LECTIO SEVENTEEN

             § 847. After taking the various parts of the soul in turn, and discussing each one separately, the Philosopher now shows how they are interrelated: explaining, first, that the vegetative part is common to all animate beings, and then, at 'Sensation is not necessarily found', that the sphere of sensitivity is more limited.

             In the light, then, of his previous conclusions he observes, first, that all beings that participate in any way in soul must, from the first moment of their generation until their final corruption, have some share in the vegetative principle; indicating by these terms that he speaks especially of animate beings which come to being through generation and cease through corruption.

             § 848. And he proves the point thus. No animate and generated being can exist without passing through the stages of growth, maturity and decline. And these all presuppose food. Growth implies that more food is being absorbed by a subject than is needed to maintain its existing bulk. Maturity implies a balance of food and bulk; whilst in decline less food is being absorbed than suffices to maintain the subject's bulk. And as it pertains to the vegetative principle to make use of food, this principle must be common to everything that is born and that dies; and must be related to the other parts of soul as the foundation they all presuppose.

             § 849. Then, at 'Sensation etc.', he shows how sensitivity is related to living things: and first, that it is not found in all of them; secondly, at 'But if Nature'. . ., where it is found. First, then, he remarks that touch (the sense presupposed by all the other senses, and therefore by all animal life as such) need not exist wherever life exists. The organ of touch requires (as we have seen) a sort of balance of contrary qualities; hence it cannot exist in simple bodies, which are characterised by the predominance of some one particular sensible quality--as heat in fire or cold in water.

             § 850. Similarly, whatever is unable to receive into itself forms free from matter cannot sense; for this way of receiving forms is, as we have seen, essential to sensitivity. Now plants, because in them the earthy element predominates, so that they are near neighbours to the simple bodies, are unable to receive forms from outside, except with a material alteration. Not all living things, therefore, are sensitive.

             § 851. Then, at 'But if Nature', he shows that all animals are sensitive. He does this (1) with regard to animals that can move from place to place; and (2) with regard to all animals without exception, at 'But having sensation'. As regards (1) he first proves his point; and then, at 'But a body . . .' refutes a possible objection. To prove that all animals are sensitive he assumes as a principle that Nature does nothing in a purposeless way. Everything in Nature has a reason, exists to supply the needs of purposeful being. Thus in order that certain activities may be carried out, things have a natural equipment of suitable organs. These organs, it is true, being composed in this or that way, have certain accidental qualities or adjuncts, e.g. hairs or colours, not to mention innate weaknesses, which are due rather to the matter of which they are composed than to the ends which they subserve. But since Nature always does act for an end, whatever natural thing simply could not reach a natural end would be quite out of place in Nature.

             § 852. Now Nature has adapted the bodies of mobile animals for movement; and they move for the sake of obtaining the food which keeps them alive. And to this end they require sense-awareness; otherwise they would not perceive the noxious things to which their movement sometimes brings them, and thus they would die and the very purpose of their movements would be frustrated. For they move about in order to get food, and could not get it otherwise.

             § 853. (The case of immobile animals is not relevant here, for the food they naturally require is joined to their substance; they do not have to seek it at a distance.) Clearly then, if mobile animal bodies lacked sense-awareness they could not reach the end for which Nature designs them. They would be futile; which is an unacceptable conclusion.

             § 854. Next, at 'But a body etc.', he removes a possible objection. It might be suggested that some moving animal bodies could reach their natural end through an intellectual awareness of things that would do them harm, even though they lacked sense-awareness. But Aristotle rejects this hypothesis with respect to mobile animals, whether these come into existence by generation or no. The point has been proved with regard to generated animals; for the only animate things that come into being by generation and are endowed with intellect are human beings, and the human mind presupposes sensation, as we have seen.

             § 855. But his rejection of the suggestion that intellect might exist without sensitivity in non-generated living things may seem at variance with Aristotle's own opinion. For it was his view that the heavenly bodies are both animate and intelligent, and yet lack sensitivity because their bodies are not organised into the distinct parts which alone make sensation possible. Hence some commentators make the sentence end at 'yet not have sensation'; and its meaning they take to be that no mobile body can be intelligent, lacking sensitivity, provided that it is a generated body. And what follows--'nor indeed etc.'--they take as the beginning of a new sentence, meaning that the case of non-generated bodies is different.

             § 856. Hence, according to their view, what follows, namely 'Why should they not etc.', must not be understood as an interrogation, but as a relative clause inserted to explain why non-generated bodies, i.e. the heavenly bodies, lack a sense-apparatus even while they have intelligence: Aristotle's argument (they say) being that neither the body nor the soul of a heavenly body would get any benefit from its having senses;--not the soul, because it would not understand any better thereby, since its understanding, like that of spiritual substances, bears upon the purely intelligible; nor yet the body, because, being essentially incorruptible anyhow, its senses would play no part in maintaining its existence.

             However, this interpretation hardly squares with the conclusion which follows, namely that no animate body which has the power to move from place to place lacks sensitivity (unless we choose to relate this conclusion to the previous statement; not to the immediately preceding one).

             § 857. Since, then, this seems a forced interpretation, it is better to understand by 'non-generated body', not any heavenly body, but the bodies of certain airy animate beings called by the Platonists demons. Apuleius, for instance, defined them as airbodied animate beings, rational, passive, eternal. And it would be concerning these beings, then, that the Philosopher seeks to prove that the Platonists were wrong in allowing them intelligence without senses. So the 'Why should they not' ought to be taken interrogatively, as meaning 'why should such bodies as these lack senses?' For, if they do lack them, this must be for the good either of their soul or their body; and neither reason is valid; for without senses their souls would understand no better, nor would their bodies be any the less corruptible. And the conclusion immediately follows, as given above, namely that no living bodies that are able to move about in space lack sensation. That this is indeed Aristotle's meaning appears from his immediately adding that no simple body can possibly be the body of an animal.

             § 858. Then at 'But having' he proves the absolute necessity, for all animals, of sensitivity; first proving the point, then at 'It is then evident', drawing a conclusion. The proof subdivides. Thus: (1) he puts forward his own view; (2) he proves it, at 'Which is evident from these considerations'. His own view contains two points, of which the first is that whatever body has sensation must be either simple or mixed. But it cannot be simple; for if it were it would lack the sense of touch; which he has already shown to be necessary for all animals, not only the mobile but also the immobile.

             § 859. Then, at 'Which is evident', he proceeds to show (1) that touch is found in all animals; (2) at 'It is clearly impossible', that no animal body can be a simple body. With regard to (1) he first shows the necessity of touch for all animals; and then, at 'The others exist', that the other senses are not found in all. As to this necessity, however, having shown it in the case of touch, he then, at 'This is why taste' proves that it belongs also to taste.

             First, then, he observes that the necessary universality of touch in the animal world can be clearly shown. For every animal is a living body; and every body is tangible or sensible to touch. By 'body' is here meant exclusively the generable and corruptible sort of body, not the non-generated, incorruptible heavenly bodies. These latter are not tangible; being outside the sphere of the elements they lack the elemental qualities which alone are tangible. But all corruptible bodies, being either simple elements or compounds of elements, are necessarily tangible.

             § 860. Whence he concludes to the necessity, for the preservation of the bodies of animals, that they be endowed with touch. For they are tangible, i.e. made up of tangible qualities; and so are the other bodies which actually touch them; and in the course of nature the animal's body might well be so affected by these latter bodies as to be destroyed by them. It is not the same with those senses whose medium of contact with their objects is not by touch, i.e. smell, sight and hearing; for their objects, being at a distance, do not actually touch the animal's body; they cannot therefore be a danger to its life, as tangible objects may be. Hence, unless the animal were able to touch, and touching to discriminate between, objects harmful and congenial to it, it could not avoid the former and accept the latter, and so preserve its existence. Touch, then, is a necessity for animals.

             § 861. Then, at 'This is why taste', he shows that the same is true of taste. For taste is a kind of touch, discriminating, as it does, between the goodness or harmfulness of different foods. Now food is essentially tangible and bodily; it nourishes the body just because it has the bodily qualities of being hot, moist, cold, dry. Bodies are nourished by bodies,--not by sounds or colours or scents; for sounds, colours and scents have nothing to do with growth or decay. Savour, however, is connected with nourishment by way of the body's natural disposition. Since then taste perceives food, and food is something tangible in the vegetative or nutritive order, taste is a kind of touch. Both these senses then are necessary; from which it is all the more evident that animals could not exist without touch.

             § 862. Next, at 'The others exist', he explains why the other senses are not found in all animals, but only in some; after which, at 'It is as when', he explains one of his own expressions. First, then, he observes that the other senses, sight, hearing and smell, are required for the well-being of certain animals, but not for their bare existence. Yet for some animals (not all), these senses are absolutely necessary--for those, namely that can move from place to place; for these need to be able to perceive objects at a distance as well as what immediately touches them. Now to sense things at a distance is only possible though a medium; the medium being affected and altered by the object, and the sense by the medium.

             § 863. And at 'It is as when' he proceeds to show this by a simile from local motion. Anything moving from place to place will cause a succession of changes which terminate at its destination; for what is first propelled forward is itself the cause of something else being propelled; so that the first agent disturbs a third thing through a medium--the first thing being a disturber itself undisturbed; the last, where the movement terminates, being disturbed but not itself a disturber; whilst the medium is both disturber and disturbed; and there may be many such media. And this order in local motion is observable also in changes by alteration: where there is a primary agent of change, a final recipient of change, and a medium both changing and changed.

             § 864. But with this difference, that, in the case of alteration, the agent of change is not moving from place to place as it changes, unlike the agent of propulsion. And he gives an example. If you touch soft wax it will be moved just so far as the warmth that accompanies your action makes the wax move. The hardness of stone would make it impervious to this kind of action; but water would be affected in this way, and still more air which is extremely mobile and has the maximum mobility at a distance from the moving agent. Air especially, then, is able to move and be moved as a medium, provided of course that it be continuous, i.e. not interrupted by any obstacle. With regard then to the impact of an object upon the senses, it is reasonable to hold (against the Platonists who said that sight emitted rays which the visible object reflected) that the intervening air is affected by the shape and colour of an object all the way between this object and the eye; provided of course that the air be uniform and continuous and smooth. Air, on this view, itself affected by shape and colour, affects sight; so that it is the visible object which modifies all the air between itself and the eye. It is as though the shape of a seal were to modify a piece of wax right through from one side to the other.

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