Platonism is the philosophy of Plato, one of the most influential thinkers in Western history. Its central doctrine is the theory of Forms. Plato argued that the world we perceive with our senses is not the real world. It is a shadow of a higher reality. The real world consists of eternal, unchanging Forms: Beauty itself, Justice itself, the Good itself. Particular things in the world are beautiful or just insofar as they participate in these Forms. The Form of the Good is the highest, the source of all being and knowledge.

Plato presented his philosophy in dialogues, with Socrates as the main speaker. The Republic, the Symposium, the Phaedo, and the Timaeus are among the most famous. Platonism influenced early Christianity, especially through Augustine and Origen. It shaped Islamic philosophy through Al-Farabi and Avicenna. It shaped Jewish philosophy through Philo. In the Renaissance, it inspired the Florentine Academy. In modern philosophy, it influenced mathematics, where many thinkers hold that mathematical objects exist independently of the mind. Platonism is not just a historical doctrine. It is a live option in metaphysics, epistemology, and philosophy of mathematics.

Core doctrines

• Theory of Forms. Eternal, unchanging realities beyond the sensible world.
• Recollection. Learning is remembering what the soul already knows.
• The Good. The highest Form, source of being and knowledge.
• The divided line. A hierarchy of knowledge from imagination to understanding.

Platonism is not the same as Plato's own philosophy, though the two overlap. Platonism refers to the tradition that developed from his thought.