Can the question "Why do what morality requires?" be answered in such a way that anyone regardless of their desires or interests has reason to be moral? One strategy for answering this question appeals to constitutive arguments. In general, constitutive arguments attempt to establish the normativity of rational requirements by pointing out that we are already committed to them insofar as we are believers or agents. This study is concerned with the general prospects for such arguments. It starts by explaining (...) the general constitutive argument strategy, followed by an examination of constitutive arguments that have been given regarding theoretical reason and the instrumental principle in practical reason, and concluding with a discussion of some challenges to constitutive arguments in moral philosophy and some possible responses to these challenges. (shrink)