Lecture 22 — Touch: its medium and whether it is one sense or many

The same reasoning holds for the tangible and touch. If touch is not one sense, but several, then the tangible sense-objects must necessarily be several. But it is a problem whether it is one sense or several; and what is sensitive of the tangible—whether it is the flesh, or what corresponds to flesh in other animals, or not; and if not, then this flesh would be the medium, while the primary sense organ would be something else within.

For every sense seems to be of a single contrariety, as sight of white and black, hearing of high and low, taste of sweet and bitter. But in the tangible order, there are several contrarieties, hot and cold, dry and wet, hard and soft, and the like.

There is a partial solution of this problem: that in other senses also there are several contraries; as in voice, there is not only high and low but also loud and soft, smooth and rough, and other such qualities. There is also a like variety of differences in color.

But it is not clear what is the underlying unity of touch, as sound is of hearing.

The fact that sensation arises simultaneously with contact is not a sign of whether the sense organ is interior or is the flesh immediately. For if, as things are, one were to stretch a covering or membrane over the skin, a sensation would still arise immediately on making contact; yet it is obvious that the sense organ was not in this membrane. And if it were connatural, the sensation would reach the sense even sooner.

Therefore it appears that the relation of this part of the body to the whole is comparable to that which air would have if it formed a natural covering that grew all round our bodies.

For then it would appear that we sensed sound and odor and color through a single common medium, and even that there were but one sense for hearing, seeing, and smelling. Since in fact, however, there exists something determinate through which the motions are produced, it is evident that each of these senses is diverse.

But in the case of touch, this is still far from clear. It is impossible that an ensouled body be constituted from air or water, for it must be solid. It can, then, only be a mixture from earth and the other elements, as flesh (or its counterpart) requires. Wherefore it is necessary that the medium of touch be a body naturally joined to the organism through which its sensations, which are many, come about.

That they are several is proved by the fact that there are several kinds of touch in the tongue; for that same member feels all tangible objects, as well as flavor. If, then, every part of the flesh sensed flavor, it would seem that touch and taste were one and the same. But now we know that they are two, in that one organ cannot be substituted for the other.

517. The same reasoning holds (422b17). Having considered the objects of the other senses, the Philosopher finally treats of the object of touch, examining this sense last of all because it appears to be the least spiritual of the senses, though it is the foundation of all the others. This section divides into two parts.

In the first part, he settles certain questions about the sense of touch.

In the second, he states the truth about this sense, at it would seem then in general (423b17; [545]).

About the first, he does two things.

First, he raises questions;

second, he gives a solution to the problems in question, at for every sense (422b23; [519]).

He observes then, first, that in the matters to be examined, the same reasoning holds whether we treat of the tangible or of touch. For what is said of one holds good of the other; and if touch is not one sense, but several, then the tangible must be not one genus of sense-object, but several. This he says because, while his intention is to define the sense-object first and after that the sense itself, in the case of touch, he is going first to inquire into the sense; and this is because the questions he wants to answer are more conveniently dealt with in this way than by treating first of the tangible object. So he prefaces his remarks with a kind of explanation, asserting that it does not matter whether we speak of the tangible or of touch.

518. Of the two questions about touch and the tangible, the first is whether the sense of touch is several senses or only one; and the second is, what is sensitive of the tangible, that is, the organ of sensing? That is, whether flesh is the organ of touch in animals that have flesh (which are those that have blood), and, in other animals that lack blood, something analogous to flesh; or, on the contrary, is flesh, or what corresponds to flesh, merely the medium of the sense of touch, while its primary organ is something internal, close to the heart? The second opinion is the one maintained in On Sense and What is Sensed. (Aristotle, On Sense and What is Sensed, ch. 2, 439a1–2; cf. Aquinas, Commentary on Aristotle’s On Sense and What is Sensed, ch. 5.)

519. Next, at for every sense seems (422b23), he begins to answer these questions.

And first, regarding the first;

second, the second, at the fact that sensation (422b34; [525]).

With regard to the first, he does three things.

First, he gives an argument for the view that there are not one but several senses of touch;

second, he presents a solution to the problem, at there is a partial solution; (422b27; [520]);

third, he criticizes this solution, at but it is not (422b31; [521]).

The preliminary argument runs as follows: every single sense seems to be of a single contrariety, as sight of white and black, hearing of high and low, taste of sweet and bitter; but included in the tangible, which is the object of touch, are several contrarieties, hot and cold, moist and dry, hard and soft, and others of the same kind, besides heavy and light, sharp and blunt, and so on. Therefore, touch is not one sense but several.

520. Then, at there is (422b27), he gives what might seem to be a solution, saying that one might have a solution to the aforementioned problem in that even in the other senses there appear to be several contrarieties, for example, in hearing; for in the voice, one can observe not only the contrariety of high and low, but that also of loud and soft, smooth and rough, and other such qualities.

Similarly, color presents various differences besides the contrariety of black and white, as that one color is intense, another dim, one beautiful, another ugly. Yet these facts do not mean that either vision or hearing is not a single sense; nor then need the tangible’s many contrarieties imply that touch is not a single sense.

521. Then, at but it is not clear (422b31), he sets aside this solution, saying that there is an underlying unity of all the contraries which are in the audible, that is, sound; and so too with color in the visible. But no common subject can be found which is common to all the contraries connected with touch; hence there does not seem to be one genus of the tangible, and nor does there seem to be one sense of touch.

522. To understand this passage, we must consider that there is a proportion involved in the distinction between powers and objects: if a single sense is a single potency, the corresponding object must be a single genus. Now, it is shown in Metaphysics 10 that each genus includes one primary contrariety. (Aristotle, Metaphysics 10.4, 1055a23–33; cf. Aquinas, Commentary on Metaphysics, bk. 10, lect. 5–6, nn. 2023–58.) Hence there must be one primary contrariety in the object of any one sense, and that is why the Philosopher says here that one sense is of one contrariety.

523. However, it is possible for one genus to include several contrarieties beside the primary one, and this either by a process of subdivision—as in the genus body, the first contrariety is between ensouled and not ensouled; and since ensouled bodies are divided into the sensitive and non-sensitive, and the sensitive yet again into rational and non-rational, contrarieties multiply in the genus body—or accidentally, as, to take the genus body again, we find the contrariety of white and black, not to mention all the other bodily accidental qualities. It is in this way that we must understand, as regards sound and voice, that, besides the primary contrariety of high and low, which is essential, there are other accidental contrarieties.

524. Now, in the genus of tangible things, there are several essential primary contrarieties, which can all in a way be traced back to a single subject, but in another way not. For in one way, the subject of the contrariety can be found in the genus, which is related to the various contrary differences as potency is related to act. In another way, the subject of the contraries can be found in the substance that is the subject of the genus in which the contraries are included—as when we call a colored body the subject of black and of white. Speaking, then, of the subject that is the genus, it is plain that there is no one same subject of all tangible qualities. But speaking of the subject that is the substance, there is one subject of all these, that is, the body that pertains to what constitutes the animal. This is why the Philosopher will say that tangible qualities belong to body precisely as body, that is, they are the qualities by which the elements of body are distinguished from one another. (Lect. 23, n. 546.) For the sense of touch discriminates among the things that pertain to the constitution of the animal’s body. Hence, formally speaking, and according to its account, the sense of touch is not one sense, but several; but it is one in its subject.

525. Next, at the fact that sensation (422b34), he deals with the second question; and this, in two stages.

First, he states the true answer;

second, he comes to a conclusion that throws some light on the question, at therefore it appears (423a6; [527]).

Note, in the first place, that it might appear that flesh was the organ of sensation in touch, because we feel tangible things on the instant of contact with our flesh.

526. But, setting this argument aside, he remarks that to decide whether the organ of touch be interior or not (in the latter case, the flesh would be the immediate organ of touch), it does not seem to be a sufficient sign that, when the flesh is touched, immediately there occurs a tactile sensation, that is, that the tangible is sensed. Because if one were to stretch a covering over the flesh or a delicate web, the tangible would be felt immediately on contact with it; yet it is obvious that the organ of touch would not be in that superposed skin. And again, if this superposed skin could become a part of one’s nature, one would feel even sooner through it. Hence, though at the touch of natural flesh the tangible is felt at once, still it does not follow that the flesh is the organ of touch, but only that it is a connatural medium for it.

527. Next, at therefore, it appears (423a6), he comes to a conclusion that throws light on the first question, saying that, flesh being a medium adapted to the sense of touch, it appears that this part of the body has the same sort of relation to sensation as the air would have if it formed a natural covering that grew all round our bodies. For though this air is but the medium of sight, smell, and hearing, it would appear in that case to be the organ of these senses; and thus, it would appear that we sensed sound and odor and color through a single organ and with a single organ. But in fact, just because the medium through which the motions of these sensible objects is determinate, that is, distinct from ourselves, we see clearly that it is not an organ. Moreover, there are obviously diverse organs for the three senses aforesaid and therefore a clear distinction of three senses. But it is not so clear in the case of touch; for here, the medium is a connatural part of us.

528. And he gives a reason for this difference. Air and water, the media of the other senses, could not be a connatural part of us, for it is impossible that an ensouled body be constituted from pure air or pure water. For these substances, being watery and fluid, are not solid or bounded by themselves; they need to be bounded by other things, whereas a living body must be solid and self-contained. Hence, the latter needs to be a mixture of earth and air and water, as it requires, that is, as flesh requires in animals that have flesh, and correspondingly, for those that have it not. So, this body that is the medium in touch, that is, flesh, is able to be naturally joined or united with touch in such a way that many sensations of touch come about.

529. Then, at that they are several (423a17), he states another fact in support of this. In the tongue also, he says, are several kinds of touch; for by it we feel all the objects of touch that are felt in other parts of the body, and we feel, besides, the flavor or savor that is not sensed in other parts of the body. If every part of the flesh sensed savors, we should not discriminate between taste and touch, just as we do not in fact discriminate between the touch that discerns hot and cold and that which discerns wet and dry. But now it is quite clear that touch and taste are two senses, because they cannot be substituted for the other: taste does not occur in every part where touch can occur. And the reason why taste is not to be found wherever there is touch is that savors are not qualities of those elements which constitute the bodies of animals; hence, they do not, like tangible qualities, pertain to what constitutes the animal.