An ancient Greek philosopher, often considered the most important figure in Western philosophy. Plato was a student of Socrates and later became the teacher of Aristotle. He founded a school in Athens called the Academy. Most of his writings are dialogues. He is best known for his theory that ideal Forms or Ideas, such as Truth or the Good, exist in a realm beyond the material world. In fact, however, his chief subjects are ethics and politics. His best-known dialogues are the Republic, which concerns the just state, and the Symposium, which concerns the nature of love.