 According to Hilary Putnam, the metaphysical realist subscribes not just to the belief in a mind-independent world but also to the thesis that truth consists in a correspondence relation between words (or mental symbols) and things in that mind-independent world. Call this thesis correspondence truth (after Devitt 1991). More importantly, metaphysical realists aver that an ideal theory of the world could be radically false, Putnam contends: ‘radical’ in the sense that all (or almost all) of the theory’s theses could fail to hold. Such a global failure would result if we were to be ‘brains-in-a-vat’ our brains manipulated by mad scientists (or machines, as in the movie The Matrix) so as to dream of an external world that we mistake for reality. Call this thesis radical skepticism.