Are professional roles bound by the norms of ordinary morality? This article begins with a discussion of two existing models that give contrary answers to this question; the practice model detaches professional ethics from ordinary morality, while the translation model denies any real divergence. It is argued that neither model can give a satisfying account of how professional roles ground distinct claims that are morally authoritative. The promise model is articulated and defended, wherein the obligations of professional roles are grounded (...) in an act of self-binding by the profession; the public is the promisee, and thereby entitled to make role-dependent claims. This model retains a connection to ordinary morality, but does not reduce role authority to individual conscience. Legitimate promises bind the role holder even in the face of moral disagreement. (shrink)