aitiología

Greek aitia meant cause, reason, or responsibility, and logos meant study or discourse. Aitiología was the discipline of tracing causes — of asking why something happened rather than simply describing that it happened. In medicine, Hippocrates and his school on the island of Cos (5th-4th century BCE) pioneered aetiological thinking by insisting that disease had natural causes discoverable by observation, rather than divine or demonic causes.

The Hippocratic treatise On the Sacred Disease, written around 400 BCE, explicitly rejected supernatural explanations for epilepsy — then called the 'sacred disease' because it was believed caused by gods. The author argued that epilepsy was a disease of the brain, with physical causes like all other diseases. This aetiological turn — asking physical causes, not supernatural ones — was a founding moment of Western medicine.

Galen (129-216 CE), the Roman physician who synthesized Greek medical thought, developed aetiological reasoning into a systematic method. His commentaries on Hippocrates and his own works established cause-seeking as the fundamental medical procedure. Islamic physicians Al-Razi and Avicenna built on Galen's aetiological framework, transmitting it to medieval European medicine.

Modern medicine's aetiological approach reached its fullest expression with Robert Koch's postulates of 1884 — the criteria for establishing that a specific microorganism causes a specific disease. Koch proved germ theory by identifying the causative agents of tuberculosis (1882) and cholera (1883). The ancient Greek question — what is the aitia, the cause? — now had a laboratory method.