Abstract

The paper examines two forms of naturalistic moral realism, “Micro-structure realism” and “Reason realism” . The latter, as we defend it, locates the objectivity of moral facts in socially constructed reality, but the former, as exemplified by David Brink\'s model of naturalistic moral realism, secures the objectivity of moral facts in their micro- structure and a nomic supervenience relationship. We find MSR\'s parity argument for this account of moral facts implausible; it yields a relation ship between moral facts and their natural- scientific constitution that has a queer, slapped- together quality. We argue that the relationship needs to be spelled out by a process of social construction, involving collective intentionality and constitutive rules. We explain how our constructivist model of RR differs from a form of it defended by Michael Smith , which analyzes moral facts by reference not to construction but rather to a hypothetical situation of full rationality. We agree with Smith, as against Bernard Williams, that a rational agent may have reasons for acting that go beyond the agent\'s “subjective motivational set,” but we locate such reasons by reference to the agent\'s member ship in an actual community, and we explore the prospects for moral objectivity given this constraint on moral reasons