A residual realism acknowledges the existence of an external world to which we are, as it were, causally connected. A residual realism has been taken for granted in the course of rejecting a stronger realism; indeed strong realism has been rejected as incompatible with the general outlines of residual realism. Historically, realism has developed in opposition to idealism; relativism has developed in opposition to rationalism. Realist usually adhere to a notion of truth as correspondence; indeed the correspondence theory of truth has been taken as close to a definition of realism in the philosophy of science. To the extent that it serves merely to facilitate specific predictions about appearances, realism is reduced to instrumentalism. Finitism may seem like the very antithesis of realism. It is incompatible with a correspondence theory of truth. It denies that concepts have extensions, even if they are putative natural kinds or real universals.