Conceptions of individual autonomy and of rational autonomy have played large parts in twentieth century moral philosophy, yet it is hard to see how either could be basic to morality. Kant's conception of autonomy is radically different. He predicated autonomy neither of individual selves nor of processes of choosing, but of principles of action. Principles of action are kantianly autonomous only if they are law-like in form and could be universal in scope; they are heteronomous if, although law-like in form, they cannot have universal scope. Puzzles about claims linking morality, reason and autonomy are greatly reduced by recognising the distinctiveness of Kantian autonomy.