Sôphrosunê (“self-discipline”) is the often-forgotten sibling of justice, wisdom, courage, and piety in discussions of canonical Greek virtues. Christopher Moore shows that during the classical period it was the object of significant debate--about its scope, its feel, its practical manifestations, and its value.By interpreting sôphrosunê as a commitment to norm-following, we see that these pointed discussions of the virtue, previously ignored as parodic moralizing or expressions of political propaganda, are in fact concerned with the ideal of human agency. These discussions query the way we become fully responsible for our actions.Greek thinking about sôphrosunê becomes thinking about self-constitution, our crucial capacity to act on the general reasons that we come to identify with as our own.This perspective explains sôphrosunê''s inclusion in Plato''s canon of virtues, and before that its frequent appearance in funerary inscriptions, elegiac poetry, tragic drama, and historiography.