Socrates

Socrates wrote nothing. Everything we know of him comes from his students Plato and Xenophon and from Aristophanes, the comic poet who mocked him. The son of an Athenian stonemason, he fought in the Peloponnesian War and otherwise spent his days talking with people in the agora, the gymnasia and friends' houses.

His method came to be called elenchus: ask for a definition, say of courage, then expose its contradictions with a chain of questions until the other person admits not really knowing. The Delphic oracle said no one was wiser than Socrates; he took it to mean that he at least knew that he did not know.

In 399 BCE Athens tried him for impiety and corrupting the young. He refused to beg and refused the escape his friends had arranged, saying that to flee would betray the laws he had obeyed all his life. He spent his last hours discussing the soul's immortality, then calmly drank the hemlock. That death became the founding myth of Western philosophy.