Cleanthes (331–232 BC)

The Greek philosopher Cleanthes of Assos played a leading role in the formation of Stoicism. He was at once the most physicalist and the most religious of the Stoics. Pupil, and eventual successor (in 262), of the school’s founder Zeno, he wrote numerous philosophical works, including some poetry. In particular, he developed the notion of fire as the world’s governing principle.