 Hi, I'm Peter Adamson, and you're listening to the History of Philosophy podcast, brought to you with the support of King's College London and the Leverhulme Trust, online at www.historyofphilosophy.net. Today's episode, Form and Function, Aristotle's Four Causes. If you're listening to this, you must own, or at least have access to, a computer. Maybe you're looking at it right now, as you listen to this online. But if you're anything like me, there is a lot that you don't understand about your computer. For me, computers might as well be magical devices. I turn it on, and it starts to glow, giving me powers I do not possess by nature, like the ability to download podcasts and to watch amusing videos about cats on YouTube. But of course, some people do understand computers, the ones who design, study, build, and repair them. These people are in a good position to answer all kinds of questions about computers. We might describe them as computer scientists. Some of them indeed describe themselves this way. The more that someone understands about computers, the more claim they would have to possess the science of computers. For all his achievements, Aristotle was of course not a computer scientist. This was a man whose prodigious accomplishments were achieved without the benefit of Wikipedia or amusing videos about cats. Actually, that may have been an advantage. But if Aristotle were shown a computer, he would agree that there must be some kind of science or knowledge for computers, what he would call the episteme of computers. For him, this would amount to being able to give causal explanations of computers and the things they can do. As we saw a couple of weeks ago, his theory of knowledge assumes that having episteme means being able to give such explanations by means of a demonstration. The goal is to understand not just that something is the case, but why something is the case. Aristotle is thus very interested in what sorts of causal accounts we can give. Is there any systematic way of dividing up the kinds of explanation that can feature in demonstrations? To put this in a less technical way, Aristotle wants to know how many different kinds of answer are there to why questions. Given the title of this episode, it's a bit late for me to leave you in suspense, so I'll just say right off that, according to Aristotle, there are four kinds of cause or explanation, material, formal, efficient, and final. These English terms are drawn not from Greek, but from Latin translations of Aristotle's Greek. For instance, efficient relates to the Latin verb efficio, which means do or bring about. Thus, the efficient cause is the one that brings something about. For instance, the carpenter who builds a table is the efficient cause of the table. Similarly, the word final relates to the Latin word for end or purpose, a final cause being a purpose or goal. Aristotle often uses less technical expressions for his four causes, as when he refers to the category of final cause as that for the sake of which. Aristotle sets out his four kinds of cause in the third chapter of the second book of the Physics. Perhaps the easiest of the four to understand is the material cause. This is just whatever something is made of. Aristotle gives the example of a statue being made of bronze. The next kind of cause is formal. The form will be whatever gives something its definition or determination. Aristotle's example is that the form of the octave is the ratio of 2 to 1. What he has in mind is the strings on a stringed instrument. If you have two strings at the same tension, one of which is exactly half as long as the other, the notes they give when struck will be one octave apart. Third is the efficient cause, which brings something to be by imposing form on the matter. Aristotle provides the example of the father being the cause for his child. The final type of cause is, appropriately enough, the final type of cause. Final causes are purposes. Aristotle's example is that health is the final cause of taking a walk or of administering medicine. With all due respect to Aristotle, these examples are less helpful than they might be. In particular, it isn't so helpful when he illustrates formal cause with the example of the octave. And it would be nice to have him enumerate causes of all four types for one and the same thing, so let's try to do that using the example I started with at the beginning of this episode, a computer. If we can apply the four causes to a computer, that would testify to the perennial utility of Aristotle's scheme. Unfortunately what I know about computers could fit onto a 1980s floppy disk, but I'll do my best. Let's warm up with the material cause, which is easy enough. The matter of a computer is whatever it is made of, like plastic and silicon. The formal cause will be the structure of the computer, roughly speaking the way that the matter is arranged in order to yield a computer. So this might include things like being a certain shape, having the circuit set out in a certain order, the pattern of keys in the keyboard, and so on. But the true form of the computer is going to consist only of the structural elements it needs to be a computer. The fact that the G key is right in the middle of the keyboard will only be incidental because the G key could be moved elsewhere on the keyboard without rendering the device nonfunctional. To use terminology I introduced last time, the formal cause of a computer is what gives the computer its essential properties, the features it must have if it is to be a computer. So the placement of the G key is not vital, but the computer must be able to process information for instance. Its ability to do this will derive from its arrangement or form. This is why Aristotle says, in the physics and elsewhere, that the form of a thing is closely related to its essence. As for the efficient cause, this too is easy to name. It is the person who built the computer, just as the father is the efficient cause of the child. In general, it looks like an efficient cause is whatever comes along and does something, so that something else comes to be. This immediately raises the prospect that eternal things, things that have always existed, cannot have efficient causes. It may not seem that important a point, but philosophers will wrestle with this implication of Aristotle's theory for many centuries in the late ancient and medieval periods, so stay tuned for that. Incidentally, you might worry that your computer wasn't put together by just one mechanic with a screwdriver. Won't the efficient cause be a whole team of people, or perhaps machines in a factory? Well why not? Aristotle would be happy to admit that many entities sometimes come together to form an efficient cause. Imagine for instance a battalion of soldiers pushing their boat out to sea, perhaps one of the ships launched by Helen's beautiful face. They are jointly the efficient cause of the boat's movement into the water. As for the final cause, in the example I just gave, the purpose of launching the ship would be to retrieve Helen from Troy, and the purpose of the computer of course is to watch amusing videos about cats on YouTube. And more generally to process and store information. Notice that the final cause is intimately related to the formal cause. The form of a computer is basically whatever allows it to achieve its purpose. This is exactly what we would expect of course. It amounts to saying that the design of the computer enables it to do what it was designed for. For a full explanation, we can add in the efficient and final cause. An efficient cause, for instance a human, comes along and formulates a purpose to be achieved, and that's the final cause. This agent then selects some appropriate materials, the material cause, and imposes upon them the form suitable to the task. To give a more Aristotelian example than the computer, a carpenter might impose the form of a table on some wood in order to have something to eat off. The carpenter is the efficient cause, the shape and structure of the table is the formal cause, the wood is the material cause, and having something to eat off is the final cause. Now I know what you're thinking. Are these all really causes? Of the four types Aristotle has named, there is really only one we'd normally describe as a cause, namely efficient cause. For us, causes are pushers and pullers. They are whatever makes something happen, whatever introduces a change in the world. But Aristotle will say, hang on a minute, you might remember from the last episode that to explain change we need both matter and form. The matter is whatever persists through the change and the form is whatever is added to or subtracted from the matter. For instance, when a rock is heated, the rock is the matter and heat is the new form. When wood becomes a table, the wood is the matter that remains and the form of table is added. So if it's change you're interested in, you will need to agree that matter and form are vital. Moreover, Aristotle can point out that matter and form remain on the scene even after the efficient cause has done its job. The carpenter leaves the workshop and goes to sleep, or perhaps even dies, but the wood is still shaped as a table. You might retort, okay Aristotle, I grant that it is useful to invoke matter and form when discussing change, but that doesn't make matter and form causes. The cause is the carpenter, or more generally the efficient cause, the thing which brought about the change. We don't need to talk about causes for a table that is standing still in a quiet workshop. But Aristotle will remind you what we started out trying to do. We were trying to learn how many kinds of answer there are for why questions. Efficient causes do fit the bill. Why is there a table here? Because the carpenter built it. But how about why does this table have sharp corners? Because the top is square, an answer in terms of formal cause. Or why is this table flammable? Because it's made of wood, an answer that invokes material cause. Aristotle wants us to see that we can't understand or explain things without invoking their form and matter as well as their efficient causes. Talking about pushers and pullers will only get you so far. Since you have struggled against Aristotle for this long, you're clearly not easy to please. So even now, you will probably want to draw a line in the sand. You're the efficient cause, the sand is the material cause, line is the formal cause, sorry, once you get going it's hard to stop. So you'll want to say, okay Aristotle, I'll grant you three of your four causes. The carpenter, the wood, the shape of the table, those are all real things out in the world. They have, so to speak, metaphysical respectability. So it's fine to point to them as kinds of cause. But what about the fourth type, the final cause? There are no purposes or goals floating around free in the world. The carpenter might have a goal in mind when he builds the table, like to eat off of it or to make money by selling it, but if this is a cause, it's a cause in a very different sense. We can see this, you will insist, if we think about the difference between a table or a computer on the one hand and something like a giraffe on the other hand. Giraffes too have efficient causes, namely their giraffe fathers. And they have form and matter, as we saw in the last episode. But they do not have final causes. There is no goal or purpose to a giraffe, lovely though she may be. This is a big difference between man-made things and natural things, and the reason for the difference is that the goal of a man-made thing is imposed by the human who makes it. So we don't need to take final causes seriously in the same way as the other three kinds. Even if it is useful to talk about them when we're discussing carpentry and the like, final causes just aren't real. Here we've arrived at a notorious aspect of Aristotle's conception of nature. When you say that giraffes don't have purposes, have no final causes, he will firmly disagree. How can you say that a giraffe has no final cause, he will argue, when even the parts of giraffes clearly do have final causes? Aristotle needs only to mention the giraffe's famous neck, which has the purpose of allowing her to eat leaves off tall trees. Or maybe not, I've seen it claimed that the long necks are actually for fighting other giraffes, but I'm a philosopher, so I'm not going to let a few silly facts get in the way of a good example. In fact, if we look through the animal kingdom, we see example after example of animals that are amazingly fit for purpose. The frog with eyes that can look around while the rest of it stays underwater, the lizard whose skin is the same color as its environment, and so on. How can we explain this, Aristotle will ask, without saying that there are really final causes in nature? The parts of animals perform certain functions such as camouflage, reaching leaves, and watching for enemies. These functions contribute to the overall function of each animal, which is simply to flourish and reproduce so that its species is preserved through the generations. The same goes for plants, and of course, for humans, who likewise have bewilderingly complex bodies that can only be explained by admitting the presence of final causation. If I may introduce a technical term, we can therefore say that Aristotle's conception of nature is teleological. This word comes from the Greek telos, which means end or purpose. To say that nature is teleological is simply to claim that nature involves final causation. Here you will be tempted to smile indulgently and say that Aristotle's teleology was plausible in its day, but has ultimately been shown wrong by the theory of evolution. Since Darwin, we know that functional aspects of animals have nothing to do with some kind of natural final causation. They are rather the result of a long process whereby certain features are selected for inheritance depending on whether or not they are conducive to survival. The apparent design we see in nature is merely apparent. It is actually nothing but randomness constrained by the mechanisms of survival pressure and genetic inheritance. Poor Aristotle, of course, knew nothing of this, so his teleological theory is, quite literally, antiquated. But things are a bit more complicated. Aristotle did know of an attempt to explain natural phenomena by an appeal to chance rather than teleology. This is something we've seen already in the episode on the pre-Socratic philosopher Empedocles. To remind you, Empedocles believed that separate parts of animals arose first by chance, and then came together, randomly, to produce whole animals, with the suitable animals managing to reproduce. No one today can read the ancient report of this theory without thinking of evolution, and as it happens, the ancient report is found in this very same book of the physics. Aristotle presents Empedocles' theory as a challenge to his own, so he is well aware that one could try to explain nature through randomness, rather than final causation. Aristotle rejects the theory, for the following reason. For Empedocles, everything in the natural world is to be explained by chance. For instance, teeth would just happen to spring up in such a way that they are suitably arranged for grinding and tearing food. But this is simply a misunderstanding of what chance is. When I say that something is a chance or lucky event, this means that it is unusual precisely because it might have been intentional, but is not. Aristotle gives the example of looking for someone because I am collecting money for a feast, and then happening to run into him in the marketplace. Lucky me, I didn't go to the marketplace to find him, but I found him anyway. The result is as if intended, but not intended. Another example would be if a rock just happens to fall off a cliff at the right time to kill my enemy. Again, lucky for me. But if this is what chance or luck means, it is only intelligible against a background of things that really are intentional. What happens for the most part is that purposes are pursued and achieved, final causes do their work. Occasionally, but only occasionally, a desirable result is achieved without being pursued, without any final cause being involved, and that is what we call chance or luck. How then could everything in nature be like this, since the whole point of luck is to be exceptional, whereas nature is just what almost always happens? Aristotle's response to Empedocles is, I think, a reasonably effective one, if only because Empedocles has not spelled out the mechanisms by which random processes could yield uniform and predictable processes. At least on Aristotle's telling, Empedocles has said nothing about genetic inheritance and next to nothing about survival pressures. So oddly, Aristotle may have the better of this particular argument, even if Empedocles was closer to being right. But once we add the machinery of modern genetics and evolutionary theory, it seems that we really can dispense with final causes. Here, some scholars still attempt a last-ditch defense of Aristotle, by adopting a less metaphysically loaded reading of his teleology. On this reading, Aristotle would not insist that final causes are metaphysically real, rather he would say that they are required for us in making sense of nature. Whereas matter, form, and efficient causes are actually out there in the world, final causes would have a merely heuristic function. They would help us to explain what we see, without being a real part of what we see. This brings us back to where we started, which was Aristotle's quest to find explanations, to answer why questions, to produce demonstrative syllogisms and hence, knowledge. On the less metaphysical reading, Aristotle wants to say only that we can't avoid talking of function and purpose when we investigate nature. This makes his account rather plausible. While accepting evolutionary theory, we still happily speak of giraffes needing long necks in order to reach trees, and chameleons changing color in order to avoid being eaten. Perhaps that phrase in order to simply cannot be eliminated from our scientific language, and perhaps this is all Aristotle needs, the claim that final causes would appear in proper scientific explanations. This strikes me as a clever defense of Aristotle, though I suspect that he did have a more metaphysically committed understanding of final causes. We can reserve final judgment for a few weeks, since I will be devoting a future episode to Aristotle's views about animals. But animals are only one part of the natural world around us, and Aristotle has plenty to tell us about the natural world as a whole, not least in this work we've been discussing, the physics. Thus far, we've only scratched its surface. So naturally, you'll want to join me next time, as I take a look at Aristotle on nature and the cosmos, here on The History of Philosophy Without Any Gaps.