Posidonius and the Pneumatists: The Aetiology of Emotions and Diseases

Evidence from Galen and other sources permits us to explain the origins of the medical school of the Pneumatists against a Stoic, and in particular Posidonian, backdrop. Galen’s report at On Cohesive Causes that the school’s founder, Athenaeus of Attalia, studied with Posidonius, is reliable. Athenaeus found in Posidonius already a well-developed interest in medical issues. There is a clear connection between Athenaeus and Posidonius where the aetiology of disease is concerned. Here, as elsewhere, the information taken from Galen is indispensable as it throws light on Posidonius’ notion of predisposing cause in his analysis of the soul’s affections, or emotions. Evidence from Plutarch (Life of Marius 45.3-7) reflects Posidonius’ interest in the soul’s interaction with the body. Posidonius developed his analysis following Chrysippus who had already drawn an extensive analogy between mental and bodily states and presented philosophy as the medicine of the soul. Here Posidonius followed him to a greater extent than has so far been assumed. But in fact, his concern with medical matters reflects a more general feature of the work of this wide-ranging and scientifically minded Stoic. This makes him both a witness to and (in the case of Pneumatism) contributor to Graeco-Roman medicine.