"Republic", Plato's best known and most frequently read dialogue, although receiving a flood of translations and philosophical analysis over the last 100 years, has in recent times been quite short of detailed commentaries. In particular, a full edition of the introductory sections of the dialogue, representing, probably, a single papyrus roll in the original text (the division into our 'Books' came later), has not been attempted for more than fifty years. In that period scholarship has moved on, and this edition aims to take into account recent developments in the study of Plato's literary style as well as of his ideas. The arguments have always been of great interest to philosophers, especially the sophist Thrasymachus' clash with Socrates in defending injustice as the most profitable life-choice (which of them wins the argument?). But there is a great deal more to this introduction than abstract ideas; Plato chooses to begin his great work by staging a dramatic debate, arising out of a social meeting between Socrates and friends in the Athenian port of the Piraeus during a religious festival. The case against justice as a state of affairs leading to eudaimonia ('happiness') is put with great force and humour, not to mention bad temper, and in the cut-and-thrust of argument and the clash of personalities, Plato brings vividly to life the cultural and social world of his times and the crucial issues at stake for his contemporaries. He also puts as effectively as possible the adversarial case which Socrates has to answer in the rest of Republic. This edition is aimed principally at readers without Greek; however, following the main purpose of the series, a spectrum of needs is catered for, ranging from those studying through the original text to those working with the translation.