Stoicism was founded by Zeno of Citium (334–262 B.C.E.), whose work was carried on by Cleanthes (331–322 B.C.E.), who was then succeeded by Chrusippus (c. 280–206 B.C.E.). The name “stoic’ came from the Stoa Poikile, or painted colonnade, where stoics first gathered in Athens. According to these early stoics, the entire world is a morally good organism, with different phases in which events operate according to divine reason, or logos. The sequence of events is predetermined by fate. Each world phase ends in a big fire and is then repeated in a continuous, neverending cycle.

Early stoic ethics held that only virtue is good, and only vice is bad. Other things, such as health or wealth, may be preferred, but they are morally indifferent. We each have a unique role in the world plan and our job is to learn what it is. Such learning creates concern for the self, which can and should be extended to close relatives and friends and, after them, all humanity. (The stoics may have been the first cosmopolitans.) Learning is based on assent to impressions, until all of a person’s thoughts become related and “unassailable by reason.” By counseling that we “assent to impressions,” the stoics meant that we should not deny anything that is presented to us as either a fact or an opinion but simply acknowledge its effect on us. Such stoic certainty formed the “dogmatism” opposed by the skeptics.