious and familiar, 
 that no contrariety of opinion respecting them can 
 possibly exist. Every person must be conscious, 
 that he sees, he hears, he feels, he thinks, he 
 wills. And, if I heard a man affirming, that he 
 possessed no such consciousness, I should be more 
 inclined to question the sanity of his intellect, than 
 the sincerity of his declaration. I must be persuaded, 
 
316 
 
 that his motive to dissimulation is of no ordinary 
 rank, nay greater, than I can well conceive, before 
 I should believe myself justified, in charging him 
 with disingenuity, unless I were to suppose, in 
 accordance with the Libertarian hypothesis, that 
 he might possibly dissemble his consciousness, 
 without a motive for that dissimulation. If he 
 possessed but an ordinary portion of common sense, 
 he must perceive, that his declaration would not 
 be credited. 
 
 That the question before us is not quite so plain, 
 or so easy of solution, is sufficiently evident from 
 the contrariety of the reports, which philosophers 
 of known abilities and integrity have attributed, 
 respecting it, to the faculty of Consciousness. That 
 men, who, in all other matters, evince a sacred 
 regard to truth, should in this instance only be 
 guilty of falsehood, and that, without any rational 
 motive to simulation or disguisement, they should 
 profess to believe, what they do not believe, is a 
 supposition, which no generous and intelligent 
 mind will entertain for a moment. I call upon a 
 Libertarian to try, whether he can move a leg, or 
 an arm, or do any one act without a motive. Ap- 
 pealing to my own consciousness, I find, that I 
 cannot. But, though this appeal convinces me, that 
 I cannot will without a motive, and though I am as 
 firmly persuaded of this fact, as I am of my own 
 existence, I should deem it an unpardonable vio- 
 
317 
 
 lation of truth, justice, and charity, if I charged 
 you and other Libertarians- with disingenuity and 
 falsehood, because you denied your consciousness 
 of this fact. I remember the time, when my con- 
 riction on this point was precisely the same with 
 that, which you declare yours to be. Mature re- 
 flection, and a closer attention to my own thoughts 
 and volitions, convinced me of my error. My 
 profession then was not less sincere, than it is now ; 
 nor was I less confident in the justness of my ap- 
 peal to consciousness. The change of conviction 
 interest might have dissuaded me from declaring ; 
 but could never have prompted me to avow. If 
 the same individual then, at different periods* 
 honestly appealed to consciousness in defence of 
 contrary opinions, why may not different indivi- 
 duals, with equal integrity, affirm contradictory 
 reports of the same faculty ? 
 
 But, if it must be, as you insinuate, that in this 
 question, one or other of the contending parties is 
 to be charged with disingenuity, by what right do 
 you presume, there being no third party to decide 
 the question, to arrogate the merit of candour and 
 integrity, and to charge your opponents with dis- 
 simulation and falsehood ? If there be disingen- 
 uity, it must remain a question, to which of the 
 two parties it is justly imputable. But charges so 
 ungenerous and offensive are not to be lightly 
 made: they are disgraceful to science, injurious 
 
318 
 
 to truth, and totally repugnant to that charity, 
 which is slow to censure, and thinketh no evil. 
 No man will indulge in such invidious imputations, 
 if he be not insensible to the value of character, 
 or wholly regardless of the feelings of others. To 
 recur to the rude and degrading supposition, that 
 there must be mala Jides where there is a contra- 
 diction of testimony in subjects of consciousness, 
 this contradiction being capable of a more liberal 
 and satisfactory explanation, is a procedure, dis- 
 creditable to the candour, as well as to the intellect, 
 of any controvertist. 
 
 Does consciousness then deceive us? To this 
 question I do not mean to answer in the affirma- 
 tive ; much less do I intend to deny, that two or 
 more philosophers, after examining their own 
 minds, may entertain different, or contrary opinions 
 concerning any particular mental operation. This 
 seeming contradiction requires to be explained. 
 
 Consciousness is that faculty, by which we per- 
 ceive, what immediately passes within us. It is 
 the eye of the mind, looking inward on itself, and 
 contemplating its own operations. This faculty, 
 by its nature, has no respect to what is past, or 
 what is future. It is distinguished from memory, 
 as being confined to the present; from imagination, 
 as not creating, but examining intellectual exis- 
 tences; from judgment, as being conversant in 
 ideas or perceptions simply, without comparing 
 
319 
 
 them ; and from reason, as being capable of 
 deducing no conclusions. Consciousness, as Mr. 
 Hume observes, never deceives us. If we consult 
 her with rigid attention, and with minds open to 
 conviction, referring nothing to her tribunal, but 
 subjects belonging to her jurisdiction, we may 
 confidently rely on the information, which she 
 communicates. But the office of consciousness, 
 like that of every other faculty of our nature is 
 liable to misconception; and reports, wholly 
 foreign to her province, are, through ignorance, 
 prejudice and inattention, frequently ascribed to 
 her. We hear sometimes an appeal improperly 
 made to this faculty, in reference to past existences. 
 I may say, with strict accuracy, I am conscious, 
 that I now think ; but there would be an impro- 
 priety in saying, though the expression is common, 
 " I am conscious, that I thought yesterday." It is 
 memory, not consciousness, which gives informa- 
 tion of the past. Our conviction, that we possess 
 certain powers corporeal and mental, when these 
 powers are not in exercise, is ascribed to con- 
 sciousness ; whereas the conviction is a deduction 
 from experience, and liable to error. While I 
 exercise any one of these powers, I am conscious, 
 that I possess it ; but while it is inactive, my pos- 
 session of it is not an object of consciousness. 
 My persuasion results from experience ; and that 
 persuasion may be false. The man, who, by palsy, 
 
320 
 
 lias just lost the use of an arm, may say, while yet 
 ignorant of the deprivation, that he is conscious, 
 he can move that arm. Does consciousness then 
 deceive him? No. He refers to consciousness, 
 what is deducible from experience ; and past ex- 
 perience is no infallible criterion of present exis- 
 tence. It is not the sense of sight, that is fallacious, 
 when we affirm on its authority that a rod, partly 
 immersed in water, is bent ; for by appealing to 
 the same sense we learn, that the rod is straight. 
 Our error consists in believing, that sight can inform 
 us of any thing directly, but light and shade. When 
 a person immerses in a fluid one hand above, and 
 the other below, the temperature of that fluid, and 
 feels it at once both warm and cold, does the sense 
 of touch deceive him ? No. His error, if he believes 
 the sense to be fallacious, arises wholly from an 
 erroneous conception of heat and cold. Nor is 
 reason to be charged with error, or to be pronounced 
 fallacious, because the philosopher assumes false 
 premises, and deduces a false conclusion. Fallacy 
 is not to be ascribed to this faculty, because through 
 inattention, ignorance, or precipitancy, we either 
 employ principles, which are false, or misapply 
 principles, which are just, or assume as fact, what 
 is mere hypothesis. When the fanatic, governed 
 by the illusions of a heated fancy, tells us, that he 
 is conscious of the illapses of the divine spirit, and 
 of supernatual communications from the throne of 
 
321 
 
 Deity, is it consciousness, that deceives him? 
 No Consciousness makes no such report. It 
 may attest the existence of such phantasies, in his 
 mind ; but it is imagination, not consciousness, 
 which refers their origin to supernatural communi- 
 cations from the divine spirit. Thus is conscious- 
 ness, though, like every other faculty of our nature, 
 in itself not fallacious, cited in support of errors and 
 absurdities errors not imputable to the power, to 
 which we ascribe them, but resulting solely from 
 our own fancies, or precipitate judgments. Thus 
 also do men of the strictest integrity, appeal to 
 this faculty, in defence of opinions, and theories, 
 diametrically opposite. Whence arises this con- 
 trariety? The cause is obvious. Though conscious- 
 ness never deceives us, and though we may repose in 
 her dictates the most implicit confidence, yet in 
 order to derive correct information from this great 
 oracle of metaphysical science, we must combine 
 with a habit of the most rigid attention the faculty 
 of an acute and discriminating judgment. We 
 must consult her with minds equally disengaged 
 from the fetters of prejudice, and the embarassments 
 of distraction. It is above all things necessary', 
 that we should be careful to distinguish the com- 
 munications of consciousness from the decisions of 
 judgment, the reports of memory, the deductions 
 of reason, and the creations of fancy. Ask a com- 
 mon man, whether he is not conscious, that he 
 let. X 
 
322 
 
 possesses a faculty, which by its own simple and 
 unaided power, informs him of the colour, the 
 figure and the distance of objects ; and he will 
 answer in the affirmative. Ask him, what that 
 faculty is ; and he will answer ; " It is sight." 
 Yet, though he appeals to consciousness for the ex- 
 istence of such a faculty, and firmly believes, that 
 consciousness assures him, he actually possesses 
 it, we know, that sight communicates no informa- 
 tion whatever, but concerning light and shade. 
 We know, that our perceptions of figure, distance 
 and magnitude are acquired perceptions, and are 
 the judgments of experience. Thus by miscon- 
 ceiving the real province of consciousness, and 
 referring to her authority the reports of other intel- 
 lectual powers, we appeal to her in cases, which 
 are beyond the limits of her jurisdiction, and impute 
 to her errors, which she utterly disclaims. 
 
 But even when confined within its proper pro- 
 vince, consciousness, like every other mental 
 faculty, while it is susceptible of improvement, 
 and may be strengthened by exercise, is also liable 
 to be corrupted by prejudice, to be darkened 
 through ignorance, to be impaired by inaction, 
 and distracted by fancy. Hence arise the frequent 
 appeals to this faculty in favour of opinions the 
 most contradictory. Though consciousness is not, 
 in its own nature, fallacious, the accuracy of its re- 
 ports must depend on the degree of improvement, 
 
323 
 
 to which it has attained, and its freedom from any 
 foreign or seductive influence. As the eye of the 
 body if not diseased, nor directed through a false 
 medium, will present us with correct images of the 
 objects before us, in respect to light and shade, so 
 consciousness, the eye of the mind, if neither 
 distorted by prejudice, nor darkened by ignorance, 
 neither weakened by inaction, nor extended beyond 
 its proper sphere, will uniformly report with accuracy 
 the subjects of its examination. In other words, 
 if actuated solely by the love of truth, and divested 
 of all prejudice, we exercise a steady and rigid 
 attention to the operations of our own minds, we 
 may confidently rely on the testimony of conscious- 
 ness. But few men possess that freedom from 
 prejudice, that acuteness of discernment, that 
 capacity of abstraction, that power of metaphysical 
 discrimination which strengthened by habits of 
 patient and close attention, are essentially necessary 
 to a correct investigation of the powers and opera- 
 tions of the human mind. If then endowments so 
 rare, and habits so difficult of attainment, are in- 
 dispensably necessary to a correct inspection of 
 our own minds, it needs excite no surprise, if we 
 hear the most inconsistent and mutually repugnant 
 theories supported by appeals to the testimony of 
 consciousness. This indeed occurs so often, that 
 all arguments derived from consciousness, should 
 be strictly examined, and cautiously admitted. 
 
324 
 
 Though philosophers, then, should maintain 
 contrary opinions, on any Metaphysical subject, 
 and though each party should appeal to the same 
 faculty of consciousness for the truth of its doctrine, 
 this contrariety of sentiment furnishes no certain 
 evidence, I had almost said, even no presumption, 
 that either of the parties is chargeable with disin- 
 genuity. One man affirms, that he possesses a 
 power of self-determination. He affirms, that he 
 can act according to the weaker or the stronger 
 motive, just as he pleases, and that he can prefer 
 the one to the other without a motive for that pre- 
 ference, nay, that he can will to act, without any 
 motive whatever, and appeals to consciousness in 
 support of his opinion. Another denies this, and 
 assures us, that he is not conscious of any such 
 power nay, that he is conscious, that he possesses 
 no such power. He asserts, that the only power, 
 of which he is conscious, is the power of doing, 
 as he wills, and the only liberty, which he pos- 
 sesses, the liberty of willing, not without a motive, 
 but free from any external opposition, or constraint. 
 Now, on one side, or the other, there must be 
 an error : both assertions cannot be true : one 
 necessarily must be false. What then shall we 
 conclude? Shall we say, that one, or other, of 
 the parties is guilty of mala fides ? This would, in 
 my apprehension, be a conclusion, as unphiloso- 
 phical, as it would be uncharitable and unjust. 
 
325 
 
 This, however, is your inference. Is it not more 
 candid, as well as more consonant with reason, 
 to suppose, that in consulting consciousness, in 
 which operation the most rigid attention is neces- 
 sary, either one of the parties has erred, by not 
 strictly enquiring, whether there be not a moving 
 power, by which the will itself is governed ; or the 
 other by fancying, that they are conscious of a 
 moving power, or powers, ulterior to the will, by 
 which its determinations are governed, when no 
 such powers actually exist ? Either error is cer- 
 tainly possible ; and an error, not a wilful and 
 deliberate falsehood, we are, by every principle of 
 truth and charity, bound to account it. Mankind 
 never have agreed, and probably never will agree, 
 respecting subjects much more accessible to inves- 
 tigation, than the operations of the human mind. 
 And to impute disingenuity and falsehood to op- 
 ponents, because they see not, as we see, and 
 believe not, as we believe, is of all errors the most 
 ungenerous, the most unphilosophical, and the 
 most offensive. While it betrays unpardonable 
 inattention to the powerful effects of the prejudices 
 of education, which we perceive adhering with 
 unconquerable tenacity to the acutest intellects, 
 and the most vigorous minds, it indicates at the 
 same time a spirit of pride, presumption and bigotry, 
 arrogating to itself an exemption from error, and 
 denying to others even the character of integrity, 
 
326 
 
 unless they believe and act, as it may be pleased 
 dogmatically to prescribe. 
 
 When I find, therefore, two parties, each appeal- 
 ing to consciousness, in favour of two contrary 
 opinions, I do not feel myself justified, in- con- 
 cluding, that one of them is guilty of mala jides. 
 1 am rather inclined to ascribe this contrariety to 
 that diversity of degree, in which we find sagacity, 
 reflection, and discernment exist in different minds. 
 That this is the more candid and liberal conclusion, 
 no man will deny ; that it is the more correct, in 
 the present instance, one, acknowleged fact will 
 furnish a strong presumptive evidence. For, if 
 there be disingenuity on the part of Necessarians* 
 if they are guilty, as you affirm, of mala Jides, would 
 it not be a miracle, a fact utterly unaccountable, 
 that no Necessarian should ever have been found, 
 who either inadvertently, or deliberately, disclosed 
 his secret convictions, and acknowleged, that he 
 really possessed that consciousness of free will, 
 which he had previously dissembled ? A rational 
 explanation of this simple fact, in consistency with 
 your opinion, would serve to extenuate the offence, 
 with which you are chargeable. 
 
 You ask, whether " /think such contradictions 
 " can be accounted for, in a fair and satisfactory 
 " manner on the supposition of a real unalterable 
 " difference in the mental constitution of different 
 " individuals of mankind, implying, that all of 
 
327 
 
 " them, who contradict one another the most 
 " directly are equally candid and sincere, in what 
 " they assert, but that the point in dispute between 
 " them never can be settled by any competent 
 " evidence, and is bona Jide beyond the reach of 
 " the human faculties ?" 
 
 That there exists a constitutional and radicaj 
 difference in different minds, which no external 
 circumstances can remove, is an opinion consonant 
 with the whole analogy of nature, and sanctioned by 
 experience ; but at the same time I am firmly per- 
 suaded, that much more influence is ascribed to 
 this difference, than, on strict enquiry will be 
 found to belong to it. I do not, therefore, conceive 
 it necessary to resort to any real and unalterable 
 difference in our mental constitution, in order to 
 accoimt for that contrariety of opinion, which 
 obtains among mankind on subjects, to which they 
 appear to have devoted equal attention. Educa- 
 tion, profession, society, course of reading, with a 
 variety of other circumstances, have a much more 
 powerful effect in creating this contrariety, than 
 any difference in mental constitution. And I 
 have no hesitation in declaring it to be my firm 
 opinion, that this discordance of sentiment may, 
 and often does, consist with the bona Jides of the 
 contending parties. We are both corporeally and 
 intellectually, in a great degree, the creatures of 
 circumstances. Minds, equally sagacious, and 
 
328 
 
 equally candid, perceive the same object in dif- 
 ferent lights. The Protestant may ridicule and 
 reject the absurdities of the Romish creed ; but 
 these absurdities have been firmly believed by men 
 of the most transcendent talents, and the most 
 incorruptible integrity. Nay, suppose the man, 
 Who derides them to have been placed in the same 
 situation, and the probability is, that he would 
 have adopted the same faith. The prejudices of 
 early education are not easily conquered. Quern 
 amictum mater dedit, solicite custodiunt, is an obser- 
 vation applicable to most men. And when these 
 prejudices yield to other opinions, the change of 
 sentiment only serves to shew, how much our 
 notions of men and things are governed by the 
 society which we frequent, the books which we 
 read, and the occupation, which we follow. One 
 man believes the doctrine of the Trinity ; another 
 rejects it as unscriptural and absurd ; one yields 
 his assent to the eternity of future punishment, 
 another shudders at the dogma as false and impious; 
 one believes, that man is a being wholly material ; 
 another is persuaded that the thinking principle 
 is purely immaterial. And, where is I he rash and 
 presumptuous bigot, whether in religion, or in 
 philosophy, who will dare to brand some or other 
 of these men with wilful and deliberate falsehood ? 
 You ask, if " / think it would be right to dis- 
 * cover, on which side, in any such controversy, 
 
329 
 
 " the falsehood lay ; and to detect and ta expose 
 " to just censure those, who have been guilty of 
 " it." I answer, if it can be demonstrated, that 
 any man, or set of men, have wilfully and know- 
 ingly asserted a falsehood, by professing to believe, 
 what they do not believe, they justly deserve to 
 be exposed to shame. 
 
 You ask, " what kind of evidence /think would 
 " be sufficient to establish such an unfavourable 
 " conclusion (mala fides) with respect to men, who 
 " professed and called themselves philosophers." 
 
 In answer, I will first state, what in my judg- 
 ment, would not be sufficient. It would not suffice 
 to inform one of these philosophers, that he was 
 convicted of mala fides, because you had published 
 an argument, which you conceived to be, and 
 were pleased to call, a Mathematical Demonstra- 
 tion, proving his opinion to be absurd. This, I 
 say, would not suffice. For he might naturally 
 and pertinently reply, " I do not esteem your 
 *' argument a Demonstration ; I believe it to be 
 " fallacious. The very circumstance, that it does 
 " not produce conviction on my mind, is an 
 " evidence of its fallacy. Nay, I dismiss" he 
 might say, " my own judgment of its character ; 
 " it is regarded by thousands of intelligent men in 
 " the same light, all of whom deny, that it possess- 
 " es any claim whatever to the name of Demon- 
 " stration." Nay farther, he might remind you, 
 
330 
 
 that many of your own friends, who espouse the 
 very doctrine, which this pretended Demonstration 
 is offered to support, deny it to be a Demonstra- 
 tion, and reject the argument as fallacious. " "Who 
 " ever heard," he might truly ask, " of a proposi- 
 " tion in Euclid being rejected, or even doubted, 
 " by thousands of Mathematicians ? Have not 
 " you yourself acknowleged, that Mathematicians 
 " find it impossible to resist Mathematical 
 " evidence ?" And he might pertinently add, " it 
 " remains to be determined, whether you, or I, 
 " are guilty of the greater error, you in assenting 
 " to your argument, or I in rejecting it. I do not 
 " consider myself chargeable with mala Jides, be- 
 " cause you are pleased to dignify a paralogism 
 " with the name of Demonstration." 
 
 Again It will not be sufficient merely to assert, 
 that his conduct does not exactly accord with the 
 principles, which he professes. This must be 
 proved by indubitable facts. It must be proved, 
 for example, that the Necessarian acts, as if he 
 believed, that the human will is not necessarily 
 governed by motives, and that he has a self-deter- 
 mining power, arbitrary and independent, cbn- 
 trouling all motives without a motive, and* acting 
 simply by its own sovereign authority. 
 
 Nor will even contrariety between a man's con- 
 duct and professed principles, suffice in all cases 
 to establish against him the charge of mala Jides. 
 
331 
 
 Of this fact it would be easy to produce number- 
 less evidences. Does the physician, for example, 
 never deviate from that regimen, which he re- 
 commends to others, and believes to be salutary? 
 Is he chargeable therefore with mala Jides ? Does 
 he never with a smiling countenance look at the 
 wine " mantling in the cup," and liberally partake 
 of it, contrary to his own convictions of its injuri- 
 ous tendency, and the counsel, which he admin- 
 isters to his gouty patients ? Is the philosopher 
 to be charged with disingenuity or falsehood, who, 
 from the prejudices of early education, trembles at 
 night to walk through a church-yard, and yet utterly 
 disclaims all belief in ghosts and apparitions ? 
 
 But let me offer to consideration a graver ex- 
 ample. If there can possibly be any motives 
 presented to the human mind, calculated power- 
 fully to impress it, and almost irresistibly to con- 
 troul and direct its passions, regulating every 
 sentiment and movement of the soul, they are 
 those which the doctrines and the precepts of the 
 Christian religion furnish. If there be any faith 
 capable of rendering man wise, virtuous, and 
 happy, it is unquestionably faith in the religion of 
 Jesus. Does then a belief in Christianity uniformly 
 produce this salutary effect? Let the conduct of 
 the best of its votaries answer. Nay, do we not 
 find some, in defiance of their belief in those awful 
 sanctions, which it exhibits to our contemplation, 
 
332 
 
 acting in direct opposition to its precepts? All 
 these are not chargeable with mala fides, though 
 there is a striking inconsistency between their 
 faith, and their practice. If we nnd a Ciiristian 
 pastor occasionally deviating from those principles, 
 by which he professes to be guided, nay, if we 
 find him almost habitually, in some particular, 
 violating a rule of his religion (for the best of men 
 have some sin, by which they are " easily beset") 
 are we warranted in charging him with falsehood 
 and disingenuity ? " Are you," said Dr. Johnson 
 to a reverend gentleman in Scotland, " are you 
 " so grossly ignorant of human nature, as not to 
 " know, that a man may be very sincere in good 
 " principles, without having good practice?" 
 Horace says, " Video meliora, proboque; deteriora 
 " sequor," or as another ancient has expressed it 
 
 To, xp y<TTot 
 
 Oux exTTOVOujtxev 8'* 01 (ilv agy/aj wro, 
 
 O!8* TjSovijv 7rpo0evT VTI TOO xaXou. 
 
 EUR. HIPP. 380, 
 
 I do not mean, however, to contend, that there 
 are no cases, in which the contrariety between 
 conduct and profession may convict the individual 
 of dissimulation, or disingenuity. But I affirm, 
 that this contrariety, in questions of philosophy 
 and religion, is in general no evidence of insincerity ; 
 and 1 maintain, that this unfavourable inference 
 
333 
 
 should never be admitted, and by a liberal mind, 
 will never be proposed, unless in those cases, in 
 which any other construction is evidently inadmis- 
 sible, and when the attempt to reconcile the practice 
 of the individual with sincerity of profession, would 
 argue only blindness and folly. 
 
 I have said, that to charge a philosopher with 
 mala Jides, because he rejects an argument, which 
 his adversary has the vanity to call a Mathematical 
 Demonstration, is not sufficient to convict him of 
 that charge. I have said also, that though the 
 principles of belief, which an individual professes 
 may be occasionally irreconcileable with his con- 
 duct, this repugnancy is far from furnishing any 
 certain evidence of mala Jides. Inconsistency is, 
 more or less, the character of every human being. 
 
 I shall now briefly state, what evidence would, 
 in my apprehension, suffice to convict a philoso- 
 pher of insincerity. 
 
 The first, which I shall mcation, is the clear 
 discordance of his professed sentiments with the 
 general scope, and manifest tenour of his writings. 
 If I saw an author professing a profound respect for 
 any doctrine or system, which it was obviously 
 the intention of his arguments to subvert, I should 
 conceive, that he furnished me with sufficient 
 evidence of mala Jides. When Mr. Hume professes 
 a great respect for Christianity in his Essay on 
 miracles when he writes, as if it were his main 
 
3.34 
 
 object " to confound those dangerous friends, or 
 " disguised enemies, of the Christian religion, who 
 " have undertaken to defend it by reason" when 
 he calls it with great seeming reverence (for in the 
 passage, to which I allude an ironical construction 
 seems inadmissible) when he calls it, I say, " our 
 most holy religion" while he assumes this appear- 
 ance of friendship and respect, yet labours to 
 annihilate one of its strongest evidences, we may 
 warran tab! y charge him with insincerity, by profess- 
 ing a reverence for a system of religion, which his 
 arguments were evidently intended to overthrow. 
 
 Again When the conduct of any philosopher 
 is uniformly at ^variance with his profession, and 
 when there is no conceivable hypothesis, on which 
 this contrariety can be explained, in consistence 
 with his sincerity, malajides may be justly imputed 
 to him. The cases, in which this contrariety may 
 exist, and the degrees in which it is found, are 
 necessarily various, nor can any general rule be 
 established, applicable to all. Each must be 
 judged by its own peculiar evidence. In some, 
 the arguments of insincerity may be incontestably 
 conclusive; in others they may amount to a 
 strong presumption ; and in some they may create 
 simply a suspicion. But to establish the charge 
 of disingenuity there must exist either an im- 
 possibility, or a high degree of improbability, in 
 every attempt to reconcile the repugnance of con- 
 
335 
 
 duct and profession, with the supposition, that 
 the philosopher believes, what he professes to 
 believe. The simple fact of inconsistency proves 
 nothing : for this may be, and often is, perfectly 
 reconcileable with sincerity of belief. If a philoso- 
 pher^ were to maintain that carbonic acid gas is 
 not only innoxious, but salutary, and yet should 
 in all cases cautiously avoid inhaling it, his 
 conduct would furnish incontrovertible evidence 
 of his disingenuity. Here it seems impossible to 
 offer any explanation, by which the contrariety of 
 his conduct and profession, can be reconciled 
 with sincerity of belief. If I heard a philosopher 
 protesting against the vulgar faith in dreams, and 
 asserting that they are not prognostic of future 
 events, but merely indicative of the present state 
 of our bodies or minds, yet saw him constantly 
 elated or depressed by his own dreams, this in- 
 consistency of profession and conduct would 
 afford a very strong presumption, that his belief 
 was not sincere. But I should not hold even this 
 contrariety to be, in all cases, a clear and unques- 
 tionable evidence of the insincerity of his profes- 
 sion. For, is it not possible, that the illusions of 
 the night, like the impressions of an interesting 
 novel or a mimic scene, might have left behind a 
 correspondent effect on his animal spirits, which 
 the rational faculty could not immediately dispel ? 
 
330 
 
 If a person were to maintain that animal food is 
 necessary to health and strength, and yet in all 
 cases carefully abstain from it, I should think that 
 his conduct furnished probable ground for sus- 
 pecting that he professed to believe, what he did 
 not believe But I should not consider this con- 
 trariety of profession and practice to be a decisive 
 evidence of disingenuity, because the possibility 
 must be admitted, that he may have early contract- 
 ed an antipathy to this kind of aliment, which he 
 has never been able to conquer. 
 
 I have said, that the inconsistency of a Christian's 
 practice with his creed, though it manifests the 
 inactivity, is no sure evidence of the insincerity, 
 of his faith. Even, when this inconsistency is not 
 confined to partial acts, or an individual habit, 
 but extends even to the general conduct, we are 
 not authorised to infer, that he does not believe 
 those principles, to which he professedly assents. 
 For it is no uncommon delusion for the habitual 
 sinner, while he believes in the awful sanctions of 
 Christianity, to flatter himself with the hope, that 
 his future penitence will atone for his present errors, 
 thus endeavouring to reconcile his convictions of 
 divine justice with his violation of its laws, his 
 present danger with his ultimate salvation. His 
 faith is sincere, but his practice is repugnant to it. 
 The doctrine is believed, but vicious allurements. 
 
337 
 
 strengthened by the hope of ultimate impunity, 
 overpower its natural influence. The temptation 
 is to act wrongly, not to profess falsely. 
 
 But, when the converse is the fact, and when 
 there is a powerful temptation to maintain certain 
 opinions, while the conduct bespeaks very differ- 
 ent convictions, it is then, that disingenuity is 
 either presumable, or manifest. Had the prophet 
 Daniel been tempted, either by allurements or 
 threats, to profess the religion of the Babylonian 
 Court, and at the same time been found secretly 
 adoring the God of his fathers, his conduct would 
 have undeniably betrayed the insincerity of his 
 profession. When Galileo, overpowered by the 
 terrors of the Inquisition, abjured his belief in the 
 Copernican system we may warrantably affirm, 
 that his abjuration was insincere. The circum- 
 stances, in which he recanted the heresy imputed 
 to him, coupled with the powerful evidence, which 
 he had himself adduced in support of this theory, 
 threw a strong colour of suspicion over the sincerity 
 of his retractation; and his subsequent labours 
 confirmed the suspicion. 
 
 From the preceding observations, respecting 
 contrariety of profession and practice, the two 
 following propositions maybe regarded as establish- 
 ed. 1st. That the simple fact of contrariety between 
 profession and practice furnishes no conclusive 
 evidence, and in many cases, not even a suspicion, 
 Let. Y 
 
338 
 
 of the philosopher's insincerity, 2dly. That this 
 insincerity should in no case be imputed, unless 
 where there is an impossibility, or a strong moral 
 improbability, in every supposition, by which it is 
 attempted to reconcile the conduct of the indivi- 
 dual with the sincerity of his belief. 
 
 Perhaps you will ask, if I do not think, that a 
 philosopher resisting a mathematical demonstra- 
 tion, and professing to disbelieve, what all learned 
 men, himself only excepted, firmly believe, is 
 not chargeable with malajides. If a case so extra- 
 ordinary should occur, I should hesitate to impute 
 to him disingenuity ; for it , appears to me hardly 
 consistent with possibility, that any man, in his 
 sound senses, would refuse his assent to a Mathe- 
 matical demonstration, conscious, that he might 
 as justly deny, that things, which are equal to the 
 same thing, are equal to one another. His sanity I 
 might suspect ; but his veracity I should be slow 
 to question. And here I would remark, in passing, 
 that, if any suspicion of disingenuity falls on the 
 philosopher, who refuses his assent to Mathemati- 
 cal evidence, some degree of suspicion might 
 attach to him also, who professes to believe that 
 to be a demonstration, which thousands of learn- 
 ed men have rejected as a sophism. Yet I am not 
 inclined to question your veracity. Notwithstand- 
 ing the rejection of your argument by some friends 
 to your hypothesis, and all its adversaries, not- 
 
339 
 
 withstanding also certain facts, which furnish some 
 presumption, that you yourself doubt its validity 
 (see p. 71.), I am not inclined to affirm, that you do 
 not believe it to be a Mathematical demonstration. 
 
 You ask, if " / think that the same kind of 
 " evidence, which is held sufficient to convict a 
 " witness of perjury in a court of justice, that is, 
 " deliberate inconsistency, would be sufficient to 
 " convict such philosophers of disingenuity." 
 
 Before I proceed to answer this question, I take 
 the liberty to observe, that there are various kinds 
 of inconsistency, as it respects our thoughts, our 
 words, and our actions. There may be an incon- 
 sistency in our thoughts. This, indeed, is no 
 uncommon species of the error in question. There 
 is some inconsistency, for example, in your think- 
 ing, that your argument, to which none of your 
 adversaries, and not even all your friends have 
 assented, is a Mathematical demonstration, and 
 thinking at the same time, that every Mathematical 
 demonstration compels assent. These two incon- 
 sistent opinions you have deliberately affirmed ; 
 are you therefore chargeable with malajides f There 
 is also an inconsistency in words, and likewise in 
 conduct. There appears, for instance, some 
 inconsistency in your professing a regard for justice, 
 and at the same time so far violating its principles, 
 as to charge those Necessarians with disingenuity 
 and falsehood, who, never having seen your 
 demonstration, were precluded from the possibility 
 
340 
 
 of being enlightened by your argument, and con- 
 vinced of their error. For the philosophical world, 
 not having been previously favoured with your 
 Demonstration, how were these Necessarians to 
 know, that they were believing an absurdity? 
 There is surely no criminality in involuntary igno- 
 rance ; nor can any person be justly charged with 
 disingenuity, for professing to believe any doctrine, 
 before its falsity, or its absurdity be proved. But 
 the inconsistency, to which your query refers, is 
 the inconsistency of a witness in a court of justice; 
 and to this special case I shall now direct my 
 attention. 
 
 In your letter to Dr. Priestley you observe, that 
 " he, and every person must acknowlege, that 
 " consistency is one of the chief tests of truth ; 
 " and that according to Mr. Hume, in his defence 
 " of Necessity, whatever is consistent with itself, 
 " and with known truths, is generally held to be 
 " true," whereas that, " which is found inconsis- 
 " tent with itself, and with known truths, is always 
 " held to be false." 
 
 After a careful examination of Mr. Hume's 
 Essay on Necessity, I have not found the doctrine, 
 which you here ascribe to him, either directly 
 affirmed by the author, or justly deducible from 
 any of his speculations on that subject. I find 
 Mr. Hume offering, as an argument in favour of 
 Necessity, that uniformity of operation, which we 
 remark in the passions and affections of human 
 
341 
 
 nature, and the strong resemblance, which obtains 
 between the sentiments and manners of one nation, 
 or one age, and those of another nation, or another 
 age, in which like passions and appetites may 
 have predominated. The same motives, he ob- 
 serves, always produce the same actions. Ambi- 
 tion, avarice, vanity, friendship, generosity, and 
 public spirit, variously modified and combined, 
 are producing the same effects now, which they 
 produced in ages past. This uniformity he consi- 
 ders as a strong proof, that the sentiments, feelings 
 and passions of our nature exert a definite and 
 necessary influence over our actions ; and he 
 observes, that in all our reasonings, we acknow- 
 lege a uniformity in the agency of human motives, 
 as well as in the operations of body. " If we would 
 " explode," says he, " any forgery, we cannot 
 " make use of a more convincing argument, than 
 " to prove, that the actions, ascribed to any per- 
 " son, are directly contrary to the course of na- 
 " ture, and that no human motives could, in such 
 " circumstances, induce him to such a conduct. 
 " If we heard a traveller," says Mr. Hume, " giving 
 " an account of men, wholly different from any, 
 " with whom we were acquainted, who were en- 
 " tirely divested of avarice, ambition, or revenge, 
 " who knew no pleasure, but friendship, generosity 
 " and public spirit, we should immediately, from 
 " these circumstances, detect the falsehood, and 
 
342 ' 
 
 " prove him a liar, with the same certainty, as if 
 " he had stuffed his narration with stones of cen- 
 " taurs, miracles and prodigies." The inconsistency 
 of the narrative with the known constitution of 
 human nature would render it absolutely incredi- 
 ble. 
 
 Mr. Hume's doctrine, therefore, is, that any 
 repugnancy to the known course of .nature, or to 
 the known connection between certain active prin- 
 ciples in man, and certain effects, we should regard, 
 as a proof of want of veracity in that person, who 
 should affirm as a fact, any event irreconcileable 
 with this connection. But Mr. Hume has nowhere 
 said, as far as I know, that the consistency of any 
 theory, or narrative, with itself, and with known 
 truths, is one of the chief tests of its truth ; though 
 its inconsistency with the acknowleged course of 
 nature, and the constitution of man he considers, 
 to be a clear evidence of its falsehood. Consistency 
 can do nothing more, than impart to any narrative 
 the character of verisimilitude. It authorises us 
 to say simply, that the story may be true. If I 
 heard a person relating a tale, perfectly consistent 
 with itself and also with the established laws of 
 moral and physical nature, all, that independently 
 of my knowlege of the person's character and cir- 
 cumstances, and my experience of human testimony, 
 I should be justified in asserting, would be, that 
 the story may be true. Mere consistency cannot 
 
343 
 
 carry me one step farther. If I know the man to 
 be a person of honour, or of reputed veracity, I 
 instantly yield my belief, persuaded, that he would 
 not assert any thing, but what he knew to be fact. 
 If without this knowlege of his character I give 
 credit to his narrative, my belief must be founded, 
 not in the consistency of the story with itself and 
 with the course of nature (though this is essential 
 to its credibility) but in experience, an experience, 
 which teaches me, that men, placed in certain 
 circumstances, where they cannot be deceived 
 themselves, and where they have no motive to 
 deceive others, speak the truth, and deserve credit. 
 But mere consistency, I repeat, obviates simply 
 the previous question of credibility. If the consis- 
 tency of any narrative with itself, and with the 
 constitution of things, furnished any positive ground 
 of belief, the fictions of the poet, of the dramatist, 
 and the novellist would be entitled to credit. 
 While it is admitted, then; that inconsistency with 
 itself, or with known truths is a complete proof of 
 the falsehood of any narrative, it is denied, that 
 we generally, nay in any case, yield our assent to 
 any relation, on the simple ground, of consistency 
 with itself, and with knozvn truths, or as Mr. Hume 
 has more precisely expressed it, the course of nature- 
 I contend, that consistency is a test simply of 
 credibility. 
 
 You proceed" With equal certainty I hold, 
 
344 
 
 " as I believe all mankind do, consistency to be a 
 " good test of veracity ; and at least inconsistency 
 " is always held complete evidence of falsehood." 
 
 When any problematical opinion is to be enforced, 
 or any hypothesis to be maintained, which reason 
 is finable to support, it is no uncommon artifice in 
 controversial warfare to press into its service the 
 general consent of mankind, the disputant flatter- 
 ing himself with the hope, that his antagonist will 
 not presume to oppose himself to the common sense 
 of the whole world. 
 
 The " certainty' of your other doctrine, as a 
 matter of speculation, and likewise the truth, with 
 which you have ascribed it to Mr. Hume, in his 
 Essay on Necessity, I have already examined ; 
 and this truth, this certainty I apprehend to be no 
 truth, no certainty whatever. With equal confi- 
 dence, therefore, and equal certainty you may, as 
 you do, affirm, that consistency is a good test of 
 veracity, and inconsistency a complete evidence 
 of falsehood. In respect to the first of these pro- 
 positions, if it be true, as I have endeavoured to 
 shew, that consistency gives merely the character 
 of verisimilitude to any narrative, rendering it 
 simply credible, it follows, as a necessary conse- 
 quence, that, when we hear a person relate a 
 consistent tale, we are not warranted to assert his 
 veracity ; but merely to conclude, as the story is 
 not at variance with itself, or with known facts, 
 
345 
 
 that he possibly speaks the truth. Consistency is 
 no evidence of the actual, but only of the possible, 
 veracity of the relater. 
 
 That your second proposition is false, I have 
 already, it is hoped, sufficiently evinced. To 
 constitute the crime of moral falsehood, there 
 must be an intention to deceive; and that this 
 intention exists in all cases, where inconsistency is 
 found, is a proposition, which no liberal mind 
 will admit for a moment. Reason rejects it as 
 false, and charity spurns the imputation as uncan- 
 did and unjust. Wretchedly vicious, indeed, and 
 deeply degraded would be the species, if inconsis- 
 tencies either in theory, or in practice, from both 
 which few, if any, can boast exemption, were 
 conclusive proofs of dissimulation and falsehood. 
 Is it a crime to profess two inconsistent opinions, 
 and not perceive their inconsistency? Or is in- 
 consistency another name, in all cases, for want 
 of veracity? He knows little, truly, of the human 
 mind, its imperfections, its prejudices, its blind- 
 ness to its own errors, who will venture to affirm 
 it. But if your opinion on this subject, extraor- 
 dinary as it appears to me, be the common sense 
 of mankind, as you allege it is, it is not requiring 
 too much, if I intreat you to inform me, in what 
 system of Ethics, and by what moralists, incon- 
 sistency is held to be an unquestionable proof of 
 malajides? Is it an uncommon thing for Theolo- 
 
340 
 
 gians, and men of speculative science, to maintain 
 opinions mutually irreconcileable ? Establish your 
 doctrine, and they become chargeable with wilful 
 and deliberate falsehood. Nay, will you assert, 
 that there is no inconsistency in your own creed, 
 whether theological or political, physical or meta- 
 physical ? 
 
 Quam temere in nosmet legern sancimus iniquam I HoK. 
 
 Inconsistency in any theory, or any narrative, I 
 admit to be an evidence of physical falsehood ; 
 but it is moral not physical falsehood, veracity, 
 not physical truth, with which we are at present 
 concerned. 
 
 Having offered these preliminary observations I 
 return to the question, to which I answer, that the 
 deliberate inconsistency of a witness in delivering 
 his testimony before a court of justice, is not, even 
 generally, alone sufficient to convict him of perjury. 
 The reason is evident. To convict a person of a 
 lie, or of perjury, which is only a more solemn lie, 
 a wilful intention to deceive must be clearly esta- 
 blished. And where the inconsistency of the 
 witness is not such, as positively to manifest this 
 intention, and where he has obviously no sinister 
 purpose to promote by his testimony, in short, 
 where the mains animus cannot be either directly 
 proved, or clearly inferred, no court whatever 
 would convict him of perjury. Convictions, in- 
 deed, of this crime are generally established by 
 
347 
 
 the testimony of other witnesses ; and before the 
 conviction can legally take place, there must be 
 proof, that the falsehood was wilful, material, 
 positive and corrupt, that is, that it was told deli- 
 berately, and malo animo, essentially also affecting 
 the question. 
 
 That the inconsistency of a witness in a court of 
 justice may arise from a variety of other causes, than 
 the intention to deceive, is a truth SQ evident, and 
 so generally admitted, that to confirm it by argu- 
 ment, or illustrate it by example, would be to tres- 
 pass on the time and patience of the reader. I shall 
 therefore only observe, in answer to your remark, 
 that, if it be true, that the cross examination^ of a 
 witness in a court of justice often extorts the truth, 
 it is equally undeniable, that, in numberless in- 
 stances, it has drawn a conscientious and honest 
 witness into inconsistency, and contradiction. 
 
 If incongruity of opinion, in matters of religion 
 and philosophy, were an infallible evidence of 
 mala fides, it is to be seriously apprehended, that 
 few indeed would be acquitted of the charge. It 
 is beside my present purpose to expose the contra- 
 dictions, and gross inconsistencies, which the 
 doctrine of philosophical liberty involves; but they 
 appear to me demonstrable with all the certainty 
 of intuitive evidence: yet I should feel myself 
 guilty of the most unpardonable violation, not 
 only of the common courtesies of civilised society* 
 
348 
 
 but of the more sacred laws of charity and candour, 
 if I presumed to charge any Libertarian with deli- 
 berate and wilful falsehood. We cannot all think 
 alike; nor all judge with equal accuracy. The 
 distant spire, which one pronounces to be a pyra- 
 mid, may to another appear to be a cone. Whence 
 arises this difference ? or what should we thence 
 infer ? Simply this, that the visual faculty of the 
 one, who judges rightly, has been probably more 
 exercised, in ascertaining the figure of distant 
 objects, than that of the other. If this inference 
 be allowed to be just and proper, where objects of 
 sense are the matters in question, it will not surely 
 be disputed, that a similar conclusion more forcibly 
 recommends itself, when abstract principles are 
 the subjects of discussion. Our intellectual dis- 
 cernment, as every other faculty, which we pos- 
 sess, is sharpened and improved by exercise ; and 
 closer attention, devoted to any object, neces- 
 sarily begets a more intimate acquaintance with it 
 The most correct opinions on Metaphysical sub- 
 jects maybe expected from those, .who combine 
 with a superior share of intuitive sagacity a rigid 
 and patient attention to the operations of their own 
 minds. 
 
 You ask " Do you think, that it would be in- 
 " consistent in those philosophers, if they should 
 " perceive at once, and intuitively the falsity of 
 u many practical inferences, shewn to be necessary 
 
349 
 
 " consequences of their own doctrine, in certain 
 " supposable cases, which might easily be brought 
 " to the test of open and unequivocal experiment." 
 It is answered, in the negative. To perceive the 
 falsity of any inferences from any doctrine is not 
 inconsistency, unless, by an egregious perversion 
 of language, the detection of error is to be designed 
 by this appellation. Were you to perceive the 
 falsity of many practical inferences, shewn to be 
 the necessary consequences of your hypothesis, 
 could you, without violating the established mean- 
 ing of words, call this perception inconsistency ? 
 Or, if I should be convinced by your " demon- 
 stration," that many practical inferences, clearly 
 deducible from our hypothesis, are false, shall this 
 conviction be called inconsistency ? Surely not. 
 The maintenance of an error may, but the detec- 
 tion of that error cannot, imply any incongruity 
 either in sentiment, or in conduct. But, when 
 you proposed the question, it appears evident to 
 me, that you were labouring under some confusion 
 of thought ; or if your conception was clear, it is 
 certain, that your manner of communicating it is 
 incorrect and obscure. For I presume, you in- 
 tended to ask, whether it would be inconsistency 
 in any philosopher to maintain an opinion, while 
 he at the same time intuitively perceived, or was 
 by demonstration convinced, that its practical 
 consequences were false, or absurd. If this be 
 
350 
 
 the queiy, which you meant to propose, it is 
 answered, in the affirmative. It would be incon- 
 sistency. 
 
 But permit me to observe, that not only is the 
 question, which you propose, manifestly irrelevant, 
 but that my affirmative answer will also avail you 
 nothing, until you have proved one, or other, of 
 these two positions. 1st. That Necessarians do 
 intuitively perceive the absurd practical inferences, 
 cleducible from their own theory : or 2d. That 
 you have demonstrated, even to their own convic- 
 tion, its practical and necessary consequences, to 
 be false, or absurd. These positions you have 
 presumed, and on this presumption you ground 
 your charge. Here consists your fundamental 
 error, an error, which mixes with every query 
 you propose, and renders them all, one after ano- 
 ther, irrelevant and nugatory. Before you insti- 
 tuted your enquiry, whether inconsistency forms 
 a sufficient ground for imputing to a philosopher 
 disingenuity and falsehood, it was incumbent on 
 you to prove by unquestionable evidence, these two 
 points 1st. That his opinions are inconsistent 
 with his practice, and with known facts ; and 2d. 
 That he himself is conscious of this inconsis- 
 tency. Until you have proved these two positions 
 by incontestable argument, all your attempts to 
 defend your conduct can serve no other purpose, 
 than to manifest the weakness, I will not say, the 
 
351 
 
 pertinacity, with which you would vindicate your 
 rude and ungenerous imputation an imputation, 
 which no sophistry can palliate, no ingenuity can 
 justify. Shew, that the principles, which we main- 
 tain, involve contradictions, and are uniformly at 
 variance with our practice, and you may then 
 enquire what degree of mala fides our inconsistency 
 evinces. But we cannot suffer you to beg the 
 question : against such sophistry we protest with 
 peculiar emphasis, when it forms the basis of an 
 ignominious and offensive charge. 
 
 You may, perhaps, be disposed to maintain, 
 that you have proved our inconsistency. If to 
 affirm, that body and mind are each governed by 
 necessary laws, but that necessity of operation 
 does not imply identity of result, if this be incon- 
 sistency, we are, indeed, guilty of the charge. If 
 to affirm, that there exists the same constant con- 
 junction between motives and actions, as between 
 physical causes and their effects, but that we are 
 not therefore to expect the same effect from the 
 operation of a motive on an intelligent being, as 
 from the operation of a physical cause on a physi- 
 cal substance, if this be inconsistency, we are 
 unquestionably inconsistent. If, because we con- 
 sent to determine the effect of a physical cause by 
 physical experiment, but refuse to refer to phy- 
 sical experiment, in order to ascertain the effect of 
 a moral cause, we be guilty of inconsistency, then 
 
352 
 
 indeed your imputation is well founded. If \ve 
 deny, that the laws of mind are deducible from the 
 laws of matter, or the laws of volition from the laws 
 of motion, and yet affirm, that mind and matter 
 are each governed by necessary laws, if this be 
 inconsistency, we must admit the charge. Or, if 
 a philosopher is to be convicted of inconsistency, 
 because he chooses to distinguish between analogy, 
 and identity of operation, then every Necessarian 
 must bow with submission to your accusation. 
 Habes confitentem reum. 
 
 If you know any other ground, for 'charging us 
 with inconsistency, you will pardon me, if I 
 request, that you will have the goodness to state it. 
 I must intreat, however, that in doing this, you 
 will be careful, not to beg the question. I must 
 request, that you will not upbraid us with inconsis- 
 tency, when we acknowlege the irresistible force 
 of a Mathematical demonstration, and yet refuse 
 our assent to yours. This argument we cannot 
 admit. The semblance of mathematical evidence 
 differs widely from the evidence itself. It is not the 
 arrangement of so many AA and BB, XX and 
 YY with +, , ==, &c. which forms a mathe- 
 matical demonstration, or algebraic analysis, but a 
 continued series of axioms, or of truths resolvable 
 into axioms, forming one connected chain of intu- 
 itive and irresistible evidence. Each proposition, 
 by a necessary and unalterable relation, results 
 
353 
 
 from one or other of the preceding truths ; and 
 the conclusion possesses all the evidence of intui- 
 tive certainty. 
 
 You ask me, if I know of any higher evidence 
 in science, than demonstrative reasoning, founded 
 in axioms, or self-evident necessary truths, and 
 proceeding by necessary consequences at every step 
 to the ultimate conclusion, which it was intended 
 to prove. 
 
 It is answered, that I neither know, nor can 
 conceive any higher, than demonstrative evi- 
 dence. 
 
 You ask, if I admit, that an argumentum ad 
 absurdum, supposing it to be good of its kind, is 
 just as valid, as a direct demonstration. Certainly ; 
 provided it be, as you say, good of its kind. 
 
 You enquire, if " a philosopher may rationally 
 " and candidly refuse his assent to such a demon- 
 " stration, without shewing some error in it." This 
 is truly a very singular question, furnishing no 
 common specimen of the mathematical skill, and 
 logical acumen of its author. An error in an 
 argumentum ad absurdum supposed to be good of its 
 kind ! ! ! An error in an argument, equal in evi- 
 dence,, as you say, and just as valid, as a direct 
 demonstration !!! What can this mean? Do explain 
 to me, how such a demonstration can admit an 
 error. I have always understood, that there can 
 be no error in a good direct mathematical demon- 
 let. Z 
 
354 
 
 station, and therefore no error in a deductio tfd 
 absurdum " good of its kind." But I suppose you 
 mean (if you could for a moment divest yourself of 
 the persuasion, that your argument is Mathemati- 
 cally correct) not a deductio ad absurdum " good of 
 *' its kind," this compelling our assent, but something 
 that looks like a deductio ad absurdum something 
 that its author conceives to be, and is pleased to 
 call, a Mathematical demonstration. Now, that a 
 philosopher may candidly and rationally refuse his 
 assent to such an argument, without stating his 
 reasons for that dissent, is a truth, which cannot, 
 I conceive, be reasonably disputed. The detec- 
 tion of an error in any pretended demonstration, 
 imposes no obligation to expose that error: No 
 man surely is bound to waste his time, in explain- 
 ing the ground for his dissenting from an argument, 
 though professedly mathematical, the fallacy of 
 which, he is fully persuaded, every competent judge 
 of the question, with due attention, cannot fail 
 to perceive. 
 
 You ask, if / think Dr. Priestley and his friends 
 <c have any peculiar, or personal, exemption from 
 " those rigorous laws of human, thought, or prin- 
 " ciples of reasoning and conduct, which, from the 
 " earliest ages of science, have been considered as 
 " universal and indefeasible." This is, indeed, a 
 very extraordinary question; nor is it easy to divine, 
 nnrnop it is nroposed. "Exempt- 
 
355 
 
 '" ed from the laws of human thought?" Exempted 
 by whom ? or by what ? By nature ? The rery 
 conception is extravagant. By human consent? 
 The supposition of its possibility is absurd, and 
 ridiculous. No man, who is neither a fool, nor a 
 bigot, will either need, or arrogate, the licentious 
 privilege. 
 
 The observations, which follow this truly phi- 
 losophical query, are worthy of their author. No 
 person, I am sure, will envy the feelings, which 
 could dictate, or respect the intellect, which could 
 approve, such rudeness and illiberality. You are 
 to be excused, forsooth, for charging philosophers 
 with deliberate falsehood, because they, despising 
 such an imputation, and knowing, what every 
 person, but yourself must have known, that it 
 would cover its author with shame, did not chuse 
 to divert their attention from other pursuits, to 
 expose the fallacy of your argument, and thus, as 
 you say, repel the charge ! 
 
 You ask, if my Essay, especially that part of it, 
 which relates to you, and your demonstration, be 
 not a complete proof, that you were right in that 
 opinion ; and add, that I soon found it necessary to 
 attempt, what I never can accomplish, such a 
 vindication of my great Master, and his doctrine. 
 To what opinion you here refer, it exceeds my 
 penetration to discover ; and if I may judge from 
 
356 
 
 the obscurity, in which the question is involved, 
 I am not sure, that you intended, that I should 
 understand it. The query therefore I must dis- 
 miss unanswered ; and shall proceed to direct the 
 attention of the reader, to an example of rudeness 
 here exhibited (for I will not give it a harsher name) 
 that far surpasses any insolence, which I could 
 conceive the most petulant mind to be capable of 
 indulging. You ask, if my Essay is not a proof, 
 that I soon found it necessary to vindicate the cha- 
 racter of my great Master. Now, Sir, I condescend 
 not to enquire, what you will think, or feel (for 
 that is comparatively of little moment) but what 
 will every reader, who values character, and re- 
 spect truth, think of your rude and unjust assertion, 
 (for your question must be so construed) when I 
 assure him, that my answer to your Essay was 
 written, before I knew aught of Dr. Priestley, 
 unless from his writings. Where then was that 
 necessity, which, with so little regard to fact, 
 you impute to me, of defending the sentiments, or 
 character, of a man, whom I had never seen but 
 twice, to whom I had never spoken, and with 
 whom I could not claim the slightest acquaintance? 
 Have I not a right to enquire, on what authority, 
 you have advanced an assertion as insolent, as it 
 is groundless? How does my Essay prove, that 
 1 soon found it necessary to vindicate Dr. Priestley? 
 
357 
 
 Do not deceive yourself: Dr. Priestley needed not 
 my feeble aid against such an adversary, as he 
 would have encountered in Dr. Gregory. 
 
 Conscious rectitude is generally believed to 
 invest its humblest possessor with a proud supe- 
 riority over an insolent and unjust accuser; and 
 truth will assert her pre-eminence over error and 
 falsehood. But, were I to presume to offer coun- 
 sel, or admonition to Dr. Gregory, I feel, that, 
 while the suggestions of a monitor are frequently 
 ungracious, I should be assuming a liberty, to 
 which I possess no right, and which it would ill 
 become me to exercise. But, Sir, give me leave 
 with due submission, to make one observation, 
 the justness of which, the reflections of calm and 
 sober reason will not fail to confirm, namely, that 
 rash, illiberal, and unfounded assertions reflect 
 discredit on their author, betraying a spirit highly 
 offensive, and justly reprehensible. To attempt 
 to defend an error by bold and unwarranted asser- 
 tion is to aggravate, not to extenuate, a fault, 
 while it begets a suspicion, that the offender is 
 conscious of his offence, but wants the candour 
 and the magnanimity to acknowlege it. 
 
 You ask, " If Dr. Priestley's own conduct, in 
 " professing to approve my Essay, and urging me 
 " to print it, knowing, as he must have done, 
 " whatever / may do, that it is composed in open 
 ' violation of the most familiar, and best established, 
 
358 
 
 " principles of reasoning, as well as consummate 
 <c disingenuity towards yourself, be not a very 
 " strong additional proof of the same thing." Here 
 we have exhibited another specimen of that rude- 
 ness of temper, and that illiberal spirit, which 
 sully almost every page you write ; combined with 
 a weakness of argument, which only exposes the 
 enormity, which it attempts to defend. Whether 
 my Essay violates the acknowleged principles of 
 reasoning is a question, which must be determined 
 by examination, and not by assertion. Whatever 
 may be either its merit, or its defects, and though 
 it may not be composed in strict harmony with 
 your principles of reasoning, devoid also as it is 
 of all the pomp of mathematical diagrams, and 
 algebraic formula, it contains, I humbly conceive, 
 a satisfactory refutation of your argument. Nay, 
 I trust, it has not only exposed the fallacy of your 
 demonstration, and shewn it to be the spurious 
 offspring of a wretched alliance, but has proved 
 also, that you have egregiously misunderstood 
 the very principle, on which your argument is 
 built. And, were I inclined to conform to your 
 example and appeal to authority, I have it in my 
 power to produce such testimonies in opposition 
 to your assertion, the testimonies too of metaphy- 
 sicians, not friendly to my hypothesis, that your 
 dissatisfaction with my reasoning would weigh 
 nothing against their concurrent approbation. If 
 
359 
 
 my Essay, as you affirm, so outrageously violates 
 the established principles of reasoning, it is surely 
 surprising, that such palpable sophistry should 
 escape the detection of several zealous friends to 
 your hypothesis, and at the same time competent 
 judges of the controversy, who-, while they question 
 the truth of our doctrine, candidly admit, that I 
 have completely subverted your argument. 
 
 But all this is vain affectation and ridiculous 
 parade. One sound argument will outweigh a hun- 
 dred authorities; and when I perceive an eagerness 
 to refer to authority in support of a hypothesis, or 
 in corroboration of an argument, I am inclined to 
 suspect, that the writer feels the weakness of his 
 own cause, and is fain to have the countenance 
 of opinion, when he cannot have the aid of solid 
 reasoning. 
 
 But, though I reject all appeals to authority as 
 vain and impertinent in philosophical discussion, 
 I may be pardoned for retorting this species of ar- 
 gument on an adversary, who adduces it in his 
 own favour, nay adduces it with the most ostenta- 
 tious confidence, as if modesty should be ashamed 
 to doubt its validity, and reason itself bow sub- 
 missively before it. But I will now return to the 
 main question. 
 
 You have very ungenerously and insultingly 
 charged all Necessarians, and among them Dr. 
 
360 
 
 Priestley especially, with deliberate disingenuity 
 and falsehood. You told him, that he would be 
 called upon to " vindicate his character, not merely 
 " in point of understanding as a philosopher, but 
 " in point of probity and veracity, as a man." You 
 now attempt to justify this most insolent attack ; 
 and in this very attempt you repeat the indignity. 
 Language, as I have elsewhere said, really fails 
 us to chastise such rudeness in terms of sufficient 
 sharpness and severity. You insinuate, that he is 
 guilty of wilful and deliberate falsehood by express- 
 ing his approbation of my Essay, for " you add," 
 he must have " known, that k was composed in 
 " open violation of the best established principles 
 " of reasoning." Now, permit me to ask, on what 
 authority do you presume to assert, or how have 
 you learned, that Dr. Priestley had the knowlege, 
 which you here ascribe to him ? Is Dr. Priestley's 
 testimony to be discredited, or his veracity to be 
 questioned, because he entertains an opinion con- 
 trary to yours, respecting the character of my 
 Essay? Or is he to be branded with the most 
 odious of all imputations, because he affirmed 
 that I had completely subverted your demonstra- 
 tion ? The very conception is too monstrous to be 
 entertained by any man, who respects either his 
 own, or the reputation of his neighbour. 
 
 You seem to be impressed with strong doubte 
 
361 
 
 whether Dr. Priestley understood the difference 
 between Demonstrative, and Inductive reasoning. ' 
 You observe, that he was more accustomed to 
 Metaphysical, than Mathematical speculations,* 
 and with that modesty and candour, which are 
 peculiar to yourself, you have told us, that Dr. 
 Priestley had little " taste for mathematical rea- 
 " soning, or indeed for strict reasoning of any 
 " kind." 3 This is a sentiment which needs no 
 comment, and is truly worthy of its author. How 
 much it is to be regretted, that he was not furnish- 
 ed with some of your instrument a mentis ! ! ! 
 
 But, if it be true, as you represent, that Dr. 
 Priestley had but little taste for strict reasoning of 
 any kind, would it not have been more charita- 
 ble, and more congenial with the spirit of philoso- 
 phy, as well as with the principles of common 
 decency, to have ascribed Dr. Priestley's appro- 
 bation of my Essay to his inability to detect my 
 errors, or to his incapacity for " strict reasoning," 
 rather than to a fixed principle of disingenuity, or 
 falsehood? To impeach a philosopher's under- 
 standing, or to question his talent for mathematical 
 investigation, though this certainly may give 
 offence, is a charge much less odious, than a direct 
 imputation on moral character. 
 
 But Dr. Priestley is not only to be suspected as 
 
 1 Vol. j. p. 291. a Vol. i. p. 300. * Vol. I. p. 302. 
 
having " little taste for strict reasoning of any 
 " kind," that is, " reasoning from necessary conse- 
 " quences ;" he must also be charged with the 
 basest of all vices. He must be guilty of mala fides. 
 It cannot be otherwise. He asserted two wilful 
 and deliberate falsehoods Indeed ! What are 
 they? Reader, you shall hear. 1st. He professed 
 to believe in the doctrine of Necessity, after Dr. 
 Gregory had mathematically disproved it; nay, 
 what enormously aggravates his offence, he pro- 
 fessed to believe it, even before the learned demon- 
 stration had been exhibited by its author. Base 
 hypocrite ! he must be guilty. 2dly. He approved 
 an Essay, written partly in refutation of Dr. Gre- 
 gory's work, though he knew, that it violated every 
 principle of sound reasoning. Unpardonable dis- 
 simulation ! He must be guilty : Away with him. 
 But, Sir, there is an old, though I trust, not 
 antiquated maxim, Fiatjustitia, ruat ccelum : and 
 it is essential to justice, you well know, that both 
 parties be impartially heard. Now, be assured, 
 it is remote from my intention to give you any 
 offence, or wantonly to disturb that self-compla- 
 cency, which you very naturally feel, on contem- 
 plating your elaborate and learned demonstration ; 
 but, if you will condescend to bear with me, I 
 would take the liberty to ask the following question : 
 " Is it quite certain, that your argument is a Ma- 
 " thematical demonstration?" If it is not, Dr. 
 
363 
 
 Priestley ought not to be reproached with disin- 
 genuity, if he did not yield to it, that assent, which 
 you seem to demand. It has always been under- 
 stood, and you yourself acknowlege, that a Mathe- 
 matical demonstration compels belief. I never 
 heard of any argument of this kind being* disputed 
 by any person, who was competent to understand 
 it. Yet it would appear from your own account, 
 that some Mathematicians, and in particular " one 
 " good Mathematician, could not be reconciled to 
 " your Mathematics." This looks very inauspicious. 
 Has this gentleman questioned the truth of Euclid's 
 celebrated 47th Proposition ? I presume, he has 
 not; otherwise you would not have pronounced 
 him a good Mathematician. Why, then, nay 
 how could he possibly refuse his assent to your 
 demonstration, if it be accompanied with all the 
 cogency of Mathematical evidence? Should not 
 this refusal have rendered you somewhat distrust- 
 ful of the validity of your argument ? Should it 
 not have created some apprehension, that, how 
 specious soever your demonstration might appear, 
 some fallacy must lurk at the bottom ? Should it 
 not have occurred to you, that to charge Dr. Priest- 
 ley with dissimulation and falsehood, because he 
 refused his assent to an . argument, which had been 
 rejected also by several Mathematicians, to whom 
 you had submitted it, would be a harsh, an un- 
 generous, and possibly an unjust imputation? 
 
364 
 
 Confident as you are in the strength of your 
 demonstration, the rejection of your argument by 
 one good Mathematician, as demonstrative or 
 conclusive, should have served as an admonition, 
 that the error might possibly be with you, and not 
 with Dr. Priestley. 
 
 Nay, you inform us, in your Introduction, that 
 after having submitted your demonstration to the 
 judgment of an able Mathematician, and also pro- 
 found Metaphysician, and after he had rejected it 
 as fallacious, you prevailed on him to submit his 
 objections to " two of the ablest men, and best 
 " scholars, and best Mathematicians, and of the 
 " most extensive acquaintance with various 
 " branches of science, that you had ever known." 
 Well ; what was their opinion ? Did they concur 
 with you? Did they dissent from this eminent 
 Mathematician this accomplished scholar this 
 profound Metaphysician? No You own, that to 
 your great astonishment, they approved his objec- 
 tions. This does not surprise me; the contrary 
 opinion would have surprised me exceedingly. 
 And after this acknowlegement, Sir, in order to 
 throw an air of ridicule over one of these gentle- 
 men, you are pleased contemptuously to call him, 
 a Metaphysico, MatJiematico philosopher. The 
 rejection of your demonstration by three such men, 
 as you represent them to be, methinks, should 
 have taught you, that your argument was a mere 
 
305 
 
 fallacy ; and that a philosopher might be pardoned 
 for refusing his assent to it, without incurring the 
 imputation of mala fides. Who ever heard of three 
 able Mathematicians rejecting a Mathematical 
 demonstration ? 
 
 The second ground, on which you charge him 
 with disingenuity, is the approbation, which he 
 expressed of my answer to your Essay. This 
 ground, however, is clearly untenable, until you 
 have proved, 1st. That my refutation does indeed 
 violate the best established principles of reasoning; 
 and 2dly. That Dr. Priestley, though a person, as 
 you represent him, possessing but little taste for 
 strict reasoning, or reasoning by necessary conse- 
 quences, was, notwithstanding, capable of detecting 
 its errors. When you have established, by incontest- 
 able proof, that such is the character of my answer, 
 and that he knew it to be such, your charge against 
 him of disingenuity, as far at least, as this single 
 question is concerned, may be admitted to be just. 
 
 But this painful subject is not yet to be dismissed. 
 You seem determined, that Dr. Priestley should 
 appear to have been a man, in whom no confidence 
 whatever could be justly reposed. You ask, if 
 " that conduct" (alluding to his approbation of 
 " my Essay) be not complete evidence, that he 
 " was not (as he pretended, and / did not believe) 
 " perfectly indifferent to such charges as that of 
 " mala fides : and that he too felt the irresistible 
 
366 
 
 " necessity of getting his character, if possible, 
 " vindicated per fas, aut nefas. 
 
 I have already exposed to its merited reprehen- 
 sion, your unjust assertion, that I " felt the neces- 
 " sity of vindicating the character of Dr. Priestley." 
 The simple fact, well known to several of my 
 friends in this country, that I knew nothing of 
 Dr. Priestley, except from his writings, when I 
 had finished the prima cur a of my answer to your 
 work, would alone suffice to prove that this asser- 
 tion is wholly unfounded. This fact, coupled 
 with my own positive declaration, that my answer 
 was composed solely with the view of exposing 
 the fallacies of an argument, in which you had 
 prostituted the forms, and violated the principles, 
 of Mathematical demonstration, cannot, I am 
 persuaded, leave a doubt in any candid and impar- 
 tial mind, that your statement is an act of palpable 
 injustice, and, unacquainted as I was with Dr. 
 Priestley, wholly incredible. 
 
 Having repelled this imputation, I am desirous 
 to know, how Dr. Priestley's approbation of my 
 Essay proves, that he too felt the necessity of hav- 
 ing his character vindicated. Be pleased to shew, 
 by what sort of argument you establish this con- 
 clusion. Did he request of me to attempt his vin- 
 dication? Nay did he know me even byname, 
 till my book was nearly ready for the press ? How 
 then does his approbation of my *" v r.onvict 
 
367 
 
 him of falsehood ? How does it prove, that he 
 was anxious to have his character vindicated from 
 the imputation of mala Jidcs ? Do you mean 
 to admit, that my work, though " composed 
 " in direct violation of the best established princi- 
 " pies of reasoning," did, notwithstanding, vindicate 
 the character of Dr. Priestley, and completely 
 repel your charge ? Or can you reconcile, consist- 
 ently with the plain principles of common sense, Dr. 
 Priestley's anxiety to have my Answer published, 
 with his conviction, that it was palpably sophistical, 
 and incapable therefore of subservingthe hypothe- 
 sis, or vindicating his character ? 
 
 The truth seems to be, that vanity on this, as 
 on some other occasions, has darkened your under- 
 standing. You do not see things, as they are. 
 You publish an argument, which you are pleased 
 to call a Mathematical demonstration. Several of 
 your friends question its validity. They assure 
 you, that it involves a fallacy. It fails to produce 
 conviction. Such an opinion, delivered by com- 
 petent judges of the subject, would naturally make 
 a reasonable man question its validity. But vanity 
 interposes, and in spite of all objections, you per- 
 sist in maintaining it to be a Mathematical demon- 
 stration. Nay you are not satisfied with affirming 
 its perfect correctness and validity ; you pronounce 
 every man, whether friend or foe, who will not 
 assent to it, an arrant dissembler. You threatened 
 
368 
 
 to denounce Dr. Priestley and all other Necessari- 
 ans, as men wholly devoid of veracity, if they 
 should dare to profess the doctrine of Necessity, 
 and you had the vanity to believe, that such a 
 threat, proceeding from you, and enforced by a 
 Mathematical argument, would petrify with ter- 
 ror the most intrepid and obdurate Necessarian. 
 You had the vanity to suppose, that Dr. Priestley 
 would be alarmed for the safety of his character, 
 and that he must of necessity publish an answer 
 either by himself, or by proxy, under the pain and 
 penalty of everlasting disgrace. Now, I do not 
 mean to deny, that a sentiment of this kind is ex- 
 tremely natural, in a person of your particular tem- 
 perament. I am still less disposed to deny, that 
 every individual ought to esteem probity and 
 honour as his brightest ornaments, and to dread 
 the just imputation of falsehood, as his greatest dis- 
 grace. But in all cases, where character is assailed, 
 especially when any specific charge is alleged, it is 
 natural for the person attacked, to consider these 
 two things : 1st. the character of the person, who 
 advances the charge ; and 2dly . the evidence, if any, 
 by which he attempts to support it. If the assail- 
 ant is known to be a man of intemperate feelings, 
 and prone to be hurried by impetuosity of passion 
 into precipitate and calumnious accusations, or if 
 his character be notoriously unprincipled, or the 
 evidence, on which the imputation is founded, gla- 
 
369 
 
 ringly inconclusive, or manifestly false, the charge, 
 in such circumstances, may be safely treated with 
 silent contempt. Now, Sir, it is remote, believe 
 me, from my intention to insinuate a suspicion 
 against your veracity, or moral character, when 
 you made your indecorous attack on Dr. Priestley 
 Nor, though the charges solemnly alleged against 
 you, since that time, by the College of Physicians 
 at Edinburgh, form a subject of useful, but melan- 
 choly contemplation to every reflecting mind, do 
 I consider them as matters for my discussion here. 
 Powerfully, indeed, are they calculated to impress 
 the most salutary lessons of charity, and humility, 
 and to check the vaun tings of pride, vanity and 
 presumptuous rudeness. I shall only observe, 
 that so weak, and so inconclusive is the evidence, 
 on which your accusation of disingenuity against 
 Dr. Priestley is founded, that, had you alleged the 
 same charge against myself, in similar circum- 
 stances, I should have treated it with silent dis- 
 dain, and suffered it to perish by its own vanity. 
 
 Your attack, therefore, how highly soever you 
 might think of it, was in truth like old Priam's 
 feeble dart telum imbelle, and unless to its author, 
 perfectly harmless. You valued your threat, as you 
 estimated your demonstration, much too highly. 
 This in Dr. Gregory is only consistency of charac- 
 ter, and perfectly natural. But you erred egregi- 
 ously, when you supposed, that others would rate 
 Let. 2 A 
 
370 
 
 them at the same value. Liberal men condemned 
 your charge, they laughed at your threat ; and I 
 have never met, but one single individual, who did 
 not consider your argument as wholly fallacious, 
 and as answering no other purpose, than the 
 exhibition of its author in no very favourable light, 
 either as a man, or as a philosopher. 
 
 You tell me, that your reason for considering so 
 minutely the " strange supposition," that Dr. 
 Priestley was exempted from the common laws of 
 human thought, and moral conduct, is, because in 
 your apprehension, it is only on some such supposi- 
 tion, that the parasites of Dr. Priestley can have 
 even a pretence for blaming you, on account of your 
 procedure towards him. Who the parasites of Dr. 
 Priestley are, or were, I do not presume to deter- 
 mine, having never heard of their existence till 
 now. But this I do know, that this single obser- 
 vation would sufficiently mark the character of its 
 author. This also, I know, that there is no neces- 
 sity for resorting to any such foolish and ridiculous 
 supposition, to account for the universal and me- 
 rited castigation, which your illiberal and unjust 
 imputation received. For it is highly necessary, 
 that you should understand, that the censure of 
 your conduct was not confined to the friends 'of 
 Dr. Priestley. I know no person, to whatever 
 sect or party he might belong, Churchman or Dis- 
 senter, Necessarian, or Libertarian, Jew or Gen- 
 
371 
 
 tile, who did not condemn in the severest terms, 
 your rude, ungenerous, and absurd imputation. 
 It is true, I have met with some, who laughed at 
 the folly and extravagance of the man, who could, 
 on no better ground, than conceit in his own argu- 
 ment, allege such a charge ; and they have animad- 
 verted with some pleasantry on the structure of 
 that mind, which could conceive the idea, that 
 such an imputation was either just or generous or 
 credible. Bat these were, doubtless, the " para- 
 sites" of Dr. Priestley ; and therefore their opinion 
 is not to be regarded. 
 
 But in one of your written communications, 
 in answer to my letter, reminding you of your 
 engagement in this communication, which you 
 give me leave to cite, you are pleased to 
 inform me, that you are " a passionate lover of 
 " that recreation, which you sometimes call meta- 
 " physical dissecting, and anatomising," and with 
 your wonted courtesy condescend to acquaint me, 
 that, according to your conception your oppo- 
 nent, under adroit and skilful hands, would make 
 an excellent figure. Now, Sir, as you inform me 
 also that " Physic is your trade and Metaphysics 
 " your amusement," it might be a profitable opera- 
 tion to yourself, capable as you are with your knife, 
 of " dividing asunder between soul and spirit," if 
 you would take the trouble to anatomise the men- 
 tal constitution of that philosopher, who believes, 
 
372 
 
 that a mathematical demonstration compels assent, 
 yet affirms that to be a mathematical demonstration, 
 which does not compel assent who affects a won- 
 derful respect for justice, yet wantonly and perti- 
 naciously violates its dictates who knows, that 
 many of his own friends believe in the doctrine, 
 which he impugns, yet charges them on that 
 account with mala Jides who speaks of these 
 friends with respect, yet brands them with the im- 
 putation of disingenuity who says, he intended 
 no injustice to one of his opponents, yet charges 
 him with falsehood, because, forsooth, he would 
 not refute his demonstration who, in defence of 
 this conduct aggravates the fault, by repeating the 
 insult who desires to have his own assertions be- 
 lieved on his own simple authority, while he him- 
 self will not believe the positive declarations of 
 others, if unfavourable to his own vanity who has 
 the superlative modesty to conclude, that, when 
 two philosophers would not take " the trouble of 
 shewing the fallacy of his argument, the sole rea- 
 son was, that they were incapable of doing it- 
 who maintained, that a sophism was a demonstra- 
 tion, because he believed it to be so. 
 
 You tell us, that, if deliberate inconsistency in 
 Dr. Priestley be an evidence of mala fides, especially, 
 as he must have perceived intuitively the falsity of 
 the necessary consequences of that doctrine, which 
 he professed to believe, you cannot conceive, what 
 
373 
 
 reason or pretence, he or any of his " parasites" 
 can have to blame you for giving him a fair oppor- 
 tunity to prevent sucli a charge, if he thought it 
 unjust. This apology, Sir, will not serve you in 
 any stead. You must prove the inconsistency ; 
 nay it is incumbent upon you to shew, that Neces- 
 sarians are more inconsistent than their opponents, 
 otherwise we shall be authorised to retort the argu- 
 ment. Nay, you will be required to shew us, how 
 Dr. Priestley must have perceived intuitively the 
 falsity of the consequences of his own doctrine. 
 This is a sort of intuition, or rather I should say, 
 a degree of it, which I never experienced in myself, 
 though I am a believer in Necessity, nor in any of 
 my acquaintance. And I must own, this is some- 
 what surprising, considering the vast pains, which 
 you have taken to improve our intellectual percep- 
 tions. But there is no remedy for innate dulness. 
 You have expended amazing labour, in order to 
 shew us, that the same effects do not follow from 
 the application of physical forces to a physical 
 body, as from the application of motives to an 
 intelligent being; and you have hence inferred, 
 that the principle of constant conjunction between 
 motive and action does not exist. The premises 
 we know from experience, or if you like the expres- 
 sion better, we see intuitively, that the same effects 
 do not take place in both cases ; but we neither 
 perceive intuitively, nor has it yet been demonstrat- 
 
374 
 
 ed, that diversity of result, when either the agents, 
 or the subjects, or both, are different, implies the 
 absence of the principle of constant conjunction. 
 
 But the reason, which you assign for giving him 
 this intimation is superlatively curious and de- 
 mands attention. You inform us, that " you knew 1 
 " very well that Dr. Priestley had gone so far in 
 " the controversy, that he could not retract, being 
 " pledged beyond all possibility of redemption, as 
 " many others have been, not only in point of un- 
 " derstanding, but of veracity, to maintain to the 
 " last, right or wrong, that opinion, which he had 
 " erroneously professed to believe ; and that on 
 " this account it was the more incumbent on you to 
 " give him the earliest opportunity of refuting 
 it." ' 
 
 You labour under a grievous error, if you flatter 
 yourself with the hope, that by rudeness, like this, 
 you can either advance your reputation as a philo- 
 sopher or as a man, or that you can gain assent to 
 the hypothesis, which you are desirous to support. 
 No man, I am persuaded, whatever may be his 
 opinion of the subject of this controversy, will hesi- 
 tate to condemn so injurious and so illiberal an 
 attack on the veracity of Dr. Priestley and other 
 Necessarians. You knew well, that contrary to 
 his own conviction, he would maintain his error. 
 
 1 Essay, Vol. I. Introd. p. 265. 
 
375 
 
 On what evidence is this knowlege founded ? If 
 you are not privileged wantonly to defame the 
 character of others, it is peculiarly incumbent on 
 you to produce' your evidence, if you desire to 
 avert an imputation, highly discreditable to your- 
 self. 
 
 But it is not the insolence of the attack, with 
 which we are at present chiefly concerned. It is 
 the argument itself, which, as I have already 
 remarked, is singularly curious, and for its logical 
 accuracy not unworthy of its author. You have 
 told us, in the passage immediately preceding 
 that, which I have now cited, that Dr. Priestley 
 was a man insensible to argument. If, by insen- 
 sibility to argument, we are to understand, that, 
 which is commonly denoted by it, namely a certain 
 insusceptibility of intellect, or that impenetrability 
 of mind, which renders it incapable of feeling the 
 force of argument, will you explain to me, how 
 you reconcile this peculiarity of mental constitution 
 with your laboured charge of disingenuity and 
 falsehood. If Dr. Priestley was really inaccessi- 
 ble to the influence of argument, and if, after all, 
 which he had read or heard on the subject of this 
 controversy, he still remained unconvinced, by 
 what process of reasoning do you convict him of 
 malajides ? He may have been dull of apprehen- 
 sion ; he may have been hard to be convinced ; 
 
376 
 
 but obtuseness of intellect is not to be regarded as 
 only another name for want of veracity. 
 
 Now, Sir, by advancing two charges evidently 
 irreconcileable, you have placed yourself in a pre- 
 dicament, which most men would consider to be 
 somewhat embarassing. If a skilful mathematician, 
 like yourself, were to undertake the delineation, 
 he might by the help of your own, or some similar 
 diagram, very aptly represent your condition, and 
 its effects. He might, for example, represent the 
 desire to establish the charge of mala Jides against 
 Dr. Priestley, impelling you in one direction, and 
 the desire to fix upon him the imputation, that he 
 was insensible to argument, impelling in a different 
 direction, and yourself, under the influence of 
 these two desires, rushing along the diagonal, and 
 missing both the ends, at which you were aiming. 
 
 But you really knew, that he was inaccessible 
 to argument, and knew also, that he would ob- 
 stinately persist in his opinion, and therefore you 
 condescended to give Tiim an opportunity of doing 
 that, which you were perfectly assured, tlrat he 
 would not do. Now, I am very willing to admit, 
 that this conviction furnished no solid reason for 
 not apprising Dr. Priestley of your intended charge. 
 I am ready to acknowlege, that, however he might 
 act upon the occasion, you had your own duty to 
 perform; yet I cannot see, how the persuasion, 
 
377 
 
 that he would persist in his error rendered it more 
 incumbent on you, ' as you state, to give him an 
 opportunity of preventing the charge. The very 
 reverse appears to me to be the juster conclusion. 
 Had you foreseen, that he would retract his opi- 
 nion, it became then peculiarly your duty to afford 
 him an opportunity of averting the imputation ; but 
 surely, if you certainly knew, as you profess to 
 have known, that Dr. Priestley would pertinaci- 
 ously maintain his opinion, it could not render the 
 duty more particularly incumbent on you. 
 
 But there are two questions, which here natur- 
 ally present themselves, to which I am extremely 
 desirous to have distinct answers. 1st. How did 
 you learn, that Dr. Priestley would not retract his 
 opinion? Be pleased to favour me with an answer 
 to this question. If you had no private informa- 
 tion on the subject, I should like to know, by 
 what process of reasoning you arrived at such a 
 conclusion. It will not do to appeal to Dr. Priest- 
 ley's mental constitution ; for, proceeding on this 
 principle, you resolve his volitions into the influ- 
 ence of motives, and make the determinations of 
 the will dependent on the state of mind. It will 
 not do to tell us, that Dr. Priestley had uniformly 
 betrayed an insensibility to argument; for, where 
 the will governs, superior to all controul, and is 
 
 1 See Introduction to the Essay, p. 265. 
 
378 
 
 directed by no rule of action, past experience can 
 furnish us with no criterion of its future determina- 
 tions. Where every event is supposed to be con- 
 tingent, and where there is no bond of connection 
 between antecedents and consequents, foresight is 
 impossible, and past experience useless. No 
 sagacity can anticipate the result, if the cause or 
 previous circumstances may with equal probability, 
 produce any one, out of a plurality of effects. Be 
 pleased then to inform me, by what means you 
 knew, that Dr. Priestley would will not to retract 
 his opinion. I am particularly desirous to have a 
 distinct answer to this question. 
 
 You have indeed told us, that you knew Dr. 
 Priestley's mental constitution, that you knew his 
 insensibility to argument, and that you knew also, 
 that he had pledged himself to maintain the hypo- 
 thesis of Necessity. But, if your anticipation of 
 his conduct was founded in the knowlege of any, 
 or all, of these circumstances, whatever you may 
 conceive yourself to be, you are as much a Neces- 
 sarian as I am. If you allow, that the will is 
 governed by mental constitution, by the convictions 
 of the judgment or the affections of the heart ; if 
 you admit that the love of fame, a regard to one's 
 " pledge," or any motive whatever determines its 
 volitions, you abandon your own hypothesis. You 
 may indeed please yourself, and amuse your 
 readers, with half-formed theories, by which, in- 
 
379 
 
 fluence, and no influence, is ascribed to motives; 
 but be assured, that no man, unless he will be 
 satisfied with such a hypothesis, as the Indian's 
 elephant and tortoise, will ever assent to such a 
 theory. You may satisfy yourself with telling us, 
 that the will resembles a judge, and as the latter, 
 though he may generally decide according to 
 evidence, may notwithstanding decide against it, 
 so the will though generally governed by the 
 strongest motives, is yet voluntarily so governed, 
 and may, if it please, determine in opposition to 
 them. This, I say, you may tell us ; but is there 
 any person of common discernment, who does 
 not perceive, that this illustration involves the 
 very absurdity, which it is intended to remove? 
 Has the judge no motive for deciding against 
 evidence? Has the will no motive for resisting 
 the strongest motive? If not, there is an effect 
 without a cause, a motion without a moving power, 
 a volition without a motive. 
 
 In the second place, I am desirous to under- 
 stand, how the veracity of a philosopher can be 
 pledged to maintain an opinion, right or wrong. 
 To renounce a false hypothesis, and to acknowlege 
 an error cannot surely be construed into a breach 
 of veracity. On the contrary, I should be inclined 
 to esteem it a very strong pledge, of candour, in- 
 tegrity and truth. Be pleased then to inform me, 
 how Dr. Priestley's veracity was pledged to persist 
 
380 
 
 in his error; for I frankly confess, that I have not 
 intellect to comprehend it. I can easily imagine, 
 that the retractation of an opinion, zealously main- 
 tained, may be supposed to derogate from the 
 understanding of a philosopher, but it exceeds my 
 powers of comprehension to conceive, how he can 
 be pledged, in point of veracity, to persist in 
 avowing an opinion, which he believes to be false. 
 But the want of a competent knowlege of mathe- 
 matical science, by which I doubt not, you could 
 analytically and diagrammatically explain this 
 problem, is truly a great defect ; I must, therefore, 
 humbly look to you for a scientific explanation of 
 this apparently paradoxical position. 
 
 You say, " you cannot conceive, what reason, 
 " or pretence, Dr. Priestley, or any parasite of his 
 " can have to blame you, for giving him a fair 
 " opportunity to prevent such a charge, if he 
 " thought it unjust." Now, Sir, as far as I know, 
 there is no one, who blames you, for giving him 
 an opportunity of preventing the charge. This is 
 another example of your proficiency in miscon- 
 ception ; unless you intend the observation, as a 
 specimen of your dexterity, in evading the charge 
 against you, and obtruding something in its stead, 
 respecting which no diversity of opinion can exist. 
 We blame you for advancing so injurious an im- 
 putation : we blame you for threatening to advance 
 it, especially as you had been admonished by one 
 
381 
 
 friend, to forbear from such a charge, and by 
 several, that your demonstration failed to produce 
 conviction. Besides, is there candour, is there 
 liberality, is there justice, or common reason in 
 requiring of any man to point out the errors of an 
 opponent, under the penal imputation ofmalajides? 
 Was the time of Dr. Priestley, or is the time of 
 any person, to be taxed at the discretion of every 
 vain, rude, and wordy writer, who takes it into his 
 head to send him his manuscript, denouncing the 
 heaviest charge, if he does not peruse, and refute 
 it? Surely " you say, it must have been very easy 
 " for Dr. Priestley or Mr. Cooper to have pointed 
 " out the errors in your argument, if they (you 
 " mean it) had been liable to such objections, as 
 " those, which I have urged against them (it)." 
 Nothing certainly could have been more easy: 
 but I conjecture, they were desirous to see you in 
 print. 
 
 You say " It is abundantly plain to you, that 
 " neither Dr. Priestley, nor Mr. Cooper, nor any 
 " man, who had, or expected ever to have any 
 " credit, either in point of understanding or know- 
 " lege, or in point of probity and veracity, would 
 " ever have put his name to such a publication as 
 " mine." 
 
 No counsel, which I can offer, can be supposed 
 to be, in your judgment, of any value. But, if 
 there be any person or persons, whose understand- 
 
382 
 
 ing you esteem, they should impress on you the 
 necessity of abstaining from assertions, of the truth 
 of which you have no evidence, but more especially 
 from those, the incorrectness of which you cannot 
 fail to be aware. Rash, intemperate and unfounded 
 affirmations weaken the authority of a writer, even 
 where his statements may be just, and necessarily 
 generate in the mind of his reader some degree of 
 disbelief, in whatever he affirms. 
 
 If my Essay reflect such discredit on my under- 
 standing as you represent, how do you reconcile 
 this censure of yours with your own express 
 acknowlegement of my ingenuity ? Is Dr. Gre- 
 gory privileged to be inconsistent with himself? Or 
 does he claim any exemption from the common 
 rules of human conduct, or the laws of human 
 thought? Were I to adopt your favourite argument 
 ad verecundiam, which I do not much admire, I 
 should reply; If the character, which you give of 
 my Essay, be just, how came it, that this consum- 
 mate ignorance, this palpable sophistry, escaped 
 the penetration of the critics, by whom the work 
 was reviewed ? " Can you conceive, that it was 
 " reserved for you to discover faults so glaring ? 
 " Does it not indicate a very extraordinary degree 
 " of vanity, and arrogance in yon, to suppose, that 
 " you had discovered at once such monstrous 
 " faults in my argument, in which so many of the 
 " ablest men, that ever this country produced, could 
 
383 
 
 " find no error whatever?" (Seepage 241 J Weak and 
 inconclusive as feuch reasoning is, it may be fairly 
 retorted; and if you deny its validity in my 
 defence, you cannot consistently affirm it in your 
 own. But all this, I am well aware, is mere 
 empty parade, and idle vanity. The character of 
 your Essay, and of my Answer, must rest, not on 
 opinions, but facts not on affirmation, but proof. 
 Whatever may be the merit, or demerit of either, 
 it must be established, not by vain appeals to the 
 judgment of others, nor by long querulous charges 
 of misrepresentation, which, when examined 
 amount to nothing, but by intrinsic positive evi- 
 dence. 
 
 Your rude attack on my veracity and probity I 
 might be allowed to treat with silent scorn. Had 
 the attack been made by any other than Dr. Gre- 
 gory, I should have received it with very different 
 emotions. But in what controversy have you been 
 engaged, in which you have not charged your 
 opponents with wilful falsehood? You have 
 even charged the members of the College of Phy- 
 sicians at Edinburgh with insincerity ; and have 
 imputed to them a solemn and deliberate deviation 
 from truth. You speak and write, as if veracity 
 were your peculiar or favourite attribute, and as 
 if dissimulation, and disingenuity formed the lead- 
 ing trait in the character of your opponents. What 
 infatuation ! Called upon by the College to vin- 
 
384 
 
 dicate your veracity, and accused of the most gla- 
 ring misrepresentations and falsehood, you pro- 
 duced a defence, in which misrepresentation is 
 repeated, and sophistry comhined with the main- 
 tenance of a doctrine, which, as the members of the 
 College truly say, deserves for its atrocity the sever- 
 est reprobation. And is this the man, who has 
 the temerity? But I "have said enough, and less 
 in justice to myself, as well as to those, whose 
 veracity you have assailed, I ought not to have 
 said. I shall now only add, that, when you wan- 
 tonly attempt to wound the moral character of an- 
 other, you should bear in mind, that you are in- 
 flicting a deep and irreparable injury on your own. 
 I have said wantonly, not malignantly ; for in charity 
 I am inclined to believe, that charges of disinge- 
 nuity and falsehood are to you become so habitual, 
 that you throw them out at random, heedless of 
 their effects, and insensible of their immorality. 
 
 You say, it is abundantly plain to jou f that 
 neither Dr. Priestley, nor Mr. Cooper would ever 
 have put their name to such a publication as mine. 
 It is impossible not to admire the accomodating 
 perspicacity, and the convenient darkness of intel- 
 lect, with which you are gifted. Things appear 
 obscure and questionable, when there is evidence 
 sufficient for the conviction of any rational man ; 
 and they seem extremely plain to you, when there 
 is no evidence of their truth, nay when you possess 
 
385 
 
 evidence of their falsity. You have said, that it is 
 abundantly plain to you, that Mr. Cooper would 
 not have put his name to such a publication as 
 mine. On what authority do you assert this? You 
 knew nothing whatever of Mr. Cooper's sentiments 
 of my Essay, yet you presume to affirm, that it 
 could not possibly receive his approbation. Now, 
 it happens very unfortunately for your assertion, 
 that the opinion so abundantly plain to you, is 
 contrary to fact. Mr. Cooper's judgment of my 
 Essay is already in possession of the public. In 
 p. 335 of the first volume of his "Life of Priestley," 
 he thus expresses himself: "The doctrine of Neces- 
 " sity has been opposed by Dr. Gregory of Edin- 
 " burgh, with a weakness of argument, and a petu- 
 " lance of language, that place his work in the 
 " lowest rank, among the writers, who haveadopted 
 " the same side of the question." In the following 
 sentence-, he delivers his opinion of my Essay. In 
 this instance, then, you judged without evidence, 
 and the fact, so abundantly plain to you, is con- 
 tradicted by the testimony of Mr. Cooper him- 
 self. 
 
 I shall next enquire, how far your conviction is 
 correct, respecting the opinion of Dr. Priestley. 
 And here, I am persuaded, it will be clear to every 
 impartial reader, that this conviction, the ground 
 of which is so plain to you, is not only founded 
 in no evidence, but is even contrary to that identi- 
 
 2 B 
 
386 
 
 cal testimony, the authenticity of which is admitted 
 by yourself. You say, in your first letter, that you 
 have no reason to question the veracity of Dr. Lind- 
 say and Mr. Paterson. I entirely concur with you. 
 Permit me, then, to ask, what was the report 
 of these two gentlemen, delivered to two friends 
 of your own, as you yourself state, respecting 
 Dr. Priestley's opinion of my Essay. You know 
 this report. You communicated it to me your- 
 self, and at the same time assured me, that you 
 had no reason to question its accuracy. Yet, in 
 defiance of this evidence, and your own declaration 
 in its favour, you affirm it to be abundantly plain 
 to you, that Dr. Priestley would not have put his 
 name to such a publication as mine. Now, Sir, 
 it is pretty evident, that you are here inclosed in a 
 dilemma, from which you will find it somewhat dif- 
 ficult to extricate yourself. You must either main- 
 tain, that Dr. Priestley was a consummate dis- 
 sembler, a thorough-paced hypocrite, approving 
 openly what he secretly condemned, or you must 
 admit, that his declaration was consonant with the 
 conviction of his own mind. If you take the first 
 alternative, and affirm that Dr. Priestley was a 
 man destitute "of moral principle, I desire to know, 
 how his probity was to restrain him from affixing his 
 name to any publication, how base soever. If you 
 choose the other alternative, and acknowlege Dr. 
 Priestley to have been a man of honour, then 
 
387 
 
 but I forbear to prosecute this alternative. That 
 you, Sir, or indeed any man, while he is endea- 
 vouring to degrade the reputation of another, 
 should debase his own character by representations, 
 not merely gratuitous, but even repugnant to facts 
 admitted by himself, is a lamentable example of 
 , the noxious influence of intemperate feeling. 
 When you asserted an opinion of this kind, if 
 better principles had not restrained your pen, you 
 should at least have reflected, that the means of 
 refutation might possibly be in my power. 
 
 Having now replied to your numerous queries, 
 and exposed the futility of your laboured defence, 
 I shall conclude my examination of your fifth 
 letter, with a few observations on the assumed 
 basis of your invidious charge. 
 
 That inconsistency between profession and 
 practice, or that incongruity of sentiment, may, 
 in certain cases, furnish sufficient evidence of dis- 
 ingenuity, is readily admitted ; but that we are in 
 every instance of inconsistency of opinion to infer 
 wilful and deliberate falsehood, would be to assert 
 a conclusion as repugnant to truth, as it would be 
 irreconeileable with the dictates of liberality and 
 justice. If inconsistency were, in all cases, to be 
 regarded, as a proof of mala jides, I apprehend, 
 that there are not many Theologians or Philoso- 
 phers, who would escape the charge. What shall 
 we say, for example, of those Libertarians who 
 
388 
 
 believe, that the Deity foresees all human actions, 
 and that, what he foresees, must infallibly happen, 
 yet that the agent Man may do, or may not doj 
 what the Deity foresees, he certainly will do? Here 
 is involved as gross a contradiction, as ever was 
 proposed to human assent; yet I should offend 
 against the principles of candour and charity, were 
 I to charge Libertarians with deliberate falsehood. 
 Nor do I admit, that inconsistency of practice 
 with theory is universally, or indeed generally, a 
 proof of disingenuity. The practice of no man 
 perfectly accords with his principles. There are 
 moments, in the life of the most consistent human 
 character, when the principles, by which his con- 
 duct is usually regulated, cease to operate. This 
 is a truth, of which every individual, who bestows 
 the least attention on his own conduct, must be 
 fully sensible. And I hesitate not to add, that, 
 in respect to consistency, Necessarians have no 
 reason to shrink from a comparison with their 
 opponents. A Libertarian acts, as if motives 
 governed the will, yet maintains that the will is 
 not governed by motives. With an inconsistency 
 truly surprising, he reasons from motives to actions, 
 and from actions to motives from the action in- 
 ferring the motive, and from the motive the action. 
 He disclaims the doctrine of Necessity, and yet 
 he reasons and acts like a Necessarian. He pre- 
 sumes, that certain motives, addressed to certain 
 
389 
 
 states of mind will be productive of certain actions; 
 and depending, that the result will be such, as he 
 anticipates, he regulates his conduct, agreeably to 
 this expectation. You reckon with no less cer- 
 tainty on the attendance of an auditory at the hour 
 appointed, after your lectures have commenced, 
 than you anticipate the effect of a medicine, which 
 has been uniformly exhibited in given circum- 
 stances, with one and the same result. And, if 
 in the administration of the medicine your expec- 
 tation should, in any case, be disappointed, you 
 do not question the fact, that the medicine acts 
 necessarily, and, in precisely the same circum- 
 stances, must always produce precisely the same 
 effect ; you merely infer, that the intervention of 
 some circumstance in the case of the patient, of 
 which you were not aware, prevented the effect, 
 which you reasonably anticipated. And, if your 
 auditory should at any time absent themselves, 
 you ought, by parity of reason, not to question 
 the necessary connection between their former 
 motives, and the consequent attendance; it is 
 merely to be concluded, that some unusual cir- 
 cumstance had occurred, which had counteracted 
 the operation of the wonted motives to attendance. 
 This too would be your conclusion, a conclusion, 
 however, totally irreconcileable with the hypothesis 
 of Liberty. It is now Saturday evening, and I 
 am as confident, that to-morrow the churches and 
 
390 
 
 chapels, not only in this island, but throughout 
 the Christian world, will be opened, and the peo- 
 ple assemble for divine service, as I am sure, that 
 the sun will rise, or the Thames flow. I am as 
 confident, that, the day following, the gates of the 
 Exchange will be opened, and the usual business 
 of life resumed, as I am sure, that the seasons 
 will continue to move on in regular order. 
 
 It is this uniformity in the operation of moral, 
 as well as physical causes, which constitutes that 
 regularity, and much of that beauty, which we 
 observe in the universe. Dissolve the connection 
 between physical causes, and effects, and you 
 reduce the natural world to a state of chaos and 
 deformity. From the same cause, acting in pre- 
 cisely the same circumstances, might then arise a 
 variety of effects light or darkness, motion or 
 rest, attraction or repulsion, pain or pleasure, life 
 or death. Destroy the connection between motive 
 and action, and the moral world becomes equally 
 a scene of irregularity, and disorder. If the pas- 
 sions, affections, and appetites of our nature, have 
 not each a uniform and definite influence, if bene- 
 volence may intend mischief, anger prompt to 
 forbearance, avarice despise wealth, and ambition 
 spurn power, as accident may be ; all anticipation 
 of human conduct becomes impossible ; experience 
 is rendered fruitless; prudence ceases to be a 
 virtue, it has even no existence ; the principles of 
 
391 
 
 human society are totally subverted, and universal 
 disorder prevails. If I cannot confidently pre- 
 sume, that those, with whom I am connected, 
 will each, in his own sphere, perform certain 
 offices, and fulfil certain engagements, it becomes 
 impossible for me to regulate my own conduct, as 
 dependent on theirs. If I cannot anticipate the 
 effect of any given motive or motives (the term 
 motive being taken in its largest acceptation) with 
 nearly the same certainty, as I anticipate a physical 
 effect from a given physical cause, doubt, perplex- 
 ity, and inaction must be the necessary conse- 
 quences. 
 
 We may call that certainty by which we antici- 
 pate a physical effect from a physical cause, by 
 the name of physical certainty ; and we may dis- 
 tinguish the certainty, by which we anticipate a 
 moral effect from a moral cause, by the name of 
 moral certainty. But the least reflection must 
 convince us, that this is a distinction, which refers 
 solely to our degrees of knowlege, and our capa- 
 city to anticipate, not to any difference in the 
 constancy of that relation, which subsists between 
 the antecedents and consequents, in either case. 
 I may not know how a die, thrown from the hand 
 may turn up, because I cannot foresee the various 
 ways, in which it may impinge, before it rests; 
 the uncertainty, however, is not in the effect, but 
 in my mind ; for its last position is the necessary 
 
392 
 
 consequence of the first impulse, and cannot pos- 
 sibly be different, in the same circumstances. I 
 may be equally doubtful, how a person will act, 
 in a given situation, being wholly unacquainted 
 with his sentiments, temper and disposition^; but 
 these sentiments, this temper, and these disposi- 
 tions, whatever they be, have as definite and 
 necessary an influence in determining the action, 
 as physical circumstances, in determining a physical 
 effect. And, if our anticipation of the conduct of 
 others be more or less certain, as our knowlege of 
 all the previous actual circumstances is more or 
 less correct, and if this anticipation be founded in 
 moral certainty of which there are degrees, in 
 opposition to physical certainty, it is not because 
 the operation of moral, is less necessary or less 
 certain, than that, of physical causes, but because 
 the former are more changeable in their nature, less 
 accessible to examination, and therefore less easily 
 known. 
 
 In fact, we generally find Libertarians them- 
 selves reasoning in this manner. We uniformly 
 find them resolving any deviation from one's usual 
 mode of action into the intervention of some new 
 or extraordinary motive and remarking, that, 
 had they known all the real circumstances, they 
 should have correctly anticipated the result. Is 
 this reconcileable with a self-determining will? 
 When we find a person acting in a way, which 
 
393 
 
 excites surprise, why do we ask, " What could 
 " be his raotive ? ' if the action be not ascribable to 
 the motive as its cause ? Common language con- 
 nects them as cause and effect. If the will decides, 
 not only in opposition to motives, but even with- 
 out a motive, to what purpose do we enquire into 
 the general sentiments and disposition of the agent, 
 and what motives have been addressed to him ? 
 Or how could we infer, that a change of motives 
 could in any case produce a change of conduct? 
 
 I am aware, that Libertarians, being convinced, 
 that to deny the influence of motives would be to 
 resist the uniform evidence of experience, and to 
 impeach the consistency of their own conduct, 
 while to admit their necessary operation would be 
 to abandon their own doctrine, resort to a middle 
 hypothesis. They tell us, that they admit the in- 
 fluence of motives, but they deny that influence to 
 be necessary. This doctrine is, if possible, more 
 absurd than the hypothesis of Liberty. Influence 
 is agency, and all agency must, in its effect, be 
 necessary. In the whole compass of nature, I 
 neither know, nor can I conceive, any energy, 
 any influence, the effect of which is not definite 
 and fixed. Its operation may be counteracted, 
 and overcome by a more powerful agency, but 
 still it has an effect, and that effect, being in the 
 same circumstances uniformly the same, must be 
 regarded, as a necessary effect. If Libertarians 
 
394 
 
 can specify any energy, or influence, either phy- 
 sical, moral, or intellectual, the effect of which is 
 not determinate and necessary, they will discover 
 a principle, of which, I frankly own, that I can- 
 not even form a conception. But let us return to 
 our subject. 
 
 If the will can determine its own volitions with- 
 out a motive, by what data, by what principle, is 
 it possible to anticipate, with even the lowest degree 
 of probability, its determination in any given case? 
 The motives presented to it furnish me with no 
 information ; the will is not governed by motives. 
 Unless, therefore, I can divine, how it will deter- 
 mine, I can know nothing of the result : no human 
 science can enable me to anticipate the determina- 
 tions of a power, independent, and self-governed. 
 It is mere trifling to tell us, that the will determines 
 its own volitions from the consideration of the 
 motives presented to it, though it is not necessarily 
 governed by these. This is to repeat the absurdity, 
 not to remove it. If the will can give either the 
 stronger or the weaker motive the preference, and 
 can determine the choice without a motive for that 
 preference, how am I to foresee with any probabi- 
 lity, which it will prefer? For aught I know, it 
 may be the weaker, or it may be the stronger, 
 just as this capricious and arbitrary power may 
 happen to decide. Experience thus becomes use- 
 less ; and human foresight is an absurdity. From 
 
395 
 
 what has been it is impossible to infer, what will be. 
 Those, with whom I am connected, and on whose 
 conduct my own, in a great degree, depends, may, 
 in given circumstances, have uniformly acted in a 
 certain way ; but this furnishes no ground for pre- 
 suming, that they will, in circumstances precisely 
 similar, act in the same way. The will overrules 
 all motives ; and its wayward determinations no 
 wisdom can foresee. I am left therefore to con- 
 jecture, without the means of conjecturing, how 
 they will act. If I conclude, that the same men 
 addressed by the same motives will adopt the same 
 conduct, I reason as a Necessarian ; for this is to 
 assume the necessary connection between the same 
 previous circumstances, and the same result. 
 
 If it is said, that the will, though not necessarily 
 influenced by the motives presented to it, will 
 naturally adopt the same determination as in the 
 former instances, I answer, that this presumed 
 uniformity or similarity of determination indicates 
 the operation of a more regular and steady cause, 
 than an independent, and arbitrary will. It is 
 certainly irreconeileable with the supposition of a 
 power determining our volitions, sometimes in 
 obedience to motives, sometimes in opposition to 
 motives, and sometimes without a motive. But, 
 waiving this conclusion, which seems necessarily 
 to follow from the presumption here stated, I desire 
 to know, on what the presumption itself is founded. 
 
The will is either governed by motives, or it is not. 
 A middle, hypothesis is absurd. If the affir- 
 mative is maintained, Necessity follows ; if the 
 negative is asserted, Divine Wisdom itself (be it 
 spoken with reverence) could not foresee an effect, 
 resulting from no cause. 
 
 The conduct therefore of a Libertarian, when by 
 the exercise of foresight he endeavours to anticipate 
 the actions of others, or presumes that, in given 
 circumstances, they will act in a certain way, is 
 utterly irreconcileable with his own hypothesis. 
 Unless he reason from motives to actions, unless 
 he infer, what will be the result, from his knowlege 
 of the previous circumstances, believing, that there 
 exists between them a constant connection, and 
 that his anticipation will be more or less correct, 
 as his knowlege of all the actual previous circum- 
 stances is more or less accurate, unless he reason 
 on this ground, to conjecture the conduct of others 
 with the lowest degree of probability, is wholly 
 impossible. The Libertarian does reason thus nay 
 he is compelled to reason thus ; and his general 
 conduct, as well as his sentiments, are in this 
 respect chargeable with inconsistency. He believes, 
 that the Deity is omniscient ; he believes that he 
 foresees every event, and that his foreknowlege is 
 infallible; while he at the same time maintains, 
 that the will of man is free to do, and actually 
 may do, what the Deity foresees, that he will not 
 
397 
 
 do. As a moralist, he labours to inculcate virtuous 
 principles, to subdue malevolent passions, and to 
 strengthen the benevolent affections of the heart, 
 persuaded, that if he can establish the latter, or 
 give them a decided ascendency, the conduct will be 
 virtuous ; and yet he believes that the state of the 
 heart and its affections, with our notions of good 
 and evil, have no necessary connection with the 
 conduct, and that the self-determining will guided 
 by no rule, but its own arbitrary authority, may 
 decide in favour of virtue or vice, without any 
 motive whatever for the preference. As a critic 
 he requires that the conduct, and sentiments of 
 every person in the fable shall be consonant with 
 his moral and intellectual character, and pro- 
 nounces them unnatural,, when they do not mu- 
 tually accord ; and yet he believes that there exists 
 no necessary connection between a certain state 
 of heart or mind and a certain system of manners. 
 As a statesman, he believes, that like feelings, 
 and passions have, in all ages and nations, pro- 
 duced, and will continue to produce, like events, 
 and that the earthquake, the volcano and the 
 hurricane, are not more certain in their operation, 
 than the exasperated passions of a turbulent and 
 seditious people ; and yet he believes, that ambi- 
 tion and avarice, anger and revenge do not neces- 
 sarily and definitely affect the conduct. As a manu- 
 facturer, or as the master of a family, he anticipates 
 
398 
 
 the labour of his servants with the same certainty, 
 as that the wind, or the water, or the steam will 
 move his machinery, or that the fire will prepare 
 his dinner. And if in any case his expectation is 
 disappointed, he never questions the operation of 
 the motives ; he merely infers, that some new mo- 
 tive must have presented itself, which he did not 
 foresee, and overcame the motives, by which they 
 were usually governed. 
 
 These are far from being the only examples, 
 which might be adduced to shew, that the practice 
 of a Libertarian is at variance with his principles. 
 These, however, may suffice to prove, that the 
 charge of inconsistency may with peculiar effect be 
 retorted on himself; but it would be an unpardon- 
 able violation of the sacred principles of charity 
 and justice, if any Necessarian were to construe 
 this inconsistency into an evidence of deliberate 
 disingenuity or falsehood. 
 
 It has been observed, that the will is either go- 
 verned by motives, or it is not, and that a middle 
 hypothesis is absurd. Some Libertarians, however, 
 finding it impossible to remove the objections, to 
 which the general hypothesis is liable, endeavour 
 to evade them, by adopting an intermediate opi- 
 nion. They acknowlege, as I have remarked, 
 the influence of motives, but they deny the neces- 
 sity of their operation. The will, say they, deter- 
 mines its own volitions, according to the motives 
 
399 
 
 presented to it, and has always a regard to these mo- 
 tives, though it is not necessarily governed by their 
 influence. " The power of self-determination," says 
 Dr. Price, " wants an end and rule to guide it, but 
 " no certainty of its being exerted agreeably to a 
 " rule, can have the least tendency to infringe, or 
 " diminish it." Here under a specious assemblage 
 of words may be detected a palpable contradiction. 
 Let any Libertarian explain, in simple and intelli- 
 gible language, how the exertions of the will, if 
 resulting certainly from any law, or regulated by 
 any rule, can be reconciled with the doctrine, that 
 the will acknowleges no law, but its own will. 
 Let it be explained also, what he means, in consis- 
 tence with his hypothesis, when he observes, that 
 the will determines its own volitions with a regard 
 at the same time to the motives presented to it. 
 For, as Dr. Priestley has justly remarked, there 
 seems no difference between saying, that the 
 motives determine the will, and the will determines 
 itself from the motives. If I determine on A in 
 preference to B, from a view of the motives pre- 
 sented to me, the motives may strictly be said to 
 be the cause of my determination. If the motives 
 are supposed to be contemplated by the mind, but 
 not to produce any definite and necessary effect on 
 its volitions, it evidently follows, that the will de- 
 termines, without paying any regard to the motives. 
 If a judge, after hearing the evidence on both sides, 
 
400 
 
 were to give a decision in favour either of A, or 
 of B, according to the whim'of the moment, or his 
 own arbitrary determination, could it be said with 
 any propriety, that he decided according to his 
 view of the evidence ? If the agent contemplates 
 the motives, but the will, by its own arbitrary deci- 
 sion, prefers this to that motive, can it be said with 
 any truth, that the volition was determined by 
 the agent agreeably to his view of the motives ? If 
 motives have any influence whatever on the will or 
 its determinations, if it be not a necessary influence, 
 let the Libertarians explain both its nature, and its 
 extent. 
 
 But in order to bring the question concerning 
 this half-formed hypothesis to a fair issue, leaving 
 no room for ambiguity or evasion, I shall suppose,, 
 that I am placed in a situation, where the motives 
 A prompt me to one action, and the motives B 
 incline me to another action, can I, after viewing 
 these motives, prefer A to B, or give an ascendency 
 to either without a'motive for that preference t Let 
 it be granted, that the will determines, or chooses. 
 Can it determine, or choose, or prefer without 
 a motive ? If it is answered in the negative, it fol- 
 lows, that the determination is produced by the 
 motive. If the answer is affirmative, it is evident 
 there is a volition that is a change, without any 
 cause of that change. It is vain to urge, that the 
 agent himself is the cause. He can no more be the 
 
401 
 
 cause of a volition, than he can be the cause 
 of a judgment. He wills from motives, as 
 he judges from evidence. His approbation or re- 
 jection of this or that action as necessarily results 
 from the previous circumstances, as his belief or 
 disbelief of this or that proposition results from the 
 evidence submitted to his consideration. He him- 
 self can be the cause of neither the volition, nor 
 the judgment. If a man, famishing with hunger, 
 should, on seeing food, desire or will to have it, 
 can we, without a perversion of reason and common 
 language say, that he is the cause of that desire, or 
 of that volition? There is a gross impropriety, if 
 not absurdity in the very conception. Every vo- 
 lition is the effect, not of the agent himself, but of 
 some desire in that agent to obtain some probably 
 good, or to avoid some probable evil. 
 
 Thus, it is evident, that the middle hypothesis 
 involves the very absurdity, which it professes to 
 remove. 
 
 Let. 
 
FROM t>R. GREGORY. 
 
 LETTER VI. 
 
 SIR, 
 
 X ou have thought fit to charge me with extreme 
 vanity, arrogance, and ostentation. I give you all 
 due credit, not so much for sincerity, as for inven- 
 tion and genius, in that strong accusation ; which 
 has this very peculiar merit, that it is advanced 
 confidently, not only without any evidence, but in 
 direct opposition to the most complete evidence 
 that can be desired or conceived. 
 
 As to what y6u call ostentation, I never could 
 have guessed what you meant by it, if you had not 
 afforded me some assistance, by that clause of 
 your first paragraph, in which you are pleased to 
 say that my illustrations are seemingly not so much 
 calculated to elucidate the subject, as intended to ' 
 excite your wonder at my extensive knowlege. I 
 assure you, that till I read that paragraph of your 
 Essay, I never once suspected that they could excite 
 any such wonder; which certainly they never were 
 
403 
 
 intended "to do, and never can do in any person of 
 competent understanding, and acquaintance with 
 natural science. Even you, unfavourably as you 
 seem resolved to think of me in every respect, can- 
 not think me either so ignorant, or so foolish, as to 
 regard any or all of the illustrations I employed as 
 a proof or display of extensive knowlege. To the 
 best of my remembrance and belief, all of them are 
 things, not only well ascertained, but universally 
 admitted, and familiarly known to every person 
 who is engaged in the pursuits of physical science. 
 Many of them, I am sure, are still more generally 
 known ; I mean, to a large proportion of those 
 whom men of science are pleased to call the vul- 
 gar. Many illustrations, and these too derived 
 from various branches of physics, were necessary for 
 my purpose, as announced even in the title of my 
 Essay, and as very fully explained in the plan and 
 conduct of my argument. My demonstrative rea- 
 soning was very abstruse ; and I could not expect 
 it to be much attended to, or even generally under- 
 stood, without very full illustration. Far other helps 
 than A and B, X and Y, or any algebraic signs 
 and symbols, were necessary to render easy, or 
 even practicable, that patient thinking, that com- 
 parison of different relations, and that strict atten- 
 tion to their differences, not to their resemblances, 
 which were wanted for my purpose. No ex- 
 amples or illustrations could have served my pur- 
 
404 
 
 pose, but such as were familiar, and established 
 beyond the possibility of doubt or dispute. 
 
 With respect to the charge of vanity, which yon 
 so strongly urge against me, and which you say 
 my Essay discovers throughout, I am much at a 
 loss to find out to what you allude, unless it be to 
 a circumstance, trivial in itself, to which you seem 
 to allude in the second sentence of that part of 
 your Essay which relates to my argument. In 
 that sentence you are pleased to say, that I have 
 assailed the system of Necessity in a manner some- 
 what new. If this was really your meaning, and if 
 you seriously thought or found that my argument 
 was only somewhat, but not altogether new, you 
 must no doubt have thought me chargeable with 
 great vanity, and you might well have added 
 great disingenuity also, when I said, in the Intro- 
 duction to my Essay, that my mode of reasoning 
 was perfectly new, and even singular ; and stated 
 the novelty and singularity of it as a consideration, 
 which, I conceived, should entitle it to some atten- 
 tion. In my own vindication or excuse, I can only 
 say that I acted bona Jide ; that at the time I pub- 
 lished my Essay,. I firmly believed, and, notwith- 
 standing your strong insinuation to the contrary, 
 do still believe it to be not somewhat, but altoge- 
 ther new and singular. However, as I pretend to 
 no infallibility on such points, I shall most frankly 
 acknowlege ray mistake, as soon as you shall 
 
405 
 
 point out to me any argument or mode of reason- 
 ing in opposition to the doctrine of Necessity, 
 \vhich is either wholly or partly the same with mine. 
 I am sure that not one of the many persons who at 
 my desire perused it, and gave me their remarks on 
 aV before it was published, nor any of those who 
 have perused it, and have communicated their ob- 
 servations on it to me since it was published, ever 
 intimated to me that I had been anticipated in any 
 part of my reasonings. Many of those persons 
 (among the rest, the late Dr. REID of Glasgow, 
 and the late Dr. CAMPBELL, Principal of Maris- 
 chal College, Aberdeen ; the former a keen asser- 
 tor of the Liberty, the latter as keen an assert or of 
 the Necessity of human actions) declared, that it 
 was, in every respect, perfectly new to them. It 
 appears to me impossible, that all, or even that 
 any of those persons should have failed to perceive 
 at once, if any part of my argument had been bor- 
 rowed, without proper acknowlegement, from the 
 writings of others on the same subject. Though I 
 may be mistaken in what I think on this point, I 
 cannot be justly blamed, or charged with vanity, 
 for what I have said or thought with respect to it : 
 and it is incumbent on you, if you wish to escape 
 the charge of disingenuity in that insinuation, which 
 I believe to be peculiar to yourself, either to 
 retract it, or to establish it by complete proof. It 
 is a simple question of fact ; and I shall be happy 
 
406 
 
 to do justice to those who had anticipated me, as 
 soon as you shall enable me to do so, by letting 
 me know who they were, and in what parts of 
 then 1 writings they had reasoned in any manner like 
 to what I have done. 
 
 In other respects, I conceive that the account, 
 which I gave so minutely, of my mode of proceed- 
 ing, of the circumstances which had suggested to 
 me so peculiar a mode of reasoning, and of the 
 various assistances which I had employed, to 
 direct, to verify, and to illustrate my reasoning, 
 might fairly be reckoned much more than sufficient 
 to preclude all suspicions of vanity on my part. 
 
 I began, as you know, by doing justice to the 
 superior talents and knowlege of those whose 
 doctrine I undertook to disprove, and disclaiming 
 all pretensions to superior talents or knowlege 
 myself. I stated explicitly, that, notwithstanding 
 the great talents and knowlege of my opponents, 
 I conceived that I might be right, and they wrong, 
 in our respective opinions, and that I might be 
 able to point out distinctly wherein their error 
 consisted, when I employed certain instrumenta 
 mentis, or expedients to assist and regulate my 
 investigation, which expedients or instruments 
 they had not thought of employing. The great 
 advantage of employing such instruments, and the 
 decisive superiority which it might give to one 
 naturally much inferior to others, I was at pains 
 
407 
 
 to point out, and to illustrate very fully ; not only 
 in the luminous words of BACON, but by some fa- 
 miliar and striking examples. I took care to 
 mention the very minute circumstance, or parti- 
 cular illustration, employed by Dr. REID in one 
 of his works, that first suggested to me that train 
 of thought which you find detailed in my Essay, 
 and which I found it had not suggested to Dr. 
 REID himself. And lastly, I was at much pains 
 to point out, that the argument, or principle of 
 reasoning, which I employed in my Essay, was, 
 originally and essentially, not mine, but SIR ISAAC 
 NEWTON'S, implied, or tacitly assumed by him, 
 in the whole of his Principia. The only difference 
 between his use and my use of those principles is, 
 that he employs them in direct reasoning, on sup- 
 positions which are true in fact, and were believed 
 by him to be true, to demonstrate necessary con- 
 sequences of those true suppositions, which conse- 
 quences must also be true, and are found so when 
 tried experimentally: while I, on the contrary, 
 employ the same principles for the purpose of 
 indirect reasoning, or a deductlo ad absurdum, by 
 necessary consequences from a supposition, which 
 I believe or know to be false, to inferences that 
 may be tried experimentally ; but which are so 
 palpably and ridiculously false, that no person 
 chooses, or has occasion, to try them that way. 
 I can see nothing like vanity in this mode of 
 
408 
 
 proceeding: but, if you do, -I wish you would 
 specify wherein it consists. I wish also you would 
 take the trouble to read again, or, as I suspect it 
 may be, to read for the first time, that section of 
 my Essay (the 15th,) in which the relation between 
 my mode of reasoning and SIR ISAAC NEWTON'S, 
 in his Principia, is not only pointed out, but fully 
 discussed. That section, in your analysis of my 
 Essay, you pass over with a very brief expression 
 of contempt, in these words: " In Section 15th 
 " we find a general illustration of his favourite ar- 
 " gument, but nothing new." This is, indeed, a 
 very easy way of disposing of it ; so easy, and so 
 brief, and withal so foreign to the purpose of that 
 section, that it might easily ha? e been written by 
 one who had never read or understood a syllable 
 of that section which you profess to hold so cheap; 
 and I shrewdly suspect this was your case when 
 you wrote and published your Essay. If you will 
 now take the trouble to read that section, you will 
 soon perceive that this suspicion is the least unfa- 
 vourable opinion that can be formed of your conduct, 
 in disregarding, or professing to disregard it, and 
 arguing boldly in defiance of what, if you understood 
 my 15th section, you must perceive to be the fun- 
 damental principles, not only of NEWTON'S rea- 
 sonings in his Principia, but of all reasonings by 
 necessary consequences, from any supposition, true 
 or false, that may be assumed, with a view either 
 
409 
 
 to a direct or an indirect demonstration. To 
 
 some of these violations of the established rules 
 and common practice of good reasoning, which 
 occur in your Essay, I have already called your at- 
 tention; and I shall soon have occasion to call your 
 attention to some other violations of the same kind. 
 With respect to the arrogance which you have 
 so confidently laid to my charge, I can conceive 
 nothing more groundless, or more unjust, than 
 such an accusation; nor can I conceive any excuse, 
 or pretence, that you can have for imputing arro- 
 gance to me ; for the whole tenor of my conduct,' 
 with respect to the publication of my Essay, appears 
 to me complete proof of the very opposite sentiments 
 on my part : I mean of the most extraordinary, 
 perhaps unexampled, caution, and diffidence, and 
 deference to the superior judgment and knowlege 
 of others. 
 
 If I had published my argument as a complete 
 logical and mathematical demonstration, hastily, 
 or even on the force of my own single unassisted 
 judgment, however long I might have considered 
 it by myself, you would have had some reason to 
 charge me with arrogance. If I had published it, 
 after submitting it to the revision of a very few 
 persons, whose sentiments were the same with 
 mine, and who of course approved of what I had 
 written, you would have had at least some excuse 
 for charging me with arrogance. If I had published 
 
410 
 
 it after submitting it to the revision of every person? 
 of my acquaintance who thought as I did with 
 respect to the subject of controversy, and who un- 
 animously agreed in thinking my demonstration 
 valid, but had taken care not to let any person 
 see it who held a different opinion with respect to 
 the subject of dispute, and, particular^ had 
 taken care not to show it to the person, or per- 
 sons, to whom it most immediately related ; you 
 would have had some pretence for charging me, if 
 not with personal, at least with a kind of party 
 arrogance. But when I acted, as you know I did, 
 in a manner directly opposite in all these respects; 
 when I submitted my Essay to the revision, not 
 only of every person of my acquaintance whose 
 opinion of the point in dispute coincided with 
 mine, but, moreover, submitted it to the revision 
 of every person of my acquaintance who held the 
 opposite opinion, with the most explicit assurance 
 to them all, that, if they could point out any error 
 in it, I should most thankfully acknowlege their 
 superiority in reasoning, and should commit my 
 work to the flames; when, in particular, I sent 
 my Work to Dr. PRIESTLEY, and gave him ample 
 time (between two and three years) to consider it; 
 and not only invited, but strongly urged him, and 
 his friend Mr. COOPER, to whom he chose to 
 entrust the charge of reading and considering it, 
 to give me their remarks on it, with the same as- 
 
411 
 
 surance that I had given to every other person to 
 whose revision I submitted it ; when Dr. PRIEST- 
 LEY himself, on first receiving my Essay, acknow- 
 leged that the letter which accompanied it, and 
 contained the offer which I have often mentioned, 
 did me the greatest honour ; and when, on receiv- 
 ing my second letter, two years afterwards, in 
 which I reminded him Of what had passed before, 
 and urged him to give me his observations on my 
 Essay, Dr. PRIESTLEY advised me to publish my 
 book without any farther delay ; and acknow- 
 leged that my attention to him and his brethren 
 
 had been greater than they were entitled to ; 1 
 
 conceive, without arrogance, that I did not only 
 all that / ought to have done, but all that I could 
 do, or conceive, in point of caution, and distrust 
 of my own reasoning, and in deference to the 
 judgment of others, especially of those whose 
 doctrine I undertook to refute. You must at least 
 acknowlege that I did infinitely more than you 
 have done in that respect ; and, I shrewdly sus- 
 pect, more than you ever heard of any other person 
 doing. If you think otherwise, I beg you will tell 
 me what more you think I ought to have done, or 
 could have done. 
 
 I shall be happy to profit by your instructions, 
 on any future similar occasion. 
 
REPLY 
 
 TO LETTER VI. 
 
 JVI \ r answer to your Essay is introduced witf* 
 observing, that your work exhibits extreme vanity, 
 arrogance, and ostentation. This description of 
 its character, I own, may seem harsh and severe ; 
 but it was not hastily affirmed : nor has the re-ex- 
 amination of your Essay served to weaken, but on 
 the contrary, to strengthen the opinion, which my 
 answer expressed. Whether my judgment of your 
 work be, or be not warranted by facts whether 
 I have misrepresented your manner, or correctly 
 described it, must be submitted to the decision of 
 those readers, who shall, or may, have candidly 
 perused it. In your later productions, it is obvious 
 to remark, are betrayed the same vanity, the same 
 insolence of temper, the same rude and contume- 
 lious spirit. We find likewise the same charges of 
 falsehood, and misrepresentation, alleged against 
 your opponents. As a controvertist you seem to 
 be peculiarly unfortunate. All your adversaries, 
 it would appear, are either so deficient in discern- 
 ment, as not to comprehend you, or so disingenuous, 
 
413 
 
 as to misrepresent your meaning. Complaints, 
 thus frequently repeated, are not only heard with 
 indifference, but they create a suspicion, that the 
 fault is imputable to you, and not to your oppo- 
 nents. 
 
 In reply to my charge, you deliver it as your 
 opinion, that your conduct, in respect to the 
 publication of your Essay, is " a complete proof 
 " of the most extraordinary, perhaps, unexampled 
 " candour, and diffidence, and deference to the 
 " superior judgment, and knowlege of others." 
 After remarking, that this observation furnishes 
 no refutation of my charge, which refers to the 
 sentiments, and manner of your Essay, I would 
 take the liberty to enquire, what evidence you can 
 produce of this unexampled deference to the judg- 
 ment of others, unless the mere act of submitting 
 your argument to their examination can be regard- 
 ed as such? It is true, you consulted several 
 mathematicians, and metaphysicians also, re- 
 specting the validity of your demonstration ; but 
 such consultations, with such a result, afford no 
 decisive evidence, of a diffident, or submissive 
 spirit. They remind me of an anecdote, related 
 to me by the. friend of a late respectable clergyman, 
 in the North of Scotland. This reverend gentle- 
 man was occasionally consulted by the young 
 women of his parish, concerning the propriety of 
 their choice, when they were about to enter into 
 
414 
 
 the matrimonial state. The good old clergyman 
 knew full well, that they had made up their minds 
 (to use the fashionable phrase) before they came 
 to ask his counsel, and he treated them accord- 
 ingly. " Sir," said a young woman to him, " I have 
 " made free to call upon you, and ask your advice." 
 " Very well, Margaret," said the reverend gen- 
 tleman, " you shall certainly have my best advice ; 
 " but what is the subject, on which you wish to 
 " consult me?" " I want to know, Sir," said she, 
 " whether you would advise me to marry Johnnie 
 " Gordon ; if you have any objections, I should 
 " like to hear them." " None at all, Margaret, 
 " if you yourself are pleased with him." " But, 
 " Sir, they say, he drinks." " Then, don't marry 
 " him." " Aye, Sir, but they tell me, that he is 
 " very kind to his poor old mother, and supports 
 " her." " Then, Margaret, marry him." " But, 
 " Sir, I am told that he is ill tempered." " Then, 
 " don't marry him." " Very right, Sir; but every 
 " body says, that he is an honest, hard-working 
 " man, and a good servant." " Then, I advise 
 " you to marry him." '< But ah, Sir- Shall I tell 
 " you? They say he has a bastard child in an- 
 " other parish." " Then, pray, Margaret, by no 
 " means marry him." " But, Sir, I dinna believe 
 " it: some say, its nae true." " Why don't you 
 " ask himself!" said the reverend gentleman. " I 
 " dinna like to do that, Sir ; for, if it were true, I 
 
415 
 
 " fear, I would marry him, after a' He wudna, 
 " may be, mak' the war husband" " That's a 
 "point," said the reverend gentleman, " on which 
 " I would not venture to give any opinion." Thus 
 ended the conference ; and the marriage, after 
 this, as after all other similar conferences, took 
 place. 
 
 I doubt not, but you consider these consulta- 
 tions, as a clear evidence of the modesty and dif- 
 fidence of the young ladies, as also, of the great 
 deference they paid to the opinion of their spiritual 
 pastor. The reverend gentleman knew better ; he 
 was well aware, that their resolutions were fixed, 
 before they came to consult him. I do not there- 
 fore regard the mere act of submitting your argu- 
 ment to the examination of some mathematical, or 
 metaphysical friends, as a decisive evidence of 
 modesty and diffidence ; nor can I consider your 
 adherence to your own opinion, as a proof of 
 deference to their judgment. I do not, however, 
 mean to affirm, that you were bound to yield your 
 own conviction to the objections of those, who 
 questioned the validity of your demonstration: 
 but I repeat, what I have now remarked, that to 
 coasult another, and not defer to his opinion, 
 is no proof of diffidence. All the Necessarians, 
 to whom you submitted your demonstration, pro- 
 nounced it to be fallacious ; or at least refused their 
 assent to it ; men, it would appear from your own 
 
416 
 
 report, " of acknowleged talents, and liberal educa- 
 " tion, well accustomed to scientiiic researches, 
 " and of whose acuteness in reasoning* you had the 
 " highest opinion. One of these, you inform us, 
 " was a person of superior talents, and great eru- 
 " dition, and extensive general knowlege, peculi- 
 " arly well versed in metaphysical researches, and 
 " capable of, and much used to, close and accu- 
 " rate reasoning." Now, Sir, the young maids 
 seem to have shewn the same Reference to their 
 ghostly father, as you displayed towards those 
 Mathematicians, and Metaphysicians, whom your 
 " most extraordinary, perhaps unexampled can- 
 " dour and diffidence prompted you to consult." 
 And yet you well know, and acknowlege, that 
 a Mathematical demonstration compels assent. 
 
 It was remarked in my Essay, that you had 
 assailed the doctrine of Necessity in a manner, 
 somewhat new. You seem highly indignant, that 
 I should have expressed myself in this qualified 
 manner, respecting the novelty of your mode of 
 attack, and refer me to Doctors Reid and Camp- 
 bell, to whom, you inform me, that your manner 
 of reasoning was entirely new Dr. Campbell, 
 however, did not acknowlege the validity of your 
 argument. Now, Sir, I will frankly own, that I 
 am here, perhaps, chargeable with injustice to- 
 wards you in speaking of your Essay, as a novel 
 production, in terms too qualified. In regard to 
 
417 
 
 its tone, arid manner, I must confess, that I be- 
 lieve them to be purely your own, and that, in 
 this respect, the production is not partly, but 
 wholly, new. I must confess also that I believe 
 your mode of reasoning to be novel and extraordi- 
 nary, and that it is likely to remain a perfect unique 
 in the history of metaphysical science. But, when 
 I qualified the expression, I alluded to your appli- 
 cation of Mathesis to a question in Metaphysics ; 
 and it did occur to me, that, notwithstanding 
 your merit in this respect, you were not the only 
 philosopher, (absit invidia,) who could boast the 
 high desert of evolving the most recondite myste- 
 ries, ascertaining the most sublime truths, and 
 atchieving the most difficult operations, by the aid 
 of Mathematical science. You must recollect, that 
 the tailor of Laputa, when measuring Gulliver 
 for a suit of clothes, took the gentleman's altitude 
 by the help of a quadrant; and that the inhabitants 
 of the island, being all great Mathematicians, 
 when they praised the beauty of a lady, described 
 it, by rhombs, circles, parallelograms, ellipses, and 
 other geometrical figures. You will recollect also, 
 that a Mathematician of great celebrity, applied 
 Mathematics to a great variety of important, and 
 sublime investigations. We are told of the re- 
 nowned knight, Sir Hudibras, that 
 
 " In Mathematics he was greater 
 " Than Tycho Brahe, or Erra Pater ; 
 Let. 2 D 
 
418 
 
 " For he, by geometric scale, 
 
 " Could take the size of pots of ale, 
 
 " Resolve by sines, and tangents straight, 
 
 " If bread or butter wanted weight, 
 
 " And wisely tell, what hour o' th' day, 
 
 " The clock does strike, by Algebra." 
 
 Now, though I mean not to affirm, that you 
 have attained the same high eminence with this 
 gentleman, HI the application of Algebraic analysis, 
 yet I might possibly do you injustice, were I to 
 deny, that if you proceed, as you have begun, you 
 may perhaps arrive at an equal degree of celebrity. 
 I must further confess, that, in my humble appre- 
 hension, not only is the argument indisputably 
 new that no philosopher, or mathematician, ever 
 conceived it before, but likewise, that you have 
 handled it with an adroitness of skill, an urbanity 
 of manner, an elegance of conception, a liberality 
 of sentiment, and a conciseness of diction, peculi- 
 arly your own. If any philosopher, or mathema- 
 tician, possessed powers equal to the excogitation 
 of such an argument, beside Dr. Gregory, no man, 
 I am persuaded, could have unfolded it so briefly, 
 or employed it against his opponents with such 
 singular success. If any of the students, at the 
 academy of Lagado, had, agreeably to the prac- 
 tice of Mathematicians there, swallowed, on a 
 fasting stomach, the demonstration in question, 
 fairly written on a thin wafer, with ink composed 
 of cephalic tincture, I am confident, that no man 
 
419 
 
 unless a person, to whom " physic is his 
 "trade, and metaphysics his amusement," could 
 anticipate the wonderful effects, which it might 
 have produced, as the wafer digested, and the 
 tincture mounted to the brain. 
 
 You complain that I dismissed your 15th Sec- 
 tion without remark; and you " shrewdly suspect," 
 that I did not take the trouble to read it. Here 
 you do me injustice. I certainly did read it, and 
 have read it now a second time ; but I will not 
 undertake, unless you should particularly request 
 it, to read it a third time. It contains, as is stated 
 in my Essay, a general illustration of yotir mode 
 of reasoning, but nothing new, as far as the argu- 
 ment is concerned. Your analysis of Newton's 
 corollary, and your disquisition about the mean- 
 ing of the words corpus and vires, in that corol- 
 lary, might have been spared with some advantage 
 to the reader, and no injury to your demonstra- 
 tion. Your application of the corollary to the 
 subject in question, presents us with nothing, but 
 a repetition of the same fallacy, which pervades 
 your whole argument. Every candid and intel- 
 ligent reader, who will take the trouble to peruse 
 your 15th Section, and is acquainted with your 
 " peculiar mode of reasoning," will acknowlege 
 the justness of this statement. With these obser- 
 vations I dismiss vour 6th Letter. 
 
120 
 
 Your 7th Letter is not yet finished. To that 
 part, which you transmitted to me in print, you 
 have my reply in manuscript. This reply I shall 
 suppress for the present; judging it better to 
 wait, till your 7th Letter is completed, and till I 
 shall have an opportunity of examining the whole 
 of your future animadversions ; if they should ever 
 be presented to the public, or to my private peru- 
 sal. In the mean time, the state of the contro- 
 versy between us, will be sufficiently illustrated by 
 the preceding Letters. You assure me, that you 
 are hearty in the cause, and are desirous to pro- 
 ceed with as great celerity, as your professional 
 engagements will permit. Having waited how- 
 ever fourteen years for the completion of that 
 Answer, which in the year 1804 was by your own 
 account nearly ready for the press, and part of 
 which has been in print almost fifteen years, I trust 
 I shall not be accused of impatience, when I 
 required, that, agreeably to your promise, you 
 would either publish your Letters, or retract your 
 opinion. 
 
 A few cursory remarks on that part of your 7th 
 Letter, which I have received, shall conclude my 
 Reply. 
 
 I have said, that a body cannot move in any 
 direction, without an impulse in that direction. 
 This I have been taught to consider as an admitted 
 
421 
 
 truth. Nothing more forcibly evinces a conscious- 
 ness of the weakness of your cause, than your avi- 
 dity to seize on any observation, how unimportant 
 soever, which can furnish you with an occasion to 
 carp or cavil. And it unfortunately happens, that, 
 indulging this propensity, you sometimes expose, 
 not the ignorance or inadvertence of your adver- 
 sary, but either your own unacquaintance with the 
 subject, or a captious querulous spirit. The pro- 
 position, which I advanced, has been, I believe, 
 universally admitted : nor did I expect that 
 any cavil could be raised against it. Newton, in 
 his second Law of Motion, says, that the altera- 
 tion of motion is ever proportioned to the motive 
 force, and is made in the direction of the right line, 
 in which that force is impressed. The truth, how- 
 ever, of my proposition you dispute, and tell me, 
 that a body moving in a curve is a proof of its fal- 
 sity. The justness and pertinency of this objection 
 I submit to the judgment of every philosophical 
 reader. Acquainted, as you profess to be with 
 the Principia of Newton, you surely must know, 
 that two impulses, combined into one, are univer- 
 sally considered as one motive impulse. In New- 
 ton's second corollary to the third Law of Motion, 
 he calls the composition of one, out of two oblique 
 forces, one direct force. 
 
 But, if your observation were correct and well 
 

 422 
 
 founded, my argument remains untouched until 
 
 you have shewn, that 
 a body impelled in the 
 direction A D, may 
 describe the diagonal 
 AR 
 
 D 
 
 B 
 
 C 
 
 I have said, that for every action there must be 
 a motive. I consider this as a self-evident truth ; 
 nor can popular phraseologies, how common soever, 
 be received as proofs of the contrary position. 
 This you affirm is to you " no truth at all." It 
 must be granted, I conceive, that every volition 
 implies a change, and that no change, whether in 
 matter, or in mind, can take place without a 
 cause. The agent cannot be the cause of his own 
 volition : this surely will not be affirmed. Nay, 
 if he could, the fact could furnish no satisfactory 
 explanation of the point in question. Why did he 
 change his state of mind? Why did he form a 
 new volition ? A motive, a cause, is still wanted, 
 unless we resort to a senseless identical proposition, 
 and say ; He willed a change, because he willed 
 a change. This, surely, is not a very philosophi- 
 cal answer, nor would it satisfy any person, who 
 should desire to know, why another had acted in 
 
423 
 
 this, or in that manner. I hold it therefore to be 
 an incontrovertible truth, that for every volition, 
 and therefore, for every action, there must be a 
 motive. The contrary doctrine would imply, that 
 there may be a change produced in our state of 
 mind, without any cause for that change, which is 
 equivalent to affirming an effect without a cause. 
 
 When you attempt to ridicule the expression 
 " a metaphysical universality" you betray an ig- 
 norance of a distinction, familiar to every noviciate 
 in the Dialectic Art; a distinction, which one 
 would conceive it impossible for any person to 
 overlook, who has devoted the slightest attention 
 to the philosophy of the human mind or the prin- 
 ciples of just reasoning. A metaphysical, a physical, 
 and a moral universality, are the distinctive and 
 acknowleged characters of what are denominated 
 universal propositions, as more, or less, compre- 
 hensive, which no man, who thinks correctly, 
 can possibly confound. The pertinency of your 
 multiplied queries, and endless illustrations, on 
 the subject of physical forces, I forbear at present 
 to notice ; nor is it my intention now to follow 
 you, while you ramble through numberless cases 
 of physical forces, centripetal forces, curvilinear 
 motion, friction, and I know not what beside. 
 Their profundity and importance however, as well 
 as their connection with the main question, may 
 be estimated from the proposition, which they are 
 
424 
 
 designed to illustrate, namely, that curvilinear 
 motion " takes place in a line, to which the body 
 " moving neither has nor can have any impulse ; 
 " and for moving in which, as far as our knowlege 
 " of nature enables us to judge, there cannot be 
 " any one physical cause." Newton, it is appre- 
 hended, was aware of this ; and yet he considered 
 the composition of two forces, or two impulses, 
 as only one force, or one impulse. But this dis- 
 tinguished philosopher, it would seem, did not 
 understand the subject; he had not learned to 
 apply Mathematics to Metaphysical science. 
 
 You promise to offer a few remarks, and a few 
 questions, on the distinction between essential, 
 material, efficient and Jinal causes. There is no 
 pertinent query, that you can propose, which I 
 wish to evade; no relevant observation, which 
 shall not receive from me all the attention, which it 
 may appear to deserve. I shall merely remark at 
 present, that, whether we consider every agent, 
 physical and intellectual, which contributes to the 
 effect, as a distinct cause, or, with greater pro- 
 priety, regard all the concurring circumstances, 
 or agents, as constituting the cause, is of little 
 moment; for in either case, while every single part 
 of the cause can produce only one and the same 
 part of the effect, or all collectively produce no 
 other, than one and the same whole effect, the 
 doctrine of Necessity remains unshaken. If it 
 
425 
 
 can be shewn, that any agent, any antecedent 
 circumstance, physical or moral, could have pro- 
 duced, cceferis paribus, any other, than that effect, 
 or that part of the effect, which it did produce, 
 the hypothesis of Necessity falls to the ground. 
 
 Necessarians believe, that the agency of moral, 
 as well as of physical causes, is regular and uniform. 
 They believe, that the changes in the intellectual 
 world are under the government of fixt, and defi- 
 nite laws, as much as the phenomena of physical 
 nature. They believe, that this regularity and 
 uniformity in the operation of intellectual and 
 moral causes, is essential to the order and harmony 
 of that system, to which we belong. Let the 
 connection between moral causes and their effects 
 be dissolved, and disorder and perplexity would 
 universally prevail. But we believe that every 
 appetite, every passion, every sentiment, and every 
 feeling, has one definite and uniform agency. 
 We believe, that they are all, equally with the 
 physical agents of nature, not partly but wholly, 
 not occasionally but constantly, under the direction 
 and control of the great Governor of the universe. 
 We believe, that He, by whose command circle 
 thousands and thousands of surrounding worlds, 
 foreordains on this diurnal sphere also, whatso- 
 ever comes to pass. In him all causes centre ; 
 He is the supreme arbiter of all events. Under 
 his government we are placed ; and by the counsels 
 Lot. 2 E 
 
426 
 
 of his wisdom all things are ordained. Whether 4 
 the wreck of a world, or the fall of a sparrow, it 
 is the appointment of Him, who is the Architect 
 of the universe, and who regulates every move- 
 ment of the vast machine. Weak and short-sighted 
 mortals may fix their attention on second causes, 
 and forget that the Omnipotent ruleth over all. 
 In every passing event, trivial or momentous, they 
 may perceive no other agency than the will of 
 man: or, if they acknowlege the direction and 
 superintendence of a superior power, it is only to 
 ascribe to it oqcasional interpositions in human 
 concerns. Chance and contingency may furnish 
 themes of specious declamation; in relation to our 
 limited faculties, their existence is admitted : but 
 we may rest assured, that under the government 
 of an omniscient and presiding power, contingency 
 and chance can have absolutely no place, and that 
 every circumstance the most minute, is ordained by 
 unerring wisdom, combined with unchangeable 
 goodness. Dark, indeed, and inscrutable to us 
 are the ordinations of the Supreme Cause. Evils, 
 moral and physical, cloud the present scene. 
 Why these were either ordained, or why they are 
 permitted to exist, it is denied to us fully to under- 
 stand. But vain man would be wise. He, whose 
 habitation is but an atom in the immensity of space, 
 who sees little, and knows still less, dares to arraign, 
 what his short-sighted reason does not approve, 
 
427 
 
 erecting his own limited conception into a standard 
 of physical possibility, and dogmatising, as if his 
 narrow intellect could span the infinitude of crea- 
 tion, or as if he were certain, that he ranks in the 
 highest order of possible intelligences. If it be 
 true, that we must and can reason, only from 
 what we know, it is equally true, that reason 
 teaches us, that we know but little, and that little 
 imperfectly. Dark, however, and mysterious as 
 are the ways of Providence, let us humbly hope, 
 that under the government of a good and wise 
 being, suffering will not be perpetuated, and that 
 all evils, present and future, will ultimately issue 
 in a state of pure, substantial, and never-ending 
 happiness. 
 
 I am, Sir, yours, &c. 
 ALEX. CROMBIE. 
 
Published by the Author of the Replies, and sold by 
 R. Hunter, No. 72. St. Paul's Church Yard ; 
 
 1. An Essay on Philosophical Necessity. In one large Volume 
 8vo. Price 7s. in boards. 
 
 2. A Treatise on the Etymology and Syntax of the English 
 Language. Svo. Second Edition. 
 
 3. GYMNASIUM sive SYMBOLA CRITICA, intended to 
 facilitate the Attainment of a correct Latin Prose Style. 
 2 Vols. Svo. 
 
 4. Letters on the Present State of the Agricultural Interest. 
 
 5. A Reply to the Strictures of the Rev. Mr. Gilchrist, on 
 a Treatise on English Etymology and Syntax. i 
 
 6. A Letter to D. Ricardo, Esq. 'containing an Analysis of 
 his Pamphlet, on the Depreciation of Bank Notes. 
 
RETURN CIRCULATION DEPARTMENT 
 
 TO *> 202 Main Library 
 
 LOAN PERIOD 1 
 HOME USE 
 
 r 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 ALL BOOKS MAY BE RECALLED AFTER 7 DAYS 
 
 1 -month loans may be renewed by calling 642-3405 
 
 6-month loans may be recharged by bringing books to Circulation Desk 
 
 Renewals and recharges may be made 4 days pno'r to due date 
 
 DUE AS STAMPED BELOW 
 
 ... , --.- j_ -.. 
 
 \ ' - 
 
 
 (' ' <" "' 
 
 
 
 Ubl L) 
 
 ,;;;j 
 
 
 UNIV. OF CAl 
 
 JR, BERK. 
 
 
 
 
 
 RKbfMfilife Mfm f *^ 
 mA A AAAfl 
 
 jBa 
 
 
 1 t 2000 
 
 
 
 U. C. BERKELEY 
 
 
 
 
 
 
 
 
 
 
 
 
 FORM NO. DD6 60m 
 
 UNIVERSITY OF CALIFORNIA, BERKELEY 
 1 778 BERKELEY, CA 94720 
 
>