  At least two kinds of questions are relevant here. First, once we have a particular property in mind how can we know it is a moral one? Second, how do we come to know anything about moral properties apart from knowing they are moral? The first question might seem more difficult for the naturalist than for some non-naturalists; if goodness really is a sui generis non-natural property then perhaps being directly acquainted with it is sufficient for recognizing it as moral. The second question, though, is easier for the naturalist than the non-naturalist. Since the naturalist holds that moral properties are either identical to or reducible to some subset of natural properties there need be no mystery about how we come to have some knowledge of those properties even if there is some residual mystery as to how we discover that they are the moral ones. Or, at least, a commitment to naturalism in meta-ethics introduces no new problems about how we come to know anything about these properties. For given naturalism, the moral properties might well be identical to or reducible to familiar properties like the property of promoting happiness or the property of being truthful. In general we learn about such natural properties through observation and scientific inquiry and the naturalist can “piggy back” on whatever more general epistemological theory explains our ability to come to know anything about those properties. We learn, for example, what kinds of upbringing promote honesty through empirical observation and theorizing. Non-naturalism can be understood in many different ways, but none seems to make the task of explaining the possibility of moral knowledge as straightforward as it seems to be for the naturalist.