Unani Medicine, as said earlier, is based on the principles put forward by Hippocrates. He was the first person to establish that disease was a natural process, that its symptoms were the reactions of the body to the disease and that the chief function of the physician was to aid the natural forces of the body. He was the first physician to introduce the method of taking medical histories. His chief contribution to the medical reals is the humoral theory.

The humoral theory presupposes the presence of four humors Dam (blood), Balgham (phlegm), Safra (Yellow bile) and Sauda (black bile) in the body. The temperaments of persons are expressed by the words sanguine, phlegmatic choleric and melancholic according to the preponderance in them of the respective humors blood, phlegm, yellow bile and black bile. The humors themselves are assigned temperaments : blood is hot and moist phlegm cold and moist, yellow bile hot and dry, and black bile cold and dry.

Every person is supposed to have a unique humoral constitution which represents his healthy state. And to maintain the correct humoral balance there is a power of self-preservation or adjustment called Quwwat-e-Mudabbira (medicatrix naturae) in the body. If this powder weakens, imbalance in the himoral composition is bound to occur. And this causes disease. In Unani Medicine, great reliance is placed in this power. The medicines used in this system, in fact, help the body to regain this power to an optimum level and thereby restore humoral balance, thus retaining health. Also correct diet and digestion are considered to maintain humoral balance.