Episode 77 – Cleanthes: The Water-Bearer

This episode shines a light on Cleanthes of Assos, the crucial but often overlooked successor to Zeno, who kept the fledgling Stoic school alive through sheer grit and intellectual dedication. Arriving in Athens as a poor boxer, he worked all night as a water-bearer to afford the fees to study philosophy by day, embodying the Stoic ideals of perseverance and self-sufficiency. This unwavering commitment gave him the moral authority necessary to lead the school after Zeno, ensuring its survival during a period of intense philosophical competition in Athens.

Cleanthes was a staunch defender of Stoic materialism, the belief that everything that exists, including the soul and God, must be physical. He argued that for two things to interact, like the mind and body, they must both be corporeal, a concept he illustrated with everyday examples like blushing from embarrassment or turning pale with fear. He saw the soul, or hegemonikon, as a physical substance—a fiery, intelligent breath called pneuma—and believed our emotions were actual physical alterations of this substance. This materialist view was not just an abstract theory; it formed the concrete basis for the Stoic belief that we could actively work on and improve our own minds.

This physical understanding of the mind led to Cleanthes's focus on the power of assent, the moment of choice when we agree with an impression. He famously, though perhaps too literally, described this as the soul being "stamped" by reality, like a signet ring in wax. While his student Chrysippus would later refine this model, Cleanthes established the core idea that our freedom and moral responsibility lie in this act of judgment. By rigorously training ourselves to only give assent to clear, rational impressions, we can avoid the faulty judgments that lead to destructive emotions and live a life in harmony with the rational order of the cosmos.