An Essay on Final Cause in Aristotle’s Physics

One goal of Aristotle’s natural philosophy is to show that final causes exist in nature. Aristotle makes this claim because he believes that things grow for the sake of something; he shows this by distinguishing the regular and predictable manner of growth of natural things from spontaneous, chance growth (199a7–8). I will argue that this argument is sound because it eliminates the possibility that a thing which arises in a regular and predictable manner does not also arise for the sake of something.

Early in the Physics, Aristotle outlines the four causes for a natural thing’s existence. The material cause is that out of which it is made, the efficient cause who or what constructs it, the formal cause its shape, and the final cause its ultimate purpose or “end” (194b24–195a3). In other words, the final cause of a thing is the reason for which it exists and the purpose it serves in its existence. Natural things are substances which have an internal principle of motion that allows them to grow and change without an external actor (192b12–15). Aristotle makes distinctions between natural things which arise for the sake of something — i.e., they have a final cause — and things which arise spontaneously or by chance. In this paper I will refer to natural things which have a final cause in three ways: as things that arise in deliberate service of a particular end, that grow for the sake of something, or that exhibit goal-directed growth.

In Book 2 of his Physics, Aristotle offers a concise argument for the existence of final cause in nature (198b10–199a5). In one part of his first premise, he argues that if a thing grows in regular and predictable manner, then it grows neither spontaneously nor by chance. If a thing grows in a regular and predictable manner, this means that with each new occurrence of that thing, it grows in essentially the same way. In his third premise, he argues that natural things grow in a regular and predictable manner by giving the example of teeth development. For any kind of natural thing with teeth, say humans, teeth grow in roughly the same manner among all members of that group of things. This occurs nearly invariably, meaning that each member of the group has teeth which grew in the same way and are very similar (198b35–36). Since members of these groups tend to share characteristics in this way, whether with their teeth or in some other way, natural things quite clearly appear to arise in a regular and predictable manner.

In the second half of his first premise, Aristotle argues that if something does arise in a regular and predictable manner as natural things do, then it arises neither spontaneously nor by chance. To substantiate this claim, Aristotle distinguishes something which arises in a regular and predictable manner — e.g., rainfall during the Athenian winter — from a deviation from this pattern like summer rain. In both cases, rainfall occurs necessarily; in other words, once commenced, it proceeds to its conclusion because of the demands of the water cycle regardless of surrounding conditions. However, while winter rainfall comes about in a regular and predictable manner, summer rainfall is an unexpected and erratic occurrence. We thus ascribe it to chance or spontaneity in spite of the ultimate necessity of its taking place (199a1–3). By distinguishing between regular and predictable growth and spontaneous or chance growth in this way, Aristotle argues plausibly that the two cannot happen in the same instance.

In his second premise, Aristotle argues that if something arises neither spontaneously nor by chance, then it arises in deliberate service of a particular end; its growth is for the sake of something, goal-directed, and driven towards a final cause (199a3–6). Here he attempts to link growth which arises in a regular and predictable manner with growth which arises in deliberate service of a particular end. Aristotle makes the assumption that things only either grow in deliberate service of an end or spontaneously and by chance. Having established in his first premise that things also only arise either in a regular and predictable manner or spontaneously and by chance, he can then argue that if something does not arise in the latter manner, then it must arise both for the sake of something and in a regular and predictable manner (199a3–6). This idea in conjunction with his third premise forms the basis of his conclusion that natural things arise for the sake of something and that final cause thus exists in nature (199a7–8). A formal reconstruction of this argument is given below:

P1) If something grows in a regular and predictable manner, then it arises neither spontaneously nor by chance.

P2) If something arises neither spontaneously nor by chance, then it arises in deliberate service of a particular end.

P3) Natural things grow in a regular and predictable manner.

C) Natural things arise in deliberate service of a particular end; hence, growth for the sake of an end happens in nature.

I have reconstructed the above argument using a hypothetical syllogism. I believe that this argument is valid because when all premises hold true, the conclusion must be true. I also view the argument as sound because it is valid and because I consider each premise to hold true.

Of the premises Aristotle enumerates to argue that final causes exist in nature, the second one most merits further consideration and perhaps objection. This premise holds that if a thing arises neither spontaneously nor by chance, then it arises in deliberate service of an end; in other words, there must be a final cause behind its growth. In making this claim, Aristotle suggests that only two possibilities for the growth of things exist: either something arises spontaneously or by chance, or its growth is goal-directed and done for the sake of something (199a3–5). Naturally, one might object to this assertion by wondering if a third kind of growth exists, namely one by which something neither comes about spontaneously nor in deliberate service of an end. Without arguing against Aristotle’s conclusion that final causes exist in nature, could there be a kind of growth which is regular, non-spontaneous, and which does not serve a particular end?

In fact, the argument which Aristotle refutes in making his own might serve to elucidate this point. Just before he offers his rebuttal to it, Aristotle summarizes the argument of those who say that perhaps things in nature simply come about because it is necessary that they do so (198b17–19). In other words, things grow as they do purely by necessity rather than because such growth is optimal or goal-directed. By this logic, which somewhat resembles evolutionary biology, things tend to be “organized spontaneously in a fitting way” such that they either grow in accordance with the regularities of their environment and survive or happen to be maladjusted and perish (198b30–31). Proponents of this argument thus claim that natural processes like rainfall or teeth development unfold as they do simply because they must do so, and the ends served or disserved by this unfolding are merely so coincidentally — by chance. Aristotle is right to object to the role of chance advanced by this view, since any natural process occurs regularly and predictably and cannot be said to have resulted from chance (198b35–199a1). But a refinement of the first argument which keeps its suggestion that some natural processes occur necessarily rather than for the sake of something, but which avoids its conclusion that nature is “organized spontaneously”, could challenge the idea that only two types of growth exist.

This objection to Aristotle’s second premise could suggest that he relies too heavily, even implicitly, on a higher or divine design which arranges nature’s final causes in harmony. It seems plausible to argue that, while winter rainfall and summer heat occur in a regular and predictable manner free from chance or spontaneity, they nevertheless do not occur with humans, plants, or animals in mind. In other words, while it is true that rainfall occurs neither spontaneously nor by chance, perhaps it does not occur for the sake of crop cultivation; after all, it would presumably occur in the same way regardless of whether crops were planted or not, as Aristotle’s opponents argue (198b20–23). Moreover, this time in contrast to what his opponents argue, the concept of purely necessary rather than goal-directed growth in nature does not mean that chance defines the way that natural things arise. Instead, some natural processes unfold by necessity, such as rainfall according to the water cycle or heat according to the Earth’s solar orbit, while others occur for the sake of some end, like human teeth development for the sake of easy consumption of food. Perhaps an overarching element of chance determines which thing’s final cause is ultimately compatible with its natural surroundings; then chance would effectively govern the relations among natural things without determining the way in which a thing actually grows. This slight critique to the idea that all natural things are designed with final causes in harmony with one another seems plausible, since humans are imperfect and even somewhat maladjusted to their environments.

Aristotle or a defender of his would likely reply to this objection by arguing that it depends upon an imprecise conception of spontaneity and chance. By saying that a natural process occurs regularly and predictably, neither spontaneously nor by chance, and not in deliberate service of an end, the objector risks distorting the meaning of spontaneity given by a charitable reading of Aristotle’s argument. If one argues that a natural process like winter rainfall arises only by necessity, then it is difficult to evade the logical consequence of this line of reasoning: that the end, here the cultivation of crops, was not deliberately served but instead served spontaneously or by chance. This returns us to the very point offered by the objector on rainfall, which was that the element of chance only concerns a final cause’s compatibility with its surroundings, not the growth of the natural thing. (For example, teeth development has a final cause which corresponds to the kind of food a thing is meant to eat. Chance concerns not this development, but only whether that end — the consumption of certain foods — allows the thing to survive in its environment.)

This point leads to a contradiction which disqualifies the objection to Aristotle’s second premise, thus rendering his argument sound. Since they cannot avoid the conclusion that some things survive and others perish because of the compatibility of their final causes with their environments, and since they attempt not to ascribe such outcomes to a design which arranges these final causes in harmony, objectors attempt to separate chance from the growth of natural things by designating it as an overarching arbiter. But this makes chance a part of nature, which creates the contradiction. As Aristotle argues, if the growth of a natural thing arises in some way from spontaneity or chance, which it would do if chance were an arbiter, then that thing cannot have arisen in a regular and predictable manner (199a1). This conflicts with premise three, which states as even the objector would do that natural things grow in a regular and predictable manner (198b35–36). Since the objection to premise two has been disqualified by contradiction, it is true that if a thing arises neither spontaneously nor by chance, then it arises in deliberate service of a particular end. These are the only two types of growth for a natural thing. It follows from this that natural things, which grow in a regular and predictable manner and therefore neither spontaneously nor by chance, must arise in deliberate service of an end (199a3–6). Aristotle’s conclusion that final cause exists in the way that things come to be and are in nature thus stands.

In this paper, I recount Aristotle’s argument for the existence of final causes in nature and argue that it is sound. I do so by first offering an explanation of each premise individually and as it contributes to the conclusion. I then formally reconstruct and analyze Aristotle’s argument from Book 2 of the Physics, after which I present and entertain an objection to the argument’s second premise. I then offer my conception of what Aristotle’s reply to this objection might have been and argue that this reply refutes the objection. Finally, I analyze his original argument in light of its vindication and assert that his conclusion that final cause exists in nature is true.

Bibliography

Barnes, Jonathan. “The Complete Works of Aristotle: The Revised Oxford Translation, Vol. 1”. Princeton University Press. 1984.