G. A. Cohen and J. Raz object that Constructivism is incoherent because it crucially deploys unconstructed elements in the structure of justification. This paper offers a response on behalf of constructivism, by reassessing the role of such unconstructed elements. First, it argues that a shared conception of rational agency works as a starting point for the justification, but it does not play a foundational role. Second, it accounts for the unconstructed norms that constrains the activity of construction as constitutive norms. (...) Finally, on this basis, it draws a contrast between constructivist and foundational methods of ethics, such as deontology and teleology. (shrink)