Kant and Skepticism (review)

Kant's theoretical philosophy is often read as a response to skeptical challenges raised by his predecessors. Yet Kant himself explicitly discusses skepticism in relatively few places in his published work, so Michael Forster's focused examination of Kant's relation to skepticism is a useful addition to the literature. Forster sets out to distinguish different types of skepticism to which Kant might be responding, determine what responses Kant offers, and evaluate the strength of those responses.

Perhaps the most valuable part of the book is the opening chapters, where Forster distinguishes three kinds of skepticism about metaphysics ("veil of perception" skepticism, Humean skepticism, and Pyrrhonian skepticism), and argues that it is a mistake to see Cartesian, veil of perception skepticism as a central target of Kant's. Though this point has been made before (e.g., by Karl Ameriks), insufficient attention to it has continued to result in misplaced criticisms of Kant's project, and Forster's forceful reminder is certainly welcome.

The other two types of skepticism, Forster argues, did play crucial roles in the development of Kant's metaphysical views, with each at some point rousing Kant from a self-described "dogmatic slumber." Forster claims that the 1766 Dreams of a Spirit Seer is a deliberately Pyrrhonian work, and that the equipollence worries about metaphysics described there persisted into the critical period in the form of the Antinomies. Now, while Forster is certainly right that Pyrrhonism focused on producing equally strong arguments for incompatible claims, this philosophical maneuver is hardly unique to that school of thought. Not every reductio ad absurdum is usefully labeled 'Pyrrhonian'. What was distinctive about the Pyrrhonian approach was not only its method, but its ultimate aim, namely, that of producing a general suspension of belief. Since Kant never had that as his ultimate aim, Forster's historical claim has limited plausibility. Forster's views about the influence of Humean skepticism on Kant, however, are more compelling. He argues that reflecting on Hume's arguments in the mid-1770s did not so much awaken Kant to the challenges of accounting for a priori cognition as give him a deeper appreciation of those challenges. Though this interpretation implies that Kant's statement in the Prolegomena about Hume's influence is a gross exaggeration, the fact that there is no unambiguous Hume-inspired philosophical revolution in the pre-critical texts supports this implication of Forster's view.

Having located what he takes to be the skeptical concerns Kant had in mind, Forster turns to describing how the critical philosophy attempted to respond on behalf of metaphysics. He claims that Kant reconceived metaphysics as (i) dealing with objects of possible experience instead of with the supersensuous realm, while (ii) investigating just those aspects of the world that are constituted by our own minds, and (iii) requiring systematicity. Such a reconception, Forster claims, was intended to save some parts of metaphysics (e.g., the causal principle) while allowing the skeptical challenges to maintain force against others (e.g., doctrines concerning God) by providing a basis for transcendental arguments. These arguments, Forster holds, assume the actuality of experience and conclude by identifying necessary conditions for experience, conditions that in turn require the truth of transcendental idealism.

The second half of the book is devoted to a critique of Kant's position, which Forster holds is ultimately unsatisfactory. He offers several criticisms, of which two are particularly important. The first is a new version of an argument familiar from Jonathan Bennett's 1966 book: Kant attempts to explain our synthetic a priori cognition using claims concerning what is necessary for experience. These latter claims must be a priori, but are they supposed to be analytic or synthetic? If synthetic, then no explanatory progress has been made. But if they are analytic (e.g., analyses of the concept of experience), then the resulting claims, if true, could themselves only be analytic. Forster's second main criticism is that Kant uncritically presupposed both the reality of subjective experience and the validity of...