Plato
Plato was an Ancient Greek philosopher and a disciple of Socrates. He studied Dialectics, 無知の知 (the concept of "knowing that you know nothing"), and Aporia. He was also the teacher of Aristotle.
Plato is well-known for his works such as Socrates' Defense, Nation, and Feast. One of his most significant contributions is the concept of Idea, which he proposed in his Theory of Ideas.