A (of Tyre?) in claiming that a providential deity – leading the diviner to select
the particular victim whose internal organs will correspond with the situation under enquiry
- guides the choice of sacrificial victim in extispicy (entrail divination). It is debated whether
Poseido ̄nios broke up the older Stoic unity of god-fate-nature into its individual com-
ponents and placed them hierarchically with god at the top, fate below, and nature in the
third tier, although this may only have been done for the purposes of grounding a particular
argument in defense of divination (Reydam-Schils). Poseido ̄nios accused E of athe-
ism, on the grounds that Epicurus’ inclusion of “gods” in his kosmos (gods who did not
and could not interact or interfere with the workings of the world) was no more than a
token gesture designed to make his philosophy less unpalatable to the masses.
Poseido ̄nios also made novel and important contributions in many areas, including his-
tory, geography, meteorology, cosmology, psychology, and mathematics. G (PHP
8.1.14: CMG 5.4.1.2, p. 482) calls him the “most scientific” of the Stoics. S (Books
1 – 3) discussed his work in geography at length. Poseido ̄nios is reported to have estimated
the circumference of the Earth at 180,000 stades, a significantly smaller figure than
E’ 252,000 stades. In meteorology, he wrote on the causes of hail, snow,
winds, storms, thunder, lightning, rainbows, earthquakes, halos and parhelia. He argued
influentially that tides were caused by winds affected by the Moon (cf. S
S). Poseido ̄nios seems to have gone to some length to clarify the methodological
differences between philosophy generally and particular sciences like astronomy. He is
reported to have constructed a celestial globe. He estimated the sizes and distances of the
Sun and Moon, and a few fixed-star observations are credited to him. For Poseido ̄nios, the
Sun is larger than the Earth, a sphere, and composed of pure fire. The Moon was composed
of a mixture of fire and air, and its opacity was caused only by extreme thickness. He also
wrote on eclipses and comets. In mathematics, he contributed to the foundations of geo-
metry, and composed a book (quoted at some length by P in his Commentary on the First
Book of Euclid’s Elements) to counter Z S’s critique of geometry.
Gale ̄n reports (PHP 5.7.1–10: CMG 5.4.1.2, pp. 336–338) that Poseido ̄nios broke with
earlier Stoics and followed P and A in dividing the faculties of the soul into
three: thinking, desiring, and being angry. But Poseido ̄nios, on Gale ̄n’s account, broke with
Plato in situating all three faculties in the heart rather than in separate locations in the body.
The extent and depth of Poseido ̄nios’ use of Plato is still debated.
Ed.: Edelstein and Kidd (1972–1999).
G. Reydams-Schils, “Posidonius and the Timaeus: Off to Rhodes and Back to Plato?” CQ 47 (1997)
455 – 476; A.D. Nock, “Posidonius,” JRS 49 (1959) 1–15.
Daryn Lehoux
Poseido ̄nios of Corinth (325 BCE? – 175 CE?)
Mentioned by Athe ̄naios, Deipn. 1 (13b), in a catalogue of authors of Halieutika. He lived
probably before O K.
RE 22.1 (1953) 826 (#5), R. Keydell; SH 709; A. Zumbo, “Ateneo 1, 13b–c e il ‘canone’ degli autori
alieutici,” in P. Radici Colace and A. Zumbo, Atti del Seminario Internazionale di Studi “Letteratura
scientifica e tecnica greca e latina” (2000) 163–170.
Claudio Meliadò
POSEIDO ̄NIOS OF CORINTH