Abstract

Moral realism faces two worries: How can we have knowledge of moral norms if they are independent of us, and why should we care about them if they are independent of rational activities they govern? Kantian constitutivism tackles both worries simultaneously by claiming that practical norms are constitutive principles of practical reason. In particular, on Stephen Engstrom’s account, willing involves making a practical judgment. To will well, and thus to have practical knowledge (i.e., knowledge of what is good), the content of one’s will needs to conform to the formal presuppositions of practical knowledge. Practical norms are thus constitutive of practical knowledge. However, I will argue that the universality principles from which Engstrom derives the formal presuppositions of practical knowledge are reflectively and psychologically unavailable. As a result, they cannot help Kantian constitutivism provide an answer to moral realism's worries.