Moral knowledge

Common parlance seems to presuppose that there is genuine moral knowledge. We hear people say that someone knew full well that he was doing wrong and did it anyway, or that someone knew a friend had been immoral but would not acknowledge this, or that some people pretend not to know their moral responsibilities. Indeed, mere sanity is supposed to imply ability to “know the difference between right and wrong.” But there are skeptics about moral knowledge, as about other kinds of knowledge; and the former include people not skeptical about other domains, such as natural science (see SinnottArmstrong 2006 for a full-scale treatment of the nature and varieties of moral skepticism). Two kinds of skepticism should be distinguished. One denies that there is moral knowledge but not that there is justification for moral claims. The other denies that there is either moral justification or moral knowledge. We must consider both possibilities, but the prior question is whether there are even moral propositions to be known.