Posidonius [addendum]

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Modern study of Posidonius has been transformed since the mid-1960s by the collection of ancient evidence compiled by Ludwig Edelstein and Ian G. Kidd (1972), and minutely analyzed by Kidd (1988, 1999), which contains only texts that name Posidonius explicitly. The picture presented is undoubtedly too narrow, and an accurate assessment of Posidonius's achievement and influence must await further study of other texts in which his influence may be reliably detected. But even the newly circumscribed picture has made it increasingly clear that Posidonius largely adhered to basic Stoic doctrines and principles and that his main innovations lie in his breathtakingly comprehensive effort to integrate both natural and human sciences into Stoic cosmology, epistemology, and ethics. His range was encyclopedic, and while the bulk of his massive output was in physics (embracing also metaphysics, theology, and the special sciences), there is little he neglected.

In metaphysics Posidonius sought to reconcile Stoic materialism with its quasi-dualist principles of matter and God (which are thoroughly blended together throughout the universe), and to explicate the incorporeal status of time, void, and bodily limits (points, lines, and surfaces). In logic relatively little is securely attested: work on the logic of relations and on axiomatic method in mathematics. He also analyzed the structure of scientific explanation (etiology): Subordinating mathematical sciences to philosophy, he emphasized material and teleological factors in ways that suggest Aristotelian influence (Rhodes, where he worked most of his life, had a tradition of Aristotelian studies, and Andronicus of Rhodes [first century BCE], a younger contemporary, had a prominent role in reviving study of Aristotle's treatises).

Posidonius's scientific work had substantial impact on many later Stoics (notably Lucius Annaeus Seneca, Cleomedes [fl. c. 100 CE], and Geminus [10 BCE–60 CE]) and on ancient science and philosophy more widely (including Strabo [c. 64 BCE–after 23 CE] and Galen). Spanning astronomy, meteorology, geophysics, and geography, his work shows a concerted effort to extend the scope and empirical basis of Stoic theories. Problems he tackled include the size and distance of the sun and moon, the size and climatic zones of the earth, eclipses, comets, rainbows, clouds, thunder, winds, earthquakes, volcanoes, hydrodynamics, and mineralogy. Especially impressive is his theory of oceanic tides, which he correlated with the daily, weekly, and annual periodic motions of the moon; detailed observation here revealed systematic links between celestial and terrestrial phenomena that exemplify the principle of cosmic interaction (sympathy) underlying Stoic determinism and its providential design.

In ethics Posidonius upheld the central doctrines of Stoic Eudaemonism: virtue is a form of knowledge, only it (and anything possessing it) is genuinely good, and it is entirely sufficient for happiness (eudaimonia). He also brought new rigor to Stoic psychology by subjecting previous accounts of emotion and emotional behavior to precise critical analysis. Tendentious evidence in Galen has convinced many scholars that Posidonius rejected the monistic psychology of Chrysippus in favor of a Platonizing dualism, but recent studies (Cooper, Tieleman) argue that he sought rather to defend Stoic intellectualism by analyzing the structure of human motivation more closely. Similar concerns are evident in his massive History (fifty-two books covering 146 to 80s BCE—from a Roman defeat of federated Greece to an invasion of Athens), where ethics and ethnography combine with climatology and geography to explain both customs and historical events.

Aristotle; Chrysippus; Eudaimonia; Galen; Plato; Seneca, Lucius Annaeus; Stoicism.

Edelstein, Ludwig, and Ian G. Kidd, eds. Posidonius. Vol. 1, The Fragments. New York: Cambridge University Press, 1972. The standard collection of ancient testimony.

Kidd, Ian G. Posidonius. Vol. 2, The Commentary. New York: Cambridge University Press, 1988. Meticulous analysis, with full reference to earlier scholarship.

Kidd, Ian G. Posidonius. Vol. 3, The Translation. New York: Cambridge University Press, 1999.

Theiler, Willy. Die Fragmente/Poseidonios. 2 vols. Berlin: de Gruyter, 1982. An insufficiently cautious collection of texts but often helpful for its commentary.

Algra, Keimpe. "Posidonius' Conception of the Extra-cosmic Void: The Evidence and the Arguments." Mnemosyne 46 (4) (1993): 473–505. Establishes his Stoic orthodoxy on some basic questions of cosmology.

Cooper, John M. "Posidonius on Emotions." In The Emotions in Hellenistic Philosophy, edited by Juha Sihvola and Troels Engberg-Pedersen. Dordrecht, Netherlands: Kluwer Academic, 1998. Argues that Posidonius's account has affinities with Plato but remains fundamentally Stoic.

Tieleman, Teun. Chrysippus' On Affections: Reconstruction and Interpretation. Leiden, Netherlands: Brill, 2003. Argues, contrary to prevailing views, that Posidonius sought to refine rather than undermine Stoic moral psychology.

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