Abstract
Philosophy can serve two roles in relation to moral thinking: first, to provide a meta-ethical commentary on the nature of moral thought, as the methodology or the philosophy of science provides a commentary on the nature of scientific thought; and second, to build on the common presumptions deployed in people's moral thinking about moral issues, looking for a substantive moral theory that they might support. The present essay addresses the nature of this second role; illustrates it with substantive theories that equate moral obligations respectively with requirements of nature, self-interest, benevolence, reason and justifiability; and outlines a novel competitor in which the focus is shifted to requirements of co-reasoning and respect