The aim of this paper is to defend moral relativism from the accusation that it would make it irrational to classify past changes in public opinion as instances of moral progress, for they would constitute an improvement only from our current point of view. The argument is this. For our assessment of a change in public opinion as an instance of moral progress to be rational, we need to take the moral claims made before the change to be false simpliciter (...) while being open to the possibility that we ourselves change our minds at some point. These two things can be made compatible if we construe moral relativism as taking the truth of moral claims to be relative to the context of assessment. Thus understood, moral relativism is in fact the only view that makes room for talk of moral progress, as the rest of candidate positions make it irrational. (shrink)