or the universe was generated out of these four elements and their mutual attraction and repulsion. The conflict between these two schools of thought became manifest in their medical philosophies. Whereas, Alcmaeon argued that there were indefinite number of diverse qualities that made up the human organism, Empedocles contended that there were four concrete or substantial elements. Whereas it is Empedocles' medical philosophy that ultimately inspires the humoral doctrine of human nature, it is Alcmaeon's theory that underpins the medical therapeutic doctrine proposed in On Ancient Medicine (Group IV). Alcmaeon's argument that there are an infinite number of causes for disease that cannot be simply organized into categories is the basic operating assumption of empirical medicine. Therefore, medical knowledge continuously expanded thorough a firsthand experience and observation of the human organism within nature. It is in this light that On Ancient Medicine should be seen as an attempt by the advocates of the Alcmaeon and the empirical school of thought to respond to and critique the Empedoclean or humoral theory of medicine. On Ancient Medicine The basic arguments of On Ancient Medicine have three components. In chapters 1–19 the author responds to the supporters of the hypothesis theory of medicine. In so doing he argues that the exploration of medicine itself reveals the human organism as a blend of diverse substances or humors. Having set forth this humoral theory, he then critiques the hypothesis theory proposed by his opponents as being an oversimplified conception of the cause of disease. Against this backdrop, he discusses his own theory and method he employed in its discovery (chaps. 20–24). He then responds to the charge that ancient medicine is not a genuine medical art because it has limited accuracy. These arguments must be seen in the light of the author's theory of human physiology (chaps. 9–12). Chapters 1–19 The author is responding to the supporters of the hypothesis theory by arguing that medicine has a systematic character to qualify it as a tekhne (art, craft or science). This genuine tekhne depends on the knowledge of the physician attained through first-hand experience that enables him to both distinguish diverse treatments and to realize success in their skillful administration (1). Medicine should not proceed with hypotheses or generalizations; rather it should be rooted in experience and discovery. It should be empirical in its methodology. Hence, in chapter 2 the author argues that medicine's principle and