LECTIO NINE

             § 333. After showing that the activities called vegetative originate in the soul, the Philosopher proceeds to examine these activities. And first he examines their subject-matter, which is food. Next he shows how the activities and their subject-matter correspond--this at 'Since only what is alive'. Thirdly, at 'Wherefore this soul-principle', he defines the faculties brought into play in these activities. As regards the first point he does three things: (a) he states the plan of the present argument; (b) at 'It would appear that food', he says what at first sight appears true about nutrition; to which (c) at 'But a difficulty', he brings an objection.

             In the first place, then, (a) he observes that, as the vegetative and reproductive powers are included in the same general vegetative power ('vegetative' as a special power being really the nutritive power), we should discuss food first of all in relation to this power as a whole. For it is taking food that characterises this part of the soul as distinct from the intellectual or sensitive parts. For the other vegetative activities all presuppose taking food.

             § 334. Then (b) he states in three points what appears at first sight with regard to nourishment. First, food would always seem to be the contrary of the subject fed; and this because it has to become the latter, and becoming is from one thing to its contrary. Secondly, however, it seems to be clear that not any contraries will do; they must be such as can change into one another. Food is changed into the being of the one fed; hence all contraries which alternate in a subject without the one ever actually changing into the other have nothing to do with food. Thus sickness is not the food of health, nor white of black. But how substances come to contain contraries is another question.

             § 335. (c) Again, since increase of bulk seems to follow nutrition, the contraries involved must be such as affect each other in this way. Water may be generated by fire and e converso, but we do not say that water is fed by fire. Yet we can say that fire is fed by water, inasmuch as watery vapour nourishes fire. When water comes from fire there is no new coming-to-be of water; but fire can make use of and grow by means of watery vapours. Among the elements, therefore, only fire seems to be fed and only water seems to be food, taking water to include all vapours and liquids.

             § 336. Then at 'But a difficulty' Aristotle brings an objection against what he has just said. The difficulty concerns the statement that food is a 'contrary'. For some maintain that food should resemble the subject fed. Food causes growth, and a thing grows by what it resembles; otherwise the growth would be a mere addition of something extrinsic. Therefore like, it seems, is fed by like.

             § 337. To others, however, it seems that food must, as we have said, be contrary to what is fed. And they are moved by two reasons. (a) Food, being cooked, is transformed into the subject fed. But all transformation is either into a contrary or into an intermediate, as white into either black or grey. And the intermediate is a sort of contrary: grey compared with white, is black; and compared with black, is white; for it combines both. Therefore food is contrary to the subject into which it is transformed.

             § 338. (b) Again, every agent is contrary to that on which it acts; like is not passive to like. But food is passive to what is fed: it is transformed and digested. What is fed is not passive to its food, any more than an artist to his material (for it is the material that is altered, not the artist, except indirectly, in so far as he moves from potency to act). It would seem, then, that food is contrary to what is fed. Now the first of these two reasons is drawn from the contrariety between the two terms of a change; and the second from the contrariety between agent and patient. That which is fed, and itself acts upon the food, is the term into which the food is transformed.

             § 339. Then at 'It makes all the difference' he solves the problem, saying that the answer depends on whether by 'food' we mean what remains at the end of the process of heating and digesting, or what is received at first before this process begins. If food can be taken in both these senses--namely as the finished and as the raw product--then the two answers are both admissible. If it is taken in the latter sense, then subjects are fed by their contrary, which itself is acted upon and transformed; but if in the former sense, then like is fed by like; for the active agent assimilates what it acts upon, which is ultimately made like the agent and, as such, can increase the agent's bulk. Thus both the above opinions were in one way true and another way false.

             § 340. Next, at 'Since only', he shows how food is related to the activities of the vegetative principle: to taking nourishment; to growth (at 'To be nutritive'); and to reproduction (at 'And it is productive').

             First, then, he observes that nothing is fed except what has life and soul; hence the besouled body is what is fed. Now food is potential with respect to the subject fed; for it is changed into this subject. It follows that, inasmuch as food is the material of feeding, it is essentially, not accidentally, related to the besouled body as in potency to this body.

             § 341. Nothing then is, properly speaking, fed excepting what has a soul. Fire might seem to resemble in some way things that are fed, but it is not fed, strictly speaking. For that is properly said to be fed which absorbs something else in order to maintain its own being; and though this appears to happen with fire, it does not really happen. Once a fire has started, if you add fresh fuel, a new fire starts in the new fuel; but not in such a way that the new fuel maintains the fire already started before it was added. By starting a fire in fresh wood you do not maintain the flame in the other wood already burning. For the one flame made up of many flames is not one in the simple sense of the term; it is only one by the aggregation of many units, like a heap of stones. And it is this sort of unity that gives to burning a certain likeness to taking food.

             § 342. Living bodies, on the other hand, are really fed; food maintains life precisely where it already existed. This also is why only living bodies, properly speaking, grow; for each and every part in them is fed and increases; whereas inanimate things increase only by addition of part to part; what existed already does not increase, it is merely made into a new whole together with some other thing added to it.

             But if fire has a special likeness to living and growing things, this is because the formal principle in fire is stronger than in the other elements, and its active power greater. It seems, therefore, to feed and grow because it so obviously seizes and subdues to itself other things.

             § 343. Then, at 'To be nutritive', he relates taking food to growth, observing that whilst the objective terms of feeding as feeding and of growing as growing are one and the same thing, they differ in idea. Food, we have seen, is in potency to the living body; which itself is both a quantum and a definite particular thing or substance. As a quantum it receives its food (which itself is a quantum) as a cause of growth; but as a particular sort of substance it receives food precisely as food. For it is of the nature of food to maintain the substance of what is fed; which is required by the continuous using up of natural warmth and moisture. Hence the substance of the thing fed lasts just so long as it is fed.

             § 344. Then at 'And it is productive' he relates nutrition to generation, as the latter's cause. For seed, the generative principle, is the residue of food. And food is an agent in generating, not the subject fed, but other subjects of the same kind; for the subject fed already exists and cannot be generated afresh. Nothing generates itself; only what does not yet exist is generated. This is not to say, however, that things cannot maintain themselves.

             § 345. Next, at 'Wherefore, this soul-principle', he concludes with a definition of the powers of the vegetative soul: first, of the nutritive power, and then, at 'Since all things', of the whole vegetative principle. As to the nutritive power, he observes that it is simply that faculty by which a living being is able to maintain itself as such; while food is the condition of this faculty's activity, that by means of which it maintains its subject. Hence loss of being follows lack of food.

             § 346. And, having remarked that the source of nutritive activity is a capacity in the soul relating essentially to food, he goes on, at 'Since there are three' to show how that power and the food itself differ as sources of nutrition. Nutrition, he says, involves three factors: what is fed; that wherewith it is fed; and the primary agent in feeding: this primary agent is the primary, i.e. vegetative, soul. What is fed is its body; and that wherewith it is fed is food. Thus a capacity in the soul is the cause of taking food as the principal agent; but food as the instrumental agent.

             § 347. Next, at 'Since all things', he defines that primary or vegetative soul (the entire soul of plants, but only part of any animal's soul). To understand his definition, we must realise that the three vegetative activities fall into a certain order. First is taking food, by which things are maintained in being; the second and more perfect activity is growth, by which a thing increases in both quantity and capacity; while the third and most perfect and ultimate vegetative activity is reproduction, by which a being, already pretty complete in itself, gives existence and perfection to another being. For each thing is at its best, as is said in the Meteorologica, Book IV, when it can reproduce its likeness in another. If then all things are rightly defined and named in terms of their end, and the end of all the activities of the vegetative soul is to generate its likeness in another, it follows that we can suitably define this 'primary soul' as that which is reproductive of another, like to itself in kind.

             § 348. And in view of his previous remark that this primary soul's instrument was food, to prevent anyone thinking that it had no other instrument, he shows, at 'That by which', that the subject fed has another instrument wherewith it is fed; just as in steering a ship there are two instruments. For the pilot steers with both hand and rudder. Now the hand is a conjoined instrument which has the soul for its form. Whilst, then, the rudder is an instrument which moves the boat and itself is moved by the hand, the hand itself is not moved by an exterior motive force, but by an interior one; for it is a part of the man and the man moves himself. Similarly, the instrument of nutrition is twofold. There is the separated instrument not yet informed by the soul; and this is food. But there must also be a conjoined instrument; for the food must be digested; and this requires heat. As then a pilot moves the rudder with his hand, and the boat with the rudder, so the soul moves the food with heat and, by means of the food, nourishes itself. The heat is the soul's conjoined instrument; a natural warmth inseparably rooted in the soul and necessary to all living things as the condition of their digesting their food. And it is because this primary soul is, unlike the intellect, the actuality of a part of the body that it has a conjoined instrument.

             § 349. Summarising, Aristotle says that he has defined 'in outline', that is in general, what food is; later he will treat of it with more precision and finality. For he wrote a special book on food, as also on the generation and movement of animals.

416b 32-417a 21