In this article, I vindicate the longstanding intuition that the Stoics are transitional figures in the history of ethics. I argue that the Stoics are committed to thinking that the ideal of human happiness as a life of virtue is impossible for some people, whom I dub ‘hopeless fools.’ In conjunction with the Stoic view that everyone is subject to the same rational requirements to perform ‘appropriate actions’ or ‘duties’ (kathēkonta/officia), and the plausible eudaimonist assumption that happiness is a source (...) of normative reasons only if it is in principle attainable, the existence of hopeless fools demonstrates that the Stoics were pluralists about the ultimate justificatory basis of rational action. Hopeless fools are required to behave just like their non-hopeless counterparts, not because doing so is conducive to their happiness, but because doing so conforms with the dictates of Right Reason. (shrink)