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Tie natural Ttoloiy of a Doctrine of tie Forces. 
 
 By Prop. BENJ. N. MARTIN, D. D., L. H. D., 
 
 University of the City of New York. 
 
 fuom the plloceedings ob" the university convocation held at albany, n. y 
 August 1st, 2d and 3d, 1871. 
 
THR 
 
 .No 
 
 Division 
 
 Range 
 
 Shelf 
 
 Received 187 
 
Natural Theology of the Doctrine of the Forces. 701 
 
 t 
 
 \. Of c 
 THE NATURAL THEOLOGY OF THE DOCTRlte 0£ J fli] 
 
 By Prof. Benjamin K Martin, D. D., L. H. D., 
 
 University of the City of New York. 
 
 The great change which has passed over the philosophy of physics 
 in our day, re]ates to the doctrine of the forces; and scientific teach- 
 ing now affirms the correlation, or convertibility, of them. all. 
 
 The idea of force, which lies at the basis of this view, is yet far from 
 being clearly defined in the conception of the physical philosopher. 
 It is vaguely conceived as something lying back of phenomena, to 
 which the latter are to be referred as their ground or cause. All 
 the varied phenomena oij the physical world, and, indeed, of the 
 physical universe, are attributed, not as recently they were, to 
 imponderable fluids or agents, but to motions of the masses, or ihe 
 particles, of matter ; motions which are themselves due to the action 
 of certain impelling forces. The chief interest which attaches Lo 
 the subject arises from the apparently successful attempts that have 
 been made to convert one of these forces into another, and thus to 
 arrive at a generalization which will admit of our grouping them 
 together, as forms or manifestations of a single force. 
 
 The great physical agencies of our world, light, heat, electricity, 
 and the chemical force (known now as chemism), are so unlike in 
 their ordinary aspects, that, during all the earlier stages of our 
 inductive progress, not only was their nature unknown, but their 
 unity, their common character, was unsuspected. Light was regarded 
 as a peculiar emanation from a certain class of bodies called lumi- 
 nous ; heat was a kind of fluid filling the pores of bodies, and capa- 
 ble of being squeezed out of them by compression, as water from a 
 sponge ; of electricity, it was long disputed whether it consisted of 
 one fluid, manifesting its presence by excess and defect, or of two 
 fluids of opposite character, which give respectively the vitreous and 
 the resinous electricities ; magnetism was conceived to be due to a 
 fluid acting from one pole of a magnet to another, in curved lines ; 
 galvanism was deemed to be a fluid closely related to the nervous fluid 
 of the human system ; and in addition to all these we had the force of 
 
 239 
 
702 University Convocation. 
 
 chemical affinity, governing, in a manner that was deemed entirely 
 peculiar, the chemical reactions. It was long before any common 
 ground in all these apparently diverse agencies was even suspected ; 
 but within a recent period a change has passed over these modes of 
 conceiving of the imponderable agents of our general chemistry. 
 
 It began to be understood that light was not a distinct substance 
 sent forth in radiating lines, but a vibration or regulated motion, in a 
 universally diffused medium of the rarest kind, a motion analogous to 
 that vibration of the air which reports itself to the ear as sound. By 
 this discovery, one of the great supports was stricken from an 
 erroneous mode of conceiving. 
 
 Early in the present century, however, the mutual relations of 
 some of these agencies began to be more clearly perceived. Galvani's 
 original discovery, made in 1790, that a movement can be excited 
 in the limbs of an animal by the application of two metals to the 
 nerve and the muscle, was made in connection with the conductor of 
 an electrical machine; and was originally announced as a kind of 
 animal electricity ; and this connection, iC at first rather conjectured 
 than proved, succeeding researches confirmed."* Ten years after, in 
 1800, Yolta contrived — by means of the instrument which was 
 named, from its inventor, the voltaic pile — to accumulate this force 
 so as to bring it much more fully within the sphere of observation. 
 The general attention of observers was thus fixed upon the very 
 interesting phenomena of voltaic electricity, and many wonderful 
 properties and beautiful laws were brought to light. The discovery 
 in 1820, by Oersted, of Copenhagen, that the conducting wire of a 
 voltaic circuit affects the magnetic needle, brought prominently for- 
 ward the idea of the connection of these forces; and the term electro- 
 magnetic marks the step which identified the two as really forms of 
 one, so that electricity, magnetism, and galvanism, became insepara- 
 bly connected in scientific thought as manifestations of a single 
 agency. 
 
 Contemporaneous with this, was the brilliant epoch of Davy and 
 Faraday. It had been found that under the influence of the voltaic 
 circuit certain compound substances are decomposed. Water, for 
 instance, was resolved into its elementary gases ; and some metallic 
 salts suffered a like resolution into their constituent elements. Davy 
 felt assured that not only these, but the whole body of the voltaic 
 phenomena, are chemical in their nature; and in 1806 he uttered 
 
 * Wheneirs Hist, of the Inductive Sciences. 
 
 240 
 

 Natural Theology of the Doctrine of the Forces. 703 
 
 his thought, more as a conjecture than a discovery, " that chemical 
 and electrical attractions were produced by the same cause, acting 
 in the one case on particles, and in the other on masses."* 
 
 This anticipation of Davy's was taken up by his successor, 
 Faraday, who proved that the electric current in a voltaic pile is 
 due to " the mutual chemical action of its elements." He intro- 
 duced a distinctness of conception, and an accuracy of expression, 
 which contributed greatly to the elucidation of the subject. He 
 showed that the wire of a voltaic circuit " conducts chemical 
 affinity," and that "electricity is only another mode of the exertion 
 of chemical forces."f By his researches, principally, the identity of 
 chemism with the various forms of electricity, was established ; and 
 we have, as the great result of Faraday's labors, the science of 
 electro-chemistry. 
 
 Meanwhile, in other departments, a similar progress was going 
 on. Not only was the theory of light reduced to the simple con- 
 ception of the regular and rapid movement of particles of a rare 
 medium, but the conception of heat underwent an analogous change. 
 It was found that the conception of a physical substance termed 
 caloric, which had served, during all the last century, to explain and 
 classify many of the phenomena r afforded only an imperfect and 
 unsatisfactory account of them ; and the attention of observers was 
 directed to the subject in the hope of gaining some clearer ideas. 
 Among the earliest of these investigators was our distinguished 
 countryman, Count Rumford. A paper read by him before the 
 Royal Society, in 1798, gave account of a very remarkable and 
 happy experiment, which elucidated the nature of heat, so far as to 
 show that it could not be a distinct substance. He had been struck 
 by the very great amount of heat generated by the mechanical 
 process of boring cannon ; and that process gave him the idea for 
 his experiment. He took a thick metallic cylinder, and immersing 
 it in water at a temperature of 60°, applied to it a metallic plunger, 
 which was firmly pressed against the end of it, while the cylinder 
 itself was steadily turned by horse-power. At the end of an hour, 
 the temperature of the water had risen to 107° ; in thirty minutes 
 more it reached 140° ; at the end of two hours the mercury stood 
 at 178° ; at two hours and twenty minutes it was 200°; and at two 
 hours and thirty minutes the water, which amounted to two and a 
 half gallons, actually boiled. " It would be difficult," he says, " to 
 
 *Whenell's Hist, of the Inductive Sciences. fib. 
 
 241 
 
704 University Convocation. 
 
 describe the surprise and astonishment expressed in the countenances 
 of the bystanders on seeing so large a quantity of water heated, and 
 actually made to boil, without any fire."* 
 
 This experiment ought to have been decisive against the theory 
 of the material nature of heat, but, for a long time, it failed to 
 attract the attention which it deserved ; and only recently, by the 
 confirmatory experiments of Joule, in England, did it reach the 
 rank to which it was entitled. It shows us that heat — a thing 
 which can be supplied inexhaustibly by the simple friction of a 
 borer — is not any material substance, however attenuated, but must 
 be conceived as a peculiar mechanical condition of the particles of 
 matter. This general view I need not dwell upon. It has been 
 illustrated with so much ability and interest by Tyndall, in his 
 Lectures on Heat, that it suffices to refer to his book for the complete 
 elucidation of the subject. Heat is now understood to be a rapid 
 motion of the particles of any substance — of what nature we do 
 not yet accurately know — but this, unquestionably. In heating a 
 substance, we do but put its particles into a state of rapid, perhaps 
 vibratory, motion ; an elevation of temperature means an increase 
 of this movement, either in rapidity or in extent, or in both ; and a 
 lowering of temperature means a. diminution of the amount of this 
 motion. 
 
 Now this internal motion of the particles of any body, is found 
 to sustain a relation to the mechanical motion of the mass as a 
 whole ; and the one of these motions is convertible into the other. 
 When a ball is dropped from a height upon a solid body, and its 
 motion suddenly arrested, the ball becomes heated ; that is, the 
 mechanical motion of the mass, its transfer by a molar force from 
 place to place, is changed into a motion of the particles among them- 
 selves. These are thrown into rapid vibration, we will call it, for 
 want of a more accurate name ; that is, the temperature of the body- 
 is raised. If we hammer a piece of iron, it becomes hot ; the arrested 
 mechanical motion of the hammer, becomes transformed into a rapid 
 agitation of the molecules of the mass which arrests it. 
 
 Heat sustains, moreover, a relation to light. That they are 
 closely connected, our commonest experience teaches us all ; but how 
 closely, the world has only in late years learned. Light, too, is but a 
 vibration as it comes to us through the transparent ether which, as a 
 medium, connects our world with the stars ; and hence it is easy to 
 
 * Tyndall ; Lectures on Heat. 
 
 242 
 
JVa tura l Theol ogt of the D o ctrine o f the For ces. 7 05 
 
 conceive them as analogous states of matter. The vibrations of 
 heat have only to be sufficiently increased, and the heated body begins 
 to report itself to our eyes as a luminous one. The lower tempera- 
 tures are dull and faint in their gleam, but as the temperature rises, 
 that is, as the rapidity of the motion increases, the light grows more 
 intense, till the agitated and quivering mass glows with the white 
 light which represents the intensest heat, and almost forbids our 
 direct vision. 
 
 Light also stands in similar relations to mechanical force. The 
 sudden arresting of a mass in rapid motion, produces not only heat 
 but light. Tyndall states that the impact of one of the solid projec- 
 tiles of the great Armstrong guns, upon a target at Shoeburyness, 
 sometimes produced not only heat, but a flash of light so distinct as 
 to be visible by broad daylight. 
 
 JSTow these two great classes of agencies to which I have referred, 
 the electro-chemical force on the one hand, and that of light, heat 
 and mechanical force on the other, were next drawn into mutual 
 relation. It was found that not only would the voltaic pile develop 
 heat, as in many arrangements it does to a very high degree, but that 
 certain applications of heat would also develop the phenomena of 
 electricity ; and soon the thermo-electric pile was devised as by far 
 the most sensitive instrument for the measurement of heat. Thermo- 
 electricity has now become a very important branch of physics ; and 
 we have in this name another indication of the general progress of 
 the identification of all these varied agencies. 
 
 The exact mechanical equivalent of heat has been determined after 
 a vast amount of careful experiment and measurement, by Joule in 
 England, and by Mayer in Germany ; so that it now seems possible 
 to calculate, on the one hand, the amount of heat which would be 
 produced by the arrested motion of any moving mass, and on the 
 other the amount of matter which could, be put in motion by the 
 extinction of a given amount of heat. The amount of force required 
 to raise a weight of one pound through a height of one foot, called 
 the foot-pound, is the unit. 
 
 Thus all these different forces are found to be but varied manifesta- 
 tions of the same great agency. They are different kinds of motion, 
 produced by a force which is not many and diverse, but one and 
 simple. The varying phenomena are identified with one another 
 through their common relation to the general fact of motion, of the 
 specific kinds of which we have yet much to learn. What is the 
 
 243 
 
706 University Convocation, 
 
 particular kind of motion which constitutes heat, and how it differs 
 from that of light, and how from that of electricity, we do not know, 
 nay, are perhaps far from knowing ; but we seem pretty well assured 
 that these different kinds of movement all sustain a common relation 
 to the mechanical motion of a mass, and are substantially convertible 
 into one another ; and this is what is now meant by the converti- 
 bility, or the correlation, of the forces ; they are all interchangeable 
 forms of a single force. 
 
 I pause a moment in view of a generalization so interesting, and 
 so comprehensive. For the co-ordination of a vast number of remote 
 and apparently unrelated facts, no other generalization which sci- 
 ence has reached since the great discovery of Newton, seems to me 
 so remarkable. The varied phenomena of nature bad been already 
 grouped into distinct classes, and arranged with all the method of a 
 scientific order; the generalization which embraces them all, is, 
 therefore, the comprehension of a whole body — nay, of the whole 
 body of the physical sciences, under one most general principle. 
 The explanation which this generalization affords is equally happy. 
 The result is no simple registration of phenomena, according to that 
 superficial view of induction which theoretically denies to science 
 anything more than the office of mere observation. More true to 
 the high aims of the intellect itself than to the demands of that 
 insufficient theory of procedure which is honored under the name of 
 induction, the men of science have concurred with unwonted unan- 
 imity, first, in referring the phenomena observed, in each several 
 department, to the ground which alone can afford a satisfactory view 
 of them ; and then in embracing all these distinct branches of know- 
 ledge under what we may, with some reservations, call a universal 
 expression. The consequence is, the discovery of a law, on the one 
 hand, so comprehensive as to include the immense and varied body 
 of natural phenomena, and, on the other, so profound as to furnish 
 explanation of the whole vast mass. Each phenomenon is an intelligi- 
 ble result of some modified operation of the one great and universal 
 Force of Nature. 
 
 It is a point of great interest that, in this wide formula, science 
 seems to have reached the extreme limit of her inquiries. When 
 these specific forces have once been thus grouped and united, no 
 further advance in generality of expression is possible. The problem 
 has been reduced to its very simplest form of statement. These, 
 navigators on the great sea of the unknown, set out by different and 
 
 244 
 
 
Natural Theology of the Doctrine of the Forces. 707 
 
 even opposite courses ; but, sailing thus in contrary directions, they 
 •have at length come in view of each other ; their discoveries have 
 compassed the globe, and the whole orb of knowledge stands dis- 
 closed in all the simple harmony and unity of truth. 
 
 If there is something painful in the idea of having reached the 
 limit of research in so great a sphere of inquiry — in hearing, as it 
 were, the last word of science in regard to the great expansion of 
 her thought, we may, at least, feel that it enables us the better to 
 pursue the course of those reasonings upon which the noblest minds 
 have always been intent. If the problem is solved, we may the 
 more justly inquire for the bearing of the solution upon the great 
 theme of our present inquiry. 
 
 This brings us to the question, for the sake of which I have entered 
 into this account of the doctrine of force, as at present held. What 
 is to be the bearing of this great discovery upon the theistic view of 
 the universe ? What is to become of our conception of God, when 
 the phenomena of nature are all referred to general or universal 
 laws, and these are affirmed to be the manifestations of one compre- 
 hensive, controlling, and universal force, operating through the 
 unnumbered ages of past time ? Let us endeavor to trace the subject 
 to its issues. 
 
 Before, however, we can have much hope of gaining any idea of 
 the bearing of this discovery, we shall need to inform ourselves some- 
 what more particularly of the specific character of the force thus 
 indicated. Under what form of thought is it to be properly con- 
 ceived ; or, scientifically speaking, what is its law ? 
 
 Here it is first to be observed, that the general expression which 
 we have obtained is not absolutely universal. We identify several, 
 perhaps many, of the forms of force known to us, but we have 
 no reason from that fact to assume that we have thereby identified 
 them all. Each of the forces included in our generalization 
 has, as its marked characteristic, a definite relation to physical 
 motion ; we may find reason to conclude that there are other forces 
 which have no such relation. In that case we should be acting 
 wholly without our warrant, if we should insist upon stretching our 
 generalization so far as to include them. There is a group of force's 
 which together govern the motions of atoms in space. Physicists 
 have thus far recognized no others ; but I can hardly be wrong in 
 saying that the force by which an atom resists the compression 
 which would crush it out of exitence, is one of a wholly different order, 
 
 245 
 
708 University Convocation. 
 
 and has no relation whatever to motion, either molecular or mechani- 
 cal. Perhaps, too, other forces, relating not to the constitution of 
 matter, but to the operations of the mind, may be arrived at, which 
 equally refuse to come within the generalization. 
 
 In speaking, therefore, of the convertibility of forces, I beg that 
 it may be observed that I speak with a limitation, and refer only to 
 the motive forms of force — to those general and diffused agencies 
 which pervade the universe and give movement to the atoms which 
 compose it. 
 
 Of these forces, then, I may observe that, in the case of several 
 of them, science has ascertained the existence of a common law 
 which affords us a deeper insight than we gain by any other means, 
 into their interior nature. The great law which governs, and 
 expresses, the diffused operations of gravitation, has been already 
 determined to be that of the inverse square. Now, it is quite 
 remarkable that the same law has been proved to be the one which 
 governs the attractions of electricity, and also, on independent 
 grounds, of magnetism. We should have been at liberty to infer 
 as much from the common nature of these forces, but it so happens 
 that the proof of this community is less clear in the case of gravita- 
 tion than in that of some of the others. On the ground, however, 
 of this common law, we may feel emboldened to identify them all, 
 and to conceive their general action as altogether analogous -to the 
 well known operations of this familiar agent. 
 
 Let us suppose, then, the universal prevalence of such a force as 
 gravity is ascertained to be, viz., one that corresponds in intensity 
 to the mass of the * matter involved, and which varies inversely as 
 the square of the distance. That gravity exists under this law is, 
 perhaps, the best ascertained of all physical truths. It pervades the 
 universe through all its spaces, and it reaches and governs each 
 minute particle of matter. Now, we shall find that the simple 
 supposition of the prevalence of such a force will give us, as a 
 result, the existence of the other phenomena — of many of them, at 
 least — which our observation has recognized as other forms of force. 
 Gravity is abundantly familiar to us as connecting the mass of the 
 earth itself with the objects upon its surface; and Newton extended 
 it to the moon, and determined first her motions, and then the 
 motions of the celestial bodies generally, to be governed by the same 
 force. But when we come to reason about the force which governs 
 the relations of physical objects to each other, we fail to recognize 
 
 246 
 

 Natural Theology oi the Doctrine of the Forces. 709 
 
 it with any similar distinctness; indeed, we have failed to recognize 
 it at all. Yet even here it exists, and our observation, if nice 
 enough, could not fail to distinguish it. 
 
 The proceedings of the Royal Astronomical Society (vol. xiv) 
 contain a very interesting account of the exact methods employed 
 to ascertain, and to measure, the force of gravity between bodies of 
 moderate size on the surface of the earth. Dr. Maskelyne had 
 previously determined the fact that the attraction of a precipitous 
 mountain influences the direction of a plummet hanging near it, 
 and swerves it from its true perpendicular position ; but more precise 
 and extended experiments were required, for the production of 
 accurate standard measures of length, which had been determined 
 upon by the British government ; and the work was undertaken by 
 the highest scientific skill. A cylinder of lead was cast, with the 
 utmost care to obtain it pure and make it uniformly dense; from 
 this were turned, with exactest nicety, two spheres of lead of some 
 twelve inches diameter, for attracting-balls. Then two small balls 
 were added with delicate torsion suspenders, the motion of which 
 was to be accurately observed. But, alas ! after weeks and months 
 of observation, only the most irregular and inconsistent results were 
 obtained. It was found, upon inquiry of the most successful 
 continental observers, that the slightest changes of temperature 
 between the bodies were sufficient to invalidate the results. It was 
 necessary to deposit the apparatus in an underground apartment, 
 so as to obtain as nearly as possible, an absolute uniformity of tem- 
 perature, and to observe it by means of a telescope through a glass door, 
 in order to detect the slight modifications which the attraction 
 exhibited. Still, with such minute care, aided by whatever sug- 
 gestions science could furnish, observations were obtained which 
 authenticated, and measured, the force of gravity as an actually 
 existing and appreciable thing, which exerts an agency between all 
 the masses of matter on the surface of the earth. 
 
 Supposing, then, that such a force exists and operates everywhere 
 around us, let us endeavor to trace it to its results. Recollect that, 
 by the very supposition, its effect must be faint at any considerable 
 distance, save when the masses which attract each other are very 
 great ; but that a force which follows this law, though faint at con- 
 siderable distances, becomes large when the particles are near, and, 
 after it once becomes perceptible, grows immensely with every addi- 
 tional reduction of the distance. Half the distance will give four 
 
 247 
 
710 University Convocation. 
 
 times the force of attraction ; a reduction to the tenth part, will mag- 
 nify the force one hundred times ; and an approximation which reduces 
 the distance to the hundredth part, will raise the force to ten thousand 
 times its original amount. 
 
 Upon this law, a particle brought into close proximity with any 
 small mass must show a faint attraction for it, like that which exists 
 between the movable particles of a fluid and the inner surface of a 
 tube partly immersed in it. Precisely such is the force which we 
 call capillary attraction. Next, bring two molecules into still closer 
 proximity to each other, and the result must be a still more powerful 
 attraction, corresponding to that force of mechanical aggregation 
 which forms the ordinary masses of our less dense minerals, like clay 
 or chalk. Let them come still nearer, into a proximity measured by 
 the minute intervals of thousandths or ten-thousandths of an inch, and 
 the attraction increasing in a proportionate degree inversely, not as 
 the distance but as the square of the distance, must develop a force 
 equaling the highest that we know — that which governs the combi- 
 nations of chemistry, and effects the cohesion of masses of homoge- 
 neous matter, like the pure metallic elements iron, lead, or gold. 
 
 We have only to suppose that the atoms of matter are determined 
 by some such cause as heat, to stand at different distances from each 
 other, and the supposition of one general force, varying as the inverse 
 square of the distance, will give us as the inevitable theoretical 
 result, different manifestations or rather different degrees of attrac- 
 tion, corresponding to most of the well-known forces which exist 
 around us. Thus, gravitation will be but the attraction of masses 
 for each other at considerable or great distances ; capillary attrac- 
 tion will be the attraction of particles by some mass to which they 
 are very nearly approximated ; mechanical cohesion will correspond 
 to the relation of particles brought into much closer proximity — a 
 force of far greater strength, corresponding to the square of the 
 diminished distance ; and the highest of all known forces must 
 inevitably result from bringing the atoms of matter into the closest 
 possible approximation to each other. Our general theory must 
 involve these varied results, when viewed in connection with the 
 varied distances at which we conceive the particles to stand ; and 
 the doctrine spreads a beautiful simplicity and clearness of concep- 
 tion over the whole field of these varied forms of nature's action. 
 The general and diffused forces of the universe may thus be all con- 
 
 248 
 
Natvral Theology of the Doctrine of the Forces. 71 1 
 
 ceived as only varied forms of gravity, acting under its single, simple, 
 and beautiful, law of the inverse square. 
 
 Nor is there any reason to doubt the actual existence of such vast- 
 amounts of force in these minute relations. Tyndall abundantly 
 illustrates the immense power of these molecular forces. He 
 describes the manner in which an iron cylinder, half an inch thick, is 
 burst with ease by the expansion of a small quantity of water freez- 
 ing within it; and mentions that metallic cylinders of double that 
 thickness, are unable to resist the force with which a small voltaic 
 battery effects decompositions. 
 
 The same writer, speaking of the forces involved in the molecular 
 changes which accompany chemism, says : 
 
 " The energy of the forces engaged in this atomic motion, as 
 measured by any ordinary mechanical standard, is enormous. I have 
 here a pound of iron which, on being heated from 32° to 212° F., 
 expands by about -g-^o-th of the volume it possessed at 32°. Its aug- 
 mentation of volume would certainly escape the most acute eye ; 
 still, to give its atoms the motion corresponding to this augmentation 
 of temperature, and to shift them through the small space indicated, 
 an amount of heat is requisite which would raise about eight tons 
 one foot high. Gravity almost vanishes in comparison with these 
 molecular forces ; the pull of the earth upon the pound weight as a 
 mass, is as nothing compared with the mutual pull of its own mole- 
 cules. Water furnishes a still subtler example." * * * " Sup- 
 pose a pound of water heated from 3f C. or 39° F. to 4£ C, that is, 
 one degree ; its volume at both temperatures is the same ; there has 
 been no separation of the atomic centers, and still, though the vol- 
 ume is unchanged, an amount of heat has been imparted to the water 
 sufficient, if mechanically applied, to raise a weight of 1,390 pounds 
 one foot high." * 
 
 Pursuing the illustration, he estimates the force employed in com- 
 bining one pound of hydrogen with eight pounds of oxygen, to form' 
 water, as " equal in mechanical value to the raising of 47,000,000 
 pounds one foot high." The substance would then be in the form 
 of vapor, and, "to condense this to a liquid, would require a power 
 equal to 6,718,000 foot-pounds ; and still, further, to bring the fluid 
 water to the form of ice, would require a force of 993,564 foot-pounds." 
 
 " I think, " he observes, " I did not overrate matters when I said 
 that the force of gravity was almost a vanishing quantity, as exerted 
 
 * See Tyndall's Lectures on Heat. 
 
 249 
 
712 University Convocation. 
 
 near the earth, in comparison with these molecular forces." Strangely 
 enough, Tyndall does not here recognize these molecular forces as beino- 
 themselves but manifestations of the force of gravity exerted between 
 atoms, though elsewhere he shows that the conception is not altogether 
 an unfamiliar one to him. But, translating his statement into its 
 more appropriate terms, I will call upon you to observe the immense 
 energy with which gravity unites the particles when once they are 
 fairly brought within the scope of each other's attraction. They are 
 held to each other with a power that we can hardly estimate. The 
 force requisite to unite one pound of hydrogen with eight of oxygen, 
 and condense them to ice, can be estimated only by millions — not less 
 than 55,000,000 of pounds ! Most truly does the same writer say on 
 another occasion, " The force with which bodies expand when heated 
 is quite irresistible by any mechanical appliances that we can make use 
 of. AV these molecular forces, though operating in such minute 
 spaces, are almost infinite" (mark the word) "m energy." Here, 
 again, I must venture to put in a correction. It is not " though" 
 operating, but because operating in such minute spaces; it is because 
 the atoms are brought into such close approximation, that the amount 
 of force is so immensely great. That any mass of matter, brought 
 indefinitely near another, must experience a vast force of attraction, 
 is a simple consequence of the law of the inverse square ; but as it 
 is only these minute atoms which can be so closely approximated to 
 each other as to feel the full power of each other's attraction, it is 
 between them only that we find this extraordinary intensity of force. 
 The sphere of their operation is reduced to the most contracted limit ; 
 but within that sphere they are boundless. The atomic forces of 
 nature are the great forces, and, in precise accordance with the funda- 
 mental law, they are vast, just in proportion to the nearness of the 
 objects on which they act ; and within the inappreciably small dis- 
 tances of which we have spoken, the force must be of necessity, 
 •immeasurably great. 
 
 This is the limit to which the physical observer carries his reason- 
 ings. But the process cannot stop here. It is an accepted doctrine of 
 our natural philosophy that, in every union, chemical or mechanical, 
 with which we are acquainted, the particles still stand at appreciable 
 distances from each other : and still more recently it begins to be 
 affirmed, as an indispensable element of our physical reasonings, 
 that the particles of every solid body are permanently in some kind 
 of regulated motion or vibration. The spaces in which these mole- 
 
 250 
 
Natural Theolog y of the Doctrine of the Forces. 713 
 
 cular movements take place, must be considerable when compared 
 with the magnitudes of the moving particles themselves. The 
 physicist sometimes startles his hearers by the statement, that the 
 immense orbits of the heavenly bodies are not more vast in compari- 
 son with the diameter of the planets, than are these inter-atomic 
 spaces in comparison with the dimensions of the vibrating atoms. 
 The distances, therefore, which separate the particles of a solid, from 
 each other, even in the closest unions that we know, are not only 
 appreciable, but must- be regarded as relatively very great. What, 
 then, must follow when the approximation becomes more complete — 
 when the atoms stand, perhaps, much nearer than in our closest 
 chemical combinations ? Especially, what must follow when the dis- 
 tance is absolutely overcome and annihilated, and the particles of 
 matter are brought into absolute contact with each other? Plainly, 
 by all laws of reasoning, the force must in that event become infinite. 
 As the distance diminishes, the force increases ; and this by a rate more 
 rapid than the diminution to which it corresponds, even as the 
 inverse square of the diminished distance. Increasing, therefore, 
 by this advancing rate, the growing force must rapidly outrun all 
 measurement ; and with the cessation of all interval between the 
 particles, it necessarily surpasses all finite quantity, and becomes 
 absolutely infinite. The conclusion may be surprising, even startling ; 
 but one fails to discern any consideration which should lead us to 
 call it in question. 
 
 And why should we be unwilling to admit it? Did we not just 
 now hear our great expounder of physics — Tyndall himself — say 
 that these forces are " almost infinite? " But why " almost ? " The 
 limitation is altogether gratuitous. " Not only almost," a greater 
 authority than he once said, "not only almost, but altogether." 
 If they are almost infinite at the minute distances which we know, 
 what are they, what must they be, when the distances are annihilated, 
 and each atom is given up to the full force of the attraction which 
 embraces and holds it ? 
 
 Every established principle of reasoning — even of our most exact 
 and mathematical reasoning — points to this single conclusion. When 
 of two terms inversely related to each other, one wholly disappears, 
 the other can be expressed by no sign but that of infinity ; nor can 
 we refuse to admit the result without impeaching the very principles 
 upon which all reasoning in physics depends. 
 
 Such, then, must be our general inference from the prevalence of 
 
 [Senate No. 32.] 46 251 ■ 
 
714 ' University Convocation. 
 
 the admitted law of gravitation throughout the universe — that an 
 infinite force is exerted in connection with every particle of matter. 
 
 Of the objections which may be suggested to this result, I cannot 
 here stop to take particular account. It is clear, however, that no 
 one of them can possess any weight against our conclusion, which is 
 not of equal validity against the law of gravitation itself. It may 
 be said that that law 'is valid for perceptible distances, but that we 
 do not know it to be so at the infinitesimal distances to which our 
 reasoning refers. But it is evident that this is imposing upon a 
 known law, a modification which has no ground but our ignorance. 
 The atom is wholly beyond the sphere of observation, and we have 
 no right to assume, without some necessity to dictate the procedure, 
 that within the inter-atomic spaces, the law is at all different from 
 what we discern it to be in those which are open to our observation. 
 
 Another objection to the conclusion which I have affirmed, arises 
 from the belief that the supposition of a repulsive force becomes 
 necessary, to account for the continued separation of particles, which 
 must otherwise inevitably be crowded together into a perfectly com- 
 pact and dense mass. To this it may be replied, that it is nut 
 repulsive force that causes smoke to rise from the earth in the 
 atmosphere, or a cork in water ; neither does a specific force of that 
 kind need to be supposed, to preserve the equilibrium of the 
 planetary system. Perhaps, therefore, some other supposition may 
 be found adequate for a similar result in the case of the particles ol 
 matter. Possibly enough the established system of molecular 
 motions, already referred to as existing in every mass of matter, as 
 heat, or some similar form, may be found quite sufficient to prevent 
 the apprehended consequence of a crush of all material particles 
 into a common center. 
 
 I can only say that, upon a somewhat careful consideration, I 
 have found no objections that seem to be of any very decisive 
 weight agaiftst the conclusion which I have been led to form. For 
 the present, therefore, that conclusion must stand unopposed as the 
 only rational result of accepted scientific principles; and we are 
 driven to admit that the surest of our physical determinations — the 
 law of the inverse square — implies the existence of an infinite force 
 governing each particle of matter.* 
 
 * The only objection which it seems important to discuss is that which arises from the idea that 
 the force of attraction between any two bodies must be measured from their centers of gravity ; and 
 that its maximum cannot be developed by any contact of mere surfaces. 
 
 252 
 
NA TURAL THEOL OGY OF THE D CTRINE OF THE FOR CES. 715 
 
 The next thought to which our reasonings conduct us is, that this 
 infinite is one of a very high kind. It is not the simple infinite which 
 would be furnished by the law of a force increasing inversely as the 
 distance; though that, too, would give an infinite as the result in 
 every case of the actual contact of particles. But this is an infinite 
 of what mathematicians call the second order, involving an immensely 
 higher degree of force, and corresponding to the geometrical laws 
 which necessarily govern the diffusion of any emanation. 
 
 It operates, too, in every possible — nay, in every conceiveable — 
 direction, from every particle as a center; so that we have both an 
 infinite of intensity, and an infinite of direction, involved as conse- 
 quences of our original admission of the universal prevalence of the 
 law of the inverse square. It becomes evident, upon consideration, 
 that this astonishing intensity of force cannot be the endowment of 
 the atom of matter with which, to ordinary view, it seems to be con- 
 nected. We come then next to inquire, what is the seat of this 
 infinite force to which we have been brought ? In what does so vast 
 and amazing a power inhere, and to what does it belong ? 
 
 It is here to be observed that force is not an independent and sub- 
 stantive entity ; it cannot be conceived as capable of existing alone. 
 It does not float free in the universe. By its very nature it exists, 
 always as a quality of some substance. As motion never can be 
 conceived as real, without something to be moved, so force never can 
 
 This objection rests on the demonstration of Newton, that the sum of all the attractions of a 
 number of particles free to move, is precisely the same as if the whole were con centrated at the 
 center of a spherical mass. From this datum it is inferred that the maximum of force could be 
 developed only by contact of the centers, and as these must forever be separated by the sum of the 
 two radii, the absolute maximum never can be reached. 
 
 To any such reasoning, however, it may be replied, that the center of gravity is not an objective 
 fact, but only an abstraction of the mind itself; it is a conception formed for the simplification of 
 the mechanical and astronomical problems which present themselves, but by no means an objective 
 reality. The resultant of two impulses upon a body, is motion in an intermediate direction, and this 
 may be treated and reasoned of precisely as though the impelling cause were one. But the philoso- 
 pher who should argue on that supposition as an actual fact, might not be farther from the truth 
 than is he who conceives the familiar abstraction of the center of gravity to be the real point of the 
 development of force. 
 
 Moreover, Newton's demonstration, on which the objection is based, has reference to the parti- 
 cles of a mass not subjected to the disturbing influence of any other attraction. For matte r under that 
 condition, his conclusion is valid. But when the mutual attraction of two such masses is in ques- 
 tion, the conditions of the problem are altered. The center of gravity for each, is no longer at the 
 absolute center of the mass, but approaches that side on which the attracting body exerts its influ- 
 ence. The conception, therefore, of two centers of gravity, coincident with the centers of the two 
 masses, is materially inaccurate. As the two masses approach each other, the two centers of gravity 
 may, perhaps, be more and more removed toward their surfaces, in the line which joins the centers 
 of the two bodies, till, at the moment of contact, they may even coincide in the point of junction 
 and constitute only a single mass. 
 
 It seems, therefore, altogether legitimate to say that, even upon the supposition of the reality of 
 the center of gravity as the point of maximum energy, the objection cannot be decisively maintained. 
 
 253 
 
716 University Convocation. 
 
 be conceived except as the attribute of some substance to which it 
 belongs and on the existence of which its own existence is depend- 
 ent. Force is evermore the quality or attribute of something to 
 which it belongs, or in which it inheres. 
 
 To the inquiry above suggested, we are not yet in a position to 
 return a complete answer. All that we can now say is, negatively, 
 that there is no reason to think that such an astonishing amount of 
 force can be the endowment of the elementary atom. The minute 
 particle cannot possess this infinite force. It would violate every 
 law of our thinking to imagine such a thing. The atom cannot 
 be the infinite ; cannot possess the infinite. This minimum of possi- 
 ble existence cannot exert the maximum of power. We must look 
 elsewhere for its seat. ' 
 
 Nor can we, on other grounds, admit such a supposition, since we 
 should, in that case, be forced to concede the existence of many such 
 infinites. If each particle were to be conceived as capable of exert- 
 ing an infinite force, we must at once admit an indefinite number of 
 such infinites, a conclusion against which all philosophy revolts. 
 There can be no such multiplicity of infinites. The idea is at war 
 with all simplicity, and with all comprehensiveness, of thought. 
 
 A more precise consideration of this subject will greatly contribute 
 to support the conclusion that the force is not inherent in matter at 
 all. Indeed, it is by no means in matter that we find the force 
 which is the subject of our reasonings. The very existence of the 
 force is indicated to us, not by anything in the particle itself, but 
 simply by its motion, by its change of position in reference to other 
 particles. Of no other relation does the theory take cognizance 
 than this alone. Heat is a mode of motion, and heat is identical 
 with light, and identical with electricity, magnetism, etc. All these 
 manifestations are referable to the movements of atoms in space, and 
 gravitation does but sum up all these movements in the one compre- 
 hensive formula, which states the mode in which this force varies 
 with the varying masses and distances of the objects upon which it 
 acts. No one of these forces has any recognizable relation to the 
 constitution, or gives us the least frisight into the structural relations, 
 of the atoms which they govern. They relate exclusively to the move- 
 ments of these atoms with reference to one another. The fact, the law, 
 and the specific character, of these changing place-relations — these are 
 all that our several sciences profess to ascertain for us. In light, we 
 have the measured vibrations which give us, by their motion, the 
 
 254 
 

 Natural Theology of the Doctrine of the Forces. 7 J 7 
 
 sense of color ; in heat, we have a mode of motion, less rapid and 
 regular, but still only motion ; in electricity we have attraction and 
 repulsion ; in magnetism polarity — that is, motion of particles and 
 of masses, from or toward the poles of a magnet ; in the voltaic cir- 
 cuit, besides the two last mentioned, we have the transfer of particles 
 from the positive to the negative pole, and chemical combination 
 and decomposition ; and in gravitation — that comprehensive form 
 which, as I have maintained, sums up all the rest — we have only the 
 movement of particle and mass toward a center. Everywhere we 
 have motion simply, mere change of position and combination ; and 
 motion is always ab extra. Every motion of matter that we know, is 
 from some external source. 
 
 E~ow, in all these forms of motion there is no indication whatever of 
 anything inherent in the particle, and no question of any such 
 thing. The particle simply changes its place and its arrangement 
 with others. It is attracted or repelled — combined or detached — 
 permanently or transiently, and with more or less intensity ; this is 
 all. We have simply the evidence of a force which controls the 
 movements of atoms in space — a force everywhere present through- 
 out space, and impressing motion upon the particles of matter in 
 accordance with laws — or more properly, with a law, since all are 
 one — of great simplicity and comprehensiveness. 
 
 But there is no indication that this force, which ever holds matter 
 in its mighty and comprehensive grasp, is resident in the atoms 
 which it controls. All that we ascertain of it shows it rather to be 
 pervasive, and universal. It reaches from atom to atom, and on, 
 from atom to more distant atom ; from mass to mass ; from planet 
 to planet ; from system to system. It fills the minute spaces which 
 separate atom from atom ; it spans the chasm between orb and orb ; 
 it reaches from system to system of the galactic mass, to which sys- 
 tems and suns belong — it stretches onward and outward, and above 
 and below — through ether and media, and whatever else, till it fills 
 the very immensity of nature, as the separated particles of matter 
 never do and never can. 
 
 Now, surely, the force which is known to us solely as determining 
 the position of particles in space, and as impressing movement upon 
 them, is not to be conceived as residing in the particles themselves. 
 It exists no more truly within the atoms than it does without. It 
 has nothing to do with their specific constitution or character, and 
 does but impart impulse and motion to them. It is not confined and 
 
 255 
 
718 University Convocation, 
 
 limited, belonging to this atom or to that, but pertains to some- 
 thing which is all-pervading, and which occupies every void space in 
 which a material atom exists arid moves. 
 
 Why limit it to the particle which it controls and adjusts, when 
 it exists in every minute void, and extends throughout every vast 
 read), of the boundless universe to which our observation can pene- 
 trate ? Evidently such a limitation is needless and gratuitous. The 
 cosmos is no chaos of ten thousand conflicting forces, seated in as 
 many separate atoms of matter, and forming a combination which is 
 but the resultant of unnumbered oppositions of independent powers. 
 It is a harmony, and it is one. It is one, by virtue of its great, 
 simple and comprehensive law, which is the harmonious operation 
 of a single grand universal and infinite force, pervading and control- 
 ling its every part. To this result, the doctrine of the unity and the 
 correlation of the forces, inevitably conducts us. 
 
 And is it not thus that the thoughtful mind has ever imagined it 
 to be i An Infinite Force, everywhere present, impressing itself 
 upon every particle of matter, giving law to the universe and impart- 
 ing motion to its otherwise dead masses and forms — to that the 
 human mind has ever been trying to lift itself — it has been the 
 aspiration and the aim of every noble soul. To that science, after so 
 long wandering amid facts, and phenomena, and laws, now seems 
 making its way, and coming to support the aspiration she has some- 
 times seemed to suppress and smother. 
 
 After long dealing with forces and principles that seemed as 
 diverse and conflicting as the forms and phenomena of matter, 
 science gains a glimpse, nay a conviction, that beneath all these 
 varied forms there is one general system of laws, simple and far- 
 reaching; and drawing her breath with a wonder that is half delight 
 and half awe, she exclaims, " The forces of nature are all oneP 
 Yes ; so the devout mind has always understood it to be ; all forces 
 in this vast scheme of nature are manifestations of one ; all life and 
 movement have one great Author. 
 
 Pondering yet more profoundly this great generalization, science 
 still further announces that this universal force is a force inherent, not 
 in the particles of matter, but in something which pervades the uni- 
 verse, giving movement and law to all matter, and establishing har- 
 mony throughout all nature. And what is this but the recognition 
 of an immaterial ground and source of all the phenomena of the 
 world about us ! One comprehensive and universal Force, of infinite 
 
 256 
 

 Natural Theology of the Doctrine of the Forces. 719 
 
 intensity, of unlimited extent, of immaterial nature. Such is the 
 issue to which the doctrines of the convertibility and correlation of 
 the forces are bringing the scientific mind of our day. Shall we 
 not accept the conclusion which does but translate into a scientific 
 formula the long familiar language in which theology has ever pro- 
 claimed one infinite, omnipresent, and spiritual, Lord of the universe, 
 and say with satisfaction and joy, that surely the long conflict of 
 scientific and religious thought must be approaching its end, when 
 both acknowledge the universal sway of the one infinite force, which 
 is at the same time, the All ? 
 
 Perhaps, however, a conclusion so gratifying may seem a little 
 premature. Is it quite certain that the acknowledgment of a univer- 
 sal force, must carry with it the certainty of so complete a harmony 
 of thought in these two departments of reasoning ? Let us look 
 somewhat more carefully into the nature of our apparent result. 
 
 Our conclusion is that the agencies of nature are to be referred to 
 one comprehensive force. But surely force is not God. In order to 
 any very distinct appreciation of that conclusion, we need to deter- 
 mine somewhat more accurately what our conclusion amounts to. 
 
 What, then, is force ? 
 
 This inquiry is one which physical science, with all its effort at the 
 accurate measurement and general identification of the forces, has 
 hardly taken up for investigation. She has been content to rest in a 
 vague acceptance of the conception as something generally known, 
 with little attempt to ascertain its precise content of meaning. 
 
 One writer has indeed attempted a definition, but the inadequacy 
 of the result becomes painfully apparent upon a moment's considera- 
 tion. " Force," he declares, " is motion." As much motion as there 
 is, so much force there is, and no more. But call it by what name 
 you will, it must surely be admitted that there is force where there 
 is no motion. The stones of an arch press with a very positive and 
 unmistakable force, upon the abutments ; but if the arch is sound 
 there is no motion, and can be none. This is identifying the agent 
 with one of the familiar phenomena by which it manifests itself, and 
 through which we recognize it ; but the phenomenon of motion is 
 not the force which causes the motion. The meaning of the word 
 motion is abundantly clear ; in its original and physical sense, it 
 denotes simple change of place ; and this is not what any man ever 
 meant by the word force. Force has indeed a relation to motion ; it 
 is even that which produces motion ; but it is not itself motion. 
 
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720 University Convocation. 
 
 When we look upon a handful of gunpowder we may well believe 
 that there is an immense force connected with those little black 
 grains ; but to say that there is any motion of them, except by a 
 loose metaphor, would be affirming what our senses of sight and feel- 
 ing positively deny. 
 
 This attempted definition, however, is interesting, inasmuch 
 as it is the frank expression of a great embarrassment in physical 
 philosophy. Strictly, it is plain that force is not mere motion ; 
 and yet it becomes clear, on reflection, that it is only as expressed 
 by means of motion, that physical science can recognize force 
 at all. The energy — if it is more satisfactory to the scientific 
 reasoner to describe it by that term — out of which motion arises, 
 science cannot distinctly recognize as separate from the motion 
 itself; not because the two are indistinguishable, but because there 
 are no physical terms for the description of the hyper-physical source 
 from which motion originates. 
 
 So far is it from being true that force is conceived as identical with 
 motion, it is not as motion that, even in physical nature, force is 
 revealed to us. We become acquainted with it not as motion, but as 
 resistance to our own voluntary effort. When, for instance, I 
 attempt to break a stick, or to tear a piece of paper, I become 
 acquainted with the cohesive force which holds atoms together, not 
 by any motion in it, or in them, but simply by its resistance to my 
 own exercise of power. The type of force is not motion, but resistance^ 
 which is rest* — the balance or equilibrium of forces. So, I become 
 acquainted with gravity as a force, not by the observation of motion, 
 but by the resistance which it offers to my own attempt to uphold 
 an unsupported body. 
 
 Indeed, I do not become aware of the force which I myself exert in 
 connection with my physical system, through any observation of the 
 motion which it produces. When a man, in walking rapidly, comes 
 in contact with some fixed object, and receives a blow, or a shock, 
 from the collision, the physiologist tells him that we put forth a great 
 deal more force in our ordinary movements than we are at all aware 
 of. This internal exertion of force becomes so familiar, in its ordinary 
 exercise, that we often do not notice it; and the motion which is pro- 
 duced by it fafls entirely to suggest to the mind our own very active 
 exertion, until some resistance rudely awakens us to a knowledge of the 
 very energetic efforts which we are almost unconsciously putting forth. 
 
 * Hesto, or re-mto; not to move, but to stand. 
 
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Natural Theology of the Doctrine of the Forces. 721 
 
 With the exception of this one attempt, I know of no effort to 
 define force by any physicist; and this is simply a confusion of 
 motion with the condition on which it depends. The omission is 
 so great that it naturally suggests inquiry. How is it that scientists, 
 so much concerned with the subject as to have studied very labori- 
 ously the relations of each form of force to the others, and to have 
 reached the grand generalization which unifies all the specific forces 
 of nature, have never made any serious effort to define this ultimate 
 element in which all their researches terminate? How is it that 
 they have never felt the need of an accurate determination of the 
 meaning of the one word of transcendent importance, and of con- 
 stant occurrence, in all their inquiries? All the movements of 
 nature, we are told, are due to one force ; and this force is forever 
 indestructible, and its amount forever equal and undiminished in 
 the universe; but when we ask, "What is force?" we have no 
 answer, and nobody has ever thought of the propriety of framing 
 an answer, or has any answer to give. 
 
 The only explanation of so great an oversight, is to be found in 
 the fact that the conception of force is one of those universal ideas 
 which belong of necessity to the intellectual furniture of every 
 human mind. It is one of those simple and essential elements of 
 our knowledge, which are imparted to us by the very action 
 of our own minds ; and which, therefore, may well be assumed as 
 universally known. But force is not an object of the senses, and 
 no examination. through any organ of sense, or through any instru- 
 ment of observation, can detect its presence. It is not phenomenal ; 
 does not reveal itself through any manifestation, but belongs to the 
 interior nature and constitution of things. Hence, though all 
 physical science supposes it, and all scientific reasonings assert or 
 assume its existence, science can give no account of it by any 
 physical characters. It has no form or color for the eye, and no sound 
 for the ear ; it has no odor, nor feel, nor taste. It is neither solid, 
 fluid, nor gaseous; it does not crystallize in any one of the six 
 regular systems of the mineraldgist ; it does not combine according 
 to any chemical formula ; it finds no place in any latest list of the 
 sixty or seventy known elements. Physical science, therefore, has 
 no means of defining it. The definition must be looked for in quite 
 another direction. The question, what force is, our physical philo- 
 sophy has no means of answering; and hence it is no scandal, nor 
 reproach, that she has never undertaken to answer it. That deter- 
 
 259 
 
722 University Convocation. 
 
 mination must come from a nicer analysis than either the qualitative, 
 or the quantitative, method of chemistry. 
 
 All this is simply saying that the conception of force is meta- 
 physical, rather than physical, and is derived from the mind and 
 not from matter. It cannot, therefore, be analysed in either the 
 wet or the dry way ; unless, indeed, the metaphysical analysis of 
 abstract ideas should be decided to belong, as I think has sometimes 
 been suggested, to the latter method. 
 
 What, then, is force, metaphysically? How do we become acquainted 
 with it in the sphere of the mind ? To what extent is it known to 
 us as an element of our psychology ? 
 
 To these questions, the answer is not difficult. We become acquainted 
 with force as an element of our own personal experience. We are 
 conscious of the exercise of something which we call energy, force, or 
 power, in our own mental states. Throughout that sphere, we are 
 familiar with the great conception of action ; and action is the exercise 
 of force. The mind is constitutionally endowed with a power of 
 action ; and this power of our spiritual nature is what we mean b}^ force. 
 Force, then, is the active nature of a cause ; that quality by virtue of 
 which it acts, and produces effects. It is one of the elements of our 
 very being — an essential quality of our intellectual nature. We are 
 often conscious of the exercise of this activity, and recognize a power 
 in ourselves by which we are capable of exertion and effort. 
 
 This exercise of our activity we become aware of in all the forms 
 of perception and consciousness. Thus we hear some sound, but are, 
 unable to distinguish it clearly, and to decide upon its character; and 
 we listen with attention, with an effort, to discriminate it from other 
 sounds, and to learn its true nature. So, too, in vision, we examine 
 by the eye with a similar strain of attention. In our ordinary visual 
 perceptions, the phenomena are so obvious that we are not conscious 
 of any effort in observing them. Hence metaphysicians have often 
 been disposed to speak of the mind as passive in its recognition of 
 physical objects. But when the object is very minute, or the charac- 
 ters indistinct, what a consciousness of effort there is in our determina- 
 tions ! The botanist, for instance, who examines with his glass the 
 obscure organs of some small flower, how strenuously does he exert 
 his whole faculty of vision, to make sure of the facts upon which his 
 classification depends ! 
 
 The same remarkable circumstance occurs, also, in our purely men- 
 tal action. What efforts do we sometimes make of memory, to recall 
 
 260 
 
Natural Theology of the Doctrine of the Forces. 723 
 
 a lost fact ; of conception, to grasp a vague idea, and reduce it to dis- 
 tinctness ; of thinking, to trace out conclusions and consequences ! In 
 ever j form of intellectual action we find frequent occasion to exert 
 our power of knowing — that inherent and universal quality of our 
 active mental being. 
 
 Now, in all these varied experiences of our consciousness, we 
 observe and recognize the idea, and the fact, of power or force. It is 
 originally known to us as a quality of the mind, ever acting, ever 
 revealing itself in this inner sphere. Here we become acquainted 
 with force, and learn to discriminate and to understand. It is the cor- 
 relative of action ; it is that by which we can act ; and action is simply 
 the exertion of force. Here, we know something about it, as in 
 physics proper we do not ; and we distinguish it from all other things 
 by the clearest, surest, and most familiar, experience. 
 
 Now, with 'this knowledge of force, psychologically gained, we are 
 able to understand ourselves when we speak of force in the world 
 without us. When asked, " What is force ? " we cannot, indeed, 
 reply in terms of physical science, or physical quality, but, in the 
 language of our mental experience, we can give ready and decisive 
 answer. It is the capacity of acting, the power of exertion, which 
 we ourselves possess, and which we exercise in all our actions. 
 Action, you will observe, is our only word to describe a phenomenon 
 of the mind ; we can designate our mental changes only as actions. 
 The word derives its whole meaning from our inward experience in 
 consciousness ; and its explanation, when applied to any physical fact, 
 can be found only by going back to the original sphere of its occur- 
 rence, and noting what it meant there. All actions of material 
 things have a meaning derived from the action of the mind, with 
 which they are conceived to be in some real analogy. Force, too, 
 has in our experience the same hyper-physical origin, and the same 
 intellectually determined signification ; and, apart from this, the 
 word means nothing, and its use describes nothing. It denotes a fact 
 of deeper meaning than the mere phenomena of our observation. It 
 describes that profound and productive energy which underlies all 
 the phenomena of the universe. Force is the energy of a cause ; and 
 the universal force, to which all specific forces and movements are to 
 be referred, is the power, ever present, and everywhere active, of 
 one comprehensive and universal Cause. 
 
 The bearing of this conclusion upon natural theology is immediate, 
 and important. Every force is the quality of some cause ; but it is 
 
 261 
 
724 University Convocation. 
 
 primarily known to us as the endowment of the mind. The only 
 cause of which we have any direct and immediate knowledge, is the 
 mind itself; the only force, the force of our own minds. Anything, 
 then, which becomes known to us through the exercise of force is 
 presumably a mind. I have already shown that the forces which 
 govern matter are not the attributes of the material particles them- 
 selves ; they are one, and however seemingly different, they are but 
 varied forms of the force-activity of one universal Cause. But as the 
 only force known to us is the attribute of an intellectual being, 
 the presumption is, that the comprehensive force of the universe is 
 of the same kind ; it is the attribute of an intellectual and spiritual 
 being like ourselves. Such is the presumption, for such is the only 
 force the existence of which we positively know; and this -fact 
 throws the burden of proof on him who denies the intellectual and 
 spiritual character of this force. It is contrary to the analogy of our 
 knowledge to suppose the existence of any other force than such as 
 we know ; and whoever does it, assumes the obligation of proving the 
 reality of what he assumes. 
 
 But, though it would be legitimate to do so, we need not rest here. 
 The advance is easy to whatever conclusions the theological hypothe- 
 sis requires, though, under the limitations to which such a paper as 
 this is confined, I can only indicate very briefly, the general nature 
 of the reasoning which establishes them. 
 
 This universal Cause, then, or to use scientific language, the one 
 force, is, in the next place, creative. It has shaped and moulded the 
 cosmical system. Of creation, in the sense of an absolute production 
 of matter, science knows nothing. Whence matter came she does not 
 assume by any methods of her own, to determine. The only creation 
 that she knows, is the shaping of the celestial orbs, and the adjust- 
 ment of their positions and motions ; and these are due to the one 
 force which we have described and identified. She tells us how in 
 the beginning matter existed, " without form and void " — a limitless 
 and universal mist — an omnipresent star-dust throughout space ; how 
 gravity, and heat, and the other forms of force began to condense, 
 and to unite, the severed particles, and to aggregate them into per- 
 ceptible magnitudes ; how, as the process went on, revolving rings and 
 spheres were formed throughout the celestial spaces ; and how they 
 became consolidated into the rolling orbs of our visible heavens. 
 All this is familiar to us as the teaching of the nebular hypothesis; 
 and it shows that the force of the universe is creative and construc- 
 
 262 
 
Natural Theology of the Doctrine of the Forces. 725 
 
 tive, and has given to the system of things its orderly and beautiful 
 motion, its profound mathematics, and its elegant geometry. 
 
 A similar method of reasoning will disclose to us the intelligence 
 of this creative power. We infer that the Author of so much that 
 our intelligence comprehends and delights in, must be itself intelli- 
 gent. Nor in this inference, do we at all depart from the accepted 
 methods of scientific investigation. 
 
 Hitherto, and before the establishment of the doctrine of the 
 convertibility of the forces, phenomena of each specific kind had to 
 be separately investigated, and the facts of each class to be organized 
 into a separate science. Those facts could not, at that stage of 
 investigation, be referred to any recognized agency, or be classed 
 with any other phenomena. They necessarily formed a group by 
 themselves, and were treated as the subject-matter of a distinct 
 science. Thus electricity, galvanism, heat, and the other physical 
 agencies, formed so many separate departments of knowledge, and 
 gave rise to so many independent sciences. In each one of these 
 the method adopted was that of determining the character of the 
 unknown force, from that of the phenomena. These, classified and 
 arranged, gave the law of the mysterious agent with which we 
 were dealing, and indicated to us all that we could know of its 
 nature, and of its methods of operation. Thus, in gravity, we had 
 the conclusion of a force, the law of which was that of the inverse 
 square ; in magnetism, the inference was of a force acting in curved 
 lines from one pole to the other of a magnet. Universally, the 
 character of the unknown agent was reached by inferences derived 
 from the observation of its phenomena of force-activity. 
 
 We adopt the same method in our teleological reasonings. We 
 study the phenomena as our observation discerns them, and they 
 indicate the law of the unknown force to be that of intelligence. 
 It is the force of something which acts, as we do, from a perception 
 of reasons and for the accomplishment of ends. It has all the charac- 
 teristics of an intelligent and spiritual nature, like that of the human 
 mind.* 
 
 Did time permit, it would be interesting to proceed, and under 
 the same scientific sanction, to develop yet further the characteristics 
 
 * How simply, and yet how forcibly, has Cicero expressed this idea, in those elegant writings 
 which have given instruction and delight to the cultivated minds of every subsequent age : 
 
 "Quumque sint ia nobis consilium, ratio, providentia, necesse est deos hcec ipsa habere majora ; 
 nee habere solum, sed etiam his uti, in maximis et ia omnibus rebus." See The Be JTalura, 
 Lib. II, 79. 
 
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726 University Convocation. 
 
 of this creative and general Agent. I might show that it is a free 
 and elective force, acting under the law, not of necessity, but of adap- 
 tation and choice, and possessing herein the eminent characteristics of 
 a spiritual being; and that beyond even this, it is manifested to us as 
 a moral and benevolent being. It is a person ; a being who is per- 
 cipient not only of mechanical exigencies and contrivances, not only 
 of ideas and laws, but of moral relations, and of benevolent and 
 holy ends. The creative force of nature belongs to a Spiritual 
 Being — is the attribute of an Infinite God. 
 
 Such, then, is the general method which our reasonings must fol- 
 low ; and such are the conclusions which arise from the new aspect 
 of the physical philosophy of our day. Surely they are of a most 
 interesting kind. Science comes to recognize force as the basis of 
 all life and motion in the universe, and she decides that the force is 
 forever one. But force is spiritual and intellectual, and the neces- 
 sary, or at least the probable conclusion is, that the one force is that 
 of a spiritual being. Force, however, is an intellectual conception, 
 and can be known only by a study of the mind. Science, therefore, 
 is not the study of nature alone ; it embraces as well, the study of 
 man. Science cannot assert the existence of force, without some 
 knowledge of the human mind from which alone the idea of force 
 is derived. All true science, therefore, involves both the knowledge 
 of nature and the knowledge of man ; it includes the study of mind, 
 as well as of matter. A philosopher may pursue either ; but he can 
 have no complete knowledge of what he investigates, without bor- 
 rowing from the other department of investigation. If the scientist 
 would understand that force which is the great result of his discov- 
 eries, he must learn it in, and from, the mind, in which alone we 
 discern its character, and learn its reality : if the metaphysician 
 would understand the abstractions with which he deals, he must 
 study them in connection with their manifestation in nature. All true 
 science implies a knowledge both of nature and of man ; and the 
 knowledge of nature and the knowledge of man, together, give us, 
 beyond all contradiction, beyond all mistake, the knowledge of a 
 universal, infinite force, residing in an intelligent, moral, and per- 
 sonal Being; or, in other words, the knowledge of God. 
 
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