Eminent Greek philosopher who lived from c. 428 B.C.-347 B.C. He was a friend and admirer of Socrates, whom he features as a character in many of his dialogues and treatises. Among these, some of the most important include Apology, Crito, Gorgias, Ion, Republic, Phaedo, Phaedrus, Symposium, Timaeus, Critias, and Laws.