"During the winter of 1858, while in Venice, I had the somewhat peculiar illusion which you request me to relate. I remember the circumstances very accurately because I have often repeated the story, and have made an effort to keep all the attendant circumstances clear of exaggeration. I was travelling with my mother, and we had taken rooms at a hotel which had been located in an old palace. The room in which I went to bed was large and lofty. The moon was shining brightly, and I remember standing before a draped window, thinking of the romantic nature of the surroundings, remnants of old stories of knights and ladies, and the possibility that even in that room itself love-scenes and sanguinary tragedies might have taken place. The night was so lovely that many of the people were strolling through the narrow lanes or so-called streets, singing as they went, and I laid awake for some time listening to these patrols of serenaders, and of course finally fell asleep. I became aware that some one was leaning over me closely, and that my own breathing was being interfered with; a decided feeling of an unwelcome presence of some sort awakened me. As I opened my eyes I saw, as distinctly as I ever saw any living person, a draped head about a foot or eighteen inches to the right, and just above my bed. The horror which took possession of my young fancy was beyond anything I have ever experienced. The head was covered by a long black veil which floated out into the moonlight, the face itself was pale and beautiful, and the lower part swathed in the white band commonly worn by the nuns of Catholic orders. My hair seemed to rise up, and a profuse perspiration attested the genuineness of the terror which I felt. For a time I lay in this way, and then gradually gaining more command over my superstitious terrors, concluded to try to grapple with the apparition. It remained perfectly distinct until I reached at it sharply with my hand, and then disappeared, to return again, however, as soon as I sank back into the pillow. The second or third grasp which I made at the head was not followed by a reappearance, and I then saw that the ghost was not a real presence, but depended upon the position of my head. If I moved my eyes either to the left or right of the original position occupied by my head when I awakened, the ghost disappeared, and by returning to about the same position, I could make it reappear with nearly the same intensity as at first. I presently satisfied myself by these experiments that the illusion arose from the effect of the imagination, aided by the actual figure made by a visual section of the moonbeams shining through the lace curtains of the window. If I had given way to the first terror of the situation and covered up my head, I should probably have believed in the reality of the apparition, since I have not by the slightest word, so far as I know, exaggerated the vividness of my feelings."
THE PHYSIOLOGICAL PROCESS IN PERCEPTION.
Enough, has now been said to prove the general law of perception, which is this, that _whilst part of what we perceive comes through our senses from the object before us, another part_ (and it may be the larger part) _always comes_ (in Lazarus's phrase) _out of our own head_.
At bottom this is only one case (and that the simplest case) of the general fact that our nerve-centres are an organ for reacting on sense-impressions, and that our hemispheres, in particular, are given us in order that records of our private past experience may co-operate in the reaction. Of course such a general way of stating the fact is vague; and all those who follow the current theory of ideas will be prompt to throw this vagueness at it as a reproach. Their way of describing the process goes much more into detail. The sensation, they say, awakens 'images' of other sensations associated with it in the past. These images 'fuse,' or are 'combined' by the Ego with the present sensation into a new product, the percept, etc., etc. Something so indistinguishable from this in practical outcome is what really occurs, that one may seem fastidious in objecting to such a statement, specially if have no rival theory of the elementary processes to propose. And yet, if this notion of images rising and flocking and fusing _be_ mythological (and we have all along so considered it), why should we entertain it unless confessedly as a mere figure of speech? As such, of course, it is convenient and welcome to pass. But if we try to put an exact meaning into it, all we find is that the brain reacts by paths which previous experiences have worn, and makes us usually perceive the probable thing, i.e., the thing by which on previous occasions the reaction was most frequently aroused.
But we can, I think, without danger of being too speculative, be a little more exact than this, and conceive of a physiological reason why the felt quality of an object changes when, instead of being apprehended in a mere sensation, the object is perceived as a thing. All consciousness seems to depend on a certain slowness of the process in the cortical cells. The rapider currents are, the less feeling they seem to awaken. If a region A, then, be so connected with another region B that every current which enters A immediately drains off into B, we shall not be very strongly conscious of the sort of object that A can make us feel. If B, on the contrary, has no such copious channel of discharge, the excitement will linger there longer ere it diffuses itself elsewhere, and our consciousness of the sort of object that B makes us feel will be strong. Carrying this to an ideal maximum, we may say that if A offer _no_ resistance to the transmission forward of the current, and if the current _terminate_ in B, then, no matter what causes may initiate the current, we shall get no consciousness of the object peculiar to A, but on the contrary a vivid sensation of the object peculiar to B. And this will be true though at other times the connection between A and B might lie less open, and every current _then_ entering A might give us a strong consciousness of A's peculiar object. In other words, just in proportion as associations are habitual, will the qualities of the suggested thing tend to substitute themselves in consciousness for those of the thing immediately there; or, more briefly, _just in proportion as an experience is probable will it tend to be directly felt._ In all such experiences the paths lie wide open from the cells first affected to those concerned with the suggested ideas. A circular after-image on the receding wall or ceiling is actually _seen_ as an ellipse, a square after-image of a cross there is seen as slant-legged, etc., because only in the process correlated with the vision of the latter figures do the inward currents find a pause (see the next chapter).
We must remember this when, in dealing with the eye, we come to point out the erroneousness of the principle laid down by Reid and Helmholtz that true sensations can never be changed by the suggestions of experience.
* * * * * A certain illusion of which I have not yet spoken affords an additional illustration of this. _When we will to execute a movement and the movement for some reason does not occur, unless the sensation of the part's_ NOT _moving is a strong one, we are apt to feel as if the movement had actually taken place._ This seems habitually to be the case in anæsthesia of the moving parts. Close the patient's eyes, hold his anæsthetic arm still, and tell him to raise his hand to his head; and when he opens his eyes he will be astonished to find that the movement has not taken place. All reports of anæsthetic cases seem to mention this illusion. Sternberg who wrote on the subject in 1885,[107] lays it down as a law that the intention to move is the same thing as the feeling of the motion. We shall later see that this is false (Chapter XXV); but it certainly may _suggest_ the feeling of the motion with hallucinatory intensity. Sternberg gives the following experiment, which I find succeeds with at least half of those who try it: Rest your palm on the edge of the table with your forefinger hanging over in a position of extreme flexion, and then exert your will to flex it still more. The position of the other fingers makes this impossible, and yet if we do not look to see the finger, we think we feel it move. He quotes from Exner a similar experiment with the jaws: Put some hard rubber or other unindentable obstacle between your back teeth and bite hard: you think you feel the jaw move and the front teeth approach each other, though in the nature of things no movement can occur.[108]--The visual suggestion of the path traversed by the finger-tip as the _locus_ of the movement-feeling in the joint, which we discussed on page 41, is another example of this semi-hallucinatory power of the suggested thing. Amputated people, as we have learned, still feel their lost feet, etc. This is a necessary consequence of the law of specific energies, for if the central region correlated with the foot give rise to any feeling at all it must give rise to the feeling of a foot.[109] But the curious thing is that many of these patients can _will the foot to move_, and when they have done so, distinctly _feel the movement to occur_. They can, to use their own language, 'work' or 'wiggle' their lost toes.[110] Now in all these various cases we are dealing with data which in normal life are inseparably joined. Of all possible experiences, it is hard to imagine any pair more uniformly and incessantly coupled than the volition to move, on the one hand, and the feeling of the changed position of the parts, on the other. From the earliest ancestors of ours which had feet, down to the present day, the movement of the feet must always have accompanied the will to move them; and here, if anywhere, habit's consequences ought to be found. The process of the willing ought, then, to pour into the process of feeling the command effected, and ought to awaken that feeling in a maximal degree provided no other positively contradictory sensation come in at the same time. In most of us, when the will fails of its effect there is a contradictory sensation. We discern a resistance or the unchanged position of the limb. But neither in anæsthesia nor in amputation can there be any contradictory sensation in the foot to correct us; so imagination has all the force of fact.
'APPERCEPTION.'
In Germany since Herbart's time Psychology has always had a great deal to say about a process called _Apperception_.[111] The incoming ideas or sensations are said to be 'apperceived' by 'masses' of ideas already in the mind. It is plain that the process we have been describing as perception is, at this rate, an apperceptive process. So are all recognition, classing, and naming; and passing beyond these simplest suggestions, all farther thoughts about our percepts are apperceptive processes as well. I have myself not used the word apperception because it has carried very different meanings in the history of philosophy,[112] and 'psychic reaction,' 'interpretation,' 'conception,' 'assimilation,' 'elaboration,' or simply 'thought,' are perfect synonyms for its Herbartian meaning, widely taken. It is, moreover, hardly worth while to pretend to analyze the so-called apperceptive performances beyond the first or perceptive stage, because their variations and degrees are literally innumerable. 'Apperception' is a name for the sum-total of the effects of what we have studied as association; and it is obvious that the things which a given experience will suggest to a man depend on what Mr. Lewes calls his entire psychostatical conditions, his nature and stock of ideas, or, in other words, his character, habits, memory, education, previous experience, and momentary mood. We gain no insight into what really occurs either in the mind or in the brain by calling all these things the 'apperceiving mass,' though of course this may upon occasion be convenient. On the whole I am inclined to think Mr. Lewes's term of 'assimilation' the most fruitful one yet used.[113] Professor H. Steinthal has analyzed apperceptive processes with a sort of detail which is simply burdensome.[114] His introduction of the matter may, however, be quoted. He begins with an anecdote from a comic paper.
"In the compartment of a railway-carriage six persons unknown to each other sit in lively conversation. It becomes a matter of regret that one of the company must alight at the next station. One of the others says that he of all things prefers such a meeting with entirely unknown persons, and that on such occasions he is accustomed neither to ask who or what his companions may be nor to tell who or what he is. Another thereupon says that he will undertake to decide this question, if they each and all will answer him an entirely disconnected question. They began. He drew five leaves from his note-book, wrote a question on each, and gave one to each of his companions with the request that he write the answer below. When the leaves were returned to him, he turned, after reading them, without hesitation to the others, and said to the first, 'You are a man of science'; to the second, 'You are a soldier'; to the third, 'You are a philologer'; to the fourth, 'You are a journalist'; to the fifth, 'You are a farmer.' All admitted that he was right, whereupon he got out and left the five behind. Each wished to know what question the others had received; and behold, he had given the same question to each. It ran thus: "'What being destroys what it has itself brought forth?'
"To this the naturalist had answered, 'vital force'; the soldier, 'war'; the philologist, 'Kronos'; the publicist, 'revolution'; the farmer, 'a boar'. This anecdote, methinks, if not true, is at least splendidly well invented. Its narrator makes the journalist go on to say: 'Therein consists the joke. Each one answers the first thing that occurs to him,[115] and that is whatever is most newly related to his pursuit in life. Every question is a hole-drilling experiment, and the answer is an opening through which one sees into our interiors.'...So do we all. We are all able to recognize the clergyman, the soldier, the scholar, the business man, not only by the cut of their garments and the attitude of their body, but by what they say and how they express it. We guess the place in life of men by the interest which they show and the way in which they show it, by the objects of which they speak, by the point of view from which they regard things, judge them, conceive them, in short by their mode of _apperceiving_...
"Every man has one group of ideas which relate to his own person and interests, and another which is connected with society. Each has his group of ideas about plants, religion, law, art, etc., and more especially about the rose, epic poetry, sermons, free trade, and the like. Thus the mental content of every individual, even of the uneducated and of children, consists of masses or circles of knowledge of which each lies within some larger circle, alongside of others similarly included, and of which each includes smaller circles within itself...The perception of a thing like a horse...is a process between the present horse's picture before our eyes, on the one hand, and those fused or interwoven pictures and ideas of all the horses we have ever seen, on the other;...a process between two factors or momenta, of which one existed before the process and was an old possession of the mind (the group of ideas, or concept, namely), whilst the other is but just presented to the mind, and is the immediately supervening factor (the sense-impression). The former apperceives the latter; the latter is apperceived by the former. Out of their combination an apperception-product arises: the knowledge of the perceived being as a horse. The earlier factor is relatively to the later one active and _a priori_; the supervening factor is given, _a posteriori_, passive...We may then define Apperception as the movement of two masses of consciousness (Vorstellungsmassen) against each other so as to produce a cognition.
"The _a priori_ factor we called active, the _a posteriori_ factor passive, but this is only relatively true...Although the _a priori_ moment commonly shows itself to be the more powerful, apperception-processes can perfectly well occur in which the new observation transforms or enriches the apperceiving group of ideas. A child who hitherto has seen none but four-cornered tables apperceives a round one as a table; but by this the apperceiving mass ('table') is enriched. To his previous knowledge of tables comes this new feature that they need not be four-cornered, but may be round. In the history of science it has happened often enough that some discovery, at the same time that it was apperceived, i.e. brought into connection with the system of our knowledge, transformed the whole system. In principle, however, we must maintain that, although either factor is both active and passive, the _a priori_ factor is almost always the more active of the two."[116] This account of Steinthal's brings out very clearly the _difference between our psychological conceptions and what are called concepts in logic_. In logic a concept is unalterable; but what are popularly called our 'conceptions of things' alter by being used. The aim of 'Science' is to attain conceptions so adequate and exact that we shall never need to change them. There is an everlasting struggle in every mind between the tendency to keep unchanged, and the tendency to renovate, its ideas. Our education is a ceaseless compromise between the conservative and the progressive factors. Every new experience must be disposed of under _some_ old head. The great point is to find the head which has to be least altered to take it in. Certain Polynesian natives, seeing horses for the first time, called them pigs, that being the nearest head. My child of two played for a week with the first orange that was given him, calling it a 'ball.' He called the first whole eggs he saw 'potatoes,' having been accustomed to see his 'eggs' broken into a glass, and his potatoes without the skin. A folding pocket-corkscrew he unhesitatingly called 'bad-scissors.' Hardly any one of us can make new heads easily when fresh experiences come. Most of us grow more and more enslaved to the stock conceptions with which we have once become familiar, and less and less capable of assimilating impressions in any but the old ways. Old-fogyism, in short, is the inevitable terminus to which life sweeps us on. Objects which violate our established habits of 'apperception' are simply not taken account of at all; or, if on some occasion we are forced by dint of argument to admit their existence, twenty-four hours later the admission is as if it were not, and every trace of the unassimilable truth has vanished from our thought. Genius, in truth, means little more than the faculty of perceiving in an unhabitual way.
On the other hand, nothing is more congenial, from babyhood to the end of life, than to be able to assimilate the new to the old, to meet each threatening violator or burster of our well-known series of concepts, as it comes in, see through its unwontedness, and ticket it off as an old friend in disguise. This victorious assimilation of the new is in fact the type of all intellectual pleasure. The lust for it is curiosity. The relation of the new to the old, before the assimilation is performed, is wonder. We feel neither curiosity nor wonder concerning things so far beyond us that we have no concepts to refer them to or standards by which to measure them.[117] The Fuegians, in Darwin's voyage, wondered at the small boats, but took the big ship as a 'matter of course.' Only what we partly know already inspires us with a desire to know more. The more elaborate textile fabrics, the vaster works in metal, to most of us are like the air, the water, and the ground, absolute existences which awaken no ideas. It is a matter of course that an engraving or a copper-plate inscription should possess that degree of beauty. But if we are shown a _pen_-drawing of equal perfection, our personal sympathy with the difficulty of the task makes us immediately wonder at the skill. The old lady admiring the Academician's picture, says to him: "And is it really all done _by hand_?"
IS PERCEPTION UNCONSCIOUS INFERENCE?
A widely-spread opinion (which has been held by such men as Schopenhauer, Spencer, Hartmann, Wundt, Helmholtz, and lately interestingly pleaded for by M. Binet)[118] will have it that _perception should be called a sort of reasoning operation, more or less unconsciously and automatically performed_. The question seems at first a verbal one, depending on how broadly the term reasoning is to be taken. If, every time a present sign suggests an absent reality to our mind, we make an inference; and if every time we make an inference we reason; then perception is indubitably reasoning. Only one sees no room in it for any unconscious part. Both associates, the present sign and the contiguous things which it suggests, are above-board, and no intermediary ideas are required. Most of those who have upheld the thesis in question have, however, made a more complex supposition. What they have meant is that perception is a _mediate_ inference, and that the middle term is unconscious. When the sensation which I have called 'this' (p. 83, _supra_) is felt, they think that some process like the following runs through the mind: 'This' is M; but M is A; therefore 'this' is A.[119] Now there seem no good grounds for supposing this additional wheelwork in the mind. The classification of '_this_' as M is itself an act of perception, and should, if all perception were inference, require a still earlier syllogism for its performance, and so backwards _in infinitum_. The only extrication from this coil would be to represent the process in altered guise, thus: 'This' is _like those_; _Those_ are A; Therefore 'this' is A.
The major premise here involves no association by contiguity, no _naming_ of _those_ as M, but only a suggestion of unnamed similar images, a recall of analogous past sensations with which the characters that make up A were habitually conjoined. But here again, what grounds of fact are there for admitting this recall? We are quite unconscious of any such images of the past. And the conception of all the forms of association as resultants of the elementary fact of habit-worn paths in the brain makes such images entirely superfluous for explaining the phenomena in point. Since the brain-process of 'this,' the sign of A, has repeatedly been aroused in company with the process of the full object A, direct paths of irradiation from the one to the other must be already established. And although roundabout paths may also be possible, as from 'this' to 'those,' and then from 'those' to 'A' (paths which would lead to practically the same conclusion as the straighter ones), yet there is no ground whatever for assuming them to be traversed now, especially since appearances point the other way. In _explicit_ reasoning, such paths are doubtless traversed; in perception they are in all probability closed. So far, then, from perception being a species of reasoning properly so called, both it and reasoning are co-ordinate varieties of that deeper sort of process known psychologically as the association of ideas, and physiologically as the law of habit in the brain. _To call perception unconscious reasoning is thus either a useless metaphor, or a positively misleading confusion between two different things._ * * * * * One more point and we may leave the subject of Perception. _Sir Wm. Hamilton thought that he had discovered a 'great law'_ which had been wholly overlooked by psychologists, and which, 'simple and universal,' is this: "Knowledge and Feeling,--Perception and Sensation, though always coexistent, are always in the inverse ratio of each other." Hamilton wrote as if perception and sensation were two coexistent elements entering into a single state of consciousness. Spencer refines upon him by contending that they are two mutually exclusive _states_ of consciousness, not two elements of a single state. If sensation be taken, as both Hamilton and Spencer mainly take it in this discussion, to mean the feeling of _pleasure_ or _pain_, there is no doubt that the law, however expressed, is true; and that the mind which is strongly conscious of the pleasantness or painfulness of an experience is _ipso facto_ less fitted to observe and analyze its outward cause.[120] Apart from pleasure and pain, however, the law seems but a corollary of the fact that the more concentrated a state of consciousness is, the more vivid it is. When feeling a color, or listening to a tone _per se_, we get it more intensely, notice it better, than when we are aware of it merely as one among many other properties of a total object. The more diffused cerebral excitement of the perceptive state is probably incompatible with quite as strong an excitement of separate parts as the sensational state comports. So we come back here to our own earlier discrimination between the perceptive and the sensational processes, and to the examples which we gave on pp. 80, 81.[121] HALLUCINATIONS.
Between normal perception and illusion we have seen that there is no break, the _process_ being identically the same in both. The last illusions we considered might fairly be called hallucinations. We must now consider the false perceptions more commonly called by that name.[122] In ordinary parlance hallucination is held to differ from illusion in that, whilst there is an object really there in illusion, _in hallucination there is no objective stimulus at all_. We shall presently see that this supposed absence of objective stimulus in hallucination is a mistake, and that hallucinations are often only _extremes_ of the perception process, in which the secondary cerebral reaction is out of all normal proportion to the peripheral stimulus which occasions the activity. Hallucinations usually appear abruptly and have the character of being forced upon the subject. But they possess various degrees of apparent _objectivity_. One mistake _in limine_ must be guarded against. They are often talked of as mental _images_ projected outwards by mistake. But where an hallucination is complete, it is much more than a mental image. _An hallucination is a strictly sensational form of consciousness, as good and true a sensation as if there were a real object there._ The object happens not to be there, that is all.
The milder degrees of hallucination have been designated as _pseudo-hallucinations_. Pseudo-hallucinations and hallucinations have been sharply distinguished from each other only within a few years. Dr. Kandinsky writes of their difference as follows: "In carelessly questioning a patient we may confound his pseudo-hallucinatory perceptions with hallucinations. But to the unconfused consciousness of the patient himself, even though he be imbecile, the identification of the two phenomena is impossible, at least in the sphere of vision. At the moment of having a pseudo-hallucination of sight, the patient feels himself in an entirely different relation to this subjective sensible appearance, from that in which he finds himself whilst subject to a true visual hallucination. The latter is reality itself; the former, on the contrary, remains always a subjective phenomenon which the individual commonly regards either as sent to him as a sign of God's grace, or as artificially induced by his secret persecutors...If he knows by his _own experience_ what a genuine hallucination is, it is quite impossible for him to mistake the pseudo-hallucination for it...A concrete example will make the difference clear: