The Stoic Concept of Proneness to Emotion and Vice

According to an old view of Ian G. Kidd based on some passages from Galen's treatise 'On the Doctrines of Hippocrates and Plato', the Stoic concept of the soul's proneness to emotion and vice was formulated for the first time by Posidonius and became through Cicero a communis opinio in Roman Stoicism from the 1st century BC. Against this account the present contribution confirms, thanks to a new reading of a fundamental Galenic passage, that this concept was in some way already present in Chrysippus' reflexion and demonstrates, through the witness of Seneca's Epistle 94, that it had been professed even a generation before him by the dissident Stoic philosopher Aristo of Chios. Accordingly, the concept of proneness should be considered as a permanent tenet of Stoic philosophy dating back directly to the first generation of Zeno's disciples. This shows also, in line with Teun Tieleman's recent interpretation of Posidonian psychology, that not even in this point Posidonius substantially distanced himself from Early Stoicism.