Republic (Gk. Politeia), dialogue in ten books by Plato. The traditional English title is derived from the Latin translation, Respublica, of the Greek title, and is perhaps misleading. The original meaning is closer to ‘society’ or ‘the state’. The Republic was written in the early years of the Academy, the school which Plato founded to give a philosophical education to those embarking on a political career. It is an exposition of the principles on which an ideal society, in Plato's view, should be based. The rulers (‘guardians’) are to be philosopher-kings who alone have knowledge of the ideas of Justice and the Good (see PLATO 4 and 5); they will rule in the interests of the majority, who have only limited perception. Book I has the conversational form of an early Socratic dialogue (see PLATO 2), but the rest of the work is a more or less continuous exposition by Socrates of what one must suppose to be Plato's own views on society at the time of writing (about 375 BC). The interlocutors are Socrates, an old man Cephalus (father of the orator Lysias) and his son Polemarchus, Thrasymachus a sophist, and Plato's brothers Glaucon and Adeimantus. The discussion takes place at the house of Cephalus.

The dialogue starts with the question ‘What is justice?’, which at its simplest means ‘Why should we be good?’ The conventional definition offered by the poet Simonidēs, that it means giving a person his due, is shown to be inadequate. Thrasymachus rejects conventional morality and maintains that human behaviour is, and should be, guided by self-interest. Socrates reduces Thrasymachus to silence, but Glaucon and Adeimantus remain unsatisfied and restate his case for him. Glaucon argues that justice is a matter of expediency, and that we would all be unjust to our own advantage if we could. Adeimantus argues that justice is pursued only for mercenary reasons. Socrates must show that justice is preferable to injustice for its own sake and not for the rewards it brings. Socrates suggests that justice will best be seen in the macrocosm of a perfect city-state, and if discovered there, can be found by analogy in individuals. Accordingly Socrates proceeds to construct the ideal state. This is seen to consist of three classes, guardians or magistrates (in whose education Plato is particularly interested), auxiliaries or soldiers, and producers. In the first resides the wisdom of the state, in the second its courage. Temperance or restraint must be present in all three classes, while political justice is that which keeps each class to its proper functions. Similarly, individuals have the qualities of the three classes present in their souls, but in varying proportions. They are wise in respect of the rational element in them, courageous and moved by generous impulses in respect of the spiritual element, and they are moved to satisfy their appetites. In a disciplined individual, spirit and appetite are subordinated to reason; justice consists in the harmony of all these elements. The discussion of the ideal state is continued; Socrates' proposal for the community of women and children is explained, and it is shown that for the efficient working of the constitution the supreme power must be in the hands of philosophers. Socrates expounds the proper education of the guardians (from which the misleading tales of the poets must be excluded) and the nature of true knowledge, which is not of the objects and images of the world of the senses, but of the realities of the intellectual world, apprehended by pure intelligence. The theory of Ideas or Forms (see PLATO 4 and 5) is developed; and the liberating nature of right education is illustrated by the simile of men chained in a subterranean cave representing, in Plato's view, the general human condition, who see only the shadows of objects behind them thrown by firelight on the wall in front of them, so that they take these shadows for the only realities: the guardians will struggle out of the cave into the world of knowledge and wisdom. Socrates resumes (book 8) the subject of the various types of political organization and personal character, and traces the process of degeneration from the perfect type and the perfect man, namely aristocracy and the aristocratic man, through four stages to the worst, namely tyranny and the tyrannical man. Finally the rewards of virtue are considered, chief among these being the reward that the soul receives in the life after death, the soul being immortal, but rewards are merely a secondary consideration. The nature of this afterlife is indicated in the tale of Er the son of Armenius, who twelve days after his death returned to life and described what he had seen in the other world.