Theories of reasons and other normativia can seem to lead ineluctably to a tragic dilemma. They can be personal but parochial if they locate reasons in features of the point of view of actual people. Or they can be objective but alien if they take reasons to be mind-independent fixtures of the universe. Kantian constructivism tries to offer the best of both worlds: an account of normative authority anchored in the evaluative perspectives of actual agents but refined by a procedure that guarantees certain principles, like the moral law, will have universal and unconditional authority. This chapter considers motivations for such a view and chronicles the intrepid efforts of its adherents to make good on this guarantee - to show that the structure of practical reason commits reasoners to morality.