Henry Allison criticizes and rejects naturalism because the idea of freedom is constitutive of rational spontaneity, which alone enables and entitles us to judge or to act rationally, and only transcendental idealism can justify our acting under the idea of freedom. Allison’s critique of naturalism is unclear because his reasons for claiming that free rational spontaneity requires transcendental idealism are inadequate and because his characterization of Kant’s idealism is ambiguous. Recognizing this reinforces the importance of the question of whether only (...) transcendental idealism “can ground the right to the conceptual space” that we occupy when thinking spontaneously or acting under the idea of freedom. Only with a clear answer to this question can Kant’s idea of freedom provide a basis for assessing today’s naturalist orthodoxy. (shrink)