This thesis looks to re-evaluate the East Greek intellectual view of non-Greeks in the middle to late fifth century. To do this I examine how ethnic difference is understood in the Hippocratic treatise Airs, Waters, Places (as well as the rest of the fifth-century Hippocratic corpus) and Herodotus' Histories, which together represent the new ethnographic thought of the fifth century. I will argue that neither author understood there to be any essential difference between Greeks and non-Greeks, nor represented non- Greeks as anti-Greeks, as many scholars today hold. Furthermore, I will argue that the idea of a Greek/barbarian dichotomy was to a considerable extent a construction of Athenian ideology, which stood in contrast to an East Greek cosmopolitanism that understood ethnic difference not in terms of differences in nature but of cultural variation within a common human condition. / Thesis / Master of Arts (MA)