Teleology in Nature
Aristotle's conception of natural bodies is teleological.
He thinks that natural bodies have natures, that a nature is the organization of the material so that there exists a natural body that behaves in the ways characteristic of the natural kind, and that these behaviors are in the natural body for the sake of an end.
Anaxagoras and Socrates
"My glorious hope, my friend, was quickly snatched away from me. As I went on with my reading I saw that the man made no use of intelligence (νῷ), and did not assign any real causes (αἰτίας) for the ordering of things, but mentioned as causes air and ether and water and many other absurdities. And it seemed to me it was very much as if one should say that Socrates does with intelligence whatever he does, and then in trying to tell the causes of everything I do, to say that the reason that I am sitting here is because my body consists of bones and sinews, because the bones are hard and are separated by joints, that the sinews are such as to contract and relax, that they surround the bones along with flesh and skin which hold them together, .... He would mention other such causes for my talking to you: sounds and air and hearing, and a thousand other such things, but he would neglect to mention the true causes, that, after the Athenians decided it was better to condemn me, for this reason it seemed (δέδοκται) best to me to sit here and more right (δικαιότερον) to remain and endure whatever penalty they ordered" (Phaedo 98b-e; cf. Timaeus 46d). In the Phaedo, in his intellectual autobiography, Socrates says that when he was younger he hoped to learn from Anaxagoras but was disappointed. He says that Anaxagoras promised to explain things in terms of νοῦς ("intellect," "mind," or "reason") and thus to explain how things are for the best. In fact, according to Socrates, Anaxagoras omits νοῦς from his explanations.
Socrates provides an analogous explanation he thinks is clearly unacceptable. To explain why he sits in jail, he says that it is necessary to explain that he sits there (as opposed to having made his escape with Crito) because he decided that this course of action was best. Anaxagoras, according to Socrates, does not provide this kind of explanation. He would say that Socrates sits in jail because his bones and sinews are arranged in a certain way, but Socrates thinks this is no explanation at all because it omits Socrates and his reasons, and so fails to explain why he is sitting in jail.
The "For Something" is in Nature
Aristotle, in his teleological conception of nature, tries to provide the sort of explanations Socrates wants in the Phaedo. Aristotle thinks that something in nature is the behavior a natural body possesses because it belongs to a kind only if the behavior the body undergoes is for the sake of an end. If it is not for the sake of an end, it is behavior that happens by coincidence.
An example helps to clarify Aristotle's view. Consider the chemical reactions that happen in digestion. These reactions could happen in glassware in a laboratory, but this would not be an instance of digestion. Digestion is something that occurs in natural bodies. Chemical reactions in the glassware is not an instance of digestion because no natural body is digesting anything. Living bodies digest their food, and Aristotle thinks that this happens for the sake of an end.
Aristotle does not think that all natural bodies have minds and act for reasons. He does not think that digestion is a behavior a living body chooses as a matter of practical reasoning and deliberation. According to Aristotle, reasoning and deliberation is not a necessary condition for teleological behavior. He thinks that the "for something" is present in things that do not deliberate.
An Argument for the "For Something"
In Physics II.8, Aristotle considers and rejects the alternative. "Why," he asks "should we suppose nature acts for something (ἕνεκά του) and because it is better?" Why not, he asks, should we not instead accept the non-teleological conception of nature in the inquirers into nature.
"Why should not everything be like the rain? Zeus does not drop the
rain to make the corn grow. It comes of necessity. The rising vapour is condensed into water by the cold, and must then descend, and incidentally (συμβαίνει),
when this happens, the corn grows. If someone’s corn on the threshing floor is
ruined it does not rain for the sake (ἕνεκα) of this, so that the corn is ruined, but the result
is incidental (συμβέβηκεν) to the raining. What, then, is to stop the parts of nature from being
like this--the front teeth of necessity growing sharp and suitable for biting, the back
teeth broad and serviceable for chewing the food, not coming to be for this, but by coincidence
(συμπεσεῖν)? And similarly for the other parts in which the for something (ἕνεκά του) seems
to be present. So that when all things turned out just as they had come to be for something,
then the things, suitably constituted as an automatic outcome (αὐτομάτου), survived; when not,
"Thus Empedocles says that at the beginning of Love there were born first, as
it happened by chance, the parts of animals, like heads, hands, and feet, and
that later these came together,
that is, composites of cattle and human beings. And all the parts that were
assembled with one another in such as way as to be capable of surviving became
animals and continued to exist because they satisfied each other’s needs,
the teeth cutting and chewing the food, the stomach digesting it, the liver
turning it into blood. And a human head, coming together with a human body,
ensures the survival of the whole, but with a cow’s [scil. body] it is not
adapted and is destroyed. For whatever did not come together according to an
appropriate relation perished. It is in the same way that everything happens now too"
(Simplicius, Commentary on Aristotle’s Physics).
"...Races of man-prowed cattle, while others sprang up inversely, Creatures of cattle-headed men..." (Aelian, On the Nature of Animals (DK 31 B 61)). they died, and die, as Empedocles says of the man-headed calves" (Physics II.8.198b).
Aristotle rejects this non-teleological understanding of regularity in nature.
"This argument, or something like it, might give us pause. It is impossible, however, that this should be how things are. The things mentioned, and all the things which are due to nature, come to be as they do always or for the most part, and nothing which is the outcome of luck (τύχης) or an automatic outcome (αὐτομάτου) does that [= come as they do always or for the most part]. We do not think that it is the outcome of luck or coincidence (συμπτώματος) that there is a lot of rain in winter, but only if there is a lot of rain in August; nor that there are heatwaves in August, but only if there is a heatwave in winter. If, then, things seem to be coincidental outcome or for something (ἕνεκά του), and the things we are discussing cannot neither be a coincidental nor a automatic outcome, they must be for something (ἕνεκά του). But all such things are due to nature, as the authors of the views under discussion themselves admit. The for something, then, is present in things which are and come to be due to nature" (Physics II.8.198b).
The Beginning of a Solution
Socrates hoped to learn from Anaxagoras that things happen as they do because νοῦς, in arranging things, arranges them so that things happen for the best. Aristotle can provide the sort of solution Socrates hoped to learn from Anaxagoras if he can work out a way in which natural bodies exercise their ways of functioning for the sake of having the best possible existence.
To work out this teleological conception of natural bodies, Aristotle argues for the existence of the "unmovable first mover" (πρῶτον κινοῦν ἀκίνητον).
How the unmovable first mover is the teleological cause for the sake of which other things change is not easy to understand in detail. The idea is perhaps most straightforward in the case of development of reason in human beings, so is is helpful at this point to turn to Aristotle's discussion of the "soul" (ψυχή) in general and the form it takes in human beings.
Perseus Digital Library:
Henry George Liddell, Robert Scott, A Greek-English Lexicon:
αὐτόματος, adjective, "spontaneous,"
ἕνεκα, preposition, "on account of,"
ἕνεκά του, "for something," τὸ οὗ ἕνεκα, "the for something,"
οὗ ἕνεκα, "that for the sake of which," τὸ οὗ ἕνεκα, "the that for the sake of which," συμβαίνει, third person singular present form of συμβαίνω, verb, "to stand with feet together,"
συμβέβηκεν, form of συμβαίνω
Aristotle's four causes: the "material cause, τὸ ἐξ οὗ, "the that out of which," the "formal cause," τὸ τί ἦν εἶναι, "the what it is to be," and the "efficient cause," ὅθεν, "that form which," and the "final cause," τὸ οὗ ἕνεκα
Arizona State University Library. Loeb Classical Library:
Empedocles, Early Greek Philosophy, Volume V: Western Greek Thinkers, Part 2
"There is nothing in Aristotle to prevent us from saying that this process can be understood and explained in terms of the appropriate kind of chemistry. And yet to understand the process this way is not to understand it as the natural process it is. Presumably the same process, as described in material terms, could be reproduced artificially. But if it were, it would not be a case of digestion. And this not because it lacked some details or some mysterious quality the natural process has, but because it, as a whole and its details, would have to be explained differently. What makes the digestion of food the process it is, and hence is essential to our understanding of it, is that it is the exercise of the capacity or ability of this kind of organism to digest food. And similarly for the other life functions. In each case there is a material description in terms of material parts of the organism and of what happens to them in terms of their properties. But in each case the process is the natural or physical process it is, rather than a materially equivalent but formally different process only, because it is the exercise of an ability the organism has in virtue of its form or soul" (Michael Frede, "On Aristotle's Conception of the Soul," 150. Modern Thinker and Ancient Thinkers: The Stanley Victor Keeling Memorial Lectures at University College London, 1981-1991, edited by R.W. Sharples (University College London Press, 1993), 138-156).