Plato (c. 428–348 BC) was an Athenian philosopher, a student of Socrates, the teacher of Aristotle, and the founder of the Academy — arguably the first institution in the West recognisable as a university. He is the earliest Western philosopher whose complete works survive.
His influence is difficult to overstate. Alfred North Whitehead’s remark that the European philosophical tradition “consists of a series of footnotes to Plato” is an exaggeration that most philosophers let stand, because the questions he framed — what is real, what can be known, what is justice — have not been replaced so much as inherited.
This guide covers his life, his works, and the ideas he is known for, with links to fuller treatments of each.
Plato’s Life
Plato was born in Athens around 428 or 427 BC into a wealthy and politically connected aristocratic family. His mother Perictione was related to the lawgiver Solon; her brother Charmides and cousin Critias both later joined the Thirty Tyrants. A young man of his background was expected to enter politics.
Two things prevented it. The first was the Peloponnesian War and the political chaos that followed. The second was Socrates. Plato became his follower, and when Athens executed Socrates in 399 BC, he concluded that the city was not a place where a decent person could pursue public life. He turned to philosophy instead.
He then travelled — to Megara, and by later accounts to Egypt, Cyrene and southern Italy, where he encountered Pythagorean mathematics that left a lasting mark on his thinking. His trips to Syracuse in Sicily were the great practical failure of his life: three attempts to influence the tyrants Dionysius I and II, none of which worked, and one of which reportedly ended with Plato being sold into slavery before being ransomed by a friend.
He died in Athens around 348 or 347 BC, aged about eighty. On the origin of his name — and the tradition that he was really called Aristocles — see why Plato was given his name.
The Academy
Around 387 BC Plato founded a school in a grove outside Athens sacred to the hero Academus. The Academy taught mathematics, astronomy and dialectic alongside philosophy, and in some form it persisted for centuries. Aristotle arrived at seventeen and stayed for twenty years.
More on its structure and legacy: Plato’s Academy — structure, curriculum and legacy.
What Plato Wrote
Around thirty-five dialogues and a set of letters are attributed to him, and unusually for an ancient author, essentially all of it survives. He wrote almost entirely in dialogue form, with Socrates usually as the main speaker — which is why separating Plato’s views from his teacher’s is a permanent scholarly headache.
Scholars conventionally group the dialogues into three periods:
- Early (Socratic): short, inconclusive, focused on defining a single virtue — the Apology, Crito, Laches and the Euthyphro among them.
- Middle: the great constructive works, including the Republic, Phaedo, Symposium, Meno and Phaedrus.
- Late: more technical and often self-critical — Theaetetus, Sophist, Statesman, Timaeus and the Laws.
What Was Plato Known For? His Key Ideas
The Theory of Forms. Plato’s central and most contested doctrine holds that the changing things we perceive are imperfect copies of unchanging, non-physical Forms. A particular just act participates in Justice itself. See how to understand the Theory of Forms.
The Allegory of the Cave. In the Republic, prisoners chained facing a wall mistake shadows for reality; one escapes, sees the sun, and returns to a hostile reception. It is Plato’s image for education and for the philosopher’s position in society. See how to interpret the Allegory of the Cave.
The tripartite soul. Plato divides the soul into reason, spirit and appetite, and defines justice in the individual as the right ordering of the three. See the appetitive soul.
The philosopher king. Cities will not cease from evil, Plato argues, until philosophers rule or rulers philosophise — a claim inseparable from his scepticism about democracy. See what a philosopher king is according to Plato.
Recollection and the immortal soul. In the Meno and Phaedo, learning turns out to be remembering what the soul knew before birth — an argument that carried Platonic ideas deep into later Christian thought.
Plato and Aristotle
Plato’s most consequential student disagreed with him. Aristotle rejected the separate existence of the Forms, arguing that form and matter are found together in particular things. The split between the two — the world explained from above versus from the ground up — became one of the organising divisions of Western thought. See why Aristotle was a disciple of Plato.
Where to Start
For a first encounter, the Apology is short, dramatic and needs no background. The Symposium is the most enjoyable. The Republic is the major work but a serious undertaking. The Stanford Encyclopedia of Philosophy entry on Plato is the best free scholarly overview.
Conclusion
Plato was an Athenian aristocrat who turned away from politics after his teacher was executed, founded a school that outlasted him by centuries, and wrote a body of dialogues that set the agenda for Western philosophy. He is known above all for the Theory of Forms, the Allegory of the Cave, the tripartite soul and the philosopher king — and for teaching the one student capable of dismantling him.