Conventionalism about promising is the view that the power to make binding promises depends essentially on the existence of a social practice or convention of promising. This paper explores an objection to conventionalism that says that—(allegedly) contra conventionalism—there is no morally acceptable world in which we lack the power of promise. Instead, normative powers theorists claim that our power of promise is morally basic or necessary. I argue that the conventionalist need not deny this claim. There are several ways to (...) develop a noncontingent conventionalism: a version of the view that can accommodate the insight that the power of promise is indispensable to morally acceptable lives. Then, I argue that the conventionalist is indeed on the hook for accommodating this insight. I wrap up by considering the state of play in the debate over conventionalism about promising. Once we note the theoretical possibility of noncontingent conventionalism, it looks like the theatre of battle shifts to the difficult question of whether “natural” morality always provides “moral necessities.”. (shrink)