Plato (427-347 BCEE) was an Athenian philosopher in Ancient Greece and the author of Theaetetus. A student of Socrates, Plato also founded the first academy in the Western world, a forerunner to the modern university, in Athens.  Its most famous member, a student of Plato, was Aristotle (384-322 BCE). How much of Theaetetus represents Socrates’s views and how much represents Plato’s is hard to establish, as Socrates did not preserve his philosophy in written form. Nevertheless, Plato’s influence on Western thought and philosophy has been huge. His writings, via Neoplatonism, were critical in the development and codification of Christianity and the early Christian church. He is also credited with founding Western political philosophy through his work Republic.

His other major works, all of which are in dialogue form, and most of which feature Socrates as the principal character, include Symposium (385 BCE), Republic (375 BCE), and Phaedrus (370 BCE).

Socrates (470-399 BCE) was an Ancient Greek philosopher, the teacher of Plato, and the main protagonist of Theaetetus. As he produced no written texts, our ideas about who he was, and what he said and thought, come from others, principally Plato via his Socratic dialogues. However, other Greeks, such as his students Xenophon and Antisthenes, and playwright Aristophanes, also wrote about him.