What are the possible functions of moral cognition? Addressing this question has proved difficult, leading to disagreement among moral psychologist. Researchers claiming that morality is composed of many distinct domains have posited multiple functions, whereas researchers focusing on the features that are unique to and common across all moral judgments have suggested a unified evolutionary function. In this review, we suggest that the limitations of these accounts can be overcome by systematically investigating the cognitive mechanisms that support moral judgments across descriptively distinct domains. As a case study, we focus on the contrast between harm and purity morals, and we argue for a novel functional difference on the basis of differences in the underlying psychological processes. Understanding the psychology behind distinct morals will pave the way for understanding the distinct functions of moral cognition.