Plato's biography is drawn mainly from the work of other ancient writers and a few of what are presumed to be Plato's letters. He was born in Athens around 428 BC to an aristocratic family with a long and esteemed history of political leadership. According to an anecdote told by the Greek biographer Diogenes Laertius, Plato was originally named Aristocles. His wrestling coach, however, dubbed him "Platon" (meaning "broad") on account of his broad shoulders—shoulders that would one day bear the foundational weight of much of Western thought.
Plato's father Ariston descended from the early kings of Athens. His mother Perictione came from a similarly distinguished line that included the sixth-century legislator Solon. Plato had two brothers, Adeimantus and Glaucon, as well as a younger sister, Potone. Plato's father appears to have died when Plato was still a young child. With no other way to support Plato and his siblings, his mother remarried to Pyrilampes, an associate of the statesman Pericles. Perictione later had a child with Pyrilampes named Antiphon.
Plato had political ambitions as a young man and appeared destined to follow the family tradition. He became disillusioned with Athenian politics, however, because both the Empire and its politics had begun to decline since the onset of the Peloponnesian War (several years before Plato's birth). Outside the political sphere, Plato enjoyed success in athletics and engaged in both poetry and drama. According to Aristotle, Plato also became familiar with the teachings of Cratylus—a student of Heraclitus—as well as those of other pre-Socratic thinkers such as Pythagoras and Parmenides. These teachings provided the young philosopher with an introduction to the foundations of Greek metaphysics and epistemology.
Around 409 BC, Plato met Socrates and became his devoted follower. Socrates was already a famous—or infamous—figure in the city of Athens on account of his intellectual unorthodoxy. Socrates has been credited with teaching Plato foundational philosophy along with his dialectical method of inquiry, which approaches the truth through a series of questions and tentative answers that must be carefully and continually examined and re-examined. It is thought that Socrates directed his disciples' inquiries toward the question of virtue and how it manifests itself in the nobility of human character. If there is a broader context under which Plato's philosophy developed—a unified context including metaphysics, epistemology, aesthetics, politics, and ethics—it is the pursuit of virtue or human goodness.
Following the end of the Peloponnesian war, an oligarchical tyranny called the "Thirty Tyrants" ruled Athens for eight months from 404-403 BC. Plato’s uncles Critias and Charmides were among the Thirty Tyrants and invited their nephew to join them. The junta was dissolved through civil war, though, before Plato could decide.
In 399 BC, Plato witnessed the trial and execution of Socrates at the hands of the restored Athenian democracy. Socrates was charged with corrupting the youth and religious apostasy, hated by many for critiquing the new democratic government and for making its leading citizens look foolish. The trial was later memorialized in Plato's Apology; Socrates’ reasons for not taking up a chance to escape from prison rather than face punishment are recorded in Plato's Crito.
During the next twelve years, Plato traveled widely around the Mediterranean, allegedly visiting Italy, Sicily, and Egypt. In these foreign lands, he sought out philosophers, priests, and prophets, with whom he reportedly studied religion, geometry, and astronomy. Around this time, he also composed his first group of dialogues, generally referred to as the "Socratic dialogues.” These include the Crito, Charmides, Euthyphro, Laches, Lysis, Hippias Minor, Hippias Major, Ion, and sometimes Gorgias, Meno, and Protagoras.
In 387 BC, at the age of forty, Plato returned to Athens and founded the Academy. Often described as the first European university, the Academy taught a comprehensive curriculum of astronomy, biology, mathematics, political theory, and philosophy, until it was closed in 529 AD by the Emperor Justinian. Aside from administering the Academy, Plato expounded his more mature philosophic speculations during this period in works such as the Phaedrus, Symposium, Euthydemus, Cratylus, Phaedo, and The Republic.
Although the Academy became his home base, Plato made two more trips to Sicily. The first was after Dionysis II’s ascent to the throne. His brother-in-law Dion persuaded him to invite Plato to help him become a philosopher-ruler, like the one described in The Republic. Within months, Dionysis II had Dion sent into exile and Plato under house arrest. Plato eventually got permission to return to Athens, where he and Dion were reunited at the Academy. A few years later, though only upon Dion and Dionysis’ insistence, he returned to Syracuse once more, and was again imprisoned by Dionysis. Plato escaped thanks to help from his Tarentine friends.
Relatively little is known about the final years of Plato’s life. He continued to lecture at the Academy, where Aristotle studied until Plato’s death. The late Platonic dialogues include the Sophist, Statesman, Critias, Philebus, Laws, and Timaeus. The year of Plato’s death is believed to be around 348 or 347 BC.