Abstract
This paper introduces constitutivism about practical reason, which is the view that we can justify certain normative claims by showing that agents become committed to these claims simply in virtue of acting. According to this view, action has a certain structural feature – a constitutive aim, principle, or standard – that both constitutes events as actions and generates a standard of assessment for action. We can use this standard of assessment to derive normative claims. In short, the authority of certain normative claims arises from the bare fact that we are agents. This essay explains the constitutivst strategy, surveys the extant attempts to generate constitutivist theories, and considers the problems and prospects for the theory.