Overview

The "Doctrine of the Four Humors" dominated the theory of health, illness, and personality from the time of Empedocles (490-430 B.C.) until the eighteenth century, when bloodletting was finally ended. The doctrine taught that four basic elements comprised all matter: fire, earth, water, and air. Each element had two qualities. For example, fire was hot and dry, earth was dry and cold, water was cold and wet, and air was wet and hot. Based on that structure, the human body was believed to have four humors corresponding to these natural elements: blood with air, black bile with earth, yellow bile with fire, and phlegm with water. The Greek physician Galen later added personality types to go with each humor.

Background

The doctrine's origin can be traced to a number of unrelated but similar theories from ancient...