Rational Explanations for Disease

The Ancient Greeks thought everyone had a mix of four humours in their body. They believed people became ill when this mix was unbalanced, so to make people better they tried to put this balance right. These ideas continued well into the Middle Ages.

In the 2nd Century AD, a doctor called Galen developed the idea of the Four Humours further. Besides bleeding and purging to get rid of excess humours, treatments based on his Theory of Opposites aimed to balance the humours by giving the patient the 'opposite' of their symptoms.