Regularity in the Natural World

A Teleological Understanding of 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 natural bodies of the kind have these behaviors because it makes them better.

In this way, with his teleological conception of natural bodies, Aristotle pushes back against the idea in the inquirers into nature that regularity in nature is not to be understood in terms of the activities of the traditional gods. Aristotle does not return to the picture in Hesiod and the theologists, but neither does he accept the conception in the inquiry into nature.

Aristotle's teleology is not straightforward to understand, but it is possible to begin to see what he has mind by considering a complaint Plato has Socrates press against Anaxagoras.

Socrates and Anaxagoras

"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 best to me to sit here and more right to remain and endure whatever penalty they ordered" (Phaedo 98b; cf. Timaeus 46d).

  "Because, Callicles, you know, Polus and I, if you recollect, decided that everything we do should be for the sake of (ἕνεκα) what is good. Do you agree with us in this view—that the good is the end (τέλος) of all our actions, and it is for its sake that all other things should be done, and not it for theirs? Do you add your vote to ours, and make a third?
  I do, Socrates" (Gorigas 449e).
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. Anaxagoras, however, according to Socrates, omits νοῦς from his explanations.

To explain why Anaxagoras was wrong to omit νοῦς, Socrates provides an analogous explanation he thinks is clearly unacceptable. To explain why he sits in jail, he says that the explanation is that he sits there, as opposed, say, to making his escape with Crito, because he decided that this course of action was better. Anaxagoras, however, according to Socrates, would say that Socrates sits in jail because his bones and sinews are arranged in a certain way. Socrates thinks this "neglects to mention the true causes," that he sits in jail because it seemed "more right to remain [in jail] and endure whatever penalty they [the Athenians] ordered."

The "For Something" is in Nature

Aristotle tries to provide the sort of explanation Socrates wanted to learn from Anaxagoras.

Aristotle does not think that all natural bodies of a given kind function in the regular ways they do because they, like Socrates, think that these ways of behavior are better for them. Aristotle thinks the "for something" is present in natural bodies that do not deliberate and that if it were not present in them, then it would be a coincidence that the regular ways in which they behave are better for them, just as on the Anaxagorean style of explanation of why Socrates sits in jail it is a coincidence that Socrates' bones and sinews are arranged so that he is sitting and that it is also true that sitting in jail seems better and "more right" than escaping with Crito. (Whereas in fact this not a coincidence. There a regular connection between Socrates' sitting (or doing whatever he is doing) and what seems better than the alternatives, and an explanation of why he is doing what he is doing sets out the cause that explains the regularity of this connection.)

Aristotle thinks of an "accidental" (αὐτόματος) outcome as one that happens coincidentally to why the outcome occurred. He thinks of "luck" (τύχη) as accidental outcome that happens in connection with a choice a human being makes. So, e.g., to use an example of Aristotle's, if a man goes to market and happens onto someone who owes him money, collecting the debt happens by luck.

"Among the things from thought some, such as a house or a statue, never owe their existence to accident (αὐτομάτου) or necessity but always to be for something (ἕνεκά του); others, like health and security, may also be due to chance (σωτηρία)" (Posterior Analytics II.95a).

"It is clear, then, that when any causal agency incidentally produces a significant result outside its aim, we attribute it to an accidental outcome; and in the special cases where such a result springs from deliberate action (though not aimed at it) on the part of a being capable of choice, we may say that it comes by luck" (Physics II.VI.197b).
"The question (ἀπορίαν) arises why we should suppose that nature acts for something (ἕνεκά του) and because it is better (βέλτιον), but just as Zeus does not drop the rain to make the corn grow but of of necessity the rising vapour is condensed into water by the cold, and then must descend, and incidentally (συμβαίνει), when this happens, the corn grows. If corn on the threshing floor is ruined it does not rain for this, so that the corn is ruined. This is incidental (συμβέβηκεν) to the rain. 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 (οὐ τούτου ἕνεκα γενέσθαι ἀλλὰ συμπεσεῖν)? And similarly for the other parts in which the for something seems to be present. So that when all things turned out just as they had come to be for something, the things, suitably set together as an accidental outcome (αὐτομάτου συστάντα), survived, and when not,
"Thus Empedocles says that at the beginning of Love [one the two forces Empedocles thinks moves things in nature] there were born first, as it happened by chance (ἔτυχε), 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 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 (DK B 31 61).




It is interesting to wonder why Aristotle did not take more seriously the evolutionary-style explanation that the ways living natural bodies of a given kind function were initially coincidences that became behavior that happens over and over again because these ways conferred survival value.

The reason, it seems, is that Aristotle understands the ways living natural bodies function in terms of forms and understands forms from within a broadly Platonic framework. This makes it difficult to think specific behavior could originate in the way Empedocles suggests.
they died, and die, as Empedocles says of the man-headed calves" (Physics II.8.198b).

Aristotle admits that this conception of regularity in nature "might give us pause," but he insists that this way in which the inquirers into nature understand regularity is incorrect.

"This account [of regularity in nature], or something like it, might give us pause, but it is impossible for things to be this way. The things mentioned, and all things 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 accidental outcome does that. We do not think it is an outcome of luck or chance (συμπτώματος) that there is a lot of rain in winter, but only if there is a lot 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 outcomes or for something, and the things we are discussing are not coincidental outcomes that happen accidentally, they must be for something. 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).

Aristotle thinks that because it happens over again and over again in nature that the regular ways in which natural bodies behave are better for them, the two are not connected coincidentally. He thinks that the connection could be coincidental only if the connection were infrequent.

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 explanation Socrates hoped to learn if he can work out a way in which the natural bodies function in the ways they do because "nature acts for something and because it is better."

To work out this understanding of natural bodies and the ways they function, Aristotle argues for the existence of the "unmovable first mover" (πρῶτον κινοῦν ἀκίνητον).

How the unmovable first mover causes natural bodies change in the ways they do is not easy to understand in detail. The idea is perhaps most straightforward in the case of the development of reason in human beings, so is is helpful at this point to turn to Aristotle's discussion of the "soul" (ψυχή) and the role it plays in the explanation of the ways human beings function.




Perseus Digital Library:
Aristotle, Metaphysics.

Henry George Liddell, Robert Scott, A Greek-English Lexicon:
αὐτόματος, automatos, adjective, "spontaneous, accidental"
ἕνεκα, heneka, preposition followed by the genitive case, "on account of, for the sake of, because of, for"
ἕνεκά του, heneka tou, "for something" (του is an indefinite singular pronoun in the genitive case)
συμβαίνω, symbainō, verb, "to stand with feet together"
συμβέβηκεν, perfect form of συμβαίνω
σύμπτωμα, symptōma, noun, "a chance occurrence"
τέλλω, verb, "to make arise, accomplish"
τέλος, noun, "fulfilment or completion"
τύχη, tychē, noun, "luck, fortune"

Charlton T. Lewis, Charles Short, A Latin Dictionary:
forma, noun, "form, contour, figure, shape"
species, noun, "the outward appearance, outside, exterior; shape, form, figure"

"[T]he judge of things was, they held, the mind—they thought that it alone deserves credence, because it alone perceives that which is eternally simple and uniform and true to its own quality. This thing they call the ἰδέαν, a name already given it by Plato; we can correctly term it form (speciem)" (Cicero, Academica I.30).

Aristotle recognizes four "predicables" (κατηγορίαι): "genus" (γένος, genus) and its subdivision "difference" (διαϕορά, differentia), "definition" (ὅρος, definitio), "property" (ἴδιον, proprietas), "accident" (συμβεβηκός, accidens) (Topics I.101b).

In his Isagoge (an introduction to Aristotle's Categories), Porphyry (3rd to 4th century CE) puts "species" in the place of "definition." Boethius (5th to 6th century CE) translated the Isagoge in Latin. This translation become the standard logic textbook in the early middle ages (from 5th or 6th century to the 10th century CE).

"Since it is necessary, Chrysaorius, both to the doctrine of Aristotle's Categories, to know what genus (genus), difference (differentia), species (species), property (proprium), and accident (accidens) are..." (Isagoge I, Corpus Scriptorum Latinorum).

On the Origin of the Species by means of Natural Selection,, Charles Darwin. 24 November 1859.


Arizona State University Library. Loeb Classical Library:
Aristotle, Physics
Empedocles, Early Greek Philosophy, Volume V: Western Greek Thinkers, Part 2


"There is nothing in Aristotle to prevent us from saying that this process [that occurs in digestion] 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).


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