The chapter focuses on the methodological debate between Empiricist and Rationalist schools of medicine, as portrayed in Galen’s early treatise On Medical Experience (Med.Exp.). This dense and philosophically-sophisticated text, preserved for the most part only in an Arabic translation, supposedly presents the substance of a dispute, witnessed by the young Galen, between his Rationalist teacher Pelops and an Empiricist opponent, about the respective roles of experience and reason in medicine. Analysing the arguments on both sides, in particular as they concern the question of inductive generalisation and the nature and validity of the empirical procedure known as epilogimos, the chapter shows how Galen’s presentation of a sequence of responses and counter-responses between the two protagonists serves to prefigure his own complex and hugely influential synthesis of the empirical and rationalist procedures in his own mature methodology.