POSEIDONIUS (13o?-5o B.c.), nicknamed "the Athlete," Stoic philosopher, the most learned man of his time and perhaps of all the school. A native of Apameia in Syria and a pupil of Panaetius, he spent many years in travel and scientific researches in Spain (particularly at Gades), Africa, Italy, Gaul, Liguria. Sicily and on the eastern shores of the Adriatic. When he settled as a teacher at Rhodes his fame attracted numerous scholars; next to Panaetius he did most, by writings and personal inter course, to spread Stoicism in the Roman world, and he became well known to many leading men, such as Marius, Rutilius Rufus, Pompey and Cicero. The last-named studied under him (78-77) B.c.), and speaks as his friend.
The titles and subjects of more than twenty of his works, now lost, are known. In common with other Stoics of the middle period, he displayed eclectic tendencies, following the older Stoics, Panaetius, Plato and Aristotle. Unquestionably more of a polymath than a philosopher, he appears uncritical and super ficial. But at the time his spirit of inquiry provoked Strabo's criticism as something alien to the school era air toXo-yuclo Kai To ItpurTo7iWov, 67rEp EKiAbiovcriv ot. 1)12i-repot). In natural science, geography, natural history, mathematics and astronomy he took a genuine interest. He sought to determine the distance and mag
nitude of the sun, to calculate the diameter of the earth and the influence of the moon on the tides. His history of the period 146-88 B.C., in 52 books, must have been a valuable storehouse. Cicero made much use of his writings.
See Zeller, Philosophie der Griechen, iii. (in Eng. trans., Eclecticism, 56-70) ; C. Muller, Fragmenta historicorum graecorum, iii.; J. Blake, Posidonii Rhodii reliquiae (Leiden, 181o) ; R. Scheppig, De Posidonio rerum gentium terrarum scriptore (Berlin, 1869) ; R. Hirzel, Unter suchungen zu Ciceros philosophischen Schriften, i.—iii. (Leipzig, 1877) ; Thiaucourt, Essai sur les trait& philosophiques de Ciceron (1885) ; Arnold, Untersuchungen fiber Theophanes von Mytilene and Posidonius von Apamea (1882) ; Schmekel, Die Philosophie der mittlern Stoa (1892) ; I. Heinemann, Poseidonios' metaphysische Schriften (Breslau, 1921) ; K. Reinhardt, Poseidonios (Munich, 192i) and Kosmos u. Svmpathie, Neue Untersuchungen fiber Poseidonios (Munich, 1926) and P. Schubert, Die Eschatologie des Posidonius (Leipzig, 1927). Full bibliography in Uberweg, Grundriss der Gesch. der Philosophic, Bd. I (1926). See also STOICS.