Smith has defended the rationalist's conceptual claim that moral requirements are categorical requirements of reason, arguing that no status short of this would make sense of our taking these requirements as seriously as we do. Against this I argue that Smith has failed to show either that our moral commitments would be undermined by possessing only an internal, contextual justification or that they need presuppose any expectation that rational agents must converge on their acceptance. His claim that this rationalistic understanding (...) of metaethics is required for the intelligibility of moral disagreement is also found to be inadequately supported. It is further proposed that the rationalist's substantive claims – that therearesuch categorical requirements of reason and that our actual moral commitments are a case in point – are liable to disappointment; and that the conceptual claim is fatally undermined by reflection on how we might best respond to such disappointment. (shrink)