Chapter 2

This explanation is easily proved false by painting the disk with narrow green and gray concentric rings, and giving each a different saturation. The contrast appears though there is no ground-color, and no longer a single difference, but many. The facts which Helmholtz brings forward in support of his theory are also easily turned against him. He asserts that if the color of the ground is too intense, or if the gray ring is bordered by black circles, the contrast becomes weaker; that no contrast appears on a white scrap held over the colored field; and that the gray ring when compared with such scrap loses its contrast-color either wholly or in part. Hering points out the inaccuracy of all these claims. Under favorable conditions it is impossible to make the contrast disappear by means of black enclosing lines, although they naturally form a disturbing element; increase in the saturation of the field, if disturbance through increasing brightness-contrast is to be avoided, demands a darker gray field, on which contrast-colors are less easily perceived; and careful use of the white scrap leads to entirely different results. The contrast-color does appear upon it when it is first placed above the colored field; but if it is carefully fixated, the contrast-color diminishes very rapidly both on it and on the ring, from causes already explained. To secure accurate observation, all complication through successive contrast should be avoided thus: first arrange the white scrap, then interpose a gray screen between it and the disk, rest the eye, set the wheel in motion, fixate the scrap, and then have the screenremoved. The contrast at once appears clearly, and its disappearance through continued fixation can be accurately watched.

Brief mention of a few other cases of contrast must suffice. The so-called mirror experiment consists of placing at an angle of 45º a green (or otherwise colored) pane of glass, forming an angle with two white surfaces, one horizontal and the other vertical. On each white surface is a black spot. The one on the horizontal surface is seen through the glass and appears dark green, the other is reflected from the surface of the glass to the eye, and appears by contrast red. The experiment may be so arranged that we are not aware of the presence of the green glass, but think that we are looking directly at a surface with green and red spots upon it; in such a case there is no deception of judgment caused by making allowance for the colored medium through which we think that we see the spot, and therefore the psychological explanation does not apply. On excluding successive contrast by fixation the contrast soon disappears as in all similar experiments.[27]

Colored shadowshave long been thought to afford a convincing proof of the fact that simultaneous contrast is psychological in its origin. They are formed whenever an opaque object is illuminated from two separate sides by lights of different colors. When the light from one source is white, its shadow is of the color of the other light, and the second shadow is of a color complementary to that of the field illuminated by both lights. If now we take a tube, blackened inside, and through it look at the colored shadow, none of the surrounding field being visible, and then have the colored light removed, the shadow still appears colored, although 'the circumstances which caused it have disappeared.' This is regarded by the psychologists as conclusive evidence that the color is due to deception of judgment. It can, however, easily be shown that the persistence of the color seen through the tube is due to fatigue of the retina through the prevailing light, and that when the colored light is removed the color slowly disappears as theequilibrium of the retina becomes gradually restored. When successive contrast is carefully guarded against, the simultaneous contrast, whether seen directly or through the tube, never lasts for an instant on removal of the colored field. The physiological explanation applies throughout to all the phenomena presented by colored shadows.[28]

If we have a small field whose illumination remains constant, surrounded by a large field of changing brightness, an increase or decrease in brightness of the latter results in a corresponding apparent decrease or increase respectively in the brightness of the former, while the large field seems to be unchanged. Exner says:

"This illusion of sense shows that we are inclined to regard as constant the dominant brightness in our field of vision, and hence to refer the changing difference between this and the brightness of a limited field to a change in brightness of the latter."

The result, however, can be shown to depend not on illusion, but on actual retinal changes, which alter the sensation experienced. The irritability of those portions of the retina lighted by the large field becomes much reduced in consequence of fatigue, so that the increase in brightness becomes much less apparent than it would be without this diminution in irritability. The small field, however, shows the change by a change in the contrast-effect induced upon it by the surrounding parts of the retina.[29]

The above cases show clearly thatphysiological processes, and not deception of judgment, are responsible for contrast of color. To say this, however, is not to maintain that our perception of a color is never in any degree modified by our judgment of what the particular colored thing before us may be. We have unquestionable illusions of color due to wrong inferences as to what object is before us. Thus Von Kries[30]speaks of wandering through evergreen forests covered with snow, and thinking that through the interstices of the boughs he saw the deep blue of pine-clad mountains, coveredwith snow and lighted by brilliant sunshine; whereas what he really saw was the white snow on trees near by, lying in shadow].[31]

Such a mistake as this is undoubtedly of psychological origin. It is a wrongclassificationof the appearances, due to the arousal of intricate processes of association amongst which is the suggestion of a different hue from that really before the eyes. In the ensuing chapters such illusions as this will be treated of in considerable detail. But it is a mistake to interpret the simpler cases of contrast in the light of such illusions as these. These illusions can be rectified in an instant, and we then wonder how they could have been. They come from insufficient attention, or from the fact that the impression which we get is a sign of more than one possible object, and can be interpreted in either way. In none of these points do they resemble simple color-contrast, whichunquestionably is a phenomenon of sensation immediately aroused.

I have dwelt upon the facts of color-contrast at such great length because they form so good a text to comment on in my struggle against the view that sensations are immutable psychic things which coexist with higher mental functions. Both sensationalists and intellectualists agree that such sensations exist. Theyfuse, say the pure sensationalists, andmakethe higher mental function; theyare combinedby activity of the Thinking Principle, say the intellectualists. I myself have contended that theydo not existin or alongside of the higher mental function when that exists. The things which arouse them exist; and the higher mental function also knows these same things. But just as its knowledge of the things supersedes and displaces their knowledge, so it supersedes and displaces them, when it comes, being as much as they are a direct resultant of whatever momentary brain-conditions may obtain. The psychological theory of contrast, on the other hand, holds the sensations still to exist in themselves unchanged before the mind, whilst the 'relating activity' of the latterdeals with them freely and settles to its own satisfaction what each shall be, in view of what the others also are. Wundt says expressly that the Law of Relativity is "not a law of sensation but a law of Apperception;" and the word Apperception connotes with him a higher intellectual spontaneity.[32]This way of taking things belongs with the philosophy that looks at thedataof sense as something earth-born and servile, and the 'relating of them together' as something spiritual and free. Lo! the spirit can even change the intrinsic quality of the sensible facts themselves if by so doing it can relate them better to each other! But (apart from the difficulty of seeing how changing the sensations should relate them better) is it not manifest that the relations are part of the 'content' of consciousness, part of the 'object,' just as much as the sensations are? Why ascribe the former exclusively to theknowerand the latter to theknown? Theknoweris in every case a unique pulse of thought corresponding to a unique reaction of the brain upon its conditions. All that the facts of contrast show us is that thesame real thingmay give us quite different sensations when the conditions alter, and that we must therefore be careful which one to select as the thing's truest representative.

There are many other facts beside the phenomena of contrastwhich prove thatwhen two objects act together on us the sensation which either would give alone becomes a different sensation. A certain amount of skin dipped in hot water gives the perception of a certain heat. More skin immersed makes the heat much more intense, although of course the water's heat is the same. A certain extent as well as intensity, in the quantity of the stimulus is requisite for any quality to be felt. Fick and Wunderli could not distinguish heat from touch when both were applied through ahole in a card, and so confined to a small part of the skin. Similarly there is achromatic minimumof size in objects. The image they cast on the retina must needs have a certain extent, or it will give no sensation of color at all. Inversely, more intensity in the outward impression may make the subjective object more extensive. This happens, as will be shown inChapter XIX, when the illumination is increased: The whole room expands and dwindles according as we raise or lower the gas-jet. It is not easy to explain any of these results as illusions of judgment due to the inference of a wrong objective cause for the sensation which we get. No more is this easy in the case of Weber's observation that a thaler laid on the skin of the forehead feels heavier when cold than when warm; or of Szabadföldi's observation that small wooden disks when heated to 122° Fahrenheit often feel heavier than those which are larger but not thus warmed;[33]or of Hall's observation that a heavy point moving over the skin seems to go faster than a lighter one moving at the same rate of speed.[34]

Bleuler and Lehmann some years ago called attention to a strange idiosyncrasy found in some persons, and consisting in the fact that impressions on the eye, skin, etc., were accompanied by distinct sensations ofsound.[35]Colored hearingis the name sometimes given to the phenomenon, which has now been repeatedly described. Quite lately the Viennese aurist Urbantschitsch has proved that these cases are only extreme examples of a very general law, and that all our sense-organs influence each other's sensations.[36]The hue of patches of color so distant as not to be recognized was immediately, in U.'s patients, perceived when a tuning-fork was sounded close to the ear. Sometimes, on the contrary, the field was darkened by the sound. The acuity of vision was increased, so that letters too far off to be read could be read when the tuning-fork was heard. Urbantschitsch, varying his experiments, found that theirresults were mutual, and that sounds which were on the limits of audibility became audible when lights of various colors were exhibited to the eye. Smell, taste, touch, sense of temperature, etc., were all found to fluctuate when lights were seen and sounds were heard. Individuals varied much in the degree and kind of effect produced, but almost every one experimented on seems to have been in some way affected. The phenomena remind one somewhat of the 'dynamogenic' effects of sensations upon the strength of muscular contraction observed by M. Féré, and later to be described. The most familiar examples of them seem to be the increase ofpainby noise or light, and the increase ofnauseaby all concomitant sensations. Persons suffering in any way instinctively seek stillness and darkness.

Probably every one will agree that the best way of formulating all such facts is physiological: it must be that the cerebral process of the first sensation is reinforced or otherwise altered by the other current which comes in. No one, surely, will prefer a psychological explanationhere. Well, it seems to me thatallcases of mental reaction to a plurality of stimuli must be like these cases, and that the physiological formulation is everywhere the simplest and the best. When simultaneous red and green light make us see yellow, when three notes of the scale make us hear a chord, it is not because the sensations of red and of green and of each of the three notes enter the mind as such, and there 'combine' or 'are combined by its relating activity' into the yellow and the chord, it is because the larger sum of light-waves and of air-waves arouses new cortical processes, to which the yellow and the chord directly correspond. Even when the sensible qualities of things enter into the objects of our highest thinking, it is surely the same. Their severalsensationsdo not continue to exist there tucked away. They arereplacedby the higher thought which, although a different psychic unit from them, knows the same sensible qualities which they know.

The principles laid down in Chapter VI seem then to be corroborated in this new connection.You cannot build up one thought or one sensation out of many; and only directexperiment can inform us of what we shall perceive when we get many stimuli at once.

We often hear the opinion expressed that all our sensations at first appear to us as subjective or internal, and are afterwards and by a special act on our part 'extradited' or 'projected' so as to appear located in an outer world. Thus we read in Professor Ladd's valuable work that

"Sensations... are psychical stateswhose place—so far as they can be said to have one—is the mind. The transference of these sensations from mere mental states to physical processes located in the periphery of the body, or to qualities of things projected in space external to the body, is a mental act. It may rather be said to be a mentalachievement[cf. Cudworth,note 10, as to knowledge beingconquering], for it is an act which in its perfection results from a long and intricate process of development.... Two noteworthy stages, or 'epoch-making' achievements in the process of elaborating the presentations of sense, require a special consideration. These are 'localization,' or the transference of the composite sensations from mere states of the mind to processes or conditions recognized as taking place at more or less definitely fixed points or areas of the body; and 'eccentric projection' (sometimes called 'eccentric perception') or the giving to these sensations an objective existence (in the fullest sense of the word 'objective') as qualities of objects situated within a field of space and in contact with, or more or less remotely distant from, the body."[37]

It seems to me that there is not a vestige of evidence for this view. It hangs together with the opinion that our sensations are originally devoid of all spatial content,[38]an opinion which I confess that I am wholly at a loss to understand. As I look at my bookshelf opposite I cannot frame to myself an idea, however imaginary, of any feeling which I could ever possibly have got from it except the feeling ofthe same big extended sort of outward fact which I now perceive. So far is it from being true that our first way of feeling things is the feeling of them as subjective or mental, that the exact opposite seems rather to be the truth. Our earliest, most instinctive, least developed kind of consciousness is the objective kind; and only as reflection becomes developed do we become aware of an inner world at all. Then indeed we enrich it more and more, even to the point of becoming idealists, with the spoils of the outer world which at first was the only world we knew. But subjective consciousness, aware of itself as subjective, does not at first exist. Even an attack of pain is surely felt at first objectively as something in space which prompts to motor reaction, and to the very end it is located, not in the mind, but in some bodily part.

"A sensation which should not awaken an impulse to move, nor any tendency to produce an outward effect, would manifestly be useless to a living creature. On the principles of evolution such a sensation could never be developed. Therefore every sensation originally refers to something external and independent of the sentient creature. Rhizopods (according to Engelmann's observations) retract their pseudopodia whenever these touch foreign bodies, even if these foreign bodies are the pseudopodia of other individuals of their own species, whilst the mutual contact of their own pseudopodia is followed by no such contraction. These low animals can therefore already feel an outer world—even in the absence of innate ideas of causality, and probably without any clear consciousness of space. In truth the conviction that something exists outside of ourselves does not come from thought. It comes from sensation; it rests on the same ground as our conviction of our own existence.... If we consider the behavior of new-born animals, we never find them betraying that they are first of all conscious of their sensations as purely subjective excitements. We far more readily incline to explain the astonishing certainty with which they make use of their sensations (and which is an effect of adaptation and inheritance) as the result of an inborn intuition of the outer world.... Instead of starting from an original pure subjectivity of sensation, and seeking how this could possibly have acquired an objective signification, we must, on the contrary, begin by the possession of objectivity by the sensation and then show how for reflective consciousness the latter becomes interpreted as an effect of the object, how in short the original immediate objectivity becomes changed into a remote one."[39]

Another confusion, much more common than the denial of all objective character to sensations, is the assumption that they are all originally locatedinside the bodyand are projected outward by a secondary act. This secondary judgment is always false, according to M. Taine, so far as the place of the sensation itself goes. But it happens tohita real object which is at the point towards which the sensation is projected; so we may call its result, according to this author, averidical hallucination.[40]The word Sensation, tobegin with, is constantly, in psychological literature, used as if it meant one and the same thing with thephysical impressioneither in the terminal organs or in the centres, which is its antecedent condition, and this notwithstanding that by sensation we mean a mental, not a physical, fact. But those who expressly mean by it a mental fact still leave to it a physicalplace, still think of it as objectively inhabiting the very neural tracts which occasion its appearance when they are excited; and then (going a step farther) they think that it mustplace itselfwheretheyplace it, or be subjectively sensible of that place as its habitat in the first instance, and afterwards have to bemovedso as to appear elsewhere.

All this seems highly confused and unintelligible. Consciousness, as we saw in an earlier chapter (vol. I p. 214) cannot properly be said toinhabitany place. It has dynamic relations with the brain, and cognitive relations with everything and anything. From the one point of viewwemay say that a sensation is in the same place with the brain (if we like), just as from the other point of view we may say that it is in the same place with whatever quality it may be cognizing. But the supposition that a sensation primitivelyfeels either itself or its object to be in the same place with the brainis absolutely groundless, and neithera prioriprobability nor facts from experience can be adduced to show that such a deliverance forms any part of the original cognitive function of our sensibility.

Where, then, do we feel the objects of our original sensations to be?

Certainly a child newly born in Boston, who gets a sensation from the candle-flame which lights the bedroom, or from his diaper-pin, does not feel either of these objects tobe situated in longitude 72° W. and latitude 41° N. He does not feel them to be in the third story of the house. He does not even feel them in any distinct manner to be to the right or the left of any of the other sensations which he may be getting from other objects in the room at the same time. He does not, in short, know anythingabouttheir space-relations to anything else in the world. The flame fills its own place, the pain fills its own place; but as yet these places are neither identified with, nor discriminated from, any other places. That comes later. For the places thus first sensibly known are elements of the child's space-world which remain with him all his life; and by memory and later experience he learns a vast number of thingsaboutthose places which at first he did not know. But to the end of time certain places of the world remain defined for him as the placeswhere those sensations were; and his only possible answer to the questionwhere anything iswill be to say 'there,' and to name some sensation or other like those first ones, which shall identify the spot. Spacemeansbut the aggregate of all our possible sensations. There is no duplicate space knownaliunde, or created by an 'epoch-making achievement' into which our sensations, originally spaceless, are dropped. Theybringspace and all its places to our intellect, and do not derive it thence.

By his body, then, the child later means simplythat place wherethe pain from the pin, and a lot of other sensations like it, were or are felt. It is no more true to say that he locates that pain in his body, than to say that he locates his body in that pain. Both are true: that pain is part of what hemeans by the word body. Just so by the outer world the child means nothing more thanthat place wherethe candle-flame and a lot of other sensations like it are felt. He no more locates the candle in the outer world than he locates the outer world in the candle. Once again, he does both; for the candle is part of what hemeansby 'outer world.'

This (it seems to me) will be admitted, and will (I trust) be made still more plausible in the chapter on the Perception of Space. But the later developments of this perception are so complicated that these simple principles geteasily overlooked. One of the complications comes from the fact that thingsmove, and that the original object which we feel them to be splits into two parts, one of which remains as their whereabouts and the other goes off as their quality or nature. We then contrast where theywerewith where theyare. Ifwedo not move, the sensation ofwhere they wereremains unchanged; but we ourselves presently move, so that that also changes; and 'where they were' becomes no longer the actual sensation which it was originally, but a sensation which we merely conceive as possible. Gradually the system of these possible sensations, takes more and more the place of the actual sensations. 'Up' and 'down' become 'subjective' notions; east and west grow more 'correct' than 'right' and 'left' etc.; and things get at last more 'truly' located by their relation to certain ideal fixed co-ordinates than by their relation either to our bodies or to those objects by which their place was originally defined.Now this revision of our original localizations is a complex affair; and contains some facts which may very naturally come to be described as translocations whereby sensations get shoved farther off than they originally appeared.

Few things indeed are more striking than the changeable distance which the objects of many of our sensations may be made to assume. A fly's humming may be taken for a distant steam-whistle; or the fly itself, seen out of focus, may for a moment give us the illusion of a distant bird. The same things seem much nearer or much farther, according as we look at them through one end or another of an opera-glass. Our whole optical education indeed is largely taken up with assigning their proper distances to the objects of our retinal sensations. An infant will grasp at the moon; later, it is said, he projects that sensation to a distance which he knows to be beyond his reach. In the much quoted case of the 'young gentleman who was born blind,' and who was 'couched' for the cataract by Mr. Chesselden, it is reported of the patient that "when he first saw, he was so far from making any judgment about distances, that he thought all objects whatever touched his eyes (as he expressed it) as what he felt did his skin." And other patients born blind, but relieved by surgicaloperation, have been described as bringing their hand close to their eyes to feel for the objects which they at first saw, and only gradually stretching out their hand when they found that no contact occurred. Many have concluded from these facts that our earliest visual objects must seem in immediate contact with our eyes.

But tactile objects also may be affected with a like ambiguity of situation.

If one of the hairs of our head be pulled, we are pretty accurately sensible of the direction of the pulling by the movements imparted to the head.[41]But the feeling of the pull is localized, not in that part of the hair's length which the fingers hold, but in the scalp itself. This seems connected with the fact that our hair hardly serves at all as a tactile organ. In creatures withvibrissæ, however, and in those quadrupeds whose whiskers are tactile organs, it can hardly be doubted that the feeling is projected out of the root into the shaft of the hair itself. We ourselves have an approach to this when the beard as a whole, or the hair as a whole, is touched. We perceive the contact at some distance from the skin.

When fixed and hard appendages of the body, like the teeth and nails, are touched, we feel the contact where it objectively is, and not deeper in, where the nerve-terminations lie. If, however, the tooth is loose, we feel two contacts, spatially separated, one at its root, one at its top.

From this ease to that of a hard body not organically connected with the surface, but only accidentally in contact with it, the transition is immediate. With the point of a cane we can trace letters in the air or on a wall just as with the finger-tip; and in so doing feel the size and shape of the path described by the cane's tip just as immediately as, without a cane, we should feel the path described by the tip of our finger. Similarly the draughtsman's immediate perception seems to be of the point of his pencil, the surgeon'sof the end of his knife, the duellist's of the tip of his rapier as it plunges through his enemy's skin. When on the middle of a vibrating ladder, we feel not only our feet on the round, but the ladder's feet against the ground far below. If we shake a locked iron gate we feel the middle, on which our hands rest, move, but we equally feel the stability of the ends where the hinges and the lock are, and we seem to feel all three at once.[42]And yet the place where the contact isreceivedis in all these cases the skin, whose sensations accordingly are sometimes interpreted as objects on the surface, and at other times as objects a long distance off.

We shall learn in the chapter on Space that our feelings of our own movement are principally due to the sensibility of our rotatingjoints. Sometimes by fixing the attention, say on our elbow-joint, we can feel the movement in the joint itself; but we always are simultaneously conscious of the path which during the movement our finger-tips describe through the air, and yet these same finger-tips themselves are in no way physically modified by the motion. A blow on our ulnar nerve behind the elbow is felt both there and in the fingers. Refrigeration of the elbow produces pain in the fingers. Electric currents passed through nerve-trunks, whether of cutaneous or of more special sensibility (such as the optic nerve), give rise to sensations which are vaguely localized beyond the nerve-tracts traversed. Persons whose legs or arms have been amputated are, as is well known, apt to preserve an illusory feeling of the lost hand or foot being there. Even when they do not have this feeling constantly, it may be occasionally brought back. This sometimes is the result of exciting electrically the nerve-trunks buried in the stump.

"I recently faradized," says Dr. Mitchell, "a case of disarticulated shoulder without warning my patient of the possible result. For two years he had altogether ceased to feel the limb. As the current affected the brachial plexus of nerves he suddenly cried aloud, 'Oh the hand,—the hand!' and attempted to seize the missing member. The phantomI had conjured up swiftly disappeared, but no spirit could have more amazed the man, so real did it seem."[43]

Now the apparent position of the lost extremity varies. Often the foot seems on the ground, or follows the position of the artificial foot, where one is used. Sometimes where the arm is lost the elbow will seem bent, and the hand in a fixed position on the breast. Sometimes, again, the position is non-natural, and the hand will seem to bud straight out of the shoulder, or the foot to be on the same level with the knee of the remaining leg. Sometimes, again, the position is vague; and sometimes it is ambiguous, as in another patient of Dr. Weir Mitchell's who

"lost his leg at the age of eleven, and remembers that the foot by degrees approached, and at last reached the knee. When he began to wear an artificial leg it reassumed in time its old position, and he is never at present aware of the leg as shortened, unless for some time he talks and thinks of the stump, and of the missing leg, when ... the direction of attention to the part causes a feeling of discomfort, and the subjective sensation of active and unpleasant movement of the toes. With these feelings returns at once the delusion of the foot as being placed at the knee."

All these facts, and others like them, can easily be described as if our sensations might be induced by circumstances to migrate from theiroriginal localitynear the brain or near the surface of the body, and to appear farther off; and (under different circumstances) to return again after having migrated. But a little analysis of what happens shows us that this description is inaccurate.

The objectivity with which each of our sensations originally comes to us, the roomy and spatial character which is a primitive part of its content, is not in the first instance relative to any other sensation.The first time we open our eyes we get an optical object which isa place, but which is not yetplacedin relation to any other object, nor identified with any place otherwise known. It is a place with which so far we are onlyacquainted. When later we know that this same place is in 'front' of us, that only means that we have learned somethingaboutit, namely, that it iscongruent with thatotherplace, called 'front,' which is given us by certain sensations of the arm and hand or of the head and body. But at the first moment of our optical experience, even though we already had an acquaintance with our head, hand, and body, we could not possibly know anything about their relations to this new seen object. It could not be immediately located in respect ofthem. How its place agrees with the places which their feelings yield is a matter of which only later experience can inform us; and in the next chapter we shall see with some detail how later experience does this by means of discrimination, association, selection, and other constantly working functions of the mind. When, therefore, the baby grasps at the moon, that does not mean that what he sees fails to give him the sensation which he afterwards knows as distance; it means only that he has not learned at whattactile or manual distancethings which appear at thatvisual distanceare.[44]And when a person just operated for cataract gropes close to his face for far-off objects, that only means the same thing. All the ordinary optical signs of differing distances are absent from the poor creature's sensation anyhow. His vision is monocular (only one eye being operated at a time); the lens is gone, and everything is out of focus; he feels photophobia, lachrymation, and other painful resident sensations of the eyeball itself, whose place he has long since learned to know in tactile terms; what wonder, then, that the first tactile reaction which the new sensations provoke should be one associated with the tactile situation of the organ itself? And as for his assertions about the matter, what wonder, again, if, as Prof. Paul Janet says, they are still expressed in the tactile language which is the only one he knows. "To be touchedmeans for him to receive an impression without first making a movement." His eye gets such an impression now; so he can only say that the objects are 'touching it.'

"All his language, borrowed from touch, but applied to the objects of his sight, make us think that he perceives differently from ourselves,whereas, at bottom, it is only his different way of talking about the same experience."[45]

The other cases of translocation of our sensations are equally easily interpreted without supposing any 'projection' from a centre at which they are originally perceived. Unfortunately the details are intricate; and what I say now can only be made fully clear when we come to the next chapter. We shall then see that we are constantly selecting certain of our sensations asrealitiesand degrading others to the status ofsignsof these. When we get one of the signs we think of the reality signified; and the strange thing is that then the reality (which need not be itself a sensation at all at the time, but only an idea) is so interesting that it acquires an hallucinatory strength, which may even eclipse that of the relatively uninteresting sign and entirely divert our attention from the latter. Thus the sensations to which our joints give rise when they rotate are signs of what, through a large number of other sensations, tactile and optical, we have come to know as the movement of the whole limb. This movement of the whole limb is what wethink ofwhen the joint's nerves are excited in that way; anditsplace is so much more important than the joint's place that our sense of the latter is taken up, so to speak, into our perception of the former, and the sensation of the movement seems to diffuse itself into our very fingers and toes. But by abstracting our attention from the suggestion of the entire extremity we can perfectly well perceive the same sensation as if it were concentrated in one spot. We can identify it with a differently located tactile and visual image of 'the joint' itself.

Just so when we feel the tip of our cane against the ground. The peculiar sort of movement of the hand (impossible in one direction, but free in every other) which we experience when the tip touches 'the ground,' is a sign to us of the visual and tactile object which we alreadyknow under that name. We think of 'the ground' as being there and giving us the sensation of this kind of movement. The sensation, we say, comesfromthe ground. The ground's place seems to be its place; although at the same time, and for very similar practical reasons, we think of another optical and tactile object, 'the hand' namely, and consider thatitsplacealsomust be the place of our sensation. In other words, we take an object or sensible content A, and confounding it with another object otherwise known, B, or with two objects otherwise known, B and C, we identify its place with their places. But in all this there isno 'projecting'(such as the extradition-philosophers talk of) of A out of anoriginalplace; no primitive location which it first occupied,away fromthese other sensations, has to be contradicted; no natural 'centre,' from which it is expelled, exists. That would imply that A aboriginally came to us in definite local relations with other sensations, for to beoutof B and C is to be in local relation with them as much as to beinthem is so. But it was no more out of B and C than it was in them when it first came to us. It simply had nothing to do with them. To say that we feel a sensation's seat to be 'in the brain' or 'against the eye' or 'under the skin' is to say as muchaboutit and to deal with it in as non-primitive a way as to say that it is a mile off. These are all secondary perceptions, ways of defining the sensation's seatper aliud. They involve numberless associations, identifications, and imaginations, and admit a great deal of vacillation and uncertainty in the result.[46]

I conclude, then, that there is no truth in the 'eccentric projection' theory. It is due to the confused assumption that the bodily processes which cause a sensation must also be its seat.[47]But sensations have no seat in this sense. Theybecomeseats for each other, as fast as experience associates them together; but that violates no primitive seat possessed by any one of them. And though our sensations cannot then so analyze and talk of themselves, yet at their very first appearance quite as much as at any later date are they cognizant of all those qualities which we end by extracting and conceiving under the names ofobjectivity, exteriority,andextent. It is surely subjectivity and interiority which are the notionslatestacquired by the human mind.[48]

[1]Some persons will say that we never have a really simple object or content. My definition of sensation does not require the simplicity to be absolutely, but only relatively, extreme. It is worth while in passing, however, to warn the reader against a couple of inferences that are often made. One is that because we gradually learn to analyze so many qualities we ought to conclude that there are no really indecomposable feelings in the mind. The other is that because the processes that produce our sensations are multiple, the sensations regarded as subjective facts must also be compound. To take an example, to a child the taste of lemonade comes at first as a simple quality. He later learns both that many stimuli and many nerves are involved in the exhibition of this taste to his mind, and he also learns to perceive separately the sourness, the coolness, the sweet, the lemon aroma, etc., and the several degrees of strength of each and all of these things,—the experience falling into a large number of aspects, each of which is abstracted, classed, named, etc., and all of which appear to be the elementary sensations into which the original 'lemonade flavor' is decomposed. It is argued from this that the latter never was the simple thing which it seemed. I have already criticised this sort of reasoning in Chapter VI (see pp. 170 ff.). The mind of the child enjoying the simple lemonade flavor and that of the same child grown up and analyzing it are in two entirely different conditions. Subjectively considered, the two states of mind are two altogether distinct sorts of fact. The later mental state says 'this is thesame flavor (or fluid)which that earlier state perceived as simple,' but that does not make the two states themselves identical. It is nothing but a case of learning more and moreaboutthe same topics of discourse or things.—Many of these topics, however, must be confessed to resist all analysis, the various colors for example. He who sees blue and yellow 'in' a certain green means merely that when green is confronted with these other colors he sees relations ofsimilarity. He who sees abstract 'color' in it means merely that he sees a similarity between it and all the other objects known as colors. (Similarity itself cannot ultimately be accounted for by an identical abstract element buried in all the similars, as has been already shown, p. 492 ff.) He who sees abstract paleness, intensity, purity, in the green means other similarities still. These are all outward determinations of that special green, knowledgesaboutit,zufällige Ansichten, as Herbart would say, notelementsof its composition. Compare the article by Meinong in the Vierteljahrschrift für wiss. Phil., xii. 324.

[2]See Vol. I, p. 221.

[3]Those who wish a fuller treatment than Martin's Human Body affords may be recommended to Bernstein's 'Five Senses of Man,' in the International Scientific Series, or to Ladd's or Wundt's Physiological Psychology. The completest compendium is L. Hermann's Handbuch der Physiologie, vol. iii.

[4]"The sensations which wepostulateas the signs or occasions of our perceptions" (A. Seth: Scottish Philosophy, p. 89). "Their existence issupposedonly because, without them, it would be impossible to account for the complex phenomena which are directly present in consciousness" (J. Dewey: Psychology, p. 34). Even as great an enemy of Sensation as T. H. Green has to allow it a sort of hypothetical existence under protest. "Perception presupposes feeling" (Contemp. Review, vol. xxxi. p. 747). Cf. also such passages as those in his Prolegomena to Ethics, §§ 48, 49.—Physiologically, the sensory and the reproductive or associative processes may wax and wane independently of each other. Where the part directly due to stimulation of the sense-organ preponderates, the thought has a sensational character, and differs from other thoughts in the sensational direction. Those thoughts which lie farthest in that direction we callsensations, for practical convenience, just as we callconceptionsthose which lie nearer the opposite extreme. But we no more have conceptions pure than we have pure sensations. Our most rarefied intellectual states involve some bodily sensibility, just as our dullest feelings have some intellectual scope. Common-sense and common psychology express this by saying that the mental state is composed of distinct fractionalparts, one of which is sensation, the other conception. We, however, who believe every mental state to be an integral thing (Vol. I. p. 276) cannot talk thus, but must speak of the degree of sensational or intellectual character, or function, of the mental state. Professor Hering puts, as usual, his finger better upon the truth than any one else. Writing of visual perception, he says: "It is inadmissible in the present state of our knowledge to assert that first and last the same retinal picture arouses exactly the samepure sensation, but that this sensation, in consequence of practice and experience, is differentlyinterpretedthe last time, and elaborated into a different perception from the first. For the only realdataare, on the one hand, the physical picture on the retina,—and that is both times the same; and, on the other hand, the resultant state of consciousness (ausgeloste Empfindungscomplex)—and that is both times distinct.Of any third thing, namely, a pure sensation thrust between the retinal and the mental pictures, we know nothing. We can then, if we wish to avoid all hypothesis, only say that the nervous apparatus reacts upon the same stimulus differently the last time from the first, and that in consequence the consciousness is different too." (Hermann's Hdbch., iii. i. 567-8.)

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