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 146 easily to exclude the illusions of association; it is obvious, that such a man can obtain the idea of another body in motion, only by accompanying it with his hand; or by associating the ideas, on account of which he calls the hand, moved, with the body in question. By frequent operations of the hand, such as that described above, he becomes familiar with the idea of the hand moved. The ideas of the sensations, on account of which, he calls it moved, are easily raised, easily form themselves into combination, and easily associate themselves with the object, Hand. The idea of Hand, and the idea of Hand moved, having become very familiar, it is an easy case of association to transfer the term moved to other things, as the foot moved, the body moved, the stone moved. When he has become familiar with the application of Moved, as a connotative term, to various objects, it is easy, in this, as in other cases, to drop the connotation; and then he has the abstract, MOTION.[31] [32]
[31] The author correctly, in my opinion, refers to our muscular sensibility (aided by Touch), the fundamental notions of Resistance, Motion, Extension, Space. He also remarks properly, that the idea of motion and the idea of extension are the same; they are merely different modes of viewing one experience. In a mutually involved series of properties such as these, the Analysis may proceed in several different arrangements, no one being apparently very decisive. The following mode is suggested as on the whole, the most consecutive.
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 147 of consciousness, distinct from all modes of passive sensation, and from all forms of emotion. It is a kind of consciousness remarkably constant in its character; it varies in degree, but with this peculiarity that because a man is physically weaker than usual, he does not on that account exaggerate or misrepresent the degree of his muscular expenditure; the feeling of lifting two pounds is not made the same as the feeling of lifting four pounds, although in some of the incidents of exertion, as in the organic state of exhaustion, the smaller expenditure in one state is held to be equal to the greater expenditure in another state. The consciousness of putting forth power is the most uniform, the least variable, of all our sensibilities; the same amount of actual force expended is estimated as nearly the same under all circumstances.
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 148 confounded all modes of expended energy that are dynamically equal, we should be disqualified from attaining the ideas of motion and extension.
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.