 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.historyoffilosophy.net. Today's episode, The Philosopher's Toolkit, Aristotle's Logical Works. A few episodes back I asked you to imagine that you were a medieval monk, reading Plato's Timaeus. That was good practice for what I'd like you to do now. Imagine instead that you're a 5th century AD student of philosophy. You have come to the great centre of learning that is the city of Alexandria in Egypt. Don't forget to visit the lighthouse, I hear it's wonderful. You already have a good education under your belt, you are literate and have studied some rhetoric, and now you are going to try to master philosophy. What's the first thing you will study? Of course it will be Aristotle. As we'll see eventually, in the late ancient world, even Platonists introduced their students to philosophy through Aristotle, saving Plato's texts for more advanced research. But what Aristotle will you begin with? Nowadays, a course on Aristotle might start with his ethics or his physics. But, as a late ancient student, you will be taught that there is only one place to begin doing philosophy, logic. In fact, you will spend quite a while digesting Aristotle's logical works. Many students will never progress any further into more advanced topics. The designers of the late ancient curriculum were onto something when they prescribed a foundation in logic for their students. Logic deals with the rules of rational argument, and obviously philosophy is nothing if not a kind of rational argument. So, there is good reason to think that the study of logic is fundamental to the study of philosophy as a whole. But your late antique philosophy professor will also be teaching you that logic is not, strictly speaking, a part of philosophy. Only the foolish Stoics would call it that. As well-trained Aristotelians, you will be considering logic instead as an instrument for philosophy, a tool which is deployed in the various disciplines that really are parts of philosophy, like physics, ethics, and metaphysics. For this reason, you refer to Aristotle's works on logic collectively as the organon, a Greek word which means tool or instrument. In late antiquity, the organon was seen as including no fewer than eight works, namely categories, on interpretation, prior analytics, posterior analytics, topics, and, to top it off, the rhetoric and the poetics. Nowadays, we find it strange to think of the rhetoric or poetics as works on logic. They seem to have been tossed in for lack of anywhere better to place them in the Aristotelian system. So, for us, Aristotle's logical writings, still sometimes called the organon, would at most be the other six works. But thinking of all of these works as logical would mean taking a very broad view of logic. I already discussed the topics last time. It doesn't deal with logic as we understand it, but rather with the rules of dialectical debate, where premises are assumed for the sake of argument or because they are acceptable for some other reason. As for the Sophistical Refutations, you might guess from its title what goes on there. Aristotle uncovers the tricks and ambiguities used by the sophists to produce misleading arguments. This is, one might say, the study of anti-logic, the study of intentionally bad arguments, like the ones displayed in Plato's Euthydemus. That leaves us with four more logical works by Aristotle, the ones I will be discussing in this and the next episode. The Categories, On Interpretation, Prior Analytics, and Posterior Analytics. So, are these the works where he really discusses logic? Well, not really. It is only the prior analytics that deals with logic in something like our sense, by analyzing the forms of arguments separate from their content. For instance, it's in this work that Aristotle will discuss the fact that it is fine to argue from every A is B and every B is C to the conclusion every A is C. While you're working out whether that sounds right, I'll retrace my steps a bit and start where the late ancient philosophy classes did with the categories, not the prior analytics. So, what is the categories about? That turns out to be a difficult and much discussed question. Let's start with the title. It relates to the Greek verb katé goren, which means to blame or to accuse, but which Aristotle uses with the meaning to predicate, that is, to say one thing about another thing. So, on the face of it, it looks like the categories might be about things that can be said about or ascribed to other things. That's still a bit vague, but does seem to fit the content of this work reasonably well. What we get first is a few short chapters making points about words that are predicated, for instance the difference between synonyms and homonyms. The second chapter makes a fundamental distinction between two kinds of predicates, one of the most important distinctions in Aristotle, in fact. We'll be using it many times in podcasts to come. The distinction is between what is said of something and what is present in it. That's how Aristotle puts the point here, but the usual way of putting the contrast is to say that some features of things are essential and others accidental. A feature or predicate is said of something or essential to that thing if it has to do with the very nature of the thing in question. For instance, it is essential to a giraffe that it be a giraffe, that it be an animal, and that it have any other features that are required for membership in the exclusive club that is the species of giraffes. All other features are accidental, or present in, things. So, for instance, if the giraffe is painted blue, blueness is accidental to it or present in it. If the giraffe is a particularly fine example of its species, then its glossy coat and unusually erect posture will also be accidental to it, because it could get sick, lose the glossy coat and the good posture, but still be a giraffe. In fact, this is a test you can use to decide whether Aristotle would count a given feature or predicate as being essential or accidental. If you can change a feature of something without destroying that thing, then the feature must be accidental. After these preliminaries, the categories gets on to the thing that it is most famous for. It gives a list of ten so-called categories, which here means types of things that can be predicated. There are ten categories. If you know them, you can say it along with me. Ready? Substance, quality, quantity, relation, place, time, position, state, action, and being acted upon. So what exactly is this list listing? Well, maybe something like this. If you think about all the features that can be predicated of something, you'll see that they will fall into these ten types. Let's have an example, shall we? Consider our friend, the silent film comedian Buster Keaton. Firstly, he is a human. That's a predication in the category of substance, because it tells you what sort of thing he is. All his essential features will arise from his being this sort of substance, and the only way he can lose these essential features is to stop being a human, in other words to die, which I'm sad to report Buster Keaton did do in 1966. It was only then that he stopped being, for instance, alive, rational, embodied, and so on. These were the things that were essential to him. But Buster had lots of features that are not essential. For instance, his feet were big, and that's an accidental feature which falls under the category of quantity. He was silent, which falls under quality. He lived in California, which falls under place. He made films, that's the category of action, and in these films he got smacked in the face and thrown out of windows. That would be very much in the category of being acted on. This whole project of classifying predicates into 10 classes is not something Aristotle necessarily thought up on his own. Scholars believe that it originated in the context of Plato's Academy, where Aristotle studied for many years. You can imagine how this might have gone. They'd send a student to the front of the class, tell him to stop fidgeting, and everyone else would call out descriptive words, which would be divided up into 10 classes. They wanted to make sure that they had a category for every predicate they could think of. Obviously I'm pretty much making this up, except that we do know that the Academy was mad about classification and logical exercises of this sort. I can't resist mentioning here the famous anecdote about another philosopher, Diogenes the Cynic, who was going to make for a very entertaining podcast before too long. Upon hearing the Academy's definition of man as two-legged animal without feathers, Diogenes showed up with a plucked chicken and said, here is Plato's man. I'm tempted to make a joke of my own here, maybe something about this leaving Plato in a foul mood. But I think it would be better to go back to Aristotle's logical works. I will leave the categories for now, but return to it in a few episodes when I come to talk about Aristotle's metaphysics, because when he deals with the category of substance, Aristotle makes a number of points that bear on metaphysics. Indeed, even to some ancient readers it seemed problematic to pigeonhole the categories as dealing only with logic or language, since it does have this metaphysical content as well. Of course it's no surprise that Aristotle would make some metaphysical remarks while discussing substance, and in general he seems happy to make wide-ranging points about each of the categories. He says especially interesting things about the category of relation, and we may return to that subject somewhere down the line, for instance when we talk about the innovative theories of relation developed in medieval philosophy. For now, though, we've got two more logical works to cover. Next we'll tackle On Interpretation. Again, this does not quite seem to be a work on logic in our sense, rather it looks more like a contribution to the philosophy of language. You might remember that this is an area Plato explored in his dialogue The Cratylus, which considered whether words have significance by nature or convention. Aristotle flatly declares at the beginning of On Interpretation that the conventional answer is correct. Names are conventional symbols, and Aristotle says something interesting about what they symbolize. You might think that the sound Buster Keaton would simply represent Buster Keaton, and it does, but in the first instance Aristotle thinks it represents a thought in my soul. He says that there is a chain of representation in fact. If I write down a word, that represents the word as spoken, so that verbal language is more fundamental than written language. The spoken name in turn represents the thought, and it is the thought which represents the thing out in the world. All this is something else that will inspire some innovative philosophy in the medieval period. But Aristotle is only warming up to his main theme, which is the study of sentences that assert or deny something. For instance, I might assert that Buster Keaton is human, or deny that Buster Keaton is a giraffe. This is a point that does have clear relevance for logic, especially Aristotle's logic. His logic is sometimes called categorical, because he is always focusing on statements that relate a predicate to a subject. Remember, the verb kazugur-in means to predicate. He makes another distinction that will be crucial down the line, by making the point that some predications are universal and others are particular. So I could say all humans are alive, or I could say Buster Keaton is alive. Aristotle uses this distinction to look at the question of which sentences are directly opposed to which. He says that one statement is contradictory of another, if it is an exact negation of it, and as he points out, it's a matter of some subtlety to determine this. For instance, the contradictory of all humans are white is not all humans are not white, but rather some human is not white. The reason this is important and useful is that for every pair of contradictories, one and only one can be true. So in the example I just gave, either there is at least one non-white human, or all humans are white. It has to be one or the other. I know what you're thinking, what if there are no humans at all? I'll be dealing with that question in the next episode, so in the meantime I have to ask you to be patient and assume for the sake of argument that there are in fact humans. This point about contradictory statements leads Aristotle into the most famous part of On Interpretation. He's told us that for any pair of contradictory statements, one will be true and the other false. But this leads to a problem. What if the statements we're considering are about the future? To take Aristotle's example, what if I say, there will be a sea battle tomorrow? This has a contradictory, namely, there will not be a sea battle tomorrow. So according to Aristotle's rule, one of these is true and the other false. But here comes the problem. Suppose it's true that there will be a sea battle tomorrow. In that case worries Aristotle, it is already fixed or settled that the sea battle will occur. It looks like it is too late for anyone to do anything about it. The admirals may confer about strategy, consult the weather forecasts, and so on, all the while thinking it is not yet decided, but in fact it must already be inevitable that there will be a sea battle because the statement that there will be a sea battle is already true. Aristotle finds this troubling, warning that if the argument is right, there will be no point in deliberating about any course of action. The future is already written, as it were. Everything that happens, happens necessarily. Aristotle offers a solution to the problem, but unfortunately it's rather unclear what the solution is meant to be. On the most popular interpretation, he says that these statements about the future are in fact neither true nor false, so he makes an exception to his rule about contradictories in this one case. But there is reason to find that unsatisfying. If we're surveying the wrecked ships in the Thames estuary tomorrow, and you turn to me and say, see I told you there'd be a sea battle, it would be implausible for me to say, no, you weren't right because when you said that it wasn't true, at least not yet. That, at any rate, is the most famous part of On interpretation, and it clearly relates to what we think of as logic, but the core of Aristotle's logic is presented in the Prior Analytics. The ancient interpreters saw these texts I've been discussing as forming a sequence. The categories would talk about individual terms, the words that would fall into the ten categories. Then On interpretation talks about words put together into statements. Now, the Prior Analytics will talk about sentences put together into arguments. This story is too simple, especially when it comes to the categories, but it's true enough that the Prior Analytics studies conjunctions of sentences to form arguments. In particular, what it studies is the arguments Aristotle calls by the Greek word syllogismos. This, of course, is where we get our word syllogism. For Aristotle, a syllogism is an argument with two premises and a conclusion. Of course, there has to be one term which appears in both premises, since otherwise you can't conclude anything. So, a typical syllogism might go like this. All mammals are animals, some mammals are giraffes, therefore some animals are giraffes. When Aristotle tells us in the Prior Analytics that this kind of argument is successful, he doesn't just give an example, like I just did. Instead, he uses variables. For the argument I just gave, it will go like this. All a is b, some a is c, therefore some b is c. It's easy to underestimate the importance of this. For us, nothing could be more natural than using letters or symbols as variables when discussing the logical form of an argument. But someone had to invent this, and the someone who invented it was Aristotle. This deceptively simple little device is arguably what enabled Aristotle to invent logic, because it allowed him to consider various argument forms abstractly and to state very rigorously how one argument relates to another. That is just what he goes on to do in the Prior Analytics. But at first glance, he's only handling a rather small range of arguments. As I say, he only looks at these two premise arguments he calls syllogisms. And in fact, he only looks at syllogisms where one thing is being asserted or denied of another thing. So the types of premises he considers are all a is b, some a is b, no a is b, and some a is not b. Putting in examples instead of variables, then, all giraffes are animals, some giraffes are animals, no giraffes are animals, and some giraffes are not animals. Aristotle then exhaustively considers all the possible ways that such premises can be combined and proves that some will immediately produce a conclusion. These syllogisms he calls complete. Others need some argument to show that they do produce a conclusion, and still others are unproductive. Aristotle's meticulous discussion of these syllogisms is one of his greatest achievements. It set the stage for more than 2,000 years of logic, which would be done largely within the framework envisioned in the Prior Analytics. In fact, it was only with Gottlob Frege in the 19th century that logic finally departed from this Aristotelian paradigm. Amazingly, though, this isn't the only thing Aristotle tries to do in the Prior Analytics. For one thing, he's conscious of something I've mentioned, which is that he seems to be looking at a rather restricted range of argument types. So, he attempts to show that all productive arguments can be reduced to his syllogisms. He's actually not right about this, as will be pointed out by the Stoics, themselves great contributors to the history of logic. He also spends a good deal of the Prior Analytics discussing the fact that the premises and conclusion of an argument can be either possible or necessary. So, for instance, suppose I say giraffes are necessarily mammals, and all mammals nurse their young. Does that show me that giraffes necessarily nurse their young? Is the necessity transferred from the premises to the conclusion? This is an area where Aristotle's ideas about logic are rather different from the ideas that philosophers have today. For instance, he thought that if a statement is necessarily true, it must always be true, which seems fair enough. But he also thought that you can go the other way, that if something is always true, then it is necessarily true. This isn't nearly so obvious. For instance, I don't have a sister, and in the absence of some startling news from my parents, I am never going to have a sister. But is it necessarily true that I don't have a sister? It doesn't seem so. Next time, we'll be looking further at Aristotle's ideas about necessity as we examine what Aristotle had to say about knowledge. That will bring us from the Prior Analytics to its sequel, the predictably titled Posterior Analytics. There, we'll discover that, for Aristotle, our knowledge must concern things that are necessarily true, which means things that are always true. If you find this hard to believe, then the only logical conclusion is that you should join me again next week for Aristotle's epistemology, here on The History of Philosophy, without any gaps.