Cleanthes

Cleanthes (c. 330–230 BCE) succeeded Zeno as head of the Stoa, giving its physics a fervent, almost devotional cast. His Hymn to Zeus — addressing the supreme god as the rational law pervading all things — is the noblest religious poem the school produced.

A former boxer who drew water by night to study by day, he held the cosmos to be a living, divine fire, and was succeeded in turn by his pupil Chrysippus.

Life and teaching

Cleanthes came from Assos, in the Troad. He arrived in Athens poor and supported himself by manual labour, working at night drawing water for gardens, and his diligence earned him the nickname “the second Heracles”. He studied with Zeno for many years and became head of the school on Zeno’s death in the 260s BCE. He was regarded as slow but steady, and ancient writers compared him to a hard writing tablet that takes impressions with difficulty but keeps them well.

His philosophical contributions were significant. He is credited with the Stoic concept of tension, the tensional movement of the fiery breath that holds bodies together, and he held that the sun is the ruling part, or hegemonikon, of the cosmos. In ethics he is reported to have formulated the goal of life as living in agreement with nature, and he maintained, against Chrysippus, that virtue once gained cannot be lost. He also held that all souls survive until the cosmic conflagration, whereas Chrysippus restricted survival to the souls of the wise. According to Plutarch, he thought the astronomer Aristarchus of Samos should be charged with impiety for moving the hearth of the cosmos by making the earth revolve.

The Hymn to Zeus survives because it was quoted in full in the anthology of Stobaeus. It praises Zeus as the ruler of nature who steers all things by law, and laments that the wicked, ignorant of the universal reason, pursue their own mistaken goods. Another short prayer — asking Zeus and Destiny to lead him where they will, since he will follow willingly or be dragged — was quoted by Epictetus and rendered into Latin by Seneca. Cleanthes is said to have died at a great age by fasting.