Abstract

Although Thrasymachus' eloquent condemnation of justice in Book One of the Republic has fascinated many, no precise philosophical interpretation of Thrasymachus' thought has found general acceptance. Some have read Thrasymachus' ideas as an advocacy of ethical egoism, others as a defense of legalism, and a third group detects in his words a foreshadowing of Machiavelli or Nietzsche. In chapter one I show that these questions about Thrasymachus' doctrines not only have a crucial bearing on how to interpret Book I of the Republic but also determine how we assess the significance and character of Plato's moral argument in the Republic as a whole. ;In the second chapter I argue that Thrasymachus rather than Glaucon and Adeimantus links the ethical discussion in the later Books of the Republic to a wider audience. It thus follows that a correct interpretation of Thrasymachus' doctrines allows us to see how Plato's moral argument is intended to address popular moral concerns. Moreover, since both Glaucon and Adeimantus profess to renew Thrasymachus' challenge in Book II, a successful interpretation of their doctrines presupposes that we understand clearly how Plato's brothers restate Thrasymachus' ethical challenge. I show in chapter three that all previous attempts to clarify the relation between the challenges of Book I and II of the Republic fail to explain this relationship in a satisfying way. ;Based on these results, I develop a new interpretation of Thrasymachus' doctrines. I start my analysis in chapter four by showing that all previous interpretations of Thrasymachus' doctrines lead to serious difficulties. This result enables me in chapter five to approach Thrasymachus' ideas from a new perspective. My new interpretation places Thrasymachus' praise of injustice at the center of his ideas. I show that Thrasymachus embraces the central claim that injustice consists in exercising political power over others. Consequently, Thrasymachus emerges as a sharp political and ethical thinker who holds that unconstrained rule over others is a necessary condition for freedom and happiness. This new interpretation of Thrasymachus' doctrines provides a fruitful guide for interpreting Plato's moral argument in Books II-X. For I show in my last chapter that Plato's moral arguments in Book VIII and IX of the Republic are a direct response to Thrasymachus and not to Glaucon's and Adeimantus' challenge in Book II. It follows that Plato's overall moral argument in the Republic falls into two parts. The arguments in Book II-IV are addressed to Glaucon and Adeimantus, whereas the latter arguments in Books VIII and IX are addressed to Thrasymachus' challenge of Book I