Philosophical naturalism, considered in general, is not a unified doctrine but a broad label applied both to methodological stances (e.g., "The methods of philosophy are continuous with those of empirical science") and to substantive positions (e.g., "For a belief to be epistemically warranted is for it to be the product of a certain kind of causal process"). The two are often combined, as when a naturalistic interpretation of a given domain of discourse is justified as "the best explanation" of associated practices. However, the two are in principle independent. In the moral case, for example, it has been argued that a projectivist or noncognitivist interpretation gives a better explanation of moral practice than any substantive naturalism (Blackburn 1984, Gibbard 1990).

But what makes a method or interpretation naturalistic? Attempts to give an explicit definition have largely been abandoned in favor of pointing. Roughly, naturalistic methods are...