'U^U^^;-^ LIBRARY UNIVEi^SlTY Of CALIFORNIA SAN DIEGO J BD 181 C3 UNIVERSITY OF CALIFORNIA SAN DIFGO 3 1822 01104 3130 Hs ^'^ PHYSICAL REALISM rm.NTKD BY SrOTTlSWOODE AND CO., NEW-STllEET .SQUARE LONDON y/ /V'///. J PHYSICAL EEALISM BEING AN ANALYTICAL rillLOSUPllY FEOM THE PHYSICAL OBJECTS OF SCIENCE TO THE PHYSICAL DATA OF SENSE BY TUCJMAS CASE, M.A. FEI.I.OW AND .?)(7^ai cXfyKTtKO)^' AmSTOTLR LONDON L X G :^I A N ^, G Pt E E X, A X D C 0. AND NEW yOKK : 15 EAST 10"" STUEET 1888 All ii(//il.' r^.trrrril ' Neque tamen illis nihil addi posse affirmamus : sed contra, nos, qui Mentem respicimus non tantum in facultate propria, sed quatenus eopulatur cum Eebus, Arteni Inveniendi cum Inventis adolescere posse, statuere debemus.' Bacon, Nov. Org. i. 180. TO WILLIAM S. SAVOEY, F.E.S. SUKGEOX-EXTKAOEDIXAEY TO II. M. THE QUEEN l'EESIl>ENT OF THE UOYAL COLLEGE OE SUKGEOKS OF EXGLANl' HUKGEON TO ST BARTHOLOMEW'S HOSPITAL CONTENTS PART 1. GENERAL PBOOF OF PHYSICAL REALISM. I, THE PHYSICAL OBJECT OF SCIENCE .... II. IDEALISM AXD REALISM ...... III. THE PHYSICAL DATA OF SENSE .... IV. THE HISTORICAL ORICxIN OF PSYCHOLOGICAL IDEALISM 3 13 40 82 PART II. PSYCHOLOGICAL IDEALISM. V. DESCARTES .... VI. LOCKE VII. BERKELEY .... VIII. Berkeley's theory of vision . IX. HI'ME ..... X. KANt's 'critique' and NECESSARY TRITIIH 101 141 186 225 2nG .•;i9 APPENDIX .383 Part I. GENERAL PEOOF OF PHYSICAL REALISM. ' Itaque contemplatio fere desinit cum aspcciu ; adeo id rerufn invisibilium exigua aut nulla sit observatio.' Bacon, Nov. Org. i. 50. B CHAPTEE I. THE PHYSICAL OBJECT OF SCIENCE. ' Natural Philosophy, as now regarded, treats generally of the physical universe, and deals fearlessly alike with quantities too great to be distinctly conceived, and with quantities almost infinitely too small to Le perceived even with the most powerful microscopes ; such as, for instance, distances through which the light of stars or nebulas, thouoh moving; at the rate of about 186,000 miles per second, takes man}^ years to travel ; or the size of the particles of water, whose number in a single drop may, as we have reason to believe, amount to somewhere about 10^'', or 100,000,000,000,000,000,000,000,000. Yet we successfully inquire not only into the composi- tion of the atmospheres of these distant stars, but into the number and properties of these water-particles ; nay, even into the laws by which they act upon one another.' This quotation from Professor Tait's ' Eecent Ad- vances in Physical Science ' is a recognition of the reality of the insensible, and of its knowledge by the natural philosopher, as facts. No metaphysical theory of existence can be complete, unless it recognises the known reality of the insensible physical world ; and no psychological theory of human knowledge can be accepted as even a probable hypothesis, unless it B 2 4 niYSICAL REALISM part i. explains liow these scientific objects of human know- ledo-e are known from the orisjinal data of sense. The distinction between the sensible and the scien- tific;, the apparent and the real, the perceptible and the imperceptible, is not only a scientific fact but has be- come a commonplace in natural philosophy, without having produced any marked effect in mental philo- sophy. Astronomy has long opposed the real to the apparent motions of celestial bodies ; and Sir Isaac Newton carried this contrast so far as to oppose abso- lute, true and mathematical, to relative, apparent and common, time and space. In physics, apparent size is the room which a body seems to occupy, physical size is the real space taken up by its particles. Not only physics, but chemistry and biology unite in the anti- thesis of molar and molecular motion, in recognising therefore motions which are for the most part imper- ceptible, in resolving what seem to our senses to be heterogeneous qualities into mere varieties of imper- ceptible motion, and in referring these motions to particles which are as imperceptible as the motions themselves. In all these sciences the latent structures and processes of things are opposed to their external appearances and perceptible changes. I do not mean that these undeniable conclusions, very far removed as they are from the original data of observation and experiment, are at all inconsistent with the sensations, perceptions, observations, or exjDeriences which ordinary men have, and from which the natural philosopher starts. On the contrary, the very untutored senses themselves are best explained — na}^, can be only explained — by statements at first sight opposed to them. It is only in appearance that the motion of the earth round the sun contradicts our senses, for, though CHAP. I. THE PHYSICAL OBJECT OF SCIENCE 5 it contradicts one single appearance, the whole sum of astronomical observations is only to be explained by means of it. Similarly, when it is said that one thing is apparently larger and physically smaller than another, vision is contradicted, but the sense of touch is justified, and our experience as a whole explained. The latent motions of particles, into which sensible qualities are resolved, at first sight contradict but really explain the whole system of our sensations of touch, vision, and hearing. But though the results of science thus explain the data of sense, it must be remembered that they only explain them, and are not themselves data of sense. No man can make himself see the earth going round the sun, except by standing on the sun itself. No man can see liij;ht at the moment when it starts from a distant star vears before it reaches his senses. Micro- scopes can be multiplied in power, but they are millions short of the actual (I do not speak of the potential) divisibility of the particles of things. Moreover, the natural philosopher gives even greater reality to the imperceptible than to the perceptible. The astronomer not only opposes but prefers real to apparent motion, the physicist physical to apparent size, and all natural philosophers latent structures and molecular processes to masses and their molar motions. It is not too much to say, that the mission of modern as well as of ancient philosophy is to convince mankind that sense is unequal to the subtlety of things ; to get behind the scenes and see the machinery of nature at work ; to recognise the insensible as real, }'es, and more real, than the sensible. Sense is not science. Our knowledge is not limited to sensible phaino- mena. We are quite as certain of the existence of 6 PHYSICAL REALISM part i. that wliicili cannot be brought within our sensibiHty as of that which can, and of objects which we do not experience as of ()l)jects of experience itself. Further, we are quite as certain that they exist in space and in time ; for if they are not in space they have no size, if they are not in time they have no dura- tion, and that which has neither any size nor any dura- tion is nothing ; and, if they are neither in time nor space, they do not move, for motion is change of phice in space during time. Space and time are not mere forms of our sensibihty, but conditions of things and their motions beyond the range of our sensibiHty. We not only know that the imperceptible exists, and that it exists in space and time, but also we know im- perceptible attributes both of the perceptible and of the imperceptible. For example, I know that the hour-hand of my w^atch moves, though I cannot perceive it moving, as well as that the minute-hand moves which I can per- ceive moving with difficulty, or the second-hand which I can perceive moving with ease. I know that the im- perceptible particles of matter gravitate imperceptibly towards one another, as well as I know that their masses gravitate, and that unless gravitation is true of the former, it is not true of the latter. Still more insensible are cohesion and chemical affinity, which are imper- ceptible motions exerted between imperceptible particles and at imperceptible distances. The whole of modern science is based on the fact that there are numerous latent structures and latent processes which are known to be real attributes of particles themselves latent. He, then, wdio will venture to assert, as mental philosophers often do assert, that the attributes which we ascribe to things are simply the phtenomena or the sensations which they cause in us, must be prepared to deny all CHAP. I. TIIE PHYSICAL OBJECT OF SCIENCE 7 the imperceptible structures and motions which are recognised as attributes of things in natural philosophy. Natural philosophy does not stop at the reality and knowledge of imperceptible things and their imper- ceptible attributes. It takes one step further : it regards the imperceptible as not only real but causal. In the first place, among imperceptible objects there are latent processes of cause and effect, no part of which can be represented by a sensible object. When, for example, the physicist declares that the medium called asther remains fixed in space, while each successive part of it undulates in consequence of the previous undulation of another part, in the same manner as water communi- cates successive waves, he afiirms that the whole of this propagation of undulations through sether is real, though the whole of it is imperceptible. Secondly, he affirms still more ; he affirms that the imperceptible undula- tions not only cause one another, but finally cause our sensations of li;e of it to arise in us, cannot be an invention. There is a thing beyond sense, a reality beyond phainomena, not only actual in nature, but known to science. There is a thing real and known which is not a sensible phasnomenon, because such things as imperceptible particles are known really to 8 PHYSICAL REALISM part i. exist, though they are incapable of becoming sensible. There are attributes real and known which belong to this thing, but are not sensations or sensiljle plia3- noniena, because such attributes as the imperceptible motions of imjoerceptible particles are known really to take place, although they are not capable of becoming sensible. Finally, these real things by these real attributes are real and known causes of human sensa- tions because the imperceptible motions of the imper- ceptible are known really to cause sensations of light and other sensations in men, although the latent pro- cess, by which an imperceptible motion such as the undulation of tether produces sensible light, is totally beyond the reach of sense, which perceives not the undulation but the sensible result. Thus real things and real attributes transcending yet really causing sensa- tions are, in some way or other, known to the natural philosopher. The insensible, then, is not a simple reality, but contains three realities, all insensible : real substances, real attributes, real causes of sensations. There are things in themselves. A thing in itself might mean a thing out of all relations. In this sense nature contains no things in themselves ; it is a system of related things the universe of which is alone out of relation as the sum of all relations. But this is not what is meant by a thing in itself in philosophy : what is reallv meant is not a thing out of all relations, but a thing distinct from the phtenomena it causes in us, a thing in itself as opposed to its sensible appearance. In this meaning, nature contains infinitely more things in themselves than it contains phaenomena ; and man, as a natural philosopher, knows things in themselves which are not phaenomena, when he knows imperceptible particles ; knows not merely the phaenomena which CHAP. I. THE PHYSICAL OBJECT OF SCIENCE 9 they cause in us, but their real attributes, when he knows imperceptible motions, and knows that the thing in itself, not as an ' unknown cause,' but by its real attributes produces phasnomena, when he knows that imperceptible things, by their imperceptible motions, cause human sensations. There are real things known, real attributes known, real causes known, beyond the phsenomena of sense. All this knowledge does man as a natural philosopher possess of things in themselves. Two antitheses have been handed down to us from ancient philosophy, the natural and the supernatural, the visible and tlie invisible. These distinctions are often treated as convertible ; but they are not so. The natural and the visible are not identical ; and the super- natural and the invisible are not identical: there is a natural yet invisible world. Between the extremes of visible nature and the invisible supernatural world there is an invisible nature, distinct from both ; a world which is neither in heaven nor in man, but in itself. If we combine both the antitheses, they cease to be double, and form this triple division : — 1. The natural and visible, e.g. sensible pheenomena. 2. The natural and invisible, e.g. insensible bodies and imperceptible particles. 3. The supernatural and invisible, e.g. God. Natural philosophy is the science of nature visible and invisible. From the former it infers the latter. But it stops at nature. So far as it is the science of an invisible nature, it is a philosophy of the suprasensible, not a theology of the supernatural. It outruns sense, but walks with reason to knowledge, without flying to faith. That we know invisible nature beyond sense in natural philosophy is a simple fact, explicable by logical 10 PHYSICAL REALISM part i. reasoning from sense. Can we in theology further know the invisible beyond nature as well as beyond sense ? Can we know the supernatural world and God by reason- ing from sense ? These are questions beyond natural philosophy. But the theologian may be sure that, on the one hand, unless we can vindicate our knowledge of insensible nature, we can hardly hope for a know^- ledge of an insensible world beyond nature ; and that, on the other hand, reasoning from sense to nature encourages reasoning from nature to God. Natural philosophy is the first step beyond sense into the unseen world, within which natural theology soars heaven- wards to tell Of things invisible to mortal sight. I will conclude tliis chapter by quoting, from Sir John Herschel's ' Discourse on Natural Philosophy,' a passage which is sufficiently near to the existing state of science for our present purpose. Its value is that it groups together a number of scientific conclusions, which, as it seems to me, cannot be explained by any theory of reality except realism, or the theory that there is a real and known world beyond phasnomena, or by any process of knowledge except syllogism, or deductive inference which carries reason beyond sense. ' What mere assertion will make any man believe, that in one second of time, in one beat of the pendulum of a clock, a ray of light travels over 192,000 miles, and would therefore perform the tour of the world in about the same time it requires to wink with our eye- lids, and in much less than a swift runner occupies in taking; a single stride ? What mortal can be made to believe, without demonstration, that the sun is almost a million times larger than the earth ; and that, although CHAP. I. THE PHYSICAL OBJECT OF SCIENCE 11 SO remote from us that a camion-ball shot directly towards it, and maintaining its full speed, woukl be twenty years in reaching it, it yet affects the earth by its attraction in an inappreciable instant of time ? a closeness of union of which we can form but a feeble and totally inadequate idea, by comparing it to any material connection ; since the communit^ation of an impulse to such a distance, by any solid intermedium we are acquainted with, would require, not moments, but whole years. And when with pain and difficulty we have strained our imagination to conceive a distance so vast, a force so intense and penetrating, if we are told that the one dwindles to an insensible point, and the other is unfelt at the nearest of the fixed stars, from the mere effect of their remoteness, while amono' those very stars are some whose actual splendour exceeds by many hundred times that of the sun itself, although we may not deny the truth of the assertion, we cannot but feel the keenest curiosity to know how such things were made out. ' The foregoing are amongst those results of scientific research which, by their magnitude, seem to transcend our power of conception. There are others again, which, from their minuteness, would elude the grasp of thought, much more of distinct and accurate measure- ment. Who would not ask for demonstration, M^lien told that a gnat's wing in its ordinary flight beats many hundred times in a second ? or that there exist ani- mated and regularly organised beings, many thousands of whose bodies laid close together would not extend an inch ? ]>ut what are these to the astonishing truths which optical inquiries have disclosed, which teach us that every point of a medium tlu'ough which a ray of light passes is affected with a succession of periodical 12 niYSICAL REALISM part i. movements, reguLirly recurring at equal intervals, no less than five hundred millions of millions of times in a single second ; that it is by such movements, communi- cated to the nerves of our eyes, that we see — nay, more, that it is the difference in the frequency of the recur- rence which affects us with the sense of the diversity of colour ; that, for instance, in acquiring the sensation of redness our eyes are affected four hundred and eighty- two millions of millions of times ; of yellowness, five hundred and forty-two millions of millions of times ; and of violet, seven hundred and seven millions of millions of times ? Do not such thino-s sound more like the ravings of madmen, than the sober conclusions of people in their waking senses ? ' They are, nevertheless, conclusions to which any one may most certainly arrive, who will only be at the trouble of examining the chain of reasoning by which they have been deduced ; but, in order to do this, something beyond the mere elements of abstract science is required. Waiving, however, such instances as these, which, after all, are rather calculated to surprise and astound, than for any other purpose, it must be ob- served that it is not possible to satisfy ourselves com- pletely that we have arrived at a true statement of any law of nature, until, setting out from such statement, and making it a foundation of reasoning, we can show, by strict argument, that the facts observed must follow from it as necessary logical consequences, and this not vaguely and generally, but with all possible precision in time, place, weight, and measure.' CHAP. IJ. 13 CHAPTER II. IDEALISM AND KEALISM. The problem of this essay is to use the insensible world of science as a fact from which to find the nature and origin of knowledge. Science is systematic know- ledge. Yet the mental philosopher usually contents himself with endeavouring to explain ordinary know- ledge. If he is a mental physiologist, it is true, he also uses natural science to proceed from the organs to the functions of sense. But there is another use of natural science to mental philosophy, which has been too much neglected : the objects of science are as important as the bodily organs to the explanation of knowledge. Natural science should be used to ascer- tain what we know as well as how we know it. More- over, the insensible physical world of the natural philosopher ought to prove to the mental philosopher that neither all knowable objects nor all sensible data are psychical, but some are physical. I purpose to show that physical objects of science, being objects of knowledge, require physical data of sense. Hence this essay is called Physical Eealism. We must confront natural with mental philosophy. The former has outstripped the latter. Natural i)hiloso- phers have long ago discovered to a great extent how pli3'-sical nature is the causa essendi of sensible data. ; but mental philosophers have failed altogether to show 14 PIIYSICAl. REALISM rAiir i. how sensiljle data are the causa cognoscendi of physical nature. Tlie reason is, the data are mainly unknown. The existing hypotheses of the origin of knowledge do not explain the facts of science, and too often end by denying what they fail to explain. Especially to blame is the hypothesis that all the data of sense are psychical facts, such as sensations and ideas, from which there is no way to insensible but physical objects of scientific knowledge. This vicious hypothesis is psychological idealism. Hence this essay is designed to combat psychological idealism by means of physical i-ealism, and to appeal from the hypothesis of psychical data to the ph^'sical ol)jects of science. The physical world of science cannot be explained by the common hypothesis that all sensible data are psychical, nor without the more moderate hypothesis that some are physical. The motto of all idealism is ideale prius reale posterius. But it has many meanings. Anaxagoras founded philosophical idealism by the proposition that the Divine Intelligence is prior to the order of nature ; and in adding that soul is also prior to body Plato became its second founder. The Cartesian idealism means that knowledge begins with psychical ideas, and the Kantian idealism that it adds a priori mental ele- ments. Of these idealisms two are of supereminent importance in the history of thought ; that which places God at the beginning of the world, and that which places psychical ideas at the beginning of knowledge. The former is the belief of the majority of mankind, the latter of most philosophers since Descartes. The former is theological, the latter psychological idealism. Theological and psychological idealism are not necessarily connected. A philosopher may hold that God causes physical nature and man apprehends it. CHAP. II. IDEALISM AND REALISM 15 He may be theologically an idealist, psycliologically a realist. On the other hand, he may snppose that all sensible data are psychical facts, and yet doubt the existence of God. He may be psychologically an idealist, theologically an atheist. The founders of natural theology had no thought of making psychical facts the becrinnings of human knowledge. The followers of Hume hardly consider themselves supporters of the doctrine that God created the world. These distinctions are of importance, because there is a crude notion in our times that idealism in mental philosophy is necessary to theology. They are of special bearing on the scope of this essay, which is aimed, not at theo- logical, but solely at psychological idealism. Psychological idealism began with the supposition of Descartes that all the immediate objects of knowledge are ideas. From Descartes it passed to Locke and Berkeley. But with Hume it changed its terms from ideas to impressions. Kant preferred phsenomena, Mill sensations. The most usual terms of the present day are sensations, feelings, psychical pha3nomena, and states of consciousness. But the hypothesis has not changed its essence, though the idealists have changed their terms, — Verbum, non animum, mutant. They at least agree that all sensible data are psychical objects of some kind or other. The psychological idealists differ widely about the origin of knowledge from these psychical data. Some of them hold that there are a priori elements contributed b}^ mind to the psychical data of sense, others that these supposed elements are a posteriori. But this difference about the origin does not prevent them from agreeing about the object of sense, which they alike hold to be some kind of psychical fact, whether idea, im- 16 PHYSICAL REALISM pakt ]. pression, phn3nomenon, sensation, feeling or state of consciousness. There is a further difference among the idealists. Some of them, beginning witli Descartes, believe that, thongli the immediate objects of sense are psychical, reality also includes physical facts. Others, beginning with Berkeley, reply that psychical data cannot yield physical objects, and therefore the psychical is all that is known to be real. The former divide reality into the psychical and the physical, the latter resolve it wholly into the psychical. The former have been called Cosmothetic Idealists, and the latter Absolute or Pure Idealists. But, while they differ only about the objects which can be mediately known, they still agree about the immediate data. Starting from the common hypo- thesis that all sensible data are psychical, the cosmo- thetic idealist nevertheless believes in physical realities, but the absolute idealist denies or doubts them. Cosmothetic idealists further differ amoncf themselves about the physical world. Descartes held that a physical world can be known through the medium of ideas ; Locke, in one of his many moods, that it is a cause of ideas, but unknown. This difference is important, because cosmothetic idealism is the usual view of men- tal physiology in our own time, and it is held in both forms. Mental physiologists have unwarily received from psychologists the hypothesis of psychical data, which they usually call sensations, and have at the same time learnt from nature that the data of sense are effects of physical structures and motions beyond sense. Hence they are cosmothetic idealists. But according as they are rather physiologists or rather psychologists, they lean to Descartes or to Locke. The former hold th.nt. starting from psychical sensations as CHAP. II IDEALISM AND REALISM 17 data, by inference we know their physical causes ; the latter, that the psychical sensations are produced by the physical causes, which are nevertheless unknown and unknowable. Their differences, however, do not dis- turb the consensus that the immediate objects of sense are not physical, but purely psychical. It may be thought that this consensus of idealism is a proof of truth. But agreement is one of the chief causes of human error, because it tempts men to dis- pense with further consider-ation of the question. More- over, we shall find that the inconsiderate assent to this common proposition is the very reason why opposite schools of idealists cannot conclusively answer one another. Lastly, there are two kinds of consensus : one, assent to a self-evident principle, such as 1 + 1 = 2; the other, agreement in a common hypothesis. Now the proposition that all sensible data are psychical phasnomena is not a self-evident principle, but a de- batable hypothesis. Eealism is the philosophy of a reality beyond psy- chical facts. The earliest form in which it was a conscious doctrine was the belief in the reality of universals. Plato thought that there were universal forms existing in themselves, incorporeal and super- natural archetypes, in accordance with which similar individuals are produced in nature. Aristotle agreed that there are real universal forms, and even that they are incorporeal substances. He contended, however, that they exist not in themselves but only as belonging to individual substances, which are concretions of matter and form. In the Middle Ages the disciples of Plato and Aristotle were called Eeales, to distinguish them from the Nominales, who either contended that uni- versals were merely general names, or else general c 18 rilVSICAL REALISM r.uiT i. conceptions. Those who adopted the hitter view were afterwards called Conceptualists. It is not necessary to be either a Platonist or an Aristotelian. There is a third realism of universals possible ; and that, too, without falling into nominalism or conceptualism. The theory of the reality of univer- sals, though overlaid with many errors, contains two important truths. The first is, that science knows of classes which have an indefinite number of similarities, such as triangles, colours, and living beings. The second is, that of these similarities some are fundamental, others derivative ; e.g. three-sided rectilineal figure is the foundation of innumerable other similarities of tri- angle ; undulations of ether produce the facts of colour, metabolism is the basis of the fiicts of life. The first truth shows that a natural class, or real kind, is not a name, nor a notion, but a real sum of individuals form- ing an indefinite number of similarities. The second truth shows that the distinction between essence and property is not a nominal difference depending on the meaning of a name, nor a notional difference depending on the analysis of a notion, but a real distinction depend- ing on the fundamental character of the similarities, on which the rest depend. Without natural classes, whose similarities can be expressed in laws, there would be no science ; and without essences, or fundamental similarities of those natural classes on which other similarities depend, we could not have the mathematics of the triangle referring its propositions back to its being a three-sided figure, nor the physics of light^ referring all the facts of (colour back to the undulation of £ether. A natural class, then, is the sum of individuals possessing an indefinite number of similarities. A real CHAP. n. IDEALISM AND EEALIS3I 19 essence is the fundamental similarities of the individuals of a natural class. It is easy to make too much of it or too little. If we follow the nominalist, and make asthereal undulation the meanino- of the name ' lio-ht,' or the conceptualist, and make it the analysis of the notion, we make too little of it, because the undulation of asther began before, goes on without, and will last after, our names and notions. If, on the otlier hand, we follow Aristotle, and make it an incorporeal sub- stance coexisting with matter, we make too much of it, because it is only a motion of matter after all ; while, if we try to soar with Plato into the supernatural world and make it a heavenly archetype of earthly light, we fail to explain the facts and desert science for mysticism. The realism of universals, however, is not the business of this essay. There is another meaning of realism, which we may call the Eealism of Tudividuals. This is the theory that there is a phj^sical world of individuals beyond psychical sensations and ideas. It may be held with any theory of universals ; the realist of individuals is not necessarily a realist of universals. It is also a later product. The realism of universals is rather a doctrine of ancient, the realism of individuals rather of modern, philosophers. Not that Aristotle rejected the distinct reahty of physical individuals ; but it never occurred to him that it needed to be proved. There was, as Brandis remarked, an uncon- scious realism in ancient philosophy. It seldom doubted a world beyond the psychical ; the question was rather whether there were not three worlds; naliirnl individuals, supernatural universals, and ps3^chical in- telligences. ]3ut in modern times the development of psychological idealism has brought even the physical 20 PHYSICAL REALISM part i. world of individuals into question. In opposition to this psychological idealism a conscious realism has arisen, the object of which is to show that there are physical things beyond psychical facts. This realism of physical individuals is part of the business of this essay, and for shortness will in the sequel be called simply Eealism. Eealism is constantly misunderstood. It is some- times supposed to be a synonym for mere Sensualism, or the belief that physical things are as they appear to our senses. But sensualism is only a crude form of realism. There is a realism which goes beyond sense to science, and holds that things are not as they imme- diately appear to sense, but rather as they are mediately inferred by science. A more serious misunderstanding is the confusion of realism with Materialism. Material- ism is a kind of realism ; it is also more. It is a double hypothesis : first, that there are physical things ; secondly, that they are either the only realities, or at least are prior to psychical realities, whether in nature or in man. Only the first part of this hypothesis is essential to realism ; the second part, which contains, too, the real sting of the materialist, is unnecessary to the realist, A man ceases to be a materialist, but he remains a realist, if he holds that God is the Creator and Governor of the world, while the world is not a psychical fact of God's Intelligence but a physical effort of His Intelligent Will ; and that nature is posterior to God though prior to man. The motto of materialism is, reale prius ideale 2'>osterius : the motto of realism is reale non est ideale. In short, it is one thing to affirm a natural world of individual objects beyond sense, another thing to deny a supernatural world beyond nature. CHAP. II. IDEALISM AND REALISM 21 Hence realism is not the exact contrary of all idealism. It is not opposed at all to the idealism of natural theology. It is not even the direct contrary to all psychological idealism. Idealism centres itself on the data, realism on the objects of knowledge. The former says that aU sensible data are psychical, the latter that some objects are physical. Hence a difficulty in contrasting them, and even in keeping them distinct. Some idealists, as we have seen, though they regard all data as psj^chical, admit the independent reality of physical objects. As Hamilton has pointed out, the cosmothetic idealists are also hypothetical, or, as some would say, transfigured realists. The exact contrary of realism is not all idealism but pure or absolute idealism. The pure or absolute idealist denies the reality of aught beyond the psychical world, the realist affirms the reality of the physical. At the same time realism is not a single body of doctrines. Eealists agree only in one position — the reality of physical things. In the foundations of that position, in the sensible data of knowledge, they differ toto ccelo. It is, therefore, necessary to classify them to prevent confusion, and that sort o{ ignoratio elenchi,\\\\\Q\\ idealism and realism alike have to suffer from their opponents when they are not properly defined. Of the realism of individuals there are two species recognised among modern philosophers — the Hypo- thetical Eealism of the cosmothetic idealists, and the Intuitive or Natural Eealism of the Scotch philosophers, Eeid, Stewart, and Hamilton. Agreeing about know- able objects, hypothetical and intuitional realists differ about the data of sense. According to the former, the data are psychical ideas or sensations of the ego ; ac- cording to the latter, they include the primary qualities 22 PHYSICAL REALISM taut i. of llie physical non-ego. Agreeing in a physical world, they differ about the way in which it is to be reached, the former holding that it is inferred from psychical data, the latter that it is innnediately perceived. Hypo- thetical or transfigured realism is the hj'-pothesis that our senses present psychical ideas or sensations repre- senting external physical objects ; intuitive or natural realism, the hypothesis that the senses present the pri- mary qualities of external physical objects themselves. Modern philosophy exhibits a constant oscillation between the opposite poles of, the ego and the non-ego ; and the two received kinds of realism are opposite cur- rents in this oscillation. The cosmothetic idealist or hypothetical realist, learning from natural philosophy that his senses do not directly perceive external things, takes refuge in the psychical world of his own soul. Dissatisfied with this alternative, and conscious that he somehow apprehends something physical, the in- tuitional realist flies forward to the direct perception of an external world. Extreme views are usually as untrue as extreme measures are dangerous. Is there a via media ? I venture to propose a new Eealism. When I consider the objects of science, I am struck by the enormous number of things and attributes entirely beyond the reach of sense and not even corresponding to any sensible object. I refer, espe- cially, to corpuscles, their structures and motions. Secondly, on going further, I find that the whole ex- ternal world has been discovered l)y sciences, such as optics, acoustics, and biology, to be insensible, and that nothing is sensible except what has been impressed on the body, and in the body on the nervous system, of a sentient being. Thirdly, I notice that a connection has been scientifically established between external in- CHAP. II. IDEALISM AND REALISM 28 sensible objects and the objects of which I am sensible. The former are causes of the latter. They are also found to resemble one another in primary qualities, such as duration, extension, motion, but not in secondary qualities, such as light, heat, and sound ; for the se- condary qualities, as they are in external nature, are found by corpuscular science to be insensible modes of primary qualities ; light, heat, and sound being all insensible modes of motion producing a heterogeneous effect on the senses. I cannot believe that this whole fabric of insensible objects can be scientific, yet unknown. But it must be either physical or psychical. If the ol)jects are psy- chical, they are either sensations or ideas. But they are insensible and often inconceivable. Now what is insensible cannot be a sensation, and what is incon- ceivable cannot l)e an idea. Not all oljjects of science, then, are either sensations or ideas ; therefore they are not psychical objects at all. It remains that they are physical objects. Again, I cannot believe that this whole fabric of physical objects of science can have been inferred without sufficient data of sense. I therefore proceed to iiKpiire what data of sense are required to infer a physical object of science. This is a question of logic. Now the rules of logic teach me that whatever is inferred is inferred from similar data. If I infer that all men will die, it is because similar men have died. Now, as we have seen, physical objects are scientifically inferred from sensil)le data. It follows that the sensible objects, which are these data, must also be physical. The similar can be inferred only from the similar, therefore the physical can be inferred only from I lie physical. This conclusion, however, places me in a dilemma. 24 PHYSICAL REALISM part i. Science shows me tliat the object of sense is internal, logic that it is physical. The former evidence might incline me to cosmothetic idealism, the latter to intui- tive realism. Which shall I prefer ? Am I to say that the sensible data are psychical objects within me ? No, because I require physical data of sense to infer physical objects of science. Am I to say that the sensible data are physical objects without me ? No, because no external object is sensible. I can be neither a cosmothetic idealist, because of logic, nor an intuitive realist, because of natural science. If, then, natural science requires that the object of sense must be within my nervous system in order to be sensible, and logic that it must be physical in order to infer physical objects of science in the external world, how can the sensible object be at once physical and internal ? I answer, it is the nervous system itself sensibly affected. The hot felt is the tactile nerves heated, the white seen is the optic nerves so coloured. The sensible object must be distinguished from its external cause on the one hand, and on the other hand from the internal operation of apprehending it : it is the intermediate effect in the nerves produced by the external cause, and apprehended by the operation of sensation. In particular, the operation and the object of sensation must not be confused, because the former may be psychical, the latter is physical. There is some plausibility in saying that the act of consciously touch- ing is psychical, there is none at all in saying that the hot felt is psychical. Non sequitur. Vision may be a psychical sensation, but the white seen is a physical object. Nor is there any reason why a psychical opera- tion should not apprehend a pliysical object. The sen- sible object then is identical neither with the external CHAP. II. IDEALISM AND REALISM 25 cause nor with the internal operation of sensation. It is the effect in the nervous system produced by the one and apprehended by the other. For example, the hot felt and the white seen are produced by external objects and are apprehended by internal sensations of touch and vision, but are themselves respectively the tactile and the optic nerves sensibly affected in the manner apprehended as hot and white. From such sensible data, internal, as science re- quires, and physical, as logic requires, man infers physical objects in the external world by parity of reasoning. Men in general begin by inferring that physical objects of sense are produced by physical causes exactly similar. Thus from the hot within we infer a fire without. Such objects, directly inferred to correspond with sensible data, may be called the originals represented by them. They are inferred, but are generally said to be perceived ; thus we speak of perceiving the fire though we only infer it. We may, perhaps, say then that the originals of the sensible are insensible objects inferentially perceptible. Afterwards, scientific men carry on this parity of reasoning, and infer that these originals beyond sense consist of further insensible particles similar to the originals, but not at all represented by sensible data ; and that many other objects, such, for example, as the side of the moon always turned from the earth, are incapable of producing sensible objects in us. These unrepresented oljjects may be said to be not only in- sensible but imperceptible, and are objects of an infer- ence which may be called transcendental, in the sense of transcending both sensitive and inferential j)erception. Lastly, science also finds that in another direction the ordinary man has carried his inferences from 20 PHYSICAL IJEALISM part i. similar (lain to similar objects too far. Physical objects arc IbuiMl to be like sensible in their primary, not in their secondary (^nalities ; for instance, external motion is like sensible motion, but external heat is an imper- ceptible mode of motion while sensible heat is not sensibly a motion at all. How is this inferred? Ik'cause, thouo-h at first sif]^ht sensible heat would demand a similar external oliject, when all the facts of sensible heat are accumulated they are found to be tlie kind of facts that are only produced by motion. Hence from sensible physical data we scientifically infer insensible physical objects, like sensible objects in primary but unlike in secondary (qualities. Such is the realism proposed in this essay. It may be expressed in two propositions : there are physical ol)jects of science in the external world ; therefore there are, as data to infer them, physical objects of sense in the internal nervous system. It is a via media between intuitive realism and the hypothetical realism of the cosmothetic idealist. As it recognises physical realities, it is realism. As the objects, which it sup- poses to l)e sensible, are not external but internal, it is not intuitive realism. As the objects of sense, which it supposes to be the data of inferring an external physical world, are not psychical but physical, it is not liypothetical realism. As they are physical data within, to infer physical objects without, the realism which I advocate may be called Physical Eealism. Tliere are three realistic ways of ox})laining our knowledge of an external pliysical world. The first is cosmothetic idealism, wliicli supposes that we are sen- sible of a psychical, Ijut infer a physical world. This is against logic, Avliich shows that all inference is by similarity. The second is intuitive reahsm, which CHAP. II. IDEALISM AND REALISM 27 supposes that we directly perceive an external physical world. This is against natural philosophy, which shows that we perceive nothing directly but what is propagated into our nervous system. The third is physical realism, which supposes that we sensibly perceive an internal but physical world, from which we infer an external and physical world. This agrees with both natural philosophy and logic. Physical Eealism must be especially distinguished from intuitive, or, as it is also called, natural realism. It is true that the theories have some common points. This essay owes to Eeid the instructive remark on the ' Sentiments of Bishop Berkeley,' that there is no evi- dence for the doctrine ' that all the objects of knowledge are ideas in my own mind.'^ The rejection of idealism, the reality of the physical world, the belief in a phy- sical object of sense, and the possibility that a psychical subject may apprehend a phj^sical object, are all points in intuitive realism which find a place in physical realism. But here the agreement ends. The intuitive realist holds an immediate perception of a physical world outside. I distinguish the immediate perception of the physical world within, and the inferential i)er- ception of the physical world beyond myself. The intuitive realist follows the idealist in thinking too much of the sensible data, and too little of the insensible objects of science. He gives too mucli weight to consciousness, and too little to science, or rather too much to the ordinary and too little to the scientific consciousness. He appeals to common sense, which is the problem rather than the soliiliou of philo- sophy. He elevates the dicta of consciousness and ' Reid, Essays on the Intellectual Powers. Essay IT., chap. x. p. 283 (ed. Hamilton). 28 PHYSICAL REALISINI part i. c'oininoii sense from uiianalysed facts into self-evident principles. Hence, in asserting an immediate know- led'^e of external nature lie contradicts science. But we nmst appeal from common sense to universal science, and from ordinary to scientific realism. The idealist can never be answered by asserting the reality of the sensible world, which he admits, and, if it stood alone, could explain. He must be confronted with the in- sensible world of science. The intuitive realists have an impossible theory of the data of sense, comprised of two incompatible ex- tremes. On the one hand, they admit the idealistic position that secondary qualities, as sensible, are psy- chical sensations ; on the other hand, they assert that external primary qualities of the non-ego are imme- diately perceived. The admission is fatal, because the Berkeleian at once points out that primary qualities are apprehended in the same way as secondary, and there- fore if one set, as sensible, are psychical sensations, why not the other ? The assertion is equally fatal, because scientific analysis shows that nothing external is imme- diately perceived. Hence I retract the admission and reject the assertion. Whether directed to primary or to secondary qualities, sense apprehends neither a sen- sation nor an external object, but an internal object in the nervous system. Everything external is inferred. Perhaps the chief reason of the defect in intuitive reahsm is the confusion of object and no7i-ego. Object is the 7^es comiderata apprehended either by sense or by reason. It is not always an external object. In sense, it is always internal, whether it be the hot or the moving, the white or the extended, secondary or primary. In reasoning, it is external, whenever we infer something beyond the sensible object within us. But the intuitive CHAP. II. idl:alism and realism 29 realists, having confused object and non-ego^ supposed that whenever sense has an object it presents the non-ego. Eeally, sense always apprehends an object distinct from the operation, but never a non-ego distinct from the ego^ that is, the man himself. Hence, also, their erroneous belief that in apprehending a primary quality, as an object, sense presents a quality of the non-ego, and in not apprehending a secondary quality as it is in the non-ego, it presents no object. Eeally, as sensible, both primary and secondary qualities are apprehended as objects, but not as external. For example, the sensibly hot and moving are both apprehended as objects by sense, but entirely within the sentient being. The subordination of secondary to primary quali- ties is not at all in the sensible effects, but in the external •causes. In the external world, secondary qualities are found by science to be only specific varieties of primary qualities. In the internal world, all qualities appear to sense to be equally elementary. As sensible, a primary quality, such as motion, is not in the non-ego, and a secondary quality, such as heat, is not a mere sensation ; nor are they both sensations ; but they are both sensible objects, both internal to the sentient being, both physical, both parts of the nervous substance sensibly affected, both apprehended in the same way as objects by the operation called ' sensation.' From these qualities, all apprehended in exactly the same way as sensible objects in our nervous system, the ordinary man infers a complete correspondence of qualities out- side, the scientific man partly corrects him by reducing secondary qualities to primary qualities in the external world. The relativity of knowledge has become a common- place. Is it a fact ? A sensible effect is the result of 30 ■ niYSlCAL REALISM part i. llu' coiiil)iiiatioii of two causes. As active or efficient cause, the external world produces the sensible efl'ect in the nervous system ; as passive or material cause, the nervous system receives this effect according to its susceptibility. Hence the effect is like or unlike to the efficient causes, according to the varying susceptibility of the nervous system. There is a variation in different animals and in different men, and even in the same man at different times. ]3ul in all men there is one differ- ence of main importance. The nervous system is far more susceptible of similar effects from primary than from secondary qualities. It is more capable of re- flectino- the waves of the sea than the undulations of astlier. Not that the effect is wholly alike in primary or wholly unlike in secondary qualities. The primary quality of distance is imperfectly reproduced in sense, the secondary quality of aerial vi])ration is to some small extent represented in the sense of hearing. But, on the whole, there is a general similarity of the sensible to the external in primary, and a general dissimilarity in secondary qualities, because of the inferior susceptibility of the nervous system to receive like effects from the latter qualities in external objects. Tn the sense, then, that the sensible effect only partly depends on tlie external cfficic^it cause, and partly also on the matter of the nervous system, there is a rela- tivity of knowledge to the structure of the nerves. There is also an evolution, which consists in the in- creasing adaptation of the nerves to sustain the effect under the action of the external object. Oil the other liand, l)y the relativity of knowledfi^e it is generally meant that the sensible effect produced is a psychical fact, not partly but wholly heterogeneous to the physical object, if there be one. In this sense CHAP. II. IDEALISM AND REALISM 31 physical realism is opposed to tlie relativity of know- ledge. It is true that red refuses to appear to our senses as a motion representing the external motion which produces it. But the cause of this fact is to he found in the construction of the optic nerve, which, when acted on by a certain imperceptible motion of gether, receives a sensible colour apparently unlike motion, just as oxygen and hydrogen in certain pro- jiortions, when acted on by electricity, become water. In the same way, when a wheel rotates too quickly, the sensible effect ceases to be a motion, because the nerves are insusceptible of taking on so rapid a motion in sense. The sensible effect is similar or dissimilar to the external object, so far as the nervous system is capable or incapable of being affected similar^ to the external object. There is no occasion then to resort to the hypothesis of a psychical relativity : the nervous element is sufficient. Moreover, if there were a psychical relativity, it would be ineradicable, because the sensible effect would then be completely heterogeneous, and would there- fore supply no data of inference to an external phj^sical cause. Eeally, sensible effects are partly like and partly unlike the external causes, because the nerves are partly fitted and partly unfitted to represent them. Being partly like, the nervous unfitness to re- present secondary qualities as they are in nature is being constaiilly ehminated l)y scientific reasoning. Thus, sense sometimes presents motion as motion, but cannot help presenting the hot, the red, c^c., as heteroiieneous to motion, because of the structure of the sensory nerves ; science, by comparing sensible motion with the sensible facts of the hot, the red, &c., infers that the external cause of the latter is really a 32 rnYSICAL realism tart I. mode of motion. In secondary qualities the sensible effect is heterogeneous, but the cause inferred by science is identical with the external object. Not that scien- tific elimination of the defects of sense ever becomes so complete as to end in absoluteness of knowledge. But there is a constant progress towards making science the mirror of being. Sense starts with physical data partly like and partly unlike external nature ; science, by progressive inferences, tends more and more to dis- cover the external qualities which cause not only the like but the unlike data in the nervous system. The sensible, therefore, is not a psychical effect completely heterogeneous to the external physical cause, but a physical effect partly relative to the nervous system ; and science is perpetually correcting this partial re- lativity. It is usual to divide theories of sensation and per- ception into presentative and representative. There are two presentative theories, respectively characterising the pure idealist and the intuitive realist. The former holds that there is no distinction between sensation and perception : sense, according to him, immediately per- ceives psychical facts, which are the sum of known existing objects. The latter distinguishes sensation and perception, because he distinguishes the psychical and the physical : sensation, in his view, is limited to psychical sensations, perception immediately apprehends the pri- mary qualities of an external physical w^orld. The pure idealist says, ' What I see is w4iat exists ; ' the intui- tive realist, ' What exists I see : ' the former reduces nature to perception, the latter brings perception to nature ; one holds esse is percipi, the other esse per- cipitur. But the point is that, according to both, the real is the sensible world, which is directly presented. CHAP. II. IDEALISM AND KEALISM 33 not represented, in perception, withont an inference to an external original. The representative theory, on the other hand, distinguishes the data of sense, as pre- sented, from the external world, as represented, in perception. It exists in many forms, according to various theories of the data of sense. But the current form is that of cosmothetic idealism, which holds that sense presents psychical data of some kind, representing physical objects in the external world. • Physical realism must accept the representative theory, but not in its idealistic form. The data pre- sented to sense are internal, yet not psychical. They are physical parts of the nervous system, tactile, optic, auditory, &c., sensibly affected in various manners, repre- senting, but only partly resembling, the external world. Further, in sense, the object is not the operation, the hot is not touch, the white is not vision, the loud is not hearing. From these points I form the following theory of sensation. In that the sensible object is internal, sen- sation is not the immediate apprehension of an external object. In that the sensible object is physical, sensation is not the immediate apprehension of a psychical fact. In that it is the immediate apprehension of an ol)ject, though internal, it is a kind of perception. I should define sensation, or sensitive perception, as the im- mediate apprehension of an internal physical object within the nervous system of a sentient being. But perception cannot be confined to sensation. Although it is true that sense feels the hot, and reason infers the fire, everybody talks of perceiving the fire. The philosopher will find it vain to fly in the face of the universal language not only of ordinary life but even of science. He must recognise this perception and analyse it. There is, then, besides sensitive or 34 PHYSICAL REALISM tart i. immediate perception, inferential or mediate perception. The former is limited to the internal object of sense, the latter extends to tlie external original. Moreover, so long as we remember that there is an inference in this latter operation, the term ' perception ' not only does no harm but serves to mark a most important distinction. We first infer external originals of sensible objects, e.g. the fire, the sea, &c. ; we cannot be said to see, but we may be said to perceive, these external objects, and also to observe and experience them, though indirectly. Afterwards, we go on to infer other external objects not represented by any sensible object, e.g. a corpuscle, aether : these we cannot be said either to see or per- ceive ; they are not only insensible but imperceptible, and we infer them by reasoning which transcends per- ception. In short, we must distinguish sensitive perception, inferential perception, and transcendental inference. Hence the following classification of physical objects knowable, and of the operations concerned with them : — 1. Internal parts of the nervous system sensibly affected: sensible data : immediately perceptible, objects of sense, or of sensitive perception, observation, ex- perience. E.g. the sensibly moving, the sensibly hot. 2. External parts of the universe : insensible objects : ol)jects of inference. (1) Originals represented by sensible objects, and resembling tin 'in in primary not in secondar}^ qualities : insensible but mediately perceptible objects of inferential perception, observation, experience. E.g. the fire, the waves of the sea. CHAP. II. IDEALISM AND REALISM 35 (2) Objects unrepresented, tliougli causing some sensible objects by imperceptible secondary qualities : the imperceptible : objects of trans- cendental inference. E.g. corpuscles, the undulations of aether. This essay contemplates not only a new realistic hypo- thesis, but a different method from that usually used in mental philosophy. Every philosophy must have a beginning. But the beginning must be what is best known ; and in mental philosophy the present objects of science are better known than the original data of sense. The method in use takes too direct a way of getting at the original data. It is true that the beginnings of human knowledge are sensible data. But the philosopher does not stand at the beginning of human knowledge. Philosophy did not begin with the infancy of the human race. The philosopher cannot observe his own infancy. The sensible data have long since been overlaid with an immense mass of inferences. Hence, though man may have begun once, it is impos- sible for the philosopher to begin now, with the data. Yet most books on knowledge begin with the dogmatic assertion that the immediate objects of the senses are psychical sensations, from which they proceed to allow man as much knowledge of nature as can be squeezed out of the original hypothesis. Ihit the assert ion if self must be proved. Besides the induction of causation, we may either reason synthetically from cause to effect, or analytically from effect to cause. Ihil (he latter is the more usual method, because man knows so much more about facts than about their causes. Hence the order of science is usually the reverse of the order of n.-ituic. 1) 2 36 PHYSICAL IIEALISM tart i. Nature always proceeds from cause to effect, science usually from effect to cause ; so tliat science becomes an analysis of tlie synthesis of nature. Similarly, the order of mental philosophy is the reverse of the order of human knowledge. It is true that the order of human knowledge is from cause to effect in the sense that sensible data are the causce cog- noscendi of physical knowledge. We begin with them as children ; hence also we are tempted to begin with them again as psychologists. But the procedure is fallacious ; we must begin with the more knowable. Now every mental philosopher is an adult man, and every adult man is more certain what he now^ knows, than how he originally came to know it, of the dis- coveries of science than of ' the secret springs and principles by which the human mind is actuated in its operation,' of the known objects than of the sensible data. Accordingly, as, in the science of nature, we must generally begin with present facts and go back- wards to the causce essendi, so, in the science of know- ledge, we must generally begin with the facts of scientific knowledge and go backwards to the causce cognoscendi. Modern philosophers have made the mis- take of attempting to repeat the synthesis of know- ledge from the original data of the child and the race. But we must rather retrace our steps from the present to the past ; instead of trying to follow the synthesis of knowledge from an unknown beginning, we must make an analysis from the present objects of scientific knowledge to the original data of sense. In a word, our method must be an analysis from science to sense. Ilenne, I began with attempting to give an outline of the kind of objects recognised in science. This CHAP. II. IDEALISM AND REALISM 37 begimiins^ has several advantacfes. First, science is knowledge ; hence to begin with its objects is an appeal not from knowledge to reality, but from the data to the objects of knowledge. It is not a dogmatic assertion of what is, but an historical description of what is known. Secondly, science is knowledge at its widest extent, knowledge proceeding from the sensible through the insensible, but perceptible, to the imperceptible world. Hence we get a more extended view of know- able objects than that usually attained by mental philosophers, who tend to concentrate themselves on the world of sense and perception. Thirdly, science is knowledge at its best, whereas the hypotheses of mental philosophers about sensible data can hardly be called knowledge at all. In appealing from the hypothetical origin of knowledge to what is actually known in science, we are appealing from the less known to the more known. In short, we are getting the facts of knowledge, wherewith to test our hypothesis of its causes. The next step is analytically to find the sensible data required to cause the knowledge of the objects of science as facts. All theories of the sensible data and of the origin of knowledge, idealistic and realistic, must be treated and compared as hypotheses. We must ask, indeed, what is their direct evidence, but also and mainly whetlier they account for the knowledge of the objects of science. The general examination of these hypotheses will follow in the next chapter. Afterwards, the various hypotheses of Psychological Idealism will be taken in detail. The elimination of these hypotheses will finally bring us to Physical Eealism. Philosophy began with the external object, which was first of all treated as a pure reality by the Pre-So- cratic philosophers. Gradually it came to be regarded 38 niYSICAL REALISM part i. as also an object of knowledge, a view wliich culminated with Aristotle. Aristotle's method was essentially to be- cvin with being as being, then to consider it secondarily as a knowable object, and thus to proceed from the known object to the knowing subject. Objective are generally the foundation of subjective distinctions in his writings. Descartes revolutionised philosophy by beginning with the conscious subject and passing through its conscious operations to the object apprehended. From his time the general order of mental philosophy has been syn- thetic, from the subjective operations to the objective world. I propose to revert to the old order, and pro- ceed analytically from object to subject, but in a new spirit. Ancient philosophy rightly began with the object, but considered it too much as being, and too little as known. Consequently, it had a tendency to multiply entities without considering whether they are knowable. Hence the Cartesian revolution and the synthetic method from subject to object. But after the first consciousness, I tliink, the object is on the whole better known than the subject ; else natural philosophy would not be more advanced than mental philosophy. In order to avoid at once the dogmatism of ancient, and the doubtfulness of modern, philosophy, I propose to begin wdth the object, not as being, but as known in science, the most perfect form of knowledge. I proceed to ask what sensible objects are required as data for science to know these objects. Of the knowing subject I treat only so far as it bears on the objects known by sense and reason, because, though I know well that I am, I know less what I am than what I know. The ancient method from bein^ to knowing? was the rig-ht order, though too dogmatic in application. The modern CHAP. II. IDEALISM AND REALISM 39 method inaugurated by Descartes, from the subject through the data of sense to the objects of science, was, after its first step, fallacious, because it then proceeded synthetically from the less to the more knowable. The analytic method of physical realism, without neglecting direct evidences of the data, proceeds, on the whole, from the more knowable objects of science to the less knowable data of sense. TABLE OF IDEALISM AND REALISM. Idealism. Kealism. 1. 2. 3, 4. T, Cosmothetic, or m • i t * •*-■ Pure. TT i.-, J 1 Physical. Intuitive. Hypothetical, •' (1) All sensible (l)All sensible (1) All sensible (I) Some sensible data are psy- data are psj'- data are inter- data are exter- chical. cMcal. nal but some nal and physi- are physical. cal. (2) All objects ( 2) Some objects (2) Some objects (2) Some objects knowable are are physical. of science are are physical, psychical. phj'sical. 40 rilYSICA.L REALISM part i. CHAPTEE III. THE PHYSICAL DATA OF SENSE. Nihil est in intelkctu, quod non prius in sensu. How far is this time-honoured proposition true ? As we have seen, it is not true of the objects of science. The whole physical world is beyond the reach of sense, insensible ; the corpuscles, of which it consists, are beyond the reach of inferential perception, imperceptible. It is true that objects of science are similar to sensible objects, but they are not the same. They are objects of intellect which are inferred from sensible objects but have never been in sense. But even this more modest statement must be qualified. In the first place, it requires Locke's correction that knowledge has two sources — sensation and reflection, outer and inner sense, or sense and consciousness. We immediately apprehend not only the objects of, or rather in, our senses, but also ourselves apprehending those objects, and performing many other conscious operations. Secondly, there is also a simpler source than sensation — the feelings. We immediately feel pleased and pained, and that too without apprehending any object ; as in the pain of hunger, the pleasure of nutrition. Sensation is more complex than feeling, be- cause it is the apprehension of an oljject ; touch the apprehension of the hot, vision of the coloured, hearing of the sounding, &c. Frequently we have a feeling and CHAP. III. THE PHYSICAL DATA OF SENSE 41 a sensation together ; for example, when we feel pleased or pained at the same time as we taste sweet or bitter. But it is of the greatest importance to distinguish feeling as a source of knowledge, especially as it is not at all improbable that it was the original source even of sensa- tion. Even now that feeling and sensation are distinct, feelings are still the raw experiences of volitions, passions the beginnings of actions. We feel pleasure and pain before we will to pursue the one and avoid the other. All knowledge, then, does not begin with sensation, but with feeling, sensation, reflection. It is true, however, that all knowledge of nature begins with sensation. Yet even this modified proposition must be carefully guarded. In the first place, though phy- sical knowledge begins with the operation of sensation, it does not follow that the object, in apprehending which the operation of sensation consists, is also a sensation. Yet this non-sequitur appears in the first few pages of most books of modern philosophy. The causes of the confusion of sensation with its object are to be found partly in the structure of modern languages, which, being far richer in abstract than in concrete terms, tempt philosophers to fall into a loose way of speaking of perceiving a sensation instead of perceiving a sensible object ; but mainly in another confusion, that of object and non-ego, which makes philosophers shrink from speaking of perceiving a sensible object, lest they should seem to assert an intuition of the external world. But an object {to dvTLKeLixevoi>) is merely that which is apprehended as opposed to the operation of apprehend- ing it, and is not necessarily external to the apprehend- ing subject. In sense, without being external, the object is still distinguishable from the operation ; the hot from touch, the sweet from taste, the coloured from 42 PHYSICAL REALISM part i. ^•isioll, the loud from hearing, the scented from smelhng. Although, therefore, physical knowledge begins with sensation as an operation, it does not begin with sensa- tion as a sensible object. Given, then, that physical knowledge begins with sense, we still have to ask, what is the object apprehended immediately by sensation; what is the sensibly hot, sweet, coloured, loud, scented? This is the question of the present chapter. There are two main evidences of hypothesis — the direct and the indirect. Direct evidence is the best, if possible, but it is seldom attainable ; for example, there is no direct evidence for the hypothesis of gether. But where direct proof fails, indirect should be all the stronger in compensation. It consists in using the facts to test the hypothesis, and that in two ways. First, the facts must be explained by the hypothesis ; secondly, they must eliminate other explanations. Thus the hypothesis of an undulating aather, as the vehicle of light, though wanting in direct evidence, is proved by its power of explaining all the facts of light, and by the elimination of the hypothesis of emission, which explains some, but not all the facts. I propose to apply these rules to the various hypotheses of sensible data, stated in the last chap- ter. Are the objects of sense, which form the data of science, psychical or physical ; and, if physical, ex- ternal or internal ? On the one hand, how far is there direct evidence for any of these hypotheses ? On the other hand, how do they stand the indirect test of the facts of science ? That is, can the objects of science as facts of knowledge be explained by any hypothesis of the data of sense ; and can the other hypotheses be eliminated ? Being hypotheses, idealism and realism alike must be treated by the logical rules CHAP. III. THE PHYSICAL DATA OF SENSE 43 of hypothesis. Sensible data must be made to explain the scientific facts, as gethereal undulations have been made to explain luminous facts. We must be on our guard against synthetic hypothesis. Wliat would be thought of a natural philosopher, who dared to start with the hypothesis of emission and denied all the facts of light, which cannot be deduced from the emission of corpuscles by a luminous body ? What, then, shall we think of mental philosophers, who start with the hypothesis of sensations and deny all the insensible world which cannot be deduced from the contempla- tion of sensations by sensation? I admit that there may be direct evidence of an hypothesis. But even so, unless that evidence be mathematical certainty, the hypothesis must also be submitted to the indirect or analytical evidence of explaining the facts. Now it cannot be pretended that the direct evidence of the hypothesis of perceiving sensations or any other hypo- thesis of sensible data is mathematically certain. There- fore all the hypotheses of idealism and realism must pass through the alembic of analysis. The first direct evidence is that of consciousness. Consciousness is the immediate apprehension of oneself performing some operation. Thus I am conscious that I feel, that I perceive through my senses, that I imagine, remember, reason, desire, will, act. Unfor- tunately, however, this operation of apprehending other operations has come to be confused in psychology with the operations themselves. Hamilton, seeing that perception requires an object, and consciousness of perception requires perception, falsely concluded that the consciousness includes the perception of the object, whereas it only requires it as a condition. He com- mitted the common fallacy of confusing a thing with 44 PHYSICAL REALISM part i. its condition. Reull}^ perception is tlie apprehension of the object, consciousness of perception the apprehen- sion that I am apprehending the object. Mill, again, seeing that feeling pleasure and pain are the same as being conscious of feeling them, falsely concluded that every operation is the same as its consciousness. He committed the fallacy of over-generalisation. In feeling pleasure and pain there is no distinction between opera- tion and object, and hence none between feeling and consciousness. But whenever there is a distinction between operation and object, the operation is concerned with the object and the consciousness with the operation. Hence to see white is different from being conscious of seeing white. So with other operations. Eeasoning is a mediate operation from premises to conclusion. The consciousness of reasoning is an immediate apprehension that I am performing that mediate operation. Will is an active operation, the determination to act ; its consciousness an intellectual operation, apprehending that I determine to act. To reason and to will, then, are not the same as being conscious that I reason and will. It is not improbable that the lowest potency of sensi- tive life may have been mere feeling, and the beginning of consciousness mere conscious feeling ; and that as, in the growth of the senses, the operation and the object became distinguished, consciousness became distinct from the operation, the operation being concerned with the object, and the consciousness with that relation of oneself to the object, in which an operation about an object consists. But whatever may have been the genesis of consciousness, its nature consists not in being the sense of objects but the sense of operations. When, as in feeling, there is no distinction between operation CHAP. III. THE PHYSICAL DATA OF SENSE 45 and object, there is none between consciousness and operation. When, as in sensation, there is a distinction between operation and object, the operation is con- cerned with the object, the consciousness with the opera- tion. Not that consciousness has no reference to the object, but only that it is not the apprehension of it. The operation, which is the apprehension of the object, is a certain relation of subject to object : the conscious- ness, which apprehends the operation, is an apprehension not of the object, but of the relation of the subject to the object. For example, I see white, I am conscious that I am seeing white. It was necessary to have thus defined consciousness on account of the mass of confusion and inconsequence imported into psychology b}^ regarding consciousness as identical with all the conscious operations. Hamilton, seeing that consciousness is intuitive, but falsely identi- fying it with the perception of an external world, falsely concludes that perception of an external world is also intuitive. He ought by the same argument to have made reasoning immediate, or else consciousness mediate, either of which alternatives is absurd. Mill, seeing that consciousness is limited to the apprehension of mental operations, and falsely identifying it with the mental operations, falsel}^ concludes that the mental operation of sensation is also limited to the apprehension of mental operations. He might as well have said that will, being identical with its consciousness, is an intel- lectual apprehension of a mental operation. But as will is an active determination to do something, while its consciousness is an intellectual apprehension that one has that active determination, so sensation is an appre- hension of an object, while its consciousness is an apprehension that one is performing that operation. 46 PHYSICAL REALISM part i. Sensation says, ' This is white or sweet ' ; consciousness says, ' I am seeing something white or tasting something sweet.' This being consciousness, one operation of which I am conscious is that I know objects. What knowledge of objects am I conscious of possessing ? In answering this question, it must be remembered that science is a kind of knowledge of which we are conscious. There is an ordinary consciousness and a scientific consciousness. The ordinary man thinks little or nothing about it, but the man of science is conscious that science passes beyond sense into the insensible, and beyond the objects represented by sense into what I have called the im- perceptible world. We are conscious of knowing a sensible, an insensible, and an imperceptible world by natural philosophy. Now, this knowledge does not appear to conscious- ness to apprehend a psychical object. When I reflect on my inferential knowledge of the number of corpuscles in a drop of water, or of the distance of the sun from, the earth, or of the size of the earth ; when, again, I reflect on my indirect perception of a fire, or the waves of the sea; when, finally, I reflect on my sensation of the white object I see or the hot object I feel ; in all three instances, I appear to my consciousness to be apprehending not psychical, but physical facts. The conscious subject maybe psychical, the conscious ojDera- tions may be psychical ; but I am not conscious that the vision of white, or the perception of a fire, or the inference (jf a corpuscle, apprehends a psychical object. So far as 1 am conscious of the sensations of my five senses, a white object in vision, a hot object in touch, a scent in my nostrils, a sound in my ears, a flavour in my mouth, cannot but seem to be apprehended as CHAP. III. THE PHYSICAL DATA OF SENSE 47 physical objects. Consciousness of the apprehension of objects is in favour of reahsm. But when I apprehend the white, the hot, a scent, a sound, even a flavour, I further appear to be appre- hending an object not only physical, but also external to myself. This seemingly conscious aj)pearance is the strong point of intuitive realism, which depends on it to claim an intuition of an external world. Nevertheless, the appearance is a delusion, which we can trace to its source. From my earliest infancy, whenever a sensible effect has been produced in my nervous system, I have been accustomed to infer an external object. By asso- ciation, perhaps also facilitated by evolution, the in- ference has become so automatic as to be unnoticed. The consequence is, I think I am intuitively sensible of the external object when I am really inferring it. Nothing can prevent the delusion. I appear to see the paper and its distance from me. I cannot now consciously disengage the sensation of the sensible object from the inference of the perceptible original. Hence the limits of consciousness as an evidence. Consciousness does not become reflective, and therefore a source of psychology, till many operations have already become automatic in the conscious subject. The process from the sense of the insensible object to the inference of the perceptible original has been re- peated an incalculable number of times before any man is sufficiently adult to consciously reflect on what he has been doing. Accordingly, consciousness is the source ratlier of the nature than of the orii^in of knowledge ; invaluable for what we knovv now, delusive for how we came to know it. 1 am conscious that I somehow apprehend a sensible and an insensible world ; but I am not conscious of the exact point at 48 PHYSICAL REALISM part i. which it ceases to be sensible, and becomes insensible and inferred. Intuitive realists were right in appealing to consciousness for the nature of knowledge ; only they should have appealed from the ordinary to the scientific consciousness. But they were quite wrong in appealing to consciousness for the ultimate origin of knowledge. They said truly, ' I apprehend an external world ' ; they said falsely, ' I apprehend it intuitively.' Nevertheless, the antithesis between the nature and origin of knowledge must not be exaggerated. Con- sciousness tells us somethinoj of the orie neither the external object nor the in- ternal effect in the nervous system, l)ut the internal psychical sensation. If so, realism will have to succumb to idealism. The ([uestion we now have to ask ourselves is not 50 niYSICAL REALISM part i. \vlielher the external object causes our sensation in some way or other. The scientific evidence of the propa- gation of motion from external objects to our bodies and the conscious involuntariness of sensation are suffi-- cient proofs that the external object does cause our sensation. It is, however, a different question how one causes the other. Secondly, the question we now have to ask ourselves is not whether there is any evidence at all that the sensation produced is purely psychical. What is to be said on this point will follow when we come to the Cartesian philosophy in detail. The present questions are, first, whether Ijiology proves that within ourselves nervous and cerebral motion produces a psychical sensation ; secondly, if so, whether it follows that the sensible object also becomes a psychical sensa- tion. The answer is that biologists have gone beyond biology, and that no affirmative answer can be given to these questions from the observations, or direct in- ferences from sense, which are the evidences of their science. In the first place, the nervous system is imperfectly known. It is quite clear that external oljjects propa- gate motions to the nerves, but it is not at all clear what happens when the effect has been produced. In optics, for example, so long as we are reading of the undulations of light, of the manner in which rays are communicated to the eye, of the structure of the lens by which the ra3'S are made to converge on the retina, and of the general structure of the retina, and even of its nervous elements, everything is clear. But the further we penetrate from the retina along the optic nerve to the optic centres at the base of the brain, the darker the subject becomes, and fact seems to pass into hypothesis. It is the same with all our senses. Nay, CHAP. III. THE PHYSICAL DATA OF SENSE 57 difficulties begin at the very terminations of the nerves. What, for example, are the precise functions of the tactile corpuscles, of the rods and cones of the retina, of the rods of Corti in the ear ? We know more of nervous structure than of nervous action. What is nervous action ? This is an unsolved problem. What is cerebral action ? This is a more unsolved problem. The structural connections of afferent nerves with centres, of centres with efferent nerves, of efferent nerves with muscles, and to some extent the structural constituents of nerves and muscles are fairly made out. It is also found that an appre- ciable interval takes place between the stimulation of an afferent nerve and the muscular motion which it indirectly but ultimately produces. This interval proves an important point about nervous action ; it is a motion because it takes time to go from place to place. The genus of nervous action, then, is known to be mo- tion. But what is its differentia ? After the first crude hypothesis of animal spirits moving in the nerves, nervous motion was supposed to be the simplest form of me- chanical motion by impact, as if the impression were pushed along to the brain, as a series of bricks knock one another over. Then it was supposed to be vibra- tion. Later researches tend to show that it has relations to the motions of electricity and of chemical action. It is, no doubt, some molecular motion allied to other motions of the same kind ; but its peculiarity is its slowness, compared, for instance, with electricity. Its precise differentia is at present unknown. Cerebral motion is still more unknown. It has been found, by experimenting on various parts of the brain, that different parts are to some extent connected with different muscular motions, from which it is inferred 58 PHYSICAL REALISM r.virr i. that tlioy are also connected with diilerent nervous motions. lUit liow the brain moves between the stimu- his of an afferent nerve and its effect on an efferent nerve is unknown. lie would l)e a bold man who would come forward and say he knows the motion by which the effect impressed on tlie nerves is communi- cated to the brain and there made ready for sensation. How, then, can he say he knows that cerebral motion, of which in biology he is ignorant, produces a psj^chi- cal sensation, which is beyond the venue of a physical science ? Secondly, the so-called transmutation of cerebral motion into psychical sensation is admitted to be per- formed in some mysterious way, unknown and inex- plicable. This point may be made clear by the following quotation from Professor Huxley's Lay Sermon on Des- cartes' Discourse, in which the Professor is trying to prove that thought is existence, and, so far as we are concerned, existence is thouo-ht : — ' For example, I take up a marble, and I find it to be a red, round, hard, single body. We call the redness, the roundness, the hardness, and the singleness, " quali- ties " of the marble ; and it sounds, at first, the height of absurdity to say that all these qualities are modes of our own consciousness, which cannot even be conceived to exist in the marble. But consider the redness to beat!T i. liypollicsis is rendered most difficult by the pliaiiiomena of rellex action. In rellex action, the afferent and efferent nervous processes are certainly connected with- out any breacli of physical continuity. It might again be objected that only the nerves of reflex processes are continuous. But we cannot divide the nerves of reflex action from those of conscious action, and say that the former nerves are physically continuous, whereas the latter are interrupted l^y purely psychical sensations and volitions, because the very same nerves, which are used in conscious, are used also in reflex actions. For example, we may wink either voluntarily or automati- cally. An object strikes the eye, transmits its motion to the afferent optic nerve, which communicates with the brain, which transmits the motion to the efferent facial nerve, governing the orbicular muscle of the eyelids, which makes them close. The whole of this process often takes place automatically, without any rupture of phy- sical continuity. When it takes place consciously, are we to say that the physical motion, having arrived from the optic nerve to the brain, does not produce the motion of the efferent nerve, but produces a psychical sensation instead, which produces a psychical volition, which at leno'th affects the efferent nerve ? There is not a tittle of biological or any other evidence that the physical continuity is sometimes preserved sometimes broken in ihis manner in the verj^'same series of nerves. To escape this gratuitous hypothesis of psychical interruption, some of the mental physiologists resort to paradoxes, in order at once to preserve the physical continuity of the nervous system, together with purely psychical sensations. Allowing that in all cases the motion of the afferent nerves propagated through the centres produces the motion of the efferent nerves in a CHAP. III. THE PHYSICAL DATA OF SENSE Gl continuous manner, some suppose that, standing quite apart from these physical processes, the conscious sub- ject is a sort of impartial spectator, performing purely psychical operations that have no physical effects, while others positively go the length of supposing tliat not only in sentient beings, but in all nature, there are alwa3's two independent but parallel streams, the well- known physical motions and supposititious psychical processes accompanying them. These hypotheses are exceedingly like the Pre-established Harmony, and like it in being made to get over a self-made difficulty. They are hypotheses to cover an hypothesis. The former alternative does not go beyond conscious beings, but it fails to explain a fact of consciousness far more certain than the li}-pothesis. We are certainly con- scious that external objects somehow affect our feelings and sensations, that our sensations, desires and infer- ences affect our volitions, that our volitions somehow affect the motions of our bodies. It is absurd to suppose that our conscious operations are inert and idle, when they are consciousty both passive and active, and that the conscious subject is like a child, given his opera- tions like a toy to make believe he is very busy, but really to keep him quiet. The latter alternative which carries this inert psychism into everything whatsoever, without any evidence, except the original hypothesis of two parallel streams in a sentient being, would have us believe that the wind blows, the waves swell, the earth moves, with some obscure sentience. Such a per- sonification of nature was excusable in primitive religion, but it is not worthy of modern science. Lastly, to return to the usual hypothesis that nervous motion produces psychical sensation, which again issues in nervous motion, one cannot help asking what can be 02 PHYSICAL REALISM tart t. the source oi" ;i liiological hypothesis so foreign, nay, so contradiclory to the evidence of biology ? Biologists have become psj^chologists, and have fallen under the dominion of tlie idealists. Without any criticism, with- out any biological proof, simply because it is the fashion, and as if it were a first principle, they have accepted the idealistic hypothesis of purely psychical sensation, and thereon have reared an hypothesis of their own, that nervous motion produces this psychical sensation, Mdiich reproduces nervous motion. Now, the present question, as I said before, is not whether there is a purely psychical sensation, but whether there is any evidence that motion propa- gated from tlie afferent nerves to the brain 2)roduces such a tertium quid, instead of producing motion from the brain to the efferent nerves. There is no evidence, either psychological or biological. As a psychologist, I am conscious that I perform the opera- tion of sensation, which for argument's sake may be assumed as purely psychical ; but I am not conscious of my nervous motion. I am not, therefore, conscious of sensation arisimr out of nervous motion. A bioloo:ist, not ill himself but in another body, can observe a nervous system, its physical continuity, and the time of its action proving motion ; Init this dissector cannot either observe or l)e conscious of the sensation of another nervous system ; he cannot, therefore, observe nervous motion issuing in sensation. That there is such a pro- cess from the physical into the psychical and back is sheer ]iy])Otliesis, An arbitrary concordance of idealism and l)iology, Xor is this all ; they proceed to suppose that the effect produced by the external object on the internal nervous system is not yet sensible, but that, when the CHAP. III. THE PHYSICAL DATA OF SENSE Go psycliical sensation is produced, the effect for the first time becomes sensible, so that tlie sensible object is either identical with the sensation, or at all events is equally psycliical. But, in the first place, even if a purely psycliical sensation is produced in this manner, it does not follow that the sensible object becomes psychical. There is no reason, except the old and ex- ploded hypotliesis similia similihiis cognoscuntur, why a psychical operation may not apprehend a physical object. Secondly, whatever may be the nature of the operation, it is most improbable in itself that the hot felt through one's bod}^, the white seen through one's eyes, the loud heard through one's ears, is anything but a physical condition of the tactile, optic and auditory nerves in connection with the brain. The idealistic hypothesis of psychical sensation, tlien,_does not prove the biological hyioothesis of the transmutation of nervous motion into psychical sensation, nor either hypothesis the third hypothesis that the sensible object is psychical. Ter sunt conati imponere Pelio Ossam Scilicet atque Ossse frondosum involvere Olympum. The study of the mental pli}'siology of the present day suggests several reflections. In the first place, the insensible and imperceptible motions of a3tliei", their reflections from other bodies, and their impact on the senses are now well-established discoveries of science. They are known (jualities, which are not sensations, but the insensible causes of sensations. Not all knowable qualities, therefore, are sensations. Secondly, as we recede from the external world Ijehind the periphery into the nervous system, science becomes more vague. What are nervous and cerebral motions ? Thirdl}', we are told that cerebral motion, whicli is physical, pro- duces a heterogeneous sensation, which is psychical. C)i rilVolCAL Ul'Al.IS.M rARX I. I liii we are jjiveii no evidence of this transmutation. We cannot observe it in a dissecting-room. If it be said we are conscious of it, we answer that we are conscious of sensation, but not of cerebral motion, and therefore not of cerebral motion producing psychical sensation as a separate and indeed heterogeneous fact. Fourthly, this transmutation of one unknown into another unknown is admitted to take place in an unknown manner. Fifthlv, we are illo^icallv asked to infer from this trans- mutation of cerebral motion into psychical sensation that the sensible object, e.g. the red seen in vision, is also a psychical sensation. Sixthly, we are not told how, if the object of sense thus becomes psychical, we infer the external causes, which, as we have seen, are nuicli the clearest part of the whole business. Seventhly, we often find that, with more logic than consistency, the external objects which were jDreviously made the scientific causes of sensation are nevertheless afterwards declared unknown and unknowable. Meanwhile, the fallacy of this so-called biology is its assumption of psychological idealism. All that is really proved by natural philosophy is that external redness, for example, is an insensible quality of insensible gather, consisting of a vibration of a certain velocity ; and that, reflected 1)}' an external object, it produces in the optic nerves of a sentient being a sensible redness, whic^li is not iden- tical willi the external vibrations nor itself a sensible vibration at all. The simple conclusion from these scientific facts would be that the nervous effect is the sensible redness, from Avhich, together with sensible motion, the external motions of vibration are inferred. Xotliing more is proved by mental physiology. When we look back at the whole light thrown by natural philosophy on the sensible object, we shall find CHAP. III. THE PHYSICAL DATA OF SENSE 65 that it is known that external jDhysical objects produce internal physical effects in the nervous system, but it is not known that these internal physical effects in their turn produce an internal psychical object of sense. Meanwhile, we are conscious that, when we use our senses, we somehow apprehend a physical object, which seems by an illusion to be also external. The simplest liypothesis, which can be made in these circumstances, is that the sensible object is neither external on the one hand nor psychical on tlie other, but the internal physical effect on the nervous system. In other words, there is a via media between intuitive realism and idealism of all kinds, closer to the scientific facts than either hypothesis ; namely, physical realism. At the same time, scientific observation is not a positive proof of physical realism. It brings the sensible object within the man : it cannot decide whether it is or is not within the soul. Its ultimate result is that the sensible object is not external but internal, not without but within the sentient being, not identical with the physical object in the outside world but produced in the interior microcosm of the animal organism. This negative conclusion eliminates intuitive, but it does not positively establish physical realism. As a direct evidence, natural philosophy, being founded on ol)ser- vation, is able to sliow that the sensible object is not the physical object outside, but is within the iicrxous system ; not being founded on consciousness, it is not able to decide whether this internal sensible object is physical or psychical, whether it is the nervous effect, or something even more internal. It leaves this problem unsolved. Accordingly, there still remain two pos- sible alternatives — physical realism and psychological idealism. F GO PHYSICAL KEALISM tart i. Neverllieless, scieutific observation makes physical realism the more probable alternative, because this hypothesis simply accepts the proved nervous effect as the sensible object, instead of hypothesising a further psychical object, which is unproved, and breaks the nervous continuity. When as a mental philosopher one adds consciousness to scientific observation, the proba- bility of physical realism is increased. Consciousness tells us that we somehow apprehend physical objects, which appear also to be sensibly external. Scientific observation disabuses us of the appearance that the sensible object is external, but not of the consciousness that it is physical. Natural philosophy, as a direct evidence, may be said to remove the physical object of sense from the external to the internal world, but no I'lirllicr lliati ihe nervous system. The most probable mental philosophy would simply conclude that it there becomes sensible — though onl}^ the most probable. We asked for direct evidence that the immediate object, hot, coloured, &c., perceived by our senses is a psychical pha3nomenon, and we find there is none. Con- sciousness is so far from saying so, that it confuses the iimnediate and the mediate, and leads us to think that the immediate object is not only physical but external. Scientific analysis corrects this confusion, and teaches us that tlie innnediate ol)ject is not external but internal, Ijul does not go on lo show that it is not only internal but psychical. I suspect that the idealists by a kind of confusion have changed the trutli that the object of sense is not external but internal into the hypothesis that it is not physical \mi psychical. The idealist may reply that direct evidence is not re(inired for an hypothesis, and that the psychical object i.s like ci3tlier — something inaccessible to direct evidence, CHAr. III. THE PHYSICAL DATA OF SENSE 67 but needed to explain the facts. I accept this issue. I admit that, if the ideahstic hypothesis of the sensible object could explain the facts of the known world and eliminate the hypothesis of physical realism, it would be proved by this indirect evidence. There would still be no direct evidence that a hot or coloured object is not a physical but a psychical fact. But, contrary to all ap- pearance, we should be obliged to conclude that, as light is paradoxically but really an undulation of asther, so is the seen, or felt, or heard, or tasted, or smelt, a psychical, and not a physical, fact. The gist of the idealistic hypothesis is that not some but all the immediate objects are psychical, and that no physical object whatever is apprehended by sense. The consequence is that all our sensitive experience will be limited to psychical objects; for, so far as it is sensitive, experience is merely the sum of our sen- sations. Moreover, the supposition of a priori elements of knowledge will not help us, for nobody pretends that we have an a priori apprehension of the physical to add to an a posteriori apprehension of the psychical : such an hypothesis would be too great an inversion. The consequence is that all the data of our knowledge will be psychical. No doubt different idealists will pro- vide more or less of such psychical data. Some will have merely psychical sensations, others will add a psychical subject, and others again psychical apprehen- sions a priori. But at the widest the data will all be psychical facts of some kind oi- other. Now the question arises, what can be known from psychical data? 11" all the iimuediate objects I touch, see, taste, smell, and hear are psychical, and I am psychi- cal, and all my apprehensions are psychical, if all my sensitive experience is of nothing but psychical phoeno- p 2 08 niYSIOAL REALISM part i. nieiia, if all the data which form the immediate premises of my mediate knowledge are psychical, what can I infer from such facts in the premises? To answer this question we must consult the logical rules of inference. All inference is by similarity. Not to enter into the question whether there is one fundamental type, there are three ap2)arent kinds of inference — induction, deduc- tion, and analogical inference. All these are different modes of reasonimx from similar to similar. In induction we apprehend that similar particulars have a similar characteristic, and infer that the class, including those and all other particulars similar to them, have that similar characteristic. In deduction we start with a proposition stating the similar characteristics of a class, either inferred by induction or otherwise known, as major premise ; we combine it with a minor premise, asserting that something is one of the class of similar particulars ; and from this combination we infer that this new but similar particular has the similar characteristic already known to belonor to the class. In analoi?ical in- ference, which is an imperfect substitute for induction followed by deduction, we apprehend that a particular has a characteristic, or several similar particulars have a similar characteristic; we apprehend by analogy that another particular is similar to the given parti- cular or sinular particulars ; and from the analogy we infer that this new but similar particular may have the characteristic similar to that of the given particular or particulars. Various men are mortal, . • . all men are mortal : all men are mortal, I am a man, . • . I am mortal : the earth is inhabited, Mars is like the earth, . • . Mars may be inhabited : — these inductions, deductions, and analoi:^ical inferences are nothinsf but inferences from, similar to similar. They are founded ciiAr. III. THE THYSICAL DATA OF SENSE G9 also on tlie reality and knowledge of classes and laws. But what is a class except similar things, and what is a law except the fact that similar things possess similar characteristics ? From this limitation of inference to similarity it follows that whatever the character of the data, such will be that which is inferred. If all the data were psychical, then, by parity of reasoning, we could only infer the psychical. If we never had direct experience of anything pli}'sical whatever, then, there being nothing physical in the premises, nothing physical in the con- clusion could possibly be inferred. From the similar the similar is inferred ; from the psychical the psychical. But in order to infer the physical we must have some physical data. The universal similarity between the data in the premises and the inferred in the conclusion requires to be guarded from misapprehension. I said above that the old hypothesis — like is known by like — is a fallacy. I now say that like is known from like. These positions are not inconsistent. The former refers to the relation of subject and object, the latter to the relation of object to object. There is no reason why the object appre- hended should be like the subject apprehending ; but there are reasons why objects inferred should be like the objects from which they are inferred — the rules of logic. If the subject has constantly had physical objects pre- sented to it, it must apprehend them, or be useless. But when the subject has before it the immediate objects which can be presented to it, whether a posteriori or a priori, it has all the data from which reasoning can start ; and if that reasoning is to maiiilaiii tlio rousistoucy of truth, it can add nothing in the conclusion which is not justified by the presence of sometlnng shnilar in I lie 70 rilYSICAL llEALISM part i. preinises. If reasoning contains, on tlie Kantian hypo- thesis, a iJiiori apprehensions, these will be part of the data ; but if it adds anything, not in the data but in the conclusion, which has no analogue in the premises, reasoning becomes paralogism. This fallacy is well known in deduction ; but it is equally true of induction, which only generalises the subjects and predicates con- tained in the particular instances, and of analogical idference, wdiich infers that one particular similar to another may be similar also in a characteristic already apprehended in that other. Therefore, although like objects are not necessarily immediately apprehended by a like subject, only like objects are inferred from like objects, not by any necessity in the relation of subject and object, but by the nature of reasoning. Hence a psychical subject may immediately perceive physical objects ; but if it w^ere a psychical subject and perceived psychical objects it could infer nothing but psychical things, similar either to the psychical subject perceiving or to the psychical objects perceived. Again, the logical canon, like is known from like, must not be confused watli the metaphysical hypothesis, like causes have like effects. Aristotle extended the principle of the propagation of the species from the organic to the inorganic world, and thought that every cause is homogeneous wdth its effect. Modern science has discountenanced this view, except in the far-off sense that all physical causation may be the propagation of motion in various forms. But wdien I say that we can only infer like objects, wdiat I mean is not that we must infer causes like the effects, but causes like the causes which we have already known. For example, Newton, already knowing the effects requiring gravitation to cause them in terrestrial bodies, when he found similar CHAP. iir. THE PHYSICAL DATA OF SENSE 71 effects ill celestial bodies, inferred tliat tlieir cause also is a celestial, similar to terrestrial, gravitation. Now, if all the data of sense were psychical, not only the effects but also the causes in sense would be j)sycliical : conse - quently, when we came to a sensible effect, similar to other sensible effects, l)ut not due to any sensible cause, we should have to infer a similar cause beyond sense ; and, as all the causes in sense would ex hypothesi be psychical, we should have to infer, by parity of rea- soning, a psychical cause, not because the effect was psychical, but because all previously known causes would be psychical. If, on the other hand, there were physical causes in the data of sense, we could then, and only then, infer a similar physical cause beyond sense. Again, when I say that only like objects are inferred from like, I do not mean that nothing new can be inferred, but only nothing new which is not similar to the data. The conclusion is no mere restatement of the premises. What is inferred need not have been already experi- enced, nor is reasoning confined to merely reproducing the immediate data of the senses. But what is inferred must be similar to what has already been experienced. What is new, and has never been, nor ever will be, in experience, such as an a^thereal undulation, can be in- ferred. But the sethereal undulation is a motion similar to the experienced motion of waves of water. Nothing new, which is not similar to the data, can be inferred. It is true of the Deity Himself, who, though not experi- enced, is inferred to be like man, but infinitely intensi- fied in the attributes which we already know in our- selves. Consequently, if all the data were psychical, we should be able to draw inferences to similarly psychical subjects and similarly psychical objects, new but similar to the data. But we should not be able to infer some- 72 PHYSICAL RKALISM paet i. tiling wholly new, dissimilar and heterogeneous, for Avhicli there was no analogue either in the sentient sub- ject or in the sensible objects. Hence, the physical, for Avliich there would be ex hyjxUhesi no analogue in the premises, could not be inferred. If, on the other hand, as I suppose, the sensible data are physical facts in ni}' organism, I can then infer new but similar physical objects outside, although I have never immediately per- ceived them by sense. Another misapprehension will immediately arise. It is said that one opposite implies another, and, therefore, though we experience only one opposite, we infer the other. Thus, it is supposed, from psychical data we infer their opposites, phj^sical things. I am almost ashamed to write down Aristotle's distinction of con- tradictories and contraries ; but it is necessary in an illogical age. Contradictory opposites are the positive and its negative, as relative and not relative, finite and not finite. Contrary opposites are the furthest removed positives, as white and black. Now contradictory op- posites in a sense imply one another, but contrary opposites do not. White implies not white : it does not imply black. We might have apprehended white without having any conception of black, much less having proof of its existence. Secondly, great harm is done by such vague terms as ' imply ' and ' implication,' which some- times mean conceiving and sometimes inferring. The positive, when apprehended, makes us conceive the con- tradictory negative, but does not make us infer that it exists. Are we to fall into the old sophism of arguing that as something is contradicted by nothing, nothing exists ? It is a common argument that the relative which we .experience imphes the non-relative and absolute, CHAP. III. THE PHYSICAL DATA OF SENSE 73 the finite implies the infinite. This is an utter confu- sion of contradictories and contraries. The relative im- plies the not relative ; but the contradictory, not relative, is not necessarily the positive contrary, abso- lute, for it also includes nothing ; and the relative, in implying the not relative, does not decide whether it is absolute or nothing. As white implies not white, but not necessarily black or any other particular colour, so the relative implies not relative, but not necessarily the particular species of not relative, absolute. The same remark applies to the opposition of finite and infinite, except that in this case the term ' infinite ' is ambiguous, being properly the not finite, but including both that which is not finite, because it is nothing, and that which is not finite, because it extends without limit. The finite implies its contradictory, not its contrary : it implies the negative not finite, but does not imply the particular positive species, the infinite which extends without limit. Secondly, the relative and finite imply only in the sense of making us conceive the mere contradictories, not relative and not finite. The positive sides of the contradictions not only leave the content of the negatives undetermined, but also leave the question undecided whether we can infer that there is anything corresponding to the ideas of the negatives. Nor do they even give us the ideas till we have not only apprehended the positives, but also apprehended that they are relative and finite. The relative and the finite, then, when apprehended to be such, make us conceive the ideas of the not relative and not finite, but give us no idea of a positive some- thing absolute and extending without limits, niucli less make us infer that this species of not relative and not finite is something real as distinguished from nothing 71 PHYSICAL REALISM takp i. at all. When we merely experience something which lia})peus to 1)0 finite, we need not think of any opposite ; if we think of it as finite, we mnst have an idea of the not finite ; but we need not form an idea of the positive infinite, much less can we prove that there is something infinite, and say, ' I experience the finite and relative, therefore there is an infinite and absolute.' Men accept such arguments because they think it helps to prove the existence of a Deity. But the fi.nite and relative do not make us conceive a positive infinite absolute, much less infer its existence ; and theology has better argu- ments for a Deity than the confusion of negative and positive, of contradictory and contrary opposition, of conception and inference, of ideas and judgments. Similarly, the ps3^cliical does not imply the physical. The physical and the psychical are contraries, not con- tradictories. The contradictory of the psychical is the not psychical, which may be anything else or nothing. Suppose that I had experienced nothing but jDsychical data. If I had never thought of them as psychical, but only as hot, red, and so on, I should have had no reason to conceive the not psychical. If I had thought of them as psychical, I must then have had the bare idea of not psychical as its contradictory. But I should neither have been able to have inferred that it existed nor what it was. The content of the idea would have been the bare negation or contradictory of the psychical. I should have had no idea of the physical as a positive contrary, much less have proved its existence. Just as the apprehension of white makes me conceive the idea of not white, but does not infer that there is any other colour, much less the contrary black, and just as the apprehension of the relative and finite makes me con- ceive the idea of not relative and not finite, but does not CHAP. III. THE PHYSICAL DATA OF SENSE tO infer that there is anything which is not relative and not finite, much less the contrary absolute and extending witliout limits, so the apprehension of the psychical would make me conceive the idea of not psychical, but would not tell me that there is anything positive which is not psychical, much less that it is the contrary, physical. To infer the existence of the positive con- trary, the physical, I should have required other than psychical data, which would, however, have been ex hypothesi all the data possible. In all cases the existence of a contrary is a matter not of implication in the knowledge of the opposite con- trary, but a matter of independent inference. Human reasoninfir would indeed be easv, if without further question the moment one had ascertained a tiling, one knew that its contrary existed ; when one had experi- enced white, one knew black ; when all ex]Derience had been of the relative and finite, one knew the absolute and infinite ; when all the immediate data of all reason- ing were psychical, one straightway knew that there are physical things. Why, one contrary does not even make us conceive the idea of another, much less infer its existence. The white makes us conceive the idea, not white : we want other evidence to infer the existence of the black. The psychical makes us conceive the idea, not psychical : we want other evidence to prove the existence of the physical. A synthesis from psychical data to physical things must be founded on some better device than the fallacy of the implication of opposites. But in reality the whole liypothesis of such a synthesis is illogical. To infer physical things we require more than psychical data, and their implications, and their consequences : we require physical data in the premises similar to the physical ol)jects in the conclusion. 7('» PHYSICAL REALISxM pakt i. The canons of inference, then, teach us, first, that from siniihirs similars are inferred ; secondly, that what is inferred may be something new so long as it is similar to some of the data ; and thirdly, that it cannot be the contrary of all the data. Therefore, on the idealistic hypothesis that all the data are psychical, in the first place, what is inferred would also be psychical ; secondly, it would include other psychical subjects and other psy- chical objects similar to those which ex hypothesi form the data of inference ; l)ut, thirdly, it would not include physical things, for which there would be no analogy, and which are not implied in merely psychical data : for psychical data would not make us even conceive, much less infer their contraries, physical things. On the other hand, if some of the data are physical, what is inferred can be phj^sical like the data, different yet similar objects, the data being in our own bodies, the inferred objects in the external world. We constantly hear at the present day of two worlds and their correspondence — the psychical and the physical. It is not the purpose of this essay to deny this anti- thesis, nor to depend upon it. But it is also commonly supposed that all the data of our knowledge belong to the former world, from which the latter is inferred. Against this hypothesis I direct this essay. If all the data of sense were psychical, the parity of reasoning would have no data to infer the physical. But the physical world is the object of natural science, which is knowledi?e. Therefore, not all the data of sense are psychical. There must be similar physical data to infer similar physical objects. Such, then, are the data required by the rules of reasoning to infer a physical world. We began by saying that, if the idealistic hypothesis led to the CHAT. III. THE niYSICAL DATA OF SENSE / i only possible explanation of the facts, we must accept it even on this indirect evidence. We now see to what it logically leads. All that is inferred as well as all that is perceived, all that is immediate and all that is mediate, all that is apprehended in ns and all that is known be3"ond, vrill be psychical. That is, all known realities will be psychical facts of some kind or another. As Berkeley says, the whole known world will be mind and ideas ; with Hegel, thonght will be being and beino- will be thouo-ht. These are the logical idealisms. Nothing physical, and not psychical, will be inferrible, still less knowable. This logical consequence of all psychological idealism must be confronted with the discoveries of natural philo- sophy. A survey of these discoveries shows an enormous mass of insensible and inconceivable realities, which are scientifically known by inference from sensible data. But they are physical realities, incapable of being re- solved into any kind of psychical fact ; being insen- sible they are not sensations, being inconceivable they are not ideas. It follows, therefore, that some things physical, and not psychical, are knowable, and not all known objects are psychical. The phvsical objects of scientific knowledge directly eliminate pure idealism. Starting synthetically from the common idealistic hypothesis that the sensible data are psychical, the pure idealist draws the strictly logical conclusion that all known objects, inferred from these psychical data of sense, must also be psychical. Accord- ing 1o him, then, there are no physical objects of know- ledge. His lofific is consistent, but his conclusion is fjilse. He has omilled tlie physical world whicli, being beyond our sensations and ideas, cannot be resolved into sensations or ideas, ])ut which yet is an object of 78 niYSICAL EEALISM p.\rt i. science — the most perfect form of knowledge. Not all known objects, therefore, are psychical; some are phy- sical. Pnre idealism then is false, and some form of realism true. As intuitive realism has already been eliminated by natural philosophy, it onl)^ remains to decide between the hypothetical realism of the cos- mothetic idealist and the physical realism of this essay. The physical objects of scientific knowledge in- directly eliminate cosmothetic idealism with its hypo- thetical realism. The cosmothetic idealist tries to reconcile the idealistic theory, that the sensible data are psychical, with the realistic theory that some objects knowable by inference from these data are physical. We have found that the realistic part of his theory is correct. He has the merit of admittinir that there are physical objects of knowledge : this is his superiority to the pure idealist. He has the merit of admitting that they are not intuitively perceived by sense, but inferred : this is his superiority to the intuitive realist. But he is illogical. His defect is the inconsequence of supposing that physical objects, though not intuitively j)erceived, could be inferred from purely psychical data. But we have seen that all inference is l:»y similarity, and there- fore physical ol)jects could not Ije inferred from purely psychical data. The physical would be the object of a new term in the conclusion, absent and un- justified in the premises. If all the data of sense were psychical, then, by parity of reasoning, all objects knowable from them would be psychical. But by the discoveries of science, and by the admission of the cosmothetic idealist, some objects knowable by inference from the data of sense are physical. Therefore not all the data of sense are psychical. Suhlata consequent tollitur antecedens. CHAr. HI. THE rilYSlCAL DATA OF SENSE 79 Cosmotlietic and pure idealism are mutually destruc- tive of each other. The former admits that some objects are phj^sical, which prove that the latter is wrong in supposing all objects to be psychical. The latter admits that only psychical objects can be inferred from psychi- cal data, so that the former is wrong in supposing that physical objects are inferred from psychical data. Pure idealism fails to recognise, cosmotlietic idealism fails to explain, the knowledge of an insensible and inconceiv- able physical world. If we combine both we destroy the common data of both. As the pure idealist says, if all the data were jDsychical all the objects would be psychical ; but as the cosmotlietic idealist admits, not all the objects are psychical. It follows that both are wrong in saying all the data are psychical. Their data fail to explain the physical objects of scientific know- ledge. Science eliminates all psychological idealism. Meanwhile the physical objects of scientific know- ledge are not merely destructive of psychological idealism, but are also constructive of pliysical realism. They prove in themselves that some objects of know- ledge are physical, and, in combination with the logical rules of inference, that some data of sense must be physical, to infer them. Similars are inferrible only from similars. Therefore the physical is inferrible only from the physical. But some objects of science are physical ; therefore they are inferrible only from physi- cal data. These data of sense, however, though physical, are proved by scientific analysis to be internal ; there- fore the data of sense are physical ol)jects within our nervous system, from which we infer physical objects in the external world. This is the theory of physical realism, established by the logical rules of In'pothesis. I admit that the direct evidences are not a positive 80 niYSICAL REAT,1SM part i. proof of physical realism. Consciousness, alone, is even in favour of intuitive realism. But scientific analysis destroys this hypothesis by separating the sensible effect from the external cause, and showing that the sensible object must be internal. On the other hand, it does not show that the sensible object is not only in- ternal but ps3^cliical, and therefore does not favour idealism. It makes the intermediate theory of physical realism possible, even probable. I do not believe, how- ever, that the data of sense are recoverable by any direct method, because from our very birth, and with inherited power, we overlay them with inferences. Hence the shipwreck of modern philosoph}^ which sup- poses its hypotheses of sensible data to be first principles, and has alternated between the opposite but equally futile attempts to grasp physical things by sense, or to leap from psychical data to physical things. I admit, therefore, that the crucial evidence must be indirect. That hypothesis of the data of sense must be accepted, which explains the knowledge of the objects of science. This insensible, this inconceivable, this physical world of science is not an object of intuition, is not a sum of psychical sensations and ideas, is not inferrible from psychical sensations and ideas. Its knowledge then must be accounted for otherwise. It is inferrible from internal and physical data, the nervous system sensibly affected by external objects. The data of sense, then, are neither physical objects without, which are the causes not the objects of sense ; nor psychical objects within, from which nothing physica could be inferred ; but physical objects within, from which physical objects without are inferred by all, and known by science. Physical realism, therefore, or the theory of internal physical data to infer external physi- CHAP. III. THE THYSICAL DATA OF SENSE 81 cal objects, is, in accordance with the logic of explana- tion and elimination, the only hypothesis of the data of sense sufficient to explain the knowledge of the objects of science. It is a mental philosophy born of natural philosophy, ' that great mother of sciences.' ^ ^ Bacon, Nov. Org. i. 80. G 82 PHYSICAL REALTSM tari r. CHAPTER IV. TlIK IIISTOIMCAL OEIGIN OF PSYCHOLOGICAL IDEALISM. Aristotle remarks that we oiK^it not only to criticise our opponents, but also to point out the causes of tlieir errors. The origin of intuitive reahsni and its presen- tative theory of perception, is the inevitable tendency of oi'dinar}' man to confound sense with reason, and his sensations with liis inferences. He has so loiiix been accustomed Ic^ infer an external world, that at last he cannot but fancy his senses perceive it. He seems to himself even to be conscious that it is so, calls his con- fusion common sense, and at last defies philosophers to distini^uish the sensible and the real. To have dis- abused philosophy of this confusion is one of the many services owed by mankind to Greek philosophers. The distinction of sense and reason soon dawned on the Greeks, and with it the discovery that the object of sense is not the external tliin2f at a distance from our- selves, but some sort of result on our senses, from which the external thino; is inferred bv reason. In short, the Greek philosophers founded the representa tive theory of sensitive perception. But they did not agree al)Out the nature of the sensible object, or repre- sentative of the external thing impressed on the senses. Without pretending to give a history of their views, we may distinguish two great epochs : the first, that in which the sensible object was regarded as a corporeal CHAP. IV. ORIGIN OF rSYCIIOLOGICAL IDEALISM 83 effect ; the second, tliat in wliicli it began to be regarded as an incorporeal essence in onr senses. In this second epoch tlie Greeks prepared the way for the tlieory that the sensible object is an incorporeal idea. But they never actually reached the idealistic theory. The first approach to a scientific theory of the objects of knowledge is to be found in the Atomists, Leucippus and Democritus of Abdera, the pioneers of a sound philosophy of nature. To them we owe the dawn of the truth, afterwards developed into the dis- tinction of primary and secondary qualities, that tlie real and original qualities of particles are figure, position and arrangement, whose different combinations, together with motion, give rise to qualities, such as heat and colour, which, though really derivative, appear equally original to our senses. The manner, however, in wliicli this important doc- trine was presented to the world was not purely unex- ceptionable. The Atomists, it is true, admitted that there is for every variety of sonsil)le qualit}' a distinct mode, or schema in their language, of the original qua- lities ; for example, a sharp taste arises from angular, a sweet from round schemata. Ihit, to say notliing of their crude speculations on corpuscular structure and motion, they fell into tlie fallacy of confusing the deri- vative quality with its sensible effect in the famous dictum, ' Conventionally there is sweet, conventionally bitter, con\-entionally hot, conventionally cold, conven- tionally colour ; l)ut really atoms and void.' ^ From this Atomistic identification of secondary qualities with their sensible effects, assisted by the Heraclitean identity of contraries, it was but a short step to the sceptical theory of Protagoras, that all (pialities are merely the ' Sext. Emp. Adv. Maih. \\\. 135. G 2 84 niYSICAL REALISM pakt i. appearances in our senses, witliout any correspondents in the fluent matter of nature. The Atoniists did not recognise sufficiently, the Scejotics not at all, the fact that derivative or secondary qualities are qualities of external things. There is also a conunon tendency in modern mental philo- sophy to identify secondary qualities v^dth their sen- sible manifestations. But for every sensible quality, which is the product of an external object, there is a distinct quality in the external object. A primary quality is also like the sensible quality. A secondary equality, such as heat or colour, is not, indeed, like the sensible effect, being a mode of a primary quality, such as motion ; but it is a distinct and specific variety of that primary quality ; it is the motion of a different kind of matter, it goes on independently of the sensible effect, and it is a knowable object of science. Thus, it has been discovered in natural philosophy that heat and light are not molar but molecular motions, that they are motions of astlier ; that they are, in rerum natiird, different motions of different leno-ths, the waves of mere heat beinof lono^er than those of li rriuc. iv. 203 CHAP. V. DESCARTES 139 no primar}' data to infer bodies— not even one's own body, nineli less other bodies, and their corpuscles, whose structures and motions cause sensible effects in one's own body. But, as Descartes admitted^, bodies are known and inferred from sensible data. Therefore the data cannot be soul and ideas. From similars dis- similars cannot be inferred. From soul and ideas, no- thinjT else follows. But somethini]^ else is known to science ; therefore, not from soul and ideas. Physical bodies and corpuscles, structures and motions, require physical data of sense. After the dogmatism of mediseval philosophy, Des- cartes was rio^ht to doubt. He was riojlit also in begin- ning with the certain fact of consciousness ; I think, therefore am. But, at the same time, he forgot that there are other facts of consciousness. There is a universal consciousness of the thinking subject, but there is also a scientific consciousness that the thinkin<]j subject knows jDliysical objects. Instead of this, Des- cartes substituted the hypothesis that the thinking sub- ject is a soul which perceives ideas, and then, in defiance of logic, attempted a synthetical deduction from this idealistic hypothesis of psychical data of sense to a real- istic knowledge of physical objects of science. The de- duction may be attacked both by enstasis and elenchus ; in its premises and in its conclusion. On the one hand, the subject is not purely psychical, and, if it was, would not be limited to j^sychical data : on the other hand, if the data were psychical, we could not infer physical objects of science, which are admitted by Descartes, and are more certain than any hypothesis of the nature of the subject and its data. Hence the hypothesis of soul and ideas must be surrendered, because the thinking subject -is not the soul but the man, because sensible Vi^YCllOlAK'-iC'W' fl'I'wM-ISM I'AfiT II. r>lH<'''tH :\yc iiol i(l<';is IhiI |)Ii\'; i<';iI (■i]cc\:: on I lie ncrvoiiH Kyslciii, ;iii(| \iic;\MH('. Howl ;in'l I'Ic'is would nol, cikiMc iii.'iii I') iiifcr pli\: i'-;il ()\t'\cc\H oi' yc'\ci\c('. I )cMr,,'i,ri(;H, tlic ori'Mii;il j'cfiiii.s (;!' jno(l<::a\HU> iiior;il);i,r, il)if)ii(; v.'ifiis nicflit.'ilioiiiUiis |)l;i,ci(riKHiiiif', VM,r';i,- l);iiii. 1 '\ liiH HccliiKioii III ;i, Im»I. loom is ;iii ;i(liiiif;i,blo vv.'i.y ol' dislillin;.'- l,lioiin|||„s, |»rovi(l'(l only llicHf! v;i,|)oiir8 of llic lic'ilcd l)i;iiti <",\.\\ ])(; coiidciiscij inlo ;j, kiiowhidgo (>r lli<' (»iil:,idc world. ' IjIhh. !" iindcrslauding are ideas. Yet this hypothesis in one form or other lias i-ciiinincd c\cv sinceLocke's time as the putative priiu'i])lc of all ideaUsm. Many a ])liilosoj)her, wlio lias wiili I,ockc rcco\"crcd from I lie Cartesian hypothesis that the subject, is soul, and lias followed llnmc in coircctincf Locke's confnsiou of sensations and ideas, nevertheless clings to llic liypo- ' Essdi/, 1. 1, 2. 142 r.SYCIlULOGlCAL IDEALISM tart ir. thesis that all immediate objects are some psychical state or other, without any evidence, whether of Cartesian deductions, or of psychological consciousness, or of natural science. Locke, having begun at a new" beginning, pro- ceeds to his method, wdiich is as synthetical as that of Descartes : — ' I shall pursue this following method. ' First, I shall inquire into the original of those ideas, notions, or whatever else you please to call them, which a man observes, and is conscious to himself he has in his mind ; and the ways wdiereby the understanding comes to be furnished w4th them. ' Secondly, I shall endeavour to show wdiat knoiv- ledge the understanding hath by those ideas, and the certainty, evidence, and extent of it. ' Thirdly, I shall make some inquiry into the nature and grounds of faith or opinio7i, whereby I mean that assent which w-e give to any proposition as true, of wdiose truth yet we have no certain knowledge. And here we shall have occasion to examine the reasons and de^Tces of assent.' ^ From this passage we can see how vain is psycho- logical synthesis. The smallest mistake at the beginning vitiates the wdiole procedure and every consequence. A man is here said to be conscious of having ideas in his mind. It is true that he is conscious of havinof ideas. But even tlie followers of Locke himself would deny that this is all he is conscious of, Hume would say that he is also conscious of impressions, and Mill would add judgments. Yet to a philosoj)hical use of the syn- thetic method by Locke it w^as necessary that ideas should be all the materials of knowledge ; for the next question 1 Easay, I. 1, 3. CHAP. Yi. LOCKE 143 is — what knowledge can be gained by ideas; wliicli is a false issue, if ideas are not tlie wliole material of knowledge. But as they are not the whole, it is not to be wondered at that, in the sequel, Locke oscillates between two contrary tendencies, a logical but false reduction of knowledge to ideas, and an illogical but true extension of it to things beyond. Moreover, to inconsequence he adds inconsistency. He tries to begin with an understandincf of ideas and end with a know- ledfje of thin stance to which it can be attributed, is also necessarily 150 PSYCHOLOGICAL IDEALISM part ii. present ;' ^ and he had apphed this theory both to soul and body. Locke developed this hint into a formal theory that we perceive the simple ideas of qualities, while 'we accustom ourselves to suppose some sub- stratum, wherein they do subsist and from which they do result, which, therefore, we call substance! ^ This theory he applied to body and spirit ; and from him has de- scended the ordinary hypothesis that the objects of 'sense and consciousness are qualities, while substance is inferred — without data to infer it. This error will meet us again in this chapter. At present it will be sufficient to quote a passage from another part of Locke's Essay : ' Our simple ideas have all abstract as well as concrete names : the one whereof is (to speak the language of grammarians) a substan- tive, the other an adjective ; as whiteness, white ; sweetness, sweet.' ^ This is the well-known logical dis- tinction of abstract and concrete, but its consequences are often overlooked. Locke, for instance, forgot to ask in which meaning he should call a simple idea an object of sense. The abstract whiteness is a quality ; the concrete white is the qualified. Now, nobody ev^er saw whiteness ; the object of vision is the white, the red, &c. Similarly, the object of taste is not sweetness, but the sweet ; and so on with all sensible objects. Universally, then, an object of sense is never a quality, but always the qualified ; and a quality is an abstrac- tion ; and, though we may sometimes speak of perceiving it, we do so only for convenience. But the qualified is a substance ; whiteness and sweetness are qualities, but the white and the sweet are substances. The object of sense, therefore, is always a substance. 1 do not mean that sense perceives a whole substance at once, but only 1 Princ. i. 52. ^ Essay, II. 23, 1. ^ III. 8, 2. CHAP. VI. LOCKE 151 SO far as it is sensible to a given sense ; sight perceives a substance so far as it is white ; taste perceives a sub- stance so far as it is sweet, and so on. Nor do I mean an external substance, for I am a substance, consisting, too, of an immense plurality of substances, which I per- ceive so far as they are sensibly affected. These conclusions apply both to outer and inner sense. In sensation, I perceive not a mere quality, nor a whole substance at once, nor an external substance ; I perceive my nervous system, not so far as it is ner- vous structure moving, but so far as it is sensibly affected in different parts, the optic nerve so far as it is visibly white, the gustatory nerve so far as it is sweet to taste, and so on. Similarly in consciousness, I perceive, not mere thinking, nor the whole of myself, but myself thinking, in the manner described in the last chapter. The object of my sensation is myself as a physical sub- stance sensibly affected ; the object of my consciousness is myself as a thinking substance. Descartes rightly said, ' I think.' He ought not to have deserted this prin- ciple. Locke ought to have returned to it, and have applied it from consciousness to sensation. Modern philosophy ought now to give up the sensation of qualities and inference of substance, because there is a direct sensation of my nervous system sensibly affected, and a direct consciousness of myself thinking, both of which are senses not of qualities, but of the qualified. We have a sense of substances, in order to infer them. Locke's complete theory is that all sense perceives a simple idea. Eeally, sense always perceives a sub- stance qualified. It is doubtful whether the substance, as perceived, is ever simply qualified ; for instance, even when I feel simply pained, I doubt whether I do not feel pained for a time. But, in any case, I do not Lj2 rSYCTIOLOGICAL idealism part ii. perceive aiiytliing simple in the sense of a simple quality, wliicli is only simple in tlie sense of abstract ; but I perceive at least tlie simply qualified. Secondly, I do not perceive anything simple in the sense of a simple idea, which is really conceived, not perceived ; but I perceive, in sensation, my nervous system sensibly affected, and in reflection, myself thinking. The object of sensation, and the object of consciousness, so far from being simple ideas, are not ideas at all. They are two sets of materials of knowledge, of which neither is a quality, and neither is an idea, but each a substance. Locke's attempt to make the origin of ideas determine the origin of knowledge breaks down at the very outset by substituting abstractions for con- crete data of sense. At the end of what he has to say on simple ideas,^ Locke comes to the operations which he supposes to make other ideas out of them, and to the ideas thus made.^ ' The acts of the mind,' says he, ' wherein it exerts its power over its simple ideas, are chiefly these three : First, combining several simple ideas into one compound one, and thus all complex ideas are made. The second, is bringing two ideas, whether simple or complex, together, and setting them by one another, so as to take a view of them at once, without uniting them into one, by which way it gets all its ideas of relations. The third, is separat- ing them from all other ideas that accompany them in their real existence. This is called abstraction, and thus all its general ideas are made.'^ He then re- marks that ideas, made up of several simple ones put together, he calls complex ; such as are beauty, grati- tude, a man, an army, the universe. Next he divides complex ideas under three heads : modes, substances, ^ Essay, II. 2-11. -' II. 11 scq. to the end of the Third Book. ' II. 12, 1. CHAP. VI. LOCKE 153 relations. Complex ideas of modes are ideas of affec- tions of substances, subdivided by liim into simple, or combinations of tlie same simple idea, e.g. a dozen, formed of units, and mixed, or combinations of simple ideas of several kinds, e.g. beauty, theft. Complex ideas of substances are ' such combinations of simple ideas as are taken to represent distinct particular things subsisting by themselves, in which the supposed, or confused idea of substance, such as it is, is alwa}-s the first and chief ; ' ^ they are subdivided into ideas of single substances, e.g. a man, and collective ideas of several substances, e.g. an army. ' The last sort of complex ideas,' he says, ' is that we call relative, which consists in the consideration, and comparing one idea with another,' ^ e.g. father and son, bigger and less, cause and effect.^ The consideration of all these com- plex ideas in their order occupies the remainder of the Second Book ; while that of abstract ideas follows, along with general words, in a general treatment of language in the Third Book.^ The whole discussion is full of variety. But it is vitiated by two incurable errors. In the first place, the objects of knowledge are complicated with their mere ideas. But many scientific objects are known to exist, without being conceivable. Secondly, no thorough analysis is attempted of the three acts of mind, which are supposed to be the sole causes capable of producing out of simple ideas all other ideas. Locke calls them composition, comparison and abstraction ; ^ making the first to be the origin of all complex ideas of modes and substances, the second the origin of all complex ideas of relations, the third the origin of all general ideas. ' Essay, II. 12, G. ^ II. 12, 7. ^ II. 25, 2. ' Cf. II. 33, 19. ' II. 11. 154 rSYCHOLOGICAL IDEALISM part n. He saw the foundation of these operations on sense ; but he forgot to ask their rehition to reason. After sense, we conceive particular ideas in the reproductive imagination, and general ideas by abstrac- tion from sense. It does not follow that all general ideas are thus formed ; on the contrary, it is impossible that the idea of an insensible object should be either reproduced or abstracted from sense, in which it has never been. Again, we may compare and compound ideas. But at the same time we also judge about sensible objects and apprehend their relations. In judgment we use ideas, particular and general. ^ But, as Mill has pointed out,^ we also judge about sensible objects in order to apprehend their relations. I am in pain ; this is a judgment that I, who am real, am in pain, which is real. Now, reasoning starts from such judgments about the relations of sensible objects, and sometimes by analogy, sometimes and better by induction and deduc- tion, infers rational judgments, no longer about simple objects, nor about ideas, but about the relations of real objects ; on the principle, if the premises are true, the conclusion is also true. That is, starting from judgments of sense, we infer rational judgments on evi- dence about relations, as real as the sensible relations. Kor is this all ; as I showed in the last chapter, reason, having from sensitive concluded rational judgments, forms indirect ideas, roughly corresponding to the objects inferred, like to the ideas of sensible objects but not the same, and only capable of being made by reason. For instance, reason, having inferred that there are particles in bodies, causes the idea of a corpuscle ; a general idea of corpuscles, which is not a result of mere abstraction, and particular ideas of this or that cor- ^ Mill, Logic, i. 5, 1. CHAP. TI. LOCKE 155 piiscle, Avliieli are not results of composition and com- parison of ideas, but of inference from judgment to judgment. Beyond sense and imagination, besides composition, comparison and abstraction of ideas, there are also judgments of sense about the relations of sen- sible objects, and reasoning from these judgments to the relations of insensible objects, producing rational conceptions of ideas, due to no other source but reason- ing. The narrow problem of the origin of ideas cannot be separated from the whole problem of judgment, reasoning, and the origin of knowledge. Locke, in the Second and Third Books, saw only one side of thinkinc^, and that its weakest side : imagination and abstraction, comparison and com- position, of ideas from sense. Eational inference of realities, beyond sense and ideas, he allowed to fade into the distance of the Fourth Book. Consequently, he found only the direct sources of ideas, and missed their indirect source in reason. No doubt he was in- fluenced by the Cartesian logic of his day, which knew only the order — idea, judgment, reason. But there is a second order — reason, judgment, idea. As soon as judgment begins to act on the senses, reason begins with it, and, never stopping except to sleep and rise again refreshed, constantly forms new judgments issuing in new ideas. But Locke postponed reasoning, ignored rational conception, and therefore always fell short even of the origin of ideas. Even in the ideas of simple modes, the very simplest department of complex ideas, this defect is noticeable. After sensations of motion, we may form ideas of motion by imagination ; and the ideas of simple modes of sensible motion by composition.^ l)ut reason also ' Essay, II. 18, 1-2, loC) . PSYCHOLOGICAL IDEALISM part it. infers simple modes of insensible motion in nature, such as electricity and magnetism, cohesion and chemi- cal attraction, which were never in sense, and frames indirect ideas of these motions. Similarly, we may imagine ideas of sensible duration and extension, and compound ideas of these simple modes ; but when Locke goes on to suppose that the mind extends itself to infinity simply by repeating these ideas, he neglects the rational evidences of the unbounded nature of time and space. Unless men had thought they had reason to infer infinity, no mere repetition of ideas of the finite would ever have given the idea of the infinite, which is always accompanied by a rational inference that the in- finite itself is be3^ond any idea we can possibly form of it. The mischievous consequences of omitting reason in the formation of ideas are best seen in Locke's doctrine of mixed modes and relations. Without reasoning, mere composition and comparison, as soon as they go beyond sense, would produce at most artificial ideas, the va- garies of imagination. Consequently, it is not sur- prising that Locke treats the ideas of mixed modes and relations, which he supposes to be formed by pure com- position and comparison from and beyond sense, as artificial, and even goes so far as to contend that not merely the ideas, but mixed modes and relations them- selves, have no other reality but what they have in the minds of men, and are real only in the sense of being consistent, not in the sense of representing real things. This paradox is a serious matter, for it affects the reality not only of a mixed mode, such as beauty, or a rela- tion, such as father and son, but all moral modes and relations. It reduces morality itself to an idea.^ 1 Cf. Essay, II. 22, 2 ; II. 25 ; II. 30, 4 5 ; II. 32, 10 ; III. 4, 2 ; III. 5. CHAP. VI. LOCKE 157 But obligation is a mixed mode, wliicli is real ; theft, drunkemiess, lying, are mixed modes wliicli are only too real, and tlie conformity of morality to law is a rela- tion, which is also real, though perhaps less common ; and the complex ideas of these mixed modes and relations are not artificial, but really, though inadequately, corre- spond to real morality and immorality. We may admit that morality is not altogether immutable ; it is not therefore unreal. We may admit that the ideas of the beautiful, of the good, and of law, are difTerently com- pounded in ancient and modern morals ; they are not therefore artificial. We may admit that actions of virtue are uncommon ; but virtue is not an idea. By reasoning, man finds out the moral relations suited partly to humanity in general, and partly to the cir- cumstances of his time. By rational conception, he apprehends ideas of moral relations, immutable and mutable. Happy he who can also realise these ideas, and be Virtutis verse custos rigidusque satelles. There is even a certain fashion of ideas, wliicli Locke illustrates by the Greek idea of ostracism and the Eoman idea of proscription. But these ideas were not on that account artificial : they represented real mixed modes at Greece and Eome : to be ostracised or pro- scribed was anything but a mere idea. The Greeks and Eomans inferred that these institutions would serve certain purposes, and thus both established the real mixed modes and represented them by corresponding ideas. The modern historian from his evidence hifers that these mixed modes existed in the past, and con- ceives the ideas in the present. Similarly, the relation of paternity is not the idea of that relation, nor a mere product of comparison. It is a real relation of generation. 158 PSYCHOLOGICAL IDEALISM part ii. wliicli from sensible data we infer really to take place, and of wliicli we afterwards form an idea, rational and by no means artificial, tliougli but superficially represent- ing the actual physical process of propagation. Mixed modes and relations, and their ideas beyond sense, are not always artificial constructions of composition and comparison of sensible ideas ; but reasoning from judg- ments of sense discovers real mixed modes and relations, and then forms indirect ideas, really, though inade- quately, corresponding to these realities, in science, in art, and in morals. The fallacy of omitting reason again appears in Locke's treatment of universals in the Third Book. He thinks that the sole source of general ideas is direct abstraction from sense. The consequences he draws are that all classes are abstract ideas, that no real essence is knowable beyond ideas, that simple ideas are unde- finable, and that universal truths are merely the agree- ments and disagreements of our abstract ideas. ^ All these consequences would follow if we had no higher power than abstracting general ideas from particular sensible objects. All classification would be artificial. But there is a second source of general ideas. Eeason, by discovering the numerous similarities of particulars, infers real kinds or natural classes, which are not indeed eternal but as constant as the similarities, and thereby causes new, general, often very indirect ideas repre- senting these real classes, but not identical with them ; e.g. the rational general idea of a corpuscle. Again, a simple idea of sensible light is undefinable ; but hght in the universe is not, as Locke thinks, undefinable. On the contrary, optical reasoning proves that the real essence or fundamental similarity on which its pro- I Essay, IV. 3, 31 ; IV. 12, 7. CHAP. VI. LOCKE 1-39 perties depend is an ethereal undulation, and defines it accordingly. Lastly, whatever we may think of essences and definitions, if Locke's theory that direct abstraction is the sole source of general ideas, and that classes are abstract ideas, were true, it would follow that all uniformities would be universal relations of abstract ideas ; and he accepted the consequence ; even the variety of Locke's mind refusing to entertain a con- ceptualisra of classes along with a realism of natural laws. If ships and liquids were abstract ideas, the laws of flotation would be universal relations of abstract ideas. These laws, however, are universal relations of real ships and real liquids, inferred by reason. Therefore the classes so related are realities beyond abstract ideas. Abstraction of ideas from sense is not the sole source of generality, as Locke thought : reason infers natural classes and laws, and indirectly produces general ideas, not identical with them, but representing them, not arti- ficially but really, though inadequately. Curiously enough, Locke himself saw, through a glass darkly, the interference of reason in the origin of one complex idea, that of substance. If sense perceived simple ideas of qualities, and composition united simple into complex ideas, the only complex ideas we could have would be complex ideas of qualities. We might have, for example, a complex idea of a combina- tion of extension, solidity, motion, thinking, and no- thing more. But Locke saw that we have somethiuQ- more. He, therefore, suddenly introduced, beyond sense and over and above composition, a supposition ; and says that ' not imagining how these simple ideas can exist by themselves we accustom ourselves to suppose some suhstratum, Mdierein they do subsist and from which they do result ; which, therefore, IGO rSYCIIOLOGICAL IDEALISM paet ii. we call substance.' ^ Secondly, he allowed tliat this supposition causes an obscure and confused idea of the supposed but unknown support of qualities. He re- coo-nised two such supposed and conceived substances : body, the substratum to those simple ideas we have from without ; and spirit, the substratum to those we liave from within.'-^ Finally, he regarded both these substances as unknown, and neither of their ideas as clear and distinct. Nevertheless, he thought that the ideas of substance were real in a different way from those of other complex ideas. The complex ideas of mixed modes and relations were, according to him, real if con- sistent ; those of substances real only if agreeing with things without us.^ It is the supposition of existence, over and above the composition of ideas, which made him allow this .agreement with existence to ideas of substances. Inconsistent as this supposition is with his general theory of the composition of complex ideas, it is nevertheless the truth, though in a very imperfect shape. Let us then proceed to correct it, by showing what is the real nature of this inference, which Locke calls a supposition. It is true that external substances are inferred. But there are three views of what a substance is inferred to be. Some say that it is only a combination of qualities. But qualities are abstractions ; and a body is not ex- tension, solidity, motion, or any number of further abstractions, combined, but the extended, solid, moving, &c. Locke went to the opposite extreme of supposing a substance to be a substratum or kind of support on which the qualities rest, and this is the ordinary view, descended indeed from the compound, or 'concrete,' substance of Aristotle, composed of matter and form. 1 Essaij, II. 23, 1. - See II. 23, 1-5. ' II. 30, 4-5. CHAP. vi. ■ LOCKE 161 But here are two abstractions, the subject abstracted from the quaUties and the quahties from the subject. If a body ceased to be extended, sohd and moving, it would cease to be ; there would be no substratum or support left. Hence the third view, that a substance is a qualified subject, the extended, solid, moving, &c. ; in which the qualities are nothing except as characterising the subject, and the subject nothing except as charac- terised by the qualities ; from which subject or sub- stratum, qualities or attributes are opposite abstractions. Secondly, external substances must be inferred from similar data. To infer qualified subjects beyond sense, there must be qualified subjects in sense. If the data were ideas, we could onlv infer other ideas. If the data were qualities, we could only infer qualities. A fortiori, if tlie data were ideas of qualities we could never infer a real qualified subject, for which there would be no analogue. Therefore, again we find that Locke's sensible data were false. He thought that by sense we perceive simple ideas of extension, resistance or solidity, motion, &c., and then without rhyme or reason suppose something totally different, a real sup- port in the external world. Eeally, sense perceives qualified subjects, the extended, resisting, moving, &c. within ; hence reason infers similar extended, resisting, moving, qualified subjects without. It must not be forgotten that muscular sense was not noticed in Locke's day ; but the logic of reason had been known since Aristotle's day, and he ought not to have neglected it. Thirdly, substances are not unknown : they are the only things that are known. Everything else is real, and is known, only so far as it belongs to substance ; and although cjualities are abstracted and spoken of as real and known for mere convenience, what is really M 102 I'SYCIIOLOGICAL IDEALISM part ii. known in mathematics is not tlie quality of extension, but the extended ; in physics, not the quahty of gravity, but the gravitating ; in morals, not the quality of good- ness, but the good. Substances would be unknown, and uninferred, on Locke's data. But substances are known, because sense perceives them within, and reason infers them without, by parity of reasoning. They are the data and conclusions of all our knowledge. Sensation perceives the nervous system in different parts as sensibly white, sweet, extended, moving, &c. Eeason infers similar physical substances or bodies. Science goes on to infer similar corpuscles. Nor does it stop till it infers the body of the universe. Consciousness perceives myself as thinking subject, partly body, partly soul. Eeason, from the signs of bodily organs, language, actions, and productions of others, infers similar thinking subjects. Natural theology, not from bodily organs, but from physical creations, infers God, not as a body, but as a Creator. All this is knowledge of substance, logically inferred from sensation and consciousness ; and only because the objects of outer and inner sense are sub- stances, can reason logically infer substances, physical and psychical. It does not follow, however, that reason is infallible : it is fallible so far as not logical from sense. Nor does it follow that we know substance completely. We begin with sense, and perceive subjects only as sensibly qualified. Eeason reveals subjects insensibly qualified. But we never know the whole of any sub- stance whatever, not even ourselves, not even a crystal which we seem to see through and through. This imperfection of human knowledge misleads philosophers into ag-nosticism. But the truth is, sense and reason enable us to know substances not wholly but partially. rinalh% the knowledge of substance creates the idea CHAr. yi. LOCKE 163 of it. The original ideas are derived from my own sub- stance. From myself as sensible I derive my idea of a physical subject ; from myself as conscious, my idea of a thinking subject, partly physical, partly psychi- cal ; from both, my idea, of a qualified subject. But my ideas of all other known subjects are results of reasoning, which first infers similar subjects, and then forms ideas of them. Ideas of substance are right, so far as they correspond to really known substances sensible and inferred, and their correctness varies in accordance with sense and reason. They are clear, distinct, and adequate, in proportion partly to their proximity to sense, and partly to the extent of reasoning about any given substance ; but they are seldom or never adequate to what is known of a substance. Locke, though inconsistent, was justified in allowing that the complex ideas of substances are not due to mere composition of simple ideas ; and he ought to have made the same admission in the case of other ideas, because not all ideas of mixed modes are due to composition, nor all ideas of relations to comparison, nor all general ideas to abstraction. He was justified in allowing that we infer substance, in order to conceive the idea of it, beyond ourselves. He was justified in allowing that ideas of substances are right, so far as they represent real objects. But he was unable to found a philosophy of substance, because, in the first place, he failed to apprehend that sensation and reflec- tion both perceive substances within ; secondly, he was accordingly, but falsely, constrained to reduce the in- ference of substances without to a mere supposition — a supposition without any data, illogical, and impossible to reason ; thirdly, he had to call all substances, all qualified subjects, the only things in the world we M 2 164 PSYCHOLOGICAL IDEALISM tart ii. know, unkiiowu ; and call ideas of substances obscure and confused, when really the clearest and distinctest ideas we have are those of stones, waters, houses, plants, animals, cats, dogs, men and other substances. There are man}^ sources of ideas. Sensation and reflection are not directly concerned with ideas, as Locke thought, but with sensible objects. But after sense, reproductive imagination without reasoning con- ceives particular ideas of the objects of sense, memory refers the ideas to their objects, and abstraction con- ceives general ideas of the objects of sense. Eeasoning infers insensible objects and forms their ideas. There is a rational imagination of ideas. Eational ideas of known objects are not artificial. Locke partly saw this in the case of substance. But the ideas of modes and relations are also rational and correct, so far as they agree with modes and relations properly inferred as belonging to external substances. While, however, rational ideas of the insensible are not artificial, they are often inade- quate ; e.g. of a corpuscle, of infinite space and time, of gravitation, of the universe, of God. Lastly, the inventive imagination makes artificial ideas, such as those of a centaur, a fairy, ' The Iliad,' ' A Midsummer Night's Dream.' But it has never yet been successfully analysed. Perhaps even the comparison and composi- tion of artistic imagination are founded on reasoning, not to the actual and real, but to the possible and ideal. Let us now suppose that Locke's general account of the origin of ideas is immaculate and superior to our objections, that sensation and reflection perceive simple ideas ; that comparison, composition and abstraction are the three acts which form compound ideas ; and that the introduction of a supposition of substance was a momentary lapse of a philosopher from the consis- CHAP. VI. LOCKE 165 tency of pliilosopliy. What will be tlie consequence ? As he says himself, ideas will be the instruments and materials of our knowledge.^ Then, by parity of reason- incf, all that we can know from such materials will be other ideas, and, as he has said himself, ideas will be also all the objects of our understanding.^ Locke you would imagine to be the founder of pure idealism. We should have expected him to go on to show that every- thina: in the world of science is an idea. At the end we should have been inclined to say — There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy. But Locke had a various, thous^h not a loorical mind. He was a student of Descartes ; he was also imbued with the English devotion to nature. From the former source he derived the theory of ideas, from the latter the reality of things. Locke, after assuming that all objects of understanding are ideas, admitted that ex- ternal realities exist. The Essay contains an undercur- rent of ontology, which comes up first in the famous distinction of primary and secondary qualities,^ recog- nising external qualities as real, as external causes of our ideas of sensation, and even as externally related as cause and effect to each other : — ' The qualities then that are in bodies, rightly con- sidered, are of three sorts. ' First, the bulk, figure, number, situation, and motion or rest of their solid parts ; those are in them, whether we perceive them or no ; and when they are of that size, that we can discover them, we have by these an idea of the thing, as it is in itself; as is plain in artificial things : these I call primary qualities. 1 Essaij, II. 33, 19. ' I. 1, 8. ^ II. 8. 20G PSYCHOLOGICAL IDEALISM pakt ii. ' Secondly, the jwwer that is in any body, by reason of its insensible primary qualities, to operate after a peculiar manner on any of our senses, and thereby pro- duce in us the different ideas of several colours, sounds, smells, tastes, &c. These are usually called sensible qualities. ' Thirdly, the power that is in any body, by reason of the particular constitution of its primary qualities, to make such a change in the hulk, figure, texture, and motion of another body, as to make it operate on our senses differently from what it did before. Thus the sun has a power to make wax white, and fire to make lead fluid. These are usually called powers.' ^ The same undercurrent of ontology reappears in the admission of substances, and real essences, though unknown. It becomes most marked in the Fourth Book, where Locke adds to all his other entities, one's own existence, the existence of God, and the existence of other things, such as the clippings of our beards and the parings of our nails. Finally it springs up into an elaborate picture of the insensible universe beyond the reach of our ideas.^ It is a dangerous thing to be an unconscious metaphysician. Locke's metaphysical theory of existence is quite outside his psychological theory of ideas. How does it agree with his logical theory of knowledge ? If it be true to say, that beyond ideas there is an external world of qualities, real and causal, real substances and real essences, my own ex- istence, God's existence, the existence of bodies, and of insensible corpuscles, what is truly said by a philoso- pher, who is after all but human, must be known to a man. What then does Locke, the philosopher who says all this, say about the knowledge of man ? ' Essay, II- 8, 23. ' IV. 3, 24. CHAP. YI. LOCKE 167 The Fourtli Book, wliich is on knowledge and opinion, starts with a theory quite consistent with the previous Books, on the origin of ideas : — ' Since the mind, in all its thoughts and reasonings, hath no other immediate object than its own ideas which it alone does or can contemplate, it is evident that our knowledge is only conversant about 'em. ' Knowledge then seems to me to be nothing but the perception of the connection and agreement, or disagree- ment and repugnajicy of any of our ideas. In this alone it consists.' ^ Locke proceeds to divide knowledge into intuition and reasoning. He says that ' sometimes the mind per- ceives the agreement or disagreement of two ideas immediately by themselves without the intervention of any others : and this, I think, we may call intuitive knowledge.' '^ He adds that ' when the mind cannot so bring its ideas together, as by their immediate com- parison, and as it were juxtaposition, or application one to another, to perceive their agreement or disagree- ment, it is fain, by the intervention of other ideas (one or more, as it happens), to discover the agreement or disagreement, which it searches : and this is what we call Reasoning.' ^ Afterwards, he writes a whole chapter ^ on Eeason, in which he again defines it as the percep- tion of the agreement or disagreement of ideas by intermediate ideas. At the same time he rejects the syllogism, although the process wliich combines two extremes by the intervention of a middle is clearly the same process as his own. But the main point to be observed is that, according to him, reasoning begins with an intuitive perception of the relation of ideas 1 IV. 1, 1-2. ^ IV. 2, 1. 3 IV. 2, 2. * IV. 17. 1G8 rSYCHOLOGICAL IDEALISM part ii. and ends Avitli a mediate perception of tlie relations of ideas. A theory of reasoning such as this must con- fine all reasoned knowledge, and therefore all science, to relations of ideas. This actually is his view of mathematics and morals. ' I doubt not,' he says, ' but it will be easily granted, that the knowledge we have of mathematical truths is not only certain, but real know- ledge ; and not the bare empty vision of vain insignifi- cant chimeras of the brain : and yet, if we will consider, we shall find that it is only of our own ideas.' ^ He says the same of moral knowledge, which he also holds to be as certain as mathematics,^ I admit that if all objects of reasoning are ideas, mathematical knowledge is only of our ideas. But, in this case, it is not of the bulk, figure, number, structure and motion of bodies and particles, Mdiich Locke himself recognises beyond our ideas. Sir Isaac Newton, then, must have been wrong in saying that all the particles of matter gravi- tate to one another with a force varying inversely to the square of the distance ; for he was pretending to a mathematical knowledge of the motions of particles beyond ideas. What a curious contretemps., that in 1687 Newton should discover to mankind the Mathe- matical Principles of Natural Philosophy in every particle of matter, and in 1690 Locke should publish an Essay concerning Human Understanding to prove that the knowledge of mathematical truths is only of our own ideas ! We are relieved from further criticism of this pure idealism, however logical, because Locke himself deserts it for realism, however hypothetical. At first he delibe- rately confines all knowledge to the perception of the re- » Essmj, IV. 4, 6. - IV. 4, 7. CHAP. VI. LOCKE 1G9 lations of ideas, and throughout applies these limits strictly to mathematics and morals. But all of a sudden he in- troduces us to a knowledsfe of real thino-s in other de- partments of knowledge, and, as it were, writes a second essay on another human understanding. The manner in which he makes this abrupt transition is highly instruc- tive. Having defined knowledge to be only conversant about ideas, and to be nothing but the perception of the aofreement and disao^reement of ideas,^ he reduces these agreements and disagreements of ideas to four sorts — identity or diversity, relation, coexistence, and real existence.^ The knowledge of the first three sorts proceeds consistently enough, when suddenly, without any previous prej^aration, much less argument, he lays down the following dogma : — ' Fourthly. The fourth and last sort is that of actual real existence agreeing to any idea! ^ On his original hypothesis that ideas are all the objects of understanding, on his theory of the origin of ideas, in the Second Book, on his definition of know- ledge in the ver}^ same chapter of the Fourth Book, he ought to have said, the knowledge of the idea of actual real existence agreeing to any idea. But just as Des- cartes passed from the idea of God's existence to His existence, so Locke passed from the knowledge of the idea of existence to the knowledge of existence agreeing to any idea. But while Descartes had been inconse- quent, Locke to inconsequence added inconsistency ; he had begun by saying that all objects of understanding are ideas ; he afterwards admitted a knowledge of ' exist- ence agreeing to any idea.' He afterwards divides this knowledge of existence into three departments — an intuitive knowledge of our ' IV. 1, 1-2. ^ IV. 1, 3. s IV. 1, 7. 170 PSYCHOLOGICAL IDEALISM taiit it. own existence, a demonstnitive knowledge of the exist- ence of a God, a sensitive knowledge of objects present to the senses,^ — and devotes a chapter to each.^ In Locke's philosophy, all three ought to have been knowledges of ideas ; they are knowledges of the real and actual existence of things. Again, the Fourth Book presents us with two theories of a proposition to support this inconsistency. First, he divides propositions into two kinds ; mental, wherein ideas, and verbal, wherein words, the signs of our ideas, are put together.^ Afterwards, he says that there are tw^o sorts of propositions ; one, con- cerning the existence of anything answerable to an idea, and the other, concerninsj the aofreement or disao;ree- ment of our abstract ideas.* I am not referring to all these places to criticise Locke for inconsistency, which is a weakness of human nature, a weakness even of philosophers, who are but men, and an amiable weak- ness, because one of tw^o contradictories must be true. My object is rather to show^ that Locke at last came to the truth, that not all objects of knowledge, of j)roposi- tions, of understanding are ideas. But there is a further question. How do we know these actual existences ? or, to use Locke's owni phrase, ' How shall the mind, when it perceives nothing but its own ideas, know that they agree with things themselves ? ' ^ The intuitive knowledge of our own existence is settled in a single section, short but significant, in which he gives up his original theory that we perceive nothing but ideas : — ' As for our oiim existence, we perceive it so plainly, and so certainly, that it neither needs, nor is capable of any proof. For nothing can be more evident to us than ' Essay, IV. 3, 21 ; IV. 9, 2. "" IV. 9-11. * IV. 5, 5. * IV. 11, 13. ^ IV. 4, 3. CHAP. VI. LOCKE 171 our own existence. I think, I reason, I feel pleasure or pain : can any of these be more evident to me than my own existence ? If I doubt of all other things, that very doubt makes me perceive my own existence, and will not suffer me to doubt of that. For if I know I feel pain, it is evident I have as certain perception of my own existence as of the existence of the pain I feel : or if I know I doubt, I have as certain perception of the existence of the thing doubtincr as of that thouo-ht which I call doubt. Experience then convinces us that ice have an intuitive knowledge of our own existence, and an internal infallible perception that we are. In every act of sensation, reasoning or thinking, we are conscious to ourselves of our own being ; and, in this matter, come not short of the highest degree of certainty.'' ^ This passage breathes the very spirit of Descartes. Cogito, ergo sum. I am conscious that I am a thinking subject. This is the fact that never ought to have been deserted. Descartes deserted it for an inference of substance, and Locke followed him out of the right path, but he had to come back to it after all. Consciousness reveals to me not thoughts but a thinker. This con- sciousness is indeed inconsistent with the previous state- ments of Locke ; first, that reflection perceives the ideas of operations, whcli is two removes from consciousness ; secondly, that there is a sup])osition of a substance as unknown substratum to those operations, wdiich would be a baseless inference from data containing nothing but ideas of operations. Nevertheless, the direct conscious- ness of our existence is the fact. How then is it that it is constantly disappearing out of philosophy, not only in the seventeenth, but also in the succeeding centuries ? Because philosophers are perpetually confusing abstract ' IV. 9, 3. 172 PSYCHOLOGICAL IDEALISM part ii. and concrete, forgetting that thoughts are abstract quahties but the thinker the real being, and thus concludincf that consciousness and reflection reveal thoughts, leaving the subject to inference and supposi- tion, when really consciousness and reflection tell me that I am a thinking subject, from which I infer other thinking subjects. Unfortunately, in another part of the Essay, Locke had exaggerated the truth, I am conscious that I am a person, a . thinking intelligent being, into the falsity, I am that very consciousness.^ But in the first place, I am conscious that I perform numerous operations besides the operation of being conscious, that I am a sensible, remembering, reasoning, desiring, willing sub- ject ; consciousness therefore itself tells me that I am more than itself. Secondly, it is not my only source of information about myself. I am conscious that I am partly body thinking, but I also indirectly observe my body. I reason from my consciousness and observa- tions, and infer that I am a permanent substance, when I am asleep as well as when I am awake, when I am conscious and when I am unconscious. Thirdly, consciousness is interrupted ; if I were consciousness I should have an intermittent existence. Finally, Locke has confused the causa cognoscendi with the causa essendi. Consciousness is necessary to tell me, I am a person ; but it does not make me a person ; this am I made by being a permanent substance, partly body and partly soul, capable, when awake, of reasoning, and therefore of the status of a rational being. At the end of Butler's ' Analogy,' the Dissertation on Personal Identity contains an excellent statement of its relation to consciousness, as follows : — ' Essay, II. 27, 9 seq. CHAP. VI. LOCKE 173 ' But tlioiigli consciousness of what is past does thus ascertain our personal identity to ourselves, yet to say that it makes personal identity, or is necessary to our being the same persons, is to say that a person has not existed a single moment, nor done one action, but what he can remember, indeed none but what he reflects upon. And one should really think it self-evident that consciousness of personal identity presupposes, and therefore cannot constitute, personal identity ; any more than knowledge, in any other case, can constitute truth, which it presupposes.' Locke, then, is right in saying that consciousness is an intuitive knowledge of oneself, wrong in saying that it is oneself. Not from the false identification of self and consciousness, but from the consciousness of self, that is, from the intuitive knowledge we have of our own existence, as cogitative beings, Locke deduces our knowledge of the existence of a God by an argument, which is an extension of the third argument in the ' Principia Philosophise ' of Descartes.^ A finite thinking subject requires an infinite thinking subject to create it. Yes, but this argument holds only if we are conscious of ourselves as thinking subjects. God is not an idea, and consequently cannot be inferred from mere ideas. Thus, if Locke had clung to his ideas of reflection, he could not have proved a God : the consciousness, not of mere thoughts, but of a think- ing subject, is necessary to natural theology. Simi- larly, it is necessary to infer any other thinking subject but myself. If, then, I were conscious only of ideas of operations, and even if I were conscious directly of operations, I could not infer thinking subjects, and I could not infer God. The object of consciousness, there- • IV. 10 ; cf. Descartes, Princ. i. 20. 174 rSYCIIOLOGICAL IDEALISM part ii. fore, is not oparations, still less tlieir ideas, but tliiiikini]^ subjects. Here agaiu, too, we find that not all objects, and not all data, of understanding are ideas. Locke was obliged to surrender his theory of ideas in order to prove his own existence, the existence of others, the existence of God. Next, we come to what Locke calls our sensitive knowledge of objects presented to our senses. Here, with Cartesian inconsequence, he tried to maintain his theory of ideas, and yet show how we know external realities, or originals, by inference. Li the Fourth Book he returns to this point again and again. He begins by proposing this problem. 'There can be nothing more certain,' he says, ' than that the idea we receive from an external object is in our minds. But whether there be any thing more than barely that idea in our minds, whether we can thence infer the existence of any thing without us, which corresponds to that idea^ is that, whereof some men think there may be a question made ; because men may have such ideas in their minds, when no such thing exists, no such objects affect their senses.' ^ He answers the question by saying that a man is conscious of a different perception when he looks on the sun by day and thinks on it by inght,and concludes that this is a knowledge not intuitive nor demonstrative, but sensitive. Again, he divides the problem by simple ideas and complex ideas of sub- stance ; and argues that, in the first place, simple ideas, which the mind can by no means make to itself, must necessarily be the product of things operating on the mind in a natural way, and that the idea of whiteness in the mind answers that power which is in any body to produce it there ; ^ and, in the second place, the reality of our 1 Essay, IV. 2, 14. ~ IV. 4, 4. CHAP. VI. LOCKE 175 knowledge of substances is founded on our complex ideas of them being such as are made up of such simple ones as have been discovered to coexist in nature/ rinally, he devotes to the knowledge of objects without us a chapter,^ in which he contends that its certainty is as great as we are capable of concerning the existence of anything but oneself and God, and that it deserves the name of knowledge. He adds four arguments to the preceding : first, that those who want the organs of sense want the ideas of that sense ; secondly, that some- times I cannot avoid the having those ideas produced in my mind ; thirdly, that many of these ideas are pro- duced with pain, which afterwards we remember with- out offence ; fourthly, that our senses in many cases bear witness to the truth of each other's report. Finally, he falls back on the practical argument that we have at all events a knowledge of the external world by the happiness and misery we receive from it. The whole of these arguments are summed up in this one : I have ideas of sensation, which I do not produce myself ; I infer that they are produced by external bodies. It is the Cartesian argument from the passivity or involun- tariness of sensations and ideas. Locke's admission of the reality and knowledge of external bodies is light and honest, but completely destructive of his original h3'pothesis of the objects and data of understanding. It is true, as he admits, that we know external bodies. But this admission de- stroys his original doctrine that knowledge is always concerned with ideas. Again, it is true, as he admits, that we know bodies by inference. But this destroys his doctrine that reasonino- bef^ins and ends willi ideas. Botli admissions also destroy his original doctrine that ' IV. 4, 12. "- IV. 11. 170 PSYCHOLOGICAL IDEALISM part ii. ideas are all the objects of understanding. It is also true, as lie says, that we infer external bodies from the passivity of sensation. But is it true that we could have drawn this inference from sensible data, if sensa- tion had been a perception of nothing but ideas ? This is what Locke makes no attempt to prove. It is con- tradictory to his own logic. Like Descartes, he recog- nised that real truth is the agreement of our propo- sitions with external reality.^ But unlike Descartes, he has given up any special criteria of truth. The vera- city of God he uses only for revelation ; "^ and regards the inherent clearness and distinctness of ideas not as positive criteria, but only as conditions of truth. ^ The consequence is that he has no organon except the rules of reasoning ; and he is aware that, as the data of reasoning are, according to him, ideas with their agree- ment and disagreement, so the conclusions are logically confined to the agreement and disagreement of ideas. ^^ Yet he expects us also to believe that reasoning starting with ideas of sensation can be logically extended to ex- ternal bodies. All logic demands that, as are the data, so are the conclusions. I find that some of the sensible objects I perceive are passive. I have a right to infer some other cause. But I must by parity of reasoning infer a cause similar to those already known. Now, what data does Locke supply me ? Granting him every advantage and all his inconsistencies, I should have ideas of sensa- tion and reflection, and compound ideas from the Second Book : from the Fourth Book, I should have conscious- ness of myself, and a demonstration of other thinking subjects, and of God. These, ex hypotltesi, are all the data, ' Essay, IV. 5. ^ IV. 16, 14. 3 IV. 2, 15. " IV. 17. CHAP. VI. LOCKE 177 direct and indirect, at tlie very best. Wliat would be the logical inference ? I could infer, from the passivity of sense, that it resulted either from other ideas, or from other thinking subjects, or from God. I could not, being without bodily data, infer that it resulted from external bodies. Locke saw the importance of the passivity of sense, but forgot the rules of logic. Newton and Locke were contemporaries. What, then, was Locke's attitude to natural philosophy ? He recognised its discoveries, and especially the corpus- cular philosoj)liy revived by Bacon, developed by Des- cartes, and brought to its perfection by Newton. We have followed him in his ' little excursion into natural philosophy ' ^ to distinguish primary and secondary qualities. He there admits the existence of corpuscles, real qualities, primary and secondary, though insensible, and real powers between qualities, e.g. the power of fire to make lead fluid. There is no fault to find here except with his definition of a quality as ' a power to produce any idea in our mind.' "^ A quality is really a characteristic of a subject or substance. It has various powers, and among them the occasional power of affect- ing our senses. For instance, motion is a characteristic of every corpuscle, and has a power of affecting every other corpuscle, and sometimes of affecting human senses in the way of sensible motion, light, heat, sound, and so forth. But to define it by its sensible power, would be to convert a very occasional accident into the essence of motion, forgetting that there are myriads and millions of motions which come nowhere near the earth, much less man, and are not powers of producing any ideas in his mind. Locke defined quality by a separaljle accident. ' 11. 8, 22. 2 II. 8, 8. N 178 rSYCIlOlAHIlCAL IDllAhlt^M i'aki ii. IKmu'o alsi^ a mistake" In his ilcfiiiifu)!! oi' a socoiulary (|iiality as a power of au insensibU' primary (pialily to prodiu'o in our senses a sensible idea. This is only au oecasional i\\\d aeeidental [lower ; and a seeoudary (piahty is a speeitie niodifieatiou (W a j)riniary ([uahty, Avhieh exists Avhether it prodnees a sensible elleet or not. Thus heat is a moth' of motion transterred iVom star to star, and bi't'ore the oriuiu oi' animals nuu'h ot' it was exhausted without haN'in^ tlie power of ])roduc- iuiX sensible heat \\\\\\ these eorreetions, Locke ex- presses the seientilie distiuetiou ol" primary anil second- ary qualities in the uuivtM'se. lie I'uUv reeoi^uises the existence ot" thai part oi" insensible nature, whii'li I have called the imperceptible, to distinguish it t"rom the in- sensible but interentially perceptible originals of sensible objects. Tie recognises corpuscles as well as masses, the ]iarticles ol" this paper as Avell as the paper. Hut when he came to give these imperceptible cor- puscles a pku'c in the human understanding, he began to vacillate. In tlu> Fourth J3ook, lu^ distinguishes knowledge and opinion, as respectively the perception and the presumption ot" agreements and disagreements ot" ideas, as certain and probable. Strictly, he could put natural pliilosophy in neither, because he admitted that it was not about ideas, but things. Ihit tlu^ alternative to which he leaned was to draw the line between know- ledge and opinion, exactly between the pa])er and its particles, between the mass and the corpuscle, between the perceptible and the impcrce[)(ible ; and. tlierelore, to call the Ihst interences l"roni sense knowledge, and the subsequent interences of science opinion. On the whole, according to him, knowledge' includes mathematics and morals because tliev are about ideas, knowledge of self ' Essex I/, IV. 3, 5 ; IV. 10, 6 ; IV. 11. i» ; 1\. H. n>. or A p. VI. LOCKE 179 because it is intuition, knowledge of God because it is demonstration from this intuition, and knowledge of ex- ternal originals directly inferred from sense : here ends knowledge. In opinion falls natural philosophy. Why? Because the further from sense the less, he thought, our knowledge. Because we are not capable of the ideas of things so remote and minute, and this defect, as he thought, keeps us in ignorance of the things. Because we merely make experiments which are not science Because we can only guess and probably conjecture, use hypothesis and analogy. ' Analogy,' says he, ' in these matters, is the oidy help we have, and 'tis from that alone we draw all our grounds of probability. Thus observing that the bare rubbing of two bodies violently one upon another, produces heat and very often fire itself, we have reason to think that what we call heat and fire consists in a violent agitation of the imper- ceptible minute parts of the burning matter : observing likewise that the different refractions of pellucid bodies produce in our eyes the different appearances of several colours ; and also that the different ranging and laying the superficial parts of several bodies, as of velvet, watered silk, &c., does the like, we think it probable tliat the colour and shining of bodies, is in them nothing but the different arrangement and refraction of their minute and sensible parts.' ^ But knowledge of these insensible qualities he denies. He doubts ' that how far soever human industry may advance useful and experimental philosophy in physical tilings, scientifical will still be out of our reach ; ' ^ and he suspects that 'natural philosopliy is not capable of being made a science.' ^ Yet this very Locke winds up his Essay by " IV. IG, 12 ; cf. IV. 3, 10 ; IV. 3, '24 end ; IV. G; IV. 12, 9 13. - IV. 3, 2G. => IV. 12, 10. N 2 180 PSYCnOLOGICAL IDEALISM part it. a triple division of science, one of M^iicli is Physics or Natural Philosophy, the knowledge of things.^ It is a matter of deep regret that Locke should have written thus of natural philosophy in the very time of Newton. There is some truth in what he says, but marred by exaggeration. There is a huge abyss of ignorance, but it is not altogether an incurable igno- rance. Much of what is called science is opinion, but fresh evidences convert opinion into science. Because there are probabilities in natural philosophy, it does not follow that there is nothing certain. We cannot have a perfect knowledge of nature, but we can know some- thing without knowing everything. We cannot always discover real essence, but there is a knowledge of co- existences and causes, of the conservation and correlation of physical forces, as in electricity and magnetism, with- out always knowing their essences. Locke rightly saw that there is more of the universe unknown than known, and much which is only opined ; but he lost sight of the main fabric of science. By the mere elimination of chance such a concatenation of laws cannot but be true. Locke was ignorant of the logic of science. The two greatest men of science in his own country were Bacon and Newton, of whom the former had shown that there is an experimental science of nature, the latter that natural science is capable of physical deduc- tions from mathematical principles. But Locke, like Hobbes, was silent about Baconian induction, and oblivious to ever3^thing except the old method of intui- tion and demonstration, Mdiicli suits mathematics, but not the whole of natural philosopll3^ Everything out- side demonstration, he calls hypothesis and analog}^. He did not recognise the variety of method, the ana- 1 Essay, IV. 21. CHAP. VI. LOCKE 181 logia demonstrationum 'pro natura sifhjecti, desiderated by Bacon. He did not see that the corpuscuhir philosophy is made independent of tliis liypothesis and that analogy, by many different evidences in many different departments — gravity, light, heat, sound, elec- tricity, magnetism, chemical attraction, nervous and muscular motion — all of which point to corpuscles, their motions, according to Newton's laws, their modifications constituting secondary qualities, their convertibility and indestructibility as motion. He did not recognise that there is a circumstantial evidence, which in law is sufficient to hang a man, in nature sufficient to prove a fact ; and an approximate certainty, by accumulation of evidence, ever indefinitely approaching absolute necessity. But his greatest, though characteristic, blunder was his attempt to carry inference beyond sense to the ex- ternal original inferentially perceptible and then stop short ; to allow us to know the paper and not the par- ticle, the mass and not the molecule. Such a logic is arbitrary. If insensible modes of jjriniary qualities are truly said to be, as Locke allows, then they are knowable. The same laws of reasoning which enable us to infer from sensible effects an external cause, en- able us from that cause to infer another cause, and so on till we have completely explained facts of sense by laws of science. If it were not so, how could science correct ordinary knowledge ? Ordinary knowledge infers an external object, like in secondary as well as primary qualities. Science declares that the external world is like in primary but not in secondary qualities to the sensible effect. But if the former is knowledge and the latter opinion, by the first principle of method ordinary knowledge, as more certain, is to be preferred to the less 182 PSYCHOLOGICAL IDEALISM part it. certain science ; so that the ordinary man is right in his theory of external Ught and heat, and the natural philosopher wrong ! Locke's line between knowledge and science gives the ordinary man, with his inference of bodies, knowledge, but the scientific man, with his inference of corpuscles, opinion. He elevates ordinary above scientific knowledge, which is absurd. There is a standino- difference between natural and mental philosophy, and Locke has done much to pro- duce it. He would make theology and morals not only sciences, which they are, but more scientific than natural philosophy, and tells man, whose real function is to know all and do all, that his proper business is his moral duties and his future state. ^ Newton had just written the ' Optics ' and the ' Principia,' but Locke's theory of science would reduce these works to mere opinions. The whole history of science is against him. On the foundation of Newton's mechanics of motion has been gradually reared a system of science which has eventually revealed to us the insensible and imperceptible causes of our sensations in the external world. On the other side stand the mental philosophers, philosophmites secundum sensum, considering primarily their sensations and ideas, and with difficulty extending their thoughts even to the external originals, then gazing stupidly at the perceptible world, and never dreaming that they have to explain the knowledge of imperceptible nature. Locke's hypothesis that we have a sensitive knowledge from ideas of objects presented to sense, a mathematical and moral science of ideas, and an uncertain opinion of the physical universe, undervalues natural philosophy. It immediately produced the false attitude of Berkeley and Hume towards nature, but it has affected the whole ' Essay, IV. 12, 11. CHAP. VI. LOCKE 183 course of mental pliilosopliy, wliicli lias unduly neglected the problem of knowledge, presented to it by natural pliilosopliers. Hence, while natural philosophy has shown that the insensible is the causa essendi of the sen- sible, mental philosophy has never yet shown how the sensible is the causa cognoscendi of the insensible. But let us suppose that the whole fabric of science is opinion, the whole imperceptible world unknown. Yet it is at least an object of understanding and reason- ing, because, as Locke himself says, ' not but that it is the nature of the understanding constantly to close with the more probaljle side,' ^ and, as he admits, reason may end either in certainty or in probability, either by demonstration or an argumentum ad judicium} This being so, imperceptible probabilities are objects of understanding and reason, but are not all ideas ; there- fore not all objects of understanding and reason are ideas. Nor could they be reasoned from ideas as their data. This want of consequence brings us to another defect in Locke's theory of primary and secondary qualities ; his false view of their sensible aspect. In his opinion, as external they are powers, as sensible they are ideas. But they are neither mere powers nor mere ideas. If, as sensible, they were ideas, we could not logi- cally infer insensible j)rimary qualities, which are ad- mitted not to be ideas, yet inferrible. Therefore, even as sensible, primary and secondary qualities are not ideas, but physical qualities in sense, from which to infer physical qualities beyond. So universally, the inference of imperceptible corpuscles with real qualities and powers beyond sense, even if only probable, could not be drawn from mere ideas of sensation. The natural » IV. 20, 12. ^ IV. 17. 184 rSYCIIOLOGICAL IDEALISM part ii. philosophy of tlie physical world, whether it be know- ledije or opinion, demands physical data of sense. How came Locke, having said that ' whatsoever the mind perceives in itself or is the immediate object of percej)tion, thought, or understanding, that I call idea,' ^ immediately to conclude real primary qualities of matter ? Through the Cartesian habit of surreptitiously passing from the idea to the thing, and his own supposi- tion of a bastard sensation of the thing. His one argu- ment for the reality of primary qualities is that they are ' such as sense constantly finds in every particle of matter, which has bulk enough to be perceived.' ^ But according to him sense is of ideas. All then he could consistently say would have been that primary qualities are such as sense constantly finds in the idea of every particle of the idea of matter, which has the idea of bulk enough to be perceived. But this consistency with his hypothesis would not have proved the fact of the material reality of primary qualities beyond ideas. At the same time, his lapse into a direct sense of matter is of interest, because it is a distinct anticipation of intuitive realism. It exhibits the constant tendency of the philosopher to relapse into the ordinary man, and to fancy he directly perceives the external thing, or, using the inaccurate ter- minology of modern psychology, after contending that what we are conscious of is subjective affections, to sup- pose a consciousness of objective existence. As Locke tried to bridge over the gulf from ideas of sensation to qualities by a kind of bastard sensation of qualities, so his modern followers try to bridge the gulf from subjective affections of consciousness to objective exist- ence by an undefinable consciousness of objective exist- ence. But it is certain that sensation perceives not the 1 Essay, II. 8, 8. ^ n g, 9. CHAP. VI. LOCKE 185 external thing, but its internal effect ; and the only way in which we can reach external qualities of things is not by sense but by inference from adequate internal data, which cannot be mere ideas, nor any psychical states of subjective consciousness. The ' Essay concerning Human Understanding ' begins by assuming that all objects of understanding, as well as all data of sense, are ideas : it ends by ad- mitting that things beyond ideas are objects of under- standing, reasoning, science. The end is better than the beginnincf, tliou£fh the conclusion does not follow from the premises. External bodies are properly in- ferred by ordinary men, as Locke admitted ; and imperceptible corpuscles and their qualities are known, with more certainty than he admitted, by men of science. Therefore, in the first place, not all objects of under- standing, reasoning, science, are ideas. Secondly, the data of sense are neither ideas of sensation nor external qualities of matter, but internal effects on the nervous system, sensibly qualified as extended, moving, hot, coloured, and by other primary and secondary qualities. From internal, ordinary knowledge infers external, sub- stances. From these again science, correcting ordinary knowledge, infers imperceptible corpuscles, qualities primary and secondary as the modifications of primary powers exerted between those corpuscles, and powers of affecting our senses. Locke's ' Essay ' throughout, to make it thoroughly correct, consistent, and consequent, would need two fundamental alterations : — 1. Some objects of understanding are physical things. 2. Some data of sensation are physical effects on the nervous system. 186 PSYCHOLOGICAL IDEALISM part it. CHAPTER YII. BERKELEY. The two pliilosopliers liitherto discussed assumed liypotlieses, but admitted facts, and tried to explain them. Descartes assumed that ideas are the data of sense, Lut admitted the knowledge of physical objects, and broke down on the inconsequence of reasoning from psychical data in the premises to physical objects in the conclusion. Locke made the same assumption, the same admission, and the same failure. But he went further into hypothesis, and to inconsequence added inconsistency. He assumed that ideas are not only all the data but also all the objects of understand- ing, and then admitted that physical objects are also objects of understanding. The admission is true, and therefore, while it contradicted, also destroyed the double hypothesis. We now come to a philosopher who, accepting the whole ideal I13 pothesis, consist- ently denied facts Berkeley assumed, with Descartes, that ideas are the data, and with Locke, that they are the objects, of human knowledge, and consistently, but falsely, deduced man's ignorance of a pli3^sical world. The 'Principles of Human Knowledge,' after an Introduction on Abstract Ideas, begin in the following manner : — ' It is evident to any one who takes a survey of the objects of human knowledge, that they are either ideas CHAP. VII. BERKELEY 187 actually iinprinted on tlie senses, or else such as are perceived by attending to the passions and operations of the mind, or lastly, ideas formed by help of memory and imagination, either compounding, dividing, or barely representing those originally perceived in the aforesaid ways. By sight I have the ideas of light and colours with their several degrees and variations. By touch I perceive, for example, hard and soft, heat and cold, motion and resistance, and of all these more or less either as to quantity or degree. Smelling furnishes me with odours, the palate with tastes, and hearing- conveys sounds to the mind in all their variety of tone and composition. And as several of these are observed to accompany each other, they come to be marked by one name, and so to be reputed as one thing. Thus, for example, a certain colour, taste, smell, figure and consistence having been observed to go together, are accounted one distinct thing, signified by the name " apple." Other collections of ideas constitute a stone, a tree, a book, and the like sensible things ; which, as they are pleasing or disagreeable, excite the passions of love, hatred, joy, grief, and so forth.' ^ Here are most of the errors in the Second and Third Books of Locke's Essay accepted as principles. With- out proof, ideas alone are supposed to be perceived ; ideas of qualities without a qualified subject, and ideas of operations without a thinking subject. Eeason- ing from the data of sense to their causes is entirely postponed in favour of representing, compounding and dividing ideas. Ideas, simple or complex, are consist- ently declared to be all the oljjects of human knowledge. But these so-called principles are mere hypotheses. There is not one word of proof that either the data or ' Princ. i. 188 PSYCHOLOGICAL IDEALISM part ii. the objects of liumaii knowledge are ideas. Locke, not human nature — and not even tlie whole of Locke — was the oracle of Berkeley. Berkeley, however, being a less various but a more logical thinker than Locke, was truer to the data of his predecessor. Locke, as we found, having assigned comparison, composition and abstraction as the three acts, wliicli form new ideas from sense, suddenly, and without any justification, introduced a fourth act of supposition, which is a kind of reasoning, to account for our idea of substance. Berkeley avoided the after- thought, and, at the same time, the truth, that reason does intervene in the formation of ideas from sense. Adhering to Locke's first thoughts, he perceived that what his predecessor had allowed about other complex ideas equally applied to complex ideas of substances. If we start from ideas of sensation, such as those of colour, taste, smell, figure and consistence, and merely compound these ideas, we can construct a collection of ideas and account it one distinct thing, called an apple ; but we cannot, without introducing a qualified physical substance into sense, and restoring its privileges to reason, either perceive or infer an external physical substance. Berkeley thus reduces Locke to logic ; nor has mental philosophy ever recovered this purely hjqDO- thetical theory of substance. Berkeley also made an important correction in one of Locke's three acts, abstraction. Locke had supposed that we can form a perfectly abstract idea of a triangle, which is ' neither equilateral, equicrural, nor scalenon, but all and none of these at once.' ^ Berkeley devoted the Litroduction of the ' Principles ' to a criticism of this modern conceptualism, and founded modern nominalism. ' Essmj, IV. 7, 9. CHAP. Til. BERKELEY 189 He denied that he could abstract or conceive separately quahties which cannot exist separately, or form a general notion in Locke's sense. ^ He admitted that he could consider a figure merely as triangular, without attending to its particular qualities, but not form an abstract general inconsistent idea of a triangle.^ Simi- larly, Hume afterwards said, that all general ideas are nothing but particular ones annexed to general terms. ^ The essential truth at the bottom of this theory is that abstraction is only a kind of attention. But, as often happens, one extreme view begets another. We cannot rise to a purely abstract idea, nor need we fall to a purely particular idea ; we cannot form an idea of triangle in general, nor need we think of a single triangle. We can frame a general idea of a miscella- neous assemblage of similar individuals.^ Secondly, the point about classes is, not what we conceive, but what we infer and know. But, while correcting Locke's exaggeration of abstraction, Berkeley left its independence of reasoning. The consequence is that, according to him, the limit of generalisation would be some single simple idea or some single collection of simple ideas of sense viewed generally. This narrow- ness pervades his whole philosophy. There is, indeed, such a simple abstraction of ideas from sense, as we ad- mitted in the last chapter. But reason, at the same time, starts from sense and first infers classes of in- sensible objects, and then constructs general ideas of them in the rational imagination. Finally, this rational imagination of general ideas accompanies a rational abstraction ; like direct abstraction, attention, but atten- tion to objects of reason. We can abstract, in the sense ' Princ. Introduction, x. - Id. xvi. 3 Treatise, ii. § 7. ^ Cf. Mill, Logic, iv. 2, 1. 100 PSYCHOLOGICAL IDEALISM tart ii. of attending to, an insensible object, not apart from the qualities wliicli belong to it, but apart from tlie quality of being sensible, wliicli does not belong to it. Tlie idea of an object will indeed contain some sensible qualities, and usually some visible colour. But having inferred that the invisible object is coloured only in the sense of reflect- ing asthereal undulations, by aljstraction I consider the object as so qualified, without attending to it as visibly coloured. In short, I know by scientific reasoning that objects exist apart from merely sensible qualities, and I can attend separately to their existing apart, Berke- ley fell into the error of postponing inference about classes, and therefore of limiting abstraction to direct formation of ideas from sense. Eeally, there are objects known by sense, and objects known from sense by reason ; and there is an abstraction from sense, and an abstraction from reason, though in l)oth cases the ab- straction is but attention to sensible and rational objects of knowledfje. According to Berkeley, then, starting from the Second and Third Books of Locke's Essay, all the objects of human knowledge are ideas of sensation and reflec- tion, and the collections of ideas made out of them by memory and imagination, to which he reduced abstrac- tion of ideas, and without reasoning about causes. But it is impossible for errors to remain perfectly logical. Though he had just said that all objects known to us are ideas, he proceeds, like Locke, dogmatically to assert tliat a thinking subject exists : — ' But besides all the endless variety of ideas or objects of knowledge, there is likewise something which knows or perceives them, and exercises divers operations, as willing, imagining, remembering about them. This perceiving active being is what I call mind, spirit, soul, CHAP. Til. BERKELEY 191 or myself. By wliicli words I do not denote any one of my ideas, but a thing entirely distinct from them, wlierein they exist, or which is the same thing, whereby they are perceived ; for the existence of an idea con- sists in being perceived.' ^ Berkeley was dogmatic, but right, in asserting the existence of himself; but he was wrong in calling this tliinking subject a thing entirely distinct from his ideas, and in supphdng no data for his knowledge of it. I am a thinker, from whom the subject and the thoughts are opposite abstractions. But, in sj^ite of his criticism of abstract ideas, Berkeley had already fol- lowed Locke's Secotld Book in supposing all the objects of reflection to be mere ideas of operations. The ques- tion then arises, how he could possibly know that he was also a thinking subject. Locke had said that the thinking subject is a matter of mere supposition. Berkeley went a stage further : he said that ' it cannot be of itself perceived, but only by the effects which it produceth.'^ But there are several difficulties in al- lowing him to take this view on his hypotheses. In the first place, if it is true, there is something which is known, though indirectly, without being an idea ; therefore, not all objects of understanding, but only all objects of sense, will be ideas. Secondly, if all the objects of sensation and reflection were ideas of sensible qualities and ideas of operations, as he supposes, the whole of these data would contain no subject, not of course a physical nor even a psychical subject, and nothing like a subject, for a subject is, as Berkeley admits, not an idea ; therefore, no subject, even no psychical subject, could be logically inferred. We must clioose, therefore, between the original data and the illogical conclusion. ' Princ. ii. - Id. xxvii. 192 PSYCHOLOGICAL IDEALIS.M TART II. But Berkeley was right in admitting the existence and knowledge of a thinking subject. Therefore, the data of sensation and reflection cannot be mere ideas. Even if not sensation, at least reflection must be perception of m3\self as a tliinking subject, from which I infer other thinking subjects, and God Himself. Berkeley ought to have returned to Descartes, and begun with the consciousness, ' I think.' But, although he saw that we cannot abstract what cannot exist sepa- rately, he was so enthralled by Locke that he began by supposing that we perceive ideas of qualities and ideas of operations, when we cannot even abstract these ob- jects except in the sense of attending to them in their subjects. The idea of colour and the idea of willino- are as much abstractions as the idea of a triangle. We really perceive, by sensation, at least, the coloured, and by consciousness, at least, the willing. But Berkeley, like Locke, began all sense with abstract ideas of quahties and operations. Though, unlike Locke, he saw that he could derive no physical subject from the former, he illogically thought he could derive a tliinking subject from the latter ideas, although, hke Locke, he had no data for a logical sequence from the conscious ideas of operations to the thinking subject. Curiously enough, he ended, like Locke, in after all returning to Descartes, and in admitting, ' I know or am conscious of my own being.' ^ This admis- sion that I am conscious of myself is quite incon- sistent with the original hypothesis that I perceive ideas of operations directly, and the subsequent corollary that I perceive myself only indirectly by my efiects. Nevertheless, the admission is true, and the hypothesis and its corollary false. I cannot infer a thinking sub- ' Hylas and Philonous, Third Dialogue. CHAP. vir. BERKELEY 103 ject from mere operations. I am not conscious of operations, still less of ideas of operations — an abstrac- tion, two removes from the truth. I am conscious of myself, as thinking subject. But Berkeley involved his admission of a thinking subject with another hypothesis. He accepted the Cartesian transition from self to soul without a word of proof. ^ As I have already shown, I am not conscious of this identification, I am conscious of the very reverse. The combined evidence of consciousness, observation, and reasonino- teaches me that I am a man thinking partly by my body and partly by my soul. But, you will say, Berkeley was a theologian, who, knowing that God is a spirit, rightly inferred that man is a spirit. The answer is that man is not God. It is true that there is a resemblance, but there is also a difference. When I infer that there are other men, I observe, by direct inference from sense, two sorts of signs, bodily organs and physical works, from both of which I infer a man like myself, body and soul. But God only offers me one of these signs. His works of nature, but no signs of a body. Hence I have a right to infer that He is similar to myself, so far as He by intelligence and will produces works of order, beauty, and goodness^ similar to those of man, but I have no right to infer either that He, like man, is also a body, or that man, like Him, is a pure spirit. Nor have I a right to infer that — All are but parts of one stupendous whole, Whose body nature is, and God the soul. Nature is to God as works are to man; and as a man's body is not his works, so neither is nature the body of God. ' Hie omnia regit,' says Newton^ about the Deity, ' Princ. ii. ■^ Newton, Princijpia, Lib. III. Scholium Generale {sub fin.), O 1 01 PSYCHOLOGICAL IDEALISM tart ii. ' noil ut anima miindi, sed ut universorum dominus.' God lias no body ; for liow could He liave a body pro- portionate to His infinite intelligence and will, and show it not ? God, then, is a spirit ; man is not. Now, it is true that God, for a time, gave a bodily sign, when He took upon Himself a body and made Himself man. But the incarnation of Christ is a very proof of the difference between God and man. Christ ceased to be a pure Spirit, became flesh, and dwelt among us. Berkeley cannot explain this union of the Divine and the human in Christ. God is a spirit ; but if man is also a spirit, what is the incarnation ? Berkeley's only logical answer would be the gratuitous hypothesis that Christ took upon Himself certain ideas, called the human body. But Christ had the ideas already from eternity. What He wanted was the very body, re- presented by those ideas, for a time. There is nothing for it, but that God is a spirit, and Christ took upon himself a body and became man, and man is both body and spirit in one. The idealistic hypothesis that I am a spirit is inconsistent both with philosophy and with Christianity. Yet in our own time a false philosophy of man as a purely spiritual subject is supposed to be a justification of Christian theology. Berkeley, in the Introduction and the first two sec- tions of his ' Principles,' furnished himself with his pre- mises. They are anticipations of human nature, mainly derived from Descartes and Locke, with an occasional assumption of liis own. Let it be granted, from Des- cartes, that the tliinking subject, myself, is a mind, spirit, soul. Let it be granted, from Locke's Second Book, that not only all data, but all objects of know- ledge, are simple ideas of sensation and reflection, and ideas compounded by memory and imagination. CHAP. vn. BERKELEY 195 without taking any notice of reasoning ; and let us avoid Locke's inconsistenc}^ of supposing an external physical substance beyond a collection of ideas, and his error of purely abstract ideas. Let the premises, which he owes to Descartes and Locke, be granted to Berke- ley, without his proving them. Wliat follows ? Why, the purely hypothetical, fairly logical, wholly synthetic deduction from false and unproved hypotheses, known as the Berkeleian philosophy. He who is foolish enough on the mere authority of this doctor to swallow the hypotheses, like pills, M^ill find that the deductions will purge him of all knowledge beyond spirit and ideas. Berkeley begins his deductions by explaining the existence of what he calls sensible things, and denying that what he calls unthinking things exist except as perceived : — ' The table I write on, I say, exists, that is, I see and feel it ; and if I were out of my study I should say it existed, meaning thereby that if I was in my study I might perceive it, or that some other spirit actually does perceive it. There was an odour, that is, it was smelled ; there was a sound, that is to say, it was heard ; a colour or figure, and it was perceived by sight or touch. This is all that I can understand by these and the like expressions. For as to what is said of the absolute existence of unthinking things without any relation to their being perceived, that seems perfectly unintelligible. Their esse is per dpi, nor is it possible that they should have any existence out of the minds of thinking beings which perceive them.' ^ So far as this argument follows from its premises it is hypothetically unanswerable. The esse of ideas is percipi ; if, then, all objects of human knowledge are ideas, their esse will be percipi ; and again, an unthink- ' Princ. iii. 2 196 rSYCIIOLOGICAL IDEALISM tart ii. ino- tliiiicf, wliicli is not an idea, will not be Immanly known to exist. Berkeley was entitled to these liypo- tlietical conclnsions. Bnt liis argument conceals a further false hypothesis, namely, that what is unknown by man to exist, being unintelligible to him, is non- existent ; from which he concluded that a purely un- thinking thing is not only unknown by man, but also non-existent. Thus to hypotheses and hypothetical de- duction Berkeley added dogmatism. He dogmatically asserted the existence of mind and the non-existence of matter. The importance of the deductions which immediately follow consists in their entire omission of reasoning from the data of sense to their causes, and its conse- quences, when combined with Locke's premises. Houses, mountains, rivers, and, in a word, all sensible objects, are supposed to have a separate existence. Now, says Berkeley, they are what we perceive by sense, and what w^e perceive are ideas or sensations ; therefore they are ideas or sensations.^ He adds that it is only the doctrine of abstract ideas which makes us dis- tinguish the existence of sensible objects from their being perceived.^ But it is not true that a house is a sensible object which we perceive by sense ; sense perceives only a sensible eifect of an external house, which is inferred by reasoning, and can be distinguished from the sensible effect by the attention of abstraction. But it is true that if we choose to omit reasoning about causes, and suppose that sense perceives ideas or sen- sations, the only house we should know would be, not the house now inferred, but onl}^ what we should then perceive, a mere collection of ideas or sensations, in- capable of being abstracted from being perceived. ' Princ. iv. " Id. v. CHAP. VII. BERKELEY 197 This strict though liypothetical logic from Locke's Second Book removed Berkeley into another arena of philosophy. Descartes and Locke had admitted the existence and knowledge of an external world, not merely psychical but also physical ; that a house is an external object causing our ideas ; and, in accordance with the representative theory, that perception presents ideas but represents external objects. Berkeley, agree- ing both with Descartes and Locke in the perception of ideas, but aware that neither philosopher supplied data from which to infer an external object, and following Locke in postponing reasoning about it, logically con- cludes that the external object and the sensible object are one, and that in perceiving an idea or sensation, we are perceiving not a sensil)le effect of an external house, but the house itself. His pure idealism produced the metaphysical theory that objects, supposed to be ex- ternal, are nothing but ideas or sensations in the mind, and the ps^xhological theory of a presentative percep- tion of ideas or sensations, representing nothing. Having hypothetically deduced that the esse of all objects known to man ispercipi, and that what are called external objects are really ideas or sensations, Berkeley proceeds to the conclusion that ' all the choir of heaven and furniture of the earth ; in a word, all those bodies which compose the mighty frame of the world,' exist in my mind, or in that of some created spirit ; or else subsist in the mind of some eternal spirit.^ This con- clusion also follows from the premises. If all objects of knowledge are ideas, and ideas subsist in the mind of some spirit, it follows necessarily that the whole known world subsists in the mind of some spirit. So far, indeed, as the human spirit goes, we could only speak ' I'rinc, VI. 198 rSYCIlOLOGICAL IDEALISM part ii. of tlie wliole hioicn world. We saw above that Berke- ley, while speaking even of man,^ denied the existence of what was not an object of human knowledge. He now corrects this defect by the addition of the eternal spirit,^ to whom whatever exists is known, while what is not known does not exist. Of the Divine spirit at least Berkeley could say, whatever exists is an object of His knowledge ; if, then, all objects of knowledge are ideas, and ideas subsist in the mind of a spirit, whatever exists subsists in the mind of the eternal spirit of God. Even so, however, it might be objected that, if ideas are the objects of human, it docs not follow that they are the only objects of Divine knowledge. But in Berkeley's ' Principles ' there is a perpetual equivoque between the sensible ideas of man and the intellectual ideas of God. ' From what has been said it follows that there is not any other substance than spirit ; ' this is the next hypothetical consequence.^ It is an immediate corol- lary. If there were only man, the only known substance would be spirit, but add God and it would follow that the only existing substance is spirit, so that there remains no unthinking substance.^ Berkeley further proceeds to deduce this denial of matter from the hypothesis of ideas. He is perfectly logical. Ideas cannot exist in an unthinking substance ; if then sensil:)le qualities were ideas, there would be no unthinking substance or substra- tum of those ideas or qualities.^ Again, he warns us ao-ainst those who maintained that, thouii-h unthinkinfy substance is not the substratum of sensible ideas, ideas are nevertheless the coj)ies or resemblances of unthinking substance. ' I answer,' he says, ' an idea can be like no- thincr but an idea.' ^ This memorable sentence marks » Prlnc. iii. - - Id. vi. ^ Id. vii. " Id. '" Id. ^ Id. viii. CHAP. yii. BERKELEY 199 the return of the logic of reasoning into mental philo- sophy. Berkeley at this point begins to think about reasoning, though too late ; for he had alread}^ fixed the objects of knowledge without it. But he thinks about it as a logician, and gives the answer to the illogical attempt of Descartes and Locke to first enclose man within psychical ideas, and then, without any clue in the data, expect him to discover physical objects. In the case of physical substances, if the data of inference were sensible qualities as ideas, we could infer a similar col- lection of qualities as ideas ; if they were qualities with- out being ideas, we could infer a similar combination of qualities ; but in neither case could we infer a physical substance, for which we should have no analoa'ue in sense. ^ This rigorous logic from Locke's hypotheses of ideas enabled Berkeley to destroy Locke's theories of material substance and its primary qualities at a blow : — ' Some there are who make a distinction betwixt primary and secondary qualities : by the former, they mean extension, figure, motion, rest, solidity or impene- trability, and number ; by the latter they denote all other sensible qualities, as colours, sounds, tastes, and so forth. The ideas we have of these they acknowledge not to be the resemblances of anything existing without the mind or unperceived ; but they will have our ideas of the primary qualities to be patterns or images of things which exist without the mind, in an unthinking sub- stance which they call matter. By matter,. therefore, we are to understand an inert, senseless substance, in which extension, figure, and motion do actually subsist. But it is evident, from what we have already shown, that extension, figure and motion are only ideas existing in * Cf. Princ. xxxvii. 200 rSVClIOLOGICAI. IDEALISM part ii. the mind, and that an idea can be hke nothing bnt another idea, and that consequently neither tliey nor their archetypes can exist in an nnperceiving substance. Hence it is phiin, that the very notion of what is called matter or corporeal substance involves a contradiction in it; 1 Yes ; if, and only if, qualities as sensible are ideas, an idea is like nothing but another idea, and therefore we could infer no external qualities of matter ; neither insensible primary qualities like primary qualities as sensible, nor insensible secondary qualities as modifi- cations of primary qualities and causes of secondary qualities as sensible. Now, matter is nothing without qualities ; therefore, we could not infer matter at all. The argument is quite logical, if we once admit with Locke, that, as sensible, all qualities are ideas. If with modern idealists we should substitute sensations, it would equally follow that we could infer no insensible qualities of matter, and therefore no matter at all. Berkeley added a second argument to prove that all qualities exist only as ideas in the mind and not in matter and its particles : — ' Thev who assert that fio-ure, motion and the rest of the primary original equalities do exist without the mind in unthinking substances, do at the same time acknowledge that colours, sounds, heat, cold, and such- like secondary equalities, do not, which they tell us are sensations existing in the mind alone, that depend on and are occasioned by the different size, texture, and motion of the minute particles of matter. This they take for an undoubted truth which they can demonstrate beyond all exception. Xow if it be certain that those original qualities are inseparably united with the other ^ Princ. ix. CHAP. VII, BERKELEY 201 sensible qualities, and not, even in thonglit, capable of being abstracted from tliem, it plainly follows that tliey exist only in the mind. But I desire any one to reflect and try whether he can, by any abstraction of thought, conceive the extension and motion of a body without all other sensible quaUties. For my own part, I see evi- dently that it is not in my power to frame an idea of a body extended and moved, but I may withal give it some colour or other sensible quality which is acknow- ledged to exist only in the mind. In short, extension, figure, and motion, abstracted from all other qualities, are inconceivable. Where, therefore, the other sensible qualities are there must these be also, to wit, in the mind, and nowhere else.' ^ This argument does not touch Locke, so fiir as it depends on the admission that secondary qualities are mere sensations ; for Locke said that, as sensible, they are ideas, and, as external, powers. But it touches later theories of secondary qualities, realistic and idealistic. It is true that if secondary qualities are sensations, primary qualities, as sensible, will also be sensations, from which no external quality, and there- fore no matter, could be inferred. Moreover, the argu ment is interesting as another instance of Berkeley's re- duction of the external to the sensible. He saw that on the conjoint hypothesis that sense perceives qualities as sensations, with abstraction of ideas, but without reasoning to causes^ we should only be able to infer and attend to qualities, primary and secondary, as they are fused in sensation. Hence his followers invariably re- gard primary and secondary qualities merely as various kinds of sensations, and not as external qualities. By this series of hypothetical arguments Berkeley 1 Princ, X. 202 PSYCHOLOGICAL IDEALISM pakt ii. arrived at the following conclusions : all subjects are spirits and all objects ideas of spirits. This absolute universality logically applies only to the eternal spirit. As far as the human spirit goes, Berkeley's conclusions, so far as they are logical, must be put in a more moderate form. If there are spirits, and all objects of knowledge are ideas, then all known subjects are spirits and all known objects are ideas ; a physical subject of qualities is not known to exist, and qualities, primary and secondary, are known as ideas or sensations in our minds, but are not known to be external qualities of physical subjects, bodies and corpuscles, in an external world. What, then, is to become of the minute particles of matter, their latent sizes, textures, and motions ; to say nothing of their priority, and their production of our sensations ? What,- again, are the causes of the ideas or sensations in the mind of a human spirit ? Berkeley, like Locke, at last found himself face to face with the problem of reasoning to causes. Given ideas of spirits as all the data and objects of knowledge, what causes can reason infer ? We might feel tempted now to say that Berkeley, having the universe of Divine ideas, as it were, in his grasp, would at once say that the external world of bodies, their corpuscles, and their qualities, which the natural philosopher has discovered to be the insensible causes of sensible quahties, even aether and its motions, are Divine ideas, by which the Deity produces the sen- sations of man. But Berkeley no more than the modern Berkeleian resorts to this Hegelian alternative. He precluded himself from taking it, both by his identifica- tion of the external with the sensible object, and by his doctrine of the inactivity of ideas. As the former deprived him of the external world as a distinct object, CHAP. vir. BERKELEY 208 SO tlie latter prevented him from regarding insensible causes as ideas. ' All our ideas,' says lie, ' sensations, or the things which we perceive, by whatsoever names they may be distinguished, are visibly inactive ; there is nothing of power or agency included in them, so that one idea or object of thought cannot produce or make any alteration in another.' ^ So far from resolving insensible scientific causes into Divine ideas acting on us, he uses the theory of the inactivity of ideas to deny in- sensible scientific causes. ' Whence, it plainly follows,' he concludes, ' that extension, figure, and motion cannot be the cause of our sensations. To say, therefore, that these are the effects of powers, resulting from the con- figuration, number, motion, and size of corpuscles, must certainly be false.' ^ Berkeley, having decided that the cause is not the qualities of corpuscles, proceeded to infer that it is the spirit of God : — ' We perceive a continual succession of ideas, some are anew excited, others are changed, or totally disap- pear. There is, therefore, some cause of these ideas whereon they depend, and which produces and changes them. That this cause cannot be any quality or idea, or combination of ideas, is clear from the preceding section. It must, therefore, be a substance ; but it has been shown that there is no corporeal or material substance. It remains, therefore, that the cause of ideas is an incorporeal active substance or spirit.' ^ Berkeley, like Descartes and Locke, saw that there is an involuntariness in our sensations which requires some cause. They might have all stopped there, and said that the nature of the cause is unknown ; but they were too philosophical to be agnostics. Descartes ' Princ. XXV. ^ Id. ^ Id. xxvi. 204 PSYCHOLOGICAL IDEALISM part ir. and Locke, however, were not log-ical enouojli to see wluit cause could be inferred from their data ; but guided b}^ real facts rather than by their theories illogically supposed that, without anything physical in the data, we could infer a physical cause. Berkeley, on the other hand, was the first of the psychological idealists to see that the data and ol)jects of knowledge must determine the inference ; so that, if the data and objects are mind and ideas, when we find ideas in sensation, which are due neither to one's own ideas nor to one's own mind, we cannot infer a corporeal or material substance, but must infer that the cause is either other ideas or another mind. He had elimi- nated other ideas by his doctrine of the inactivity of ideas. There remained another mind. Now, proceeds he, though we are conscious of being able to produce some ideas by will, yet the ideas of sense have not a like dependence on our will ; there is therefore some other will or spirit that produces them, and in an order which proves that this cause is the spirit of God. ^ Thus, the solution, which was suggested by Descartes, as a possible alternative in his ' Principia Philosophige,' ^ and which ought to have been taken by Locke in the Fourth Book of his Essay, when he had deserted mere ideas in favour of an intuition of oneself and a demon- stration of God, was at length adopted by Berkeley in his ' Principles.' If all the data are ideas and minds, created and eternal, and if ideas are inactive, the only loc^ical conclusion is that the sensible ideas of created minds are direct imprints of the eternal Spirit of God. This logical conclusion of psychological idealism, evaded by Descartes and Locke, was accepted by Berkeley, with all its hypothetical consequences. As ^ Princ. xxviii.-xxx. * Descartes, Princ. ii. 1. CHAP. Til. BERKELEY 205 usual, he felt the double edge of his weapon, and was prepared not only with what is, but with what is not. On the one hand, he concluded that God is, and on the other hand, that matter is not, the cause of our sensa- tions.^ Secondly, he concluded that ' the set rules or established methods, wherein the mind we depend on excites in us the ideas of sense, are called the laws of nature.' ^ Thirdly, he concluded that God is not merely the prime cause, but the immediate and sole cause of sensible effects, setting aside second causes, such as the sun and the motion of bodies : — ' And yet this consistent uniform working, which so evidently displays the goodness and wisdom of that governing spirit, whose will constitutes the laws of nature, is so far from leading our thoughts to him, that it rather sends them a-wandering after second causes. For when we perceive certain ideas of sense constantly followed by other ideas, and we know that it is not of our own doing, we forthwith attribute power and agency to the ideas themselves, and make one the cause of another, than which nothing can be more absurd and unintelligible. Thus, for example, having observed that when we perceive by sight a certain round luminous figure, we at the same time perceive by touch the idea or sensation called heat ; we do from thence conclude the sun to be the cause of heat. And in like manner perceiving the motion and collision of bodies to be attended with sound, we are inclined to think the latter an effect of the former.'^ Finally, he presents us with his complete theory of real things, when second causes have been expunged :'* — ' The ideas imprinted on the senses by the author of nature are called r^rt^ ^/r/;<^.§ ; and those excited in the 1 Berkeley, Princ. xxvi. - Id. xxx. ^ Id. xxxii. ^ Id. xxxiii. 200 PSYCHOLOGICAL IDEALISM part ii. imagination, being less regular, vivid and constant, are more properly termed ideas or images of things, which they copy and represent. But then our sensations, be they never so vivid and distinct, are nevertheless ideas, that is, they exist in the mind, or are perceived by it, as truly as the ideas of its own framing. The ideas of sense are allowed to have more reality in them, that is, to be more strong, orderly and coherent than the creatures of the mind ; but this is no argument that they exist without the mind. They are also less dependent on the spirit, or thinking substance which perceives them, in that they are excited by the will of another and more powerful spirit ; yet still they are ideas, and certainly no idea, whether faint or strong, can exist otherwise than in a mind perceiving it.' This passage marks a turning-point in the history of idealism. Hitherto, the line between ideas of sensation and ideas of conception had not been so carefully drawn as that between all ideas and the physical realities which cause them. Now, Berkeley, having deduced the destruction of physical realities, while still preserving the h3q:)othesis that ideas are the objects of sensation, was puzzled to find some boundary between the real and the ideal. He drew it between the ideas of sensation and the ideas of imagination, partly by their vividness and faintness, but mainly because the former are directly produced by God. Hence, he identified sensible ideas with real things, at the same time explain- ing that they are after all oidy ideas. Sensible ideas he declared to be his reriim natura} He even admitted corporeal substances, 'taken in the vulgar sense for a combination of sensible qualities,' not ' in the philosophic sense for a support of accidents or ' Princ. xxxiv. CHAP. VII. BERKELEY 207 qualities without the mind.' ^ So sure was he that sensible ideas are the real things, that he even said that 'we are fed and clothed with these things which we perceive im- mediately by our senses ; ' that is, by sensible ideas.''^ Thus did he reduce reality to ideas imprinted on our senses by God without the intervention of physical causes, sense to the presentation of sensible ideas repre- senting no external bodies, and knowledge to collections of ideas inferring no external cause except God. He took the show of sense for the nature of things, and thought that, if the veil were uplifted, we should see nothinc^ but God. This doctrine of reality, much more logical, but also far narrower than that of Descartes and Locke, is the transition to Hume's distinction of impressions and ideas, and has ended in the ordinary sensationalism of modern Berkeleians, such as Mill, who do not indeed say that God is the direct cause of our sensations, but give up the problem and leave sensations in mid-air, nor dogma- tise about all reality but confine themselves to known reality, in other respects differing in nothing but ter- minology from Berkeley. The fundamental character of ]3erkeleianism is the theory that everything real is either my sensations and combinations of sensations, or those of other minds. ' I do not believe,' says Mill, ' tliat the real externahty to us of anything, except other minds, is capable of proof.' ^ It is often said that Berkeley is unanswerable, in his final position that the real world consists of ideas im- printed on our senses, not by nature, but by the spirit of God. He cannot be answered by the hypothetical 1 Princ. xxxvii. ^ Id. xxxviii. ^ Examination of Sir W. Hamilton s Philosoj^hy, chap, xi., note, 8uh fin. 208 PSYCHOLOGICAL IDEALISM part ii. realism of cosmotlietical idealists, such as Descartes and Locke and their modern successors, because they start knowledge, like Berkele}^, with nothing but psychical data, from which nothing but the psychical could be inferred, and only suppose it to infer j^hysical causes, by bad logic. Berkeley was the first logician of idealism. Cosmothetic idealism is an inconsequence, which must end in pure idealism at last. Again, he cannot be answered by intuitive realism, because it rests on the false identification of the sensible and external world by common sense, instead of appealing to the distinction of the sensible effect from the external cause by science. It is no use to knock the stick on the ground, when Berkeley resolves the ground and the stick into ideas, and the agent into a spirit. It is no answer to assert that the things immediately perceived are real things ; for Berkeley admits it, but says that they are also sensible ideas or sensations.^ It is no answer to oppose a presentative perception of apples and houses to a philosopher, who agrees but rejoins that the things presented are only collections of ideas. If Berkeley is equal to the intuitive realist on the ground of common sense, he is superior on the ground of science and philo- sophy. The intuitive realist supposes that the real world directly perceived is external ; science shows that it is within ; Berkeley adds that it is within the mind. The intuitive realist supposes that a secondary quality is directly perceived as a mere sensation in the mind, a primary quality as a real quality in the external world ; Berkeley, in a far more philosophic spirit, shows that they are directly perceived in the same manner, for, as sensible it is hnpossible to separate extension, figure and motion from other sensible qualities. Both confuse two ' Pfinc. xxxiii. seq.; Hylas and PJiilonous, Third Dialogue, suh fi7i. CHAP. VII. BERKELEY 209 realities, distinguislied by science, the sensible and tlie external ; but, if this common confusion could be over- looked, it would be more scientific to make the real object of immediate perception, with Berkeley, entirely internal, than, with intuitive realism, partly internal and partly external — as if I could perceive the light of a candle within me, and its extension in the outside world. The truth is that idealists and realists have had too many errors in common with Berkeley to answer him. Idealists share his error that the data are ideas, realists that the real world is the object of immediate percep- tion. All of them, also, confine themselves too much to perceptible bodies, to the neglect of imperceptible corpuscles. Within that narrow circle Berkeley has no difficulty in resolving apples and houses, and even mountains and rivers, into sensible ideas. But we must turn the corner of pure idealism. The question is not what it makes of the sensible and the perceptible, but what it does with the imperceptible. The true contra- dictory instance against Berkeley's position is the natural philosophy of the imperceptible world of cor- puscles, which cause, but are not, and cannot be inferred from, sensations or sensible ideas. This is the answer of physical realism. Let us proceed to its details. In one way God, in another way nature, causes our sensations. There are two opposite extremes to be avoided — the substitution of nature for God, and that of God for nature : the former the temptation of the natural philosopher, the latter that of the natural theologian. The natural philosopher prolongs the chain of physical causes, until at last he feels tempted to believe that he has expelled intelligence from nature, and say, ' I have swept the universe with my telescope and cannot find God.' Tlxe natural theologian, dazzled 210 PSYCHOLOGICAL IDEALISM part n. by tlie universal cause, is apt to neglect tlie subordinate agency of physical causes, and forget nature in the love of God. Natural philosophy is limited by the nature of its evidence. God is inferred by combining the evidence of outer and inner sense ; but natural philosophy reasons only from sensation and observation, without conscious- ness and reflection. Of itself, nature can neither prove nor disprove a deity. Even within its own limits natural philosophy is limited. Evolutionists, for example, have been more successful in dealing with organisms than in the far larger problem of the inorganic world. Evolution consists in the differentiation of homogeneous matter. Now differentiation invariably requires one of two condi- tions : either one efficient cause must act on different materials, as when tlie same kind of motion produces molar motion in one body and molecular in another ; or different efficient causes must act on one kind of material, as when different lengths of undulation produce sensible heat or sensible light in the nervous system. Both alternatives presuppose difference ; the former difference in the patient, the latter difference in the agent. There is no known instance of one kind of cause acting on one kind of material and producing different kinds of effects. Hence, if we suppose matter, absolutely homo- geneous, universally diffused, and reciprocally acting in its various parts, it would contain no difference either of agent or patient to produce the different effects of actual nature ; but all its particles, at equal distances, would exert all forces equally in all directions, and produce an exact balance, with no differences whatever. The theory of evolution, therefore, is no explanation of the beginnings of difference. But given a pre-existing difference, even of two groups of particles with dif- CHAP. VII. BERKELEY 211 ferent arrangements of tlieir primary qualities, how- ever slight, evolution is the further differentiation, not of the absolutely, but of the relatively homo- geneous into the more heterogeneous, arising from different structures acted on by one kind of agent, or different agents acting on one kind of structure, or different agents acting on different structures, and so on ad infinitum, not a parte ante, but a parte post. There must, however, be something else to cause an original difference in things. But limited as natural philosophy is within, it is still more limited from without. Having only reasoning from outer sense and observation, it dis- covers physical causes ; but it cannot tell what else they may be. Natural theology now steps in, to supplement sensa- tion by consciousness, observation by reflection, and to reason from both outer and inner sense. To observa- tion, a workman and a product have the mere appear- ance of cause and effect ; but when we add conscious reflection, we infer that he is an artist using means to an end ; and, when we observe again a similar work, we still infer an artist. So from His work, natural theology infers a Divine Architect of nature, establishing the original difference of things, and developing further differences, by using physical causes of effects as means to ends. ' Omnia quae agunt in virtute primi agentis agunt.' When science shows that evolution develops living organs, this is no reason why this very evolution should not be a Divine means of producing fresh life. The growth of a tree has not been regarded as inconsis- tent with Divine agency ; why, then, should not Divine power be exercised in the whole growth of the world ? On the other hand, the natural theologian must not forget that, after all, the existence of nature must bQ r 2 212 rSYCIIOLOGICAL IDEALISM tart ii. more certain than that of God, and that, indeed, without the order of nature the main part of the evidence for a God disappears. If God is the intelhgent cause, most certainly the means used are physical causes. Ah attempts to argue that because God is the cause of all effects, insensible motions are not causes, or that there can be no evolution, must fail, because nothing is more surely established than the powers and laws of motion. To convert God from an Intelligent Will using physical means into the direct and sole cause of every effect, even to the threshold of our senses, is the greatest danger that can befall natural theology, which must then yield to the laws of the communication and conser- vation of motions. No reconciliation of theology and science will be found superior to that of Bacon,^ which admits too of being perpetually enlarged with every physical dis- covery : God having made nature uses it as a means ; the more physical causes, the more means at His com- mand ; the more elaborate and indirect the physical process, the more subtle the Divine Architect ; who, having established a difference in corpuscular structure, uses the evolution of one particle acting on another as His further process of differentiation and His most in- genious plan ; and natural philosophy is always, how- ever unconsciously, prolonging the chain of physical causes to the throne of God. ' Sic Dei sapientia effulget mirabilius,' says Bacon, 'cum Natura aliud agit, Provi- dentiaaliud elicit, quam si singulis schematibusetmotibus naturalibus Providentiae characteres essent impressi.' Berkeley for nature substituted God. By his hypo- theses and logical deductions he was compelled to say ' Be Augmentis Scientiarum, iii. 4, sub fin. (Ed. Ellis and Spedding, vol. i. p. .570.) CHAP. VII. BERKELEY 213 that ideas are imprinted on our senses, not by tlie in- sensible motions of physical substances, but by the direct agency of God Himself. Instead of an Intelligent Agent, using nature as the means to produce effects on our senses, God, without the intervention of insensible nature, thus becomes the direct and sole cause of every sensible effect. There is God, then, and no nature, but the nature of man. The good bishop flattered himself that he was thus serviuQ- the cause of his relifrion. But how different is the doctrine of the Bible ! In the beginning God created tlie heavens and the earth ; and, only after nature, man. This is the meeting-point of religion and science. In substituting God for nature, and denying second causes, Berkeley not only falsified religion but also contradicted science. He said that God is, but nature is not, the cause of our sensations. His followers have deserted his theory of religion, but they have supplied no adequate theory of science. Any mental philoso- pher, who says that real things are our sensible ideas or sensations, whether he says that they are produced by God, witli Berkeley, or, with the modern Berkeleian, gives up the knowledge of the causes of our sensa- tions, in eitlier case he is following Berkeley in rejecting the positions of natural philosophy that the external sun is the cause of sensible heat, that the motion and collision of particles of air insensibly proceed till at last they produce sensible sounds, and that imperceptible corpuscles, with their configuration, number, motion, and size, cause our sensations.^ Psychological idealism had gradually brought mental philosophy into this state of paradox by the very poverty of its data. Descartes was a scientific genius, labouring to ' Cf. Princ. xxv., xxxii. 211 rSYCriOLOGICAL IDEALISM part ii. hving a narrow mental into harmony with a wider natural philosophy. Locke, beginning to feel the ditliculty, depre- ciated natural philosophy, because he could not explain it. Berkeley, logically deducing the vanity of the attempt at explanation, boldly wrote a polemic against the natural philosophy of corpuscles and their motions.^ Tliis sad, but inevitable, defect is generally omitted or extenuated by historians of philosophy. But Berkeley himself was well aware what were the logical conse- quences of idealism. One passage from his polemic will be sufficient : — ' Some have pretended to account for appearances by occult qualities, but of late they are mostly resolved into mechanical causes ; to wit, the figure, motion, weight, and such-like qualities of insensible particles : whereas, in truth, there is no agent or efficient cause than spirit, it being evident that motion, as well as all other ideas, is perfectly inert. (See sect, xxv.) Hence to endeavour to explain the production of colours or sounds by figure, motion, magnitude, and the like, must needs be labour in vain. Accordingly, we see the attempts of that kind are not at all satisfactory.' ^ But we have seen, since Berkeley's time, a sure progress in the natural philosojDhy of mechanical causes. A striking contrast to the passage just quoted may be found in the following quotation from Professor Tyndall's ' Fragments of Science ' ^ : — ' The domain in which this motion of light is carried on lies entirely beyond the reach of our senses. The waves of light require a medium for their forma- tion and propagation ; but we cannot see, or feel, or taste, or smell this medium. How, then, has its exist- ence been established? By showing that, by the 1 Princ. ci. seq. ^ Id. cii. ^ pp_ 72_3. CHAP. Til, BERKELEY 215 assumption of tliis wonderful intangible cether, all tlie pliasnomena of optics are accounted for, with a fulness, and clearness, and conclusiveness which leave no desire of the intellect unsatisfied. Wlien the law of gravi- tation first suofo'ested itself to the mind of Newton, what did he do ? He set himself to examine whether it accounted for all the facts. He determined the courses of the planets ; he calculated the rapidity of the moon's fall towards the earth ; he considered the precession of the equinoxes, the ebb and flow of the tides, and found all explained by the law of gravitation. He therefore regarded this law as established, and the verdict of science subsequently confirmed his conclusion. On similar, and, if possible, on stronger grounds, we found our belief in the existence of the universal sether. It explains facts far more various and complicated than those on which Newton based his law. If a single pha3- nomenon could be pointed out which the asther is proved incompetent to explain, we should have to give it up ; but no such phsenomenon has ever been pointed out. It is, therefore, at least as certaii;! that space is fiUed with a medium, by means of which suns and stars diffuse their radiant power, as that it is traversed by that force which holds in its grasp, not only our planetary system, but the immeasurable heavens them- selves.' Berkeley's idealism is unscientific. From this point we must retrace our steps by the method of analysis. By the falsity of the consequences we must destroy the original hypotheses and find the real data of reasoning from sense to science. By a chain of logic, he had hypo- thetically deduced that, if all objects of human know- ledge are ideas, derived from outer and inner sense, and by the help of memory and imagination variously com- 21G PSYCHOLOGICAL IDEALISM part ii. ])oiindo(l into collections of ideas, in the minds of created spirits, then such a spirit will be able to infer nothing but ideas and spirits, and to conclude that, if all ideas are inactive, our sensible ideas, which are passive and not caused by our own will, must be imprinted on our senses by the will of the eternal spirit of God ; so that real things, as distinguished from mere ideas of imagina- tion, will be the sensible ideas directly imprinted on our senses by Divine, without the intervention of physical causes. Now, the flaw in this chain is in its last link, in the logical but false rejection, witli which it ends, of the bodies, corpuscles, and mechanical causes, discovered by natural philosophy. What is corpuscular science ? In brief, there are bodies insensible and imperceptible, or corpuscles. They possess primary qualities, various species of which are secondary qualities ; especially, they possess motion, a primary quality, wliose secondary species are undula- tions of cEther, vibrations of air, &c., and which also exists in various forms, such as cohesion, gravitation, chemi- cal attraction, electricity, magnetism, &c. Corpuscles have innumerable similarities and uniform relations or laws of nature, and especially the laws of motion and of the causation of motion by motion. They are also the particles of masses, or larger bodies, which are partly inorganic and partly organic. Among organ- isms are bodies containing nervous systems, which consist, like other masses, of corpuscles having the various motions of bodies in general and a peculiar ner- vous motion, combined with muscular motion. Lastly, some of the other bodies, among their innumerable pro- cesses of cause and effect, produce in nervous systems sensible effects, such as sensible motion, sensible heat, &c. Such are the objects of corpuscular science. CHAT. YII. BERKELEY 217 Corpuscular science destroys Berkeley's idealism in liis logical conclusion from liis original hypotheses. He denied second causes ; but motions producing motions are second causes. He said that God's "will is the sole cause of sensible effects ; but corpuscular motions, acting on the corpuscles of the nervous system, also produce sensible heat, colour, sound, &c. If God is the prime cause, nature is the second cause, by means of which He acts on man. He said that the rules wherein God excites in us the ideas of sense are the laws of nature. But the uniform relations of corpuscular mo- tions among themselves are an immense system of laws, compared with which the laws of their action on the nervous system and the senses are but a diminutive fraction. What account would it be of the universal law of gravitation, of every particle to every particle in the universe, to say that it is merely a rule to excite in us the sensible idea or sensation of weight ? God, tlien, is not the only cause, but under Him nature is also the cause and law of sensible effects. Again, Berkeley said tliat sensible ideas imprinted on sense by God are the real tilings, and external bodies are not : the Berkeleian says the same thing of sensations, only without dogmatism about the sole causation of God and about the absolute non-existence of external bodies. But the natural philosopher knows that external bodies are not sensations, but the causes of sensations and sensible ideas. For example, the gravitations of par- ticles are not sensations, but are the known causes of sensible weiglit being felt by us. Therefore, so far from being non-existent, or so far from not being known to exist, external bodies and tlieir motions are known to exist as causes of sensible effects. To the Berkeleian, theUj we must answer, not all known realities are sensa- 218 rSYCIIOLOGICAL IDEALISM tart ii. tions ; to Berkeley liimself, not all realities are sensible ideas imprinted on our senses by the Author of our being ; but some known realities are external bodies and their qualities producing sensible effects in us. There is a known world of real bodies, intervening between God and man, and used by God as a means to cause effects in our senses. Corpuscular science destroys Berkeleian idealism not only in its hypothetical conclusions but also in its original hypotheses of the objects and data of human knowledge. Insensible corpuscles and their qualities are not our ideas, but the causes of our ideas. They are objects of natural philosophy, which, in the hands of Newton and his successors, is a kind of knowledge. Therefore, not all objects of knowledge are ideas, and some of the objects are corpuscular causes of our ideas. Again, if the original data were ideas, these corpuscular causes could not be inferred, as Berkeley logically showed. But they are scientifically inferred by natural philo- sophy. Therefore, neither the original objects nor the original data are mere ideas. CorjDuscular science deals' double death to logical idealism. Berkeley had logically deduced from his hypothesis that all qualities are only sensible ideas. But natural philosophy has shown that insensible corpuscles have the primary quality of insensible motion, obeying various laws, and that insensible modes of corpuscular motion are the secondary qualities of light, heat, and sound in the universe. Sir Isaac Newton showed that, beyond the sensible resistance or weight which we feel, there is an insensible gravitation of particles which pervades the universe, which connects parts of bodies inaccessible to our senses, and which, in one of its myriad appli- cations, causes bodies to feel heavy in our hands. CHAP. VII. BERKELEY 219 Qualities, tlien, primary and secondary, are known in natural philosophy to belong to external bodies, as well as cause sensible effects in us. Moreover, their range in the insensible world of science is infinitely more extensive than their perception by sense. Qualities, therefore, are not mere sensible ideas or sensations, but are mainly the external characteristics of masses and corpuscles in nature. But, again, external qualities of bodies could not be inferred from sensible ideas of minds. There- fore, qualities, even as sensible, are not sensible ideas. Berkeley was compelled by the logic of his idealism to reduce all qualities to sensible ideas, but he was doubly wrong in point of fact. Primary and secondary qualities, as known to corpuscular science, are neither reducible to, nor inferrible from, sensations or sensible ideas. Again, from Locke's hypothesis that sense always perceives ideas of qualities, Berkeley consistently de- duced that we cannot suppose an unthinking substance,^ that Locke's substratum is an abstraction, like materia prima^ and that the only known substance is a combina- tion of sensible qualities, or ideas, with which we are fed and clothed.^ But are these conclusions true and scientific ? The matter, known to natural science, is durable, extended, moving, causing and receiving mo- tion ; it is not, indeed, also something else distinct from being these things ; nor, however, is it mere duration, extension, motion, causation, and reception of motion, distinct but combined. Li other words, matter or body is not the abstract substrate supposed by Locke, nor the equally abstract combination of qualities substituted by Berkeley, but a qualified subject, characterised by a number of qualities. Now, besides all this, it is * Princ. vii. ^ Id. xi., xvi. ^ Id. xxxvii.-xxxviii. 220 PSYCHOLOGICAL IDEALISM part ii. not, tlioiiii'li it sometimes causes, a collection of sensible ideas. A drop of water contains the particles enume- rated in the first page of this essay ; but the sensible effect of it on any of my senses, and the ideas I after- wards form of it, do not contain anything of the kind, and are totally incapable of containing such a number of units of any kind, which are only inferred by reason. If tliere are so many particles in a drop of water, how many in a river, and how many in the ocean ? The truth is, that an analysis of a substance into particles is not a division of the sensible object, sensation, or sensible idea, but of the external object inferred. Corpuscles, then, are a proof of external bodies. Hence it follows that known substances are not abstract substrates of qualities, nor abstract collections of qualities, nor still more abstract ideas of collections of ideas of qualities, but qualified subjects, some of which are thinking and partly psychical, others unthinking and entirely phy- sical. Again, as physical substances are not qualities nor ideas, so neither could they be inferred from such data. If sense never perceived anything but spiritual sensations or sensible ideas or qualities, science could not infer durable, extended, moving bodies containing corpuscles. But these substances are the very subjects of the laws of motion and gravitation. It follows, then, that the data of sense from which they are inferred are not mere qualities, still less sensations, least of all ideas, but the nervous substance sensibly qualified. To return at last to Berkeley's first principle. He said that all the objects of human knowledge are ideas imprinted on the senses, or else such as are perceived by attending to the operations of the mind or collections of these ideas. This supposed principle is a false hypothesis containing two fundamental errors ; an error CHAJ?. VII, BERKELEY 221 about objects known, and an error about objects per- ceived. The insensible and imperceptible corpuscles discovered by natural pliilosopliers are not ideas of any of these kinds, though they are causes of them. Not all the ol3Jects of human knowledge, then, are ideas. Secondly, if the objects imprinted on the senses were ideas, the insensible corpuscles could not have been inferred. Not all the objects of human perception, then, are ideas. Insensible imperceptible corpuscles are physical objects of knowledge inferred from physical data of sense. Similarly their esse is not per dpi, as it would be if they were ideas. The esse of ideas of sen- sation is jyercipi. The esse of a sensible object is ^er- cipi by sense. An accident of the esse of an external body, e.g. water, is per dpi by inference. But the esse of an imperceptible corpuscle, e.g. in a drop of water, is not perdpi at all. Berkeley, by a confusion of esse and perdpi, adopted a presentative theory of perception, like the intuitive realists ; by a confusion of the sensible object with a sensible idea, his presentative theory is not realistic but idealistic ; by a confusion of the sensible and the real, it is a theory that we present sensible ideas as the real tilings.^ He recurs again to this theory, as the very kernel of his philosophy, at the end of the Third Dialogue between Hylas and Philonous : — ' Phil. I do not pretend to be a setter-up of ?ieiv notions. My endeavours tend only to unite and place in a clearer light that truth, which was before shared between the vulgar and the philosophers ; the former being of opinion, that those tilings they immediately per- ceive are the real things ; and the latter, that the things immediately perceived are ideas which exist only in the ' Cf. Princ. iv. 222 rSYCIlOLOGICAL IDEALISM part ii. mind. ^Vliicli two notions put together do, in effect, constitute the substance of what I advance.' Each one of the propositions in this theory is false. First, the things we immediately perceive are real things, but not the real things. There is an immense multi- tude of real things known to science, but not im- mediately perceived. The apple, the table, the house, the river, the mountain, cause sensible effects, which are real enough ; but they are external bodies whose cor- puscles are known to have a like but different structure from that of the sensible effects ; the particles of a table are not the particles of my hand lying on it, nor of my tactile nerves, still less of the operation of sensation. Secondly, the things immediately perceived are not ideas which exist only in the mind. It is true that they are within me, and here is Berkeley's superiority over the intuitive realist. But, apart from the absence of direct evidence that the hard., or hot, or heavy felt is an idea within my mind ; if it were so, I could never infer the bodies and corpuscles, which, as we have found, are too well established in natural philosophy to be any longer denied. Therefore, things immediately perceived are, not ideas which exist only in the mind, but bodily effects of bodies on the nervous system. Lastly, Berkeley wishes us to draw the conclusion that ideas which exist in the mind are the real things, and that physical objects are not real things. His premises to prove it, however, are both false ; for, as we have seen, the things immediately perceived are neither the real things, nor ideas. Hence his syllogism only proves that ideas are real things, and some real things are ideas ; which is true enough, but also consistent with other real things. Xow, corpuscular science proves bodies which are real things in the external world ; and, to infer them, CHAT. VII. BERKELEY 223 logic requires bodily data, wliicli are real things in the nervous system. Other real things, then, are known and perceived, besides ideas. Berkeley's idealism — and we may add all Berkele- ianism — is false, metaphysically, psychologically, and logically : — 1. His metaphysical theory of existence is false, because not all real things are sensible ideas whose sole cause is God ; but some realities are known to be physical causes. 2. His psychological theory of immediate perception is false, because we immediately perceive neither sen- sible ideas, nor sensations, nor the real things, but real physical effects, representing real physical causes. 3. His logical theory of reasoning is false, because from the first he prefers imagination and memory of ideas to reasoning about causes, and reasoning syntlie- tically from hypotheses to reasoning analytically from facts. Berkeley omitted nature, between sense and God. Starting from Locke's hypothesis of the objects of know- ledge, he rejected discoveries of natural pliilosophy, when he ought to have preferred the latter to the former. He ought to have gone still further, and surrendered not only Locke's hypothesis of the objects, but also tlie hypotliesis of Descartes that tlie data of knowledge are psychical ideas. When Newton had shown what could be done in natural philosophy, mental philosopliy should have reformed its data to explain his discoveries. But how seldom philosophers realise that their theories of man ought to explain a Shakespeare, a Bacon, a Newton ! To infer the Newtonian philosophy, the senses of man must perceive, not ideas of qualities, but various parts of the physical substance of the nervous system sensibly 221 rSYCIlOLOGICAL IDEALISM part n. qualified as durable, extended, moving, as well as sound- ing, heated, coloured ; from wliicli even an ordinary man infers insensible bodies, a scientific man their imper- ceptible corpuscles and motions and laws. If all objects of human knowledge were ideas of spirit, man could infer nothing but spirit and ideas. But the antecedent is an hypothesis, for which Berkeley had no authority except Descartes and Locke: the consequent is false, being contradictory to corpuscular science : therefore, the antecedent hypothesis is also false, because from true premises it is not possible to draw a false conclu- sion. The real world includes, between the sensible and the supernatural, the natural world of insensible bodies and imperceptible corpuscles, which are physical objects of scientific knowledge inferrible only from physical data of human sense. Such is the answer of physical reahsm. 99^ CHAPTER VIII. Berkeley's theory of vision. Ix answering tlie objections which might be made against his ' Principles,' Berkeley refers to his ' Essay- to wards a New Theory of Vision ' as follows : — ' Thirdly, it will be objected, that we see things actually without or at a distance from us, and which consequently do not exist in the mind, it being absurd that those things which are seen at the distance of several miles should be as near to us as our own thoughts. In answer to this, I desire it may be con- sidered, that in a dream we do oft perceive things as existing at a great distance off, and yet for all that, those things are acknowledged to have their existence only in the mind. * But for the fuller clearing of this point, it may be worth while to consider, how it is that we perceive dis- tance and things placed at a distance by sight. For that we should in truth see external space, and bodies actually existing in it, some nearer, others farther off, seems to carry with it some opposition to what hath been said, of their existing nowhere without the mind. The consideration of this difficulty it was, that gave birth to my " Essay towards a New Theory of Vision," which was published not long since. Wherein it is shown that distance or outness is neither immediately of itself perceived by sight, nor yet apprehended or judged of Q 22G rSYCIlOLOGICAL IDEALISM pakt ii. by lines and angles, or anything that hath a necessary connexion with it : but that it is only suggested to our thoughts by certain visible ideas and sensations attend- inir vision, which in their own nature have no manner or similitude or relation, either with distance, or things placed at a distance. But by a connexion taught us by experience, they come to signify and suggest them to us, after the same manner that words of any language suggest the ideas they are made to stand for. Insomuch, that a man born blind, and afterwards made to see, would not, at first sight, think the things he saw, to be without his mind, or at any distance from him. See sect. xli. of the forementioned treatise. 'The ideas of sight and touch make two species, entirely distinct and heterogeneous. The former are marks and prognostics of the latter. That the proper objects of sight neither exist without the mind, nor are the images of external things, was shown even in that treatise. Though throughout the same, the contrary be supposed true of tangible objects : not that to suppose that vulgar error, was necessary for establishing the notions therein laid down ; but because it was beside my purpose to examine and refute it in a discourse concern- ing? vision. So that in strict truth the ideas of sifijht, when we apprehend by them distance, and things placed at a distance, do not suggest or mark out to us things actually existing at a distance, but only admonish us what ideas of touch will be imprinted in our minds at such and such distances of time, and in consequence of such and such actions. It is, I say, evident from what has been said in the foregoing parts of this treatise, and in section cxlvii. and elsewhere of the Essay concerning Vision, that visible ideas are the language whereby the governing spirit, on whom we depend, informs us what CFAr. VIII. BEEKELEYS THEORY OF VISION 227 tangible ideas lie is about to imprint upon us, in case we excite this or that motion in our own bodies. But for a fuller information on this point, I refer to the Essay itself.' ^ Here we find from Berkeley's own words that he had more than one object in writing the ' Theory of Vision.' It is an essay half physical, half psychological, and this doubleness of purpose has ever since clung to the subject. On the one hand, he wanted to destroy the exaggerations introduced by mathematicians into optics, by showing that the eye is not fitted to see any- thing, and therefore not any lines and angles, beyond itself; on the other hand, he wanted to support the idealistic theory, which he had already conceived, and shortly intended to publish in the ' Principles,' by show- ing that, whereas we do not see things without, we do see visible ideas and sensations. In its first purpose, the main thesis of the ' Theory of Vision ' is a great optical discovery, though exaggerated ; in its second purpose, it is an excellent disproof of intuitive realism, but no proof at all of psychological idealism. Perhaps no treatise has ever evinced such a singular compound of genius and confusion. The effect both of its truth and its falsity persists to this very day, especially in the hypothesis of ' local signs.' What does Berkeley prove about the sense of vision ? He divides the subject into four parts — distance, magni- tude, situation, and the difference between sight and touch. ^ On the first point, he says that ' distance being a line directed endwise to the eye, it projects only one ' Princ. xlii.-xliv. ^ Theory, i. Distance is discussed in i.-li. ; Magnitude, lii.-lxxxvii. ; Situation, Ixxxviii. cxx. ; The dillerencc between sight and touch, cxxi. to end. Q 2 228 I'SYCIIOLOGICAL IDEALISM tart it. point ill the funil of the eye, which point remains invariably the same, whether the distance be longer or shorter.' ^ This proves, according to him, that we do not see distance at all, but really that we do not see remote distance, in depth or the third dimension, verti- cally from the eye. As he says elsewhere, we see no solidity or profundity.^ On the second point, he shows that we do not see the real magnitude, greater and smaller, of an external object. 'Thus, for instance,' he very properly remarks, ' the very same quantity or visible extension, which in the figure of a tower doth suggest the idea of a great magnitude, shall in the figure of a man suggest the idea of much smaller magnitude.' ^ On the third point, he relies on the inverted image in vision to show that we do not see the real situation, as high and low, of external objects. On the fourth point, he makes the instructive remark that there is no vision of resistance,^ and he has brought out more clearly than any of his predecessors that ' there is no one self- same numerical extension perceived both by sight and touch,^ and that ' we never see and feel one and the same object.' •" This conclusion is the great stumbling-block to the ordinary man, who has so overlaid sense with inference, and, we may add, had so many visible pictures of his hand and other members visibly touching visible objects, all within his sense of vision, that he finds himself almost incapable, even when he becomes a philosopher, of realising to himself that he is really seeing one set of objects within the retina and feeling another within the tactile nerves, while he infers an external object in re- ' Thcorij, ii. - lb. cxxxv., cliv. ^ lb. Ivii. ^ lb. cxxxv. ■ lb. cxxi. ''' lb. xlix. CHAP. TJii. BERKELEY'S THEORY OF VISION 229 latioii to both. Never tlieless, Berkeley verified the pre- vious scientific discovery of the distinction between ex- ternal and sensible objects by his new discovery of the invisibility of remote distance. Since we do not see distance in the third dimension from the eye, we cannot see, but only infer, a remote object. The visible object might, indeed, still be an object touching the eye ; but even this hypothesis is negatived by the further study of the nervous system. What did Berkeley not prove about the sense of vision ? On the very first point, while he proved that we do not see remote distance he did not prove that we do not see distance at all. He did not prove that we do not see a surface painted on the retina, with its distances. There are three dimensions of extension or space ; in each there is distance — distance from point to point of a line, from line to line of a surface, from surface to surface of a solid : in each dimension the parts or places, which are distant, are out of one another. Now what he proved was that there is no vision of the third dimension, not that there is none of the other two ; that there is none of distance in depth, not that there is none of distance in length and width ; that there is none of outness in the external world, not that there is none of outness of parts on the surface painted on the retina ; that there is none of sohd, not tliat there is none of superficial extension ; tliat there is none of distance endwise to the eye, not that there is none of space and its distances within the eye. In short, he concluded more than he proved. ' It is,' he says, ' I think, agreed by all, that distance, of itself and immediately, cannot be seen.' ^ It is still agreed by present psychologists ; but we want something more than agreement to prove ' Thconj, ii. 230 rSYCIIOLOGICAL IDEALISM pakt ii. that, because remote distance is not seen, therefore no distance can be seen. ' From what we have shown,' he says, ' it is a manifest consequence that the ideas of a space, outness, and things placed at a distance, are not, strictly speaking, the object of sight; they are not otherwise perceived by the eye than by the ear.' ^ But he had proved only that we do not see external things placed at a distance and their outness in space. It still remained, and remains even now, to be proved that the space, the outnesses, and the distances, within the sur- face of the picture painted on the retina, are not objects of sight. Therefore, he did not prove that we have no vision of space. He vacillated ; sometimes allowing, some- times denying that the extended is visible,^ and finally deciding that ' what we strictly see are not solids, nor yet plains variously coloured ; they are only diversity of colours.' ^ But the same evidence, which proves that we do not see solid distance, proves that we do see a plain, with its superficial extension and the distances on its surface. ' There is, at this day,' as he says himself, ' no one ignorant that the pictures of external objects are painted on the retina^ or fund of the eye.' * He began then with the external object and the retina. Very well ; but what is the external object, and what the retina? Both of them have surfaces. Undoubtedly the former reflects what the mathematician abstracts as rays, but what the physicist knows to be undulations, which ulti- mately impress the terminations of nervous fibres in the retina of the eye. We do not see the sides of these rays or undulations : hence we do not see distance in the third dimension. But we do see the imprints of ' Theory, xlvi. ^ Cf. ib. xliii., xlv.-xlvi., xlviii., civ. ' Ib. civiii. ■• Ib. Ixxxviii. CHAP. Mil. BERKELEY'S THEORY OF ^'ISION 231 their ends. Now, in the first place, the end of any wave of gether, however small, is a surface ; in the second place, the end of every single optic fibre is a surface ; thirdly, as a fact, no one undulation of aether ever reaches the eye alone ; and, fourthly, no one nervous fibre is excited alone, but the whole retinal surface by a whole undulatory surface of aether. Though, there- fore, the visible picture painted on the retina by the external world is not itself solid, it is painted by the surface of one solid on the surface of another. Not remote distance, but superficial extension is visible. It is unscientific in the extreme to arbitrarily select one part of the optical evidence and reject the rest, or to see through the mathematical abstractions of the line and the angle, and then to confuse mathematical points with the extended ends of physical objects. This is the mistake of Berkeley. He knows that the rays of light are not mathematical lines, yet he says at the opening and often repeats, what has been repeated after him again and again ad nauseam to the present da}^, that a point is presented to the retina. Nothing of the kind ; it is not a point, but, to say the very least, a physical ray's extended end, which is a surface, presented to the extended end of another physical object which is a surface, the end of a nervous fibre. There is, no doubt, a minimum visibile, which may be coextensive with the end of a nervous fibre ; but it is not a point, it is a surface. The whole point-to-point theory of vision is nothing but a mathematical abstraction converted into a physical reality. It is true that the retina itself may not be sensible ; but whatever part of the optic nerve or of the brain itself is first sensil)le, that part is a surface. It is true, 232 rSYCIIOLOGICAL IDEALISM part ir. ao'ain, tliat we have admitted a psychical element in sensation, hnt we can only interpret its object by con- sciousness, observation, and reasoning. We have seen the verdict of the two latter evidences : every ph3^sical part without and within us has a surface. Now, what does consciousness of vision say ? Why, I cannot help being conscious that I am at this moment seeing an extended surface. I confuse this picture within, I admit, with what I infer without ; but the scientific distinction between the external and the sensible only shows that I was wrong in the supposition of the exter- nality or remote distance of the sensible, not that I was wrong in being conscious that I see an extended sur- face, a plain variously coloured. The whole evidence, scientific and conscious, is in favour of the visible object being like a painting, or still more like a picture in a camera obscura, fiat to sense, inferred by a complex process of reasoning to represent an external solid, but confused, by a long-standing association, with the external solid itself. Again, on the second point, Berkeley proved that we do not see the real magnitude of an external object. That is no reason why we should not see the magnitude of the visible object impressed on the retina, nor why it also should not be a real macrnitude, though distinct from external magnitude. On this point, again, he vacillated. First he admits a size of things seen, that they grow greater and smaller, and that there is not only a tangible but a visible magnitude ; then he says that visible extension, though immediately perceived, is nevertheless little taken notice of; and finally contends that the ideas of visible magnitude are equally fitted to bring into our minds ' the idea of small or great, or of no size at all of outward oljjects,' like the words of a CHAr. VTii. BEEKELEY'S THEORY OF VISION 233 language.^ The trutli is, that we see an extended coloured plain, as we have already said. We are not able to alter its whole size on a single retina, because the whole retina is used at once ; and this is a great point of difference from touch, wherein we use a finger, a hand, or our whole body to touch at pleasure. The only variation we can get in the size of the whole picture is the difference of magnitude between the area of a single retina, and the whole field of vision covered by both eyes. Usually, however, both eyes are used at once, when the visible picture has a single fixed mag- nitude. But the parts of it have very varying degrees of magnitude ; for example, the black spot made by a blot of ink covers a trifling amount of the retinal mag- nitude, compared with that impressed by the white paper before me. Hence within a single visible magni- tude, fixed on the retina, we see all sorts of sizes of the parts not behind but beside one another, some greater, others smaller, and therefore having various relations of size to the whole retinal picture. It is on this sensation of varying degrees of magnitude of the parts relatively to the fixed magnitude of the whole of the superficial picture on the retina, that the w^onderful subtlety of the sense of sight is founded. In itself, this vision of magni- tude within a magnitude carries us no further ; but when allied with data of other senses, it becomes the basis of countless inferences about external size. For example, the sight of Snowdon, when I am in the open air, is smaller than the sight of my own room, when I am indoors ; but knowing in other ways the real size of Snowdon and of my room, I can from sight measure the relative sizes of parts of each in a way possible to no other sense. There is another element in the vision of ' Theory, xxviii., 1., liv., Ixi., Ixiv. 234 PSYCHOLOGICAL IDEALISM tart ii. size about wliicli we must be careful. We see the magnitude of tlie parts relatively to the whole retinal magnitude. There are minima, beyond which this de- duction of visible parts cannot go, supposed to be con- nected with the distinction of nervous fibres. But, as I said before, a minimum visihile is not a point but an ex- tended end, like the end of a pencil. Secondly, it is tempting, with Berkeley, to conclude that the minimum is always the same size in vision,^ But it is not at all impossible that the parts impressed on adjacent nervous fibres may not be always visibly distinct. In looking at an object of a single colour, as a white leaf of a book, we do not so carefully distinguish small parts as when the object is very varied, as in reading the printed matter. The minimum, impressed on each fibre, may be always the same, and yet the minima, distinctly visible, greater or smaller according to the intensity and variety of the excitations. On the whole, then, there is a visible magnitude of the picture, always of the same size, deter- mined by the retina ; visible parts, greater and smaller, in reference to the whole size ; minima visihilia, beyond which vision cannot go, but to which, perhaps, it does not in every act of vision reach. On his third point, Berkeley proved that we do not see the real situations of external objects and, in especial, that we do not see which is up and wliicli down, but an inverted image. He did not prove that sight sees no places in its inverted picture ; nor has any of the many philosophers, who have strangely attacked visible places, ever disproved them. Berkeley, as before, vacillated : he first denied them and then admitted them. He first says that a blind man returned to sight ' would not at first think that anything he saw was ' Theory, Ixxx. CHAP. VIII. BERKELEY'S TIIEOnY OF VISION 235 high or low, erect or inverted.' ^ Afterwards, he says that ' we denominate any object of sight, high or low, in proportion as it is more or less distant from the visible earth.' ^ The latter is the truth. In the visible flat extended picture, of a constant retinal magnitude, we not only see some parts greater and some smaller, but also some in one place, some in another, though all inverted. ^OT is there any occasion to suppose that the image is ever re-inverted. It includes images of our own body and of the earth. From the data of touch, we infer that our feet are down towards the earth's centre, and our heads erect as away from it ; next, we find, over and over again, that these inferred objects, in this order, have in the visible 2^icture various parts corresponding to them, in a corresponding order — one part for the earth, another for our feet, another for our heads : con- sequently, from this combined evidence of touch and sight, we do not see but infer that the part of the retinal image answering to the head represents up, and the part corresponding to the feet represents down, and so on with all other visible places. On the fourth point, Berkeley proved that we do not see and feel the same object, and that the visible picture is numerically distinct from the tactile impres- sion produced by the same external ol)ject ; e.g. my retinal picture of the paper before me is in my optic nerve, my tactile impression in my nerves of touch. But he asked the further question whether they are also specifically distinct, or whether there is anything in common, or similar, in the visible object and the tangible object. After having, though in the vacillating manner already stated, admitted in the visible picture a visible extension, visible magnitude greater and smaller, and ' Theory, xcv. -' lb. cxi. 236 rSYCirOLOGICAL idealism part 11. visible situations liigli or low in relation to visible earth, he answered the question b)^ denying that there is any- thinfr common to sio'lit and touch. The true answer is CD o that his previous admissions were better than his final theory. Vision sees a picture visibly extended in the above-mentioned ways : touch feels a tangible imprint extended in the same ways. The visible and tangible objects, so far as the former is coloured and the latter heated, are dissimilar ; so far as the former is in the optic and the latter in the tactile nerves they are not numerically the same ; but, so far as they are both ex- tended, they are similar. Aristotle was right in dis- tinguishing special and common sensibles, and in assign- ing the extended both to sii»ht and to touch. ^ Locke was right in repeating the distinction.^ Berkeley was wrong as well as inconsistent in rejecting it. But his rejection has infected the whole subsequent course of the science of vision, the metaphysics of space, and the psychology of sense. Berkeley's theory contains a double paradox. In the first place, he supposed that we see no visibly ex- tended object, when all he had proved is that we see no visibly remote object. He used the action of the external object on the retina, to prove that we do not see a line endwise, but a point ; and then discarded it when it would also prove that we do not see a point but a surface broadwise presented to the retina.^ He had no definite idea of what is meant by distance. He evidently confused it at first with the third dimension of space. ^ Afterwards, he saw that there is a visible distance between interjacent visible points.^ But he never fairly faced the fact that distance is the interval ^ De Anima, ii. 6. "^ Locke, Essay, ii. 5. ^ Tlieory, clvii. "* lb. ii. ^ lb. cxii. CHAP. viii. BERKELEY'S TIIEOKY OF VISION 237 between any places, that there is a distance in length and width, as well as in depth, and that, though distance in depth is invisible, distance in both the other dimen- sions is visible. He coolly rejected the constant appeal of the geometer to visible figures.^ He supposed a person without touch but with sight, and asked what kind of geometry he would produce ; a useless question, because man is an animal, and an animal without touch impossible. This supposititious seeing geometer would have certain limits, as Berkeley says : first, he would have no sense of a solid,''^ which requires distance in the third dimension ; secondly, he would have no sense of resistance, which requires touch. '^ He would, there- fore, infer no external world. But he would have a sense of an extended plain with its distances, the mag- nitudes of its parts, and the situations of its places. He would, therefore, see a plain, and on that plain the outnesses of the parts to one another, and their distances from one another in length and width. He would have a sense, not a science, of space. Yet Berkeley denied all these consequences of his previous admissions, assuming that an object presents a point endwise to the eye. In short, throughout the ' Essay,' the same merit is con- stantly vitiated l)y the same defect, the discovery of the invisibility of remote distance confused with the assumption of the invisibility of extended space. In the second place, he constantly asserts that what we strictly see are not solids, nor yet plains variously coloured ; they are oidy diversity of colours.'* He then defies us to assign any similitude between the visible and the tangible, and concludes that the objects of vision are not similar to external objects, but mere ' Thcorij, cl. scq. " lb. cliv. ''' lb. cxxxv. *• lb. xliii., Ixv., ciii., cxxix.-cxxx., cliii. clviii. 238 PSYCHOLOGICAL IDEALISxAI part ii. signs, like words ; so that ' the proper objects of vision constitute an universal language of the Author of nature.'^ Meanwhile, all he has proved is, that we do not see remote distance in the third dimension. Secondly, he has forgotten his constant admission that we see visible extension, visible magnitude, visible situations. Thirdly, he is plainly under the dominion of the abstraction of qualities. He says very truly that we can neither abstract the idea of visible extension from colour, nor that of colour from visible extension. But the extraordinary thing is, that he thinks this argument proves, not that we see something coloured and extended, but that we see colour, not extension.^ He is evidently under the dominion of this simple fallacy : colour is not extension ; what we see is colour ; therefore it is not extension. But in reality, though colour is not extension, what is coloured can be also extended ; what we see is a picture at once coloured and extended, and that is the reason why we cannot separate colour and visible extension, but only attend the more to colour, or the more to visible extension in the self- same picture. Hence, the visible object is not an arbitrary sign, but similar to the tangible object felt, and, we may add, to the external object inferred, in extension. The visible figure in geometry is not, in- deed, the object of the science, but it is the best illus- tration of the object to the sense and imagination of the geometer. The visible object is not like a word, and vision not like a language, which nuiy or may not be like what is signified, but the former is the sensible object, and the latter the sense, most correspondent to the extended external world, though not the most direct way of inferring it. In short, vision sees the ' Theory, cxlvii. ; cf. li., Ixiv.-lxv., cxliii. ^ lb. cxxx. CHAP. VIII. BEUKELEYS THEORY OF VISION 239 visibly extended, toiicli feels the tangibly extended, reason infers the externally extended ; and all three objects are similar, though not the same, in extension. So far, we have seen how brilliant, and how delu- sive, was Berkeley's discovery of the invisibility of remote distance, in its physical aspect. But, as we said above, he wrote the ' Theory of Vision ' also in a psychological interest. He certainly proved in it that we do not see an object at a distance ; and it is a curious problem that, after this discovery, the intuitive realists should have advanced their hypothesis that we immediately perceive the external world. The reason is that Berkeley buried his discovery under such a heap of errors, that we can hardly be surprised if the truth for a time lay hid. He found out that we do not see depth, and confirmed the theory that we do not see anything without. But he also proceeded to infer that we do not see visible space, but only various colours. Not content with this double paradox, he proceeded to another, which was indeed a main object of the ' Essay ; ' namely, that we see only visible ideas, visible ideas of colours. There is no better instance of the extraordinary way in which the assumption of idealism is made in books of philosophy, than its sudden appearance in the ' Theory of Vision.' After he has concerned himself with the external objects, and the rays of light, and the retina of the eye, we suddenly find ourselves transplanted into quite a new world with the words : ' It is evident that when the mind perceives any idea, not immediately and of itself, it must be by the means of some other idea.' ^ The invisibility of distance in the third dimension proves that we do not see external objects at a distance from the eye. The propagation of undulations to the 1 Theory, ix. 21:0 rSYCIIOLOGICAL IDEALISM tart ii. retina and the consequent nervous motion prove that we do not see external objects at all But neither evidence proves that we see something not merely within ourselves, but also within our minds, or that the visible object is a visible idea. Berkeley, however, falls into this ordinary idealistic non sequitur, without any evidence, either physical or psychological, throughout^ the ' Theory of Vision.' For instance, he says that ' a man born bUnd, being made to see, would, at first, have no idea of distance by sight ; the sun and stars, the remotest ol)jects as well as the nearer, would all seem to be in his eye, or rather in his mind.' ^ Similarly, he assumes it as agreed on all hands that colours are not without the mind, from which, of course, it would follow that neither is visible extension.^ He even uses the mere assumption that what is in the eye is in tlie mind to argue that, as the objects of sight do not exist without the mind, the pictures painted on the bottom of the eye are not the pictures of external oljjects ! '^ Meanwhile, the evidences, which are all drawn from the way in which external objects affect the retina, prove that there is a variously coloured picture produced in the camera ohscura of the eye upon the retina, but prove absolutely nothing at all about visible ideas within the mind. Let us now shortly resume what Berkeley proved and did not prove about vision as a sense. We see no remote distance, no real magnitude, and no real situa- tions of external objects ; no solidity, no resistance, no protrusion ; no outness of the world in external space : this is what he proved. He vacillated about visible extension, and finally concluded, but did not prove, that ' what we strictly see are not solids, nor yet plains ^ Theorij, xli. ; cf. xcv. - lb. xliii. ^ lb. cxvii. CHAP. VI] I. BERKELEyS THEORY OF VISION 241 variously coloured ; tliey are only diversity of colours.' Nor did lie prove that the visible object is not on the retina, nor in the optic nerve, but is a visible idea in the mind: this is 2i petitio principii committed very early in the ' Essay.' ^ Consequently, he did not prove that vision is a universal language, and that visible objects are, like words, mere signs of extended objects without being extended. The same optical evidence, which proves that we do not see remote distance endwise, proves that we do see the extended imprinted broadwise on the retina of our eyes. The visible picture, with distances not endwise but broadwise, magnitudes of parts, and situations of places, though numerically different, is specifically similar to the tangible imprint, and to the inferred original of both, in physical extension. But while Berkeley's psychological interest was en- ticing him to resolve optical effects into visible ideas, his physical discovery was at the same time forcing him to recognise external objects to cause them. At the very outset he admits the existence of a distance projecting an effect on the eye."'^ In the sequel, he allows that ' the object wliich exists without the mind and is at a distance ' is different from the visible object,^ the former remaining the same while the latter alters according to the remoteness of the eye from the external ol)ject. He talks of our advancing forward to it so many paces or miles.* He considers that it affects not only our bodies but even our minds. ' We regard,' he says, ' the ol^jects that environ us in proportion as they are adapted to benefit or injure our own bodies, and thereby produce in our minds the sensations of pleasure and pain.' ^ No realist requires more admissions. Given only the eye, and all the universe follows, bathed through- ' Theory, ix. ' lb. ii. '' lb. Iv. ' lb. xlv. " lb. lix. K 242 rSYCTIOLOGICAL IDEALISM part ii. out its mass and its molecules in that lioht which is re- fleeted from external bodies on the retina of the eye. Optics requires external bodies to reflect and a sentient body to receive light. As soon as Berkeley becomes a natural philosopher, he deserts the pure idealism of his ' Principles,' and admits between God and the ideas within our minds the intervention of ' unthinking ' objects jorojecting effects on the retina and causing visible ideas. Nevertheless, he proceeded to misinterpret the ex- ternal object. In the ' Principles,' with much consist- ency though with no truth, he emphatically denies that any sensible object, any primary or secondary quality, is anything but an idea within the mind. But in the 'Essay,' while he thought that visible objects are ideas within the mind, he identified the external and the tangible, and suj)posed that tangible objects exist without the mind. ' For,' says he, ' all visible things are equally in the mind, and take up no part of the external space ; and consequentl}^ are equidistant from any tangible thing, which exists without the mind.' ^ This view, which is entirely inconsistent with the idealism of the ' Principles,' is curiously like intuitive realism. But even if it were possible that colour and extension could be wholly separated in this manner, at any rate the identification of tangible and external ex- tension is a confusion of effect and cause. Eeally, the externally extended object is the common original of the visible and the tangible objects, both of which are within ourselves. Berkeley's identification of the external and the tangible led him into two false consequences. In the first place, it led him to deny any common cause of sight and touch. ' It is a mistake,' he says, ' to think ^ Theory, cxi. ; cf. Iv. CHAr. Till. DERKELF.Y'S THEORY OF VISION 243 the same thing affects both sight and touch. If the same angle or square which is the object of touch be also the object of vision, what should hinder the blind man, at first sight, from knowing it ? ' ^ It is true that the square felt and the square seen are not the same : one is in the tactile, the other in the optic nerves. It is true, also, that a blind man, when first restored to sight, would have a difficulty in comparing them. But this is no proof, and it is not true, that the external square object which causes the tangible square is different from the square which causes the visible square. Trafalgar Square is one object, though it is one thing to look at it and another to walk round it. It is the same crystal which presses the hand and dazzles the eye of the natural philosopher, though the modes of motion, by which it gravitates towards the hand, and by which it reflects undulations towards the eye, are different. Otherwise, science would be impossible, for it would never be concerned with one and the same object. Secondly, the identification of the external and the tangible led Berkeley into a paradoxical theory of the object of geometry. He proved, in the end of the ' Theory of Vision,' that ' neither abstract nor visible extension makes the object of geometry.' '^ But, by a false disjunctive judgment, he thought himself entitled to conclude that the object of geometry is there- fore tangible extension. This conclusion entailed the corollary that a geometrical square is really a tangible square, and is not even represented by a visible square, which, according to him, has four parts rather than four sides.^ But who ever heard of a geometer feeling a square rather than looking at one ? Through his confusion of the external and the tangible, Berkeley has entirely ^ Theory, cxxxvi. - lb. clix, ^ Cf. ib. cxli.-cxlii. R 2 244 PSYCHOLOGICAL IDEALISM tart it. overlooked the real square of tlie geometer, which is neither an abstract idea nor visible nor tangible, but an object of reasoning, capable of being partially repre- sented by a tangible square, much better by a visible square, but perfectly by neither. In elementary geo- metry, a geometrical figure is better represented by sio-lit than by touch ; even sight fails adequately to represent more complicated figures, such as a chiliagon, while in the geometry of infinites a polygon with infinite sides is a pure object of reasoning. But Berkeley's confusion of external and tangible objects needs no further criticism, for having published it in 1709, he retracted it in 1710. In his 'Essay towards a New Theory of Vision,' it was put forward as the explanation of the external object, considered by geometry, and required by optics. In his ' Principles,' ^ he calls it himself a ' vulgar error.' But he at once flew to the opposite error, and confused the tangible object Avith a tangible idea; falsely identifying the physical with the psychical, and logically but falsely resigning the external object altogether. At the same time, he insinuated that this oscillation between intuitive realism and psychological idealism made no difference. In reality, it spoilt his theory of external objects in both books. In the ' Essay,' his confusion of the external and tangible concealed from him that the external object is the common original of touch and of vision, distinct from the objects of both. In the 'Principles,' his confusion of the tangible, as well as the visible, with ideas made him omit the external object altogether. Although the object at a distance directing a line end- wise to the eye had been the foundation of his discovery of the invisibility of remote distance, he now proceeded, ' Frinc. xliv., quoted at the beginning of this chapter. CHAP. vjir. EEliKELEY'S THEORY OF VISION 245 ill defiance of the science of optics, to make visible as well as tangible ideas effects of ' the governing spirit,' with not a single word about external objects without our minds. At the price of the physical truth of the ' Essay ' he saved the psychological idealism of the ' Principles.' Berkeley, in the ' Principles,' is a logical idealist ; but Berkeley, in his works, is, like Locke, two philo- sophers in one. On the one hand, take the ' Theory of Vision.' Here he is Locke, with his admissions. Li the same somewhat half-hearted way he recognises the external objects of science : he has an undercurrent of ontology : he is a cosmothetic idealist in visible ideas which he supposes to be projected by external objects, and an intuitive realist in tangible objects which he supposes to be externally felt, as Locke, after limiting- sensation to ideas, had supposed primary equalities with- out to be objects of a kind of bastard sensation. On the other hand, take the ' Principles of Human Knowledge.' Here he is Locke, reduced to logic. He sees that mind and ideas end in mind and ideas, and that if, as Locke himself had at first said, ideas are all the objects of knowledge, then, as Locke ought to have concluded, not unthinking body but the Divine Mind is the only external cause. But Berkeley's optics were superior to his psychology. We must appeal from the ' Principles ' to the ' Theory of Vision.' ' There is,' says he in the latter treatise, ' no one ignorant that the pictures of external objects are painted on the retina or fund of the eye.' ^ Then, these external objects are not tangible, nor visible, nor sensible at all, but are causes of sensible objects, or, as ]3erkeley would say, of ideas. Not all ol)jects ' Theory, Ixxxviii. 1>4G PSYCHOLOGICAL IDEALISM part ir. of knowledge, then, are sensible ideas. Again, these external objects, whose pictures are painted on the retina, are not God, and yet are causes of sensible effects. God, then, is not the sole cause. In short, optics require, between God and our ideas, an intervening nature. The scientific admissions of the ' Theory of Vision ' are sufficient to destroy the pure idealism of the ' Principles of Human Knowledge.' Besides the optical discovery of the invisibility of remote distance, the psychological hypothesis that we see visible ideas, and the ontological recognition of the existence of an extended world without the mind falsely confused with the tangible object, the ' Theory of Vision ' finally contains a logical speculation on the origin from vision of our knowledge of the extended beyond vision. Like the main thesis, this speculation contains much that is true, and especially that we do not see but infer an external world. It is also most suggestive, and in fact was the first hint of the hypo- thesis that association may be an account of, or rather a substitute for, the origin of knowledge. But it does not in the least explain the knowledge of extended objects in the external world, required by optics and admitted by Berkeley. We must not be led away by the appearance of simplicity, but keep steadily before us the known facts to be explained, and by them test the hypothesis. We do not see remote distance : we do judge and infer it from sight : this is the essential truth in Ber- keley's theory.^ The question is, how this judgment and inference are made. He answers that when the mind perceives any idea not immediately and of itself, it must be by the means of some other idea : ^ distance, then, ' Theory, iii, * lb. ix. CHAP. VIII. BERKELEY'S THEORY OF VISION 247 is suggested to tlie mind by tlie mediation of some other idea, which is itself perceived in the act of seeing.^ He finds tliree ideas, which arise according to the different distances of objects : the first, the lessening or widening the intervals between the pupils of our eyes, attended with a sensation ; "^ the second, the more or less confused appearance ; the third, the prevention of this confusion by straining the eye, witli its sensation.^ These are the ideas which he thinks will suggest the idea of the distance of the external object : not that there is any natural or necessary connection of those ideas with distance, but that there is an habitual or cus- tomary connection between these ideas and the idea of distance.* This process implies that the idea of distance itself has been acquired in some other way. This way, according to Berkeley, is touch combined with motion. He gives the whole process in the following passage : — ' Having of a long time experienced certain ideas perceivable by touch, as distance, tangible figure, and solidity, to have been connected with certain ideas of sight, I do upon perceiving those ideas of sight, forth- with conclude what tangible ideas are, by the wonted ordinary course of nature, like to follow. Looking at an object I perceive a certain visible figure and colour,*^ with some degree of faintness and other circumstances, which from what I have formerly observed, determine me to think, that if I advance forward so many paces or miles, I shall be affected with such and such ideas of touch.' ^ This process, l)y which visible ideas suggest tangible ^ Theory, xvi. - lb. xvi. ^ lb. xxvii. * Cf. ib. xxviii. with the above sections. ^ Note this admission of visible figure as well as colour. ^ Ib. xlv. 248 rSYClIOLOGlCAL IDEALISM part ii. ideas of distance, is what is ordinarily called association. Berkeley describes this operation with great clear- ness. ' That one idea,' he says, ' may suggest another to the mind, it will suffice that they have been observed to go together, without any demonstration of the ne cessity of their co-existence, or without so much as knowing what it is that makes them so co-exist.' ^ There is such an operation, and its recognition was not new in philosophy. Plato and Aristotle, Hobbes and Locke were aware of it. Aristotle, for instance, says that we recollect from what is similar or contrary or con- tiguous.^ But what was new in Berkeley's ' Theory of Vision ' was the hypothesis, afterwards developed by Hume, that this process of recovering ideas is some- times the analysis of what we call knowing objects. The ordinary man, when he uses his eyes, supposes that he knows, nay sees, that there is an external object at a distance from him. Berkeley tells him that he is really letting visible ideas suggest to him tangible ideas of distance ; that is all. There is a negative value in Berkeley's analysis. It is greatly superior to the ordinary supposition that we see a distant object. Berkeley, though he exaggerated when he said that we do not see any distances at all, showed conclusively that we do not see but infer a distant object in the external world. It is also superior to the supposition of ' Descartes and others ' ^ that Ave infer the distance of objects from the angles they make with our eyes. Berkeley disposed of this ' humour of making one see by geometry,' when he showed that the lines and angles between the external objects and the eyes are as invisible as the external 1 Theory, xxv. ^ j)^ ^g,,,_ 2 = 451 B, 18-20. ^ Theory, iv. not CHAP. viii. BEliKELEY'S THEOKY OF VISION 249 objects themselves.^ Mathematical opticians had fallen into the blunder of supposing that lines and angles, known only to themselves by science, are sensible data which ordinary men use in vision to infer an external world. There is also positive information in Berkeley's analysis. It contributed some new truths on the senses. In the first place, about sight ; he did not indeed show that there is no vision of space, but he did show that it is in a way unnecessary. He called attention to the scientific observation of the misfortune of the blind, who have no eyes, yet feel and infer space. Again, his remark, that no resistance is perceived by sight, con- tains the true reason why from sight alone we could not infer an external world, and therefore must appeal to touch and motion. Lastly, though it is not the case, it is possible that sight might, like hearing, or, at any rate, like language, contain no apprehension of extension, and yet enable us, when combined with a sense of exten- sion, to infer an extended object. On the whole, he has not shown that the visible object is not an extended picture ; but he has shown that, whatever the visible object is, we can know an extended object in the external world without it, and not by it alone. Secondly, he has the great merit of having hinted, however imperfectly, at what is now called the muscular sense. When he speaks of ' the motion of his body which is perceivable by touch,' ^ though he may be ex- aggerating its connection with touch, he is recognising a sense of motion. He also saw that in vision there is something more than seeing. What he calls ' lessening or widening the intervals between the pupils,' which is ' attended with a sensation,' is the convergence or diver- ^ Theory., iv., xii., lii. liii. ^ lb. xlv. 250 PSYCHOLOGICAL IDEALISM part ii. gence of the optic axes by the internal and external recti muscles, with their muscular sense. When he speaks of the confused appearance caused by objects brought too close to the eye, and of preventing the appearances growing more confused ' by straining the eye,' and of its sensation,^ he is pointing towards the increase of the convexity of the crystalline lens, for the more rapid convergence of rays from near objects to the retina, by the action of the ciliary muscle, with its muscular sense. He also refers to the movements of the eyes up and down, to the right and left, which are performed by the four i^ecti muscles.'^ In none of these cases did he analyse the muscular movements or assign them a distinct muscular sense. Nevertheless, he called attention to movement, to the sense of movement in touch, and to the sense of some kind of action in sight, connected with the knowledge of extension. At the same time, these great achievements are quite consistent with equally great blunders about our senses, of which there are two, at opposite extremes. On the one hand, he underrates the efficacy of vision when he tends to confine it to visible ideas of colour ; on the other hand, he exaggerates the efficacy of touch when he tends to extend it to external objects. Eeally, the former is the vision of the extended in the optic nerves, the latter is the feeling of the extended in the tactile nerves. However, these errors do not touch the exact question before us. Whatever else it may be, the object of vision is certainly not the external object at a remote distance. Now, the question is whether, when we say that there is such an external object, cor- responding to what we see, we are only letting visible ideas suggest tangible ideas of remote distance. ' TJieory, xxi. xxvii. ^ lb. xcvii. xcviii. CHAP. Mil. BERKELEY'S THEORY OF VISION 251 In solving this problem, two concessions must be at once made. In the first place, from vision, being no sense of resistance, We do not infer the external world directly, but only indirectly through touch and motion. Secondly, visible ideas do suggest tangible ideas, and other ideas also for that matter, by the customary tie of association, which is a real fact of human nature. But we must also ask ourselves wdiether this suggestion is all that happens. If so, we should only have the ideas ; we should not infer that, over and above the ideas, the object seen corresponds to an extended object in the external world. Eor example, at this moment, my vision of the white would suggest my tangible idea of the extended ; but I should not infer, as I really do, that over and above the tang-ible idea there is an ex- tended paper in an external world, corresponding both to the object of touch and the object of sight. Berkeley substituted the suggestion of ideas for the inference of external objects. Even in the ' Theory of Vision,' in spite of having admitted the existence of the external object, and its action on the retina, Berkeley partly accepted the consequence. ' Sitting in my study,' he says, ' I hear a coach drive along the street; I look through the casement and see it ; I walk out and enter into it ; thus common speech wou'd incline one to think, I heard, saw, and touch'd the same thing, to wit, the coach. It is nevertheless certain, the ideas intermitted by each sense are widely different, and distinct from each other ; but having been observed constantly to go together, they are spoken of as one and the same thing,' ^ Similarly, he afterwards says that, though the objects are different, as they are called by the same nauie, he will, to avoid ' Theory, xlvi. 252 PSYCHOLOGICAL IDEALISM part ii. tediousiiess and singularity of speech, speak of tliem as belonirino- to one and the same thinoj.^ Now, it is quite true that the audible, visible, and tangible are different objects, and also that, if nothing ]ia])pened except that ideas of the audible and visible sug- gested ideas of the tangible, no real identification could take place. But something further does take place. In the first place, when I hear something sounding in my auditory, see something coloured in my optic, and feel something hard in my tactile nerves, and have often ex- perienced these sensible oljjects in a similar order, I infer that there is one external object, which is the common original of these sensible objects on any given occasion. Secondly, I call this common original by one and the same name, ' coach,' because I infer it to be one thing. It is true that I have an habitual tendency to confuse the one external object with the several and different audi- tory, visible and tangible objects within me. But it is not true that there is no identity but an identity of name. There is an identical external object, the coach, which I infer, and which I can disene^age from the con- fusion with its different sensible results, by means of science. Now, if the auditory, visible and tangible objects had been mere ideas in my mind, and if these ideas merely suggested one another, I could never have inferred the one external object, and it is most im- probable that I should have even called the different ideas by one name. But I do infer one external object, and am justified by optics and other sciences connected with the senses. Therefore, in the first place, the pro- cess of this inference of one external object cannot be a mere suggestion of different ideas ; and secondly, the data of this inference of an external object cannot be ^ Thcurij, Iv. CHAP. Tin. BERKELEY'S TIIEOEY OF VISION 253 auditory, visible and tangible ideas. In reality, from physical data in the several nerves, I infer one physical coach, and give it, not them, one name. In the 'Theory of Vision,' however, Berkeley did not fully realise the consequence of reducing the infer- ence of external objects to the suggestion of tangible ideas, because he combined this association of ideas with an intuitive touch of external objects. Hence, later on, he says of a man, that ' when he has by experience learned the connexion there is between the several ideas of sight and touch, he will be able, by the perception he has of the situation of visible things in respect of one another, to make a sudden and true estimate of the situation of outward tangible things, corresponding to them. And thus it is, he shall perceive by sight the situation of external objects, which do not properly fall under that sense.' ^ Such an estimate would require the impossible iden- tification of tangible ideas, tangible objects, and out- ward things. But, in the first place, touch does not feel the outward thinfT. Secondlv, a visible idea suggests a tangible idea, but not a tangible ol^ject. Thirdly, what we really do is to estimate the situation not of a tangible idea, nor of a tangible object, but of an outward thing corresponding on the one hand to the tangible, on the otlier hand to the visible, object within ourselves. We cannot bolster up the association of ideas by an intuitive touch of outward things. In the ' Principles,' when he had retracted the con- fusion of the external and tlie tangible, and the intuitive touch of the external, the consequence of supposing that the inference from vision is nothing l)ut an associa- tion of ideas came out in its simple nakedness. He ^ lb. xcix. 254 PSYCHOLOGICAL IDEALISM tart ii. then saw that, in lliis case, ideas of sight only admonish us what ideas of touch will be imprinted on our minds, and do not mark out to us things actually existing at a distance.^ I freely admit that Berkeley was right in retracting the tansfible intuition of the external world, and tliat if we start with visible ideas, and by the suiTirestion of ideas let these visible su^rfrest tangible ideas, and have no tangible intuition of extended objects in the external world, we shall begin and end in ideas. But we do not end in ideas. His own optics require that we know external objects, and that no one is ignorant of their painting pictures on the retina of the eye. His h3qoothesis of the suggestion of ideas does not account for the knowledge of their causes. It is, therefore, false. The cause of Berkeley's error was that neglect of logical inference which made its appearance in the Second Book of Locke's ' Essay,' and led to the postpone- ment of reasoning to all kinds of lesser powers. Like Locke, Berkeley was aware of the difference between association and reasoning.^ But, like Locke, he kept in the background, and to the last, reasoning, the one power which will be heard and will not wait. Hence, in the ' Principles,' he supposes that ideas suggest ideas, until reason at last infers a God. Hence, in the ' Theory of Vision,' he substitutes for inference a false touch of out- ward things and an imperfect suggestion by visible of tangible ideas. He overlooks in both the human, though complex, inference of an external extended object which causes both sight and touch. The ' Theory of Vision ' contains the discoveries of ^ Princ. xliv., quoted at the beginning of this chapter. ^ Cf. Locke, Essay, ii. 33, 13 ; Berkeley, The Theory of Visual Language Vindicated, § 42. CHAr. viir. BEKKELEYS THEORY OF VISION 255 the invisibility of remote distance, and of the combina- tion of sight and touch with a sense of motion. It is a very good answer to those who say that we see the external world ; though even they could retort on Berkeley that he says himself that we feel it. It is no answer to those who say that we know the external world. It is a good answer to those who say that we infer it directly from sight by lines and angles, or by any other direct inference, from sight, M^hich feels no re- sistance. But it is no answer to those who say that we infer an external extended world first from the resistance felt in the senses of touch and motion, and then from the correspondence in extension between inferred, tan- gible, and visible objects. Finally, Berkeley's ' Theory of Vision ' contains two fundamental errors of omis- sion : the first, that there is no vision of an extended object within ; the second, no inference of an extended object without, common to our senses of sight and touch. 25G PSYCHOLOGICAL IDEALISM tart ii. CHAPTER IX. HUME. The academical or sceptical pliilosopliy of Hume admits of being smmnarised as follows. All the perceptions of the mind are impressions and thoughts or ideas. ^ All our ideas or more feeble perceptions are copies of our impressions or more lively ones.^ Association is a principle of connection which, by resemblance, con- tiguity or causation, on the appearance of a perception suo^gests thoughts or ideas. ^ All the objects of human reason or inquiry may naturally be divided into two kinds, to wit, Relations of Ideas and Matters of Fact. Of the former kind are the sciences of geometry, algebra, and arithmetic, and, in short, every affirmation which is either intuitively or demonstratively certain.* The origin of our beliefs, i.e. vivid ideas, of matters of fact, is experience of a constant conjunction of impres- sions, and association wliich, from this constant con- junction, begets such a connection in the imagination that, on the appearance of the antecedent, we have the idea, i.e. belief, of the consequent and of their connection as cause and effect.^ The mind has never anything present to it but the perceptions, and cannot possibly reach any experience of their connection with objects. The supposition of such a connection is, therefore, with- ^ Inquiry, ^"1. "-Vo. ^Ih.^^. ^ lb. § 4. ' lb. §§ 4-7, esp. § 7, Part II. CHAP. IX. HUME 257 out any foundation in reasoning.^ The great subverter of Pyrrhonism, or the excessive principles of scepticism, is action.'^ There is, indeed, a more mitigated scepticism, or academical philosophy, which may be both durable and useful, and which may, in j^art, be the result of this Pyrrhonism or excessive scepticism, when its undistin- guished doubts are, in some measure, corrected by common sense and reflection.^ The point of this academical philosophy is that man has the faculties to receive impressions and conceive ideas or thoughts ; and by association to make vivid ideas of causation, which are his only beliefs on matters of fact ; but not ];)y reasoning to infer exter- nal objects. Hume published it twice over, first in the 'Treatise of Human Nature,' afterwards in the 'Inquiry concerning Human Understanding.' The earlier work is more elaborate, containing in the First Part a fuller discussion of the origin of ideas, modelled on the Second Book of Locke's ' Essav,' but with the stress laid on asso- ciation ; in the Second Part, a theory of the apprehen- sions of time and space, which hardly appears at all in the later work ; in the Third Part, a longer but less elegant exposition of his theory of association as the origin of the belief in causation ; and in the Fourth Part, a long discussion of the apprehension of objects, answering to the last section of the ' Inquiry,' but com- prising a sceptical theory of substances, both material and thinkinif, which he ai'terwards omitted but l)y no means retracted in his later work. Since the 'Treatise' was published when tlui author was a young man of twenty-seven, the 'Inquiry' ten years later in the prime of life, the impartial critic must dwell mainly on the more 1 Inquiry, § 12, Tart I. - lb. § 12, Tart II. ^ lb. § 12, Part III. S 258 PSYCHOLOGICAL IDEALISM i>ARr ii. mature work ; especially as in his account of ' My own Life ' Hume says himself, ' I had been guilty of a very usual indiscretion in going to the press too early ' — a useful warning to youthful philosophers. Nevertheless, the essence of both ' Treatise ' and ' Inquiry ' is the same : it is a reduction of man to mere perceptions. Berkeley had attacked natural science : it remained for Hume to attack the human intellect. But we must take care not to be argued out of our wits. Hume's philosophy is founded on the following distinction of perceptions into impressions and ideas, which he identifies with thoughts : — ' Here, therefore, we may divide all the perceptions (jf the mind into two classes or species, which are distinguished by their different degrees of force and vivacity. The less forcible and lively are commonly denominated thoughts or ideas. The other species want a name in our language, and in most others ; I suppose, because it was not requisite for any, but philosophical purposes, to rank them under a general term or appella- tion. Let us, therefore, use a little freedom and call them impressions ; employing that word in a sense some- what different from the usual. By the term impres- sions, then, I mean all our more lively perceptions, where we hear, or see, or feel, or love, or hate, or desire, or will. And impressions are distinguished from ideas, which are the less lively perceptions, of which we are conscious, when we reflect on any of those sensa- tions or movements above mentioned.' ^ The distinction between impressions and ideas is an important discovery, or rather re-discovery. Aristotle had, in the 'De Anima,' carefully distinguished between cesthemata, or the objects in sense when an external ob- ject is present, and phantasmata, or their relics in the ^ Inquiry, 5 2. CHAP. IX. HUME 259 imagination when the external object is absent. But, as we have akeady seen, Descartes afterwards confused the object of sensation and conception under the name ' idea,' and Locke and Berkeley had followed him. So long as it was admitted that some external object is also known, this confusion had no very serious conse- quences ; for the reduction of sense to a purely psy- chical object at all was a far more fundamental error than the reduction of this psychical object to an idea. But when it began to be doubted whether any external object could be known, it then became a serious ques- tion, how we can distinguish an adventitious idea im- printed on the senses from a fictitious idea generated by the imagination. Berkeley felt this difficulty,^ and got over it partly by supposing that adventitious are more vivid than factitious ideas, but mainly by his theory that the former are directly inspired by God. Xow, Hume doubted our knowledge of any cause of our per- ceptions, natural or spiritual. Moreover, he saw that ' the word idea seems to be commonly taken in a very loose sense by Locke and others, as standing for any of our perceptions, our sensations and passions, as well as thoughts.' ^^ 1\\ these circumstances, he revived the ancient distinction of cesthema and phantasma under the new names ' impression ' and ' idea,' yet without resorting either to matter or to God. As he says in the ' Treatise,' ' By the term of " impression," I would not be understood to express the manner in which our lively ideas are produced in the soul, but merely the percep- tions themselves.' ^ Consequently he had to look out for some fresh criterion to distinguish the thing as well as the term, and found it in the liveliness of an impres- ' Princ. xxxiii. - Inquiry, § 2, note. ^ Treatise, i. § 1, note. s 2 2G0 PSYCHOLOGICAL IDEALISM part ii, sioii as contrasted with an idea. In tlie 'Mietoric,' Aristotle had described, without meaning to define, iniao-ination as a kind of weak sense. ^ Hobbes had exahed this description into a definition — ' Imagination being (to define it) amception remaining, and by little and little decaying from and after the Act of Sense.' ^ Berkeley had made faintness a partial test of an idea of imairination : Hume exalted it into the sole criterion, and committed himself to the consequences. ' The most lively thought,' says he, ' is still inferior to the dullest sensation.' The hypothesis that there is no more distinction between sense and imagination than between vivid and faint perceptions, or states of consciousness, as they now call them, has become a favourite with modern idealists, simply because they have destroyed the real criterion afforded by the presence and absence of exter- nal objects. But there is a difTerence in kind between sense and imagination, of which 'different degrees of force and vivacity' furnish no adequate criterion. The faintest impressions M^ould be undistinguishable from the most vivid ideas. This objection Hume had noticed himself in the ' Treatise,' and tried to evade it : — ' The common degrees of these are easily distin- guished : though it is not impossible but, in particular instances, they may very nearly approach to each other. Thus, in sleep, in a fever, in madness, or in any very violent emotions of soul, our ideas may approach to our impressions : as, on the other hand, it sometimes hap- pens that our impressions are so faint and low, that we cannot distinguish them from our ideas. But, notwith- standing this near resemblance in a few instances, they ' Ar. Bhct. i. 11 = 1370 A, 28. ^ Hobbes, Human Nature, chap. iii. § 1. CHAP. IX. HUME 2G1 are in general so very different, that no one can make a scruple to rank them under distinct heads, and assign to each a peculiar name to mark the difference.' ^ The conclusion of this passage exhil)its a common practice of trying to get round a contradictory instance. It is true that, on the whole, the livelier would be dis- tinct from the fainter perceptions, but there would still be a mari^in between the livelv and the faint, which, in the absence of any other criterion, it would be arbitrary to place among either impressions or ideas. But there is a still more fatal objection : some ideas are livelier than impressions, and would have, by the bare criterion of lively and faint, to change places with them. Yet Hume, to save his theory, has to say that ' all ideas, especially abstract ones, are naturally faint and ob- scure,' while ' all sensations, either outward or inward, are stroncr and vivid.' ^ But abstract ideas of mathe- maticians are often brighter than their concrete impres- sions, as in the case of the mathematician who in a fit of abstraction held the egg in his hand while he boiled his watch. Ideas of men in disease are often so vivid as to be mistaken for impressions. The artistic imagina- tion is sometimes stronger than ordinary sensation, as Handel, on being asked how he wrote the 'Hallehij;ih Chorus,' said, ' I did see all heaven before me, and the great God Himself.' This superior vividness of imagination is finely de- scribed by Addison : — ' Words, when well chosen, have so great a force in them, that a description often gives us more lively ideas than the si Critique of Pure Reason, ed. Hartenstcin, p. 33 = Mciklejohn's translation (Bohn), p. 1. Ueberweg's summary of tlie Criti:D NECESSARY TRUTHS 349 with other objects. This power is sometimes called intuition. But it is not intuitive any more than a priori. It requires sense, general reasoning, and rational ab- straction ; nor is this rational abstraction always perfect ; but when it is perfect it is a simple apprehension of the nature of the object. An analytical judgment is one which divides a simple object of perfect abstraction into subject and predicate. When we have thus got the entire content from general reasoning, and have abstracted simple objects, an affirmative analytical judgment simply divides the same simple object into subject and predi- cate by, not from, the principle of identit}' — a thing is the same as itself. This operation must be carefully guarded from misapprehension : there is no mystery about it. In the first place, it is not merely concerned with a common name, nor with an abstract idea, but with an object in the abstract, discovered by reasoning, isolated by perfect abstraction, and divided into subject and predicate by analysis. Secondly, it is not, as usually described, an analysis of the subject of the judgment into the predicate, which would deprive the latter of its content, but an analysis of the simple object isolated by perfect abstraction into subject and predi- cate, as the object and its nature. Thirdly, it adds nothing to the abstraction, but, as the abstraction iso- lates the simple object from the synthesis of general reasoning, so the analysis divides this simple object into subject and predicate. For example, having discovered that things which are wholes contain their parts, and having by perfect abstraction isolated a thing qua whole as merely a sum of its parts, the analytical judgment simply asserts this result of perfect abstraction in the form of a judgment, for the purpose of making demon- 350 PSYCHOLOGICAL IDEALISM part ir. strations from it. Indeed, Aristotle was not wrong in saying that there is a simple apprehension of simple objects, though he ought to have added the analyti(,'al judgment,- because it is as a judgment that the appre- hension becomes a principle of demonstration. Fourtlily, the analytical judgment is made spontaneously by the l)rinciple of identity, which is the law of its form, but not deduced from the principle as a premise. It has nothinfT a rniori about it, beins^ derived from sense and general reasoning, through perfect abstraction, by ana- i^ysis, adding nothing but the division into subject and predicate, not independent of experience, but only re- quiring no new experience ; in short, a priori only in the old sense of indirectly a posteriori. Aneo-ative analytical judgment is of the same kind, but one degree more complicated. General reasoning from sense infers that white objects are not black, that sweet objects are not bitter, that square objects are not round, and so forth. Perfect abstraction isolates the different objects and causes a simple apprehension of their natures as different. In the case of simple objects of sense, such as sensibly white and sensibly black, perfect abstraction is applicable, because the objects are so simple, and the abstraction simply apprehends the sen- sibly white as containing nothing black, and vice versa. In the case of other objects, such as things which are square or round, the abstraction, to become perfect, requires the neglect of many extraneous circumstances, in order to apprehend a thing quel square containing nothing round, and vice versa. A negative analytical judgment, thereupon, divides the objects differentiated in the abstract as subject and predicate of a negative judgment, a sensible object qua white is never black, a thing qua S(iuare is never round. Its principle is that CHAP. X. KA^'T■S 'CRITIQUE' AND NECESSARY TRUTHS 351 of difference, that wliicli is the same thing is not different, or two different things are not the same, or, in its more developed form, the principle of contradiction. But this law of the form of a negative anah'tical judgment is not an a priori major premise from which any analj'tical judgment is deduced, except in metaphysics and logic as sciences. Perfect abstraction and analytical judgments are not unlimited. Quantitative objects are more capable of abstract isolation than qualitative, in the narrow sense of this word. Perhaps no precise limit can be marked out, but we may lay down the general rules, that with the power of isolating a simple kind of object and apprehending its nature, abstraction ceases to be perfect, and, when perfect abstraction fails, analytical judgment is no longer possible. Thus we can perfectly abstract a thing qua whole, and judge analytically that so far it is greater than its part ; perfectly abstract the sensibly white from the sensibly black, and judge analytically that so far one is not the other. On the other hand, when we come to so complicated an object as external light, we can no longer apprehend in isolation what light is as light, but must accumulate its facts and infer that its nature is undulative by the method of explana- tion. Hence two origins of definition : perfect abstrac;- tion in exact science, explanation of properties in other sciences. An abstract science is one wliicli attends to an object, so far as characterised in some particular manner : an exact science is one in wliicli this abstract attention is ])erfect. An analj'lical is the same as a self-evident judgment, and its necessity is self-evidence. If all other things are possible, it is at least impossible that a thing should not be the same as itself, or be the same as something; 352 rSYCHOLOGlCAL IDEALISM part it. cliHerent. Not metaphysics but perfect abstraction gives this internal necessity to analytical judgments. But metaphysics justifies it by analysing the analytical axioms of identity and difference, and affords a technical description, by which, if we are asked why a whole, for example, is greater than its part, we can answer because a thing qaci whole is the same as the sum of its parts, because otherwise it would not be a whole, and because to deny it would be a contradiction in terms. But such a deduction is purely metaphysical. Nor is it a valid objection that the ordinary man could not apprehend the necessity of his analytical judgments unless he knows the axioms, for he is in the same position about ordinary deduction, where he plainly knows the logical necessity of the inference, without knowing the axioms which it requires. Analytical judgments, then, are self-evident, without being deduced a priori from their axioms. This self-evidence has several special characteristics. In the first place, we have no apprehension of it till we apprehend the objects, but directly we apprehend them in the abstract we at once accept the analytical judgment. Hence it is that there are many men, and even nations, who have never heard of the very judg- ments which to others are self-evident. The former have not, the latter have, performed the necessary abstraction. A man who has not thought of a thing as a whole has no acquaintance with the judgment, the whole is greater than its part ; no sooner has he thought of it qua whole, than he asks for no proof of the axiom. The analytical theory of principles is the only one which accounts for this extreme contrast between ignorance and certainty. Secondly, self-evidence gives to analytical judgments a universal applicability. They CHAr. X. KANTS 'CRITIQUE' AND NECESSARY TRUTHS 353 are not liable to the difficulty of synthesis, that an exception may be found to the combination of two kinds of objects ; a difficulty which, Kant confesses, aj)plies even to a priori synthesis beyond objects of experience. In an analytical judgment there is only one kind of ob- ject, which must be the same as itself and different from other things, wherever it is found. Thus the synthe- tical judgment, a whole thing is greater than its part, is liable to the exception that a thing may sometimes have no parts ; but the analytical judgment, a thing so far as it is a whole is greater than its part, can have no exception, because qua whole it is only a sum of parts. Thirdly, self-evidence makes analytical judgments con- vertible or coextensive ; so long as a thing is a whole it is greater than its part, and as soon as it ceases to be greater than its part it ceases to be a whole. We can even say that such a judgment is of eternal application ; for, even if things ceased to be wholes, it would still be true that they would be greater than their parts if there were wholes. Hence, there could not be another world ill which a whole would not be greater than its part, for it could not be a whole ; nor can any really self- evident or analytical judgment be reversed. Such is the outline of a realistic theory of self- evident analytical judgments a posteriori, of which the points are, first, that such judgments are not always about names and conceptions, but also about objects of sense and reason ; secondly, that we discover the oljjects by general reasoning from sense, by perfect abstraction apprehend a simple kind of oljject, and analyse it into subject and predicate by, not from, the principles of identity and difference, or contradiction, a posteriori ; thirdly, that analytical judgments are self-evident to one who has abstracted the objects, universal without A A 354 PSYCHOLOGICAL IDEALISM . part ii. exception, and convertible ; and, fonrtlily, that analy- tical judgments about objects of reason in tlie abstract are sometimes principles of science. As analytical principles are self-evident, conclusions logically deduced from them are necessary, though not self-evident, and the process of deduction from self- evident principles is demonstrative. There are two kinds of necessary truths : self-evident principles and demonstrative conclusions. Again, there are two kinds of deduction, which may be distinguished as empirical and demonstrative, provided we remember that demon- stration is indirectly empirical. In the last chapter we discussed empirical deduction from induction, which, though formally necessary, is materially only as pro- bable as the induction on which it is founded. In the present chapter we have added that deduction is not always limited by the probabilities of induction, but, when mediated by perfect abstraction, and starting from analytical self-evident principles a posteriori, is demonstrative of necessary conclusions. There are, therefore, two kinds of knowdedo-e : one consistinfj of induction and deduction, combined toocether in cir- cumstantial evidence, with various degrees of proba- bility up to approximate certainty ; while the other starts in the same manner, but by the perfect abstraction of a simple, non-synthetic object, such as a thing qua whole, a body qua solid, a body quel moving, &c., obtains self-evident analytical judgments, from which deduction demonstrates conclusions, materiallv as well as formally necessary. The former is science ; but the latter is exact science. Kant in the ' Critique,' and Mill in his ' Logic,' both recognised analytical judgments and their self-evidence, but the former was deceived by conceptualism and the CHAP. X. KANT'S 'CRITIQUE AND NECESSARY TRUTHS 355 latter by nominalism, and accordingly botli fell into the common error of excluding analytical judgments from principles of science. In order to answer them, we have only to remember that the axiom, the whole is greater than its part, is confessedly an analytical judg- ment, and certainly a primary major premise in mathe- matical demonstrations. Hence it is not a mere analysis of conceptions, still less the mere meaning of a name. It is the analysis of an object of general reasoning iso- lated by a perfect abstraction of a thing qua whole as a sum of its parts. This analytical a posteriori axiom, being a real principle, is a sufficient contradictory in- stance to destroy both the theory in Kant's ' Critique ' that all mathematical principles are synthetical a priori^ and the synthetical a posteriori theory in Mill's ' Logic' Major est vis instantice 7iegativce. We found that Kant starts his argument by the position that necessity and strict universality are not inductive. This position is common ground. After and beyond induction, Aristotle introduced an intelligent understanding of principles, purposely to explain their necessity. ' Necpie tamen,' says Bacon, ' etiam in uni- versalibus istis propositionibus exactam aut absolutam affirmationem vel abnegationem requirimus.'^ Newton, in the fourth ' Eegula Philosophandi,' with which he opens the Third Book of the ' Principia,' acknowledges that in- duction is only valid ' donee alia occurrerint phscnomena.' Similarly, all that Mill contends is that ' whatever has been found true in innumerable instances, and never found 1o he false in any, we are safe in acting on as universal provisionally until an undoubted exception appears ; provided the nature of the case be sucli that a real exception could scarcely have escaped notice.' ^ More- 1 Nov. Org. ii. 33. - Mill, Logic, iii. 21, 4. A A 2 356 rSYCIlOLOGICAL IDEALISM r\KT n. over, it is pcatent, from tlie limitation of liiiman expe- rience to some instances ont of all, that the induction of all must end in probability, however great. The difference between Kant and Mill begins with the contention of the latter that there are no truths more necessary than those mere probabilities of induc- tion which seem necessary to us only through insepar- able association. But, in the first place, Mill is not true to his own position, because, as we saw before, he acknow- ledges ' the original inconceivability of a contradiction ' ; though, like other philosophers, he passes lightly over this negative instance destructive of his theory that association is the origin of all ideas of necessity. Secondly, he ought to have gone further than mere inconceivability. Analytical principles of science are such that the contradictory is not only inconceivable in idea but impossible in belief, because it is incredible that a thini? should not be the same as itself. Now Mill admits, on the one hand, that the impossible is different from the inconceivable, and, on the other hand, that association is limited to the inconceivable. As, then, association is no origin of principles, whose contradictions are impossible, and as self-evident ana- lytical judgments are such j)i'biciples, it follows that their necessity cannot be due to association of ideas. Moreover, if the axiom, the whole is greater than its part, were a synthetical a posteriori judgment, dis- covered by mere induction, with a mere idea of necessity due to association, there would be two ideas, one of which would suggest the other ; but there is only one idea of one kind of object which is analytically judged to be identically a whole and greater than its part, Association, in fact, is no origin of the real and iden- tical necessity of an analytical principle, which is self- ciiAr. X. KANTS 'CRITIQUE" AND NECESSARY TRUTHS 357 evident. There are, tlien, necessary truths of \Yhich the opposites are neither mere iniprobabihties of in- duction nor mere inconceivabiUties of association, but incredible impossibiUties of existence ; namely, self- evident analytical judgments. Kant then was right in repeating after Leibnitz that there are necessary judgments in the sciences ; thereby he eliminated their synthetical a posteriori origin. But he did not thereby eliminate their analytical a posteriori origin ' Necessity and strict universality are, there- fore,' says he, ' sure signs of a knowledge a priori' That ' therefore ' is a rash word. ' Baculus stat in angulo ; ergo pluit.' There is another alternative. Because the necessary is not inductive, it does not follow that it is straightway a priori. Necessity is a soluble and not an infallible siQ'u, because there is another source of necessity, namely, self-evident analytical judgments a posteriori. But Kant was misled by Leibnitz into think- ing that analytical judgments were a piiiori. Hence his non sequitur from the inductive to the a priori. Hence also the importance of showing, as I have attempted to do, that analytical judgments are a pos- teriori, real, and necessary principles. It is to found a theory of necessity without mysticism. Kant, in fact, eliminated analytical judgments from the position of scientific principles, only in the concep- tualistic a priori shape into which, under Cartesian influences, they had been thrown by Leibnitz. He did not eliminate them in the realistic a posteriori light in which they were rightly regarded by Aristotle. Not all necessary truths are a priori, because self-evident necessary truths are a posteriori. Not all necessary principles of science are synthetical judgments a priori, because some analytical judgments a posteriori are 0'58 rSYCIlOLOGICAL IDEALISM tart ri. necessary principles of science. Tlie anal3^tical axioms, the whole is greater than the part, if equals be added to equals the wholes are equal, if equals he taken from equals the remainders are equal, have a reality in things, and an a posteriori origin, and a position among Euclid's principle^, which contradict the fundamental hypothesis of Kant's ' Critique,' that all necessary jjrinciples of science are synthetical judgments a priori. Kant might reply that, though some analytical judgments may be principles, they do not carry us far ; and that most principles at all events are synthetical judgments a priori ; such as 7 + 5 = 12 in arithmetic, and a straight line is the shortest between two points. But Kant was, to say the least of it, unfortunate in his instances. The proposition, 7 + 5 are 12, is not an arithmetical principle, but a demonstrative conclusion ; and the shortest distance between two points is so far from being the geometrical definition of a straight line that it is not geometrical at all, being merely that property of a straight line which is of most importance in mechanics. The definition of a straight line would require an investigation of space and geometry. I will only remark at present that Euclid's definition is at all events geome- trical, and it is unsatisfactory only because he attempted to define a line without a superficies, committing a blunder common with systematisers of previous dis- coveries, that of beginning too S3^nthetically. A point is only definal)le by abstraction from a line ; and simi- larly, a line from a surface, a surface from a solid, in the manner indicated, though not completely developed, by Dr. Simson in his Notes to the First Book of Euclid. A straight line also requires this analytical treatment. It has been for centuries perfectly abstracted ; but, as CHAP. X. KANT'S 'CKITIQUE' AND NECESSARY TRUTHS 359 often happens, it has been over-abstracted, and will never be successfully defined until it is anal3^tically approached from its place in a superficies. But arith- metic comes before geometry : a unit is simpler than a point, a number than a magnitude. As Aristotle remarked, and Comte repeated, a science from fewer data precedes a science which adds more.^ Accordingly, the question of necessary truths ought to be contested in the simpler and more universal science of arithmetic. The arithmetical principle concerned with the number 12 is 11-f-l, which is its sole and sufficient definition. If we were to take 7 + 5 for a definition, 12 would have infinite definitions by the addition and subtraction of other numbers, none of which would be of any further use, because to use a number in a sum we must know out of what number it is formed by the addition of a unit. In the case of 12, 11 is that number which by the addition of 1 makes 12, as 10 is the number which by the addition of 1 makes 11, and so on till we come back to 1 + 1 are 2. All those arithmetical principles, which are definitions of numbers, are founded on the units added together ; as the Greeks knew perfectly well when they said that the unit is the origin of ninn- ber, and number is multitude composed of units.^ The discovery of abstract numbers is a good instance of the process of abstraction and analysis I have been describing in this chapter. By sense and reason we find that objects are one and many and wholes, among other of their attributes, and infer that one object is always undivided, many are divided into units, and a whole is greater than its part. We thus discover truths of num- ber. But how do we apprehend their necessity ? By perfect abstraction we isolate an oljject qud one as undi- ' Ar. Post. An. i. 27. "^ Eucl. VII. Def. 2. 300 rSYCIIOLOGICAL IDEALISM taut it. vided ill quantity, objects qud two as one H one, &c., &c. This abstraction is necessary to tlie science of arithmetic. As Phito, thongli lie did not nnderstand abstraction, long ago pointed ont,^ concrete units are not altogether undivided ; a man, for example, is many in his members and only one on the whole ; but an arithmetical unit is absolutely undivided. Why ? Simply because the thing as divided is neglected, and attended to only as undi- vided, by perfect abstraction. On this abstraction of the unit, not as a mere conception, but as a simple object of attention, we have, not a priori, but by a posteriori analysis, the analytical judgment, which is the definition of a unit : not, be it remarked, the con- tingent proposition, one thing is the undivided in (piantity, which is not always true ; but a thing qud one is the undivided in quantity, which is self-evidently necessary. So far as a thing is one, it is undivided in quantity, and so far as it is divided in quantity, it is no longer one. This analytical definition is the foundation of all arithmetical definitions, all of which are merely analyses of numbers into units ; thus 1 -h 1 are 2 ; 2 -I- 1 are 3, and so forth ; every one of which are analytical definitions. Hence, though 7-1-5 is not, 11 -I- 1 is, the analytical definition of 12. All things, qud 11 -H 1 are 12, and qud 12 are 11-f-l. Mill, indeed, contends that there is a difference between 2H-1 and 3, because 'three pebbles in two separate parcels, and three pebbles in one parcel, do not make the same impression on our senses.' '"^ But he overlooks the fact that, when three pebbles are in two separate parcels, if they give us the impression 2 + 1, this is the impression 3 without any comparison with three pebbles in one parcel ; and conversely, when three 1 Plato, Rej). vii. 525 D-G B. ^ Mill, Logic, ii. 6, 2. CHAP. X. KANT'S 'CRITIQUE' AND NECESSARY TRUTHS 3G1 pebbles are in one parcel, if tliey give us the impression 3, this is the impression 2^1, without any comparison with three pebbles in two parcels. We do not require two sets of three objects each to count 2 and 1 are o. The truth is that he was deceived by the formula 2 + 1 = 3, in which, for mere convenience, we apply to number the geometrical sign for equality of two magnitudes ; but we must not allow this mere symbol to make us think that we are always comparing different quantities on each side of it; in arithmetic, equality means identit}^, and the correct arithmetical formula is 2 + 1 are 3. Kant, on the other hand, did not even take the definition of the number 12, which, as we have seen, is 11 + 1, but one of its many properties, 7 + 5. He rightly says that the proposition, 7 + 5 are 12, is not analytical : 12 is not the selfsame thing as 7 + 5, because it is 8 + 4, &c. But this proposition, though not analytical, is also not a principle, but a demonstrative conclusion from principles which are analytical, the definition of the unit and the definitions of the numbers up to 12, as 11 4 1 ; and we are able from these analytical to demon- strate synthetical judgments, by that combination which we found in the last chapter to be the essence of syllogism or deduction. Kant's attempt to prove that the prin- ciples of arithmetical demonstration are not analytical by the instance 7 + 5 are 12, is an ignoratio elenchi, be- cause this proposition is not a principle, but a demon- strative conclusion from analytical principles, including 11 + 1 are 12. It is curious what a cursory attention is paid to arithmetic in Kant's 'Critique' and Mill's 'Logic' But by looking a little more closely into this most fundamental of all special sciences, we have found that it contains analytical principles a posteriori both in the axiom, the 3G2 PSYCHOLOGICAL IDEALISM pakt ii. Avliole is greater than its part, and in its delinitions. Thus we can destroy both the synthetical theories. On the one hand, as these })rinciples, being self-evident, are snch that the contradictory is impossible, Mill is wrong in reducing arithmetic to the mere probability of induction and association. He quotes, indeed, with approval a supposition that there might be a ""A^orld, in which, whenever two pairs of things are contem- plated together, a fifth thing is brought within con- templation, and the result to the mind of contemplating two two's would be to count five.^ But it is absurd to suppose minds contemplating a fifth thing without counting it in the enumeration, and jet to end the sum, as if thev had counted it, with the number 5. Either one would count the fifth tliinij in which case the sum would be 2 + 2 + 1 are 5, or one would not, in which case the sum would be 2 + 2 are 4. There can be no world in which the result to the mind of contemplating two two's would be to count five, because 2 + 2 are de- monstrably 4, and 4 + 1 are identically the same as 6. On the other hand, as necessary arithmetical principles are a posteriori analytical judgments, we cannot follow Kant in passing from the synthetical a posteriori to the a priori synthetical theory ; for a definition, such as 11 + 1 are 12, is discovered by empirical reasoning, and by perfect abstraction and analysis becomes a self-evi- dent principle, whereby 7 + 5 is 12 are demonstrated. Finally, if we were to surrender entirely the anal}^- tical a p)osteriori origin of necessary truths, yet the synthetical a priori origin is an untenable hypothesis, because it does not explain the facts. Let us take for granted the Kantian series of arguments : the neces- sar}^ is not inductive, therefore it is a priori ; there are ' Examination of Hamilton'' s Philosojihy, chap. vi. note. CHAP. X. KANTS 'CRITIQUE' AND NECESSARY TRUTHS 3G3 necessary principles in the sciences, therefore they are a priori ; analytical judgments are merely a 2?riori ana- lyses of conceptions, but principles of science are true beyond conceptions, therefore they are never analytical judgments : but if they are neither synthetical a poste- riori, nor analytical a priori, all principles of science are synthetical a p)riori. Now, everywhere throughout the ' Critique,' Kant confesses that the a priori is contri- buted by mind to mental representations, and that the data of mental representations, without which the a priori is mere conception, are sensations, which the a priori converts into objects of knowledge. Hence he concludes that perception, experience, understanding, reasOninriori elements. Hence, according to him, necessary principles of science, being synthetical a priori, are necessary within, but impossible without, the sphere of sense and experience. Kant everywhere accepts this consequence : synthetical principles a priori are necessary, and apply, only within the limits of pha^nomena.^ This corollary of transcendentalism maybe illustrated by its application to arithmetic. According to Kant, arithmetic will contain analytical a priori axioms — for example, the whole is greater than its part — which, however, will not be principles ; and synthetical prin ciples a priori, an example of which will be 7 -f- 5 are 12. He did not, indeed, leave a satisfactory theory of the place of number in his system. There is a sentence in the ' Critique ' '-^ in which he says ' that nuuilK'r is no- thing but the unity of the synthesis of the manifold of a homogeneous intuition in general, gained by my gene- 1 Hart. 57, 152-3, '208 = Meik. 44, 119, 177. ' Hart. 144 = Mcik. 110. 3 04 PSYCHOLOGICAL IDEALISM parx ii. rating time itself in the a]:)preliensiou of tlie intuition ; ' that is, apparently, by generating a successive addition of units in time. The same view is confirmed by a passage in the ' Prolegomena to all Future Metaphysics.' ' Geo- metry,' says he, ' is based upon the pure intuition of space. Arithmetic accomplishes its concept of number by the successive addition of unities in time.'^ This, however, is a conclusion so paradoxical, that we may in charity suppose him to concede that we also apprehend contiguous units in space. But even so, space and time alike are regarded by him merely as a priori forms of sense and of sensible pheenomena. Moreover, the cate- gories, schemata, and principles of quantity are all confined by him to phaenomena. The consequence is that number is strictly limited to phsenomena, and even the synthetical principles a priori of arithmetic are re- garded b}^ Kant himself as necessarily true of phasnomena of sense, and no more. Hence his extraordinary state- ments, ' nwnerus est quantitas phenomenon,' and ' ceternitas, necessitas, phasnomena,' &c.'^ But is it true that the laws of number are limited to the phasnomena of sense ? The very first definitions of Newton's ' Principia ' disprove such a narrow theory. ' The quantity of matter is the measure of the same arising from its density and magnitude conjointly : ' this is the first definition, which is immediately illustrated by the arithmetical proposition that ' air of a double density in a double space is quadruple, in a triple space sex- tuple,' while this quantity of matter is identified with its mass. ' The quantity of motion is the measure of the same arising from the velocity and quantity of matter conjointly : ' this is the second definition, which ^ Prolegomena (translated by Mahaffy), p. 45. - Hart. 146 = Meik. 113. CHAP. X. KANTS 'CRITIQUE' AND NECESSARY TRUTHS 365 is again elucidated by the arithmetical illustration, that ' in a body, double in quantity, motion with equal velocity is double, with double velocity quadruple.' If, now, arithmetic were limited to the phaanomena of sense, the laws of mass and motion would either have to be limited to the pha^nomena of sense, or, beyond the phasnomena of sense, contain no quantity of matter or of motion, no measure, no numerical proportion ; both of which alter- natives are absurd. The truth is that the laws of mass and motion carry us far beyond the ph[Enomena of sense into a non- phoenomenal yet scientific world of material particles, and carry the laws of arithmetic with them. The law of gravitation is a law of motion by numerical propor- tion. All the particles of matter gravitate to one an- other with a force directly as their mass, and inversely to the square of the distance ; on the one hand, this gravitation is inferred to be in numerical proportion both to the quantity of matter and to the distances of the particles ; on the other hand, every particle of matter in the universe is inferred to gravitate with this numerical proportion, in times, places, and circumstances, wholly inaccessible to any possible senses of living beings. In the laws too of the structures and motions of imperceptible particles, all the definitions and axioms of arithmetic are employed. For example, in a drop of water, every thousand of tlie imperceptible particles with another particle makes one thousand and one, and is a whole including every one of these particles as parts. 'In rebus enim,' says Bacon, ' quos per numeros transiguntur, tarn facile quis posuerit aut cogitaverit millenarium, ([uam uniim ; aut millesimam partem unius, quani unum integi-iiin.' ^ As Mill remarks, ' the ^ Bacon, Nov. Org. ii. 8. 366 rSYCIIOLOGJCAL IDEALISM part. ii. great agent for transforming experimental into deductive sciences is the science of number.' ^ We can neither allow that these deductive sciences, which measure the structures and motions of imperceptible particles, are limited to phasnomena of sense, nor that there is any measure of quantity available except number. But we need not go beyond the ' Critique' itself to see the impossibility of limiting lunnber, the quantitative categories of unity plurality and totality, and arith- metical principles, to phtcnomena. One of the points of the ' Critique ' is that God is not a phtenomenon. But God is one. Therefore unity is not limited to plias- nomena. Kant also assures us that we have a unity of apperception, an identical self, which is supposed by him to be not a phgenomenon, but that which unites phaenomena. Lest we should suppose that these objec- tions prove only unity and not number beyond pha3- nomena, he distinguishes for us the human understand- ing with its unity of apperception to combine sensible representations from the divine understanding, which does not require it.'^ There are, therefore, according to Kant, who was innocent of the Hegelian identifica- tion of similars and confusion of divine and human, two understandings, the divine and the human, numeri- cally different, yet neither a phgenomenon. God, he also tells us, does not make a whole with the world ; there are, therefore, three things — God, the world, and human understanding ; none of them pha^nomena. All things are at least numbered, whether they be material or spiritual ; hence the dispute, whether Kant ought to have made luimber belong to space or to time, is completely beside the mark, for it belongs to every- thing whatever. It is impossible, therefore, to confine ' Mill, Logic, ii. 4, 7. - Hart. 119, 123 = Meik. 85, 89. CHAP. X. KANT'S 'CRITIQUE' AND NECESSARY TRUTHS 367 number, aritlimetic, or arithmetical necessity to plias- nomena of sense. What is the consequence ? Not all necessary principles are limited to phasnomena. Con- sequently, again, they cannot be synthetical judgments a priori, which, on Kant's own confession, would limit them to phasnomena. In other words, the syntlietical a priori theory does not account for arithmetical neces- sity, the simplest and best instance of scientific neces- sity, beyond phaenomena in an imperceptible world. Arithmetical principles apply to everything what- ever. After all, there is only one theory which can account for this absolute universality of arithmetic, which counts subjects as well as sensations, men, bodies, cor- puscles, and God Himself. There is not one arithmetical judgment limited to phgenomena any more than to ideas. Now, this could not be, if they were analytical a priori, which would limit tliem to ideas, nor synthetical a p)0S- teriori, which would make tliem contingent, nor syn- thetical a priori, which would make tliem necessary only within the limits of phasnomena. But it can be, if they are analytical a posteriori judgments about simple objects of reasoning in the abstract. Either, then, this theory must be accepted, or some new tlieory found. Ihit where? When we look back on the whole discussion of this difficult subject, we shall fmd that there is no evidence for the Kantian hypothesis o? a priori synthetical judg- ments, as the origin of necessary truths, except its advantage over the synthetical a posteriori and the analytical a priori theories. It has no direct evidence, either from consciousness or from anatomy, and it is not only that we are unconscious of a priori necessity, but that we are unconscious of any a piriori power, or of anything like it. In indirect evidence it also fails. It 368 PSYCHOLOGICAL IDEALISM part ii. does not attempt to eliminate an analytical a posteriori theory, altliongli sncli a tlieory, as I have shown, can readily be developed from the works of Aristotle. But what finally condemns it, and makes it quite impossible, is its confessed inability to explain even the logical in- ference, much more the scientific knowledge, of neces- sary truths beyond the phjenomena of sense ; when, as a matter of fact, in all the sciences, and not onlv in mechanics and all natural philosophy, but also in psy- chology and theology itself, insensible and imj)ercep- tible objects are logically inferred and known to obey the necessary laws of unity, plurality, and totality. Every- thing known is one ; not everything a phaanomenon. What makes so many philosophers at this moment cling to an hypothesis so utterly wanting in verification, elimination, and explanation? Partly, no doubt, its superiority to the hypothesis of Mill. But two blacks do not make a white ; and it makes little difference wdiether we say that association makes us necessarily conceive, or a priori synthesis necessarily believe, the necessity of principles within the phasnomena of sense, when the real question is how we infer their necessity in insensible and imperceptible nature, and in the super- natural world. Partly, it is thought that the Kantian tlieory of necessity must be accepted, because other parts of the ' Critic [ue ' seem to support religion. But we must beware of building the house of religion on the sand ; and religion can hardly be sup2:)orted by a philosophy, which makes it a fallacy to say that God is one. The main cause of the popularity of Kant's philosophy, however, seems to be founded on the vague use of the term ' pha^nomena,' which suggests to the unwary all the facts in lieaven and earth, sensible, in- sensible, and imperceptible. But this is not what Kant CHAP. X. KANT'S 'CRITIQUE' AND NECESSARY TRUTHS 369 meant, nor what he could mean, by phasnomena, and it would be a sad pity to rest the reputation of a philosophy on an equivocation. As Leibnitz before him spoke of ^ phcenomena sive apparitiones quse in mente mea existunt,' ^ so Kant always speaks of them as sensible representations which cannot exist out of our mind ; opposing them to nou- mena, or things of which we must form ideas, but which as objects are unknown. He was aware that his philosoph}" compelled him to make these sensible repre- sentations the limit of knowledge, not merely because they are the matter of sense, but also because a priori forms of mind cannot be valid beyond a posteriori data of mind. Moreover, as we find from the Preface to the Second Edition,^ he looked upon it as one of the ad- vantages of his ' Critique of Pure Eeason,' so to limit speculative knowledge to pha^nomena that ' we can have knowledge of no object as a thing in itself, but only so far as it is an object of sensory intuition, i.e. as manifes- tation,' because thereby he thought to make room for a practical proof of the freedom of the will beyond the area of pha3nomena. Kant, then, in limiting all speculative knowledge to phsenomena, meant that necessary truths, being synthe- tical judgments a priori, are only necessary about the a priori forms of sensible representations and about sensible representations converted into objects of know- ledo;e by these a priori forms. Such a limitation to things of sense, Sinnenwesen, phsenomena, is ftir too narrow, because arithmetical necessity applies to every imperceptible object of logical reasoning and scientific knowledge. His fundamental position, that necessity is ' Leibnitz, Op. (etl. Erdmann), p. 442, A. ^ Hart. 22 scq. = Meik. xxxii. scq. B B 370 PSYCHOLOGICAL IDEALISM takt ir. au infallible sign of a priori knowledge, must be tra- versed by this still more fundamental position : imper- ceptibility is an infallible sign of a logical inference and a scientific knowledge wliicli is neither pheenomenal nor a priori. Kant's ' Critique of Pure Eeason ' is a conspicuous instance of the failure of the synthetic method, and indeed of the impossibility of carrying it out con- sistently. He supposes himself to use the origin of knowledge to determine the limits of the objects known. Accordingly, on this synthetic method, he begins with sense, at once begs a sense of sensible representations, and thus founds his philosophy on an hypothesis which dictates the conclusion that knowledge is limited to phgenomena. On the other hand, every one of his main arguments takes a premise from the other end of know ledge, its objects, and, by an analytic method, uses the objects to infer an a priori origin of knowledge. Thus, in the Introduction, necessary truths about objects of science are used to deduce the theory of synthetic judgments a priori ; in the ' Transcendental -3^stlietic,' from their known properties space and time are inferred to be a priori forms of sense ; in the ' Transcendental Analytic,' a definition of the objects of knowledge is used to prove that they contain a priori categories of under- standincr. Nor is this all. Havin^f taken as much about an object as he wants for his a priori theory, Kant then, by his synthetic method, uses his a priori theory to dis- pose of the rest of the oljject. Thus, he argues that necessity requires synthetical judgments a priori, which again prove necessity phsenomenal ; that the properties of time and space require a priori forms of sense, which again prove time and space phaenomenal ; that known objects require a priori categories, e.g. substance and CHAP. X. K A XrS 'CRITIQUE' AND NECESSARY TEUTIIS 371 cause, wliicli again prove known objects, e.g. substances and causes, plisenomenal.^ The ' Critique ' is a perpetual see-saw between two methods ; the professed from the origin to the objects, and the concealed from the objects to the origin of knowledge. It is first synthetical, then analytical, and finally synthetical. It assumes as a principle that the matter of sense is representations. But this synthetic beginning would not justify transcendentalism. It then argues that the objects of knowledge require a priori elements. Now, this analytical procedure gives trans- cendentalism a momentary plausibility. It finally con- tends that a posteriori representations converted into objects by a priori elements are the objects of experience, and that all objects of logical inference and knowledge are phainomena. But this synthetical ending brings transcendentalism into conflict with a characteristic of the objects of knowledge, omitted in the analysis ; namely, that they are not limited to pluenomena. It is as if a natural philosopher should show that the theory of emission explains reflection and refraction, and then deny the interference of polarised liglit. So Kant shows that the a priori theory explains the necessity of synthetical truths, and then denies their universal applicability ; shows that it explains the properties of time and space in, and then denies them beyond, sense ; shows that it explains the experience of objects, and then denies the knowledge of objects beyond experience. lie arbitrarily appeals to some of the characteristics, but neglects the insensibility, of objects of science. His whole method is ad placitum. He makes origin and objects, objects and origin, origin and objects, recipro- cally determine one another, in a perpetual circle. » Hart. 22, 80, 123-4, 133-4, &c. = Mcik. xxxiii. 44, 90, 100, &c. B B 2 372 PSYCHOLOGICAL IDEALISM part ii. The analytic method, used consistently, makes com- plete havoc of the ' Critique.' ' Tempus, spatium, locus, et motus sunt omnibus notissima. Notandum tamen, quod vulgus quantitates hasce non aliter quam ex relatione ad sensibilia concipiat.' ^ In this passage, Newton points out that the limitation of the objects of science to the sensible is a vulgar error. Yet it is a constant error of mental philosophers, who think that, when they have considered only objects of sense, they have solved the secret of the scientific universe. It was the very error of Kant when he called time and space forms of sense, and therefore limited motion to sense ; when heenunciated the extraordinary series of paradoxes : ' numerus est quantitas plijenomenon, sensatio realitas plia3nomenon, constans et perdurabile rerum substantia phasnomenon, ceternitas, 7iecessitas, phseno- mena, &c.' ^ ; when he concluded that whatever is known is a phasnomenon, and what is not a phsenomenon can be conceived by pure reason, but neither inferred by logical reason nor scientifically known. This philosophy, secun- dum sensum, was an hj^pothetical corollary from the theory that all objects of experience are sensible repre- sentations informed by a priori intuitions and notions of mind. But as certainly it is false, because it cannot explain a millionth, nor even an infinitesimal, part of the insensible objects of science. Let us return from the ' Critique of Pure Eeason ' to the ' Philosophio3 Naturalis Principia Mathematica,' and enlarge our thoughts, not to the immensity of the unknown, but to the extent of the objects of science, such as was made known by ISTewton, Felix, qui potuit rerum cognoscere causas. Insensible corpuscles of matter are scientifically inferred ' l^ewton, Princijna, Dcf. Scholium. '^ Hart. 146 = Meik. 113. CHAP. X. KANT S 'CRITIQUE' AND NECESSARY TRUTHS o7o to be each one, many and numbered, and to obey tlie necessary laws of number ; to be in insensible time and space, and to obey the necessary laws of magnitude ; to be insensible substances, and move according to the laws of motion ; to be insensible causes of insensible motions, and to be insensible causes of sensible objects. They are actual, but they are not actual pha^nomena of sense, but insensible external causes of internal sensible ef- fects. Nor, being actual, are they possible phaenomena ; for possible, which are not actual, phasnomena are nothing at present, whereas the insensible particles of a drop of water, now gravitating towards my hand, are actual at present, real because causal of effects in my senses, and at the same time not only insensible but imperceptible ; so far from possibilities, impossibilities of sensation ; yet actual objects of science. The irresistible conclusion of this consistent and thorough appeal to the objects of knowledge, is that not all of them are phienomena, actual or possible, but far the larger part non-plia3nomenal, noumenal in the sense of rationally inferred, known things in themselves, as apart from our senses, though not as apart from their relations to one another. The weight of natural philosophy is destined to destroy all that mental philosophy of the present day which begins from a sense of sensations, even if it makes a vain effort to recover its false start by catching at the shadow of a priori mysticism. When Kant pro- poses to convert sensible representations of minds into objects of knowledge by a priori intuitions and notions of minds, he all the more limits scientific inference to pluenomena. But, as we have just seen, the objects of scientific inference include insensible and imperceptil)le things, which are not plucnomena, actual or possible. 374 PSYCHOLOGICAL IDEALISM part it. Therefore, in tlie first place, tlie ' Critique ' is incredibly narrow and absolutely false in limiting scientific infer- ence to phenomena, actual and possible ; and secondly, the data of scientific inference cannot be sensible re- presentations, even sublimated by a priori forms, which all the more surely would condemn science to the nar- row limits of phosnomena. Finally, we must apply consistent analysis to the Kantian arguments in detail. Thus, if necessary truths were synthetical judgments a priori, they would be limited to phenomena ; but science extends them to all particles of matter ; therefore, they are not limited to pha^nomena, and therefore are not synthetical judg- ments a priori. Secondly, if time and space were such as to be necessarily a priori forms of sense, they would be limited to pha^nomena ; but science infers that they are forms of every particle of matter in the universe ; therefore, they are not limited to phenomena, and therefore they are not a priori forms of sense. Thirdly, if objects were such as to require a priori categories of substance and cause, they would be limited to pha?- nomenal substances and causes ; but science infers that all particles of matter are substantial bodies, causing and receiving motions, acting and reacting on one an- other, inert until moved or resisted by one another, and, among countless effects, producing sensible objects in us ; therefore, objects scientifically inferred are not pliEenomenal substances and causes, and, therefore, sub- stance and cause are not a p)riori categories. In short, objects of scientific inference are not pha3nomena, and could not be inferred from a posteriori sensations con- verted into objects by a priori forms. Critical idealism is a false philosophy, both of the limits and of the origin of knowledge. vt' CHAP. X. KANTS 'CRITIQUE' AND NECESSARY TRUTHS 375 The one beacon of the present day is scientific dis- covery and invention : it was lighted by the principles of the Newtonian philosophy. But though natural philo- sophy will reveal to us nature, and provide us external goods, it will not alone produce philosophical wisdom or constitute essential happiness. What we want is principles in general philosophy. Wlien such princi- ples have been found, it will he discovered that there was a time when the details of nature were not so well known, but the general relation of God, nature, and man was much better understood than at present. We may laugh at the want of knowledge, but we must never forget the wisdom of the ancients. The stream of human discovery has been like a river, part of which escapes into marshes, while the main channel flows on into the sea : so philosophy, the perennial sources of which are to be found in Greek philosophy and sciences, speculative and practical, has in modern times been partly diverted into the marshes of idealism, while the main stream has expanded into the natural philosophy of Copernicus and Kepler, Bacon and Galileo, Descartes and Newton, and perpetually issues in discoveries and inventions. Can we bring mental philosophy back into the main stream of discovery ? We can, by using the discoveries of natural philosophy as objects of science to discover the data of sense. Idealism has failed because it has used a wrong method, and begun at an unknown be- ginning. It has taken psychical data of sense for prin- ciples, which are really hypotheses, and has used them to dictate the objects of knowledge. As it has found new ditriculties, it has feigned new hypotheses, until it has culminated in the absolute idealism of Hegel, who, by heaping hypothesis on hypothesis, — sensible repre- 370 PSYCHOLOGICAL IDEALISM part it. sentations, a jmori categories, one spiritual subject in God and all men, of which nature is a system of objective thoughts — compiled a system of philosophy which is as cumbrous a mass of hypotheses as the Ptolemaic system of astronomy. But the truth is, that, like the old hypothesis of planetary circles round the earth, the modern idealistic hypothesis of a sense of psychical data, whether called ideas or impressions, representations or sensations, is a false beginning, and could never lead to scientific knowledge. Modern astronomers succeeded by reversing the method of astronomy. They gave up reasoning synthe- tically from hypotheses of planetary circles to the de- tails of planetary motion, and began with the planetary motions as facts. Copernicus found that the planets move round the sun, and Kepler that they move not in circles but in ellipses : proceeding from these facts, Newton inquired analytically what simple motions were required to explain such elliptical motions : this was the analytical method which ended in Newton's discovery of astronomical principles. In the same way mental philosophy should reverse its method. Instead of reason- ing synthetically from hypotheses of sensible data to what objects we can and must know, we should find what we do infer and know in the sciences, and then inquire analytically what sensible data are required to explain our hiference and science. In this way, and no other, as Newton by an analysis of elliptical motions discovered the principles of astronomy, so may we by an analysis of the objects of scientific reasoning dis- cover the principles of mental philosophy. There is one characteristic of objects scientific, which is at once a positive instance to bring us to principles of mental philosophy, and a negative instance CHAP. X. KANT S 'CRITIQUE' AND NECESSARY TRUTHS 377 to destroy all psj'chological idealism : it is tlie insen- sibility of corpuscles. Corpuscles, insensible and imper- ceptible substances in time and space, moving according to laws of motion, are physical objects of science, requiring physical data of sense. On the one hand, consider this analytical deduction destructively. In the first place, it follows that these insensible and imperceptible objects of scientific inference are not sensible ideas, not perceptions, not phasnomena, nor unknown things. This consequence destroys the ideal- isms of Berkeley, Hume, and Kant. Secondly, these in- sensible and imperceptible objects of scientific inference could not be logically inferred from ideas, nor from im- pressions, nor from sensible representations converted into phsenomenal objects by a priori forms. This destroys the idealisms I have examined, from Descartes to Kant. Nor could they be inferred from any sense of sensations, however elaborated. This destroys the idealisms of our own day. On the other hand, consider this analy- tical deduction constructively. These insensible and imperceptible objects of scientific inference require a sense, from which reason may infer them by parity of reasoning. Hence, in the first place, sense is simple and synthetic ; perceiving substantial objects, which are internal but physical, durable, extended, and related to one another, within our nervous systems. Secondly, reason infers similar objects and relations in external nature. Tliere are three types of inference, analogical, inductive and deductive, each mechanically obeying its own laws, and primarily from judgments of synthetic sense inferring judgments about objects insensible and imperceptible. General reasoning, inductive and de- ductive, used circumstantially, produces a knowledge and science with an approximate always tending to 378 PSYCHOLOGICAL IDEALLSM part ir. an absolute certainty. After sense and general reasoning, perfect abstraction by attention, mechanically obeying tlie laws of identity and difference, makes us apprehend a kind of object as simply the same with itself, and frame analytical judgments of what it must be and not be, in the abstract. These analytical judgments are self- evident principles of demonstration, producing exact science, but a posteriori. This is a general outline of the analytical philosophy attempted in this essay. Among many difficulties, which may occur to others, I anticipate three main lines of objection to this essay. In the first place, it may be thought that, what- ever value physical realism may have in dealing with nature as an object of scientific knowledge, idealism retains an advantage of its own in its treatment of man as a spiritual subject. On the contrary, against Des- cartes and all his followers, but from the consilience of consciousness, observation, and reasoning about myself, I contend that man is an organism, partly body and partly soul ; who knows of himself, on the one hand, that he is an animal, inhabiting the surface of no very large planet in a considerable solar system, which is only one among countless stellar worlds, in a stupen- dous immeasurable universe ; and, on the other hand, that, infniitesimally little as he is in himself, by sense and reason he is great, in his knowledge and power over nature, which make him like even to God. But, reasonable as is this realistic, but not materialistic, con- clusion, the idealists more and more tend to the hypo- thesis, that man is a purely psychical self, while his own body is not an integral ^^art of himself, as subject, but is one among all other known bodies, which, as objects, are either all alike inferred from, or all alike identical with, his sensations or thoughts in general. CHAP. X. KANT'S 'CRITIQUE' AKD NECESSARY TRUTHS 379 Now, the former of these aUernatives leaves out half the man ; the latter inverts man and nature ; while both idealistic theories of personal identity, by draw- ing the line of self at spirit, or between soul and body instead of between man and nature, contradict the con- silience of consciousness, observation, and reasonino- : a combined evidence not to be parted, because man is a complex being, mainly imperceptible to himself, who by night falls asleep and becomes oblivious of his being, by day does not remember his infancy, never can remember nor as yet be conscious of his future career, and, therefore, is not aware of his personal iden- tity throughout life by retentive consciousness alone. Why, then, does modern thought tend towards idealistic spiritualism ? Partly from a want of simplicity and a certain vanity of man, who in his rationality would fain forget he is an animal ; mainly from a confusion of idealism and spiritualism with Christianity. But we have the best possible authority on the Christian doc- trine of man himself: the words of Christ incarnate. ' And He said unto them, why are ye troubled ? and wherefore do reasonings arise in your heart ? See My hands and My feet, that it is I Myself : handle Me, and see ; for a spirit hath not flesh and bones, as ye behold Me having^.' ^ Secondly, it will be doubted whether my general theory can be worked out in detail. I feel the full force of this difficulty. When this essay was mapped out it was to include many more details. Starting from Newton's ' Principia,' I had hoped to include a theory, long cherished, that the properties of time and space, enunciated by him in the ' Scholium to the Defmitions,' can only be explained by defining time and space as ' St. Luke xxiv. 38-39 (Revised Version). 380 PSYCHOLOGICAL IDEALISM PART II. the continuance and continnity of tlie universe, tlie former being the continual duration, tlie latter the continuous extension, of the universe as one substance including many substances, from a star to an atom. From the same starting-point, I hoped to show that a necessary physical cause of motion is any body which displaces or resists any other body, as demonstratively following from the impenetrability of matter, by which two bodies cannot at the same time occujjy the same place in space, and that again from the analytical judg- ment that a body as solid is extended in three dimen- sions. Moreover, I had hoped to apply the analytical a jiosteriori theory of necessit}^ to geometry by starting from the definition of a solid. I have also written chapters, which are in print, on possiljle phsenomena, and on actual realities, in order to show at length that scientific objects cannot be resolved into the former. These were to be followed by a discussion of ideas, including a criticism of Hegelianism, written but not printed. I have in print chapters on touch and on vision, directed against the doctrines of ' local siijns,' further developing the views in my criticism of Berke- ley's ' Theory of Vision,' and also based on the argu- ment that a sense of place is necessary to a sense of motion. Finally, I meant to have revived the logic of a method, which appears in Aristotle, but has fallen out of logic. I mean the analytical deduction from effect to cause, which appears to me to be the com- monest method of science, because man knows facts before and better than causes. But seeinsj that all these matters would have made at least another volume, and fearful of becoming tedious, I also felt that I had already claimed as much attention as could be hoped bv an untried author. CHAP. X. KANT'S 'CRITIQUE' AND NECESSARY TRUTHS 381 Thirdly, it will be said that I have exaggerated the power of sense. . This is a difficulty I do not feel or allow. The emasculation of sense, which is the most fundamental defect of modern philosophy, is a result of a bygone anatomy. It was formerly thought that the five senses were inlets, passages, or pores through which sensible effects were received within us, according to some, to the heart, according to others, to the head. In these circumstances, it was excusable to suppose that such poverty-stricken organs contributed nothing but isolated data, which the soul worked up within into all sorts of relations. But all that is changed now. It has been discovered that the senses are highly compli- cated nervous structures ending in the brain, that the brain is an integral organ of sense as well as of reason, and that the whole nervous system has been for count- less generations hereditarily modified by its operations, and, on the whole, better adapted to j)erform more and more complex operations. Since these discoveries, I submit that there is no bar to supposing that so wondrous a sensitive structure, as a brain and a system of sensory nerves has become, is an organ of simple and synthetic sense of objects and relations, internal and physical, as I have suggested. But I do not merely rely on anatomy. My main trust is in the philosophy of science. Science proves the power of man to know nature. But logic also proves the weakness of mere reason, which, without adequate data of sense, is consistency, not science. Eeason cannot logically infer insensible objects and relations in external nature, unless there are sensible objects and relations in our internal nature for sense to perceive. Hence, to provide adequate data for the parity of reasoning, I suppose a simple and synthetic 382 rSYCUULOGlCAL IDEALISM part ii. sense of physical objects and relations witliin the ner- vous system. 1 hope, Ijy this means, to have done "what I could to physic two diseases of modern idealism — the separation of reason from nature, and the divorce of reason from sense. 'Jlie leal problem of philosophy is not how to form ideas, nor how to escape from them to things ; it is not to start wdtli sensations, and ask how nmch, by association, we can conceive but not know, nor how much, by a priori elements, we can know, of mere phagnomena. What are the adequate data of sense, and what the logical processes of reason- ing, which enable science to infer an insensible and im- jjerceptible world. These are the questions for psycho- logy and logic to ask about sense and reason. ' Itaque,' in the words of Bacon, ' ex harum facultatum, Experi- mentalis scilicet et Eationalis, arctiore et sanctiore f(jedere (cjuod adlnic factum non est) bene sperandum est.'i ' Nov. Orfj. i. 95. APPENDIX. UEBEBWEG'S SUMMABY OF THE 'CBITIQUE." By the critique of the reason Kant understands the exami- nation of the origin, extent, and limits of human knowledge. Pure reason is his name for reason independent of all expei-ience. The ' Critique of the Pure Reason ' subjects the pure speculative reason to a critical scrutiny. Kant holds that this scrutiny must pi"ecede all other philosophical procedures. Kant terras every philosophy, which transcends the sphere of experience without having previously justified this act by an examination of the faculty of knowledge, a form of ' Dogmatism ' ; the philosophical limita- tion of knowledge to experience he calls ' Empiricism ' ; philoso- phical doubt as to all knowledge transcending experience, in so far as this doubt is grounded on the insufficiency of all existing attempts at demonstration, and not on an examination of the human faculty of knowledge in general, is termed by him ' Skepti- cism,' and his own philosophy, which makes all further philosophis- ing dependent on the result of such an examination, 'Criticism.' Criticism is ' transcendental philosophy ' or ' transcendental idealism ' in so far as it inquires into and then denies the possibility of a transcendent knowledge, i.e. of knowledge respecting wh;it lies beyond the range of experience. Kant sets out in his critique of the I'eason with a twofold division of judgments (in particular, of categorical judgments). With reference to the relation of the predicate to the subject, he divides them into analytical or elucidating judgments— where the predicate can be found in the conception of the subjt^ft by simple analysis of the latter or is identical with it (in which latter case the analytical judgment is an identical one)— and synthetic or anq)liti- • Ueberweg's Hist, of Fhil. (English Trans.), vol. ii. pp. 154 58 (§ 122). 384 UEBERWEG'S SUMMARY OF THE 'CRITIQUE.' cative judgments — where tlie predicate is not contained in the concept of the subject, Init is added to it. The principle of analy- tical judgments is the principle of identity and contradiction ; a synthetic judgment, on the contrary, cannot be formed from the conception of its subject on the basis of this principle alone. Kant further discriminates, with reference to their origin as parts of human knowledge, between judgments a priori and judgments a 2)osteriori ; by the latter he understands judgments of experience, but by judgments a jjriori, in the absolute sense, those which are completely independent of all experience, and in the relative sense, those which are based indirectly on experience, or in which the concep- tions employed, though not derived immediately from experience, are deduced from others that were so derived. As absolute judgments a priori Kant regards all those which have tlie marks of necessity and strict universality, assuming (what he does not prove, but simply posits as self-evident, although his whole system depends upon it) that necessity and strict universality are derivable from no combination of experiences, but only independently of all ex- perience. All analytical judgments are judgments a jyriori ; for although the subject-conception may have been obtained through expei'ience, yet to its analysis, from which the judgment results, no further experience is necessary. Synthetic judgments, on the con- trary, fall into two classes. If the synthesis of the predicate with the subject is effected by the aid of experience, the judgment is synthetic a posteriori ; if it is effected apart from all experience, it is synthetic a priori. Kant holds the existence of judgments of the latter class to be undeniable ; for among the judgments which are recognised as strictly universal and apodictical, and which are consequently, according to Kant's assumption, judgments a priori, he finds judgments wliich must at the same time be admitted to be synthetic. Among these belong, first of all, most mathematical judgments. Some of the fundamental judgments of arithmetic ((?.(/. a=a) are, indeed, according to Kant, of an analytical nature ; but the rest of tliem, together with all geometrical judgments, are, in his view, synthetic, and, since they have the marks of strict universality and necessity, are synthetic judgments a priori. The same character pertains, according to Kant, to the most general propositions of physics, such as, for example, that in all the changes of the material world the quantity of matter remains unchanged. These pi'opositions are known to be true apart from all experience, since they are universal and apodictical judgments ; and yet they are not oljtahied througli a mere analysis of the conceptions of their subjects, for the predicate adds something to those conceptions. In APPENDIX 385 like manner, finally, are all metaphysical principles, at least in their tendency, synthetic judgments a prio7'i, e.g. the principle, that every event must have a cause. And if the principles of meta- physics are not altogether incontrovertible, yet those of mathematics at least are established beyond all dispute. There exist, therefore, concludes Kant, synthetic judgments a priori or judgments of the pure reason. The fundamental question of his Critique becomes, then : How are synthetic judgments a lyi'iori possible ? The answer given is : Synthetic judgments a jjriori are possible, because man brings to the material of knowledge, which he acquires empirically in virtue of his receptivity, certain pure forms of know- ledge, which he himself creates in virtue of his spontaneity and independently of all experience, and into which he fits all given material. These forms, which are the conditions of the possibility of all experience, are at the same time the conditions of the possi- bility of the objects of experience, because whatever is to be an object for me, must take on the forms through which the £go, my original consciousness, or the ' transcendental unity of apperception,' shapes all that is presented to it ; they have, therefore, objective validity in a synthetic judgment a jwiori. But the objects, with reference to which they possess this validity, are not the things-in- themselves or transcendental objects, i.e. objects as they are in themselves, apart from our mode of conceiving them ; they are only the empirical objects or the pheenomena which exist in our conscious- ness in the form of mental representations. The things-in-them- selves are unknowable for man. Only a creative, divine mind, that gives them reality at the same time that it thinks them, can have power truly to know them. Tliings-in-themselves do not conform themselves to the forms of human knowledge, because the human consciousness is not creative, because human perception is not free from subjective elements, is not 'intellectual intuition.' Nor do the forms of human knowledge conform themselves to things-in-thcm- selves ; otherwise all our knowledge would be empirical and without necessity and strict universality. But all empirical objects, since they are only representations in our minds, do conform themselves to the forms of human knowledge. Hence we can know empirical objects or phsenomena, but only these. All valid a jyriori knowledge has respect only to pluenomena, hence to objects of real or possible experience. The forms of knowledge are forms either of intuition or of thought. The ' Transcendental Esthetic ' treats of the former, the ' Transcendental Logic ' of tlie latter. The forms of intuition are space and time. Space is the form C C 386 UEBERWEG'S SUMMATlY OF THE 'CRITIQUE' of external sensibility, time is the form of internal and indirectly of external sensibility. On the a priori nature of space depends the possibility of geometrical and on the a priori nature of time depends the possibility of aritlimetical judgments. Things-in-them- selves or transcendental objects are related neither to space nor to time ; all co-existence and succession are only in phtenomenal objects, and consequently only in the perceiving Subject. The forms of thought are the twelve categories or original con- ceptions of the understanding, on which all the forms of our judg- ments are conditioned. They are : unity, plurality, totality, — reality, negation, limitation, — substantiality, causality, reciprocal action, — possibility, existence, necessity. On their a j^Tiori nature depends the validity of the most general judgments, which lie at the foundation of all empirical knowledge. The things-in-themselves or transcendental objects have neither unity nor plurality ; they are not substances, nor are they subject to the causal relation, or to any of the categories ; the categories are applicable only to the phrenomenal objects which are in our consciousness. The reason strives to rise above and beyond the sphere of the understanding, which is confined to the finite and conditioned, to the unconditioned. It forms the idea of the soul, as a substance which ever endures ; of the world, as an unlimited causal series ; and of God, as the absolute substance and union of all perfections, or as the ' most perfect being.' Since these ideas relate to objects which lie beyond the range of all possible experience, they have no theoretic validity ; if the latter is claimed for them (in dogmatic metaphysics) this is simply the result of a misleading logic founded on appearances, or of dialectic. The psychological paralogism con- founds the unity of the I — which can never be conceived as a pre- dicate, but only and always as a subject — with the simplicity and absolute permanence of a psychical substance. Cosmology leads to antinomies, whose mutually contradictory members are each equally susceptible of indirect demonstration, if the reality of space, time and the categories be presupposed, but which with the refutation of this supposition cease to exist. Rational theology, in seeking by the ontological, cosmological, and physico-theological arguments to prove the existence of God, becomes involved in a series of sophistications. 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