Ought but Cannot

I assess a series of arguments intended to show that ‘ought’ implies ‘can’. Two are rooted in uses of ‘ought’ in contexts of deliberation and command. A third draws on the distinctive resources of deontic logic. I show that, in each case, the arguments leave scope for forms of infinite moral consciousness—forms of moral consciousness in which a moral obligation retains its authority even in the face of the conviction that the obligation is impossible to fulfil. In this respect the paper sides with Martin Luther against Erasmus and Kant.