  A skeptic might object that it’s impossible to have justified background beliefs about the functional profile of moral properties. But this kind of objection threatens to prove too much. We are entitled to rely on background beliefs in moral theory development because we’re entitled to do so in science, generally (Boyd 1988, 189–191). Our theories and background beliefs are justified together by their overall coherence. So if there are no substantial metaphysical or epistemological issues raised by the claims that healthiness exists and that we can know about healthiness, then there should be no substantial metaphysical or epistemological issues raised by the claims that goodness exists and that we can know about goodness.