How 'Must' and 'May' Built Morality

In this fourth lecture in her series on rethinking metaphysics, Amie L. Thomasson turns to moral discourse. She asks what moral language is really doing and why it takes the forms it does. Rather than assuming moral statements simply describe moral facts, she traces the functional evolution of normative language: from basic imperatives that regulate behavior, to modal verbs like "must" and "may" that enable reasoning and distinguish what is required from what is permitted, to nominalizations that allow us to theorize about morality in abstract terms. This progression, she argues, marks a crucial shift from the rule of individual persons to the rule of law. Thomasson then shows how this functional approach can preserve the insights behind competing metaethical positions, including prescriptivism, expressivism, and descriptivism, by revealing that each captures a genuine aspect of moral language. The result is a deflation of classic metaethical puzzles, not by ignoring them, but by dissolving the confused presuppositions that generated them in the first place.