But this reason, by some deemed conclusive, is nevertheless exceedingly futile; it labors under the sophism called by dialecticians begging of the question, for it supposes what was to be proved. The man destitute of all senses but that of touch will, indeed, experience the two sensations and their continuity; but what can he infer from them? Does he even know that he has either hand or forehead? Suppose him not to know, how is he to acquire this knowledge? Both sensations belong to him, and of this he is internally conscious; but whence they came, he knows not. Does the coincidence of the two sensations, perchance, prove something in favor of the existence of his forehead and hand, objects of which we suppose him to have no idea? If this coincidence proved what is pretended, with still greater reason would it prove the combination of some senses with others to elevate us to the knowledge of the existence of bodies, and consequently that this knowledge is not produced exclusively by touch. Whenever I have the sensation of the motion of placing my hand before my eyes, I find that I lose sight of the objects before me, and in their room is presented another always the same, my hand. If, from this coincidence, I infer the existence of external objects, the supremacy of touch is destroyed, for sight, also, acts a part in the formation of such a judgment. I also observe that when I have the sensation of clapping my hands together, I experience the sensation of hearing the noise of their contact; if, therefore, coincidence is of any account, hearing as well as touch comes in. What I say concerning the clapping of my hands, is applicable to what I experience when I pass a hand over any part of my body, for instance my arm, so as to produce some noise. In this case there are two sensations coincident and continuous.
It will, perhaps, be replied, that these examples refer to different senses, and produce sensations of different kinds. This, however, is of no consequence; for, if the being that perceives, infers the existence of objects from the coincidence of various sensations, the supremacy of touch is destroyed, which is what we undertook to demonstrate.
57. The sensation of the hand is not that of the forehead, for the one is warmer or colder, harder or softer than the other, and so the sensation caused by the hand upon the forehead will not be the same as that produced upon the hand by the forehead. It is to be observed, that the less difference we suppose between the two sensations, the less lively will be the perception of their duality, and consequently the less marked the coincidence on which the judgment is founded. Thus by rigorously analyzing this matter we discover that the diversity of sensations contributes in an especial manner to form judgments of the existence of objects, and therefore the combination of two senses will more conduce to this end than two sensations of one sense. Far, then, from its being necessary to consider touch as alone or superior upon this point, it is only to be held as auxiliary to the other senses.
In truth, it is almost beyond doubt that the sense of touch also requires the aid of the other senses, and that the judgments resulting from it are similar to those coming from the other senses. It is probable that only after repeated trials do we refer the sensation of touch to the object that causes it, or even to the part affected. The man who has had his arm amputated, feels pain as if he still preserved it; and this is because a repetition of acts has formed the habit of referring the cerebral impression to the point where the nerves transmitting it terminate. There is, therefore, no necessary relation between the sense of touch and the object; and this sense is, like the others, liable to illusions. Therefore, it is not exact to say that the idea of body springs up under our hand, if this be understood as excluding touch; for the same is true of the other senses, particularly of sight.
[CHAPTER XI.]
INFERIORITY OF TOUCH COMPARED WITH OTHER SENSES.
58. That superiority, or rather that exclusive privilege, conceded by Condillac and other philosophers to touch, not only has no foundation, as we have just seen, but seems to be in contradiction to the very nature of this sense. In short, it assigns the first place to the coarsest, the most material of all the senses.
It cannot be known what ideas a man reduced to the one sense of touch would form of things; but it seems to me that far from entering into clear and vivid communication with the external world, and finding a sufficient foundation whereon to base his cognitions, he would grope in the profoundest ignorance, and labor under the most transcendental errors.
59. If we compare touch with sight, or even with hearing and smell, we shall at once perceive a very important difference to its disadvantage. Touch transmits to us only impressions of objects immediately joining our body; whereas, the other three, and especially sight, place us in communication with far distant objects. The fixed stars are separated from us by a distance such as almost to pass our imagination, and yet we see them. Neither smell nor hearing, it is true, go so far; but the former fails not to warn us of the existence of a garden at many paces from us; and the latter gives us notice of a battle fought at many leagues distance, of the electric spark which has cloven the clouds on the confines of the horizon, or of the tempest roaring over the immensity of ocean.