Ancient Greek medicine developed a tradition of naturalistic explanation for disease that was genuinely innovative even if its specific theories were wrong by modern standards. The Hippocratic tradition represents a deliberate move away from supernatural explanations of illness toward environmental, dietary, and constitutional accounts.

The Hippocratic Corpus — a collection of texts attributed to Hippocrates and his school but almost certainly the work of multiple authors over several centuries — establishes a clinical approach characterized by careful observation, prognostic reasoning, and therapeutic humility. The famous Hippocratic aphorism 'First, do no harm' may be apocryphal, but it captures a genuine Hippocratic emphasis on understanding disease processes rather than intervening aggressively.

The humoral theory — health as the balance of four humors (blood, phlegm, yellow bile, black bile) — was wrong but not stupid. It provided a systematic framework for understanding individual variation in health, the influence of environment and season on health outcomes, and the rationale for therapeutic interventions. The theory persisted in Western medicine until the 17th century not because of blind traditionalism but because it was flexible enough to accommodate clinical observations.

Galen of Pergamon (2nd century AD) systematized ancient medical knowledge in a way that dominated European medicine for 1,400 years. His anatomical work — based primarily on dissection of animals rather than humans, since human dissection was socially restricted in his era — was impressive but contained errors (misapplied from pig anatomy, for example) that were not corrected until Vesalius' systematic human dissection in the 16th century.