  In the face of this challenge it may be tempting for a believer in the possibility of moral knowledge simply to reject the project of naturalizing moral epistemology. An immediate difficulty in taking this way out is the close connection between this project and moral naturalism, together with the role that the latter theory plays in addressing the ontological problems raised in section 3. Earlier we noted how the naturalizing project in moral epistemology can lead a believer in moral knowledge toward moral naturalism. The reverse is also true for a person who accepts a naturalized epistemology for non-moral knowledge. If such a person thinks that moral features of the world can be found among its natural properties and that these properties can be investigated empirically, she will have a hard time explaining why science is incapable of explaining what these moral properties are and how we can know them. In sum, we may need moral naturalism to address the ontological problems for moral knowledge, but then we are led to a naturalized moral epistemology and to the challenge now before us.