Posidonius of Apameia, the Stoic philosopher, was famous in his own time and continued to influence writers into the first and second centuries CE. Soon after, his writings seem to have been lost, and even his name is rarely mentioned. Known to modern historiography mainly from the mention of his views in Cicero, Strabo, Seneca, and Galen, he was considered from the Renaissance to the beginning of the nineteenth century as a minor figure in the development of Stoicism. Then his thought began to be discovered in an ever-increasing number of writers, who were believed to follow him although they do not quote him, and he was established as the mediator between the Orient and the Occident, the reconciler of philosophy with religion and mysticism, the foremost representative of dualism. In the early twentieth century the reconstruction of Posidonius's work through Quellenforschung ("source criticism...