Kant emphasizes that moral philosophy must be divided into two parts, a ‘purely rational’ metaphysics of morals, and an empirical application to individuals, which Kant calls ‘moral anthropology’. But Kant gives humanity (die Menschheit) a prominent role even in the purely rational part of ethics – for example, one formulation of the categorical imperative is a demand to treat humanity as an end in itself. This paper argues that the only concepts of humanity suited to play such a role are the rational idea of humanity, and the rational ideal derived from this idea, which Kant discusses in Critique of Practical Reason and other texts.
