It is notoriously difficult for philosophers to explain, to people unfamiliar with their discipline, what it is that they do. "I teach." "What do you teach?" "Philosophy." If we were to say "physics" or "history" or even "psychology," our interlocutors would think they had no problem in understanding our profession, but the answer "philosophy" almost always provokes incomprehension and unease. We can evade the issue by saying that as philosophers we study and explain the works of writers like Plato, Aristotle, and Descartes, but this clarification merely puts off the reckoning by one step; what is it that those people have written about?
One reason for this difficulty is that philosophy does not have an identifiable, partial domain as its subject matter. It attempts to think about the widest context, that which is not differentiated as one part from other parts. If it were a partial discipline, it could at least be vaguely comprehended as being something other than, say, mathematics or sociology, something that studies this domain as opposed to that. Philosophy does not define itself by such partialization, however. It leaves nothing out, and hence leaves us without the contrasting foil that would allow us to say what it is. People who are unfriendly to philosophy suspect that it is inflated, presumptuous, and nonrigorous; this feeling is an inadequate but understandable way of recognizing the fact that philosophy is not defined by being partial.
A second reason for the difficulty in saying what philosophy is lies in its method. The method of philosophical thinking is not obvious; we think we have some idea of the manner in which, say, physicists or linguists proceed in their inquiries, but how do philosophers proceed in theirs? It is hard to say; philosophy appears to be an arcane intellectual discipline, a form of thinking whose ways are esoteric and obscure. How does it come to know what it thinks it knows?
I wish to help clarify what philosophy is by discussing its method. I will suggest that the form of thinking proper to philosophy is extremely simple: philosophy is the intellectual activity that works with distinctions. Its method is the making and the questioning of distinctions. Philosophy explains by distinguishing. This does not mean that philosophy just asserts distinctions and lets it go at that; rather, it works with distinctions, it brings them out and dwells on them, dwells with them, showing how and why the things that it has distinguished must be distinguished one from the other. Furthermore, since it essentially works with distinctions, philosophy sometimes will show that a certain distinction that has been proposed or taken for granted is unreal or invalid. Philosophy sometimes obliterates distinctions. Such rejection of distinctions, however, is the negative and refutational aspect of philosophy's work; its positive success consists in achieving a distinction that clarifies a situation or a controversy, a distinction that brings out the nature of a thing. Furthermore, even when denying a distinction, philosophy proceeds by making other distinctions that allow it to deny the one in question.
Let me give some illustrations before proceeding to my argument. My claim is that philosophy does not just discuss and define, say, human freedom; rather, it will examine how responsible action is to be distinguished from the nonresponsible. It does not just talk about politics; it will distinguish the political from the economic and from the familial. It does not just examine the nature of numbers; it will show the distinction between the mathematical and the physical, between the mathematical and the logical, between the numerical and the merely collected. Philosophy does not just investigate substance; it develops the difference between the substantial and the coincidental. It does not simply investigate what propositions are; it clarifies the distinctions between propositions and states of affairs, and between propositions and the mental activities that grasp them. …