Derek Parfit argues that everyone ought to follow the principles whose universal acceptance would make things go best. I present a counterexample: a world in which no one's moral beliefs have any motivating force. I explain how Parfit's metaethical commitments imply that such a world is possible, and why this possibility is a problem for Parfit's project of reconciling Kantianism, contractualism, and consequentialism. I consider two of Parfit's responses to my counterexample.