 Hi, I'm Peter Adamson and you're listening to the History of Philosophy podcast, brought to you with the support of Kings College London and the Leverhulme Trust, online at www.historyofphilosophy.net. Today's episode, Classified Information, Aristotle's Biology. A short story by the Argentine writer Jorge Luis Borges imagines a Chinese encyclopedia entitled The Celestial Emporium of Benevolent Knowledge. This fictional work suggests a division of animals into fourteen kinds, namely, those that belong to the emperor, embalmed ones, those that are trained, suckling pigs, mermaids, fabulous ones, stray dogs, those included in the present classification, those that tremble as if they were mad, innumerable ones, those drawn with a very fine camel hair brush, others, those that have just broken a flower vase, and those that from a long way off look like flies. I don't know if this joke is partially meant to be at Aristotle's expense, but if not, it could have been. Aristotle is the father of animal classification. When we talk about the animal kingdoms being divided by genus and species, we are not only engaging in an Aristotelian project, but using Aristotelian terminology to pursue that project. The word genus comes from the Greek genos, Aristotle's name for a broad type within which a division is made. Animals were not the only thing Aristotle classified. As I mentioned in a previous episode, he and his students collected and categorized political constitutions of city-states. Even when he presents presocratic views, Aristotle shows his classifying instincts. You might remember how, in the physics, he divides up his predecessors in terms of how many principles they postulate to explain nature. He learned the practice of division from his master Plato. In two dialogues, The Sophist and Statesman, Plato has his characters try to reach definitions by dividing larger kinds into smaller kinds. It is emphasized that the divisions need to be made at the natural joints, rather than chopping at random like a bad butcher. This is the idea Borges is playing with. His imaginary celestial emporium reminds us just how many ways there are of dividing things up, and so invites us to ask whether classification is always arbitrary. But if you do think that there is a right way to divide, as Plato and Aristotle did, then a philosophical task awaits. We can understand the world by classifying the things in that world. We will sort out the frogs from the toads, and also the bullfrogs from the tree frogs. If we do the dividing right, and do it completely, we will get a comprehensive and accurate inventory of things in the world. Furthermore, we will understand how those things relate to one another. We will see that bullfrogs are closely related to tree frogs, since both are frogs, that frogs in general are related to salamanders, since both are amphibians, and that frogs are loosely related to giraffes, since both are animals. Aristotle already outlines a project of this kind in his logical works, suggesting that a definition will set out a general kind, a genus, like animal, and then divide off a more specific kind or species, like man, by saying what makes this type of animal special. Man will be the kind of animal that is rational, for instance. But there is more to philosophical understanding than mere classification. For Aristotle, as for Plato, true understanding or knowledge will require giving a causal account. In the animal world, the relevant causes will typically be final causes, that is, the purposes of things. For instance, we may distinguish between two species of bird on the basis of the shape of their beaks. This isn't yet an explanation, each type of bird has been isolated, but we don't yet have understanding. We understand when we come to see that, for instance, some beaks are designed to strain food out of pond water, while others are designed to pluck insects out of trees. This will be at least part of what it is to understand the difference between a duck and a woodpecker. A more detailed analysis might help explain the difference between different types of duck or different types of woodpecker. Again, understanding would come when we see what purposes the distinguishing features would serve. Aristotle's motto here is, nature does nothing in vain. Whatever makes each species special must serve a purpose, and help the members of that species to flourish. This whole train of thought is reflected in Aristotle's writings about animals, his zoological works. Along with a few smaller treatises, the main three texts are the history of animals, the parts of animals, and the generation of animals. These are sizable treatises. Altogether, zoology takes up more than a quarter of Aristotle's extant writings. The history of animals, in particular, is a massive, sprawling survey of information. In the title, the word history reflects the Greek historia, which just means an account laying out the results of an inquiry. Though Aristotle has included a good deal of hearsay, some of which he would have done better to ignore, the inquiry was undertaken largely by himself. After Plato's death and his departure from the academy, but before he founded his own school, the Lyceum, Aristotle travelled in the eastern Mediterranean. He had a particularly productive time on the island of Lesbos, where he undertook extensive scientific investigations. He studied marine animals with particular intensity and made some genuinely impressive discoveries. For instance, he was the first to note that whales and dolphins are not kinds of fish. Aristotle didn't just look at animals, though. He actually dissected them. He is able to talk in detail about the internal organs of animals, comparing different species, and talking about the variation in their reproductive systems, digestive organs, and so on. He urges us not to spurn the task of close observation and dissection, but to get our hands dirty. This, just as much as the study of the divine, heavenly bodies, provides an insight into the astonishingly well-designed world around us. Aristotle, in fact, says that astronomy and biology provide equal pleasure. The stars are nobler than terrestrial animals, but we have little access to them, something he compares to catching only a glimpse of one's beloved. The history of animals, all ten books of it, can seem a barely organized miscellany of facts. In a single chapter, it tells us that tortoises eat marjoram to avoid being poisoned after eating vipers, speaks of a man who could predict the weather by closely observing hedgehogs, and mentions that the marten likes honey and has genital organs that can be turned into a powder for medicine. One hopes the marten is given some honey first in compensation. But a more sensitive reading, one Aristotle suggests himself, would see the history of animals as a preparatory work for the parts of animals. On this reading, the history presents the observations that allow us to divide up the animal world into its types. Aristotle's fascination with certain details betrays this. By picking out the distinctive features of say the marten or tortoise, Aristotle prepares the way for scientific understanding. The parts of animals then supplies that understanding, by explaining the purposes of these distinctive features which serve to distinguish one species from another. Since nature does nothing in vain, any feature natural to a species will contribute to the proper functioning of the animals in that species. The eating of the marjoram, the shape of the birds' beaks, and so on, will all be hypothetically necessary, as Aristotle puts it. If the tortoise is to avoid being poisoned, it must eat marjoram. If the duck is to strain food from pond water, it needs a mouth that acts like a sieve, and so on. Aristotle's careful dissection of animals and their parts was motivated by this quest to understand these functions, like someone taking apart a car and trying to decide what each part is designed to do. Aristotle also records observations about plants, which seem to have been a specialty of his associate Theophrastus, who sojourned with him in Lesbos and wrote a work dedicated to plants. But Aristotle had a particular interest in animals. And no wonder. Animals are the most highly functional entities in Aristotle's functional, and hierarchical, world. At the bottom of his hierarchy are the familiar four elements, air, earth, fire, and water. These can all transform into one another cyclically, as Aristotle argues in another work called On Generation and Corruption. Here he's disagreeing with Plato, who believed that earth could not become any of the other elements. When the elements combine, they form basic constituents which are the same through and through, things like blood and bodily humours. These then combine again to form the more complicated parts of animals. It is really here that biological purposiveness enters into the equation. An organ like a liver or hand can only be understood within the context of the animal's functioning. As Aristotle says, an eye removed from its socket is an eye in name only. Of course, for all his careful observation, Aristotle did not always arrive at the right answers. He got things badly wrong when it came to the major organs of the body. For him, one of the most important principles in biology is what he calls vital heat. This isn't so crazy. After all, living animals tend to be warm and to cool down fast when they die. Relying on this idea, Aristotle believed that the heart's function was to spread vital heat through the body, and to serve as the centre of motion and sensation. For him, the brain was little more than a refrigeration device for regulating vital heat, and breathing in air plays the same kind of role, to balance out the heat generated in the heart. You might believe that you can tell you are thinking with your brain, and that it is just obvious that your thoughts and sensory experiences are, as it were, happening in your head, but this is clearly not true. Aristotle, and the Stoics after him, thought that the heart was the controlling organ of the body, the seat of motion and sensation. As for thinking, Aristotle denied that this is done with any bodily organ at all, as we'll discuss in a later episode. Just as vital to Aristotle's biology is the question of how new animals are formed. Here too, he was a keen observer, even keeping a careful record of the development of chicks by looking inside eggs at different stages of incubation. If you're curious about which came first, the chicken or the egg, I direct you to History of Animals Book 6 Chapter 3. The preservation of species is of tremendous importance for Aristotle, because he believes that when we are dividing up animals and understanding their functions, we are learning about eternal, necessary features of the world. The celestial bodies rotate around the earth eternally, but chickens, tortoises, and humans cannot live forever, as the celestial bodies do. They are not made of the indestructible fifth element that exists out there in the heavens. So the only way that species can be eternal is through reproduction. Thanks to reproduction and the permanence of species it makes possible, zoology is a fit subject for the Aristotelian scientist, who is interested only in necessary and eternal truths. This brings us to the third major zoological work, the generation of animals. As in parts of animals, Aristotle here deals with purposiveness. As it develops, a chick embryo is relentlessly pursuing its final cause, which is to be born as a chick which can grow into a mature chicken. But to explain the mechanics of reproduction, Aristotle has recourse to two other kinds of cause, form and matter. His basic idea is that the female human or animal provides the material for the fetus, namely menstrual fluid, while the male provides form through his seed. The seed contains certain motions which transmit the form to the blood and set up a chain of developments in the matter that lead to the formation of a fetus. Again, heat is the chief physical mechanism here. Human seed causes the matter to be heated in just the right way that the blood is concocted into a human embryo, and not the embryo of say, a giraffe. Mechanics aside, it's worth noticing how Aristotle here diverges from Plato. Forget the single transcendent form of man, a man is caused by nothing more or less exalted than another man, namely his father, in cooperation with the cosmos which provides the context in which nature unfolds. As Aristotle famously puts it, man is generated by man and the sun. Now I know what you're thinking. Things cannot be quite this simple. After all, humans resemble their parents and grandparents more than they resemble other members of the species. So the father must transmit more than the basic form of human or horse, he must also transmit say, the property of having a snub or aquiline nose. Furthermore, people also resemble their mothers. So the mother cannot, after all, be providing just a substrate of matter, with the male seed doing all of the work of transmitting form. Realizing this, Aristotle not only allows that the motions in the father's seed bring along the father's idiosyncratic features, but also admits that there must already be highly specific potentialities in the woman's menstrual fluid. These can emerge as the embryo is formed, so that you might inherit your mother's brown eyes despite having a blue-eyed father. Finally, Aristotle seems to allow for new features to arise in the child, to explain features that are apparently possessed by none of the child's immediate forebears. This raises the intriguing possibility that Aristotle could have allowed for the possibility of something like evolution. After all, if you can be blue-eyed when your parents have brown eyes, then why can't species themselves change from generation to generation? Make enough incremental changes across the generations, and you can turn apes into humans, as Darwin taught us. Aristotle clearly rejects this, but why? I suspect that Aristotle simply didn't consider it physically possible within the mechanics of reproduction for variations to arise that would lead to an actual change in species. To explain why, he might point to the cosmic cycle itself. If events here in our lower world are causally connected with the regular, eternal motions of the heavens, then it is no surprise that the events are always more or less the same. This in broad outline is Aristotle's account of how species are propagated. But there's a rather large exception we still haven't considered. Aristotle believed that some animals are generated without parents, that is, spontaneously generated. Usually, this is explained by referring to the appearance of maggots and worms in rotting flesh. Failing to notice any insects laying eggs in the flesh, Aristotle and others leapt to the conclusion that such creatures can generate spontaneously. That is part of the story, but Aristotle was also drawing an inference from his dissection work. He looked at a variety of species without finding any reproductive organs, and inferred that these species must arise spontaneously. This is the sort of mistake that can lead modern readers to regard Aristotle with amused condescension. But in a way, I think we should congratulate him on his intellectual honesty. Within his system, spontaneous generation is clearly a problem. It is a major exception to his theory that form is passed on to offspring by parents. So it's to his credit that he gave serious thought to an apparently unavoidable fact of observation, especially given the lowliness of many apparent products of spontaneous generation. Aristotle wasn't going to let a nice theory, or the fact that maggots are disgusting, distract him from his scientific integrity. Briefly, his account of spontaneous generation is that some external heat source, like the sun, does the work of setting off motions in suitably prepared matter, the work that would normally be done by generative seed. This happens when a bubble of warm liquid is somehow enclosed so that vital heat cannot escape, and an animal is more or less randomly formed. It's worth emphasizing that many types of animals are only generated in this fashion. This is surprising, given Aristotle's insistence against Empedocles in the physics, that natural things cannot be the result of chance and spontaneity, as we saw a few episodes back. In light of this, how can Aristotle say that there are eternal species that are propagated by chance? The solution, perhaps, is to say that the particular time and place of spontaneous generation is a matter of chance. This is a striking difference from normal generation, where animals and humans very intentionally set about the process of reproduction, perhaps after dinner and a movie. In the case of a spontaneously generated worm, it just so happens that the right kind of bubble is heated in the right way. But in another sense, this is anything but random. Whenever such a bubble is so heated, the result will be a worm, and it's entirely predictable that this will happen on a regular basis, even if we cannot predict where or when. Finally, we should admit a similar tension that arises frequently for Aristotle. He wants to say that nature does nothing in vain, that the world around us is full of form and purpose, yet we frequently see nature fail. Human and animal babies are born with deformities. Human whole species sometimes seem defective, as for instance, moles, which have underdeveloped eyes below their skin, a fact Aristotle observes and discusses with some interest. In general, Aristotle is not too concerned when nature falls short. Nature does nothing in vain, but it also acts only for the most part, and the fact that animals and plants are made of matter means that form can always be thwarted. We care more, of course, when humans are defective. On this point, Aristotle seems to depart from his usual optimism. He thinks the human race is in fact made up largely of defective types, including women and so-called natural slaves, but also plenty of free male citizens who are vicious when they should be virtuous, boorish when they should be pursuing the pleasures of knowledge. Aristotle needs to account for this, and tell us how to make sure we fall into the relatively small class of those humans who do fulfill their purpose. It is this task that he takes up in what may be his most enduring work, the Nicomachean Ethics, and in its sequel, The Politics. These are the texts we will be looking at in the next episodes of the podcast. But podcasts are also occasionally short of perfect, and the series is unfortunately now going to illustrate that point by going on hiatus for a few weeks. For the month of August I'm going to take a break so I can write more episodes, gearing up for the next year, which will finish off Aristotle, and then cover Hellenistic philosophy and one of my main areas of interest, Neoplatonism. I hope this break will provide an opportunity for listeners to catch up on episodes they haven't heard yet. Before I go, I'd like to thank my production assistant Rory O'Connell, who has done a wonderful job this year editing the episodes. I'm also grateful for audio advice from Andreas Lahmer and to Stefan Hagel for permission to use the music which begins and ends each podcast. Above all, of course, I'm grateful to you for listening, and I hope you'll make the right choice and listen again when I return on September 5th with Aristotle's Ethics, here on The History of Philosophy, with a break during August, but without any gaps.