He identified four fluids in particular: blood, black bile, yellow bile, and phlegm. This later became the basis of the chemical imbalance theory used widely today.

Furthermore, not far from Hippocrates, the philosopher Plato would come to argue the mind, body, and spirit worked as a unit. Any imbalance brought to these compositions of the individual could bring distress or lack of harmony within the individual. This philosophical idea would remain in perspective until the seventeenth century. It was later