In the Theaetetus Socrates provides an elaboration and discussion of Protagoras’ measure doctrine, grounding it in a “secret doctrine” of flux. This paper argues that the anthropology of the myth in the Protagoras provides an earlier, very different way to explain the measure doctrine, focusing on its application to civic values, such as “just,” “fine,” and “pious.” The paper shows that Protagoras’ explanation of the dual etiology of virtue – that it is acquired both by nature and by nurture – (...) tracks the two meanings of “anthropos” in his formulation of the measure doctrine, as “humankind” and “individual human.” On Protagoras’ account, humankind’s survival can be explained by the fact that humans share shame and justice, which enables them to live together in cities. (shrink)