The central idea behind this paper is the claim that Kant's moral idea of a realm of ends is modeled on the category of community examined in his theoretical works, and that understanding Kant's account of the category of community helps us understand certain features of the idea of a realm of ends, and in particular the fact that a member of a realm of ends must be an autonomous agent. For Kant the idea of a community is essentially the idea of a multitude of individuals in interaction and in this paper I will attempt to show why Kant believes that only autonomous individuals can interact.

Central to Kant's mature ethics is his belief that it is impossible to refute the solipsist theoretically, for from the theoretical perspective (the perspective of the Critique of Pure Reason), we can have no knowledge of the existence of other individuals. According to Kant, if I believe that other human bodies are merely lumps of unconscious flesh to be used and abused for my own pleasure, I am not making a theoretical mistake but rather a moral choice.