De Anima

The same account is to be given of touch and the tangible. If touch is not a single sense but includes more senses than one, there must be a plurality of tangible objects also. It is a question whether touch is several senses or only one. What, moreover, is the sense-organ for the faculty of touch? Is it the flesh or what is analogous to this in creatures that have not flesh? Or is flesh, on the contrary, the medium, while the primary sense-organ is something different, something internal? We may argue thus: every sense seems to deal with a single pair of opposites, sight with white and black, hearing with high and low pitch, taste with bitter and sweet; but under the tangible are included several pairs of opposites, hot and cold, dry and moist, hard and soft and the like. A partial solution of this difficulty lies in the consideration that the other senses also apprehend more than one pair of opposites. Thus in vocal sound there is not only high and low pitch, but also loudness and faintness, smoothness and roughness, and soon. In regard to colour also there are other similar varieties. But what the one thing is which is subordinated to touch as sound is to hearing is not clear.

But is the organ of sense internal or is the flesh the immediate organ? No inference can be drawn, seemingly, from the fact that the sensation occurs simultaneously with contact. For even under present conditions, if a sort of membrane were constructed and stretched over the flesh, this would immediately on contact transmit the sensation as before. And yet it is clear that the organ of sense is not in this membrane; although, if by growth it became united to the flesh, the sensation would be transmitted even more quickly. Hence it appears that the part of the body in question, that is, the flesh, is related to us as the air would be if it were united to us all round by natural growth. We should then have thought we were perceiving sound, colour and smell by one and the same instrument: in fact, sight, hearing and smell would have seemed to us in a manner to constitute a single sense. But as it is, owing to the media, by which the various motions are transmitted, being separated from us, the difference of the organs of these three senses is manifest. But in regard to touch this point is at present obscure.

In fact, the animate body cannot consist of air or water singly, it must be something solid. The only alternative is that it should be a compound of earth and of these elements, as flesh and what is analogous to flesh profess to be. Consequently the body must be the naturally cohering medium for the faculty of touch, through which the plurality of sensations is communicated. That they are a plurality is made clear by touch in the case of the tongue, for the tongue perceives all tangible objects, and that at the same part at which it perceives flavour. Now, if the rest of the flesh also had perception of flavour, taste and touch would have seemed to be one and the same sense: whereas they are really two, because their organs are not interchangeable.

Here a question arises. All body has depth, this being the third dimension, and, if between two bodies a third body is interposed, the two cannot touch one another. Now that which is fluid is not independent of body, nor is that which is wet: if it is not itself water, it must contain water. But when bodies touch one another in the water, since their exterior surfaces are not dry, there must be water between them, the water with which their extremities are flooded. If, then, all this be true, no one thing can possibly touch another in the water, nor yet in the air: for the air stands to the objects in the air as water to the things in water, but this fact we are more apt to overlook, just as aquatic animals fail to notice that the things which touch one another in the water have wet surfaces. The question then arises: is the mode of perception uniform for all objects or does it differ for different objects? According to the prevalent view, taste and touch operate by direct contact, while the other senses operate at a distance. But this view ts incorrect. On the contrary, we perceive the hard and the soft also mediately, just as much as we do the resonant, the visible, the odorous. But the latter are perceived at a distance, the former close at hand: and this is why the fact escapes us, since we really perceive all objects through a medium, though in touch and taste we fail to notice this. And yet, as we mentioned above, even if we perceived all objects of touch through a membrane without being aware of its interference, we should be just in the same position as we are now with regard to objects in the water or in the air: for, as it is, we suppose that we are touching the objects themselves and that there is no intervening medium. But there is this difference between the tangible on the one hand and visible and resonant things on the other: the latter we perceive because the medium acts in a certain way upon us, while tangible objects we perceive not by any action upon us of the medium, but concurrently with it, like the man who is struck through his shield. It is not that the shield was first struck and then passed on the blow, but, as it happened, both were struck simultaneously. And, generally, it would seem that the flesh and the tongue are related

to the true sense-organ as are air and water to the organs of sight, hearing and smell respectively. But neither in the one case nor in the other would sensation follow on contact with the sense-organ; for instance, if a body that is white were placed on the outer surface of the eye: which shows that the instrument that apprehends the tangible is within. We should then get the same result as in the case of the other senses. What is placed on the sense-organ we do not perceive: what is placed on the flesh we do perceive: therefore flesh is the medium for the faculty of touch.

It is, then, the distinctive qualities of body as body which are the objects of touch: I mean those qualities which determine the Clements, hot or cold, dry or moist, of which we have previously given an account in our discussion of the elements. And their sense-organ, the tactile organ, that is, in which the sense called touch primarily resides, is the part which has potentially the qualities of the tangible object. For perceiving is a sort of suffering or being acted upon: so that when the object makes the organ in actuality like itself it does so because that organ is potentially like it. Hence it is that we do not perceive what is just as hot or cold, hard or soft, as we are, but only the excesses of these qualities: which implies that the sense is a kind of mean between the opposite extremes in the sensibles. This is why it passes judgment on the things of sense. For the mean is capable of judging, becoming to each extreme in turn its opposite. And, as that which is to perceive white and black must not be actually either, though potentially both, and similarly for the other senses also, so in the case of touch the organ must be neither hot nor cold. Further, sight is in a manner, as we saw, of the invisible as well as the visible, and in the same way the remaining senses deal with opposites. So, too, touch is of the tangible and the intangible: where by intangible is meant, first, that which has the distinguishing quality of things tangible in quite a faint degree, as is the case with the air; and, secondly, tangibles which are in excess, such as those which are positively destructive. Each of the senses, then, has now been described in outline.