In this magnum opus, Socrates and his interlocutors undertake the construction of a theoretical city in speech to determine the definition of justice. The dialogue spans ten books, covering the triadic structure of the soul, the danger of imitative poetry, and the famous allegory of the cave. It argues that the just man is happier than the unjust, proposing a society ruled by philosopher-kings who have seen the light of the Good. This text remains the foundational document for all subsequent discussions on utopia, education, and governance.