Chrysippus 279 BC – 206 BC

Chrysippus of Soli was a Greek philosopher and the third head of the Stoic school, often regarded as its second founder. He was an extraordinarily prolific writer, credited in antiquity with more than seven hundred works, almost all of which are now lost. He systematized Stoic logic, physics, and ethics, developed propositional logic well beyond Aristotle, and defended Stoic determinism while attempting to preserve human moral responsibility. The ancient saying ran: "If there had been no Chrysippus, there would have been no Stoa."

Chrysippus was born around 279 BC in Soli in Cilicia. He came to Athens as a young man, lost his inherited fortune in a lawsuit, and turned to philosophy, attending the lectures of the Academic Arcesilaus before attaching himself to Cleanthes, the second head of the Stoa. On Cleanthes's death around 230 BC he succeeded him as the school's third head and held the position for the rest of his life.

Diogenes Laertius credits him with more than 705 books — none has survived intact — covering logic, physics, ethics, and the interpretation of poetry. Through hundreds of fragments preserved in Plutarch, Galen, Cicero, and the Stoic doxographies, modern scholars have reconstructed an enormously detailed system: a propositional and modal logic centuries ahead of its rivals, a physics of pneuma and continuous causation, and a fully argued ethics of assent and the passions.

Ancient writers said that without Chrysippus there would have been no Stoa, and most of what later Stoics, including Seneca, Epictetus, and Marcus Aurelius, took for granted as Stoic doctrine in fact descends from his pen. He is reported to have died around 206 BC, by one tradition from laughing too hard at his own joke about a donkey eating figs.