An immediate difficulty with this debunking argument is that it assumes that moral beliefs are not about moral properties that are also natural properties and hence are empirically knowable and can interact causally with other natural properties (compare Sturgeon’s reply to Harman in Sturgeon 1985; see also Campbell 1996, on Ruse). Consideration of moral naturalism, that is, opens up the possibility that those of our ancestors who tended to respond positively to moral properties had an advantage