Abstract

The “impure” part of Kant’s ethics consists of material concerning empirical knowledge of human beings. Kant is well-known for his insistence that the supreme moral principle must be discovered through non-empirical consideration of such notions as morality and rational wills. What is less appreciated is that Kant recognized what his critics have always said: that a pure ethics for rational beings in general cannot provide adequate, practical guidance for human beings in particular, real-world situations. Nor can a pure ethics answer the myriad of questions about which social relations, institutions, and practices foster morality in beings like us. Indeed, even in the Grounding for the Metaphysics of Morals, where Kant’s focus is explicitly on pure ethics, he acknowledges the importance of empirical ethical work. And in the Metaphysics of Morals, which sets forth various classes of moral duties for human beings in general, Kant draws on species-specific, empirical knowledge of human beings as well as on the purely derived requirement to respect rational nature. For example, Kant’s argument for duties regarding animals depends on empirical claims about how our treatment of animals affects our emotions, and how certain emotions facilitate moral behavior. Kant’s method here makes clear that which duties the supreme moral principle gives us depends in large part on human nature as well as on rational nature.