Abstract

Could each and every one of us, instead of interacting with actual objects, really be brains in a vat? In the first chapter of his new book, Reason, Truth and History, Professor Putnam raises this and related questions with the aim of undermining what he calls the “metaphysical realist” or “externalist” conception of reality. Putnam describes metaphysical realism as a view which holds that the world consists in “some fixed totality of mind-independent objects”; truth on this view amounts to a correspondence between words or thoughts and these objects. Putnam contrasts metaphysical realism with a doctrine which he names “internalism” and calls on Kant to explicate its basic ideas. Putnam claims that Kant was the first philosopher to see clearly the difficulties inherent in metaphysical realism. The doctrine of transcendental idealism, says Putnam, represents Kant’s attempt to avoid externalism. But is Kant’s doctrine really just an early version of Putnam’s internalism? In this paper I shall argue that it is not. Although Kant obviously rejects the position Putnam calls “externalism,” I shall try to show that Kant’s metaphysical theory is distinct from internalism. Kant couples transcendental idealism with a second doctrine of empirical realism, and this enables Kant to circumvent both the internalist’s coherence theory of truth as well as a simple-minded correspondence theory. To be sure, one of Kant’s major concerns is to argue against the possibility of knowing things-in-themselves; Kant thus maintains, as Putnam correctly points out, that the nature of perceivers must figure in the nature of what is perceived. But this is not to say, as Putnam implies, that there is no mind-independent reality in Kant’s theory. On the contrary, Kant’s Refutation of Idealism—an argument that strikingly resembles the first horn of Putnam’s brain-in-a-vat dilemma—is designed to establish the existence of “matter,” which is Kant’s general term for what we might call the “external” or the “mind-independent.” Kant does argue that the perception of matter must accord with space and time, the two forms of sensibility, and this is the source of his transcendental idealism. But if we take this to mean that there cannot be anything independent of our minds or of our conceptual schemes, then we miss the point of Kant’s double doctrine of transcendental idealism and empirical realism, which is intended to avoid a coherence-only theory of truth while yet affirming that objects are knowable only as appearances. Putnam, by running together a number of Kantian notions, misrepresents Kant’s position and thus fails to see that Kant does offer an alternative to both metaphysical realism and internalism. I shall begin my defense of the claim that Kant does provide a third alternative by exploring more fully the debate between Putnam and the externalist concerning the BV dilemma. I shall then explore the Refutation of Idealism to support my claim that Putnam’s internalism is distinct from transcendental idealism. We shall see in section IV that in interpreting Kant on transcendental idealism Putnam makes two crucial mistakes which lead him to equate internalism with transcendental idealism. The result of these mistakes is discussed in section V.