Lecture 7 — The vegetative principle: three senses of the soul’s causality

Whence we must first speak of food and generation. For the vegetative soul is present in others and is first; and it is the most common power of the soul, by which life is present in all of them. Its activities are reproduction and the use of food.

For the most natural of the works of living beings, whatever ones are complete and not defective or spontaneously generated, is to produce others like themselves: an animal an animal, and a plant a plant. To this extent they participate, as far as they are able, in being always, and the immortal, and the divine. For all things seek this, doing whatever things they do by nature for the sake of this.

Now, that for the sake of which anything takes place is twofold: one, the end of which; the other, the end by which.

Since, then, they cannot share by a continuous being in the divine and everlasting (since nothing corruptible remains forever numerically one and the same), each shares in this as far as it is able to participate in it, but one does so more, and another less. And thus it endures, not the same, but as the same; one indeed but in species, not numerically.

The soul is the cause and principle of the living body. Now, these words can be used in many ways. The soul, however, is a cause in three established modes: for the soul is that whence comes movement; that for the sake of which; and as the substance of ensouled bodies.

That it is as the substance, then, is evident. For in all things, the substance is the cause of existence itself. In things that live, however, to live is to be, and the cause and principle of these things is the soul.

Further, of that which is in potency, the act is the account.

It is manifest, however, that the soul is also a cause for the sake of which. For nature operates for a purpose, in the same way as intellect; and this is its end. Such is the soul in living things as well according to nature. For all natural bodies are instruments of the soul, whether of animals or of plants; they exist as for the sake of the soul. But “for the sake of which” is a phrase used in two ways, as “that of which,” and “that by which.”

But the soul is also the principle whence comes local motion. Yet this power is not present in all living things. Both alteration and growth are, however, due to a soul, while sensation seems to be a certain alteration, but nothing senses unless it has a soul. The same holds good of growth and decrease, for nothing undergoes growth or decrease naturally unless it is nourished, and nothing is nourished which does not share in life.

309. Whence we must first speak of food (415a22). Having distinguished the powers of soul from one another and explained how and in what order he means to discuss them, the Philosopher now treats of them in the order indicated. This he does in two stages.

In the first stage, he examines what each of them is, treating them one by one;

Then, in the second stage, at all things that live and have soul (434a22; [847]), he explains why they stand in this order. (Bk. 3, lect. 11–12.)

The former section divides into four parts:

first, he treats the vegetative part;

second, starting at these questions being settled (416b32; [350]), the sensitive part;

third, at as to the part of the soul by which it knows (429a10; [671]), the intellectual;

fourth, at we must now contemplate (432a18; [795]), local movement.

To the appetitive part is assigned no special treatise, because it does not of itself constitute any special grade of life, and because it will be treated together with motion. (Bk. 3, lect. 8–10.)

The first treatise divides into two parts:

the first part contains certain preliminaries to the study of the vegetative part;

the second, beginning at since the vegetative and generative (416a18; [333]), contains Aristotle’s conclusions on this matter.

The former section again divides into two:

in the first, he states his intention;

and in the second, at for the most natural (415a25), he gives an exposition of certain things which an understanding of the vegetative principle presupposes.

310. First of all, then, he remarks that if, as we saw in the last chapter, objects and acts have to be defined before potencies, and the first potency ought to be defined before those which follow from it, we ought in consequence to begin by discussing food (415a22), the object with which the vegetative soul deals, and generation, which is this soul’s activity. (Lect. 6, n. 308.) Now, we should speak about the object and act of this part before the others because this part is the first among the parts of the soul in the subjects wherein it is found along with the others, for it is, as it were, the foundation of the others, just as natural existence, toward which its activities pertain, is the foundation of sensible and intelligible existence. Besides, this part of soul is common to all living things (for it is separated from the others, whereas the others cannot exist without it), and one should treat the common first. Its works, then, being reproduction and taking in nourishment, it is with these that we begin.

311. Next, when he says, for the most natural (415a25), he settles a few preliminary questions for understanding the vegetative part; and this is divided into two stages.

In the first part, he shows that to generate one’s kind pertains to the vegetative part. It is necessary to show this because he had not yet done so, having spoken so far only of growth and decrease.

In the second part, at the soul is the cause (415b7), he proves that a soul is the principle of all vegetative activities. It is necessary to show this, for although the active and passive qualities serve these activities, it could seem to someone that they come from mere nature, and not from a soul—especially since life in plants is hard to discern and is hidden.

312. The first point is proved thus. All activities found to be natural to all living things pertain, as we have seen, to the vegetative power as the first and most common power of the soul, by which life is present in all of them (415a22); and reproduction is naturally present in all living things, so it pertains to the vegetative power. (Lect. 5, n. 288.)

Indeed, he says reproduction is the work of the vegetative soul because, as he says, among all works it is quite natural to all living things; and he says it is most natural (415a25) because in this it in a certain way fits with other things that have no soul but do have generation, albeit in a different way; for non-souled things have generation due to some exterior generator, whereas living things are generated due to an interior principle, insofar as they are generated by a seed that progresses into a living thing.

313. There are, however, three exceptions to the general rule that living things reproduce their kind.

First, the incomplete; for children do not beget (for what is able to make another that is such as it is itself is complete in each genus).

Second, those defective in some natural principle, such as the impotent and eunuchs.

Third, the animals and plants that are generated without seed from putrefying matter.

For in these, on account of their incompletion, a universal agent is enough for their production, that is, the power of the heavenly bodies and disposed matter. But in complete animals, more principles are required, for the universal agent is not sufficient; rather, a proper univocal agent is required.

314. Hence he says that living things can produce others like themselves, namely, whatever is complete (excluding children) and not defective (excluding eunuchs and such like) and whatever is not spontaneously generated (excluding things produced by putrefaction, which are said to come to be born, as it were, “spontaneously” because they spring up without seed, like the way someone is said to do spontaneously what he is not induced to do from something exterior to him).

And what he means by living things producing their like is that animals produce animals, and a plant a plant; and more precisely that each species produces its like, men producing men, and olive-trees, olive-trees.

And the reason why living beings produce their like is that they may continuously participate, as far as they are able, in the imperishable and the divine, that is, that they may become as like to the divine as possible.

315. For just as there are degrees of perfection in one and the same thing, inasmuch as it develops from potency into act, so there are more and less degrees of perfection in diverse beings; and therefore, the more perfect a given thing is, the more does it resemble the more perfect beings. Hence, while a thing is moving from potency to actuality, and as long as it is still in potency, it is ordered to the act and naturally has an appetite for it, and when it attains incomplete actuality, it still desires a more complete actuality; so in the same way, everything in a lower degree of reality desires to become as like as it can to the higher degrees. Hence he adds that all things seek this, that is, an assimilation to what is divine and imperishable, naturally doing whatever things they do for the sake of this.

316. But that for the sake of which something is done can mean two things:

in one way, the end for which one directly acts, as the doctor acts for the sake of health;

and in the other way, as the end by which; and this again may be taken in two ways.

For we might take the end to include also that subject in possession of that for the sake of which he acts, as when we say the end of medicine is not only health, but a body in possession of health.

Alternately, we could mean by end not only what is principally intended but also that by which the end is attained; we might say, for example, that the end of medicine is to keep the body warm, because warmth preserves that harmony of elements in the body which is health.

So then, when it is said here that perpetuity of existence is that for the sake of which the activity occurs, we are referring either to something imperishable that natural things strive to resemble by generation, or even to the generation itself by which they attain this perpetuity.

317. Because, then, the lower forms of life are unable to share in the divine and everlasting by way of continuity, that is, such that they would remain numerically the same—since nothing corruptible remains numerically one and the same always, and because the necessity of corruption is an absolute necessity (insofar as it arises from the matter itself and not from the end)—it follows that each one can only share in it as far as it is able; the more lasting natures, more, the less lasting, less, and yet they always remain by way of reproduction; each remaining one and the same, not the same simply speaking, but as the same in the sense that one and the same species remains. Hence, he adds that it does not remain one thing numerically, which is to be the same thing simply speaking, but only in species; and this because each individual reproduces its like according to species.

318. Then, at the soul is the cause (415b7), he shows the connection between the activities attributed to the vegetative power and the soul. And he does two things here:

first, he shows the truth;

second, at Empedocles did not speak well (415b28; [324]), he points out an error.

The proof of the truth, again, has two parts.

First, he states his aim, asserting that the soul is the principle and cause of the living body (415b7); and since “principle” and “cause” are spoken of in many ways, he distinguishes three modes in which this proposition is to be taken.

Soul, he says, is cause of the living body, in one way, as the principle of its movements; in another way, as that for the sake of which, or end; and in a third way, as the substance, that is, the form, of ensouled bodies.

319. Second, at that it is (415b12), he proves his proposition; and first, with regard to soul being the cause of the living body as its form. Here he uses two arguments.

First, the cause of anything as its substance, that is, form, is the same as the cause of its being, for everything has actual existence through its form. Now, it is the soul that is the cause of being for living things, for they live through their soul, and living itself is their existing. Hence the soul causes the living body as its form.

320. Then he makes a second argument, at further (415b14). The actuality of anything is the account and form of the thing that is in potency. But the soul, as we have seen, is the living body’s actuality. (Lect. 1, n. 233; lect. 2, n. 241; lect. 3, n. 253; lect. 4, n. 271.) Therefore it is the form and account of the living body.

321. Next, at it is manifest (415b15), he shows that the soul is a final cause of living bodies. And that it is a cause as the end of living bodies he says at: for nature . . . like intellect, acts for the sake of an end, as was shown in Physics 2. (Aristotle, Physics 2.8–9, 198b34–199b33; cf. Aquinas, Commentary on Physics, bk. 2, lect. 13–14.) But the intellect, in things that occur through art, orders and arranges materials for the sake of a form. So also, then, does nature. If, then, the soul is the living body’s form, it must also be its end.

322. Moreover, the soul is the end not only of living bodies but also of all lower natural bodies. He proves this as follows. For we see that all natural bodies are, as it were, instruments of the soul—not only of animals’ souls but of plants’ souls as well. For we see men turn to their own purposes both animals and plants and non-souled things; and animals make use of plants and non-souled things; and plants of the non-souled things insofar as they take nourishment and support from them. But as each thing acts in the nature of things, so it is naturally apt to act; whence it seems that all non-souled bodies are instruments of ensouled things and exist for their sake, and the less complete ensouled things exist for the more complete. After this, he distinguishes “for the sake of which” into the two aspects which have already been explained.

323. Third, at but the soul is also (415b21), he shows that the soul is the principle of movement in the body as that whence the motion originates. He uses the following reasoning: the form of every natural body is a principle of that body’s proper movement—for example, the form of fire is the principle of fire’s movement. Now, certain movements are proper to living things, such as the local motion whereby animals move themselves about from place to place, though this, to be sure, is not found in all living things. Similarly, sensation is a certain alteration and it is found only in things that have a soul. So too with growth and decrease; these movements imply the use of food and nothing self-nourishes except what has a soul. The soul, then, is the principle of all these movements.