Tim Crane’s recommendations

An interview with...

Tim Crane on Metaphysics

About Tim Crane

Tim Crane is the Knightbridge Professor of Philosophy at the University of Cambridge. He works in the philosophy of mind.

Photo by Gilles FRANCOIS via Flickr

It's abstract and not everyone's cup of tea but, in many ways, inescapable. Cambridge University philosopher Tim Crane introduces the best books on metaphysics. 

What is metaphysics?

I think of metaphysics as the most general enquiry into the nature of reality.

How does that differ from science?

Science has metaphysical elements, but one way metaphysics differs from science is this idea of generality. For example, in chemistry you might learn about different kinds of chemical changes. In metaphysics you ask ‘What is change? How is change possible?’ No science will tell you what change is, but metaphysics is supposed to tell you what it is for something to change.

How could you possibly discover anything like that?

That’s a good question. The way people encounter metaphysics is often through problems or paradoxes. If you think of an object, the very, very same object — say a person — continuing to exist across time. Philosophers have thought of that in terms of identity. To be one and the same thing, — there’s only one of you and there’s only one of me, and thirty years ago there was only one of you and one of me. But then you start thinking about what it is for something to be identical and you say ‘Things are identical when they have all their properties in common.’ Then you get into problems, because I don’t have all the properties that I had thirty years ago. I’m slightly more bulky and I’ve got less hair — how can I be identical to what I was? What’s wrong? How can the very same thing have changed any of its properties, if having the same properties is what makes you the same thing?

 So I would say the way you find things out is by investigating the source of confusion and puzzle and mystery like that. That’s very different from the way that you find things out in science. Science might start off with puzzles and mysteries, but you don’t investigate it by pulling the problem apart, you investigate it by having data and having theories.

Another thing lying behind your question is ‘How do you know which view is right?’ Supposing someone says ‘Nothing ever changes,’ and someone else says ‘Everything changes.’ This is one of the oldest questions in philosophy — going back to Heraclitus — and I don’t have an answer to that question. That’s what people call the epistemology of metaphysics, the theory of how you know things in metaphysics. But I have a few guidelines, and one of them is that you should try and speak sense. You should say things that are sensible, and you should be sceptical of views that say things that are very silly. Now someone’s going to ask me, ‘How do you know what’s sensible? How do you know what’s silly? What’s your criteria?’ Well, come and talk to me for a bit and I’ll explain it to you…

So metaphysics has had a bad name in philosophy, and was particularly attacked by Wittgenstein and the logical positivists through the 1920s and 30s. Right up through the 1950s, metaphysics was used as a term of abuse in philosophy. If it was important, you couldn’t speak about it and for Wittgenstein and people like A.J Ayer it was literally meaningless verbiage.

Yes, this is something that’s not just twentieth century, it goes back to before that too. The Middle Ages was a popular time for metaphysics. The metaphysics of the medieval universities was based on the works of Aristotle through all sorts of complicated logical and metaphysical interpretations. In the seventeenth century, at the time of the Scientific Revolution, the philosophers who started the new science wanted to throw away all that metaphysics. They thought metaphysics was a load of tosh. What they actually did was just replace one metaphysics with another. The same thing happened in the twentieth century, in a way. You mentioned the logical positivists: they knocked out metaphysics as meaningless, basically by having a criterion for what’s meaningful — the ‘verification principle.’ That says that if something can’t be scientifically verified, then it’s meaningless. Either something is a tautology — that is it’s true by definition — or it has to be verifiable scientifically, and if it’s neither of those then it’s meaningless. The objection to this — which looks like a simple nit-picking objection, but is in fact very profound — is, ‘Is the verification principle itself verifiable?’ How could you verify whether something being meaningful or meaningless is a matter of its being verifiable?

So the verification principle is not present in any science. Many scientists might believe it, but won’t get a physics textbook that tells you at the beginning, ‘This is one of the fundamental laws of nature’ — like the Schrödinger Equation, or the laws of gravity. That’s the first concern about this, how can the logical positivists even say what they’re saying by their own standards?

The answer is it’s a complex analytic statement that is true by definition — you just have to unravel it a bit. That’s the claim.

Yes, that’s a very plausible interpretation of what they would say, that it’s something to do with the definition of the idea of meaning, that it has to be verifiable...But if I said ‘There are objects beyond the limits of possible experience,’ — that doesn’t seem to be a meaningless thing to say…So I think it’s a very feeble thesis but it captured people’s imagination because it looked as if you could finally make progress, you could put aside all those empty metaphysical debates  — or what they thought of as empty debates — about how many angels there could be on the head of a pin, or how is change possible.

The end-product of the logical positivist revolution was the metaphysical views of W.V. Quine. In English-speaking philosophy, he was probably the most influential philosopher of the twentieth century, and what he did was replace the logical positivists’ view of reality and knowledge with a metaphysics of his own. Some people talk about the inescapability of metaphysics, and I think that’s true. Wittgenstein was a different case. Wittgenstein’s critique of metaphysics was tied up with his critique of philosophy as a whole in his later work. He wasn’t saying that the rest of philosophy is fine, but metaphysics is not worth doing. He was very concerned about mathematics and meaning and language and the mind and questions of value and he thought that pretty much everything that philosopher’s said about this was all confused and rubbish, really. But, as you say, metaphysics came back. It reappeared sometime in the 1960s or 70s and now it’s one of the dominant areas of philosophy and people are just doing metaphysics unashamedly.

You’re one of those, and amongst other things you’ve co-edited a standard collection of readings in metaphysics that’s very widely praised and used. How did you get into metaphysics yourself? Which of the five books that we’re going to look at really turned you on to metaphysics?

 The first book I’m going to mention is by the philosopher who first taught me metaphysics — when I was an undergraduate in the 1980s — the late E.J. Lowe or Jonathan Lowe at Durham University. Long after he taught me, he wrote a wonderful book called A Survey of Metaphysics, which is very lucid and detailed. It’s not immensely difficult but it’s not talking down to people, it’s not metaphysics made simple either. It doesn’t have the admirable quality of Philosophy: The Basics which could be read by anybody, but it’s a survey of the main — or what Lowe considers to be — the central questions of metaphysics. He divides the book into six sections: The first is about identity and change, the question I mentioned. The second section is about necessity and the essence of things. The third is about causation. The fourth is about agency and human agency. The fifth is about space and time, and the sixth is about the universal and the particular. It’s just a fantastically lucid account of those six central questions of the western metaphysical tradition.

All very abstract as well, these concepts — the most abstract you could get, presumably, whilst still making any sense at all…

I suppose that is one thing about metaphysics, it is very abstract. Say causation: it’s very hard to grasp the idea of causation in the abstract. When you say one thing causes something else, so one thing makes something else happen, what is that? What is causation? Is there such a thing, what does it involve? This has been a central question of metaphysics since Aristotle really, and you have to consider these things in an incredibly abstract way. This is why it can be very daunting to people, and it’s not to everyone’s taste. But I don’t think the logical positivists or Wittgenstein have shown us that it’s impossible, and Lowe’s book, in fact, shows how you can make sense of these questions.

One of the difficulties for someone coming from outside the subject and trying to learn about it is discovering books which are written by people who genuinely have a grasp of the subject they’re discussing. There are lots of books with metaphysics in the title which aren’t a reliable guide to this area. So you’re saying this one is reliable, it’s by somebody who really understood what he’s talking about.

Yes, I would say it’s a very reliable guide to the subject as Jonathan Lowe saw it. He had very, very strong views himself in metaphysics, so it shouldn’t be taken as an even-handed overview of everyone’s views. But I think it could be read by someone without an enormous background in philosophy, unlike, say, Heidegger’s Introduction to Metaphysics, which is a very different kind of book, it isn’t an introduction at all, it may not even be metaphysics…

Let’s move onto the second book, which is a classic of philosophy, and often the book which is recommended to people beginning philosophy, Descartes’ Meditations.

This is one of the great works of philosophy, Descartes’ Meditations on First Philosophy, published in 1641. It’s a short book and it’s a book that many people know because of the famous doctrine of the cogito, ‘I think therefore I am.’ The words don’t actually appear in the Meditations — they appear in one of Descartes’ other works — but the idea that ‘I think therefore I am’, and that thinking is his essence for each of us, is one of the core points of the book. The book is composed of six ‘meditations’, which are written rather in the style of spiritual exercises of the time. Descartes was educated by Jesuits, and it’s important that they were called meditations because they were meant to be things that people would think through themselves, they would practice these modes of thought that Descartes was recommending. So it’s written in a very personal, very intimate and slightly confiding style. In the first meditation, he raises the question of which of any of his beliefs about the world will survive scrutiny. He challenges them all. He makes up certain imaginary scenarios and says, ‘Supposing, for example, I was dreaming. Which of my beliefs would survive scrutiny under the supposition that I was dreaming?’ And so on.

Many philosophers have thought that this book is a book about epistemology, or the theory of knowledge, and that Descartes is trying to refute scepticism, scepticism being the view that we know nothing. But if you look at the very first page of this book, he says that the book is called Meditations on First Philosophy, ‘in which the existence of God, and the distinction of the human soul from the body, are demonstrated.’ So that’s what he says he’s trying to to do: he’s trying to establish the existence of God, and he’s trying to establish the distinction between the human soul and the body. He doesn’t say, ‘in which I explore the foundations of knowledge and provide an epistemology or theory of knowledge.’ He doesn’t say anything about knowledge. This is a book of metaphysics, in my view.

But isn’t there a substantial part in the first meditation which follows on from his Discourse on the Method, which emphasises the need to have a way of discriminating erroneous beliefs from true ones?

That’s right, I’m exaggerating a bit. He has a criterion of truth, what he calls ‘clear and distinct ideas.’ What he can clearly and distinctly perceive, that is what he thinks is true. But the rest of the book is about how that criterion is put to use, not in distinguishing different types of knowledge, or relationships between knowledge and perception. He gives up the idea that perception is the main source of knowledge. This is one of the ways he criticises his predecessors. His predecessors, the Aristotelians of the Middle Ages said ‘There’s nothing that can come to the mind that hasn’t previously been in the senses.’ Descartes dismissed all that, and replaced it with this criterion of truth.

There is an epistemological element to this, some early discussion of how you could know if anything’s true, but how does he get onto the metaphysical reconstruction of reality, as it were?

He gets onto the metaphysics by building up, first of all, what he thinks his essence is. His essence is to think, he says, in a particular sense of the word think. Then he asks himself how that thinking thing that he is is related to his body. He argues in a number of ways for the existence of God, and he argues for claims about the nature of God, for God is not a deceiver so God would not have deceived him about the existence of things outside of his mind, and then he makes claims about the nature of what the nature of that reality is, and then the coup de grâce of the book is the argument for what he calls the real distinction between mind and body. He says although our mind and body are intimately connected, they are things that can be separated, and therefore they are separate things.

Why would we want to read a seventeenth century metaphysician? What is it about this book that makes it an interesting book to read? Is it just that it’s a classic, or is there something profound about it?

Your question is a very good one, because I don’t think anything in this book is true. I don’t believe in the Cartesian distinction between mind and body, I don’t believe in his criterion of truth, I don’t believe in the existence of God. I suppose what we’re doing when we’re reading philosophy books isn’t just looking for things that are true. We’re looking for a kind of understanding which will help us understand the questions — the first level metaphysical questions — that we want to answer. If I want to say, ‘What is the nature of the mind?’ then it’s illuminating for me to look at Descartes, not just because Descartes had a view which I can then contrast my own view with, but also questions of philosophy do not occur in abstract isolation, they are the product of the philosophical tradition. The philosophical tradition is a contingent historical connection between individuals, texts and the way that texts have been read. The questions that we confront now are very different from the questions that were confronted 600 years ago, or even 200 years ago. They are very different from the questions that are confronted by mainstream philosophers in France, let alone questions confronted by philosophers in China, or in India, in their traditions. There are many questions, and the questions that we have have been formed by our traditions. I think there’s a very artificial view that comes from the academic pursuit of analytical philosophy, — twentieth century, and twenty-first century English language philosophy on the whole — that assumes that there is an abstract menu of questions, that there are just philosophical questions that occur to people and that anyone who is thinking philosophically would end up with this menu of questions. I don’t believe that.

Are you saying that Descartes is important because his work forms part of our tradition, or are you saying he is interesting from a kind of anthropological point of view? You can see him in his context, how those particular concerns developed into a certain style of philosophising for him, and we live in a different context so we are just as much in our little fish tank thinking that we’re reasoning abstractly about important things independently of context, when in fact, it’s the temperature of the water and the other fish around us that are making us think the way we do?

Both of those are very good descriptions of our predicament, yes. But I think there’s another thing, which is that he’s a great philosopher. Not just any random thinker from the seventeenth century is worth reading. Descartes is a great philosopher, there’s a vision there, and encountering the vision of a great philosopher is a very exhilarating thing. Understanding very different realities from our own is a very illuminating thing too, it gives us the opportunity to question why we believe the things we do, as well as to understand how we ended up where we are. So many Cartesian ideas have dominated discussion. Some people say that they’re a kind of disease, the Wittgensteinians think this is all a big confusion. My view is slightly different which is that the questions that we have grow out of our tradition, and to understand the questions that we’re asking now, we have to understand something about where it comes from.

What about this next book, Real Time 2 by Hugh Mellor?

This is a great book. Real Time 2 is the second version of the book, which he published in (1998?). It’s a treatise on the nature of time which made an enormous impression on me when I first read it. It presents a vision of the world in metaphysical categories. It tells you about the nature of time, the nature of space, things, objects, events, in a way that is connected, but not the same as the physics of time and space. The relationship between the philosophy of time and the physics of time is much closer than what I said earlier about the relationship between the question of change and the question of chemical change, because there’s nothing in science that really tells you about what change is as such. But there are physicists who talk about the nature of time and space.  Hugh Mellor is someone who is very informed by those views, and knows the physics of space and time very well. He uses his knowledge of those, and his philosophical arguments, to defend a view of time, where time is rather like space. I think the simplest way to put it is to say that there’s no such thing in reality as now, there’s nothing that marks out in fundamental reality, which time is now, anymore than there’s something that marks out in the fundamental reality of space which place is here. Here is just where I am, and now is just the point in time which we’re thinking or uttering those words, so Hugh Mellor’s view has been called a block universe view of space and time.

In what sense?

Block universe in the sense that time is just one of the dimensions of space time. It’s a view that is common in physics, that we should think of space time as a whole, like a four dimensional block. If you imagine things occurring within space time are just regions of that block, four dimensional regions of it, or what sometimes people call space time worms. I don’t know why they say worms really. So, it’s called the block universe because time and space have the same ontological standing, that is to say they exist in exactly the same way.

But tense doesn’t?

In the first version of Hugh’s book, he called that way of thinking that we have of time — in terms of the past and present and the future — ‘tense.’ In the later version of the book, the book that’s now out and the one that you can get, Real Time 2, he changed his terminology. He changed the terminology back to the very boring terminology of the Cambridge philosopher McTaggart, where the way of thinking in terms of past, present, and future is called the A-series, and the way of thinking of time in terms of events being earlier than, later than, and simultaneous with is called the B-series. This is a typically dreary, boring philosophical label. Hugh changed to that label just because that was the way everyone else in the time community was talking.

What I like about this book is its painting of a metaphysical picture. So one way to express Hugh Mellor’s view is that the A-series, what he called tense, that is the way of thinking of time in terms of past and present and future, is not real. Past and present and future are not features of reality, any more than here and there are features, here-ness and there-ness are features of reality.

So, they are features of our relation to reality, rather than things independently of the particular subjective viewpoint on the world?

That’s right, they’re products of a particular subjective viewpoint, so when I say that this time is the present, I mean this is the time at which I’m thinking that thought, that’s Hugh Mellor’s view basically.

Did reading this book then change the way you thought about your own presence in the world? I mean I’m interested because obviously we think about time in relation to our own perspective. Is this kind of abstract theorising capable of transforming how you think about your place in the world?

That’s a really good question. In a way it ought to but, in this case, it doesn’t. Some philosophers do think that metaphysics should have that kind of impact on the way you think about yourself actually in the world, and in some areas of metaphysics I think it does. The metaphysics of the mind, which is my main subject, definitely affects the way you think about yourself and your own interaction with the world. I think the metaphysics of time doesn’t. Put it this way, Hugh Mellor’s view of time and the view that many people have, that people who are dead exist timelessly, that they’re still, in some sense, real, that they’re just not in the part of space time that we’re in — for me, that’s no consolation. It’s no consolation that people that I’ve loved who are dead exist in the ultimate block universe sense.

In contrast to, for instance, a metaphysical theory that involved the conclusion that God exists, which presumably would transfer back to how you experienced other aspects of reality.

I think so, yes, depending on what God was of course.  I mean if God is that Christian God, then that ought to affect your life. If God is something ineffable, indescribable that lies behind the phenomena, or something that is the object of mystical contemplation but not the God who loves us as a father loves his children, then I don’t think that does necessarily have any impact. If God is what Tillich called ‘the ground of all our being,’ then I don’t see what the ground of all our being would have to do with the way I live my life.

Similarly I guess with Spinoza’s God, if God is everything, then ok, fair enough.

Exactly, Spinoza’s God is the one fundamental substance, the one fundamental reality, which he also called nature.

Which leads us into another thinker who thought in abstract ways about metaphysics and came up with the idea that there is just one kind of thing, Leibniz. Going back to another text, or series of texts in philosophy.

Leibniz was one of the most brilliant thinkers who ever lived, I think, and one of the most interesting philosophers. He wrote many short things, and so Leibniz’s work is often collected into collections. They’re actually surprisingly readable given the abstract nature of the ideas. I would recommend a collection that has two of his great works, one is called the Discourse on Metaphysics, which is an early work of his, and the other is his correspondence with the great philosopher Antoine Arnauld. The correspondence with Arnauld is the best place to begin if you want to understand Leibniz. There’s a connection here with what you just said about Spinoza, but also with Descartes. Descartes thought that the mind and body were two separate substances, and in the notion of substance there is the notion of a fundamental being. The idea that the world contains substances is something that goes right back to Aristotle, it’s an idea about what the fundamental reality of the world is. For Aristotle, a substance was a persisting thing, a thing that continues to exist through change. I think the best way to think of it is that substances are sort of natural unities. The world contains, in a sense, natural unities or a natural order. Descartes thought that there were two kinds of substance, there were the mental substances, which are our souls, whose essence are what he called thought, and then there is the material world itself, and the material world for Descartes was just one substance. It was just one huge extended thing because Descartes identified the essence of matter with extension, by which he meant size and shape, so matter was a purely geometrical idea. The material world around us is fundamentally just one thing, and the material objects we encounter here and there are a kind of arbitrary clumping of matter, so to speak. Material objects have no real unity, and this is very much in opposition to Aristotle’s view where an organism, for example, has a natural unity of its own. Aristotle thought that an artefact, like a table, was not a substance, but that an organism, like a horse, was a substance, because it has a kind of natural unity. Leibniz thought that Descartes had gone a bit too far, and that there was some use for these Aristotelian ideas. In his early work he emphasised that it was important to go back to Aristotelian ideas, like the Aristotelian idea of substance in terms of a natural unity. He thought Descartes’ view of material substance was ok as far as science went, but metaphysics, he said, needed something more than simply the geometrical conception of matter.

So what was his step up from that conception, just in general terms obviously?

Leibniz thought that every substance had what he called a complete notion, and the complete notion of a substance was everything that was true of it — absolutely everything. So the fact that you’re sitting here now, the fact that you’re holding the microphone, the fact that you are twenty feet away from the window, all these things are part of your complete notion. In the correspondence with Arnauld, Arnauld raises the question, well if this is true, how could things have been other than they were? How could it have been that you didn’t conduct this interview with me, or that Julius Caesar didn’t cross the Rubicon, because it seems like from Leibniz’s view, if Julius Caesar hadn’t crossed the river Rubicon, he wouldn’t have been Julius Caesar because he wouldn’t have the complete notion of Julius Caesar. Leibniz was fully aware of this question, and what he said was that those things that are necessarily true of you, are those things that you, a finite being, could deduce from thinking about yourself, just from thinking about the nature of yourself. Whereas those things that are contingently true — that are true, but could have been otherwise, like Julius Caesar crossing the Rubicon — those are the things that only God can work out from looking at what he sees about your notion. So he has this very peculiar view about the nature of the reality where it seems as if, in a certain way, things couldn’t have been other than the way they are. If we add to this another element of his view, which is that God must choose the best, then it follows from this that things couldn’t have been better than they are. This is why Leibniz is often accused and mocked as thinking that this is the best of all possible worlds, that things couldn’t have been better than they were. This was the view that was mocked by Voltaire in Candide.

So why was Voltaire’s representation of Leibniz a caricature?

Because it’s very funny! I mean a good caricature has to resemble the thing that it’s caricaturing…

But does it also refute Leibniz?

No, I don’t think so. The way I’ve put it makes it sound slightly frivolous, but in fact what Leibniz was doing was following through the consequences of what seemed to be very simple principles, and if you really want to follow through the consequences of your principles, then you have to accept certain things. Philosophers sometimes do this, but sometimes they’re not very good at doing this, sometimes they just refuse to follow through the consequences, and just say ‘Ah, I couldn’t possibly believe that, but I still hang on to my principle.’ Leibniz’s principle was first that God chose to create this world as it is, rather than in some other way. He also thought that God was wholly good, and that God must choose the best. It follows from that that this world is the best, so if this world contains things that seem less than the best, then we have to understand how that can be so, and Leibniz devoted a whole book to that which was called Theodicy - theodicy here being the explanation of why there can be evil in the world, given the existence of God. It’s an old problem, but Leibniz faced up to it in a way that many religious thinkers don’t.

It’s interesting because both Descartes and Leibniz were brilliant mathematicians in their own right, and there is a certain rigour to their reasoning process, I suspect, as a result of that.

Absolutely. Descartes invented Cartesian coordinates, the representation of geometry that we all learn at school. Leibniz invented calculus, along with Newton. They were both very rigorous thinkers. I actually think philosophically Leibniz was a more rigorous thinker than Descartes, he was more aware. Descartes had more sense in a way. For example, Descartes defined substance as something which was capable of independent existence. It follows from that definition, and other things he believes, that God is the only substance, because everything is dependent on God, so why didn’t Descartes say, as Spinoza said, that God is the only substance? Because he didn’t follow through the consequences of his definition.

Or perhaps he was worried about the heretical implications?

That’s true, he wanted to be theologically orthodox. What he says, essentially, in his Principles of Philosophy is ‘Ok I can see that this definition sort of implies that God is the only substance, but let’s put that to one side for the moment.’ Sometimes you have to do that in philosophy if you don’t want to end up with these crazy positions like Leibniz’s.

So back to Leibniz, you’ve described his view as crazy. Why would I want to read a book by a thinker whose conclusions I so strongly disagree with?

There’s the general reasons I mentioned earlier, in connection with reading the great philosophers, and learning about our tradition. In the case of Leibniz, what you see is that he faced up to certain questions about the essence of things, the essence of people, in a way that few thinkers have really faced up to them. Even if you don’t agree with him, it’s really good to ask yourself the question that he’s asking. ‘Was it part of the nature of Caesar that he crossed the Rubicon?’ And you want to say, ‘Well, no, because he might have existed without crossing the Rubicon,’ and you say ‘What makes him Caesar then? What is the essence of Caesar?’ And almost no one has a good answer to that. Now of course one way you could go is to say ‘It’s a ridiculous question, it’s a meaningless question,’ or ‘It doesn’t make any sense.’ But it’s not a ridiculous question. I can easily contemplate how my life would have been if I’d done certain other things, and I’m assuming there that I’m the very same thing. What does that mean for me to be the very same thing? That’s the metaphysical question that you have to face, and it’s raised by Leibniz’s work. He has an answer to it. He provides one extreme view that we have to balance ourselves against, and actually it’s very similar, in many ways, to the views of one of the leading philosophers of the twentieth century, David Lewis. In some ways he had similar views to Leibniz, and Lewis is now someone whose views are widely accepted and followed by people in philosophy.

Now, the title of the next book, Sameness and Substance Renewed, suggest a similar focus on what it is to be the same thing, what it is to be a substance.

Yes, there’s a theme here, in my books. In fact there are a number of themes. This is Sameness and Substance Renewed by David Wiggins, which, like Hugh Mellor’s book, is a rewritten version of an earlier book. David Wiggins’ book is about sameness, that is to say, identity, and it’s about substance as well. What substance means, what Aristotle meant, this very complex concept which has grown up in the history of philosophy where substances are the fundamental realities.  Wiggins was someone who was very influenced by Aristotle, and by Leibniz too, and I’m very interested in this book. I find it a fascinating book. One of the things I like about it is the way that he draws eclectically on texts from the history of philosophy to illustrate his points. Another interesting thing about it is that he made a very original contribution to the discussion of personal identity — that is the sameness of persons over time — where he tried to combine views which treat the psychological nature of the person as very important to their identity, with views that treat the biological nature of the human organism as important, and that’s a very original contribution to the view about what makes a person the same person over time. That’s one of the many things in this book.

The tendency in philosophy is to downplay the physicality of personal identity.

Absolutely. The dominant view of personal identity is the view that comes from Locke, which is that a person is a thinking, reasoning being that thinks for itself as itself, the same thinking thing across time, or something like that. So that means that you are your mind, essentially, and that could just as well be your brain. So it’s not a Cartesian view, but what it means is that if my brain went into your body, and your brain went into my body, then we would have swapped bodies, rather than got new brains. Now, that’s been a very dominant thought in the debate about personal identity over the last 50 to 60 years. What philosophers like Wiggins, and those who follow him, reject about this, is that it’s not so much the connection between being a person, and being a thinking and reasoning thing, but — and this is the way I’d like to put it, rather than the way Wiggins would put it — rather the connection between what you are, and what it is to be a person. So for example, supposing we can agree with Locke, that we only think of something really as a person when it’s a thinking reasoning being. Then I also think that I was once a foetus, and a foetus isn’t a thinking reasoning being. So that means I existed when I was not a person, and to use a concept from Wiggins’ work, a person there is a ‘phase concept.’ Wiggins uses the notion of a phase sortal concept, it’s a concept that only applies to things at certain phases of their existence, like the concept child, or the concept student. It’s a phase you’re going through, and one of the things I take from Wiggins is that you should think of the concept of a person as a phase concept. I existed before I was a person. If by some terrible calamity I went into a persistent vegetative state, then I would continue to exist, but I may not continue to be a person. So I think this has broken the deadlock in the personal identity debate in philosophy. You can now think of yourself, that what you are and the person that you are, can come apart. You are the organism, and for a period of its existence, the organism is a person.

That strikes me as a kind of metaphysics that does, or is likely to affect how you think of yourself. It really does seem to be like religious metaphysics, it will have an impact on someone’s life to think of themselves as in the phase of being a person, though they will still be something when they cease to be a person. Would I still exist as I decay as a body?

That’s a good question. I give it the answer no. When I say that you are an organism, I think you are a living organism. Your death is the end of you. There are other views, some people, I think rather perversely, have argued that dead people are people, so if we’re actually counting the number of people in existence, we have to count all the dead ones too. I don’t think dead people are people, and I don’t think dead organisms are organisms.

So what’s the common thread running through all these books? It’s a really interesting selection of books, a combination of classic texts and more recent ones. What was the unifying theme here?

I didn’t choose them for this reason, but looking at the books I see there is a theme, which is that there’s an orthodoxy in philosophy at the moment that I want to reject. The orthodoxy comes from philosophers like W.V. Quine and David Lewis, and what it says is that what there is in the world is very sparse. Quine once described his philosophy as being dominated by a taste for desert landscapes. He thinks, fundamentally, that there’s just physical particles and everything else on top of that is just a way of talking, so to speak. Lewis says that all there is is just space time with physical properties instantiated over space time, and everything else is just not so real as that. These are very sparse views of reality that put a big emphasis on the material nature of the world, or the physical nature of the world. They take physics as their starting point for metaphysics, or ontology, the theory of being, and their physicalist views of the world. They’re very much in contrast to the views inspired by Aristotle, which see the world as a much more messy place. You know Aristotle’s example of the fundamental being was not an atom, or an electron, but an organism, like a horse, that’s a fundamental being. My books reflect my opposition to that physicalist, sparse world picture which is dominant particularly in American philosophy. I think the views of Descartes, the views of Leibniz and the views of contemporaries — Mellor and Wiggins and Jonathan Lowe — have a much richer, more varied ontology that’s much more sensitive to the messiness of the real world as we encounter it. That’s why I like the idea of substance, which is really what links some of these things together, the idea of substances as the natural unities of the world that we’re trying to discover, that aren’t just the fundamental particles of atomic physics…

What’s that all got to do with the mind?

Many philosophers think that the important question about the nature of the mind is how does the nature of mental things — like thoughts and experiences and emotions — relate to the physical nature of the world, the atoms and the molecules the world is made up of. Many of them think that something like Quine’s and Lewis’ physicalism must be true, and that the world must be fundamentally physical. I don’t think the world is fundamentally physical. So I think, for example, that if a human person is a real thing, and the human mind is a collection of the capacities of the human person, and if the human person is a certain phase of the human organism, these are as fundamentally real as anything in physics, as any atoms or molecules that make the person up. I don’t want to defend a Cartesian view of the mind, but I don’t want to defend a physicalist view either. We should accept the messy reality of the everyday world where we see persons with their minds as fundamental things that need to be understood in their own terms.

Interview by: Nigel Warburton

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