Kant on Transcendental Illusion and the Argument from Spinozism

Abstract In the Critique of Practical Reason , Kant argues that rejection of the ideality of space and time leads, via some additional assumptions, to Spinozism. Understanding this ambitious argument requires understanding, inter alia, what Kant means by ‘Spinozism,’ what assumptions figure in the argument, and how these assumptions are supposed to be connected to the ideality of space and time. While my interpretation differs from others on numerous points, one crucial difference lies in my account of the key assumptions. As I argue, Kant takes them to arise naturally from human reason itself. The most crucial and substantive among them concern reason’s naturally formed Ideas of, respectively, absolute space, absolute time, and God. More precisely, Kant takes these claims to be products of a natural transcendental illusion, and he holds that human reason under the spell of transcendental realism is unable to expose them as illusory and unwarranted.