This chapter considers the deeper level of changes to thought processes that we can to an extent detect at the core of the shifting relationships between oral and written, poetry and prose in the Hellenic intellectual world of the late fifth century BCE. Significant discussions on this topic and on changes to so-called logoi or languages of explanation relevant to Hippocratic oratorical treatises of this period are introduced. The approach to examination of the relationship between form and content is outlined. The way in which Hippocratic expository prose develops as a new kind of logos in written prose influenced by earlier models is explored.