This article presents a research on the occurrences of Pithanon in Galen’s On Doctrines of Hippocrates and Plato (PHP). Galen writes PHP to critique doctors, Peripatetics, and stoics about the powers that govern man. He considers his criticism to be justifiable because they have come to the wrong conclusions because of the wrong selection of premises. According to him, his opponents' conclusions are based on persuasive, mistaken, ambiguous or false assumptions. Pithanon is a key word he uses to identify one (...) of the premises that is applied by the stoics in order to prove their thesis about the hegemonikon. (shrink)