This book is for people who want to think about the big themes: knowledge, reason, truth, mind, freedom, destiny, identity, God, goodness, justice. These are not the hidden preserve of specialists. They are things that men and women wonder about naturally, for they structure the ways we think about the world and our place in it. They are also themes about which thinkers have had things to say. In this book I try to introduce ways of thinking about the big themes. I also introduce some of the things thinkers have had to say about them. If readers have absorbed this book, then they should be on better terms with the big themes. And they should be able to read many otherwise baffling major thinkers with pleasure and reasonable understanding.

The word 'philosophy' carries unfortunate connotations: impractical, unworldly, weird. I suspect that all philosophers and philosophy students share that moment of silent embarrassment when someone innocently asks us what we do. I would prefer to introduce myself as doing conceptual engineering. For just as the engineer studies the structure of material things, so the philosopher studies the structure of thought. Understanding the structure involves seeing how parts function and how they interconnect. It means knowing what would happen for better or worse if changes were made. This is what we aim at when we investigate the structures that shape our view of the world. Our concepts or ideas form the mental housing in which we live. We may end up proud of the structures we have built. Or, we may believe that they need dismantling and starting afresh. But first, we have to know what they are.

The book is self-standing and does not presuppose that the reader has any other resources. But it could be augmented. For example, it could be read alongside some of the primary source materials from which I frequently quote. These are readily-available classics, such as Descartes' Meditations, or Berkeley's Three Dialogues, or Hume's Enquiry concerning Human Understanding, or his Dialogues Concerning Natural Religion. But it can equally well be read on its own without the text to hand. And after finishing it, the reader should pick up the classics, and other things like logic texts or writings on ethics, with a mind prepared.

What are we to think about?

Here are some questions any of us might ask about ourselves: What am I? What is consciousness? Could I survive my bodily death? Can I be sure that other peoples' experiences and sensations are like mine? If I can't share the experience of others, can I communicate with them? Do we always act out of self-interest? Might I be a kind of puppet, programmed to do the things that I believe I do out of my own free will?

Here are some questions about the world: Why is there something and not nothing? What is the difference between past and future? Why does causation run always from past to future, or does it make sense to think that the future might influence the past? Why does nature keep on in a regular way? Does the world presuppose a Creator? And if so, can we understand why he (or she or they) created it?

Finally here are some questions about ourselves and the world. How can we be sure that the world is really like we take it to be? What is knowledge, and how much do we have? What makes a field of inquiry a science? (Is psychoanalysis a science? Is economics?) How do we know about abstract objects, like numbers? How do we know about values and duties? How are we to tell whether our opinions are objective, or just subjective?

                  The queer thing about these questions is that not only are they baffling at first sight, but they also defy simple processes of solution. If someone asks me when it is high tide, I know how to set about getting an answer. There are authoritative tide tables I can consult. I may know roughly how they are produced. And if all else fails, I could go and measure the rise and fall of the sea myself. A question like this is a matter of experience: an empirical question. It can be settled by means of agreed procedures, involving looking and seeing, making measurements or applying rules that have been tested against experience and found to work. The questions of the last paragraphs are not like this. They seem to require more reflection. We don't immediately know where to look. Perhaps we feel we don't quite know what we mean when we ask them, or what would count as getting a solution. What would show me, for instance, whether I am not after all a puppet, programmed to do the things I believe I do freely? Should we ask scientists who specialize in the brain? But how would they know what to look for? How would they know when they had found it? Imagine the headline: 'Neuroscientists discover human beings not Puppets'. How?

                  So what gives rise to such baffling questions?            

                  In a word, self-reflection. Human beings are relentlessly capable of reflecting on themselves. We might do something out of habit, but then we can begin to reflect on the habit. We can habitually think things, and then reflect on what we are thinking. We can ask ourselves (or sometimes we get asked by other people) whether we know what we are talking about. To answer that we need to reflect on our own positions, our own understanding of what we are saying, our own sources of authority. We might start to wonder whether we know what we mean. We might wonder whether what we say is 'objectively' true, or merely the outcome of our own perspective, or our own 'take' on a situation. Thinking about this we confront categories like knowledge, objectivity, truth, and we may want to think about them. At that point we are reflecting on concepts and procedures and beliefs that we normally just use. We are looking at the scaffolding of our thought, and doing conceptual engineering.

                  This point of reflection might arise in the course of quite normal discussion. An historian, for example, is more or less bound at some point to ask what is meant by 'objectivity' or 'evidence', or even 'truth', in history. A cosmologist has to pause from solving equations with the letter 't' in them, and ask what is meant, for instance, by the flow of time or the direction of time or the beginning of time. But at that point, whether they recognize it or not, they become philosophers. And they are beginning to do something that can be done well or badly. The point is to do it well.

How is philosophy learned? A better question is: how can thinking skills be acquired? The thinking in question involves attending to basic structures of thought. This can be done well or badly, intelligently or ineptly. But doing it well is not primarily a matter of acquiring a body of knowledge. It is more like playing the piano well. It is a 'knowing how' as much as a 'knowing that'. The most famous philosophical character of the classical world, the Socrates of Plato's dialogues, did not pride himself on how much he knew. On the contrary, he prided himself on being the only one who knew how little he knew (reflection, again). What he was good at-supposedly, for estimates of his success differ-was exposing the weaknesses of other peoples' claims to know. To process thoughts well is a matter of being able to avoid confusion, detect ambiguities, keep things in mind one at a time, make reliable arguments, become aware of alternatives, and so on.

To sum up: our ideas and concepts can be compared with the lenses through which we see the world. In philosophy the lens is itself the topic of study. Success will be a matter not of how much you know at the end, but of what you can do when the going gets tough: when the seas of argument rise, and confusion breaks out. Success will mean taking seriously the implications of ideas.

What is the Point?

It is all very well saying that, but why bother? What's the point? Reflection doesn't get the world's business done. It doesn't bake bread or fly aeroplanes. Why not just toss the reflective questions aside, and get on with other things? I shall sketch three kinds of answer: high ground, middle ground, and low ground.

                  The high ground questions the question-a typical philosophical strategy, because it involves going up one level of reflection. What do we mean when we ask what the point is? Reflection bakes no bread, but then neither do architecture, music, art, history, or literature. It is just that we want to understand ourselves. We want this for its own sake, just as a pure scientist or pure mathematician may want to understand the beginning of the universe, or the theory of sets, for its own sake, or just as a musician might want to solve some problem in harmony or counterpoint just for its own sake. There is no eye on any practical applications. A lot of life is indeed a matter of growing more hogs, to buy more land, so we can grow more hogs, so that we can buy more land... The time we take out, whether it is to do mathematics or music, or to read Plato or Jane Austen, is time to be cherished. It is the time in which we cosset our mental health. And our mental health is just good in itself, like our physical health. Furthermore there is after all a payoff in terms of pleasure. When our physical health is good, we take pleasure in physical exercise, and when our mental health is good, we take pleasure in mental exercise.

                  This is a very pure-minded reply. The problem with it is not that it is wrong. It is just that it is only likely to appeal to people who are half convinced already-people who didn't ask the original question in a very aggressive tone of voice.

So here is a middle-ground reply. Reflection matters because it is continuous with practice. How you think about what you are doing affects how you do it, or whether you do it at all. It may direct your research, or your attitude to people who do things differently, or indeed your whole life. To take a simple example, if your reflections lead you to believe in a life after death, you may be prepared to face persecutions that you would not face if you became convinced-as many philosophers are-that the notion makes no sense. Fatalism, or the belief that the future is fixed whatever we do, is a purely philosophical belief, but it is one that can paralyze action. Putting it more politically, it can also express an acquiescence with the low status accorded to some segments of society, and this may be a payoff for people of higher status who encourage it.

Let us consider some examples more prevalent in the West. Many people reflecting on human nature think that we are at bottom entirely selfish. We only look out for our own advantage, never really caring about anyone else. Apparent concern disguises hope of future benefit. The leading paradigm in the social sciences is 'homo economicus'-economic man. Economic man looks after himself, in competitive struggle with others. Now, if people come to think that we are all, always, like this, their relations with each other become different. They become less trusting, less cooperative, more suspicious. This changes the way they interact, and they will incur various costs. They will find it harder, and in some circumstances impossible, to get cooperative ventures going: they may get stuck in what the philosopher Thomas Hobbes memorably called 'the war of all against all'. In the market place, because they are always looking out to be cheated, they will incur heavy transaction costs. If my attitude is that 'a verbal contract is not worth the paper it is written on', I will have to pay lawyers to design contracts with penalties, and if I will not trust the lawyers to do anything except just enough to pocket their fees, I will have to get the contracts checked by other lawyers, and so on. But all this may be based on a philosophical mistake-looking at human motivation through the wrong set of categories, and hence misunderstanding its nature. Maybe people can care for each other, or at least care for doing their bit or keeping their promises. Maybe if a more optimistic self-image is on the table, people can come to live up to it. Their lives then become better. So this bit of thinking, getting clear about the right categories with which to understand human motivation, is an important practical task. It is not confined to the study, but bursts out of it.

                  Here is a very different example. The Polish astronomer Nicholas Copernicus reflected on how we know about motion. He realized that how we perceive motion is perspectival: that is, whether we see things as moving is the result of how we ourselves are placed and in particular whether we ourselves are moving (we have mostly been subject to the illusion in trains or airports, where the next door train or aeroplane seems to move off, and then we realize with a jolt that it is we who are moving. But there were fewer everyday examples in the time of Copernicus). So the apparent motions of the stars and planets might arise because they are not moving as they appear to do, but we observers move. And this is how it turned out to be. Here reflection on the nature of knowledge-what philosophers call an epistemological inquiry, from the Greek episteme, meaning knowledge-generated the first spectacular leap of modern science. Einstein's reflections on how we know whether two events are simultaneous had the same structure. He realized that the results of our measurements would depend upon the way we are travelling compared to the events we are clocking. This led to the Special Theory of Relativity (and Einstein himself acknowledged the importance of preceding philosophers in sensitizing him to the epistemological complexities of such a measurement).

                  For a final example, we can consider a philosophical problem many people get into when they think about mind and body. Many people envisage a strict separation between mind as one thing and body as a different thing. When this seems to be just good common sense it can begin to infect practice in quite insidious ways. For instance, it begins to be difficult to see how these two different things interact. Doctors might then find it almost inevitable that treatments of physical conditions that seek mental or psychological causes will fail. They might find it next to impossible to see how messing with someone's mind could possibly cause changes in the complex physical system that is their body. After all, good science tells us that it takes physical and chemical causes to have physical and chemical effects. So we might get an a priori, armchair certainty that one kind of treatment (say, drugs and electric shocks) has to be right and others (such as treating patients humanely, counseling, analysis) are 'wrong': unscientific, unsound, bound to fail. But this certainty is premised not on science but on a false philosophy. A better philosophical conception of the relation between mind and body changes it. A better conception should enable us to see how there is nothing surprising in the fact of mind-body interaction. It is the most commonplace fact, for instance, that thinking of some things (mental) can cause people to blush (physical). Thinking of a future danger can cause all kinds of bodily changes: hearts pound, fists clench, guts constrict. By extrapolation there should be nothing difficult to comprehend about a mental state such as cheerful optimism affecting a physical state like the disappearance of spots or even the remission of a cancer. It becomes a purely empirical fact whether such things happen. The armchair certainty that they could not happen is itself revealed as dependent on bad understanding of the structures of thought, or in other words bad philosophy, and is in that sense unscientific. And this realization can change medical attitudes and practice for the better.

                  So the middle-ground answer reminds us that reflection is continuous with practice, and our practice can go worse or better according to the value of our reflections. A system of thought is something we live in, just as much as a house, and if our intellectual house is cramped and confined, we need to know what better structures are possible.

The low-ground answer merely polishes this point up a bit, not in connection with nice clean subjects like economics or physics, but down in the basement where human life is a little less polite. One of the series of satires etched by the Spanish painter Goya is entitled 'The Sleep of Reason produces Monsters'. Goya believed that many of the follies of mankind resulted from the 'sleep of reason'. There are always people telling us what we want, how they will provide it, and what we should believe. Convictions are infectious, and people can make others convinced of almost anything. We are typically ready to believe that our ways, our beliefs, our religion, our politics are better than theirs, or that our God-given rights trump theirs or that our interests require defensive or pre-emptive strikes against them. In the end, it is ideas for which people kill each other. It is because of ideas about what the others are like, or who we are, or what our interests or rights require, that we go to war, or oppress others with a good conscience, or even sometimes acquiesce in our own oppression by others. When these beliefs involve the sleep of reason, critical awakening is the antidote. Reflection enables us to step back, to see our perspective on a situation as perhaps distorted or blind, at the very least to see if there is argument for preferring our ways, or whether it is just subjective. Doing this properly is doing once more piece of conceptual engineering.

Since there is no telling in advance where it may lead, reflection can be seen as dangerous. There are always thoughts that stand opposed to it. Many people are discomfited, or even outraged, by philosophical questions. Some are fearful that their ideas may not stand up as well as they would like if they start to think about them. Others may want to stand upon the 'politics of identity', or in other words the kind of identification with a particular tradition, or group, or national or ethnic identity that invites them to turn their back on outsiders who question the ways of the group. They will shrug off criticism: their values are 'incommensurable' with the values of outsiders. They are to be understood only by brothers and sisters within the circle. People like to retreat to within a thick, comfortable, traditional set of folkways, and not to worry too much about their structure, or their origins, or even the criticisms that they may deserve. Reflection opens the avenue to criticism, and the folkways may not like criticism. In this way, ideologies become closed circles, primed to feel outraged by the questioning mind.

                  For the last two thousand years the philosophical tradition has been the enemy of this kind of cosy complacency. It has insisted that the unexamined life is not worth living. It has insisted on the power of rational reflection to winnow out bad elements in our practices, and to replace it with better ones. It has identified critical self-reflection with freedom, the idea being that only when we can see ourselves properly can we obtain control over the direction in which we would wish to move. It is only when we can see our situation steadily and see it whole that we can start to think what to do about it. Marx said that previous philosophers had sought to understand the world, whereas the point was to change it-one of the silliest famous remarks of all time (and absolutely belied by his own intellectual practice). He would have done better to add that without understanding the world, you will know little about how to change it, at least for the better. Rosencrantz and Guildenstern admit that they cannot play on a pipe but they seek to manipulate Hamlet. When we act without understanding, the world is well prepared to echo Hamlet's response: 's'blood, do you think I am easier to be played on than a pipe?'

There are academic currents in our own age that run against these ideas. There are people who question the very notion of truth, or reason, or the possibility of disinterested reflection. Mostly, they do bad philosophy, often without even knowing that this is what they are doing: conceptual engineers who cannot draw a plan, let alone design a structure. We return to see this at various points in the book, but meanwhile I can promise that this book stands unashamedly with the tradition and against any modern, or postmodern, scepticism about the value of reflection.

                  Goya's full motto for his etching is 'Imagination abandoned by reason produces impossible monsters: united with her, she is the mother of the arts and the source of their wonders'. That is how we should take it to be.