The issue of moral relativism is the question of how similar morality is to science-or, more precisely, to the common image of science as using reason and evidence to establish objective truths. So one would think that the best discussions of moral relativism would be based on the best philosophy of science of the time. In fact, the most advanced discussions of the issue are still limited by obsolete views of meaning and justification, inherited from positivist philosophy of science. After defending this diagnosis, I will base a solution to the problem of moral relativism on a more completely post-positivist account of meaning and justification. From this perspective, the problem of relativism will turn out to be a question about learning: do our moral beliefs emerge from a process of reliable learning, and are there contrary processes of moral learning that we cannot refute in any fair way? On the most plausible reading of the current evidence, anthropological, historical and psychological, the answer is at least half-relativist. The truth in moral absolutism is that our moral talk refers to something real and often describes it correctly. Our basic moral beliefs are sustained by processes of detection as the post-positivist account of reference requires. But the truth in relativism is that some moral outlooks radically different from our own are associated with rival conceptions of moral learning, whose claim to reliability cannot be refuted. While our confidence in our ways of learning is reasonable, it would be incorrect to assess the other ways as unreasonable or ill-informed. In the natural sciences, when people investigate the world using rival techniques, instruments or hypotheses, there is almost always reason to hope that more evidence would be the basis for a fair argument resolving the disputes between them. In morality, conflicting ways of learning often turn out to represent different kinds of emotional maturity, neither of them subject to fair refutation in light of the totality of data. This, and this alone, is the relativist difference between morality and science.