Front Page Titles (by Subject) CHAPTER XVII.: PERCEPTION IN GENERAL. - The Principles of Psychology
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CHAPTER XVII.: PERCEPTION IN GENERAL. - Herbert Spencer, The Principles of Psychology 
The Principles of Psychology (London: Longman, Brown, Green and Longmans, 1855).
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PERCEPTION IN GENERAL.
§ 78. As foregoing chapters have made sufficiently manifest, the term Perception, is commonly applied to states of consciousness infinitely varied, and even widely different in nature. Between the consciousness of a vast landscape, and the consciousness of a minute dot on the surface of this paper, there exist countless gradations which pass insensibly one into another; and which yet unite extremes almost too strongly contrasted to be classed together. A perception may vary indefinitely in complexity, in degree of directness, and in degree of continuity. As in one of the primitive cognitions of resistance lately treated of, it may rise but a step above simple sensation. On the other hand, when watching the evolutions of a ballet, there is a consciousness not only of the multiplied relations of coexistent positions which constitute our notions of the distance, size, figure, and attitude of each dancer—not only of the various like relations between each and the several colours of her dress—not only of the relations of position among the respective dancers; but also, of the numerous relations of sequence which the body and limbs of every dancer exhibit in their movements with respect to each other; and of those yet more involved relations of sequence exhibited in the movements of every dancer with respect to the rest. In degree of directness, again, there is a similarly marked contrast between the perception that some surface touched by the finger is hard, and the perception that a building under whose walls we stand is a particular cathedral. The one piece of knowledge is almost immediate: the other is mediate in a double, a triple, a quadruple, and even in a still higher degree—mediate inasmuch as the solidity of the building is inferential; inasmuch as its proximity is inferential; inasmuch as its position, its size, its shape, are inferential; inasmuch as its artificial origin, its material, its hollowness, are inferential; inasmuch as its ecclesiastical purpose is an inference from these inferences; and inasmuch as the identification of it as a particular cathedral, is yet a still more remote inference resulting from the union of these inferences with those various others through which the locality is recognised. In like antithesis stand the degrees of continuity, in our respective perceptions of an electric spark, and the rush of a cataract which attracts our gaze. And when to these various facts, we add the further fact, that our perceptions, or at any rate our visual perceptions, are continuous in Space as well as in Time—that when looking at a landscape and turning our eyes to different parts of it, we cannot say how much is contained in each perception, or how many perceptions take in the panorama—that while only one particular point in the whole field of view is perceived with perfect distinctness, innumerable other points are perceived with degrees of distinctness imperceptibly decreasing as they recede from the central point, so that it is impossible to say where the perception ends—when we remember this, it will be abundantly manifest that the state of consciousness which we call a perception, cannot be rigorously marked out and separated; but that it merges insensibly into others of its own kind, both synchronous and successive, and into others which we class as of different kinds, both superior and inferior. It passes at the one extreme into reasoning; and at the other borders upon sensation. It may include innumerable relations simultaneously co-ordinated; or but a single relation. It cannot be demarcated from the nascent perceptions that coexist with it; nor (where the thing perceived is in motion) from the perceptions which follow it. So that, however convenient a term Perception may be for common purposes, it must not be understood as signifying any truly scientific division.
§ 79. The only valid distinction to be drawn, is that between Perception and Sensation. Though from time to time referred to with more or less distinctness by early philosophers, it is only in later times that this distinction has been currently acknowledged; and it is but recently that the relation between the two has been specifically formulated in the doctrine of Sir William Hamilton, “that, above a certain point, the stronger the Sensation, the weaker the Perception; and the distincter the perception the less obtrusive the sensation; in other words—though Perception proper and Sensation proper exist only as they coexist, in the degree or intensity of their existence they are always found in an inverse ratio to each other.” Before making any criticisms upon this doctrine, which seems to me rather an adumbration of the truth than the truth itself, it will be needful to state the exact meanings of Sensation proper and Perception proper.
Manifestly, every sensation, to be known as such, must be perceived—must become an object of perception; and hence, as thus considered, all sensations are perceptions. The mere physical affection of the organism does not constitute a sensation proper. While absorbed in thought, I may be subject to undue heat from the fire, uncomfortable pressure from a hard seat, or a continual noise from the street; and though my sentient organs are very decidedly affected, I may yet remain unconscious of the affections—may become conscious of them only when they pass a certain degree of intensity; and only then can be said to experience them as sensations. Moreover, not only in sensation proper, do I contemplate the organic affection as an affection of myself—as a state of consciousness standing in a certain relation to other states; but I also contemplate it as existing in a certain part of my body—as standing in certain relations of position. I perceive where it is. But though, under both these aspects, sensation must be regarded as one species of perception, it will readily be seen to differ widely from perception proper—from the cognition of an external object. In the one case, that which occupies consciousness is something contemplated as belonging to the ego: in the other, it is something contemplated as belonging to the non-ego. And these it is, which, as sensation proper and perception proper, are asserted to coexist in degrees of intensity that vary inversely.
That this is not altogether a correct assertion, will, I think, become apparent on carefully examining the facts as determined by experiment. Let the finger be brought against some hard rough body—say a broken stone, the back of a ribbed sea-shell, or anything capable of giving a tactile impression of some complexity. Between that degree of pressure used in ordinary touch, and the pressure that is painful from its intensity, there are many gradations; and Sir William Hamilton's doctrine implies that, beginning with the degree of pressure needful for distinct perception, and gradually increasing it until the pain becomes unbearable, the perception, step by step decreases in vividness, while the sensation, step by step increases in vividness; but that neither at the beginning nor the end, does the one exclude the other. Do the facts correspond with this statement? I think not. During the ordinary gentle pressure, it will be found that consciousness is occupied entirely about the surface and its irregularities; that no thought is taken of the sensations through which the surface and its irregularities are known; that to attend to these sensations rather than to the objective phenomenon implied by them, requires a decided effort; and that when they are thought of, it is in another state of consciousness quite distinct from the previous one. If the pressure be gradually increased, there is not a gradual decrease in the vividness of the perception and an increase in the vividness of the sensation, but the consciousness remains, as before, occupied about the surface; the hardness and roughness of which, become the peculiarities most contemplated as the pressure becomes greater: and though the sensation may be more easily thought of than before, and is more distinctly realized when it is thought of, still, it can be thought of only in a second state of consciousness not included in the original one. But now, if the pressure be increased so far as to produce decided pain, there will occur quite a different state of consciousness, in which the thing contemplated is the subjective affection and not its objective cause. When the pain reaches any considerable intensity, it will be found that the perception has not only altogether ceased, but that it can be recalled into consciousness only by an effort. And it will be very clearly perceived that were the nature of the object producing the painful pressure, not already known, it would be entirely unknowable. Generalizing the facts then, it would seem, not so much that Sensation and Perception vary inversely, as that they exclude each other with varying degrees of stringency. When the sensations (considered simply as physical changes in the organism) are weak, the objective phenomenon signified by them is alone contemplated: the sensations are altogether excluded from consciousness, and cannot be brought into it without a decided effort. When the sensations are rendered somewhat more intense, the perception still remains equally vivid—still remains the sole occupant of consciousness; but as, by their increasing intensity, the sensations tend to force themselves into consciousness, it requires less effort than before to make them the subject of thought. Gradually as the intensity of the sensations is further increased, a point is approached at which consciousness is as likely to be occupied by them, as by the external fact they imply—a point at which either can be thought of with equal facility, and at which each tends in the greatest degree to draw attention from the other. If the intensity of the sensations be yet further increased, they begin to occupy consciousness to the exclusion of the perception, which, however, can still be brought into consciousness by a slight effort. But, finally, if the sensations rise to extreme intensity, consciousness becomes so absorbed by them, that it is impossible without great effort, if at all, to think of the thing causing them.∗
What now is the real nature of this mutual exclusion? Is it not an instance of the general fact that consciousness cannot be in two distinct states at the same time? I cannot know that I have a sensation, without, for the moment, having my attention occupied solely with that sensation: I cannot know the external thing causing it, without, for the moment, having my attention occupied solely with that external thing: and as either cognition rises, the other ceases. If, as Sir William Hamilton asserts, the two cognitions always coexist, though in inverse intensities, then it must happen, that if, beginning at either extreme, the conditions be slowly changed, so that while the cognition most distinctly present to the mind becomes gradually less distinct, the other becomes gradually more distinct; there must arrive a time when they will be equally distinct—when the subjective and objective phenomena will be thought of together with equal clearness; which is impossible. It is very true, as shown above, that under such change of conditions, there arrives a time when the subjective and objective phenomena attract the attention in equal degrees, and are thought of alternately with equal facility. And it may even be admitted that while either is being thought of, the other is nascent in thought. But this is quite a different thing from saying that they occupy consciousness together.
Perception proper and sensation proper, will however be best understood, and the purpose of the present chapter most furthered, by considering their antagonism under the light of preceding analyses. In all cases it has been found that perception is an establishment of specific relations among states of consciousness; and is so distinguished from the establishment of the primary states of consciousness themselves. While in apprehending a sensation, the mind is occupied with a single subjective affection; in apprehending the external something producing it, the mind is occupied with the relation or relations between that affection and others, either past or present. The sensation cannot be known save as an undecomposable state of consciousness. The outward object cannot be known save as a decomposable state of consciousness; which is recognized as such or such, in virtue of the special manner in which the component states are united. Now the contemplation on the one hand of a special state of consciousness, and on the other of the special relations among states of consciousness, are quite different mental acts—acts which may be performed in immediate succession, but not together. To know a relation is not simply to know the terms between which it subsists. Though when the relation is perceived, the terms are nascently perceived, and conversely, yet introspection will show that there is a distinct transition in thought from the terms to the relation, and from the relation to the terms. That the whole matter centres in the question—How do we think of a relation as distinguished from the terms between which it subsists? will be plain from the fact that Sir William Hamilton, while implying that it is something more, himself says that in one respect, “perception proper is an apprehension of the relations of sensations to each other.” Joining which doctrine with the one contended against, we see that, according to his hypothesis, the sensations and the relations between them, can be simultaneously thought of with equal degrees of distinctness, or with any other relative degrees of distinctness—a manifestly untenable proposition.
The only further remark here called for, is, that perception cannot be correctly defined as “an apprehension of the relations of sensations to each other”; for that in most perceptions some of the elements are not presented but represented in consciousness. When passing the finger over a rough surface, the perception contains very much more than the co-ordinated sensations immediately experienced. Besides these it contains the remembered visual impressions produced by such a surface; which cannot be kept out of the mind; and in the suggestion of which the perception largely consists. Again, when gazing at some one object, it will be found that objects on the outskirts of the field of view, are recognized more by representation than by presentation. If, without moving his eyes, the observer asks himself what he actually perceives of these outlying objects, he will find that they impress him simply as ill-defined patches of colour; that were it not for his previous experiences, he would not know the meanings of these patches; and that in perceiving what the objects are, he ekes out the vaguely presented impressions with some comparatively distinct represented ones. And what thus manifestly happens with perceptions of this order, happens in one form or other with all perceptions. In fact, when analyzed to the bottom, all perceptions prove to be acquired perceptions. From its simplest to its most complex forms, perception is essentially a diagnosis.
§ 80. Finally, to express in its most general form the truth that has been variously illustrated in detail—Perception is a discerning of the relation or relations between states of consciousness, partly presentative and partly representative; which states of consciousness are themselves known only to the extent involved in the knowledge of their relations.
Under its simplest form—a form however of which the adult mind has few if any examples—perception is the consciousness of a single relation. More commonly, a number of relations are simultaneously presented and represented; and the relations between these relations are cognized. Most frequently, the relations of relations of relations are the objects of perception: as when any neighbouring solid body is regarded. And very often—as when observing the motions of an animal, which are known to us as the relations between certain highly complex relations of position now present, and certain others just past—a still more abstract relativity is contemplated.
Further it is to be noticed, that in the ascending grades of perception, there is an increase not only in the number and abstractness of the relations grasped together, but also in the variety of their kinds. Numerous relations of position, of extension, of coexistence, of sequence, of degree in all sensible qualities, are co-ordinated in one thought; or what appears to us such.
Add to which that, as heretofore pointed out in each special case, the act of perception is the establishment of a relation of likeness between the particular relation or group of relations contemplated, and some past relations or groups of relations—the assimilation of it to such past relations or groups of relations—the classing of it with them.
§ 81. And now it remains only to apply the analysis thus far pursued, to the relations themselves. By a continued process of decomposition we have found that our intellectual operations severally consist in the establishment of relations, and groups of relations, among the primitive undecomposable states of consciousness, produced in us by our own actions and the actions of surrounding things. But what are these relations? They can be nothing more than certain secondary states of consciousness, produced by the union of the primary states. Unable as we are to transcend consciousness, we can know a relation only as some modification of consciousness. The original modifications of consciousness are the feelings produced in us by subjective and objective activities; and any further modifications of consciousness must be such as result from combinations of these original ones. In all their various kinds and compounds, what we call relations, can be to us nothing more than the modes in which we are affected by the comparison of sensations, or remembered sensations, or both. Hence what we have next to do, is, first to resolve the special kinds of relations into the more general kinds; and then to ascertain what are the ultimate phenomena of consciousness which the primordial relations express.
[∗]Those who wish to test this statement experimentally, should remember that the mere act of observing the current phenomena of consciousness, itself introduces a new element into consciousness, which tends more or less to disturb the processes going on. The observations should be made obliquely rather than directly—should if possible be made, not during, but immediately after, the appropriate experiences.