Zeno of Citium

Zeno of Citium (not to be confused with the older Zeno of Elea) founded Stoicism, the most influential ancient philosophy after Plato and Aristotle. He taught in a painted colonnade on the Athenian agora — stoa poikile — which gave the school its name.

The Stoic claim is severe and beautiful. The universe is a single rational, providential whole, governed by logos. Your only genuine possession is your own judgment. Everything else — health, wealth, reputation, even your own body — is "indifferent": not bad, but not yours. Live in accordance with nature and reason, accept what cannot be changed, and you will be free.

Zeno's writings are lost. Stoicism survives through later voices: the slave Epictetus, the statesman Seneca, and the emperor Marcus Aurelius, whose private notebook (the Meditations) is the most-read Stoic text. In the 21st century Stoicism has had a startling popular revival.