 However, as Onora O’Neill points out in a celebrated essay (1989: Ch. 1), the claims Kant has now made about practical reason actually commit him to a third claim concerning reason’s “common principle.” Kant has argued that the Categorical Imperative is the supreme principle of practical reason. He has also argued that practical reason has primacy over theoretical reason. It follows, therefore, that the Categorical Imperative is the supreme principle of reason.—To be sure, Kant never states this conclusion explicitly. But there are reasons for thinking that this ought to have been his view, and in some places he comes very close to such a claim. (Rescher 2000 (Ch. 9) similarly emphasizes the “isomorphism” of theoretical and practical reason. Rauscher 1998 notes that Kant’s own use of the “primacy” of practical reason is more limited than O’Neill’s, while endorsing O’Neill’s overall case.)