[The philosophical influences of Empedocles in the Hippocratic medical treatise De Natura Hominis].

The Hippocratic treatise De Natura Hominis (On the Nature of Man) has been very influential in the history of western medical thought from antiquity, because it argues the theory of four humors as the essential constituents of human body. There has been a traditional view on the theory among scholars that the author Polybos referred to Empedocles' philosophical doctrine of four elements as a model in the formation of the humoral physiology of his own. However, the theory of four humors, as compared with the doctrine of four elements, turns out to be different on the following points. 1) The four elements are introduced as substantial entities, which always remain self-identical, whereas the four humors change into one another, according to the degree of the four elemental qualities (Hot and Cold, Humid and Dry), which constitute their own nature. 2) In the Empedoclean doctrine, human nature comes into being emergently from the four elements, when they come together, or when they separate out of their primordial lump. In NH, the generation process seems to be dependent on human nature, which exists as the determinant of the conditions under which the generation can take place. 3) The Empedoclean cosmic cycle functions as a structural framework, within which the generation takes place. The cosmic system in NH has its own purpose of giving a causal explanation about how the four humors increase and decrease reciprocally in the human body, according to the alternation of the four seasons. These results will make us suppose that the philosophical influences of Empedocles on the theory of four humors remained within a very limited scope, although there are traces in some phrases and sentences as well as forms of argumentation in NH, which may be judged to be a reflection of the Empedoclean philosophical poems.