POSIDONILTS, a distinguished Stoic philosopher, the inost learned man of his time (e. 130-50 n.c.) and per-haps of all the school ; by birth a Syrian from Apamea, a pupil of Parnetius, he spent after his tea,cher's death many years in travel and scientific researches in Spain (particu-larly at Gades), Africa, Italy, Gaul, Liguria, Sicily, and on the eastern shores of the Adriatic. When be settled as a teacher at Rhodes his fame attracted numerous scholars ; next to Pametius he did most, by' writings and personal intercourse, to spread Stoicism in the Roman world ; lie became well known to many of the leading men, as -Marius, Rutilius Rufus, Pompey, and Cicero. The last-named studied under him (78-77 n.c.), and speaks as his warm admirer and personal friend.
Strabo mentions Min as a contemporary. The date of his birth has not been fixed ; it may have been 135, 130, or 125 B. c. ; accord-ing to Lucian, he lived to be eighty-four. Ile visited Rome - e.g., in 86 B.C. ou an embassy ; but it is doubtful if he ever resided there as a teacher. Ilis works, now lost, were written in an attract-ive style and proved a mine of information to later writers. The titles and. subjects of more than twenty of them are known. In common with other Stoics of the middle period, he displays eclectic tendencies. His admiration for Plato led him to write a comment-ary on the Tinixtts ; in another way it is shown by important modifications which he made in psychological doctrine. Unques-tionably more of a polymath than a philosopher, lie appears to us uncritical, or credulous even, and superficial. But at the time his spirit of inquiry provoked Strabo's criticism as something alien to the school (Td CIITLOX07LIC01, /MI Ta dpUTTOTali-01,, 67r•Ep bocXivovaa, al ill..cgrepot). In natural science he took a genuine interest, as his contributions to geography, natural history, mathematics, and astronomy sufficiently attest. He sought to determine the distance and magnitude of the sun, to calculate the diameter of the earth and the influence of the moon on the tides. His history of the period from 146 to 88 B.C., ill fifty-two books, must have been a valuable storehouse of facts. Cicero, who submitted to his criticism the memoirs which he had written in Greek of his consul-ship, made use of writings of Posidonius in De Katura DCOM71? b. ii., and De Dirinatione, b. i., and the author of the pseudo-Aristotelian treatise De Mundo also borrowed from him.
Zeller, Philosophie der Criechen, iii. 1, 570-584 (in Eng. trans., Eclecticism, 56- 70) ; C. Willer, Fraymenta Historicorum Ortreorum,iii. 245-296 ; J. Bake, Posidonii Ithodii Reliquire, Leyden,1810 (a valuable monograph); H. Scheppig, De Posidattio perm gentium terrarum scriptore, Berlin, 1869 ; R. Hirzel, Untersuckungen Ciceros philosophisclien Schriften, i. 191 sq. ; ii. 257 sq., 325 sq., 477-535, 756-789 ; iii. 342-378 (Leipsic, 1877). See STOICISM.