The Greek philosopher Zeno of Citium (335-263 B.C.) was the founder of Stoicism. His teachings had a profound influence throughout the ancient world and in important respects helped pave the way for Christianity.
Zeno the son of Mnaseas, was born in the Cypriot town of Citium and may have been part Semitic. His education, however, was thoroughly Greek, and he went to Athens about 313 B.C., where he attended the lectures of various philosophers, including Crates the Cynic, Stilpo, Xenocrates, and Polemo. Crates was his most important early master, and his first book, the Republic, was Cynic in inspiration and viewpoint. He took what he thought was the best of his masters' teachings and developed a complete philosophical system of his own. His followers were at first called Zenonians, but the name Stoics, which derived from the Stoa Poikile where Zeno taught, proved more popular. He was greatly respected at Athens and was honored by the Athenians with a golden crown and a bronze statue. He was also on good terms with the king of Macedon, Antigonus Gonatas, and was invited to live at the court in Pella. He declined the offer, although he did send two of his followers. Diogenes Laertius, who wrote a biography of Zeno in the 3d century A.D., preserves the titles of several of his works, although all have perished. In addition to the Republic, these include Life according to Nature, On Appetite (or The Nature of Man), On Becoming, On the Doctrines of the Pythagoreans, On Problems Relating to Homer, On Art, Memorabilia, and the Ethics of Crates.
Zeno's philosophical system embraced physics, logic, and ethics. Its greatest strength lay not in the elaborate but false theories set forth as explanations for the make-up of the universe, but in the almost evangelical message of its ethics. Man, in Zeno's view, had the key to true happiness within himself. He must identify with Nature (or Zeus or Providence or the Cosmos, for all were used interchangeably) and strive for self-sufficiency, which meant the rejection of all the external goods and values men traditionally cherished. In place of these, the divine reason given to every person must be cultivated toward the understanding and acceptance of God's universe. Social position was unimportant, and it was possible for the pauper or the king to strive toward the Stoic goal. The true Stoic sage was aware of the laws of Nature and followed them willingly because a beneficent Providence was guiding events. Individual suffering and misfortunes were subsumed under a larger and more important good. The ultimate goal was apathia, a state in which a person was completely indifferent to all but his own divinely given understanding of things. Virtue was defined as knowledge and vice as ignorance. The path to virtue was not easy, however. It demanded tough discipline and strict control over natural feelings and reactions such as pleasure, lust, anxiety, and fear. It also demanded a great deal of study of both theory and practical science, for only through complete awareness of the truth of the material world could the Stoic sage come to that understanding which gave him happiness.
Stoic physics and logic followed Heraclitus, Aristotle, and the two Socratic thinkers Antisthenes and Diodorus. It was an eclectic system which mixed a corporeal universe with an ultimate divine reason. God, the divine and beneficent reason behind all things, was originally one and the same with Fire, the basis of the physical universe. Through an elaborate process of separation, God willed Himself apart from corporeality and caused the chain of events which we know as the history of the universe. At some specific moment in the future, He will take corporeality back unto Himself in a mighty conflagration. This process will repeat itself infinitely and history will repeat itself exactly an endless number of times. Man's freedom in such a totally predetermined chain of causation is possible only through the independence of his mind, which bears the same relationship to his body as does God to the corporeal universe. Through reason man may come to an understanding and acceptance of the way things are and may willingly comply with Nature. Ignorance of the truth leads to vain hopes and expectations, and the ignorant man is condemned to a life of blindness. It can be readily seen from the Stoic view of a beneficent God at work in a completely preordained universe that Stoicism was among the first philosophical systems to claim that this is the best of all possible worlds.
Zeno's successors as leaders of the Stoa were Cleanthes, Chrysippus, Zeno of Tarsus, Diogenes the Babylonian, Panaetius of Rhodes, Posidonius, and Hecaton. The Stoic system, with its emphasis on fortitude and discipline, appealed to the Romans and became the most widely accepted Greek philosophy among the Roman ruling classes. Greek and Roman writers in imperial times came to identify the good Roman emperors, such as Trajan, Hadrian, Antoninus Pius, and Marcus Aurelius, with the Stoic king, and the evil emperors, such as Caligula, Nero, and Domitian, with the depraved tyrant. Marcus Aurelius was the emperor who most obviously accepted Stoicism as a way of life, and his collection of personal memoirs bears eloquent witness to the appeal which Zeno's system had to a fine and sensitive mind.
With the demise of the city-states and the concomitant failure of the older and simpler religious views to satisfy men's new spiritual needs in a time of changing values, Zeno's philosophical teachings imparted a sense of worth and dignity to the lives of great numbers of men. The striking similarities between Stoicism and Christianity made it one of the important precursors of that religion in antiquity.
An excellent introduction to Zeno and the Stoic school is in Moses Hadas, ed., Essential Works of Stoicism (1961). A more critical summary of Stoic theory and teachings is in Eduard Zeller, Outlines of the History of Greek Philosophy, revised by Wilhelm Nestle and translated by L. R. Palmer (1955). Briefer treatments of Zeno are in the surveys of ancient philosophy, such as Gordon H. Clark, ed., Selections from Hellenistic Philosophy (1940), and Arthur H. Armstrong, An Introduction to Ancient Philosophy (1947; 4th ed. 1965).