In this paper I explore the degree to which the most plausible versions of a Kantian approach to punishment differ from plausible versions of a consequentialist approach with regard to the permissibility of deterrence. I begin by examining the Formula of Humanity. Perhaps surprisingly, I show that the most plausible statement of this principle does not even mention the idea of treating people merely as a means. The other crucial claim in that principle—that we must treat people as ends—is in (...) fact the operative idea. The best interpretation of the Formula of Humanity makes Kantianism a basically ‘objective’ moral theory, in a sense to be explained, as is consequentialism. After defending my interpretation of the formula I go on to consider a recent theory of punishment developed by Victor Tadros that appeals to a principle paralleling the Formula of Humanity, the Means Principle. I argue that the Means Principle is not a plausible moral principle by using arguments that derive from my interpretation of the Formula of Humanity. The Means Principle is therefore unsuited to be the way to frame a discussion of whether deterrent punishments are permissible. In Section IV I discuss a version Kantian moral theory that can be seen as based on a proper interpretation of the Formula of Humanity. This version, drawing on the work of John Rawls, permits the pursuit of deterrence. This suggests that Kantianism and consequentialism are not divided on the issue of the permissibility of deterrence. In the final section I note one reason for thinking that further features of the consequentialist approach to deterrence make it superior to the Kantian-Rawlsian. (shrink)