“The idea of nature as implying a universal nexus of cause and effect comes to be made explicit in the course of the development of Presocratic philosophy”: G.E.R. Lloyd. “The conception of cause is borrowed from the language of medicine, as is clear from the word prophasis which Thucydides uses”: W. Jaeger. “The word aition is, from the Hippocratic writings on, a standard word for 'cause', and its relative aitia... meant a complaint or an accusation, but already by the time of Herodotus's book it can mean simply 'cause' or 'explanation'”: B. Williams.

These three distinguised scholars, distant though they are from one another in their intellectual orientations, seem to agree on the opinion that a precise and well-defined conception of causality is present in fifth-century philosophy, history, and medicine. This judgement is widely shared, but it needs to be corrected, or at least clarified and formulated, from two different but complementary perspectives.