Cleanthes 330 BC – 230 BC

Cleanthes of Assos was a Greek Stoic philosopher who succeeded Zeno of Citium as head of the Stoa around 262 BC. Originally a boxer who arrived in Athens with little money, he supported himself by drawing water at night while studying philosophy by day. He gave Stoicism a distinctively religious cast, celebrated in his surviving Hymn to Zeus, in which he identifies the divine with the ordering reason of the cosmos. His writings are otherwise lost, but his reformulations were carried forward by his pupil Chrysippus.

Cleanthes was born around 330 BC at Assos in the Troad. He came to Athens, the tradition says, with very little money and supported himself as a night-time water-carrier while studying philosophy by day, first under the Cynic Crates and then for nineteen years under Zeno of Citium, the founder of the Stoa. On Zeno's death around 262 BC he succeeded him as second head of the school, a position he held for the next three decades.

Cleanthes was renowned in antiquity for the simplicity of his life, the slowness and persistence of his learning, and the religious tone he gave to Stoic doctrine. Of his fifty or more works only fragments and the great Hymn to Zeus survive intact. The Hymn addresses the supreme god as the pervading reason of nature whose law human beings are summoned to accept; with Seneca and Epictetus, Cleanthes offers the most explicit Stoic religious vocabulary of the early school.

He consolidated and transmitted the system of Zeno without the dialectical elaboration that his successor Chrysippus would supply, and he is the source of the famous Stoic image of the dog tied to the cart, willing or unwilling, to follow. He died around 230 BC, by tradition by voluntary starvation when an injury to his gum forced him to abstain from food and he chose not to resume eating once the wound had healed.