Stoicism (stōˈĭsĭzəm) [key], school of philosophy founded by Zeno of Citium (in Cyprus) c.300 B.C. The first Stoics were so called because they met in the Stoa Poecile [Gr., = painted porch], at Athens, a colonnade near the Agora, to hear their master Zeno lecture. He had studied with Crates the Cynic, and his own teaching included the Cynic adaptation of the Socratic ideals of virtue, endurance, and self-sufficiency. He added to them the explanation of the physical universe given by Heraclitus and something of the logic of Aristotle. The development and organization of Zeno's doctrines into a great system of metaphysics was the work of Chrysippus (c.280–207 B.C.), successor to Cleanthes. Among the acknowledged leaders of the Stoics in the following period was Panaetius of Rhodes, who in the 2d cent. B.C. introduced Stoicism into Rome. He and his pupil Posidonius sought to lessen the attacks of critics by mingling with the Stoic doctrines some of Plato's psychological views. Cicero, a pupil of Posidonius, was indebted to a work of Panaetius for the basis of his own treatise De officiis. The Romans, who had received Stoicism more cordially than they did any other Greek philosophy, can claim the third period as their own. To it belong the philosophers Seneca and Epictetus of Phrygia and the emperor Marcus Aurelius. Stoicism, with its roots in earlier doctrines and theories of the human person and the universe, built up an ideal of the virtuous, wise man. Regarding philosophy as divided into physics, logic, and ethics, the Stoics made logic and physics a foundation for ethics. The Stoics, especially Chrysippus, are renowned for their logic, which contains the first systematic analysis of how the truth value of a compound proposition depends upon the truth values of its components. The physical theory underlying Stoicism is materialistic. All that has reality is material. Force, which is the shaping principle, is joined with matter. The universal working force, God, pervades all and becomes the reason and soul in the animate creation. In their ethical creed, the Stoics accepted virtue as the highest good in life. They identified virtue with happiness, claiming that it was untouched by changes in fortune. "To live consistently with nature" was a familiar maxim among the Stoics. Only by putting aside passion, unjust thoughts, and indulgence and by performing duty with the right disposition can people attain true freedom and rule as lords over their own lives.
See J. M. Rist, Stoic Philosophy (1969); A. A. Long, ed., Problems in Stoicism (1971); A. A. Long and P. N. Sedley, The Hellenistic Philosophers, (2 vol., 1987); M. Reesor, The Nature of Man in Early Stoic Philosophy (1989).