The Republic

Plato's best-known dialogue, written around 375 BC, in which Socrates and his friends ask one question: what is justice, and is the just person happier than the unjust? Glaucon challenges him with the story of the ring of Gyges, which makes its wearer invisible: would anyone stay just if they could never be caught? To answer, Socrates imagines an entire just city, with three classes that mirror the three parts of the soul, the education of its guardians, equal roles for women among them and rule by philosopher-kings, and he tells the famous Allegory of the Cave, where prisoners mistake shadows on a wall for reality.

Few books have shaped philosophy more. In the Islamic world al-Farabi's Virtuous City drew on it and Averroes wrote a commentary on it; its questions about justice, education and power are still ours. This translation is the classic version by Benjamin Jowett. Plato's last thoughts on the ideal state are in the Laws.

Plato (c. 428–348 BC) was born into an aristocratic family in Athens and became the devoted student of Socrates. After his teacher's trial and execution in 399 BC, he travelled, returned to Athens and founded the Academy, a school that lasted for centuries and counted Aristotle among its students.

Almost all his writings are dialogues in which Socrates questions his fellow citizens about justice, love, knowledge and the soul, from the Apology to the Symposium and the Republic. Known to Arab philosophers as Aflatun, he was read closely by al-Farabi and Ibn Rushd, and Western philosophy has been called a series of footnotes to him.