Physicists study matter, motion, and energy. Chemists study substances and their forms of combination, interaction and decomposition. Biologists study living things. And so forth. But what is it that philosophers study? One answer common throughout the ages is that as physicists study physics, philosophers study meta-physics. Philosophers, or at any rate the deepest of philosophers, we are told, are meta-physicists. Physicists study the contingencies of the world – things that happen to be so. Meta-physicists study the essential, necessary features of all possible worlds.



This reply is unconvincing for a number of reasons. For one thing, if it were the case, it would need a great deal of explaining to vindicate philosophy. For while physics has produced libraries of well established results (and chemistry and biology yet more libraries), we can look in vain for trustworthy books entitled Established Truths of Metaphysics or A Handbook of Philosophical Facts.



Moreover, there is more than an air of absurdity to the thought that chemists discover that water consists of H2O, and that philosophers then discover that this is not a contingent truth, but a necessary one; or that physicists discover that E=mc2, and meta-physicists then discover that this is true in all possible worlds.

Finally, if we look at the kinds of results that meta-physicists do produce, it is evident that they are little more than paradox (time is unreal; solid objects are not really solid; coloured objects are not really coloured), absurdity (we cannot know the thoughts or intentions of another; we are nothing more than a bundle of perceptions) and systematically contested to boot (there are or are not universals; moral truths are all absolute or all relative). So let us discard this foolishness.



Metaphysics is an illusion that besets philosophers (and philosophically-minded scientists) from generation to generation, which it is the task of good philosophy to dispel. But although periodic fumigation is recurrently necessary for intellectual health, what else is there for philosophy to do? What can it achieve? In the sense in which the sciences have a subject matter, it seems, philosophy has none. In the sense in which the sciences construct theories that are confirmed or infirmed by experiment or observation, there are obviously no theories in philosophy. In the sense in which the sciences make discoveries about the world around us, philosophy clearly does not. So what is its task?

We must challenge the thought that philosophy aims to contribute to human knowledge of the world. Its task is to resolve philosophical problems. The characteristic feature of philosophical problems is their non-empirical, a priori character: no scientific experiment can settle the question of whether the mind is the brain, what the meaning of a word is, whether human beings are responsible for their deeds (i.e. have free will), whether trees falling on uninhabited desert islands make any noise, what makes necessary truths necessary. All these, and many hundreds more, are conceptual questions. They are not questions about concepts (philosophy is not a science of concepts). But they are questions that are to be answered, resolved or dissolved by careful scrutiny of the concepts involved.



The only way to scrutinise concepts is to examine the use of the words that express them. Conceptual investigations are investigations into what makes sense and what does not. And, of course, questions of sense precede questions of empirical truth – for if something makes no sense, it can be neither true nor false. It is just nonsense – not silly, but rather: it transgresses the bounds of sense. Philosophy patrols the borders between sense and nonsense; science determines what is empirically true and what is empirically false. What falsehood is for science, nonsense is for philosophy.

Let me give you a simple example or two. When psychologists and cognitive scientists say that it is your brain that thinks rather than nodding your head and saying, “How interesting! What an important discovery!”, you should pause to wonder what this means. What, you might then ask, is a thoughtful brain, and what is a thoughtless one?



Can my brain concentrate on what I am doing, or does it just concentrate on what it is doing? Does my brain hold political opinions? Is it, as Gilbert and Sullivan might ask, a little Conservative or a little Liberal? Can it be opinionated? Narrow-minded? What on earth would an opinionated and narrow-minded brain be? Just ask yourself: if it is your brain that thinks, how does your brain tell you what it thinks? And can you disagree with it? And if you do, how do you tell it that it is mistaken, that what it thinks is false? And can your brain understand what you say to it? Can it speak English? If you continue this line of questioning you will come to realise that the very idea that the brain thinks makes no sense. But, of course, to show why it makes no sense requires a great deal more work.



Another example. There is a letter once attributed to Mozart in which he wrote that sometimes, when in the fever of creativity, he could hear the whole concerto that he was composing in a flash – all he then had to do was to write it down. On hearing this tale, you may nod your head wisely and think: “what an amazing genius! How could he possibly do such a thing?”

Roger Penrose, a distinguished scientist and mathematician, reflecting on the same letter, thought that we shall only be able to understand this remarkable phenomenon when we have an adequate theory of quantum gravity and a better understanding of time. “Ah,” you may think, “how true! How amazing!”



But you should pause, not to wonder whether what Mozart allegedly said is true, nor to wonder how he could do something so amazing, but to wonder whether this form of words means anything at all. After all, if he could hear the whole concerto in his imagination in a flash, all he would have imagined hearing was a crashing chord, not a concerto! In fact, the famous letter is a forgery. But that doesn’t matter. What matters is that the only sense that can be given to the phrase “hearing the concerto in one’s imagination in a flash” is that it means that he suddenly realised that he knew how to complete the concerto he was writing, not that he had already completed it in his imagination. The sudden dawning of an ability is not the same as its high-speed exercise, and to have a Eureka experience is not to rehearse the whole solution to a problem in a flash, but to know that one can rehearse the whole solution, on request, at normal speed.

So, why study philosophy?



There are many reasons, and many different kinds of reason. At a very general level, it is a unique technique for tackling conceptual questions that occur to most thinking people: questions concerning the existence of God, of an afterlife, and of free will. Also questions concerning human nature: what is the mind? How is the mind related to the body? Do we have a soul?



For although these look as if they are factual questions, they are not. They are purely conceptual questions that are to be resolved by conceptual inquiry. Philosophy also gives us techniques for handling fundamental methodological problems concerning explanations of human behaviour: what is the difference between being caused to do something, being made to do something, and acting for a reason? These in turn are pivotal for understanding the rights and wrongs of allocating responsibility. And philosophy is the sole subject that confronts questions about how we ought to live, what kind of society we ought to aspire to, and what system of laws befits rational beings living under the rule of law.

At a more specialised level, philosophy is a technique for examining the results of specific sciences for their conceptual coherence, and for examining the explanatory methods of the different sciences – natural, social and human. The sciences are no more immune to conceptual confusion than is any other branch of human thought. Scientists themselves are for the most part ill-equipped to deal with conceptual confusions.

One great task of philosophy is to function as a Tribunal of Sense before which scientists may be arraigned when they transgress the bounds of sense. For when a neuroscientist tells us that the mind is the brain or that thinking is a neural process; when an economist tells us that to act rationally is to pursue one’s desire-satisfaction, or that human felicity is the maximization of utility; when a psychologist claims that autism is the consequence of the neonates’ failure to develop a theory of mind, then we need philosophy to constrain science run amok.



The history of philosophy is a capital part of the history of ideas. To study the history of philosophy is to study an aspect of the intellectual life of past societies, and of our own society in the past. It makes a crucial contribution to the understanding of the history of past European societies. Equally, to understand our contemporary forms of thought, the ways in which we look at things, the study of the history of philosophy is essential. For we cannot know where we are, unless we understand how we got here.

The study of philosophy cultivates a healthy scepticism about the moral opinions, political arguments and economic reasonings with which we are daily bombarded by ideologues, churchmen, politicians and economists. It teaches one to detect ‘higher forms of nonsense’, to identify humbug, to weed out hypocrisy, and to spot invalid reasoning. It curbs our taste for nonsense, and gives us a nose for it instead. It teaches us not to rush to affirm or deny assertions, but to raise questions about them.



Even more importantly, it teaches us to raise questions about questions, to probe for their tacit assumptions and presuppositions, and to challenge these when warranted. In this way it gives us a distance from passion-provoking issues – a degree of detachment that is conducive to reason and reasonableness.