The Early Stoa
History
The founder of Stoicism was Zeno, b. 336/5 at Citium in Cyprus, d. c. 264/3 at Athens. First came to Athens c. 315-313, read Xen. Memorabilia & Plato's Apology, was filled with admiration of Socrates' characer. After studying with several different philosophers, of different philosophical schools, he founded his own school. He lectured in the stoa poikile (the "painted stoa") from which his school takes its name. We posess only fragments of his writings.
Zeno was succeeded in his leadership of the school by Cleanthes of Assos (331-30-233-2) and by Chrysippus of Soloi in Cilicia (281/278-208-205), who was called the second founder of the school because of his systemization of Stoic doctrines. (Diogenes Laertius: "If there hadn't been Chrysippus, there wouldn't be a Stoa.") He is said to have written more than 705 books, and to have been an excellent dialectician, but not a prose stylist.
Chrysippus was succeed by Zeno of Tarsus and Diogenes of Seucia. The latter came to Rome in 156/5, together with two other philosophers (including Carneades) on a diplomatic mission from Athens. They gave lectures in philosophy, which excited the admiration of the youth, but the displeasure of Cato, who advised the Senate to get rid of them as soon as possible. Diogenes was succeeded by Antipater of Tarsus.
Cosmology
Stoics draw from Heraclitus the notion of the Logos governing the cosmos, and fire as the arche from which everything is made. The primordial fire they identify with God and Logos; it is material, and the world is created out of transformations of the divine substance. Some of the fire retains its primordial state, this is the "soul" or consciousness of the world, while the "transformed' fire is God's body.
Stoics argue for the existence of a divine principle from design, beauty, etc. They also point out that since nature's highest creation, man, has consciousness, the whole cosmos, which is greater than man, cannot possibly lack something that he lacks.
God, the Logos, contains within himself all the active forms of existent things (borrowing a notion from Platonism), the spermatikoi logoi, which operate on passive nature to create the cosmos.
Stoics also taught that the universe is cyclically destroyed in a great conflagration in which everything reverts to primordial fire, and is cyclically re-created.
Ethics
God rules the universe providentially, planning everything for the good of man. The Stoics believe in a limited form of determinism, in which, although all our actions are controlled by providence, we are free in our attitudes either to accept or to fight against our fate. The point of Stoic ethics, therefore, is to cultivate a right attitude toward our actions and toward the things that happen to us. This is often expressed by notions of being "in harmony with nature," nature, providence, and fate being, finally, only different aspect of God. cf. Seneca, Ducunt volentem fata, noletnem trahunt.
Actions in themselves are seen as morally indifferent; the moral component lies entirely in intentions and attitudes. Moral virtue is the only true good; the cardinal virtues are phronesis ("moral insight"), courage, temperance, and justice. These virtues all fall or stand together, so that you must either have all of them or none of them. This leads to the doctrine that one is either morally good, or not; the only person who can be said to be good is the "wise man" who posesses all of the virtues perfectly.
Another component of Stoic ethics is the emphasis on lack of passions (apatheia) for virtue; the wise man is without passions, which are considered only a hindrance to the attainment of virtue. Later Stoics admitted that some passions are acceptable, or good, but they remained deeply suspicious of strong feeling. The attainment of perfection then, is largely a process of learning to rule one's self, namely, to rule the passions. Seneca: Innumerabiles sunt, qui populos, qui urbes habuerunt in potestate, paucissimi qui se.
The Middle Stoa
"In the second and third centuries before Christ the Stoic philosphers show a marked tendency to Eclecticism, admitting Platonic and Aristotelian elements in the School and departing from orthodox Stoicism. They were impelled to this course, noT only by the attacks levelled against the Stoic dogmatism by the Academicians, but also by their contact with the Roman world, which was much more interested in the practical application of philosphic doctrines than in speculation. The dominant names of the Middle Stoa are those of Panaetius and Poseidonius." (Coppleston, p. 421)
Panaetius of Rhodes (c 185-110) lived for some time in Rome, where he interested the younger Scipio and Laelius in Greek philosophy and greatly influenced the Roman historian Q. Mucius Scaevola, and the Greek historian of Rome, Polybius.
He allowed that the end of life of ordinary men is the rational perfection of their individual nature, thus allowing for some degree of virtue below that of the "wise man." He also rejected divination and astrology (which the earlier Stoics had accepted as being perfectly congruent with the notion of an ordered, connected, providential universe), and rejected popular theology.
Poseidonius of Apamaea (135-51). Cicero heard him lecture in 78 B.C. His works have disappeared, but he has been called "the most universal mind that Greece had seen since the time of Aristotle." He believed in a sympatheia between all parts of the cosmos; the world is a hierachy of grades of being, from inorganic material to God. He believed that the sub-lunar realm was perishable and mortal; the supra-lunar, imperishable and divine. Man is the link (desmos) that binds them, having a divine soul and a perishable body (cf. Cicero De Officiis). The human soul for P. was a fiery pneuma, immortal for as long as the sub-lunar realm should last, but perishing in the conflagrations affecting that realm. (P.'s teaching here is a modification of the early Stoa on conflagrations, and Panaetius', who rejected the whole idea; the supra-lunar realm is imperishable.) Poseidonius re-affirmed the validity of divination (cf. sympatheia), and also believed in the existence of spriritual beings (daimones).
*Source: Fr. Frederick Copleston, S.J.: A History of Philosophy, vol. 1, Greece and Rome.