In cases where two human cultures disagree over fundamental ethical values, metaethical questions about what could make one or the other position correct arise with great force. Philosophers committed to naturalistically plausible accounts of ethics have offered little hope of adjudicating such conflicts, leading some to embrace moral relativism. In my dissertation, I develop an empirically grounded response to moral relativism by turning away from debates over which action types are right and wrong and focusing instead on shared features of human emotional motivation. On my account, being motivated by ill-will is ethically bad (if it is), just because human beings who are fully and accurately aware of how unpleasant it is to be motivated i...