John Sellars on Aristotle, the Four Causes, and Nicomachean Ethics

John Sellars

No, absolutely not. He's an incredibly difficult thinker to get to grips with, but I think once you do, and you really get a sense of how his mind works, it's absolutely incredible. And that doesn't involve thinking that he's right about everything. I don't think you have to agree with Aristotle to think he's an incredible thinker. It's just the way that he analyses things, the way he makes decisions. He's very, very good at saying, look, it's just not as simple as that. We need to complicate this issue further. And I think that's a really valuable skill or trait for a philosopher.

The other thing he'll do that's really impressive is you'll see him make a first stab at an answer to a question, and then he'll give a second, slightly more refined answer to the same question, and then another. So there's a sense in which you can see him thinking through the problem. If you read him thinking, okay, this is a big systematic thinker, and you see these seemingly contradictory statements, you think, God, what's going on here, all these logical inconsistencies. But if you get into the rhythm of his thought process, you see him say, okay, here's a general statement, now let's refine it, now let's refine it. Once you get into the rhythm of how he thinks, it's really impressive.

Alex O'Connor

People will have heard of Aristotle, but especially if they're watching an introduction like this, they might not really know what he's all about. So in the fewest possible words to start with, what's the hype? What's so great about Aristotle?

John Sellars

Perhaps start with a very small bit of biography. Aristotle is a student of Plato. As a teenager he goes to Plato's Academy in Athens. He studies with Plato for twenty years, is effectively Plato's greatest and brightest student. So he's coming in that legacy: Socrates, Plato, Aristotle. He's drawing on all of those Platonic ideas, but then he's challenging them, questioning them, and moving them on to the next stage. That's one part of what he's doing, but he's also a natural scientist. In fact, I think the best way to think about Aristotle as a thinker is that first and foremost, he's a biologist.

He's interested in understanding the natural world, understanding organisms, including us, and how they operate. So you've got this combination of a very refined, complex metaphysics that he's inheriting from Plato, and this really down-to-earth, nitty-gritty, let's-understand-the-physical-world side. He's bringing both of those things together. At the same time, he's also interested in politics, in literature, and he invents formal logic. There's no one in history who has invented more academic disciplines than Aristotle. That's quite an achievement for anyone.

Alex O'Connor

Each of these areas — formal logic, his so-called metaphysics, his ethics — is a world unto itself. So the best thing is to take them one by one and start getting a feel for the kind of stuff Aristotle was thinking about. People often start with Aristotle with the ethics, but I always like to leave that till last. We spoke before about stoicism and did the same thing: everyone knows the stoics are people who hold fast in the face of suffering, but let's do the metaphysics first and then see why that's what comes out of it. So for Aristotle, the fundamental question might be: what is being? What is substance? What is the universe made out of? What is the foundational nature of reality? How can we start getting a feel for his picture of that?

Being and the paradox of change

John Sellars

To come back to something I was saying earlier, his first move is to say it's more complicated than anyone else has thought. The famous early metaphysician in Greek philosophy is a man called Parmenides, who's a big influence on Plato in many ways. Parmenides says, well, things either exist or they don't exist; there's no middle ground. And things can't suddenly come to be out of nothing — you can't have existing things suddenly appearing. Equally, you can't have things that exist vanishing into thin air; that doesn't happen either. So things either are or they are not. Ultimately Parmenides says everything just is, everything just exists. You can't have a non-existent thing. And if you just have existence and nothing can fall out of existence, you have permanent, eternal existence. Everything just is, all the time. This is all very armchair philosophy.

Plato inherits these ideas. Clearly Aristotle and Plato were talking about these things in the Academy when Aristotle was young. And he comes along and says, well, look, we need to complicate this, this is far too simplistic a way to think about existence. For instance, this chair exists; it's a thing. The brownness of the chair also exists. But the brownness doesn't exist on its own — you can't have brownness just like that, you can have a brown chair. So the brownness exists as an attribute of the chair. It exists in a different way to the way the chair exists. Suddenly we've got two ways of thinking about what is real.

And given that he's interested in organisms, biology and the natural world, the one defining characteristic of the natural world is change — everything's constantly in motion. This is something Parmenides denies: things just are, and they don't change. But no, everything's changing, everything's moving all the time. And if we look at physical processes and organisms, they give us really clear examples of this. The classic example would be the acorn. An acorn is an acorn, but it also is going to become an oak tree, or has the potential to become an oak tree. So there's a sense in which the acorn is two things at the same time. It is an acorn, and it is potentially an oak tree, in a way in which nothing else is potentially an oak tree.

Alex O'Connor

And that potentiality is part of what the acorn is. You wouldn't fully understand the nature of an acorn unless you understood its potentialities. Parmenides is quite hard to interpret, but he seems to deny the existence of change, because he says: stuff that is, is; stuff that is not, is not. For something to change would mean that something which is not would need to come into being — for there to be a tree that grows, there would need to be something like a tree that wasn't there before. That's something coming from nothing, and that doesn't make sense. So Parmenides brings up this paradox of change.

And Aristotle, in attempting to answer this concern, starts with this distinction. He says there are different ways in which something can be. For an acorn, it is an acorn, but it's also potentially a tree. You might think potentiality isn't really a thing, it doesn't exist. But the acorn isn't potentially a chicken — it doesn't have the potential to become a chicken, but it does have the potential to become a tree. So whatever that is, it's real, and it means something.

John Sellars

Absolutely. As you said, it's the defining characteristic of an acorn. You don't know what an acorn is unless you know it has the potential to do that. So that is really important. And this challenges the sorts of things Parmenides was saying, because the acorn is defined by what it is not at the moment, but what it can become.

The other thing going on here, if you think back to Plato: lots of people will have their caricature of Platonic metaphysics — there are ideal forms that are unchanging, and then the physical world is constantly changing and is just some kind of shadow of these really existing, unchanging things. So again, Plato's committed to the idea that the things that really exist are eternal and don't alter, and the things that change are somehow secondary and less important. Aristotle wants to challenge that and say, no, it's all this changing stuff that isn't fixed in its being — that's the interesting stuff. That's the world we live in. That's the world we want to understand.

Alex O'Connor

So Aristotle comes along and says, when we're talking about stuff that exists, there's potential and there's actual. Acorns are potentially a tree, and when it becomes a tree it's actually a tree, and it has the potential to decay. Okay — who cares? What does that mean? Why would someone bother thinking about that? An acorn potentially becomes a tree — who cares?

Against Democritus the atomist

John Sellars

It's just part of trying to understand the natural world. If you're trying to do science, you're going to want to understand how these processes work. But one really interesting thing to do in thinking about a philosopher is to ask who their enemies are. Who's the bad guy? And for Aristotle, I think the bad guy is Democritus, the atomist. Democritus is presenting what we would now call a kind of reductive materialism: everything can be reduced down to matter in motion.

Alex O'Connor

Democritus is one of our earliest, perhaps the earliest, thinkers who believed the universe is made out of small indivisible atoms. The word atom just means indivisible. It's unfortunate that we have since split the atom, but by atom we literally mean whatever the most indivisible small unit of stuff is. Democritus says the universe is made up of atoms, whatever their nature, and everything that exists can be explained in terms of those atoms — which sounds a lot like a modern materialist.

John Sellars

Absolutely. And you're all too aware of the sorts of problems that might raise if you're just talking about dead matter in motion. How is it that some things are alive? How does consciousness grow out of the interactions of these bits of dead matter? This is Aristotle's big concern — that describing the physical world in terms of that inert matter just isn't rich enough to explain the complexity and variety we see in the natural world, particularly in biological organisms. Think back to the acorn. If you're a reductive materialist, you break it up, you look at all the components, you see what it's made out of, and in theory that's your complete explanation of what it is. But that doesn't tell you anything about trees. So it's not really enough. It's only a partial explanation.

Alex O'Connor

A modern thinker might be quick to criticise Aristotle. They might say, well, if you actually knew everything about the molecular make-up of the acorn, and the make-up of the chemicals surrounding it, and of the sunlight, and put it all together, you would predict that a tree would come about. But a few things to consider: maybe it's not as simple as that, and also Aristotle is very early on here. He's one of our earliest people to think about this kind of stuff. So sometimes he misses things we now know to be true, but he's still undisputedly a genius for his time.

There's one interesting moment where Aristotle seems to prefigure evolutionary natural selection. He considers the possibility of essentially natural selection — he describes it, and then dismisses it, for reasons which, now we understand evolution, seem a bit too forthright. But the fact that it was even something considered by him is pretty astonishing. So I want to protect Aristotle's reputation against what might be called presentism, and realise that we're dealing with a mind here.

Forms — Plato versus Aristotle

Alex O'Connor

You've talked about how Aristotle was a student of Plato, and there are some really important ways in which he differs from him. You alluded to this concept of the forms in the context of change. Could you tell me a bit more about what Plato's idea of forms was, and how Aristotle thinks about things differently?

John Sellars

Precisely what Plato thinks about ideal forms is a vexed question. He says different things in different dialogues, but he seems committed to the idea that the really secure knowledge he's after can't be knowledge of something changeable. Because you think you know it, and then you go back to it a week later and it's different, so you don't really know it after all. There's a sense in which, for Plato, real knowledge looks like mathematics — eternal and unchanging. Two plus two always equals four. And so he thinks that if all our knowledge has to look like that, it's going to have to be knowledge of unchanging ideas.

So he thinks that as we look at objects in the physical world — as we look at chairs, for instance — we ought not to be so concerned about the particular chair in front of us, which is going to change and decay and not be there forever. Instead we want to get to the idea of chair in itself. We want to move from the particular chairs we see to the idea of chairness. And he thinks that idea of chairness, if it's unchanging, must have always existed. Then there's all the weird and wonderful stuff about whether there was a past life when we encountered these ideas directly before our birth.

Alex O'Connor

So the question is: you've got a chair over there, I've got a chair over here, and there's a table in between. There's something these two chairs have in common that they both don't have in common with the table, which is why we call these chairs and that a table. They're not the same object — yours is over there, mine's over here — but they've got something that connects them and makes them both fall into this category of chair. For Plato, there is this thing called chairness which both of them participate in. And our knowledge of what a chair is must be because we had some prior understanding before our birth. He entertains the idea that we were existing in the realm of forms, which is a little bit wacky and weird. But it's a real problem, because otherwise we've just got a bunch of matter arranged in various ways — I could call it a chair, but I could also use it as a table. To say there's a real thing these have in common that the lampshade doesn't means there must be this form of chairness that they all participate in. Aristotle is aware of this problem, but he doesn't agree with Plato's solution.

John Sellars

Let me give a more sensible and sympathetic account of what Plato is doing. As I say, he says different things in different places, so he's quite difficult to pin down. Another way to describe what Plato is saying is: look, for you to be able to go into the world and recognise a chair, you must already have the idea of chair in your head in some sense. So he's effectively saying there are certain ideas and concepts we must know a priori — we must know them before we go out and experience the world. They're not things we concoct off the back of experience. They must be there already. For your viewers who are deep into their philosophy, he's Kant, not Hume — that would be a way of describing where Plato is on this. A priori concepts must be in place already. And then there are the weird and wonderful stories about whether we encountered those a priori concepts in a past life, which obviously doesn't go that far.

What Aristotle wants to do is bring that idea of form down to earth. To use the mundane example of the chair again, Aristotle is going to say, yes, the chair has a form, and the form is simply the structure and organisation of the matter that makes it up. The chairs do share something in common, and it's the way the matter is structured and organised. But as soon as you destroy all the chairs in the world, there is no form left. So the form is dependent on the particular things that exist, rather than being some eternal idea that exists independently.

Alex O'Connor

So for Plato, the form exists and the objects exist as reflections of the form. Whereas for Aristotle, the individual objects exist and the form comes out of those individual objects. He flips it on its head and says the metaphysical starting point is the objects in the world, from which we get forms, rather than the other way round.

Hylomorphism — matter and form

Alex O'Connor

So for Aristotle, form is some kind of structure or arrangement of a set of matter. He's got matter and he's got form. And these two being put together gives us this concept of hylomorphism. I think hylo must mean something like matter, and morphe meaning form. So you get hylomorphism — the idea that what an object is, is a mixture of matter and form. And if you're familiar with scholastic philosophy, you'll begin to see the influence of this kind of thinking on people like Thomas Aquinas, who felt the same thing. Aristotle is such a titan of philosophy that if you read Aquinas, he just refers to him as "the philosopher". That's Aristotle's name in Aquinas's work, because he was just that significant.

So we've got an idea of Aristotle's metaphysics: hylomorphism, matter and form, a rejection of Plato, a rejection of Democritus. But there's one more missing piece before we can talk about the implications of this worldview, which is that Aristotle has some pretty specific views on the nature of causation. We've talked about objects that exist and the form in which they exist, but there are also reasons why things exist. An acorn doesn't just exist for no reason. In the modern age, if I ask you to explain something's cause — if I say, what was the cause of this chair? — you might say, well, it was whoever made it, or the factory. Aristotle wouldn't answer it quite in that way, would he?

The four causes

John Sellars

No. Famously, Aristotle is credited with a theory often referred to as the four causes. Although in this context, "cause" is perhaps a slightly misleading translation. A better way to put it would be four explanations — or better still, to say an explanation must have four different components. One of those components is what we mean by causation: who made this come about? In Aristotle, we call that the efficient cause, or explanation. Then we've got the form and the matter we've just mentioned. If you want to understand the chair, you've got to know what it's made out of, its shape and structure, and who made it. And then the fourth one you've got to know in order to understand the chair is: what's it for? What's its purpose? What's its goal? The teleology, the telos. To know the difference between the table and the chair, you need to know what they're for, what function they have. And that, he thinks, is equally vital to really understand anything.

Alex O'Connor

It's a common question in philosophy to ask, well, if I sat on that table, would it just become a chair? A sensible way to answer that is to say, well, what's its actual purpose? What was it made for? That's the only real way we can meaningfully distinguish between the table and the chair. Maybe they're both made out of wood, they've both got legs, they've both got a flat surface on top. What's the difference between a table and a stool? It's what purpose it was made with.

And yet today, if you were to say things need explaining in terms of teleology, in terms of what they're for, people are a little bit allergic to it. Aristotle is aware that people think about this differently. We understand a table is made with a purpose, but what about things that aren't man-made? We've talked about chairs and tables, and it's easy to see how this applies. But what about a tree? When you look at a tree, you might say, okay, it's got a material cause — it's made out of bark, made out of wood — and it's got a form, the form of a tree. It's got an efficient cause, which is the rain and the soil enacting the change. But what's a tree for? People would say that's a meaningless question. What would Aristotle say?

John Sellars

In the case of the tree, the organism as a whole, it's trying to stay alive, it's trying to reproduce. This is what living things do. So there's a sense in which that's their function. But what he's particularly interested in when thinking about these purposes or functions is parts of organisms in particular. If we think about a human being — what's your liver for? What are your kidneys for? What's your heart for? We can answer those questions. They have very specific purposes. They play a role in the functioning of the organism as a whole. So those look like quite simple examples of things in the natural world, not man-made, where we can point to these functions and purposes.

Teleology, function and evolution

Alex O'Connor

It's interesting how, if you read a high-school biology textbook, you'll find Aristotelian language sneaking in. If you look up on Google, why do we have a heart? — it won't say something like "because of this evolutionary trajectory and this arrangement of atoms which contingently..." It'll say: to pump blood around the body. That's why you have a heart, which is an extremely teleological answer. Why do birds make nests? Why do trees have leaves? Oh, in order to photosynthesise. In the modern day we don't like the idea that teleology is built into nature so much — we're typically suspicious of it — but the language remains.

I think it's because people want to say something like: it's kind of true that the heart exists to pump blood, but really that's shorthand for saying that an organism which pumps blood around the body is more likely to survive if it has a heart, and therefore hearts evolve in that creature. It's not really that the heart ontologically is for pumping blood. So do you think a modern understanding of evolutionary biology undermines the teleological causation of Aristotle?

John Sellars

That's a really good question. I would say, yes, the heart is for pumping blood. That's literally what it's for. Back to the acorn — you're not going to understand what a heart is unless you grasp the idea that it is for pumping blood. But then the big question is: does that imply that it was designed to pump blood? Can we reconcile what Aristotle was saying with, say, Darwinism? I think we can. If you think about what Darwin was trying to do — and this isn't my area of expertise — what Darwin's trying to do is offer an explanation for how these purposes and functions come about. Darwin can see that the heart looks as if it was designed and has a very clear purpose. And so his question is: how on earth could that have happened without reference to some kind of grand designer who constructed all of this? His explanation shows how it is that this object with a clear function came about over an incredibly long process that involved all sorts of chance and contingency along the way — but the end result is something very much with a function and a purpose. So in a sense Darwin would acknowledge that, I think.

Alex O'Connor

It's helpful to think about it this way: when you ask a question like "what is it for?", instantly you're conjuring up ideas of a creator, a god who makes it all happen for a particular reason. It's helpful to use the word "function" — it's much more secular. We're not saying this is what a heart should do. We're not saying it's written into the rules of the universe that there should be this thing called a heart with this purpose. It's just, as a matter of fact, what its function is. What does it do? Not just what it is, not just what it's made out of and how it got there, but what does it do? That's not a supernatural question. It pumps blood around the body. And that's what we're talking about with this fourth level of explanation, which still has a place in our modern metaphysics but is often understated.

John Sellars

But it depends on the context. If you go into a science lab and ask somebody why that rocket is on its way to the International Space Station, they'll say, well, because the thrust outweighs gravity and gives it escape velocity, and so on. But if you ask that same person at the pub, they'll say, because we want to get up there and do some science. And both of those can be true at once. The whole point of Aristotle's distinction is to say these are different aspects, different ways of answering the question: how do you explain the existence of this thing?

Alex O'Connor

So we've got a basic grasp of how Aristotle is thinking about the world. One of the most profound metaphysical questions somebody can ask is about the nature and causes of the universe itself. Did Aristotle believe in God?

God and the unmoved mover

John Sellars

The short answer is yes, he did. Precisely what he means by that term is slightly harder to pin down. He thinks the world is eternal, that it's always existed. So he doesn't think it was created at any point. In the early Christian reception of Aristotle this is a sticking point they have to fudge. He thinks the world has always existed; it wasn't created at any point. But nevertheless, he thinks there must be some kind of — the phrase he uses is "unmoved mover" — some kind of first cause, in the sense of something that ties up our explanations.

Alex O'Connor

Not a first cause in the sense of the big bang, a chronological first.

John Sellars

Exactly, not a first cause in that sense, but something that is the ultimate origin of movement and activity in the world, so that we don't have an infinite regress in our explanations, because he wants to avoid that. So he thinks there must be some kind of eternally existing unmoved mover that is the source of all the motion in the universe. And that's what he wants to call God.

This connects with things he has to say about the heavens. He said, okay, we want some eternal movement, movement that doesn't stop. Well, movement in a straight line is no good, because it has a start point and an end point. So what movement can go on and on forever? Movement going around in a circle. And can we think of any objects that move around in circles that have always been there and will always be there? He looks up at the night sky and says, well, look, there are all these things up there going round and round and round, and they don't seem ever to stop, and they seem to have been there forever. So perhaps these are divine bodies in some sense, underpinning everything else. But it gets very murky beyond there.

Alex O'Connor

It's quite different from a modern conception of God. Aristotle's views on the nature of whatever God might be are extremely different from something like modern Christianity, and yet, thanks especially to Aquinas, Aristotle is seen as one of the most influential Christian thinkers. Even pre-Christianity, he was laying a seed.

You said Aristotle believes in an unmoved mover. My understanding is that by "motion" in this context we're talking about change — not just what's called locomotion, movement through space, but anything which goes from one state to another. That's how Aquinas would use this term to prove God's existence, and it was based on Aristotle. And we know that change — when something like an acorn becomes a tree — would be characterised by Aristotle as the actualisation of a potential. You've got some potential thing which is not currently actual but is really there potentially, and then it gets actualised and becomes actual.

And there's a regress here, focused on by Aquinas later: in order to actualise something, there needs to be something already actual. If I want to cool down a can of Coca-Cola and I put it in a fridge, if my fridge is only potentially cold but not actually cold, it's not going to be able to actualise the potential of the can to become cold. The fridge has to be actually cold in order to actualise that change. But then, if the fridge is actually cold, something must have actualised that potential, and whatever actualised that must have been actualised by something else. And you end up with this regress.

Crucially, this isn't the kind of regress that goes backwards in time, like dominoes falling over, but: what is actualising potential right now? The potential of the cup to be in its position right now, as opposed to on the floor, is being actualised by the table, which is being actualised by the table legs, and so on. And the idea is that if this went on infinitely, there would be no ultimate actualisation. So there needs to be a so-called unactualised actualiser, or unmoved mover. The problem is, when you try to talk about this, you use the word "actuality" and "actualising" so much that you get completely lost in the weeds. But hopefully people can roughly follow that we're talking about some kind of first element in the causal chain which itself has no potential — because if it has some potential, you've got to explain why this is actualised and not that, and the regress continues. It has to be purely actual and have the power to actualise everything else. So we end up with this unactualised actualiser, the unmoved mover. Aquinas leans on that heavily to say that first unmoved mover is God. But for Aristotle it doesn't get you that far, does it? We're not talking about an omnipotent, omniscient, loving creator of the universe, just some kind of divine causal principle.

John Sellars

Yes. In so far as this unactualised actualiser interacts with the world, with us, or cares about human affairs, Aristotle has quite different views from the modern Christian. It's something impersonal, something that certainly isn't intervening in any way, that isn't particularly interested in particulars. This is where we see the Platonic influence still: Aristotle's God is going to be thinking about universal ideas and forms rather than particulars. It's going to be contemplating very general bits of knowledge. It's not going to be interested in the day-to-day activities of the physical world, and certainly not in anything we're doing. So it's a very disinterested and abstract type of deity. The fact that the Christian tradition was able to incorporate this with all the crazy things you find in the Old Testament, and find a way for it all to sit together, is quite an achievement.

The rediscovery of Aristotle and the Church

Alex O'Connor

Aristotle has an interesting history after his death. His works are neglected for some time and then rediscovered. Can you tell me about that story, particularly the Church's reception of Aristotle's work when it's rediscovered?

John Sellars

In late antiquity his works are translated into Syriac and then Arabic. Their first wave of influence is in the east, in places like Baghdad, and we see Islamic philosophers really interested in Aristotelian ideas and running with them. A little later, around the twelfth century, we see some of Aristotle's works translated into Latin, some of them from those Arabic versions. Spain is particularly important — Al-Andalus, where you've got a lot of Arabic scholars, and people from Western and Northern Europe going to Spain, learning Arabic, and translating texts. People also access some texts from Greek, from Byzantium, and translate those into Latin.

When that all happens, and people first encounter the full range of Aristotle's ideas, the Church is deeply worried. Here's this man who says the soul dies with the body, among many other things, who denies miracles, who says the universe is eternal and wasn't created. So on the face of it, Aristotle was saying a number of quite heretical things. You get a group of Aristotelian philosophers who are very radical, almost atheists, in Paris, and they're condemned. The Bishop of Paris says, no, don't teach this stuff, this is dangerous. And it's then the next generation of philosophers in Paris, which includes Thomas Aquinas, who want to rescue Aristotle. They can see he's a genius thinker, and they don't want him condemned as a heretic. So they find a way to create this marriage where they can bring the two together. It's not an easy marriage to start off with. It takes some time, some work, someone of the stature of Thomas Aquinas to pull it off.

The soul — psyche as the form of a living body

Alex O'Connor

People can begin to see how, while there's lots of resonance, Aristotle is laying some seeds that had to then be actualised by Aquinas. But there's also a lot to like in Aristotle when it comes to modern theistic thinking, and one of those is trying to account, in a world full of organisms, plants and animals, for the uniqueness and specialness of humans. Aristotle is fascinated by biology, and he knows that what a thing is — hylomorphism from earlier — is its matter and its form. If you take the right matter and put it in the right form, it gives you a thing.

But Aristotle writes quite plainly about a corpse. He thinks about a human corpse, someone who's dead, and thinks: it's got all the matter that a human does, and it's all arranged in the right way. The heart's in the right place, the blood is there, but it's dead. There's something missing, something which makes it alive. And when something is alive, there's something that makes it human as opposed to a dog or a plant. So can you tell me about Aristotle's taxonomy, and how he accounts for what a human is and what makes them special?

John Sellars

Earlier, talking about hylomorphism, we said form is the structure and organisation of the matter. And as the corpse example nicely illustrates, that's clearly not enough when we're thinking about living beings. It's not just the way the matter is organised; there's something else that's really vital — literally vital — to give us a proper understanding of what's going on. And the way Aristotle cashes this out is that we also need to think about what things can do. We need to think about their capacities, their potentialities. He uses the word "potential" in two different senses. One sense is: the acorn has a potential to become the oak tree, the warm can of Coke has the potential to become cold. That's a change an object goes through. But there's another sense of potential, which is using an ability or capacity that you have. We both have the capacity to talk; sometimes we use it and sometimes we don't. That doesn't involve any change on our part. We're still the same person, but in one case we're actualising the potential to speak, and in the other we're not.

So then he'll want to define human beings in particular, but also other living beings, as the sorts of things that have certain abilities and capacities, and that becomes part of his definition of what the form is. So the form of a human being isn't just two arms, two legs. It's the ability to speak, to move, to reproduce, but most importantly of all in the case of humans, the ability to think. That's the capacity we have that no other animals do. So it becomes our defining characteristic.

Alex O'Connor

This is where the earlier fourfold causation becomes relevant. Aristotle thought that to understand something you have to know what it's for. So when you look at real cases like this, if you don't have that element, trying to account for the difference between a corpse and a living human being becomes quite difficult. When you start reaching for words, you'll want to say something like, well, one of them is doing stuff — its heart is pumping blood, its brain is firing neurons. You're talking about what it's doing, about functions, about what everything is for, what end it's serving, and that's what produces life. So, matter and form, but form includes what a thing does, what it's for.

Aristotle uses the Greek word psyche, typically translated in the West as "soul". I don't know if you think that's an appropriate or unfortunate translation, but can you tell us how people talk about the soul when it comes to Aristotle?

John Sellars

Of course, the English word "soul" has all sorts of resonances that might make people think we're talking about something immortal, so that's a bit unhelpful — we need to bracket that. And "psyche" in English has all sorts of connotations too, so it's always a problem. But let's stick with the word "soul". The key point to remember is that "soul" simply refers to what it is that makes something alive — what distinguishes the living, breathing human being from the corpse. Soul is that thing. That's how Aristotle uses the term. That's not to say some soul has departed from the corpse, as if it's lost a component. It's just that the corpse has lost its capacities. In the case of a human being, soul — the thing that describes how we're alive — is really a case of just describing those capacities and abilities we have.

Alex O'Connor

It's like if you have a tower that you knock over. Its capacities as a tower, the form that makes it a tower, are now gone. You could call that the soul — the soul of the tower is whatever makes it into a tower, its form, its capacities. If I knock over the tower, the soul has gone, but it's not like it's floated off somewhere into an afterlife. It's just no longer functionally there.

John Sellars

And Aristotle is going to say that plants and animals have souls too, because they're living things. A plant can be alive or dead, so a plant has soul — it has some animating power, which is simply to be alive. Plants can reproduce in their own way. Animals also have the ability to move and perceive, so they have additional capacities; they're more complex. And then human beings have those two layers, but they also have this ability to think, so they're more complex again. As you go up the scale of nature, you get more and more capacities. And this is what Aristotle means by soul. He's not talking about a ghost in the machine. He's not talking about something that continues to exist after you die. He's just talking about the form of a living thing — its organisation, and also its functions and capacities, what it can do. A plant can do one set of things, animals can do that set plus more, like locomotion, and humans can do all of that plus think. And that's all Aristotle means by the soul.

Alex O'Connor

People might be put off. They might think, oh, Aristotle believes in the soul. I often find people are surprised to learn that's what he means by soul. And of course he didn't use the English word soul; he meant something more specific. So, not very supernatural here — we're just talking about matter and form. And the thing that makes humans special is their ability to reason. Now some might say, but surely this is a gradation — I've seen chimpanzees that can tap on a screen and follow numbers. Aren't they using reason as well? Is Aristotle justified in saying humans are a particular form as opposed to every other animal?

John Sellars

When Aristotle describes human beings as rational, he uses the word logos — rational comes from the Greek word logos, meaning "word" or "explanation". So humans are distinct in so far as they speak. They don't just think, they also speak. You might think your dog can think and is actually very clever, but your cat's probably cleverer. But humans speak. And you might say, okay, well, other animals like dolphins communicate — communication isn't unique to human beings. But the sense of logos we've got at play here is not simply "communicate", it's also "explain". Human beings are the only animals that try to explain the world they live in. We're the only ones that do science, and that's unique to human beings. So when Aristotle talks about rationality, he's not just talking about basic thought processes we could attribute to lower animals. Talk about the logos: he's talking about the fact that we can think and reflect about the world we live in and try to explain it. That's distinctive.

Alex O'Connor

And that's what makes humans special. And again you can see how this might be relevant to Christianity when you consider the importance of the logos — people might have encountered that Greek term in the context of Christianity, in that the logos is translated as "the word". In the prologue to John's gospel, "in the beginning was the word", and that word is logos. It's the same word being used by Aristotle to describe reason here. So some overlaps beginning to form.

Formal logic and the syllogism

Alex O'Connor

So we've got hylomorphism, the four causes, and Aristotle's view on the soul, which is actually pretty empirical and materialistic. That gives us a metaphysical picture. One thing we haven't mentioned, which people often start with because it seems a bit more meta, is something you alluded to earlier: Aristotle invents formal logic. He's this great scientist and biologist, and now a metaphysician and pre-Christian thinker, but at the same time he doesn't just want to think about propositions. He doesn't just want to think about true facts like "grass is green" and "animals have limbs". He wants to think about how facts relate to each other and combine to produce arguments, to produce new knowledge. Today in philosophy we use arguments all the time — we try to learn things by saying, well, if this is true and this is also true, then we can conclude that this is true. And funny as it might seem, this isn't really something that massively existed before Aristotle.

John Sellars

That's true. We see some arguments set out in the very early Greek texts, and lots of arguments in Plato's dialogues where Socrates is arguing with people, but there's no real formal account. You see Socrates make an argument in the dialogue, and you think, yeah, that works, or, that doesn't work — but how do you know? You're just going with intuitions. What Aristotle wants to do is formalise all of that, so we can really see when a conclusion follows deductively from the premises. When do we know we've got a necessary truth? So he wants to abstract all the distracting detail from the arguments we're making and just look at their structure, so we can see whether the conclusion follows from the premises.

The famous example is the syllogistic arguments he codifies for the first time: all As are B, all Bs are C, therefore all As are C. If you slot in facts in the first two that are correct, the conclusion is going to be correct necessarily, and there's no getting around that. And if you can string some of those arguments together into a longer piece of reasoning, you can start to come up with really quite complex pieces of knowledge. Again, famously in Plato's dialogues, Socrates is arguing with all these people we usually call sophists, presented by Plato as trying to pull the wool over people's eyes. We're all familiar with sophistry today. Aristotle really wants to say: okay, I'm going to give you the tools so you can uncover that when you encounter it, and see whether someone is giving you a good argument or not.

Alex O'Connor

To be clear, if you have an argument of that form — all As are B, all Bs are C, therefore all As are C — you could say that argument is valid. That follows from the premises. But there's no content there. It's like algebra, but for argumentation. There's no content; we're just talking about the overall structure. And Aristotle comes up with a bunch of different forms of argument, in the form of As and Bs and ifs and alls and nones, and lists out a bunch of different valid syllogisms where, if you plug in the facts, you'll know what the conclusion is. That's a pretty significant contribution to philosophy. But it's incomplete — our conception of formal logic today is not purely Aristotelian, but it's a starting point.

John Sellars

Absolutely. It's a huge achievement. If he'd just done that and nothing else, he would be a really important philosopher. But to have done that and done all the work in biology we're talking about — effectively inventing biology as a discipline in the process — not to mention all the other things, it becomes unbelievably impressive.

The lagoon — Aristotle the biologist

Alex O'Connor

I'm hoping people can begin to see that when you introduce Aristotle, and I ask you what all the hype is, it depends what you're talking about, because he's invented logic, which is totally separate from being probably the pre-eminent biologist of his era. His study of animals — didn't he live near a lake and go down and spend his time dissecting the fish, when no one else was doing that at the time?

John Sellars

Yes. After he left Plato's Academy, he spent some time on the island of Lesbos. I've never been, but apparently in the centre of the island there's a huge lagoon, a huge body of water. And Aristotle spent a couple of years there dissecting fish on the shore of this lagoon. And again, we're back to the four causes. You open up a fish, you pick out all the different bits and pieces, and I can see what this is made of, I can see what shape it is. But if I don't know what it's for, I have no idea what this is. Is this an eyeball? Is this a liver? I need to know what function they have in order to understand how this organism works. So that's where the hands-on empirical science of dissecting fish is where many of these ideas were first crystallised.

Alex O'Connor

I find it so interesting, the different ways of interpreting what it means to say what something is for. What is an eye for? To see. And it feels like you could almost trick people in the context of philosophy. If you speak to a modern atheistic materialist and say, does the eye have a purpose? — they want to say, oh, no, not really, it just exists and has the appearance of purpose. But if, without priming them, you went up and said, can you tell me what an eye is? — oh, it's the organ you use to see. What I want to say is: people might think Aristotle is antiquated, because he's holding on to this teleological nature that's been gone since evolution. But I want to say that evolution doesn't do away with this concept of function. It might do away with the idea of built-in teleology by design, but I don't think it does away with the idea that it's meaningful to say the function of a biological part is part of what makes it what it is. We really can retain that, if we just use plain language about it. The table has a function to hold things up, and that was invented by humans. The eye has the function of seeing, and that was developed by natural selection. One is designed, one's not, but they both have a function in a meaningful sense.

The ethics — the function argument

Alex O'Connor

So having said that, I want to ask you what the function of a human being is. And what I mean is, I want to wrap up — though it's probably the biggest subject of Aristotle's that's most popularly discussed — his ethics. We've got an idea of what he thought about the world, but he's also famous for his Nicomachean ethics about what makes a good life. And in many ways his idea about what makes a good life and what humans should do is not about divine command or ontological rules built into the universe, but again this question we keep coming back to: what are humans for? What is their function?

John Sellars

Absolutely. And I think you've been right for us to discuss it in the order we have, because you need to understand the biology first before you can understand what's going on in the ethics. Famously, at the very beginning of the Nicomachean ethics, he gives what we often call a function argument. You want to understand what a good human being is — first you've got to understand what a human being in general is, what it's for, and then what its function is. And once you understand that, a good human being will be one that fulfils that function. So if the defining characteristic of a human being is rationality, a good human being is going to be one that is rational and exercises those capacities.

Aristotle thinks there are two different ways in which we can engage in rational activity, two ways in which we can be good human beings, and these relate to two different types of virtue he describes in the book. The first set we might call — traditionally they're called moral virtues, but we might call them character virtues. These are primarily concerned with managing our desires and appetites. We're animals, biological creatures. We're animals with rationality added; we don't lose our animality just because we're rational beings. So we have all those desires and appetites any other animal would have. We're all motivated by pleasure and the fear of pain. This is the human condition. And so Aristotle says, well, one way we can be rational is to develop the right kind of character traits to control those desires and appetites. We have this inbuilt desire for food — there are good evolutionary reasons why we always want food — but we don't want to let that run out of control, so we want to develop the virtue of moderation, where we can keep a check on those appetites. That's one way we can live a rational life.

Another example would be courage. Again, there are good evolutionary reasons to run away from dangerous situations — very sensible. But there are some situations where it might be important to face danger and step in, for a variety of reasons. So we want to develop the virtue of courage, so we can use our reason to manage that sensible inbuilt cowardice we all have. So those are ways we can be rational by managing the non-rational elements of ourselves. A second way we can be rational — and this comes back to what we were saying about explanation and doing science — is what Aristotle calls intellectual virtues. This would be trying to understand the world we're in, to contemplate the universe, to do biology, to think about God, to do philosophy and metaphysics, the things we've been talking about. So that's another way we can be rational.

So a good human being — and this is the key, most complex question in Aristotle's ethics, which I don't think is resolved at all — is which of these, if any, is the most important? Do we have to choose between the two? The obvious thing to me seems to be that the ideal human being is going to be rational in both senses: you're going to have those virtues of moderation and courage, and also engage in that reflective activity. But the way Aristotle phrases it at the end of his book on ethics is to describe this in terms of two different ways of life. He talks about a political life — someone engaged in their community, who has those virtues, who is a good social animal. And he also talks about a contemplative life — someone just engaged in this theoretical reflection. You can see how that might connect with monastic ideas in the later Christian tradition: the person who isn't involved in society because they're engaged in intellectual pursuits. So he presents it almost as if there's a choice between these two ways of life you could live. They're both rational, both praiseworthy. But how do you want to live your life? What do you want to do? And I think philosophy often has an autobiographical element, and in this instance it's clear to me the life Aristotle wanted to live: to be engaged in that kind of contemplation and reflection, the life he did live, doing science and thinking about these big questions.

Happiness, flourishing and the good life

Alex O'Connor

Firstly, as a point of interest, people might wonder why it's called the Nicomachean ethics.

John Sellars

That's a good question, and shrouded in mystery. There's another book called the Eudemian ethics. It may be that those books were originally addressed to those people; it may be that they were edited by people with those names. In both cases we've got a pile of lecture notes. In fact, some of the books that make up these two works overlap, so it almost looks like one is an expanded version of the other. So it may be that these were the names of different editors. Aristotle had a son called Nicomachus, so it's conceivable his son put all these lecture notes together after his death. But we don't know for sure.

Alex O'Connor

So we're talking about the function of a human being, and it's the employment of rationality. But people might be confused, thinking, well, no, I studied Aristotle at school or university, and I remember them talking about happiness, and I thought that for Aristotle the ultimate aim of ethics, or of human life, was this happiness people talk about.

John Sellars

Yes. Happiness not in the sense of a subjective feeling of being happy, in the way we use the English word, but happiness in the sense of having lived a good life. Something a bit more objective, more substantial, something other people can say about you. Another term people sometimes prefer to translate it as is "flourishing", as opposed to happiness, which might better capture the kind of thing we're driving at.

Alex O'Connor

And in a very famous English translation, sometimes it's just translated as "a good life".

John Sellars

That's right. That's what we're after. So how do you live a good life? Be a good human being. Engage in rational activity. So happiness isn't about feeling good inside only. It's about actualising your potential for being a good rational being. And that's what happiness looks like. And as it happens, he thinks that if you do that, you will feel happy. That feeling of happiness, the feeling of pleasure — these will be the consequences, the by-products, of fulfilling your potential as a rational animal.

Alex O'Connor

How does that come out in practice? Different ethical theories about how to live lead to quite different practical outcomes — how you spend your time and so on. How much does Aristotle get into the practical here — here are things to do with your life, here are things to believe, here are ways to behave? Does he get that specific?

John Sellars

Yes, absolutely. I mentioned the idea of a choice between two different lives: do you want to become the research scientist or the monk, or do you want to be actively engaged in the politics of your community? He presents that as one choice about how you might live. But he also gets really into the nitty-gritty of everyday human life. One example: he has quite a lot to say about friendship. He thinks friendship and our social relationships are really important — not just friendship in the way we use the word, he's also thinking about romantic partners and family relationships. He thinks these are absolutely fundamental. So he goes into a lot of detail analysing this in a psychologically perceptive and astute way.

Friendship

Alex O'Connor

What does he think about friendship? I've heard he's got very interesting and broad views. What does he actually say?

John Sellars

For instance, he draws a distinction between genuine friends and what he calls friendships of utility. We have relationships with some people which are really just give-and-take relationships, and there's nothing wrong with that. Relationships where you meet someone in a shop — you're there for a reason, you want something from them, they want something from you. You want it to be a good, friendly interaction, but it's just a transaction; there's nothing deeper to it. And then there are real friendships, where you can really rely on the other person, and it's grounded on care and concern. You're not trying to get anything out of that person.

Again, this is Aristotle the scientist: I'm going to analyse human behaviour, human relationships, see how they differ, and classify them. And this is a useful thing to know, because you might think someone is a true friend and you can rely on them, and they might think you're just a friend of utility, and it's just about exchange back and forth. You need to have a sense of what relationships you're in and where you stand, and you can only do that if you've made these classifications.

Virtue ethics and the golden mean

Alex O'Connor

Another thing Aristotle is known for in the context of ethics is what's come to be known as virtue ethics. Typically, if you're a student of philosophy, you learn there are different ways of thinking about ethics. You could be a consequentialist, caring about the consequences of an action, like utilitarianism. Or a deontologist, who thinks there are rules to follow, like divine command theory. And then there's this third option in the middle, virtue ethics, which is about what the virtuous person would do. What does that mean? What is virtue? What is a virtuous person, and how does it connect to what we've spoken about?

John Sellars

Virtue ethics is focused on developing these character traits — courage, moderation, justice, and a range of others he discusses; generosity would be another example. The thought is: if you want to live a good life, don't think of it as a set of rules you have to follow, ten commandments or Kantian commands. Instead, develop the right character traits, so that whatever situation you find yourself in, you've got the skills to deal with it. Rules can be too black and white, too blunt. People will be familiar with all the sorts of paradoxes.

Alex O'Connor

Do you lie to the person at the door?

John Sellars

That's right. The lunatic comes to the door trying to kill your friend. Do you lie about whether your friend is there or not? If you think it's all about rules — don't lie, never lie — then you get into these sorts of problems. Whereas if you're developing the right character traits, and you find yourself in that situation, then on the basis of being just and fair to my friends, and given the specifics of this situation right here, right now, I can use the character traits I have in order to decide what to do, rather than unthinkingly applying a rule. And Aristotle was quite clear about this: there are no straightforward rules in life, because every situation is unique. So we need to judge each one as we find it. Virtue ethics is about developing the skills so you can cope with those very different, random situations.

Alex O'Connor

And what about this idea that these virtues sit in the midst of two extremes? You sometimes hear Aristotle described as believing in the golden mean. What's all that about?

John Sellars

He thinks vices are often extremes. If you go to the extreme, you're probably going wrong. The right thing to do is probably somewhere in the sensible middle. Which might not sound very exciting or sexy, but maybe it's true. People often think you want to push things to the limit, but actually maybe not. So he thinks a lot of virtues can be understood as existing in between two vices. Moderation is an obvious example — it's somewhere in the middle. Courage, he thinks, is in the middle between cowardice at one end and recklessness at the other. And for a number of other virtues this is a good way to think about them. Generosity is going to sit somewhere between stupidly giving all your money away and being really stingy and never giving any money away at all. So there's going to be a sensible middle ground.

Alex O'Connor

We all know people who are virtuous to a fault. We're so used to thinking there's good and bad, good and bad ways to behave, and as long as you're doing the good thing you should just do as much of it as you can. But then you come across the person who's too brave — the kind who always wants to stand their ground and get into a fight, or wants to stupidly run into the burning building even though there's no hope of saving anyone — and it makes you a bit uncomfortable. Or someone who's so kind that it's almost uncomfortable: you'd be a little uncomfortable in your chair, and they're like, oh my god, I'm so sorry, let me fix that, let me get you a pillow — and you're like, it's a bit much. It's too much. But obviously the too much in the other direction is also bad. So it's somewhere in the middle. And this isn't a unique insight to Aristotle — the Buddha's central path, and Confucius, have the same idea. It's well established in many ethical systems that temperance, moderation, being in the middle, is key.

John Sellars

Absolutely. Another example: if someone is incredibly selfish, that's clearly a vice. If someone pays no attention to their own personal needs to the point that they neglect themselves, that's clearly a vice as well. There's a sensible middle ground where people are looking after themselves, but not to the point of selfishness. But Aristotle isn't dogmatic about this. He says there are some things that are clearly just wrong, and there's no moderate version. A nice example he gives is that there's no moderate way to do adultery. Adultery is just not the right thing to do. So there'll be some exceptions, but he thinks it's a useful way of thinking about what the right thing to do is: probably somewhere sensible and central.

Alex O'Connor

Even with something like adultery — if you're talking about a physical act, it's pretty black and white — but even then, on the one side there's the person who has a wife and just doesn't care, who'll talk to other women and meet up with them and do all sorts of stuff. But on the other side there's the person who might be terrified to talk to anybody of the opposite sex, for fear that they're somehow doing something wrong because they've got a wife, and won't even talk to their best friend's wife. Even that, going too far, and really what you want is somewhere in the middle: I can have a wife and talk with women and have friendships and relationships with them without committing adultery. Even that sits on a continuum, and moderation is perhaps key.

The social animal

Alex O'Connor

What I'm interested in is that these specific virtues, which to us sound perfectly reasonable — bravery sounds good, courage sounds good, generosity sounds good — the way we got here metaphysically is by talking about the fact that there's such a thing as a human being, it has a natural function, and that function is reason. As philosophers we have to get rid of our assumptions that we know what's good and what's bad. Why is generosity reasonable? It seems nice, everyone likes generosity and generous people. But isn't it rational to be self-interested? Why not, if you can get away with it? If the only thing we're really talking about with Aristotle is what in fact serves the function of rationality, why generosity? Why bravery? Why these particular virtues?

John Sellars

That's a really interesting question. There are two different places where Aristotle comes close to giving a definition of a human being. One is to say "rational animal". Another is to say "social animal". Some animals live in packs and herds, others are more solitary; human beings live in packs and herds. We live in tribes, we live in villages. When we're born we're this long, utterly useless, and if we're left on our own we'd be dead within a week. So necessarily we're brought up in families. Our very survival depends on other people. So in order to survive, you have to get along with other people. So socially positive virtues like generosity and justice — and not running around killing everybody — are actually really important for our survival, absolutely fundamental.

We live in a culture where we've been encouraged to think we should all be ruthless individualists and can survive on our own, but that's just a lie. Really, it's a lie. We're all dependent on each other in all sorts of ways we might not immediately notice. People grow the food I eat. People filter the water I drink. I've never met these people, but I couldn't survive without them. So we're all dependent on each other in complex ways, and obviously today those ways are even more complex than Aristotle could ever have imagined. So getting along with other people is essential for our survival. That's the biological origin of those sociable virtues.

Is Aristotle's ethics descriptive?

Alex O'Connor

So do you think Aristotle's ethics is ultimately descriptive? When we think about ethics, it usually sounds mystical in a way we don't quite understand — you just should do this, there's this "should" component of the universe you just have to abide by. Whereas with Aristotle it sounds more like he's just saying this is the case: it is in fact the case that you're a human, which in fact has a particular function, and is in fact served by doing these particular things. Which kind of seems to reduce ethics to description.

John Sellars

Yes, you can certainly present it in a very descriptive way. This is Aristotle the biologist just describing this strange species he's encountered — he just happens to be one of them. But there's also a normative element that comes through. An adult human being who doesn't control their appetites and desires, and who never really thinks through their decisions — Aristotle is going to say that's a bad human being. They've gone wrong. They failed to be a human being in the full sense of the word, because they're not actualising their distinctive, defining capacities. And that feels really judgmental. In a sense you could say it's no different from him saying this eyeball is broken, in a very descriptive way — it's a bad table. But it feels as if there's a bit more normative force to it than that.

Alex O'Connor

But then it can also be quite attractive to people who are a bit suspicious of morality — maybe they're not realists about ethics and think it's all a bit wishy-washy. If I say that's a bad table, I'm not saying it's an immoral table. I'm not saying the table should hold things up in any sense other than that's what it's for and it's not doing it. And Aristotle's ethics could in theory be reduced to that kind of thinking, so that it's not mystical, not divine, not supernatural. It's just: there's a function you're supposed to serve, and you're not serving it, and that's all ethics really means. Which seems an easier pill to swallow than accepting this new ontological category of thing called "should" and "ought" that floats out there somewhere and we can't quite pin down.

I know Alasdair MacIntyre has that book After Virtue, which seeks to rehabilitate virtue ethics and point out that what we mean when we talk about ethics — should and should not, good and bad — is just a different language from the one someone like Aristotle was speaking. When he says words like "good" and "bad", he means them in a totally different way from the way we do, which is why we think ethics is weird and out there. Whereas maybe for Aristotle it's just a case of defining our terms differently, and realising it's not that profound.

John Sellars

Yes. And given the close interconnection between Aristotle and Christianity in the Middle Ages and after — and we talked about Aquinas earlier — we've used words like "virtue" and "soul", which are both very loaded terms coming out of that Christian tradition. So one thing that might put some people off Aristotle is thinking he's stuck within that model. But if we can ditch those terms and those associations and think, hey, this man is a natural scientist, a biologist, trying to understand organisms, and off the back of that he's producing what's ultimately a naturalistic ethics — we then end up with a completely different image of who he is and why we might want to take him seriously.

Alex O'Connor

That's interesting, the comparison with the soul. At first it sounds like something wishy-washy, but when you realise — as you say — if you didn't know you were talking about Aristotle, if you had a new atheist in a debate and someone said, well, how do you account for the soul, how do you account for what a human being is if there's no God? And the atheist goes, well, I think really what you're describing is just the fact that humans use reason, they have this animating principle, but it's just naturalistic, just a function of their biology. That would sound like a pretty robust atheistic response to a Christian. But that's kind of what Aristotle said.

And the same with ethics. If there's no God, how do you ground good and bad? Who's the moral lawgiver? Well, there isn't really one. It's just that humans are social creatures, they live in a society and act in particular ways that rationally serve their interests. Again, that sounds very much like the kind of thing you hear in debates about ethics between atheists and Christians. And yet Aristotle could just as easily be employed by the atheist as by the Christian — which is perhaps one of the reasons he's so influential: he just seems to slot in wherever you need him to fit.

Where to start reading Aristotle

Alex O'Connor

Aristotle is one of the most important thinkers. If people were going to go to the primary sources and read what this man has to say, I think most people recommend beginning with the Nicomachean ethics. I don't know if you agree, or maybe they should listen to this and then read it, or read a secondary source on his metaphysics. Where should people turn? There's your book, of course, which I'll link in the description — Introduction to Aristotle. But when it comes to the primary texts, where do you think people should go?

John Sellars

Actually, I think the easiest of all his texts to read — one we've not talked about — is his Poetics, in which he discusses Greek tragedy. It's just the most accessible. Anyone can pick it up and read it. And even if you think, I have no interest in Greek tragedy or how to structure the plots in stories, it does give you a window into his method and approach. What he's doing is what he does with every single subject: okay, let's analyse this, let's break this down, let's look at the components, let's see what all the bits are. How does a good plot work? What's the role of the characters? You get a taste of his way of thinking in a way that is really accessible.

You're absolutely right that the Nicomachean ethics is also quite good. It looks accessible because it's talking about topics people can connect with, but it is actually quite challenging, so maybe read that second. The Metaphysics is obviously really, really challenging — his book Metaphysics is really challenging — so that's probably one to save for a later day.