[MUSIC] Natural Teleology. Nature is one of the causes that are for something. This is a thesis that Aristotle sets out to defend in Chapter 8 of Book 2 of the Physics. Recall that nature is an internal principle of change, and that what something is for is a final cause, the goal, or good. So Aristotle's thesis is that natural changes are goal directed, that they have a final cause. He considers an animal that typically develops teeth that are flat in the back, and so good for chewing, and sharp in the front. Good for biting off things to chew. Let's suppose this is a dog. On the whole, this is a good arrangement for the dog, whose life would be a lot more difficult if the sharp teeth were in the back, and the flat ones in the front. Okay, so we've identified a good result of the dog's natural development. Now Aristotle's claim is that this good result is the goal of the process of development, that all the complex business of the growing animal, taking in nutrients, building tissues, excreting wastes, and so forth is all directed at producing teeth that are flat in the back and sharp in front. And presumably all the other doggy features. It doesn't just happen to turn out that way. There was a principal, the dogs nature aiming at that result. The alternative hypothesis, the one Aristotle finds in his pre-Socratic predecessors, Democritus and Empedocles, is that the good teeth are just a coincidental result of a lot of earth, air, fire, and water going about, doing their natural business inside and outside the dog. Earth trying to go down, fire trying to go up, air and water trying to get to their respective locations. All of them getting in each other's way. Some of them transforming into each other. And all of them ending up collectively in an arrangement that happens to be good for the dog. On this alternative hypothesis, the good teeth that result from all this elemental activity are only a coincidental result of the development, like the crop growth that results from rain fall. On Aristotle's version of the rain cycle, rain falls because air that has been drawn up by it's natural motion then cools down and becomes water, an elemental transformation. And water's natural motion is to go down. The rain that comes down as a result of this process is certainly good for any crops that have been planted. But it falls regardless of whether any such benefit will result. In just the same way the opponents claim, the natural motions of earth, air, fire, and water end up producing teeth that are good for biting and chewing. But they would yield the same configuration of enamel, bone, and gum regardless of whether this was useful for the animal. Now as I read the structure of the disagreement here and there's a lot of controversy among interpreters of Aristotle on this point. Aristotle is prepared to concede to the opponents that it is completely coincidental that it rains when the crops need it. But he insists that it's not a coincidence that the animal develops teeth that are good for biting and chewing. There is a significant difference between the rain case and the teeth case in his view. The difference, he tells us, is that the rain cycle doesn't benefit the crops always or for the most part. Whereas dogs do generally grow teeth that are good for biting and chewing. He is assuming, in line with his discussion of chance in previous chapters, that if a causal process yields a particular result always or for the most part, it's not a coincidence. As he puts it no result of luck or chance, that is no coincidence, comes to be either always or for the most part. He explains this point by invoking the rainfall again, which is a bit confusing since this time he's not asking whether the benefit to the crops is a coincidence, but rather whether the rain itself is a coincidence. It's not a coincidence if it rains in the winter, since this is the rainy season in Greece. But it is a coincidence if it rains in the summer, since this is typically the dry season. We can understand the seasonal difference as follows. It tends to rain a lot in the winter because that's when temperatures are cooler. And so air, doing what it naturally does by rising, will be chilled, thus generating the cycle of condensation that issues in rain. So it's not coincidental that there's a lot of rain in the winter. But it is coincidental if it rains in the summer, since something unusual has to happen to produce the cold temperature that is crucial for the rain cycle. The main point here is that winter conditions are reliable rain producers, while summer conditions are not. That makes it a coincidence if it rains in the summer, but not if it rains in the winter. Now let's consider why Aristotle agrees with his opponents that making the crops grow is only a coincidental result of the rain cycle. Recall that a coincidental result is irregular or infrequent. Does rain reliably make crops grow? Well, only in certain circumstances. If it rains a lot before planting, that's no good for the crops, since the farmers won't be able to work in the muddy soil. And as Aristotle notes, it's bad for it to rain after the grain has been harvested, since that will spoil the yield. So only if it rains between planting and harvesting is it good for the crops. Now, does the rain cycle have anything in it that makes rainfall more likely during the times when it's good for the crops? Of course, the farmers do their best to plant the grain at a time when the rain is likely to fall. So in a well functioning agricultural system, it won't be a coincidence that the rain falls when the crops need it. But the credit for that regularity is entirely due to the farmers who arrange their planting schedule to fit the predictable rainfall. The rain is going to fall no matter what the farmers do, as we can see since it falls on cultivated and uncultivated fields alike. There is no intrinsic feature of the rain cycle that makes it reliable at growing crops. For that kind of reliability you have to depend on the farmers. So as far as the rain cycle is concerned the benefit to the crops is coincidental. Now let's go back to the case of the dog's teeth. Are they good for biting and chewing as a coincidental result of the dog's development or are teeth of this sort a regular and predictable result of that development? Clearly, the second, Aristotle insists. Teeth that are flat in the back and sharp in front are a regular and reliable result of a dog's development and so they are not a coincidental result. And the same is true of all the species typical features of animals and plants. Aristotle is saying to his opponents, look what's growing is a dog, it's the offspring of a dog and unless something goes wrong, which of course can happen, it's going to end up having the sort of teeth that dogs typically have. His point is that there is a regularity and reliability in the process that gives dogs teeth of this sort, along with all the other doggy features. We are not going to see that regularity if we only look to the natural movements of the dogs elemental constituents, however. The regularity obtains at the level of the dog's form, not its matter. We are now in a position to appreciate Aristotle's summary of his case against the opposition. Teeth and other parts and all natural things come to be as they do either always or usually. Whereas no result of luck or chance comes to be either always or usually. If then these seem either to be coincidental results or to be for something, and they cannot be coincidental or chance results, they are for something. The argument can be summarized as follows. Step one, dogs typically develop teeth good for biting and chewing. Two, a typical result is not a coincidence. Three, so it's not a coincidence that dogs develop teeth good for biting and chewing. Four, if the development is not coincidental, it must be for something. Five, so the dog's development is for something. That is, it is goal directed, which is exactly what Aristotle has set out to prove in this chapter. What do you think of this argument? Has Aristotle convinced you that natural processes, like animal and plant growth, are goal directed?
