Critiqued both the "rationalists" and "empiricists" which were popular camps back then. Immense impact on modern philosophy, possibly the largest ever.

Known for Markov processes.

Knew Socrates, and carried the torch after his execution by retelling what he had said, and developed philosophy tremendously. Founded a school in Athens named the Academy, after a general named Academus. Taught Aristotle, his most famous student, who disagreed with him on a number of points. Platonic philosophy was favored by the Catholic Church until the Renaissance, when Aristotelian philosophy was re-translated from Arabic and came into vogue.