Commentary Aristotle Physics
Lecture 13. Nature acts for an end
Yet it is impossible that this should be the true view. For teeth and all other natural things either invariably or normally come about in a given way; but of not one of the results of fortune or chance is this true.
We do not ascribe to chance or mere coincidence the frequency of rain in winter, but frequent rain in summer we do; nor heat in the dog days, but only if we have it in winter.
If it is agreed, then, that things are either the result of coincidence or for an end, and that these cannot be the result of fortune or chance, it follows that they must be for an end; and that such things are all due to nature even the champions of the theory that is before us would agree.
Therefore, action for an end is present in things that come to be and are by nature.
Further, where a series has a completion, all the preceding steps are for the sake of that. Now, surely, as it is in intelligent action, so it is suitably adapted; and as suitably adapted, so it is in each action if nothing interferes.
Now, intelligent action is for the sake of an end; therefore, the nature of things also is so. Thus, if a house, for instance, had been a thing made by nature, it would have been made in the same way as it is now by art, and if things made by nature were made also by art, they would come to be in the same way as by nature. Each step in the series, then, is for the sake of the next.
Art sometimes completes what nature cannot bring to a finish and at other times imitates her. If, therefore, artificial products are for the sake of an end, so clearly also are natural products. The relation of the later to the earlier terms of the series is the same in both.
This is most obvious in the animals other than man: they make things neither by art nor after inquiry or deliberation. Therefore, people discuss whether it is by intelligence or by some other faculty that spiders, ants, and the like work.
By gradual advance in this direction, we come to see clearly that, in plants too, that is produced that is conducive to the end—leaves, for example, grow to provide shade for the fruit.
If, then, it is both by nature and for an end that the swallow makes its nest and the spider its web, and plants grow leaves for the sake of the fruit and send their roots down (not up) for the sake of nourishment, it is plain that this kind of cause is operative in things that come to be and are by nature.
And, since “nature” means two things, the matter and the form, of which the latter is the end, and since all the rest is for the sake of the end, the form must be the cause in the sense of “that for the sake of which.”
255. Having stated the opinion and argument of those who say that nature does not act for an end, he here disproves this position.
He does this first through proper arguments;
second, at “now, mistakes come to pass” (199a33; [261]), through arguments taken from those things from which the opponents tried to prove the contrary position.
256. Concerning the first point, he sets forth five arguments.
The first (198b34) is as follows. Everything that happens naturally happens either in every instance or in most instances. But nothing that happens by fortune or by that which is per se vain—that is, by chance—happens in every instance or in most instances.
For we do not say that it rains frequently in winter by fortune or by chance. But if it rains frequently in the dog days, we would say that this happens by chance. And in like manner, we do not say that it happens by chance that there is heat during the dog days, but only if this should happen during the winter.
From these two points, he argues as follows. Everything that happens does so either by chance or for the sake of an end. Now, those things that happen outside the intention of an end are said to happen by chance.
But it is impossible for those things that happen in every instance or in most instances to happen by chance. Therefore, those things that happen in every instance or in most instances happen for the sake of an end.
Now, whatever happens according to nature happens either in every instance or in most instances, as even they admitted. Therefore, whatever happens by nature happens for the sake of something.
257. He gives the second argument at “further, where a series” (199a8). He says that there is an end for all things. That which is prior and all of its consequences are done for the sake of the end. Having assumed this, he argues as follows. As something is done naturally, so is it disposed to be done. For suitably adapted means naturally. And this proposition is convertible, for as something is disposed to be done, so it is done. However, it is necessary to add the condition “unless it is impeded.” Therefore, let us agree that there is no impediment. Hence, as something is done naturally, so is it disposed to be done. But things that happen naturally are done so that they lead to an end. Therefore, they are disposed to be done in such a way that they are for the sake of an end. And thus nature seeks an end; that is, nature has a natural disposition for an end. Hence, it is clear that nature acts for the sake of an end.
He clarifies what he has said by an example. One proceeds from the prior to the posterior in the same way in both art and nature. Thus, if artificial things such as houses were made by nature, they would be made according to the order in which they now are made by art. Thus, the foundation would be constructed first, and afterward the walls would be erected, and finally the roof would be placed on top. For nature proceeds this way in the things that are rooted in the earth, like plants. Their roots, like a foundation, are fixed in the earth; the trunk, after the manner of a wall, is raised on high; and the branches are on top like a roof.
And, in like manner, if the things that are produced by nature were made by art, they would be made according to the way they are disposed to be produced by nature.
This is clear in regard to health, which happens to be produced by art and by nature. For as nature heals by heating and cooling, so also does art.
Hence, it is clear that, in nature, one thing is for the sake of another; that is, the prior is for the sake of the posterior. And the same is true of art.
258. He gives the third argument at “art sometimes completes” (199a15). He says that art makes certain things that nature cannot make, such as a house and things of this sort. However, in regard to those things that happen to be produced by art and by nature, art imitates nature, as is clear in regard to health, as was said above.
Hence, if things that are made according to art are for the sake of an end, it is clear that things that are made according to nature also are made for an end, since the prior and the posterior in each case are similarly related. However, one might say that this is not a different argument from the one already given, but complementary to it and a clarification of it.
259. He gives the fourth argument at “this is most obvious” (199a20). This argument is drawn from those things in nature that more obviously seem to act for the sake of something. He says that it is most clear that nature acts for the sake of something when we consider animals that act neither through art nor through inquiry or deliberation. It is manifest in their operations that they act for the sake of something. Because of this, some have wondered whether spiders and ants and animals of this sort act through intellect or through some other principle. But, because they always act in the same way, it is clear that they do not act by intellect, but by nature. For every swallow makes a nest in the same way, and every spider a web in the same way, which would not be the case if they acted by intellect and from art. For not every builder makes a house in the same way, because the artisan judges the form of the thing built and can vary it. If we proceed beyond animals to plants, it is apparent among them that some things have been made and are useful for an end, as the leaves are useful as a covering for the fruit. Hence, if these things are due to nature and not to art—namely, that the swallow makes a nest and the spider a web, and that the plants produce leaves for the sake of the fruit, and the roots of plants are not above, but below so that they might take nourishment from the earth—it is clear that a final cause is found in things that come to be and are by nature, that is, by nature acting for the sake of something.
260. He gives the fifth argument at and, since “nature” means (199a30). He says that “nature” is used in two ways: for the matter and for the form. The form is the end of generation, as was said above. And the account of an end is that other things come to be for the sake of it. Hence, it follows that to be and to come to be for the sake of something should be found in natural things.