At one level, the continuity of philosophy and empirical science is uncontentious. Many philosophical problems arise because of apparent tensions or conflicts within the assumptions which empirical evidence recommends to us. The most obvious examples are issues in the philosophy of science, such as problems about the interpretation of quantum mechanics, or the asymmetry of time, or the logic of natural selection. But other less specialist philosophical questions, like the existence of free will, also arise because of difficulties raised by empirical assumptions (in particular, in this case, by assumptions about the extent to which human beings are subject to the same laws of nature as the rest of the
world).

This is not to say that these philosophical issues are no different from the kinds of issues normally addressed by natural scientists. Philosophical problems are characterized by a special kind of difficulty, a difficulty which means that they cannot be solved, as scientific problems normally are, simply by the uncovering of further empirical evidence. Rather they require some conceptual unravelling, a careful unpicking of implicit ideas, often culminating in the rejection of assumptions we didn’t realize we had. But, still, despite these differences, there is clearly a sense in which philosophical thinking of this kind is part and parcel of the construction of scientific theories. Even if there is no direct involvement with empirical evidence, the task of the philosophers is to bring coherence and order to the total set of assumptions we use to explain the empirical world.

The question at issue is whether all philosophical theorizing is of this kind. Naturalists will say that it is. Those with a more traditional attitude to philosophy will disagree. These traditionalists will allow, of course, that some philosophical problems, problems in applied philosophy, as it were, will fit the above account. But they will insist that when we turn to “first philosophy”, to the investigation of such fundamental categories of thought and knowledge, then philosophy must proceed independently of science.

Naturalists will respond that there is no reason to place even first philosophy outside science. They will point out that even the investigation of basic topics like thought and knowledge needs to start somewhere, with some assumptions about the nature of the human mind and its relation to the rest of reality. Without any assumptions to work from, investigation would be paralyzed. And the obvious strategy, naturalists will argue, is to begin with our empirically best-attested theories of the mind and its relation to reality, and use these as a framework within which to raise and resolve philosophical difficulties, in the way outlined above.

Traditionalists will counter that we are not entitled to any empirically-based assumptions until we have somehow established the legitimacy of empirical knowledge by independent means. Maybe, they will concede, we need some assumptions of some sort to start with. But, on pain of pre-empting important philosophical questions, they had better be assumptions we can establish by such arguably incontrovertible methods as introspection, conceptual analysis, or deduction, and not assumptions which rest on the all-too-questionable principles of empirical investigation.