The importance of Posidonius of Apamea (c. 135–c. 50 BC) for the Roman intellectual life of the late Republic and the Empire (especially in its first two centuries) can hardly be overestimated. His philosophical and scientific work, of which we now have only fragments, ranged from the traditional fields of Stoicism – natural philosophy, logic, ethics (including moral psychology) – to the painstaking investigation of disciplines which either were considered by the earlier Stoics only in an insignificant way (meteorology, astronomy), or were completely beyond their interests (history, physical, mathematical, and ethnic geography). This encyclopedic approach won for him already during his lifetime and soon after his death the authority of the maximus omnium Stoicorum (Cic. Hort. fr. 50 Grilli = test. 33 E.–K.),1 among both professional philosophers and Roman dilettanti like Pompey. The influence of his innovative work, and the polemical reaction to it (the two often going hand in hand) is found in later centuries in moral philosophy and psychology (Seneca, Galen), natural philosophy, astronomy, and mathematics (Geminus, Seneca, Pliny the Elder, Cleomedes), as well as history and geography, both mathematical and physical (Caesar, Diodorus of Sicily, Strabo).