The Caveman's Conscience: Evolution and Moral Realism

An increasingly popular moral argument has it that the story of human evolution shows that we can explain the human disposition to make moral judgments without relying on a realm of moral facts. Such facts can thus be dispensed with. But this argument is a threat to moral realism only if there is no realist position that can explain, in the context of human evolution, the relationship between our particular moral sense and a realm of moral facts. I sketch a plausible evolutionary story that illuminates this relationship. First, the sorts of adaptive pressures facing early humans would have produced more than just potent prosocial emotions, as evolutionary antirealists like to claim; it would have produced judgments—often situated within emotions—to the effect that others could reasonably disapprove of some bit of conduct, for an early human who cared deeply about how others might respond to her action enjoyed the benefits of more cooperative exchanges than those early humans who did not. Second, according to objectivist versions of moral constructivism, moral facts just are facts about how others, ideally situated, would respond to one's conduct. Thus if any objectivist moral constructivism story is true, then we can intelligibly assert that a) our capacity for moral judgment is the product of adaptive pressures acting on early humans and b) some moral judgments are objectively true.