The Principles of Psychology, Vols. 1-2

subject. It is a real optical sensation, seeming introspectively to have nothing to do \vith locomotor or other suggestions. It is easy to say that 'the Intellect produces it,' but what does that mean? The investigator who will throw light on this one point will probably clear up other difflculties as well. be an extremely rapid or a reversible succession. Spaceperception thus emerges without being anywhere postulated. The only things postulated are unextended feelings and time. Says Thomas Brown (lecture xxiii.) : "I am inclined to reverse exactly the process commonly supposed ; and instead of deriving the measure of time from extension, to derive the knowledge and original measure of extension from time." Brown and both the Mills think that retinal sensations, colors, in their primitive condition, are felt with no extension and that the latter merely becomes inseparably associated with them. John Mill says : " Whatever may be the retinal impression conveyed by a line which bounds two colors, I see no ground for thinking that by the eye alone we could acquire the conception of what we now mean when we say that one of the colors is outside [beside] the other." *

Whence does the extension come which gets so inseparably associated with these non-extended colored sensations ? From the * sweep and movements ' of the eye — from muscular feelings. But, as Prof. Bain says, if movement-feelings give us any property of things, " it would seem to be not space, but time." f And John Mill says that " the idea of space is, at bottom, one of time." % Space, then, is not to be found in any elementary sensation, but, in Bain's words, " as a quality, it has no other origin and no other meaning than the association of these different [non-spatial] motor and sensitive effects." §

This phrase is mystical-sounding enough to one who understands association as producing nothing, but only as knitting together things already produced in separate ways. The truth is that the English Associationist school, in trying to show how much their principle can accomplish, have altogether overshot the mark and espoused a kind of theory in respect to space-perception which the general tenor of their philosophy should lead them to abhor. Eeally there are but three possible kinds of theory concerning space. Either (1) there is no spatial quality of sensation at all, and

Space is a mere symbol of succession ; or (2) there is an ea?- tensive quality given immediately in certain particular sensations ; or, finally, (3) there is a quality produced out of the inward resources of the mind, to envelop sensations which, as given originally, are not spatial, but which, on being cast into the spatial form, become united and orderly. This last is the Kantian view. Stumpf admirably designates it as the ' psychic stimulus ' theory, the crude sensations being considered as goads to the mind to put forth its slumbering power.

Brown, the Mills, and Bain, amid these possibilities, seem to have gone astray like lost sheep. With the * mental chemistry ' of which the Mills speak — precisely the same thing as the * psychical synthesis ' of Wundt, which, as we shall soon see, is a principle expressly intended to do what Association can never perform — they hold the third view, but again in other places imply the first. And, between the impossibility of getting from mere association anything not contained in the sensations associated and the dislike to allow spontaneous mental productivity, they flounder in a dismal dilemma. Mr. Sully joins them there in what I must call a vague and vacillating way. Mr. Spencer of course is bound to pretend to * evolve ' all mental qualities out of antecedents different from themselves, so that we need perhaps not wonder at his refusal to accord the spatial quality to any of the several elementary sensations out of which our space-perception grows. Thus (Psychology, II. 168, 172, 218):

*' No idea of extension can arise from a simultaneous excitation " of a multitude of nerve-terminations like those of the skin or the retina, since this would imply a " knowledge of their relative positions "—that is, '* apre-existent idea of a special extension, which is absurd." " No relation between successive states of consciousness gives in itself any idea of extension." " The muscular sensations accompanying motion are quite distinct from the notions of space and time associated with them."

Mr. Spencer none the less inveighs vociferously against the Kantian position that space is produced by the mind's own resources. And yet he nowhere denies space to be a specific affection of consciousness different from time 1 Such incoherency is pitiful. The fact is that, at bottom, all these authors are really * psychical stimulists,' or Kantists. The space they speak of is a super-sensational mental product. This position appears to me thoroughly mythological. But let us see how it is held by those who know more definitely what they mean. Schopenhauer expresses the Kantian view with more vigor and clearness than anyone else. He says :

" A man must be forsaken by all the gods to dream that the world we see outside of us, filling space in its three dimensions, moving down the inexorable stream of time, governed at each step by Causality's invariable law, — but in all this only following rules which we may prescribe for it in advance of all experience, — to dream, I say, that such a world should stand there outside of us, quite objectively real with no complicity of ours, and thereupon by a subsequent act, through the instrumentality of mere sensation, that it should enter our head and reconstruct a duplicate of itself as it was outside. For what a poverty-stricken thing is this mere sensation ! Even in the noblest organs of sense it is nothing more than a local and specific feeling, susceptible within its kind of a few variations, but always strictly subjective and containing in itself nothing objective, nothing resembling a perception. For sensation of every sort is and remains a process in the organism itself. As such it is limited to the territory inside the skin and can never, accordingly, per se contain anything that lies outside the skin or outside ourselves. . . . Only when the Understanding ... is roused to activity and brings its sole and only form, the law of Causality, into play, only then does the mighty transformation take place which makes out of subjective sensation objective intuition. The Understanding, namely, grasps by means of its innate, a priori, ante-experiential form, the given sensation of the body as an effect which as such must necessarily have a cause. At the same time the Understanding summons to its aid the form of the outer sense which similarly lies already preformed in the intellect (or brain), and which is Space, in order to locate that cause outside of the organism. ...

In this process the Understanding, as I shall soon show, takes note of the most minute peculiarities of the given sensation in order to construct in the outer space a cause which shall completely account for them. This operation of the Understanding is, however, not one that takes place discursively, reflectively, in abstracto, by means of words and concepts ; but is intuitive and immediate. . . . Thus the Understanding must first create the objective world ; never can the latter, already complete in se, simply promenade into our heads through the senses and organic apertures. For the senses yield us nothing further than the raw material which must be first elaborated into the objective conception of an orderly physical world-system by means of the aforesaid simple forms of Space, Time, and Causality. . . . Let me show the

great chasm between sensation and perception by showing how raw the material is out of which the fair structure is upreared. Only two senses serve objective perception : touch and sight. They alone furnish the data on the basis whereof the Understanding, by the process indicated, erects the objective world. . . . These data in themselves are still no perception ; that is the Understanding's work. If I press with my hand against the table, the sensation I receive has no analogy with the idea of the firm cohesion of the parts of this mass : only when my Understanding passes from the sensation to its cause does it create for itself a body with the properties of solidity, impenetrability, and hardness. When in the dark I lay my hand on a surface, or grasp a ball of three inches diameter, in either case the same parts of the hand receive the impression : but out of the different contraction of the hand in the two cases my Understanding constructs the form of the body whose contact caused the feeling, and confirms its construction by leading me to move my hand over the body. If one born blind handles a cubical body, the sensations of his hand are quite uniform on all sides and in all directions,—only the corners press upon a smaller part of his skin. In these sensations, as such, there is nothing whatever analogous to a cube. But from the felt resistance his Understanding infers immediately and intuitively a cause thereof, which now presents itself as a solid body ; and from the movements of exploration which the arms made whilst the feelings of the hands remained constant he constructs, in the space known to him a priori^ the body's cubical shape. Did he not bring with him ready-made the idea of a cause and of a space, with the laws thereof, there never could arise, out of those successive feelings in his hand, the image of a cube.

If we let a string run through our closed hand, we immediately construct as the cause of the friction and its duration in such an attitude of the hand, a long cylindrical body moving uniformly in one direction. But never out of the pure sensation in the hand could the idea of movement, that is, of change of position in space by means of time, arise : such a content can never lie in sensation, nor come out of it. Our Intellect, antecedently to all experience, must bear in itself the intuitions of Space and Time, and therewithal of the possibility of motion, and no less the idea of Causality, to pass from the empirically given feeling to its cause, and to construct the latter as a so moving body of the designated shape. For how great is the abyss between the mere sensation in the hand and the ideas of causality, materiality, and movement through Space, occurring in Time! The feeling in the hand, even with different contacts and positions, is something far too uniform and poor in content for it to be possible to construct out of it the idea of Space with its three dimensions, of the action of bodies on each other, with the properties of extension, impenetrability, cohesion, shape, hardness, softness, rest, and motion — in short, the foundations of the objective world. This is only possible through Space, Time, and Causality . . . being preformed in the Intellect itself^ . . . from whence it again follows that the peroeption

of the external world is essentially an intellectual process, a work of the Understanding, to which sensation furnishes merely the occasion, and the data to be interpreted in each particular case." * I call this view mythological, because I am conscious of no such Kantian machine-shop in my mind, and feel no call to disparage the powers of poor sensation in this merciless way. I have no introspective experience of mentally producing or creating space. My space-intuitions occur not in two times but in one. There is not one moment of passive inextensive sensation, succeeded by another of active extensive perception, but the form I see is as immediately felt as the color which fills it out. That the higher parts of the mind come in, who can deny ? They add and subtract, they compare and measure, they reproduce and abstract. They inweave the space-sensations with intellectual relations ; but ^tee relations are the same when they obtain between the elements of the space-system as when they obtain between any of the other elements of which the world is made.

The essence of the Kantian contention is that there are not spaces, but Space — one infinite continuous Unit — and that our knowledge of this cannot be a piecemeal sensational affair, produced by summation and abstraction. To which the obvious reply is that, if any known thing bears on its front the appearance of piecemeal construction and abstraction, it is this very notion of the infinite unitary space of the world. It is a notion, if ever there was one ; and no intuition. Most of us apprehend it in the barest symbolic abridgment : and if perchance we ever do try to make it more adequate, we just add one image of sensible extension to another until we are tired. Most of us are obliged to turn round and drop the thought of the space in front of us when we think of that behind. And the space represented as near to us seems more minutely subdivisible than that we think of as lying far away.

The other prominent German writers on space are also * psychical stimulists.' Herbart, whose influence has been widest, says * the resting eye sees no space,' t and ascribes * Vierfache Wurzel des Satzes vom zureichenden Grunde, pp. 52-7. f Psychol als Wissenschaft, § 111. visual extension to the influence of movements combining with the non-spatial retinal feelings so as to form gradated series of the latter. A given sensation of such a series reproduces the idea of its associates in regular order, and its idea is similarly reproduced by any one of them with the order reversed. Out of the fusion of these two contrasted reproductions comes the form of space* — Heaven knows how.

The obvious objection is that mere serial order is a genuSy and space-order a very peculiar species of that genus ; and that, if the terms of reversible series became by that fact coexistent terms in space, the musical scale, the degrees of warmth and cold, and all other ideally graded series ought to appear to us in the shape of extended corporeal aggregates,— which they notoriously do not, though we may of course symbolize their order by a spatial scheme. W. Volkmann von Volkmar, the Herbartian, takes the bull here by the horns, and says the musical scale is spatially extended, though he admits that its space does not belong to the real world. t I am unacquainted with any other Herbartian so bold.

To Lotze we owe the much-used term * local sign.' He insisted that space could not emigrate directly into the mind from without, but must be reconstructed by the soul ; and he seemed to think that the first reconstructions of it by the soul must be super-sensational. But why sensations themselves might not be the soul's original spatial reconstructive acts Lotze fails to explain. Wundt has all his life devoted himself to the elaboration of a space-theory, of which the neatest and most final expression is to be found in his Logik (ii. 457-60). He says :

"In the eye, space-perception has certain constant peculiarities which prove that no single optical sensation by itself possesses the extensive form, but that everywhere in our perception of space heterogene- f Lehrbuch d. Psychol., 3te Auflage, Bd. ii. p. 66. Volkmann's fifth chapter contains a really precious collection of historical notices concerning space-perception theories 0U8 feelings combine. If we simply suppose that luminous sensations per se feel extensive, our supposition is shattered by that influence of movement in vision which is so clearly to be traced in many normal errors in the measurement of the field of view. If we assume, on the other hand, that the movements and their feelings are alone possessed of the extensive quality, we make an unjustified hypothesis, for the phenomena compel us, it is true, to accord an influence to movement, but give us no right to call the retinal sensations indifferent, for there are no visual ideas without retinal sensations. If then we wish rigorously to express the given facts, we can ascribe a spatial constitution only to combinations of retinal sensations with those of movement."

Thus Wundt, dividing theories into *nativistic' and * genetic,' calls his own a genetic theory. To distinguish it from other theories of the same class, he names it a * theory of complex local signs.' " It supposes two systems of local signs, whose relations — taking the eye as an example — we may think as . . . the measuring of the manifold local-sign system of the retina by the simple local-sign system of the movements. In its psychological nature this is a process of associative synthesis : it consists in the fusion of both groups of sensations into a product, whose elementary components are no longer separable from each other in idea. In melting wholly away into the product which they create they become consciously undistinguishable, and the mind apprehends only their resultant, the intuition of space. Thus there obtains a certain analogy between this psychic synthesis and that chemical synthesis which out of simple bodies generates a compound that appears to our immediate perception as a homogeneous whole with new properties. "

Now let no modest reader think that if this sounds obscure to him it is because he does not know the full context ; and that if a wise professor like Wundt can talk so fluently and plausibly about ' combination ' and * psychic synthesis,' it must surely be because those words convey a so much greater fulness of positive meaning to the scholarly than to the unlearned mind. Really it is quite the reverse ; aM the virtue of the phrase lies in its mere sound and skin. Learning does but make one the more sensible of its inward unintelligibility. Wundt's ' theory ' is the flimsiest thing in the world. It starts by an untrue assumption, and then corrects it by an unmeaning phrase. Retinal sensations are spatial ; and were they not, no amount of 'synthesis' with equally spaceless motor sensations could

intelligibly make them so. Wundt's theory is, in short, but an avowal of impotence, and an appeal to the inscrutable powers of the soul.^ It confesses that we cannot analyze the constitution or give the genesis of the spatial quality in consciousness. But at the same time it says the aniecedents thereof are psychical and not cerebral facts. In calling the quality in question a sensational quality, our own account equally disclaimed ability to analyze it, but said its antecedents were cerebral, not psychical — in other words, that it was s> first psychical thing. This is merely a question of probable fact, which the reader may decide.

And now what shall be said of Helmholtz ? Can I find fault with a book which, on the whole, I imagine to be one of the four or five greatest monuments of human genius in the scientific line ? If truth impels I must fain try, and take the risks. It seems to me that Helmholtz's genius moves most securely when it keeps close to particular facts. At any rate, it shows least strong in purely speculative passages, which in the Optics, in spite of many beauties, seem to me fundamentally vacillating and obscure. The *empiristic' view which Helmholtz defends is that the space-determinations we perceive are in every case products of a process of unconscious inference, f The inference is similar to one from induction or analogy. % We always see that form before us which habitually would have caused the sensation we now have. § But the latter sensation can never be intrinsically spatial, or its intrinsic spacedeterminations would never be overcome as they are so often by the ' illusory ' space-determinations it so often suggests.! Since the illusory determination can be traced to a suggestion of Experience, the * real ' one must also be such a suggestion : so that all space intuitions are due sole-

* Why talk of 'genetic theories '? when we have in the next breath to write as Wundt does: ' ' If then we must regard the intuition of space as a product that simply emerges from the conditions of our mental and physical organization, nothing need stand in the way of our designating it asone of the a priori functions with which consciousness is endowed." (Logik, n. 460.) ly to Experience.* The only psychic activity required for this is the association of ideas, f

But how, it may be asked, can association produce a spacequality not in the things associated ? How can we by induction or analogy infer what we do not already generically know ? Can * suggestions of experience ' reproduce elements which no particular experience originally contained ? This is the point by which Helmholtz 's * empiristic ' theory, as a theory, must be judged. No theory is worthy of the name which leaves such a point obscure.

Well, Helmholtz does so leave it. At one time he seems to fall back on inscrutable powers of the soul, and to range himself with the * psychical stimulists.' He speaks of Kant as having made the essential step in the matter in distinguishing the content of experience from that form — space, course — which is given it by the peculiar faculties of the mind. :[: But elsewhere, again, § speaking of sensation alistic theories which would connect spatially determinate feelings directly with certain neural events, he says it is better to assume only such simple psychic activities as we know to exist, and gives the association of ideas as an instance of what he means. Later, || he reinforces this remark by confessing that he does not see how any neural process can give rise without antecedent experience to a ready-made (fertige) perception of space. And, finally, in a single momentous sentence, he speaks of sensations of totich as if they might be the original material of our spacepercepts — which thus, from the optical point of view, ' may be assumed as given.' '^

Of course the eye-man has a right to fall back on the skin-man for help at a pinch. But doesn't this mean that he is a mere eye-man and not a complete psychologist ? In other words, Helmholtz's Optics and the ' empiristic theory ' (herein professed must not be understood as attempts at answering the general question of how space-consciousness enters the mind. They simply deny that it enters with the first optical sensations.* Our own account has affirmed stoutly that it enters then ; but no more than Helmholtz have we pretended to show why. Who calls a thing a firsf sensation admits he has no theory of its production. Helmholtz, though all the while without an articulate theory, makes the world think he has one. He beautifully traces the immense part which reproductive processes play in our vision of space, and never — except in that one pitiful little sentence about touch — does he tell us just what it is they reproduce. He limits himself to denying that they reproduce originals of a visual sort. And so difficult is the subject, and so magically do catch-words work on the popular-scientist ear, that most likely, had he written * physiological ' instead of ' nativistic,' and ' spiritualistic * instead of * empiristic ' (which synonyms Hering suggests), numbers of his present empirical evolutionary followers would fail to find in his teaching anything worthy of praise. But since he wrote otherwise, they hurrah for him as a sort of second Locke, dealing another death-blow at the old bugaboo of * innate ideas.' His * nativistic ' adversary Hering they probably imagine — Heaven save the mark ! — to be a scholastic in modern disguise.

After Wundt and Helmholtz, the most important antisensationalist space-philosopher in Germany is Professor Lipps, whose deduction of space from an order of nonspatial differences, continuous yet separate, is a wonderful piece of subtlety and logic. And yet he has to confess that continuous differences form in the first instance only a logical series, which need not appear spatial, and that wherever it does so appear, this must be accounted a ' fact,' due merely Ho the nature of the soul.'f

Lipps, and almost all the an tisensationalist theorists except Helmholtz, seem guilty of that confusion which Mr. *In fact, to borrow a simile from Prof. G. E. Mtiiler (Tbeorie der sinnl. Aufmerksamkeit, p. 38), the various senses bear in the Helmholtzian philosophy of perception the same relation to the ' object ' perceived by their means that a troop of jolly drinkers bear to the landlord's bill, when no one has any money, but each hopes that one of the rest will pay.

Shadworth Hodgson has done so much to clear away, viz., the confounding the analysis of an idea with the means of its production. Lipps, for example, finds that every space we think of can be broken up into positions, and concludes that in some undefined way the several positions must have pre-existed in thought before the aggregate space could have appeared to perception. Similarly Mr. Spencer, defining extension as an * aggregate of relations of coexistent position,' says " every cognition of magnitude is a cognition of relations of position,"''^ and **no idea of extension can arise from the simultaneous excitation" of many nerves "unless there is a knowledge of their relative positions. "t Just so Prof. Bain insists that the very meaning of space is scope for movement, % and that therefore distance and magnitude can be no original attributes of the eye's sensibility. Similarly because movement is analyzable into positions occupied at successive moments by the mover, philosophers (e.g. Schopenhauer, as quoted above) have repeatedly denied the possibility of its being an immediate sensation. We have, however, seen that it is the most immediate of all our space-sensations. Because it can only occur in a definite direction the impossibility of perceiving it without perceiving its direction has been decreed — a decree which the simplest experiment overthrows. § It is a case of what I have called the ' psychologist's fallacy ' : mere acquaintance with space is treated as tantamount to every sort of knowledge about it, the conditions of the latter are demanded of the former state of mind, and all sorts of mythological processes are brought in to help. || As well might one say that because the world consists of all its parts, there-

I As other examples of the confusion, take Mr. Sully : " The fallacious assumption that there can be an idea of distance in general, apart from particular distances" (Mind, in. p. 177); and Wundt: "An indefinite localization, which waits for experience to give it its reference to real space, stands in contradiction with the very idea of localization, which means the reference to a determinate point of space " (Physiol. Psych., Ite Aufl. p. 480). fore we can only apprehend it at all by having unconsciously summed these up in our head. It is the old idea of our actual knowledge being drawn out from a pre-existent potentiality, an idea which, whatever worth it may metaphysically possess, does no good in psychology.

My own sensationalistic account has derived most aid and comfort from the writings of Hering, A. W. Volkmann, Stumpf, Leconte, and Schon. All these authors allow ample scope to that Experience which Berkeley's genius saw to be a present factor in all our visual acts. But they give Experience some grist to grind, which the soi-distant * empiristic ' school forgets to do. Stumpf seems to me the most philosophical and profound of all these writers ; and I owe him much. I should doubtless have owed almost as much to Mr. James Ward, had his article on Psychology in the Encyclopaedia Britannica appeared before my own thoughts were written down. The literature of the question is in all languages very voluminous. I content myself with referring to the bibliography in Helmholtz's and Aubert's works on Physiological Optics for the visual part of the subject, and with naming in a note the ablest works in the English tongue which have treated of the subject in a general way.*