Lecture 11 — Sensation and life: touch as fundamental sense

All things that live and have soul, therefore, must have the vegetative soul; and this, from generation to corruption. For everything generated must pass through the stages of growth, maturity, and decline; and this is impossible without food. Of necessity, then, a vegetative power is found in all that is born and dies.

Sensation, however, is not necessarily found in everything that lives. For things whose bodies are simple cannot even have touch, without which no animal can exist at all; nor can whatever is unable to receive species without matter.

But if nature does nothing in vain, all animals are sensitive. For all that exist by their nature subsist for the sake of something or accompany things that are for the sake of something. Therefore if every body that is able to move about lacked sensation, it would soon be destroyed and would never attain its end, which is the work of nature. For how would it be nourished? For animals that stay still indeed find nourishment in that out of which they are produced.

But a body that is generated, not stationary, cannot possess a soul and intellectual discernment and yet not have sensation; nor indeed can an ungenerated one. For why should it not have it? For the good of either the soul or the body. But neither, surely. For the one would not then understand better nor would the other benefit on account of it. No mobile body, then, has a soul without sensation.

But if it has sensation, the body must be either simple or mixed. It cannot, however, be simple; for then it would lack the sense of touch, and it must have this sense.

This is evident from these considerations. For an animal is an ensouled body, and every body is tangible, and the tangible is what is sensible to touch; therefore the animal’s body must be able to touch if the animal is to survive. For the other senses sense through an extraneous medium, e.g., smell, sight, hearing. But if it had no sense of touch, it could not avoid certain things and seize upon others; and thus, the animal could not preserve itself.

This is why even taste is as a certain touch; for it relates to food, and food is a tangible body. But sounds and colors and scents do not nourish or contribute to growth or decay. Taste must also, then, be a certain touch, being a sense of the tangible and the vegetative.

These senses then are necessary to the animal, so it is plain that no animal can exist without touch. The others, however, exist for the sake of some good; and then not in every genus of animal, but in some, namely, in those that need to move from place to place. For if such an animal is to survive it must sense not only what is in contact with it, but also what is afar.

And this will happen, if it senses through a medium, this being acted upon and moved by the sense-object, and the animal itself by it.

For just as a thing moving locally operates till it effects a change toward some destination, and, pushing something else, it makes the other push, and this is motion through the intermediate, such that the first mover pushes without being pushed, and the last is only pushed without pushing anything, while the intermediary is both (or the many intermediaries), so it is with the alteration in question, except that what causes the alteration remains in the same place.

For example, if one dips an object into wax, the wax moves to the extent that the object enters it; whereas a stone is not moved at all, but water a long way, and air most of all, giving and receiving motion, so long as it remains a unity. Hence, even as regards reflection, it is better to say that the air is acted upon by shape and color, so long as it retains unity, than to say that the sight proceeds out and is reflected back. On a smooth surface air has unity, and so in turn, moves the sight, as if a signet ring were to sink into and right through wax.

847. All things that live and have soul (434a22). After discussing the various parts of the soul in turn, the Philosopher now shows how they are ordered to each other:

first, he explains that the vegetative part is necessary to all animate beings;

second, at sensation, however, is not necessarily found (434a27; [849]), he shows that the sensitive is not in all, but only in animals.

In the light, then, of his previous conclusions about the parts of the soul, (Bk. 2, lect. 4 – bk. 3, lect. 10.) he observes, first, that all things that live, and consequently have any part in soul, must, from the first moment of their generation until their final corruption, have the vegetative soul; thereby he implies that he means the living things that are generated and corrupted.

848. And he proves the point thus. Everything living and generated must pass through the stages of growth, maturity, and decline. And these cannot happen without food. For the time of growth requires that more food is being absorbed by a subject than is needed to maintain its existing bulk; the time of maturity implies a state of balance; but the time of decline implies a state of less. Since, then, to make use of food pertains to the vegetative part, this part of the soul of necessity is in all living things that are generated and corrupted. And in this way the order of this part of the soul to the other parts of the soul is evident, for all the others presuppose it.

849. Then, at sensation, however, is not necessarily found (434a27), he shows how the sensitive part is related to living things:

and first, that it is not found in all of them;

second, at but if nature does nothing in vain, animals must have sensation (434a30; [851]), where it is found.

First, then, he remarks that it is not necessary that all living things have sensation, because the sense of touch, without which no other sense can exist (and consequently, neither can any animal, the very account of which is completed from the fact that it has sense, exist without touch), cannot exist in any simple body; for the sense-organ of touch requires (as we have seen) a sort of mean of contrary qualities; hence, it cannot exist in simple bodies, that is, in the elements, which have an excellence of tangible qualities—as an excellence of heat in fire or of cold in water. (Bk. 2, lect. 22, nn. 521–24.)

850. Similarly, whatever is unable to receive species without matter cannot sense; for the sense is receptive of species without matter, as was said above. (Bk. 2, lect. 5, n. 284; lect. 24, n. 551; bk. 3, lect. 7, n. 792.) Now, there are some living things, that is, plants, that are near neighbors to the simple bodies because in them the earthy element predominates, and they do not receive the species of sensible things, except with a material modification. Not all living things, therefore, are sensitive.

851. Then, at but if nature (434a30), he shows that all animals have sensation. And regarding this, he does two things.

First, he shows this with regard to animals that can move from place to place;

second, with regard to all animals without exception, at but if it has sensation (434b8; [858]).

As regards the first, he does two things:

he first proves his point;

second, at but a body (434b3; [854]), he refutes a possible objection.

To prove that all animals are sensitive, he assumes as a principle that nature does nothing in vain, for all that exist in nature exist for the sake of something (since nature acts for an end) or accompany things that are for the sake of something, that is, they arise of necessity from those things that are for the sake of something; for example, nature makes organs for the sake of certain activities.

But from the fact that the organs are of a certain disposition it follows that they have certain accidents, for example, they have certain hairs or colors, or even corruptions that are not for the sake of an end but rather arise from a necessity of the matter. In this way, then, since nature acts for an end, if the natural things cannot reach the end that nature intends, it would be pointless.

852. But nature has made the body that is able to move about, that is, that of the animal that can move with a progressive movement, organized and disposed in such a way for the sake of the motion, and so that by that motion it might find food to preserve it in being. But this could not be if it did not have sensation, since then it would not discern the corruptive things that it could meet and thereby it would be destroyed and it would not reach the end that nature intends, that is, to preserve it through the food that it acquires from its motion. For how would they be nourished, if they could not seek food through movement?

853. Nor is the case of immobile animals, since these animals stay still (that is, that are immobile) a problem, for they are joined to nourishment in the substance from which they are produced; thus, they do not have to seek it at a distance. Clearly then, if mobile animal bodies lacked sensation, they could not reach the end for which nature has ordered them, and thus they would exist in vain, which is incongruous.

854. Next, at but a body (434b3), he removes a possible objection. It might be suggested that some moving bodies could reach the end intended by their nature by discerning corruptive things by means of their intellect, even if they lacked sensation. But he rejects this, saying that the body not having a stationary existence, but a progressive one, cannot possess a soul and intellectual discernment of harmful things in such a way that it would not have sense, whether it be generated or ungenerated. The point has been proved with regard to generated animals, for the only living things that come into being by generation and are endowed with intellect are human beings, and the human intellect needs sensation, as we have seen. (Lect. 6, n. 772; lect. 7, n. 791.)

855. But his rejection of the suggestion that intellect might exist without sense in non-generated living things seems false even according to Aristotle’s own opinion. For he asserts that the heavenly bodies are both ensouled and, among the parts of the soul, they have intellect but not sensation, since their bodies are uniform, without the distinction in organs that is required for sensation. Hence, some commentators make the sentence end at not have sensation; and its meaning they take to be that no mobile body can have intellect without sensation, provided that it is a generated body. And what follows—at nor indeed can an ungenerated—they take as the beginning of a new sentence, meaning that the case of a non-generated body is different from that of a generated body, namely, that it cannot have intellect without sensation.

856. Hence, according to their view, what follows, namely, for why should it not, must not be understood as a question, but as a relative clause inserted to explain why a non-generated body, that is, the heavenly body, does not have sensation even though it has understanding: the explanation being that if it were to have sensation, this would be either such that thereby there would be some benefit for the heavenly body’s soul or some benefit for the heavenly body itself, but neither of these is the case: the heavenly body’s soul would not understand any better on account of sensation than it does without sensation (for it understands through the mode of the separated substances, which are intelligible through themselves), nor could even the heavenly body be preserved in being better on account of sensation, since it is not possible that it corrupt, so it does not need senses to avoid things that might corrupt it.

However, this interpretation hardly squares with the conclusion which follows, namely, that no mobile body, that is, one that is not immobile, has a soul without sensation, unless we choose to relate this conclusion back to the previous statement and not to the immediately preceding one.

857. Since, then, this seems to be a forced interpretation, it is better to understand by “non-generated body” not any heavenly body, but the bodies of certain airy animate beings that the Platonists posited, calling them “demons.” Apuleius the Platonist, in fact, defined demons as “animals with airy bodies, rational in mind, passive in spirit, and temporally eternal.” And it would be concerning these beings, then, that the Philosopher seeks to prove that the Platonists were wrong in allowing them intellect without senses. So the “why should it not have” ought to be taken as a question, as meaning “why should such a body not have senses?” as if to say, “there is no reason to assert this.” For if it does lack them, this must be for the good either of its soul or its body; and neither of these is the case, for without senses its soul would understand no better, nor would its body be better preserved. And the conclusion immediately follows, as given above, namely, that no mobile body that has a soul lacks sensation. That this is indeed Aristotle’s meaning is apparent from his immediately adding that no simple body can possibly be the body of an animal.

858. Then, at but if it has sensation (434b8), he proves that sensation is simply necessary for all animals. And about this he does two things:

first, he proves the point;

second, at it is, then, evident (435b4; [869]), he draws a conclusion.

The proof subdivides.

First, he puts forward his own view;

second, he proves it, at this is evident from these considerations (434b11; [859]).

His own view contains two points, of which the first is that if some body has sensation, the body must be either simple or mixed. It cannot, however, be simple; for if the body were it would lack the sense of touch, which he has already shown that all animals must have, not only the progressively mobile animals but also the immobile animals. (Bk. 2, lect. 3, n. 260; lect. 4, n. 266; lect. 5, n. 288; lect. 6, n. 300; lect. 19, n. 484; lect. 27, n. 602.)

859. Then, at this is evident (434b11), he proceeds to show what he has proposed.

First, that touch is found in all animals;

second, at it is clearly impossible (435a11; [865]), that no animal body can be a simple body.

With regard to the first, he does two things.

First, he shows the necessity of touch for all animals;

second, at the others, however, exist (434b24; [862]), that the other senses are not found in all.

About the first of these, he does two things:

first, he shows that it is necessary for touch to be in all animals;

second, he shows this concerning taste, at this is why even taste (434b18; [861]).

First, then, he observes that this, the necessity that touch be in all animals, is evident from these considerations. For an animal is an ensouled body, and every body, that is, every generable and corruptible body*, is tangible, and* I call “tangible” what is sensible to touch. (But the heavenly bodies, which are ungenerable and incorruptible, are not tangible, for they are not of the nature of the elements, such that they could have the elemental qualities that are the tangible qualities; rather, all corruptible bodies necessarily have the tangible qualities, since they are either simple or compounds of elements.)

860. Whence he concludes that the animal’s body must have the sense of touch if the animal is to survive. For an animal’s body is tangible, that is, it has the tangible qualities, and so are the other bodies that touch it; therefore the animal’s body might well be affected by these things that touch it with a material change, even to the point of its corruption. It is not the same with those senses that sense through different media, and without touching, that is, smell, sight, and hearing; for their sense-objects, being at a distance and not touching the animal’s body, cannot alter it in the direction of corruption, as the tangible objects can. Hence, if the animal had no sense of touch to discriminate between fitting things and corruptive things, it could not avoid certain things and seize upon others; and thus the animal could not preserve itself. Having the sense of touch, then, is a necessity for an animal’s preservation.

861. Then, at this is why even taste (434b18), he shows that the same is true of taste, that is, that taste is as a certain touch, for taste is for food, that is, it is that whereby one discerns whether food is fitting or not; but food is a certain tangible body, for it nourishes the body just because it is hot, moist, cold, and dry. For we are nourished by the things from which we are composed. But sounds and colors and scents contribute nothing to nourishment, or to growth or decrease. Flavor, however, does contribute to nourishment insofar as it is a consequence of a thing’s constitution. In this way, then, it is clear that taste is a certain touch, since it is the sense of something tangible and the vegetative or nourishing, that is, of food. Both these senses then are necessary for animals; from which it is plain that no animal can exist without touch.

862. Next, at the others, however, exist (434b24), he explains why the other senses are not found in all animals, but only in some. And about this he does two things.

First, he shows it;

second, at for just as a thing (434b29; [863]), he explains one of his own expressions.

First, then, he observes that the other senses of sight, hearing, and smell, belong to an animal not out of necessity, but for well-being, and it is not necessary that they be in every genus of animal, but in some, that is, those that can move from place to place. For if such an animal is to survive, not only ought it sense what is in contact with it, but also what is afar, since it travels to food that is at a distance. And this, that is, sensing things at a distance, will happen if it has a sense that senses through a medium, this medium being acted upon and moved by the sense-object, and the sense by the medium.

863. And, at for just as a thing (434b29), he proceeds to show this through a likeness based on local motion. For we see that anything moving locally will cause a succession of changes till they reach a determinate place, for what first pushes a thing makes the latter push something else; thereby the first agent moves the third thing *through the intermediate—*and the first mover impels without being pushed, and the last, where the movement terminates, is pushed but does not itself push anything; while the intermediary holds both—it both pushes and is pushed, and there may be many intermediaries. And as this happens in local motion, so too it happens with alteration that there is a primary mover and a last thing moved and an intermediary that is mover and moved.

864. But there is this difference: in the case of alteration, what causes the alteration remains in place as it acts, unlike the agent of a push. And he gives an example. If you touch soft wax, the wax moves to the extent that, through the alteration of heat, the action of the one touching touches it. But a stone, because it is hard, is not receptive to such an impression, whereas water would be so altered, even a long way further than the wax, and still more air, which is even more capable of being acted on, would be moved most of all, by it giving and receiving motion as a medium, provided of course that it remains a unity, that is, not interrupted by any obstacle.

With regard then to reflection in sight, it is better to hold that the air is acted upon by shape and color, provided that the air retains unity and is continuous, which happens when it is smooth and uninterrupted, rather than to say that there are rays coming forth from one’s sight and reflected by the visible object, as the Platonists asserted. And therefore, air so moved by shape and color moves sight, insofar as the visible thing modifies all the air up to the eye. It is as though the shape of a signet ring were to be impressed on a piece of wax right through from one side to the other, just as the visible impresses its species on the air all the way to sight.