Commentary Aristotle Physics
Lecture 14. Opponents’ arguments show that nature acts for an end
Now, mistakes come to pass even in the operations of art: the grammarian makes a mistake in writing and the doctor pours out the wrong dose.
Hence, mistakes are clearly possible in the operations of nature also. If, then, there are cases in art in which what is rightly produced serves a purpose, and if where mistakes occur there was a purpose in what was attempted but not attained, so must it be also in natural products, and monstrosities will be failures in the purposive effort.
Thus, in the original combinations, the “ox-progeny,” if they failed to reach a determinate end, must have arisen through the corruption of some principle corresponding to what is now the seed.
Further, seed must have come into being first, and not straightway the animals: the words “whole-natured first” must have meant seed.
Again, in plants, too, we find the relation of means to end, though the degree of organization is less. Were there in plants, then, also “olive-headed vine-progeny,” like the “man-headed ox-progeny,” or not? It seems an absurd suggestion, but there must have been, if there were such things among animals.
Moreover, among the seeds, anything must have come to be at random.
But the person who asserts this entirely does away with “nature” and what exists “by nature.”
For those things are natural that arrive at some completion by a continuous motion originated from an internal principle: the same completion is not reached from every principle; nor any chance completion, but always the tendency in each is towards the same end, if there is no impediment.
The end and the means toward it may come about by chance.
We say, for instance, that a stranger has come by chance and gone away after he has bathed, when he does so as if he had come for that purpose, though it was not for that that he came. This is accidental, for chance is an accidental cause, as I remarked before. But, when an event takes place always or for the most part, it is not accidental or by chance. In natural products, the sequence is invariable, if there is no impediment.
It is absurd to suppose that purpose is not present because we do not observe the agent deliberating. Art does not deliberate. If the ship-building art were in the wood, it would produce the same results by nature. If, therefore, purpose is present in art, it is present also in nature. The best illustration is a doctor doctoring himself; nature is like that. It is plain, then, that nature is a cause, a cause that operates for a purpose.
261. After the Philosopher has shown by appropriate arguments that nature acts for the sake of something, he here intends to make this clear by destroying those things through which some embraced the contrary position.
This section is divided into three parts according to the three things by which some seem to be moved to deny that nature acts for an end.
The second part begins at “but the person” (199b14; [267]).
The third part begins at “it is absurd” (199b26; [268]).
262. The first thing by which some seem to be moved to deny that nature acts for an end is the following. Sometimes we see things happen otherwise than is customary, as happens in the case of monsters, which are the errors of nature. Hence, Empedocles held that, at the beginning of the constitution of things, certain things were produced that did not have this form and this order that is now commonly found in nature.
263. He brings forth four arguments to overcome this difficulty.
First (199a33), he shows that, although art acts for the sake of something, error still occurs in things that are made by art. For sometimes the grammarian does not write correctly or the doctor prescribes a drink as a medicinal potion incorrectly.
Hence, it is clear that error occurs also in things that are by nature, even though nature acts for the sake of something. Of the things that are made by art for the sake of something, some are made according to art and are made correctly.
There are other things, however, in which the artisan fails, not acting according to his art, and in these cases, error occurs, even though the art is acting for the sake of something.
For if art does not act for a determinate end, then there would be no error no matter how the art was performed. For the operation of the art would be equally related to all things. The very fact that there happens to be error in art, then, is a sign that art acts for the sake of something.
The same thing also happens in natural things, in which monsters are, as it were, the errors of nature acting for the sake of something insofar as the correct operation of nature is deficient. And this very fact that error occurs in natural things is a sign that nature acts for the sake of something. The same thing is true of those substances that Empedocles said were produced at the beginning of the world, such as the ox-progeny, half ox and half man.
For if such things were not able to arrive at some end and final state of nature such that they would be preserved in existence, this was not because nature did not intend this, but because they were not capable of being preserved.
For they were not generated according to nature, but by the corruption of some natural principle, as it now also happens that some monstrous offspring are generated because of the corruption of seed.
264. He gives the second argument at “further, seed must have” (199b7). The argument is as follows. Wherever there are determinate principles and a determinate order of proceeding, there must be a determinate end for the sake of which other things come to be. But in the generation of animals, there is a determinate order of proceeding. For it is necessary that seed come to be first, and there is no animal that exists immediately from the beginning. And the seed itself is not immediately hardened, but in the beginning, it is soft and tends toward perfection in a certain order. Therefore, there is a determinate end in the generation of animals. Therefore, monsters and errors do not occur in animals because of nature’s not acting for the sake of something.
265. He gives the third argument at “again, in plants” (199b9). The argument is as follows. Although nature acts for the sake of something in regard not only to animals but also to plants, the degree of organization is less, namely, it is less clear. Fewer things can be inferred from the operations of plants.
If, therefore, monsters and errors occur in animals because nature does not act for the sake of something, this should be even more true of plants. As the “man-faced ox-progeny” occurs in animals, does there also occur in plants an olive-headed vine-progeny, half olive and half vine? It seems absurd to say that these things occur. Nevertheless, this must be so if it is true in regard to animals that nature does not act for the sake of something. Therefore, in regard to animals it is not true that nature does not act for the sake of something.
266. He gives the fourth argument at “moreover, among the seeds” (199b13). The argument is as follows. As animals are generated by nature, so also are the seeds of animals.
Therefore, if what occurs in the generation of animals happens in any way whatsoever, and not by nature, as it were, acting for a determinate end, then the same would be true of seeds: any sort of seed would be produced by any sort of thing. This is obviously false. Hence, the first supposition is also false.
267. Next, at “but the person” (199b14), he destroys the second point by which some were moved to hold that nature does not act for the sake of something. This seemed true to some because things that happen naturally seem to proceed from the prior principles, which are the agent and the matter, and not from the intention for an end.
But Aristotle shows the contrary. He says that one who speaks in this manner—that is, one who says that nature does not act for the sake of something—destroys nature and the things that are according to nature. For those things are said to be according to nature that are moved continuously by some intrinsic principle until they arrive at some end—not to some contingent end, and not from any principle to any end, but from a determinate principle to a determinate end. For progress is always made from the same principle to the same end, unless something impedes it.
However, that for the sake of which something is done sometimes happens to occur by fortune, when it is not done for the sake of this.
For example, if some stranger should come and leave after he has bathed, we say this was by fortune. For he did not bathe himself as if he had come for this purpose, since he did not come for this.
Hence, his bathing is accidental, for fortune is a per accidens cause, as was said above. But, if this should happen always or in most instances to him who comes, it would not be said to be by fortune.
But, in natural things, events occur not per accidens, but always, unless something should impede. Hence, it is clear that the determinate end that follows in nature does not follow by chance, but from the intention of nature. And from this it is clear that it is contrary to the meaning of nature to say that nature does not act for the sake of something.