The Best Immanuel Kant Books

Could you begin by saying a little bit about who Kant was?

The first thing that I want to say about Immanuel Kant is that he was the greatest philosopher of all time. That’s controversial, obviously, and other people would have different views, but in my opinion he is the all-time great.

He was a German philosopher who lived in the eighteenth century and was very much part of the Enlightenment. He was responsible for many of the main ideas that we associate with the Enlightenment, and, in particular, the idea that we should trust to no authority except our own reason, that on all the most fundamental questions about life, including questions about how we should conduct our lives, the ultimate authority was what we could glean from the exercise of our own reason.

The motto of the Enlightenment was ‘dare to be wise’ and this was a motto that was very dear to Kant’s heart. You can see why: this was an injunction to have the courage of our own convictions, the courage of our own resources, and in particular the resources of our rational faculty.

He’s usually thought of as a German philosopher, and he wrote in German. But, historically, that’s not quite accurate is it?

He was born in Königsberg in Prussia. The town itself now goes under the name of Kaliningrad, which is part of Russia. But, yes, we ordinarily think of him as a great German philosopher.

In your Five Books selection you haven’t included a biography. That’s probably no accident.

It is no accident. There are biographies of Kant. There’s one that came out not very long ago—about fifteen years ago—which I personally found an interesting read, but that’s because I have this special keen interest in Kant. (I am referring to Manfred Kuehn’s biography, simply entitled Kant: A Biography.) For most people this would not be a particularly inspiring read. Kant didn’t have a very interesting life. The biography is fascinating because of the light that it casts on his philosophical work, the actual composition of that work, and the various processes that he went through as he was producing his books; but there’s not much in the way of an external story to sustain people’s interest. He was born in Königsberg, lived all of his life in Königsberg, and—famously—never travelled very far from Königsberg. He was a confirmed bachelor and was devoted to philosophy. If you want to get a sense of Kant the man and of his life, the thing to do is to read his philosophical works rather than consult a biography. Philosophy was his life.

We’re going to begin with a book that is notoriously difficult to understand. You could genuinely spend a lifetime delving into the meaning of various sentences and arguments. The book is his first Critique, the Critique of Pure Reason (1781).

This is the one book on the list that is a complete no-brainer. If you’re thinking about the five key texts for an understanding of Kant, this has got to be one of them.

I began by saying that, in my view, Kant was the greatest philosopher of all time, and I also want to say that this is the greatest philosophical book of all time. This is his masterpiece. It covers a huge amount of territory. Part of what is so impressive is the range of topics that he discusses in the course of it—although, interestingly, it doesn’t cover as much territory as he originally intended. We’ll be looking at other books in due course, and some of the material in those other books was originally going to be part of the Critique of Pure Reason. In a way, what’s going on here is that those other books contain the material that Kant himself thought was most important—the stuff that he was keenest to get to. But before he could get on to those other topics, he felt that he had to do a lot of preliminary groundwork, and that’s what you find in Critique of Pure Reason. But it turns out to be so fascinating, and has such far-reaching implications, that it has become a classic in its own right.

Is it fair to sum up this book as about the limits of what we can discover with our reason?

Yes. In a way, that’s the point. Some of the questions that Kant is particularly interested in—and that he will get on to in his later works—are questions where this issue is particularly pertinent. So, yes, Kant in this book is interested in limits. He’s interested in the limits to what we can know; he’s interested in the limits to what we can use pure reason to ascertain; he’s interested in the limits to what we can even think about. He’s interested in these limits in various different senses. On the one hand, he’s keen to approach them, to map out the limits from within by doing as much as possibly can be done through the exercise of reason; but he’s also interested in stepping up a level and looking at them from above, asking questions of principle about where these limits are to be drawn and what might lie beyond them. Of course, there’s an inevitable problem that arises there because if you’re asking questions about what lies beyond the limits of knowledge then inevitably the question arises: can you hope to know any answers to such questions? For if you claim you can, aren’t you involved in self-stultification? So, all these tensions are there throughout the Critique, and they’re part of what makes it such a fascinating read.

Kant described himself as being stirred from his ‘dogmatic slumbers’ by reading David Hume’s work. They are such completely different writers – it feels slightly surprising to think that David Hume’s highly empirical work should give rise to something which is so much more abstract and focussed on the powers of reason, rather than on the powers of observation.

That’s right. What we find in Hume is a classic commitment to empiricism. The phrase ‘empiricist’ is entirely appropriate in connection with Hume. He takes very seriously the idea that our knowledge and understanding of the world are constrained by experience. In some very deep sense, they are limited to what we can experience. The reason why Kant says that he was woken from his ‘dogmatic slumbers’ when he read Hume was that he had previously, rather unthinkingly, taken for granted that we had the intellectual resources to broach questions and consider issues that transcend experience, in just the sort of way that Hume denied was possible. It wasn’t just that. Hume had also taken his empiricism sufficiently far to call into question some of the basic ways in which we think about experience itself. This also was a bit of an eye-opener for Kant. He recognised that there were issues here that needed to be addressed.

He was very impressed by Hume’s arguments, though not actually ultimately persuaded by them, and thought that it was incumbent upon the philosophical community at large, and on him in particular, to do what he possibly could to address these arguments. So that all fed into this broad project that we’ve already described in the Critique of Pure Reason, of trying to determine just how far reason can go, determining to what extent Hume was right in saying that our understanding and knowledge are constrained by experience and to what extent he was wrong.

“This is the greatest philosophical book of all time. This is his masterpiece”

There’s a lot that Kant is prepared to accept in Hume’s empiricism. He agrees with Hume that there is a fundamental sense in which our knowledge is constrained by experience. Where he most fundamentally takes issue with Hume is that he draws a crucial distinction between—as he puts it—what we can think and what we can know. Kant’s view is that, although Hume is right with respect to what we can know (that that is constrained by what we can experience), we can think about things that transcend our experience. We can have thoughts about things that we can never hope to have any insight into, but where, nevertheless, the very process of thinking about those things can still play a significant role in our lives.

So, one striking and obvious example of this, which we will be talking about a little bit later, is the existence of God. Nobody can know that God exists, no one can hope to establish the existence of God, in Kant’s view. This is an issue that lies beyond the reach of our own experience. The various attempts that people have made to prove God’s existence were all, in Kant’s view, futile. He spends a large part of the Critique of Pure Reason laying into these attempts. But it does not follow, in Kant’s view, that the question as to whether God exists should be dismissed as meaningless. It is still a perfectly legitimate and interesting question. There is still room for us to think about God’s existence and perhaps to have faith in God’s existence. Indeed, there is one very striking sentence in the preface to the second edition of the Critique of Pure Reason where Kant describes his project as ‘denying knowledge in order to make room for faith’. So, you can see that there’s a negative project and a positive project that are intertwined. On the one hand, he is curbing our pretensions to know more than we can; but, on the other hand, he is doing so as a means of opening up the ground for the possibility of faith.

An important distinction that Kant makes is between the ‘noumenal’ world and the ‘phenomenal’ world. What exactly is going on there?

This is an absolutely crucial distinction that permeates the Critique of Pure Reason and is very relevant to all of the later work as well. Basically, it is a distinction between appearance and reality.

Many philosophers have believed that there is a fundamental distinction between appearance and reality. Kant is part of that tradition and makes a distinction between appearance and reality that is as profound as anyone’s. The way this comes about is that, in the process of exploring the scope and limits of our rational knowledge, he comes round to the view that some of what we can know through an exercise of reason can only be explained if it is due to us imposing a framework onto our experiences that is already built into our minds. An analogy that is very often used to illustrate this idea, which is in some ways a crude analogy, but in other ways, I think, a very helpful one, is that of a pair of spectacles. It’s as if we are born with native spectacles through which we see everything but, unlike ordinary spectacles, these condition what we see in a very profound way. Ordinary spectacles can literally colour what you see as well: if you’re wearing rose-tinted spectacles then everything will appear to you as having a rosy hue. For Kant it’s a bit like that, but with bells on. Among other things, he thinks that even the fact that we experience things in space and time is due to these native spectacles that we carry around with us. Space and time themselves are part of the spectacles.

“We have knowledge only of ‘phenomena’—Kant’s word for appearances; we don’t have knowledge of ‘noumena’—how things are in themselves”

This is why you get this fundamental division between appearance and reality. All that we ordinarily think about, all that we aspire to discover when we’re involved in the natural sciences, is concerned with the world of space and time and that’s the world of appearances: that’s how things look to us through the spectacles. Kant is adamant that we can never take these spectacles off. If we could take them off, then we might be able to see how things are in themselves, but that’s precisely what we can’t do, and that’s why this distinction between appearance and reality hits so hard in the Kantian system. We have knowledge only of phenomena – ‘phenomena’ is Kant’s word for appearances – and we don’t have knowledge of noumena – ‘noumena’ is the word that he sometimes uses for how things are in themselves.

This is related to what we were talking about a little earlier, because the question of whether there is a God or not is not a question about anything that’s going on within the world of space and time. However extensively you search, however closely you peer into the cracks, you are never going to find a divine being: whether there’s a God or not is a matter of how things are in themselves. It’s a matter of the world of reality, not the world of appearances. This helps to tie in with what we were saying earlier about Kant’s conviction that matters like the existence of a divine being are matters of faith, not matters of knowledge. Knowledge is restricted to the world of appearances.

Just to get this clear, somebody reading this could think that you’re discussing a psychological limit to our experience—a limit set by how our brains happen to be. Is that what Kant is saying, that we have brains that are only able to cope with things which occur in space and time and can be explained in terms of cause and effect?

We have to think of it as something even more profound than that. No doubt, there are all sorts of interesting ways in which our brains do condition how we experience things: perhaps there are differences between us and other animals so far as that goes, and perhaps there are differences between us and aliens on other planets, if there are such beings. But those are themselves matters of empirical investigation. Our brains are themselves physical objects. That’s all part of what’s going on within this spatio-temporal framework. Kant is talking about something that’s even more profound than that because the very fact that we’re seeing things in spatio-temporal terms at all is part of how we condition our experiences. It’s part of the spectacles that we’re carrying around with us. So, the brain analogy is a good one; but ‘analogy’ is the operative word here. It can at most be seen as another illustration of the idea.

And these are logical constraints on reality rather than empirical ones?

That is another important point in this connection. That’s right. Kant believes that these discoveries that he has come to about this fundamental distinction between appearance and reality and all that comes with it are discoveries that are themselves the product of pure rational reflection. Here he is doing philosophy, not science: whatever else it is, the Critique of Pure Reason is a philosophical work. Again, you’re absolutely right: we have to distinguish between what’s going on here and what’s going on when psychologists or physiologists investigate the ways in which brains—or even our minds, for that matter—influence how we see things.

So, we’ve got these glasses on that we can’t take off. Is Kant saying that through his use of reason he’s able to think about what the world might be like in some respects if we didn’t have the glasses?

Yes. Up to a point, he thinks there’s room for genuine speculation here. He’s absolutely adamant that it’s never anything more than speculation. The minute we think we can derive any conclusion about how things are in themselves, the minute we think we have the intellectual resources to explore beyond the limits of our spatio-temporal experience, we find ourselves in trouble: our arguments start undercutting themselves, and we’ll find we have what look like equally compelling arguments for opposite conclusions. It’s just a mess. We have to admit our limitations and we have to admit that we can’t know how things are in themselves.

“The minute we think we have the intellectual resources to explore beyond the limits of our spatio-temporal experience, we find ourselves in trouble”

But that doesn’t stop us from speculating, and one possibility that we keep coming back to is that there’s a supremely powerful, benevolent deity directing the workings of the world. Of course, a lot of people have had that belief and it’s played a supremely important role in their lives, and Kant thinks that that’s perfectly legitimate as long as we recognise that it is an article of faith and that it’s not something that we can ever hope to make more secure than an article of faith.

What’s your second book choice?

I’ve chosen another book by Kant with a rather forbidding title: Groundwork of the Metaphysics of Morals [1785]. But, basically, this is an introduction to Kant’s moral philosophy. ‘Introduction’ is a misleading term in this context because it’s quite a forbidding read – no one could claim that it is easy. But it lays out the fundamental principles of Kant’s moral philosophy.

To go back to something that I was saying earlier, originally a lot of the material in the Groundwork was meant to be in the Critique. It’s interesting to look at the connection between the two works. How was it that a book that was originally supposed to be fundamentally about ethics ended up being the Critique of Pure Reason? The answer relates very much to the conversation that we’ve just been having. Kant recognised the importance of ethics and he recognised the importance of trying to do one’s duty and to live one’s life in accordance with the distinction between right and wrong. But he was also well aware that recent advances in science, in particular the success of Newtonian mechanics, looked as if it was posing a threat to the very idea of ethics. It was looking increasingly as though everything that happens in the world could be explained as the result of inexorable causal laws. The popular view that more and more people were beginning to take seriously was that the world basically consisted of a lot of tiny billiard balls knocking into each other in such a way that, in principle, you could predict with absolute certainty everything that was going to happen.

“Advances in science, in particular the success of Newtonian mechanics, looked as if it was posing a threat to the very idea of ethics”

Kant took that picture very seriously. In fact, he didn’t just take it seriously: it was part of his project in the Critique of Pure Reason to argue that every event has a cause, that everything is completely causally determined. But if everything is completely causally determined then it immediately looks as if there’s a threat to the very idea of free will. It looks as if we can’t possibly be free agents. In particular, of course, it looks as if we can’t possibly be free moral agents. The very idea of a distinction between right and wrong looks as if it is under threat as well. And so, that’s why Kant felt that he had to indulge in all that elaborate metaphysical work before he could get on to what was really of interest to him. He somehow needed to be able to reconcile his commitment to Newtonian science, and to the principle that every event has a cause, with his equally ardent commitment to the possibility of free will.

How is free will possible in a phenomenal world that is all about cause and effect?

That’s the key question. I have been saying he’s trying to reconcile the two but, of course, we need to be told how the reconciliation goes. In fact, it’s a direct application of what we were talking about in connection with the Critique of Pure Reason. He goes back to the idea that there is a fundamental distinction between appearance and reality, between the phenomenal and the noumenal. Everything is completely causally determined in the phenomenal world. So how can there be freedom in the phenomenal world? The answer to that question is: there can’t be. There really is no room for freedom in the phenomenal world. Complete causal determination does indeed rule out freedom, says Kant. Other people have taken a different view, but that was Kant’s view.

“We hope we are free agents, because without freedom nothing in our lives seems to make sense”

How then does he square the circle? The answer is: by appeal to the distinction between appearance and reality. Our freedom is a feature of how we are in ourselves. This is something that works at the level of reality, rather than at the level of appearance—although it does mean that, just as in the case of the existence of God, strictly speaking we have to regard our belief in our own freedom as an article of faith. It is just like the existence of God—we can’t hope to prove conclusively that we are free agents. We hope we are because without freedom nothing in our lives seems to make sense. Ultimately, however, it’s another article of faith.

Much of the Groundwork is concerned with developing the idea of what he calls the categorical imperative. Perhaps you could just spell out in broad terms what that is and why it’s so important for him.

The Groundwork is divided into three chapters. What we’ve just been talking about dominates chapter three. But in the first two chapters of the book, he’s actually just doing moral philosophy. What he’s trying to do in those two chapters is establish the fundamental principles of morality or – ideally – the fundamental principle. One thing that I think is important to appreciate is that he takes himself to be preaching to the converted. He doesn’t see this as an exercise in trying to persuade anybody of anything. He thinks that, if you want to know what the basic difference is between right and wrong, you don’t read his Groundwork, you don’t consult any philosophical text, you consult your own conscience. He thinks people already know perfectly well how to distinguish between right and wrong. They don’t need Kant to tell them – that’s not his business, that’s not something he sees as necessary or possible for him to do. People already have a sense of the distinction between right and wrong.

“People already know perfectly well how to distinguish between right and wrong. They don’t need Kant to tell them”

What he can do, as a philosopher, is take this basic knowledge that people already have and systematise it. That’s the aim of the exercise in the first two chapters of the Groundwork. It’s in the course of systematising our moral beliefs that he develops the idea of the categorical imperative. Put very simply, what he’s doing with the idea of the categorical imperative is emphasising that what’s distinctive about morality is that it lays down certain things that we just simply should do, whether we like it or not. So, he draws a distinction between categorical imperatives and hypothetical imperatives. One way to illustrate this distinction is this: suppose I’m watching you playing tennis with a friend, and it’s clear that you’re having a great deal of fun out of this. Both you and your friend are thoroughly into this game and getting a lot of pleasure from your activity. But it’s also clear to me as a bystander that neither of you are very good. So I speak to you afterwards and say ‘Look, Nigel, you really should have some tennis lessons.’ And you say ‘Why?’ And I say ‘Well, to improve your game.’ Now, if you turn round to me and say ‘I’m not particularly interested in improving my game. All I was interested in was having fun and my friend and I were both having a great deal of fun,’ then there’s a sense in which that’s absolutely fine. When I said you should take tennis lessons, it was all based on the assumption that you would be interested in improving your game. But if that’s not something that you’re particularly keen to do, then so be it.

But if I overhear you telling some outrageous lie to your friend and I take you to one side afterwards and say ‘Look Nigel, you really should stop telling these ridiculous lies,’ and you say to me ‘Why?’ and I say something along the lines of, ‘to be a better person’ —if you then turned around to me and said ‘I’m not particularly interested in being a better person’, there does seem to be a difference between the two cases. In this case, it looks as if your reply is inappropriate; whereas in the first case, you were well within your rights to tell me that you didn’t particularly want to become a better tennis player. But if you tell me that you’re not particularly interested in becoming a better person, I still have a comeback. I can turn around to you and say, well, you should be.

“What characterises morality is that is does involve this fundamental categorical imperative: there are certain things that we should simply do, full stop”

There’s this basic distinction Kant is drawing between things that you should do whether you like it or not—those are what underpin the categorical imperative—and things that you should do only if you have certain aims and aspirations—which are mere hypothetical imperatives. He thinks that, by the time we’ve thought about the basic difference between right and wrong, we’ll see that what characterises morality is that is does involve this fundamental categorical imperative. There are certain things that we should simply do, full stop, irrespective of our aims and aspirations.

And these are universalisable in the sense that it’s not just that I ought to do these things: anybody else in relevantly similar circumstances should do too.

That’s right. In a way, that’s part of the very idea of a categorical imperative: it’s something that applies to you whether you like it or not, simply by virtue of the fact that you’re a rational agent. The sheer fact that you’re somebody confronted with choices about what to do means that, among other things, you must do x or you must refrain from doing y. It’s in these terms that Kant thinks he can formulate a fundamental principle of morality because he says that if you’re in a position where you are trying to decide whether it’s legitimate for you to do something—for example, if you’re wondering whether it would be reasonable or legitimate for you to lie in a particular situation—whether that is so or not must ultimately depend on whether what it is that you’re about to do could be generalised. If you think it’s legitimate for you to do x in these circumstances, are you prepared to sanction a universal law to that effect so that anybody else in these or relevantly similar circumstances would be entitled to do x as well?

Kant believes that as you think it through you’ll begin to see that a lot of things that we are tempted to do will straightforwardly emerge as wrong because it simply wouldn’t be feasible for everybody to live their lives that way. So, the lying example is a classic example. Here I am, I’m tempted to tell this lie and I ask myself what would it be like if everybody did that. I think to myself: ‘Well, hold on a second. If it were well known that you could get away with lying in certain circumstances, after a while communication itself would just break down. We wouldn’t be able to trust the things that people are telling us; we wouldn’t know when to think that they were telling the truth and when to think that they might be lying, and so forth.’ I’m missing out a lot of the details and when you spell out the details a lot of people think that Kant’s argument is unsuccessful, but there you get a flavour of the sort of strategy that he adopts.

Not in the Groundwork but elsewhere he famously bit the bullet and said that if an axe-man came to the door looking for your friend and asked whether the friend was in the house, if the friend actually was in the house then you had a duty to tell the truth.

He did bite the bullet. Whether we agree with Kant or not—and obviously a lot of people would straightforwardly take issue with Kant on this—the fact that he’s prepared to bite the bullet is very striking. It’s another indication of the rigour that underpins his moral philosophy. He’s completely uncompromising in his ethics. What characterises it is its uncompromising nature: what you must do, you must do. Full stop. That’s dictated by these universal, exception-less principles that apply to all people in all circumstances. It’s the very antithesis of consequentialism, which is a view in moral philosophy according to which what’s important about what we do are the ultimate consequences and the ends can justify the means. Kant is the arch-opponent of that view. For Kant, the ends never justify the means; the means are themselves what really matter. It’s what you’re about to do, considered in and of itself, that is crucial.

The Groundwork of the Metaphysics of Morals is quite a short book. We’re moving on to a longer one again with the third choice.

I now want to consider another book that Kant wrote. In English, the title is translated in different ways. It used to be regularly translated as the ‘Critique of Judgement’ but a more recent English edition has come out with the title translated as the ‘Critique of the Power of Judgement’ [1790]. There is so much going on in this book that I cannot even begin to do justice to it now. It’s the book in which Kant tackles questions about aesthetics: the whole idea of beauty (which he considers at great length); the whole idea of the sublime. He also considers questions of scientific methodology and looks at how our conception of teleology is relevant to the way in which we pursue science. He covers a vast amount of territory. From that point of view, it’s like the Critique of Pure Reason: it’s staggering just for its breadth. So I’m not even going to try to summarise it. But what I will do is say just a little bit about how this work fits in with the other two that we’ve been considering so far.

After you’ve read the Critique of Pure Reason, and after Kant’s ethical work including the Groundwork, you have this powerful sense of this fundamental divide between appearance and reality which we’ve already seen is very important to Kant. But you also have a slightly schizophrenic feel, because you realise that one of the important features of Kant’s whole picture is that we, ourselves, are located on both sides of this divide. Part of the reason why it’s so important for Kant that we are located on both sides of the divide is that we are free rational beings in ourselves: that’s a fact about us that transcends the world of space and time. But, on the other hand, we also, of course, ordinarily think of ourselves as creatures within the world of space and time. So, we’ve got all this moral machinery that only applies to us because of our status as free rational beings in the real world. And then we’ve got everything that science is concerned with: the world of space and time, the world of appearances. One of the questions that Kant is shaping up to when he writes the Critique of the Power of Judgement is ‘What does it feel like to be a creature with a split personality of this kind, a moral agent exercising freedom and yet thinking of oneself as an animal creature in the world of space and time, governed by causal laws?’

One of the things going on, and one of the reasons why this Critique of the Power of Judgement is such a fascinating work, is that Kant asks some fundamental questions about the way things must make sense to us for us to negotiate this divide. There he is in the Groundwork trying to explain or unearth the fundamental principles of morality, telling us what the fundamental distinctions between right and wrong ultimately come to; here we are, trying to put that into practice. It’s only going to be possible for us to think about this, ultimately, in spatio-temporal terms. But there’s no guarantee that it’s going to be possible for us to do even that. The way our actions show up in the spatio-temporal world might not have any discernible relevance to the exercises of freedom that are underpinning them. Maybe, if I do the right thing—if I exercise my freedom in the right way—as far as the consequences in the world of space and time are concerned, that will always result in misery and catastrophe. There just might not be any harmonious interplay between the world of appearance and the world of reality in the way that we need there to be if this is ultimately going to make any kind of sense to us. We’d like to think that the difference between doing right and wrong had some sort of relationship to our ability to avoid misery and catastrophe. And to the extent that we find that there is a harmonious interplay between these two worlds, to the extent that we can make sense of things, to that extent we feel a certain kind of pleasure. So, this comes back to the question of what it feels like to be in this situation.

That is ultimately Kant’s story about what beauty is. The pleasure that we’re feeling there is our sense of the beautiful – and the beautiful is partly that which pleases us because it helps us to make integrated sense of our lives.

What’s your fourth book?

We now turn to a book in which Kant starts to look in some depth at issues in the philosophy of religion. Again, the title is translated in various different ways in various different English versions. I know it as Religion Within the Boundaries of Mere Reason [1793]. We’ve already, several times, used the example of God’s existence as an example of something that Kant takes to be an article of faith. But, of course, the question arises: is that an article of faith that any of us ought to have? Is the existence of God something that we ought to have faith in? What role might a belief in God play in our lives and what role does Kant think that it has to play? Again, it turns out that his answer to that question has to do with this fundamental distinction between appearance and reality.

Part of Kant’s picture is that doing the right thing is basically doing the rational thing. When we were considering earlier the categorical imperative, in effect it was a recipe for directing your life in accordance with pure reason. At the level of things in themselves, we are free and rational agents and if that’s all there was to it, we would unfailingly do the right thing. We are agents who have freedom and the only thing that’s in a position to direct that freedom is our own rationality. If that was all there was to it, we would put reason to practical use just in the way that morality demands that we should. But there’s the world of appearances as well. We appear to ourselves in a certain way; we appear to ourselves as animal creatures with animal desires, with biological urges and suchlike. And, actually, what those animal desires and animal urges do is act as temptations to diverge from the path of true rationality. That’s why, in fact, people don’t always do what they should. Kant even leaves open the possibility that we find ourselves succumbing to non-rational impulses and doing the irrational thing all the time.

“God cannot do the right thing on our behalf. The only person who can ensure that I act morally is myself”

The next question is, obviously, what does any of that have to do with religion? Kant’s answer to that question is that, in a way, we need religion as a kind of non-rational prop – I say ‘non-rational’ rather than ‘irrational’ as this is outside the jurisdiction of reason altogether – to sustain our hope that all is not lost. This is because the picture can look like a pretty bleak one. There are these fundamental categorical imperatives bearing down on us all the while, and there are constant temptations to disobey them. It looks as if we might be forever falling prey to those temptations. It looks as if we’re in a rather miserable position, unfailingly doing the very opposite of what we should be doing. It would be easy to despair in a situation like that, and, after a while, just shrug your shoulders and say ‘Well, forget it. I’m no longer interested in the categorical imperative’. Going back to the imaginary conversation we were having earlier, it would be easy to become like the guy that says ‘I’m just not interested in becoming a better person’. But Kant is very keen not to fall into that despair. The thing that he thinks helps us to maintain some sort of grip on our situation is religion: I mean faith in a divine being who can offer us solace and help.

Ultimately, we’re left to our own devices: God cannot do the right thing on our behalf. The only person who can ensure that I act morally is myself. But a religious conviction can sustain my hope that, however badly I’ve behaved in the past, and whatever kind of a mess I might find myself in now, there is always going to be scope to extricate myself from that mess. Indeed, if I not only believe in a god but also in a kind of afterlife, there may be infinite scope for me to work myself back to a sort of perfection – the kind of perfection that should have been there right from the outset but, because I’m an imperfect being just like the rest of us, hasn’t been. So, it’s a very pragmatic conception of the importance of religion. But the title of the book is revealing as well: Religion Within the Boundaries of Mere Reason. We can see that what’s going on here is that religion is helping to underpin morality but it’s got a fundamentally subordinate role to play: it’s a prop. Religion is at the behest of morality; morality is not at the behest of religion.

Can I just clarify what you mean by a ‘prop’ there? In what way is religion propping up morality? I could work out that the categorical imperative demands that I never lie to anyone under any circumstances and that seems to me to be independent of any question of whether God exists.

That’s absolutely right. Religion doesn’t come into play there at all. I do not need any appeal to religion or any appeal to God to determine that it’s wrong to tell a lie. And actually, in fact, Kant himself is as clear about that as anybody. There is a point in the Groundwork where he addresses the famous ancient question, known as the Euthyphro dilemma, that exercised Plato as well: does God command what’s right because it’s right; or is what is right right because God commands it? There’s absolutely no doubt in Kant’s mind that it’s the first of those, not the second, that even God’s command is subject to the dictates of reason, and not vice versa. Morality is not in any way dependent on religion, insofar as that goes. If you’re interested in working out the difference between right and wrong, you could do it: you could give a quasi-mathematical demonstration that lying is always wrong, say. But, in any case, you wouldn’t even need to do that, since you could just consult your own conscience: Kant thinks we’re already well aware of the difference between right and wrong. As far as ascertaining the difference between right and wrong is concerned, morality has no need of religion.

“At a practical level, Kant thinks that religious thinking can help us avoid falling into a kind of nihilism”

The sense in which religion serves as a prop is the sense in which it helps us to put morality into practice. It’s one thing to determine what you should do in a given situation; it’s another thing to do it. The fact that each of us can look back over our past life and see the multitude of ways in which we’ve gone wrong means that there’s a very real serious practical danger that we will just succumb to despair and think ‘All is now lost. I can just see that I’m a grotty person. Why should I care any longer? My past life is already testimony to the fact that I’m fundamentally irrational. Here I am confronted with another choice about whether to do the right thing or not, but I’ve so often done the wrong thing in the past, why would one more misdeed make any difference?’ So it’s at a practical level that Kant thinks that religious thinking can help us avoid falling into that kind of nihilism.

Let’s move on to the last book, which is by one of your teachers: Peter Strawson. This is a very famous work about Kant called The Bounds of Sense (1966).

You’re quite right to point out that I was fortunate enough to be taught by Strawson as a graduate student. It was a wonderful and exhilarating experience. This is the one book on my list that isn’t by Kant himself, but any English speaker who studies the work of Kant will recognise the importance of this book, and, I think, will agree with me, even if it wouldn’t make it into their list of five, that it is not totally out of place there either. One of the reasons why I’ve included it is that it has quite a historical significance.

This is a book that was written in the 1960s by an Oxford philosopher at a time when Oxford philosophy in particular, and British philosophy more generally, and Anglo-American philosophy more generally still, were pretty much hostile to the sort of philosophy that dealt with the abstruse metaphysical questions that Kant deals with in the Critique of Pure Reason. Earlier in the century, in the 1920s and 1930s, there had been a movement known as Logical Positivism which dismissed a lot of this stuff as just meaningless gibberish. Later, Oxford philosophy was dominated by what came to be known as Ordinary Language Philosophy, whose adherents thought that the way to address philosophical questions was just to think in terms of what someone in the street would say about various different issues. All of this was very much antithetical to the kind of thing you find in the pages of the Critique of Pure Reason.

“The question for any exegete of Kant, or Strawson, for that matter, is the extent to which Strawson can have his Kantian cake and eat it”

What Strawson is trying to do in his book The Bounds of Sense is explore the Critique of Pure Reason. He takes this classic philosophical text and goes through it, explaining the nature of Kant’s project, defending it where he thinks it can be defended, criticising it where he thinks it can be criticised. But, above all, he wants to show its importance—its historical importance and its philosophical importance. And this was itself of historical and philosophical importance because, in a way, it was part of Strawson’s project to rehabilitate metaphysics. He went on to do very important metaphysical work of his own, almost always with a kind of Kantian inspiration. In this book, he’s explicitly articulating the Kantian inspiration for a lot of what you find elsewhere in his work.

I think I’m right in saying that one of the distinctive aspects of his approach is that he jettisons a lot of assumptions that Kant made.

Absolutely. He’s not afraid to criticise Kant where he thinks Kant can be criticised and, in fact, one of the most distinctive things about the book is that he wants to take issue with the thing that we kept describing as absolutely fundamental. Again and again, in this interview, I’ve come back to this distinction between appearance and reality and I’ve tried to emphasise how important it is for Kant. I’ve used the analogy of spectacles and emphasised that even that fact that we see things in spatio-temporal terms is part of these metaphorical spectacles. And, actually, the fact of the matter is that Strawson is deeply uncomfortable with that. He thinks that it’s a picture of the world that is ultimately just unintelligible. Indeed, it’s not just that it can be undermined by considerations that might be wheeled in from elsewhere. Strawson is even inclined to think that it undermines itself, that the very setting up of this picture involves transgressing the limits that Kant is so keen to draw. You can’t even think of yourself as wearing a pair of spectacles unless you’re able to take them off and look at them and investigate them as a pair of spectacles; but the whole point is that that’s precisely what we’re not supposed to be able to do.

“To have written about those topics with the depth of insight that he did is truly extraordinary”

So, Strawson sees the Critique as undermining itself in some fundamental ways. There’s something right at the heart of Kant’s project that Strawson wants to distance himself from. Nevertheless, in the course of defending this picture in the Critique of Pure Reason, Kant does all sorts of things, tackles all sorts of questions, and makes all sorts of philosophical moves. Strawson’s feeling is that there’s a lot there in the Critique of Pure Reason that can still be salvaged. The sheer fact that we’re trying to jettison this picture of a pair of spectacles doesn’t mean that we have to jettison all the arguments that Kant himself takes to support that picture. One of the things that you find Strawson doing in The Bounds of Sense is salvaging as much as he thinks can be salvaged, defending as much as he thinks can be defended, without this background metaphysical picture. The question for any exegete of Kant, or Strawson, for that matter, is the extent to which Strawson can have his Kantian cake and eat it.

Inevitably, as with anything else in philosophy, there are divided views about that, and some people think that what Kant presents us with is much more of a unified package than Strawson takes it to be and that if he really does want to defend Kant on certain points then, whether he likes it or not, he’s going to have to defend Kant on other points as well that he’s keen to reject.

You described Kant as the greatest philosopher ever. What is it that makes him so great?

One obvious answer to that question is the sheer combined breadth and depth of his work. If you think about just the range of issues that Kant dealt with – and we’ve seen something of that range in this interview – it’s staggering that one person could have written about so many topics. But to have written about those topics with the depth of insight that he did is truly extraordinary. So, that’s already the beginnings of an answer to the question. But I think even that is only the beginnings of the answer because the other really striking thing about Kant is that, despite the range, you’ve also got something that at first blush you might think would be incompatible with such a range, namely an incredible unity of concern. There are certain basic ideas that he keeps coming back to, including things that we’ve kept coming back to in this discussion.

Again and again, we’ve come back to this fundamental distinction between appearance and reality and we’ve talked about Kant’s constant concern with the exercise of reason and what we can and can’t do through a proper exercise of reason. And this idea that we’re fundamentally rational beings yet also limited in various ways, which itself shows up in this distinction between appearance and reality: that’s an idea that dominates the whole of his work. So, on the one hand, you’ve got this philosopher exploring issue after issue after issue that, on the face of it, might look like quite disparate issues; and, on the other hand, you’ve got this philosopher with a very profound preoccupation with certain questions that recur throughout all of these discussions. That combination of breadth, depth, and unity is a combination that you find in all the great philosophers – it’s not unique to Kant, but in my view it’s more marked in Kant than in any other philosopher.