Posidonius (135–51? BCE)
Posidonius of Apameia, the Stoic philosopher, was famous in his own time and continued to influence writers into the first and second centuries CE. Soon after, his writings seem to have been lost, and even his name is rarely mentioned. Known to modern historiography mainly from the mention of his views in Cicero, Strabo, Seneca, and Galen, he was considered from the Renaissance to the beginning of the nineteenth century as a minor figure in the development of Stoicism. Then his thought began to be discovered in an ever-increasing number of writers, who were believed to follow him although they do not quote him, and he was established as the mediator between the Orient and the Occident, the reconciler of philosophy with religion and mysticism, the foremost representative of dualism. In the early twentieth century the reconstruction of Posidonius's work through Quellenforschung ("source criticism") was replaced by a reconstruction based on the inner form of his thought, and Posidonius was represented as a visual thinker, the defender of monism, the proponent of the doctrines of cosmic sympathy and vitalism, and the last Hellenistic philosopher. Both interpretations pay little attention to the fragments preserved under the name of Posidonius and therefore remain largely conjectural. What will be said here is based exclusively on the attested material.
This material leaves no doubt about the fundamentally dualistic character of Posidonius's system. His ethics, which is the best-known part of his thought, teaches, contrary to the general Stoic dogma, that passions are not simply false judgments but an irreducible force in human nature. This distinction is also echoed in Posidonian physics in the again unorthodox definition of matter as endowed with its own form and quality, which is merely reshaped and remodeled by divine reason. His logic establishes reason as a criterion of truth independent of sense perception. On the other hand, the duality of matter and reason is bridged by the realm of mathematical forms; among the Stoics only Posidonius was a mathematical realist. The macrocosm and the microcosm are in the end viewed as gradated, as hierarchies as it were, in which reason governs the subordinate irrational forces. God pervades the world; the passions follow the leadership of rational insight; man is here to contemplate and to act.
The Platonic and Aristotelian elements in this Stoicism were noted even by ancient critics. In Posidonius's opinion the founders of the Stoa, Zeno and Cleanthes themselves, had been Platonizing and Aristotelianizing. The strict monism of the school was due to Chrysippus, whose work Posidonius thought had to be undone. Yet although Posidonius harked back to the older teaching and in this sense remained in the Greek tradition—he was innocent of the later Orientalizing—he undoubtedly made an original contribution to philosophy. His ethics is a greatly refined analysis of the emotions that refutes the rationalistic position by pointing to its inner inconsistency and its inconsistency with observed facts. He stressed the importance of the will. Although only a few details of his physics can be rediscovered, it is clear that he was intent on explaining things; he was famous for his etiologies, and he carefully distinguished the various causes, assigning first place to teleology. Cosmic sympathy is but one of the factors he invoked in his exegesis of nature. His logical investigations furthered the understanding of syllogistic thinking, which seemed to him validated not by linguistic connections but by implied axioms. In short, his system marks a step forward in the history of Greek rationalism, and this is in accord with Posidonius's belief in the gradual development of knowledge and in the idea of progress, which he, like so many earlier Greek rationalists, upheld.
Posidonius's contributions were, however, not restricted to the field of philosophy proper. He wrote a history of his own time and in it, if not separately, dealt copiously with the rise of civilization, which he claimed began with practical inventions made by philosophers. In the historical process itself he detected the dominance of freedom over circumstance. Several of his books were devoted to natural sciences, such as astronomy and meteorology; he also investigated problems of mathematics and of military tactics. Perhaps the greatest significance of these works lies in the fact that they do not isolate scholarly and scientific research but put it in a philosophical framework. Events are seen as part of the history of the cosmos. Scientific explanations are hypotheses, the correctness and adequacy of which must be judged through philosophical reflection. It was as a philosopher that Posidonius felt impelled to reject the heliocentric theory in favor of the geocentric theory. Although he erred in this respect, he did enforce the idea of the hypothetical character of all scientific knowledge and did restore the unity of the sciences which Hellenistic thought had destroyed.
The stoa of the empire, initially influenced by Posidonius, tended more and more to follow Chrysippus. Thus, the philosopher Posidonius soon lost importance. His scientific writings kept the Greek heritage alive much longer and carried it, through Seneca's Naturales Quaestiones, into the Middle Ages. If one judges his achievement and his influence, one cannot compare him with Plato, Aristotle, or Democritus or with Zeno, Epicurus, or Plotinus. It is fair to say, however, that his personality, which he allowed to intrude into his work, makes him one of the most attractive figures among ancient philosophers. He was a man of dignity and not without a sense of irony and humor. He lived the dogma he preached, studying and teaching as well as participating in the political affairs of Rhodes, his adopted city. The variety of his gifts is amazing—his dialectical skill, traced by Galen to his mathematical erudition; the keenness of his powers of observation of men and things, which is especially marked in his reports on the travels that took him throughout almost the whole of the then-known world; and the strength of his analytical ability, along with his love of literature and art. It was perhaps the universalism of his nature that made it possible for him not only to attempt a new explanation of the universe in all its aspects, doing justice to both man's cognitive and his practical concerns, but also to root human existence—for the last time in antiquity, it seems—in the world of reality without depriving this world of the reign of human reason, which he considered of the same nature as the divine spirit ruling the cosmos.
See also Aristotelianism; Aristotle; Chrysippus; Cicero, Marcus Tullius; Epicurus; Galen; Hellenistic Thought; Leucippus and Democritus; Mysticism, History of; Plato; Platonism and the Platonic Tradition; Plotinus; Rationalism; Renaissance; Seneca, Lucius Annaeus; Stoicism; Vitalism; Zeno of Citium.
The approach of Quellenforschung has been criticized, and criticized fairly, by J. F. Dobson, "The Posidonius Myth," in Classical Quarterly 12 (1918): 179ff. For Posidonius as a monist see K. Reinhardt, Poseidonios (Munich: C.H. Beck, 1921); see also his Kosmos und Sympathie (Munich: C.H. Beck, 1926) and A. Pauly and G. Wissowa, Realencyclopädie der classischen Altertumswissenschaft, Vol. XXII (Stuttgart, 1953), Part I, Cols. 558–826. I. Heinemann, Poseidonios' metaphysiche Schriften, 2 vols. (Breslau, 1921–1928), considers Posidonius especially in relation to his predecessor Panaerius.
For a reconstruction of Posidonius's philosophy according to the attested fragments see Ludwig Edelstein, "The Philosophical System of Posidonius," in American Journal of Philology 57 (1936): 286ff. For the historical fragments see F. Jacoby, Die Fragmente der griechischen Historiker, Vol. II, No. 87 (Berlin: Weidmann, 1926). The collection of fragments by I. Bake, Rhodii Reliquiae Doctrinae (Leiden, 1810), is antiquated.
Ludwig Edelstein (1967)