Platonism

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Platonism is the philosophy that descends from Plato of Athens (c. 428–348 BCE) and the tradition of those who read, defended, and extended him. At its core lies a single claim about where reality is most fully found: not in the shifting things the senses report, but in the Forms — the changeless, intelligible patterns (Justice itself, Beauty itself, the Equal) of which visible things are imperfect copies. Above the Forms, in the dialogues that reach furthest, stands the Good, the source of being and of knowability alike, compared in the Republic to the sun.

From that picture follow the moves that mark the tradition. The soul is held to be kin to the Forms and, in some dialogues, immortal; learning is therefore not the taking-in of something new but anamnesis, recollection of what the soul already knew — the argument staged in the Meno and the Phaedo. Philosophy becomes a turning of the whole soul from appearances toward the real, and ethics rests on the conviction that to know the good truly is to do it. How literally Plato meant any of this, and how much shifts across dialogues written over a lifetime, is a question the tradition has never settled; the dialogues argue rather than pronounce.

The school had an institutional life. Plato taught in the grove of the Academy outside Athens, and the Old Academy under his successors Speusippus and Xenocrates pressed his thought toward number and system. Then came a sharp turn: under Arcesilaus and Carneades in the third and second centuries BCE, the Academy became skeptical, arguing that certainty is unavailable and that the Platonic method is above all the testing of claims. Only later, in what scholars call Middle Platonism — Plutarch, Numenius, the handbook ascribed to Alcinous, roughly the first century BCE through the second CE — did a confident, doctrinal reading return, now placing the Forms in the mind of a supreme God and drawing freely on Aristotle and the Stoics.

That revival fed directly into Neoplatonism, the systematic reading begun by Plotinus in the third century CE; the line between late Middle Platonism and early Neoplatonism is one historians draw, not one the ancients marked. Through those heirs, and through later translators and readers, Platonism became one of the durable structures of Western thought. Its vocabulary of an unseen order behind the visible, of the soul’s ascent and of a Good beyond being, runs through Christian theology, Islamic philosophy, the Renaissance recovery of the dialogues, and much later esotericism — often at several removes, and not always under Plato’s name.

→ In the library: The Dialogues of Plato (Jowett) · Plato — Phaedo (Jowett)

→ Related: Neoplatonism · The One · Nous · Gnosis · Thomas Taylor