Most theories of moral knowledge, throughout history, have focused on behavior-guiding rules. Those theories attempt to identify which rules are the morally valid ones, and to identify the source or ground of that privileged set. The variations on this theme are many and familiar. But there is a problem here. In fact, there are several. First, many of the higher animals display a complex social order, one crucial to their biological success, and the members of such species typically display a sophisticated knowledge of what is and what is not acceptable social behavior—but those creatures have no language at all. They are unable even to express a single rule, let alone evaluate it for moral validity. Second, when we examine most other kinds...