In Kant’s philosophy nonrational beings are denied moral standing. I argue that Kant’s rational humanism is arbitrary and morally impoverished. In particular I show that Kant moves illegitimately from the first formulation of the categorical imperative (which makes no mention of a moral domain) to the second (which limits moral recognition to rational beings). The move to the second formulation relies on a new and unsupported principle introduced by Kant: rational nature and only rational nature exists as an end in itself.