Athens

ARISTOTLE (384–322 BC) SAID, "Knowledge is the object of our inquiry, and men do not think they know a thing till they have grasped the 'why' of it (which is to grasp its primary cause)." He was not the first to raise the question of causation, for it was nigh an obsession of his philosophical predecessors, back through his teacher Plato (ca. 429–347 BC) to Socrates (469–399 BC), and to the earlier "pre-Socratic" thinkers, including Empedocles (ca. 495–435 BC), Anaxagoras (ca. 510–ca. 428 BC), and the atomist Democritus (ca. 460–ca. 370 BC). They all grasped that in some sense causation — what it is that makes things happen — is (or is often taken to be) both a backward-looking matter and a forward-looking matter. The nail is driven into the piece of wood. Backward-looking in the sense that this happens because a hammer was picked up and used to hit the head of the nail; forward-looking in the sense that this happens because the builder wants to tie the planks together to support a roof. The builder did this "on purpose" or "for a purpose." He wanted that end. A roof was something of value to him.

I shall argue that this forward-looking side to causation — the subject of our inquiry — lends itself to three different approaches. I do not pretend to originality in spotting these approaches. Others, for instance, R. J. (Jim) Hankinson and Thomas Nagel, have certainly remarked on this triune side. It is in tracing the way that it persists that makes the story so interesting and illuminating. The first approach, often known as "external" teleology, is the most obvious and intuitively plausible. It involves a mind, whether human or divine or something else. "For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life" (John 3:16). God, right now, let Jesus die on the cross, so that you, the sinner, should have everlasting life in the future. The second approach, often known as "internal teleology," is a bit trickier. It involves a kind of life force in some sense, something that need not be conscious, and actually in the broader sense need not even be alive. It might be more a kind of principle of ordering about the world, something that makes everything essentially end-directed. When we see it being argued for, we shall get a better sense of what it is all about. These two notions of purpose, of teleology, go back readily to the Greeks. The third kind of approach we might call "eliminative" or, more positively, "heuristic" teleology, seeing forward-looking causation — purpose — as in some sense purely conceptual, something we might use to understand the world but in no sense constitutive of the world. This label would apply to — or at least is anticipated in — the approach of Democritus and comes out more vividly in the (several centuries later) poetry of the Roman Lucretius (ca. 99–ca. 55 BC). But it is not until the modern era that this approach could be developed fully.

With respect to the first two approaches, it is not always easy to tell if one has either external or internal teleology. In Emily Dickinson's poem, is there a designer god behind everything or is it all a matter of an impersonal force, an Immanent Will (as it has sometimes been called)? What we can say is that Plato offered the first full discussion of external teleology and Aristotle the first full discussion of internal teleology, with the atomists at the least the forerunners of the heuristic option.

Plato

There are two main sources for Plato's thinking about purpose, about teleology. The first is in the Phaedo, the dialogue about Socrates's last day on Earth. It is a middle dialogue, and given the nature of the discussion is generally considered a vehicle for Plato's own thinking — apart from anything else, Plato notes explicitly that he himself was not present, which gives us a clue that there has to be some element of creativity — although there is a comparable discussion attributed to Socrates himself by Xenophon (ca. 430–354 BC), and a version of the argumentation may go back to Anaxagoras. Surrounded by the young men who are his followers, much of the discussion Socrates directs is (hardly surprisingly) about key issues, such as the nature of the soul — more on this shortly — and questions about existence beyond this life. Almost in passing, Socrates raises the question of the deity. It is not so much a question of offering a formal proof but in showing how we need such a concept in order to make sense of the ways in which we understand things.

Normally, such an issue doesn't arise. "I thought before that it was obvious to anybody that men grew through eating and drinking, for food adds flesh to flesh and bones to bones, and in the same way appropriate parts were added to all other parts of the body, so that the man grew from an earlier small bulk to a large bulk later, and so a small man became big." This is backward-looking causation, that is, what we have seen called "efficient causation." Plato acknowledges that this is not a bad explanation — we do get bigger thanks to eating and drinking — but it is in some sense incomplete. Why would one bother to eat and drink? Why would one want to grow and put on weight? See here how the notion of value is coming in. What is the point of doing something? What's the purpose? Why do we want the end result? Here we need to switch to forward-looking causation or (what within the Aristotelian system was called) "final cause." We are — or rather will be — better off if we grow. This is crucial. Something happens that we value. Which is just fine and dandy, but why should it happen? Why doesn't eating and drinking make us lose weight? "One day I heard someone reading, as he said, from a book of Anaxagoras, and saying that it is Mind that directs and is the cause of everything. I was delighted with this cause and it seemed to me to be good, in a way, that Mind should be the cause of all. I thought that if this were so, the directing Mind would direct everything and arrange each thing in the way that was best." So now one has a guide to discovery. "Then if one wished to know the cause of each thing, why it comes to be or perishes or exists, one had to find what the best way was for it to be, or to be acted upon, or to act."

Note that we have a heuristic here but more than this, although it is more a presupposition than an explicit proof. Things don't just happen. They are ordered for the best, and this is done by a mind — or rather by a Mind. The teleology in this sense is external — imposed upon the world from without.

Atomist Interlude

Pause for a moment, to dig a little more deeply. You have features, let us say teeth or hands or...