Contemporary philosophical "realism" is not a single thesis but rather a diverse family of positions, unified chiefly by their invocation of certain characteristic images and metaphors. The realist about a region of discourse typically holds, for example, that our central commitments in the area describe a world that exists anyway, independently of us; that cognition in the area is a matter of detection rather than projection or constitution; and that the objects of the discourse are real things and not just linguistic or social constructions. Debates over realism defined in terms such as these persist in nearly every philosophical subdiscipline: from ethics and the philosophy of mind to the philosophy of science and the philosophy of mathematics. (Although it is common to describe a philosopher as a realist or nonrealist tout court, realism in one area is generally independent of realism in another, and advocates of...