Plato

Plato was an ancient Greek writer and philosopher and was the student of another known philosopher, Socrates.

Biography
William Blake recalled that Plato had argued that the nature of reality was unknown and that one's perceptions were like shadows cast on the wall of a cave. (PROSE: The Pit)

The Fourth Doctor and Leela met Plato at a gathering at Anaximander's home. (PROSE: The Brain of Socrates)

Bernice Summerfield met Plato and his teacher Socrates whilst time-travelling. (AUDIO: The Oracle of Delphi)

The Eleventh Doctor, Amy Pond and Rory Williams also met him and his mentor. (COMIC: The Chains of Olympus)

Works
The Library of St John the Beheaded contained some of his lost works. (PROSE: All-Consuming Fire)

Plato wrote The Republic, a piece of literature of which the First Doctor would acquire a first edition copy for his collection. (PROSE: The Edge of Destruction)