 On this reading, Thrasymachus’ three theses are coherent, and unrestricted in their scope; but they are not definitions. They are exercises in social critique rather than philosophical analysis; and yet Thrasymachus’ debunking is not, and could not be, grounded purely on philosophically neutral ‘sociological’ observation. Thrasymachus is—on almost any reading – relying on a further pair of assumptions, which we can also find on display in the speeches of Callicles and of Glaucon in Book II, as well as other contemporary texts. One is that wealth and power, and the pleasures they provide, are  the goods in relation to which our ‘advantage’ must be assessed. (‘Good’ [agathon] and ‘advantage’ [sumpheron] are equivalent terms in this context, and ‘happiness’ [eudaimonia] is what they produce.) The other is that these goods are zero-sum: for one member of a community to have more of them is for another to have less. That is why just behavior on my part, which involves forgoing opportunities for my own advantage out of respect for the law, inevitably serves the advantage of other people—in particular, those who are willing to ‘take advantage’ of me (as we still say), and above all the self-interested rulers who made the laws. These twin assumptions about the nature of the good also shape Thrasymachus’ conception of rationality. The rational or intelligent man for him is one who, seeing through the mystifications of moral language, acts clear-sightedly to serve himself rather than others. When Socrates asks whether, then, he holds that justice is a vice, Thrasymachus instead defines it as a kind of intellectual failure: “No, just very high-minded simplicity,” he says, while injustice is “good judgment” and is to be “included with virtue and wisdom” (348c–e). 