Lecture 17 — Comparison of growth, to food. How diminution occurs.

'Quantum-in-general' does not come-to-be any more than 'animal' which is neither man nor any other of the specific forms of animal: what 'animal-in-general' is in coming-to-be, that 'quantum-in-general' is in growth. But what does come-to-be in growth is flesh or bone—or a hand or arm (i.e. the tissues of these organic parts).

Such things come-to-be, then, by the accession not of quantified-flesh but of a quantified-something.

Insofar as this acceding food is potentially the double result e.g. is potentially so-much-flesh—it produces growth: for it is bound to become actually both so-much and flesh. But in so far as it is potentially flesh only, it nourishes: for it is thus that 'nutrition' and 'growth' differ by their definition.

That is why a body's nutrition continues so long as it is kept alive (even when it is diminishing), though not its 'growth';

and why nutrition, though 'the same' as growth, is yet different from it in its actual being. For in so far as that which accedes is potentially 'so much-flesh' it tends to increase flesh: whereas, in so far as it is potentially 'flesh' only, it is nourishment.

The form of which we have spoken is a kind of power immersed in matter—a duct, as it were. If, then, a matter accedes—a matter, which is potentially a duct and also potentially possesses determinate quantity the ducts to which it accedes will become bigger. But if it is no longer able to act—if it has been weakened by the continued influx of matter, just as water, continually mixed in greater and greater quantity with wine, in the end makes the wine watery and converts it into water—then it will cause a diminution of the quantum; though still the form persists.

113. After comparing growth with generation, the Philosopher here compares growth with food.

First, he shows how that which grows is related to that which nourishes;

second, how growth is related to nourishment, at and why nutrition (322a25; [117]).

With regard to the first he does three things:

First he shows what is the nature of that which is increased, namely, that it is something quantified. And he says (322a16) that there is not generated or produced a universal quantum, any more than a universal animal or a universal man or any of the singulars, i.e., any of the singular species—for example, neither a universal lion, nor a universal ox. But just as the universal is generated in these, namely, in some individual—for example, when this animal or this man is generated—so too here, i.e., in growth, a quantum is generated, not in the universal, but in something determinate, as when there is produced a certain quantity of flesh or bone or hand, and similar things.

114. Second, at such things come-to-be (322a19), he shows what that is which causes increase—for increase comes about by the accession of something, as was said above. But if by growth there were produced quantity in a universal way, the acceding thing would have had to have been quantified in potency and in no way in act. But because there is not generated quantity in a universal way, but this quantified thing—for example, flesh—the acceding thing has to be something quantified in act, but not, however, quantified flesh, except potentially.

115. Third, at insofar as this acceding food (322a20), he concludes to the difference between that which increases and that which nourishes.

First he sets down the difference and says that in so far as the acceding thing is in potency to both—for example, to being a quantity of flesh, so that it is not only capable of receiving the species of flesh, but also of being extended to a greater quantity—in this respect it increases. For in order for growth to take place, there must be produced both quantity (so as, namely, to produce a greater quantity), and flesh (since the acceding thing must become "like" at the end, as was said above.) But in so far as the acceding thing is in potency only to become flesh, in this respect it nourishes. Thus do food and growth differ according to notion: for food nourishes in so far as it is converted into flesh, but in so far as it takes on a greater quantity, i.e., produces it in the thing nourished, it increases.

116. Second, at that is why a body's nutrition (322a24), he states a certain corollary flowing from what has been said, namely, that a thing is nourished so long as it is preserved, i.e., so long as it is kept alive. For it is always necessary to restore by nourishment that which is continuously lost—that is, that which diminishes has to be nourished. But an animal is not always growing, but only so long as the food converted into flesh can be extended into a greater quantity.

117. Then, at and why nutrition (322a25), he shows the difference between growth and nourishment. And he says that nourishment is the same thing as growth, but they differ in being—as if to say: they are the same as to subject but differ in notion. For in so far as the acceding thing is in potency to both, i.e., to quantity and to flesh, in this respect there is growth of flesh; but in so far as it is in potency only to flesh, it is nourishment or food, as was explained above.

118. Then, at the form of which (322a28), he shows how diminution occurs. And the better to understand what is said here, we should reflect that the power of the species is otherwise in living things which are properly nourished and grow, and in things without life which are neither nourished nor grow. For living bodies move themselves not only with respect to local motion but also with respect to the motion of alteration, as when an animal is naturally healed, and with respect to the motions of growth and generation, especially in the sense in which nourishment is a certain generation, as was said above, in so far, namely, as, although flesh is not generated in itself, it is generated into the already existing flesh.

Now whatever moves itself is, as was proved in Physics VIII, divided into two: one of which is the mover, and the other is moved. Consequently, it is necessary that in a living thing there be something moved, namely, whatever is converted into the nature of the species; and something moving, namely, the power of the species, which does the converting. This explains why the virtue of the species in living things does not appropriate to itself some certain signate matter, since one part flows out and another arrives, as was said above. Yet the virtue of the species cannot be without any matter, but indeterminately in this or that, since, as was proved in Metaphysics VII, the virtue of the thing that generates is a form existing in this flesh and in these bones.

Now, in non-living things no such condition is found except perhaps in so far as there is in them some likeness of growth and nourishment, as, for example, in fire and in wine because of the efficacy of their active power. Consequently, the virtue of the species in flesh or in anything similar, in so far as it does not designate for itself any signate matter, but is now preserved in this, now in that, is as a certain immaterial species.

This, therefore, is what the Philosopher here shows, namely, that this, i.e., the virtue of the species of flesh, is a species without matter, as though it were a certain immaterial potency in the respect that it does not determine for itself signate matter. Yet it is always in some matter.

What has been said applies also to every other organ, such as bone or sinew and anything similar. Consequently, if there should accede some matter which is in potency not only to this species which is in a sense immaterial, but also to greater quantity, then there will be greater immaterialities, i.e., the virtues of the species that exist in flesh and bone and so on are extended to a greater quantity.

But this cannot always occur: for the virtue of the species becomes weakened (since it is present in a matter subject to contrariety), by continually acting and being acted upon, and by the accession of extraneous matter which does not receive the virtue of the species as perfectly as before. Consequently, when the virtue of the species cannot do this any longer, i.e., convert, of the food which is in potency, not only not as much as is required for the species and a greater quantity, but not even so much as is required for an equal quantity, then diminution of quantity occurs, although the virtue of the species is still preserved in the smaller quantity. But at last even the species ceases, just as, if more and more water should be mixed with wine, it will become watered wine, and then finally the wine will be corrupted, and there will be wholly water.

Here ends the exposition of Thomas Aquinas