Front Page Titles (by Subject) CHAPTER XII.: THE PERCEPTION OF BODY AS PRESENTING STATICAL ATTRIBUTES. - The Principles of Psychology
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CHAPTER XII.: THE PERCEPTION OF BODY AS PRESENTING STATICAL ATTRIBUTES. - Herbert Spencer, The Principles of Psychology 
The Principles of Psychology (London: Longman, Brown, Green and Longmans, 1855).
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THE PERCEPTION OF BODY AS PRESENTING STATICAL ATTRIBUTES.
§ 57. From that class of attributes known to us solely through one or other kind of objective activity; and from that further class known to us through some objective reactivity called forth by a subjective activity; we now pass to that remaining class known to us through a subjective activity only. In respect of its space-attributes—Bulk, Figure, and Position—body is altogether passive: and the perception of them is wholly due to certain mental operations, certain acts of thought. Unlike heat, sound, odour, &c., which are presented to consciousness by no acts of our own, but often in spite of them—unlike roughness, softness, pliability, &c., of which we become conscious by the union of our own acts with the acts of things; the phenomena of extension in their several modifications, are cognizable entirely through an internal co-ordination of impressions: a process in which the extended object has no share. Though the data through the interpretation of which its extension is known, are supplied by the object; yet, as those data are not the extension; and as until they are combined in thought the extension is unknown; it follows that extension is an attribute with which body does not impress us, but which we discover through certain of its other attributes. To an uncritical observer, the visible outlines of an object will perhaps seem to be as much thrust upon his consciousness by the object itself, as its colour is. But on remembering that these visible outlines are revealed to him only through certain modifications of light; that these modifications are produced not by the outlines, but by certain occult properties of the substance having these outlines; and that were these occult properties absent the outlines would be invisible; it will be seen that the outlines are known not immediately but mediately. And when it is further remembered that in the absence of light, the outlines of an object are knowable only through a series of tactile and muscular sensations gained by acts of exploration; and that consciousness of the outlines depends on the thinking of these in certain relations; it will no longer be questioned that in the perception of the space-attributes, the object is wholly passive, and the subject alone is active.
The propriety of distinguishing Bulk, Figure and Position as statical attributes, may perhaps be questioned: seeing that as applied in mechanics to signify respectively the phenomena of forces that produce equilibrium, and the phenomena of forces that produce motion, statics and dynamics are allied in nature, and pass the one into the other by insensible steps; whereas the attributes that are here classed as statical, differ wholly and irreconcilably from those classed as dynamical. The reply is, that the terms as now used are to be understood, not in the mechanical sense, but in a more general sense. The statical attributes are those which pertain to body as standing or existing. The dynamical ones are those which pertain to it as acting. Since it will not be denied that the so-called secondary attributes of body, which, as we find, imply its activities, are rightly termed dynamical; it must be admitted that the so-called primary ones, which, as implying passivity, are their antitheses, may be properly distinguished as statical.
§ 58. Whether the space-attributes of body are any of them knowable through the eyes alone, has been a disputed question. That our perceptions of distance are not originally visual, but result from muscular experiences, which visual ones serve to symbolize, is admitted. And that at least one out of the three dimensions of body, involving as it does the idea of greater or less remoteness from us, can be known only through muscular experiences, must also be admitted. But our inability to conceive of colour save as having extension of two dimensions, seems to imply that superficial magnitude is to a certain extent knowable by sight. Though it is perfectly manifest that superficial magnitude as known by sight, is purely relative—that the same surface, according as it is placed quite close to the eye or a quarter of a mile off, may occupy the whole field of view, or but an inappreciable portion of it; yet as, while an object is visible at all, it must present some length and breadth, it may be argued that superficial extension in the abstract, is originally perceivable through the eyes, as much as colour is. This conclusion, however, may be proved erroneous.
A little thought will show, that visible superficial extension is inconceivable without a simultaneous conception of distance. Imagine a surface a foot square to be placed a yard from the eye, at right angles to the axis of vision; and imagine further that four straight lines are drawn from its angles to the centre of the eye. Suppose now that a surface of six inches square be interposed at half the distance, so as to subtend to the eye the same apparent area; and that another of three inches square be interposed between this and the eye in the same manner; and so on continuously. It is manifest that were it possible to repeat this process ad infinitum, the area subtended by the four converging lines would disappear at the same moment that the distance from the point of convergence disappeared; and that hence, all our experiences conforming as they must to the laws of convergent rays, we can have no conception of a visible superficies without an accompanying conception of a distance between that superficies and the sentient surface. Or, to state the case more simply, and at the same time to avoid certain objections that may else be made—superficial extension cannot be conceived, except as the attribute of something separate from consciousness—something belonging, not to the mind, but to an object out of the mind. That is to say, it implies the idea of outness; or in other words the idea of distance. Hence, as it is admitted that distance is knowable only through experiences of motion, it follows that visible extension also, is knowable only through such experiences.
But a clearer understanding of the matter will be obtained, if we consider what is really given in a visual impression. The retina, as examined microscopically, presents, among other elements, a tesselated pavement made up of minute rods packed side by side, with their ends exposed so as to form its surface. As far as can be made out, each of these rods is supplied by a separate nerve; and is, as must be supposed, capable of independent stimulation. Though the hypothesis is not without difficulties, yet it is hardly doubted that these are the agents through whose joint action our visual impressions of form, &c., are obtained. That this joint action may be the more easily comprehended, let us suppose an analogous structure on a large scale. Imagine that an immense number of fingers could be packed side by side, so that their ends made a flat surface; and that each of them had a separate nervous connection with the same sensorium. If anything were laid upon the flat surface formed by these finger-ends, an impression of touch would be given to a certain number of them—a number great in proportion to the size of the thing. And if two things successively laid upon them differed not only in size but in shape, there would be a difference not only in the number of finger-ends affected, but also in the kind of combination. But now, what would be the interpretation of any impression thus produced, while as yet no experiences had been accumulated? Would there be any idea of extension? I think not. To simplify the question, let the first object laid upon these finger-ends be a straight stick; and let us name the two finger-ends on which its extremes lie A and Z. If now it be said that the length of the stick will be perceived, it is implied that the distance between A and Z is already known; or in other words, that there is a pre-existent idea of a special extension: which is absurd. If it be said that the extension is implied by the simultaneous excitation of B, C, D, E, F, and all the fingers between A and Z, the difficulty is not escaped; for no idea of extension can arise from the simultaneous excitation of these, unless there is a knowledge of their relative positions; which is itself a knowledge of extension. By what process then can the length of the stick become known? It can become known only after the accumulation of certain experiences, by which the series of fingers between A and Z becomes known. If the whole mass of fingers admits of being moved bodily, as the retina does; and if, in virtue of its movements, something now touched by finger A is next touched by finger B, next by C, and so on; and if these experiences are so multiplied by motion in all directions, that between the touching by finger A and by any other finger, the number of intermediate touches that will be felt is known; then the distance between A and Z can be known—known, that is, as a series of states of consciousness produced by the successive touchings of the intermediate fingers—a series of states comparable with any other such series, and capable of being estimated as greater or less. And when, by numberless repetitions, the relation between any one finger and each of the others is established, and can be represented to the mind as a series of a certain length; then we may understand how a stick laid upon the surface so as at the same moment to touch all the fingers from A to Z inclusive, will be taken as equivalent to the series A to Z—how the simultaneous excitation of the entire range of fingers, will come to stand for its serial excitation—how thus, objects laid upon the surface will come to be distinguished from each other by the relative lengths of the series they cover; or when broad as well as long, by the groups of series which they cover—and how by habit these simultaneous excitations, from being at first known indirectly by translation into the serial ones, will come to be known directly, and the serial ones will be forgotten: just as in childhood the words of a new language, at first understood by means of their equivalents in the mother tongue, are presently understood by themselves; and if used to the exclusion of the mother tongue, lead to the ultimate loss of it. The greatly magnified apparatus here described, being reduced to its original shape—the surface of finger-ends being diminished to the size of the retina; the things laid upon that surface being understood as the images cast upon the retina; and its movements in contact with these things, as the movements of the retina relatively to the images—some conception will be formed of one part of the process by which our ideas of visual extension are gained.
I say one part of the process, because this analysis carries us but a little way towards the solution. Those motions of the eye required to bring the sentient elements of the retina successively in contact with different parts of the image, being themselves known to consciousness, become components of the perception. So too do those motions required to produce due convergence of the visual axes; and those further motions required to adjust each eye to the proper focus. And even when the several series of states of consciousness thus resulting, have been combined with those which proceed from the retina itself, they can give no idea of extension as we understand it, until they are united with those locomotive experiences through which we gain the idea of outness or distance; and these are impossible without those accompanying tactile experiences that give the limits to distance. To examine in detail these various groups of elements which go to make up our perception of visible extension, would take up more space than can here be spared. Nor is it needful for the establishment of general principles that they should be thus examined. The foregoing analysis shows that leaving out of view other requirements (all of which involve motion, and the accompanying states of consciousness), no image cast upon the retina can be understood, or even distinguished from another image widely different in form, until relations have been established between the separate sensitive agents of which the retina is constructed; that no relation between any two such agents can be known otherwise than through the series of sensations given by intervening agents; that such series of sensations can be obtained only by motion of the retina; and that thus the primitive element out of which our ideas of visible extension are evolved, is a cognition of the relative positions of two states of consciousness in some series of such states consequent upon a subjective motion. Not that such relation between successive states of consciousness gives in itself any idea of extension. We have seen that a set of retinal elements may be excited simultaneously, as well as serially; that so, a quasi single state of consciousness becomes the equivalent of a series of states; that a relation between what we call coexistent positions thus represents a relation of successive positions; that this symbolic relation being far briefer, is habitually thought of in place of that it symbolizes; and that, by the continued use of such symbols, and the union of them into more complex ones, are generated our ideas of visible extension—ideas which, like those of the algebraist working out an equation, are wholly unlike the ideas symbolized; and which yet, like his, occupy the mind to the entire exclusion of the ideas symbolized.
The fact however which it now more particularly behoves us to remember, is, that underlying all cognitions of visible extension, is the cognition of relative position among the states of consciousness accompanying motion.
§ 59. Leaving here the visual perception of body as presenting statical attributes, let us pass to the tactile perception of it—to such perception of Form, Size, and Position, as a blind man has. And before proceeding to deal with this perception in its totality, let us look at its components: considering these first as known to us; and then in our mode of knowing them.
It is an anciently established doctrine that Form or Figure, which we may call the most complex mode of extension, is resolvable into relative magnitude of parts. An equilateral triangle is one of which the three sides are alike in magnitude. An ellipse is a symmetrical closed curve, of which the transverse and conjugate diameters are one greater than the other. A cube is a solid having all its surfaces of the same magnitude, and all its angles of the same magnitude. A cone is a solid, successive sections of which, made at right angles to the axis, are circles regularly decreasing in magnitude as we progress from base to apex. Any object described as narrow, is one whose breadth is of small magnitude when compared with its length. A symmetrical figure is a figure in which the homologous parts on opposite sides are equal in magnitude. Figures which we class as similar to each other, are such that the relation of magnitude between any two parts of the one, is equal to the relation of magnitude between the corresponding parts of the other. Add to which, that an alteration in the form of anything, is an alteration in the comparative sizes of some of its parts—a change in the relations of magnitude subsisting between them and the other parts; and that by continuously altering the relative magnitudes of its parts, any figure may be changed indefinitely. Hence, figure being wholly resolvable into relations of magnitude, we may go on to analyze that out of which these relations are formed—magnitude itself.
Though, in passing from a mode of extension which consists in relations of magnitude, and going on to consider magnitude itself, it would seem that relativity is no longer involved, this is not really the case. Of absolute magnitude we can know nothing. All magnitudes as known to us are thought of as equal to, greater than, or less than, certain other magnitudes—can be conceived in no other way. Not only is it that in speaking of a house as great, we mean, great in comparison with other houses; that in calling a man short, we mean, short in comparison with most men; and that in describing Mercury as small, and a certain pin's head as large, we mean, in comparison with planets and pins' heads respectively; but it is that no notion of magnitude can be formed, save one constructed out of the magnitudes given to us in experience, and therefore, thought of in relation to them. In what then consists the difference between figure and size as known to us? Simply in this: that whereas, in thinking of a thing's figure, we think of the relations of magnitude which its constituent parts bear to each other; in thinking of its size, we think of the relation of magnitude which it, as a whole, bears to other wholes. Still however, there remains the question—What is a magnitude considered analytically? The reply is—It consists of one or more relations of position. When we conceive anything as having a certain bulk, we conceive its opposite limiting surfaces as more or less removed from each other; that is—as related in position. When we think of a particular area, we think of a surface whose boundary lines stand to each other in specific degrees of remoteness; that is—are related in position. When we imagine a line of definite length, we imagine its termini as occupying points in space having some positive distance from each other; that is as related in position. As a solid is decomposable into planes; a plane into lines; lines into points; and as adjacent points can neither be known nor conceived as distinct from each other, except as occupying different places in space—that is, as occupying not the same position, but relative positions—it follows that every cognition of magnitude, is a cognition of one or more relations of position, which are presented to consciousness as like or unlike one or more other relations of position.
This analysis of itself brings us to the remaining space-attribute of body—Position. Like Magnitude, Position cannot be known absolutely; but can be known only relatively. The notion of position, is, in itself, the notion of relative position. The position of a thing is inconceivable, save by thinking of that thing as at some distance from one or more other things. The essential elements of the idea will be best seen, on observing under what conditions only, it can come into existence. Imagine a solitary point A, in infinite space; and suppose it possible for that point to be known by a being having no locality. What now can be predicated respecting its place? Absolutely nothing. Imagine another point B, to be added. What can now be predicated respecting the two? Still nothing. The points having no attributes save position, are not comparable in themselves; and nothing can be said of their relative position from lack of anything with which to compare it. The distance between them may be either infinite or infinitesimal, according to the measure used; and as, by the hypothesis, there exists no measure—as space contains nothing save these two points; the distance between them is unthinkable. But now imagine that a third point C, is added. Immediately it becomes possible to frame a proposition respecting their positions. The two distances A to B, and A to C, serve as measures to each other. The space between A and B may be compared with the space between A and C; and the relation of position in which A stands to B, becomes thinkable as like or unlike the relation in which A stands to C. Thus then, it is manifest that position is not an attribute of body in itself, but only in its connection with the other contents of the universe.
It remains to add, that relations of position are of two kinds: those which subsist between subject and object; and those which subsist between either different objects, or different parts of the same object. Of these the last are resolvable into the first. It needs but to remember, on the one hand, that in the dark a man can discover the relative positions of two objects only by touching first one and then the other, and so inferring their relative positions from his own position towards each; and on the other hand, that by vision no knowledge of their relative positions can be reached save through a perception of the distance of each from the eye; to see that ultimately, all relative positions may be decomposed into relative positions of subject and object.
These conclusions—that Figure is resolvable into relative magnitudes; that Magnitude is resolvable into relative positions; and that all relative positions may finally be reduced to positions of subject and object—will be fully confirmed on considering the process by which the space-attributes of body become known to a blind man. He puts out his hand, and touching something, thereby becomes cognizant of its position with respect to himself. He puts out his other hand, and meeting no resistance above, or on one side of, the position already found, gains some negative knowledge of the thing's magnitude—a knowledge which three or four touches on different sides of it serve to render positive. And then, by continuing to move his hands over its surface, he acquires a notion of its figure. What, then, are the elements out of which, by synthesis, his perceptions of magnitude and figure are framed? He has received nothing but simultaneous and successive touches. Each touch established a relation of position between his centre of consciousness and the point touched. And all he can know respecting magnitude and figure—that is, respecting the relative positions of these points to each other—is necessarily known through the relative positions in which they severally stand to himself.
Our perceptions of all the space-attributes of body, being thus decomposable into perceptions of position like that gained by a single act of touch; we have next to inquire what is contained in a perception of this kind. A little thought will make it clear that to perceive the position of anything touched, is really to perceive the position of that part of the body in which the sensation of touch is located. Whence it follows that our knowledge of the positions of objects, is built upon our knowledge of the positions of our members towards each other—knowledge both of their fixed relations, and of those temporary relations they are placed in by every change of muscular adjustment. That this knowledge is gained by a mutual exploration of the parts—by a bringing of each in contact with the others—by a moving over each other in all possible ways; and that the motions involved in these explorations, are known by their reactions upon consciousness; are propositions that scarcely need stating. But it is manifestly impossible to carry the analysis further without analysing our perception of motion. Relative position and motion are two sides of the same experience. We can neither conceive motion without conceiving relative position, nor discover relative position without motion. For the present, therefore, we must be content with the conclusion that, whether visual or tactual, the perception of every statical attribute of body is resolvable into perceptions of relative position which are gained through motion.
§ 60. Before defining in its totality, the perception of body as presenting statical attributes, it is necesssary to remark that the resisting positions which, as co-ordinated in thought, constitute our ideas of Figure or Magnitude, must be aggregated—must be continuous with an indefinite assemblage of intermediate resisting positions. If they are discontinuous—if they are separated by positions that do not resist, we have a perception not of one body, but of two or more.
Premising this, and omitting as doubly mediate our visual perceptions of extension in its several modes, we may say that the perception of body as presenting statical attributes, is a composite state of consciousness, having for its primary elements the indefinite impressions of resistance and extension, unconditionally united with each other and the subject in relations of coincidence in time and adjacency in space; and having for its secondary elements a series of relations between resisting positions, variously united with each other in relations of simultaneity and sequence that are severally conditional on the nature of the object and the acts of the subject, and all of them conditionally united with the primary elements by relations of sequence.
To which there is only to add, as before, that these being the materials of the perception, the process of perception consists in the unconscious classing of these impressions, relations, and conditions, with the like before-known ones.