It is necessary to take notice of this term, because the idea which is named by it is apt to present the appearance of something mysterious, though, after the expositions with which we are now familiar, the materials of which it is compounded, will not be difficult to find. The word Motion, is the abstract of Moving. What we have to investigate, therefore, are the sensations, on account of which, we call a body “moving;” motion being merely moving, the connotation dropped. All motion is in a Line, either a straight line, or some other line. The idea of “moving,” therefore, contains, for one ingredient, the idea of a line. A body “moving,” is a body which is successively at every point of a line. Every point of a line, as we have seen, is a particular position. A body “moving,” therefore, is a body first in one position, then in another, then in another, through a certain series. In the idea of a Body moving, then, we can enumerate the following particulars: the idea of a body, the idea of a position, the idea of a line, the idea of succession. These are all complex ideas; some of them highly complex; united into one idea, motion, they compose one of the most complex of all our It is commonly said, that motion includes the idea both of Space, and of Time. As it includes the idea of Succession, it includes the idea of Time, successions in the abstract (otherwise called instants), without end, receiving the name of Time. As it includes the idea of a Line, it includes the idea of extension in one direction. As it includes the idea of Position, which is that of lines, in every direction, it includes the idea of extension in every direction; but extension in every direction, taken abstractly, is Space. It is important to observe, that, though we receive, and that the most frequently, information of motions by the eye, it is not from the sensations of sight, that the idea of motion is derived. It is by association of ideas alone, that we fancy we see motion, as it is thence we fancy that we see figure, and distance. The classes of sensations, from which we derive the idea of motion, and the idea of extension, are the same; they are the muscular and tactual sensations. The man born blind, is not without the idea of motion, as he is without that of colour; on the contrary, he has the idea probably much more precise, than we who have entangled it inextricably with the perceptions of sight. To recur to the exposition which we have already given; we may remember, that the sensations (taking the simplest case), on account of which we apply the name Line, are partly sensations of Touch, partly sensations of Muscular Action. If we touch a line at one point with any part of our bodies, say the finger; so long as the finger is still, we have merely the Our ideas of extension and motion, are, no doubt, If any one shut his eyes, excluding as much as possible, the ideas of sight, and conceiving, without admixture, the feelings in the finger and the arm, while the finger passes along a line, he will get some notion of the series of antecedents and consequents, whence the idea of Motion is derived. They are feelings, which language does not enable us to communicate by words; but it does not seem very difficult for any man to raise the ideas of them in himself. Let any one suppose, that the line commences opposite to the centre of his body. He begins by touching it at that point with the finger of his right hand; and in this there is one state of feeling. He gives the finger the smallest perceptible motion towards the right: this is another state of feeling. He gives it a further motion, the smallest perceptible, in the same direction: this is another state of feeling; and so on, as far as the arm can reach. The antecedent states are in each instance united with the present by memory, and by the amount of the states, thus united, the amount of the motion is computed. Conceiving the case of a man born blind, the more The feeling of Resistance expresses what is probably the most fundamental state of all, the consciousness of muscular energy or expended force. Taking the case of a dead strain, or a pressure without movement, we have mere muscular energy and nothing else. We have an indivisible, unanalysable, mode In being conscious of expended energy, we discriminate its degrees, within certain limits; we know when we increase or diminish the amount; and our sensibility is measured by the smallness of the difference that makes a change in our consciousness. This discrimination is the basis of our estimate of the property termed Force, Resistance, Momentum, in moving bodies. Our idea of force is a muscular idea, an idea of muscular force of a certain amount. Force may be viewed in other ways, or from other aspects, but its direct and simple estimate is muscular energy in the dead strain. 2. We are farther conscious of muscular energy as more or less enduring or continuing. Our consciousness varies according as a strain is protracted; a weight supported half a minute gives a feeling different from a weight supported a quarter of a minute. Farther, it is important to remark that increase of continuance is not confounded with increase of force in the same time. Mechanically speaking, it is the same to us, whether we support two pounds one minute, or one pound two minutes; the energy gone out of us, the oxidation, or consumption of material, must be the same for both. But the consciousness is not the same for both; each has a character of its own, and we recognise the distinction in clear consciousness. If we When energy is accompanied by movement, there is a new and characteristic mode of consciousness, of vital importance. Energy in the dead strain and energy with motion may be equal as regard expended force, but they are not the same to our feelings. Continuance in the one is a different fact from continuance in the other. The feeling of continuance in moving energy is the fact that we call motion; and also the fundamental property, the starting point, with reference to Extension; although much more is wanted to complete that cognition. Mere dead strain would not amount to extension; and the discriminating of dead strain from moving strain is thus of essential moment. From the sense of this distinction, and the estimate of degree of continuance in movement, we begin at once the experience of motion and the ground-work of extension. The consciousness of continuance whether of dead strain or of movement is also a consciousness of duration, but not the only mode of becoming versed in this property. All our mental states,—whether muscular feelings, sensations, emotions, thoughts, volitions,—are different as they are more or less continued, and this consciousness of difference is a consciousness of Duration or Time. Hence the usual saying that Time is a property common to the Object and to the subject. The object experiences of motion and extension are the most convenient modes of measuring time, they are the most accurate and discriminative, but they are not the only nor the chief concrete embodiments of it. We often measure time by the duration and succession of our feelings and thoughts. 3. Another mode of discrimination inhering in our muscular consciousness is the degree of movement, as slow or quick. We are differently affected according to the rapidity of our movements; an accelerated pace in the arm, or in the whole body, sensibly alters our feelings. Farther, we do not compound this alteration with its dynamical equivalents in the It is at this point that Sensation comes to our aid. Passive sensation by itself is incompetent to give us the foundations of extension; through it, we have neither resistance nor movement, nor any fact partaking in what is essential to the extended or object universe. Mere warmth, odour, relish, touch, sound, colour, contain no elements of extension. The co-operation with moving energy is what introduces us to the object world. How then does Sensation aid muscularity in evolving Extension? In various ways, but chiefly thus. Our movements are not performed in vacuo, but in conjunction with sensation. The movements of the hand and arm, are usually conjoined with sensations of touch. We draw the hand across a table; there is an arm sensibility, purely motor or energetic, which is distinct from every mode of passive sensation. There accompanies it, however, a series of tactile sensations, making a united experience, active and passive. If this conjunction The supposition, hitherto, has been confined to Touch. When we take in sight, the scope for the operation is greatly enlarged. Almost all our movements are conjoined with optical changes—sensations of colour and of visible form in a certain sequence. We speedily detect a number of uniform occurrences of movement and visible sensation. The same movement gives the same series of appearances at all times; and an inverted movement corresponds with an inverted order. Here too we attain to a number of uniformities of coincidence, with the expectation of future occurrence. A certain movement of the eyes is accompanied with an optical series, as scanning the starry heavens; as often as the movement is repeated from the same stand-point, the optical series is repeated; the inverted movement gives the inverted series. We Our idea of extended things is thus completed by sensation. It is a series of conjunctions, or associations, of movements and sensations, in a fixed order. We do not in our idea of space, command an entire view at one glance; the successive perception of points or limited portions is what we begin with, and is the character of the mind’s working even after we are educated to the utmost. The co-existing in space, is the mind’s potentiality of finding definite sensations by means of definite movements; and it seems impossible to assign any other meaning or import to the phenomena. The genesis of the idea of space determines our mode of settling the great question of the Perception of a material world.—B. “On raising the arm to a horizontal position and keeping it so, and still more on dealing similarly with the leg, a sensation is felt, which, tolerably strong as it is at the outset, presently becomes unbearable. If the limb be uncovered, and be not brought against anything, this sensation is associated with no other, either of touch or pressure.” This is the sensation of Muscular Tension. “Allied to the sensation accompanying tension of the muscles, is that accompanying the act of contracting them—the sensation of muscular motion.… While, from the muscles of a limb at rest, no sensation rises; while, from the muscles of a limb in a state of continuous strain, there arises a continuous sensation which remains uniform for a considerable time; from the muscle of a limb in motion, there arises a sensation which is “When we express our immediate experiences of a body by saying that it is hard, what are the experiences implied? First, a sensation of pressure, of considerable intensity, is implied; and if, as in most cases, this sensation of pressure is given to a finger voluntarily thrust against the object, then there is simultaneously felt a correspondingly strong sensation of muscular tension. But this is not all: for feelings of pressure and muscular tension may be given by bodies which we call soft, provided the compressing finger follows the surface as fast as it gives way. In what then consists the difference between the perceptions? In this; that whereas when a soft body is pressed with increasing force, the synchronous sensations of increasing pressure and increasing muscular tension are accompanied by sensations of muscular movement; when a hard body is pressed with increasing force these sensations of increasing pressure and tension are not accompanied by sensations of muscular movement. Considered by itself, then, the perception of softness may be defined as the establishment in consciousness of a relation of simultaneity between three series of sensations—a series of increasing sensations of pressure; a series of increasing sensations of tension; and a series of sensations of motion. And the perception of hardness is the same, with omission of the last series.” (pp. 212, 218.) Of Extension; and first, of Form or Figure: “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 Next therefore, of Magnitude: “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 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.” (p. 226.) And finally, 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. “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 “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 position 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 In further prosecution of the analysis: “How do we become cognizant of the relative positions of two points on the surface of the body? Such two points, considered as coexistent, involve the germinal idea of Space. Such two points disclosed to consciousness by two successive tactual sensations proceeding from them, involve the germinal idea of Time. And the series of muscular sensations by which, when self-produced, these two tactual sensations are separated, involve the germinal idea of Motion. The questions to be considered then are—In what order do these germinal ideas arise? and—How are they developed? “… Taking for our subject a newly-born infant, let us call the two points on its body between which a relation is to be established, A and Z. Let us assume these points to be anywhere within reach of the hands—say upon the cheek. By the hypothesis, nothing is at present known of these points; either as coexisting in Space, as giving successive sensations in Time, or as being brought into relation by Motion. If, now, the infant moves its arm in such a way as to touch nothing, there is a certain vague reaction upon its consciousness—a sensation of muscular tension. This “Due attention having been paid to this fact, let us go on to consider what must happen when something touches, at the same moment, the entire surface between A and Z. This surface is supplied by a series of independent nerve-fibres, each of which at its peripheral termination becomes fused into, or continuous with, the surrounding tissue; each of which is affected by impressions falling within a specific area of the skin; and each of which produces a separate state of consciousness. When the finger is drawn along this surface these nerve-fibres A, B, C, D … Z, are excited in succession; that is—produce successive states of consciousness. And when something covers, at the same moment, the whole surface between A and Z, they are excited simultaneously; and produce what tends to become a single state of consciousness. Already I have endeavoured to shew in a parallel case, how, when impressions first known as having sequent positions in consciousness are afterwards simultaneously presented to consciousness, the sequent positions are transformed into coexistent positions, which, when consolidated by frequent presentations, are used in thought as equivalent to the sequent positions.f … As the series of tactual “The development of these nascent ideas, arising as it does from a still further accumulation and comparison of experiences, will be readily understood. What has been above described as taking place with respect to one relation of coexistent positions upon the surface of the skin—or rather, one “Not only must there gradually be established a connection in thought between each particular muscular series, and the particular tactual series, both successive and simultaneous, with which it is associated; and not only must there, by implication, arise a knowledge of the special muscular adjustments required to touch each special part, but, by the same experiences, there must be established an indissoluble connection between muscular series in general and series of sequent and coexistent positions in general, seeing that this connection is repeated in every one of the particular experiences. And when we consider the infinite repetition of these experiences, we shall have no difficulty in understanding how their components become so consolidated, that even when the hand is moved through empty space, it is impossible to become conscious of the muscular sensations, without becoming conscious of the sequent and coexistent positions—the Time and Space, in which it has moved. “Observe again, that as, by this continuous exploration of the surface of the body, each point is put in relation not only with points in some directions around it, but with points in all directions—becomes, as it were, a centre from which radiate lines of points known first in their serial positions before consciousness, and afterwards in their coexistent positions—it follows, that when an object of some size, as the hand, is placed upon the skin, the impressions from all parts of the area covered being simultaneously presented to consciousness, are placed in coexistent positions before These three different expositions of the origin of our ideas of Motion and Extension, by three eminent thinkers, agreeing in essentials, and differing chiefly in the comparative degrees of development which they give to different portions of the detail, will enable any competent reader of such a work as the present to fill up any gaps by his own thoughts. Many pages of additional commentary might easily be written; but they would not add any important thought to those of which the reader is now in possession; and belonging rather to the polemics of the subject than to its strictly scientific exposition, they would jar somewhat with the purely expository character of the present treatise. I will only further recommend to particular attention, the opinion of Mr. Spencer, also adopted by Mr. Bain, that our ascribing simultaneous existence to things which excite successive sensations, is greatly owing to our being able to vary or reverse the order of the succession. When we pass our hands |