The Republic is an extended attempt to discover the nature of the good life and to defend the claim that such a life is the best one to live. Plato speaks of “justice” where I speak of the good life, but he builds no assumptions about its nature into the target of his enquiry. Everything is open to question and the only constraint is that the enquiry should be guided by reason.

THE DISPUTE WITH THRASYMACHUS

The work starts with an exchange between Socrates and others who offer various accounts of the nature of justice; and as is normal in such exchanges in other works of Plato, Socrates is able to show that they are confused – without himself producing any more satisfactory account. The Republic is traditionally divided into ten books. These divisions are not Plato's, but to keep it simple I retain the convention, and so we begin with Book 1. Some have regarded this first part, Book 1, as a distinct detachable composition from the remainder of the work; I think this is wrong. The correct view is that it stands in dialectical counterpoise to everything that follows. The work on the whole examines two views on the relations between power, knowledge and the good life. In Book 1 the case is made for the thesis that value and the knowledge of it are based on power.