  It is worth noting that the last three objections to moral naturalism are advanced by those who believe moral knowledge is possible but reject the idea that it is knowledge of the natural world. Of course, should those objections be successful, the upshot could be a victory for the moral skeptic, since the objections to thinking of moral knowledge as theological or as knowledge of a non-natural world may be just as successful. The problems for the possibility of moral knowledge, in short, must be seen holistically in view of the interlocking implications of the objections and replies. The following discussion of the implications of biological explanations of morals is no exception.