Main tenets of Stoicism

 

1. In physics, Stoicism contends that matter is in principle infinitely divisible, like the "infinitely divisible ooze" pictured. This put the founding Stoics at odds with the contemporary atomists They held, as well, that the active principle in the material world is pneuma, literally “breath,” but understood rather figuratively here. Pneuma exists as currents, and these currents combine in ways that give objects a stable, physical character. 
2. In cosmology, the Stoics see the natural world as a single rational and creative God, who is a material body, the body of the whole, of which all objects are, so to speak, organs.
3. In anthropology, Stoics see humans as parts of the natural world, with an important differentiating characteristic.  We are part of the world in that we are within the same bonds of cause and effect as the rest of it.  We are distinct in that we are aware of this situation.  This means that there are certain matters that are within our power: our own beliefs, judgments, desires, and attitudes. 
4. On what they called logic, and we might call epistemology, the Stoics contended that knowledge can be attained through reason. The mind receives impressions from the senses, but has the ability to judge them true or false (as representations of reality). These judgments are in themselves only opinions (doxa), though through reason we ground them, achieving clear comprehension and conviction (katalepsis). But a Stoic sage will want to check and verify his katalepsis with the expertise of his peers and the collective judgment of the species.
5. Then there is ethics. For the Stoic this is a matter of living in harmony with the universe (and so with God). This harmony requires recognizing what you have control of and what you do not, and detaching from any emotional state that depends upon what you do not control. Which is just about everything. Retrain one's own passions and recognize that the world will go its own way.