The Unani system is based on two theories, namely the Hippocratic theory of four humors and the Pythagorean theory of four proximate qualities. The four humors are blood, phlegm, yellow bile and black bile, and the four qualities are the states of living human body, namely hot, cold, moist and dry. They are represented as earth, water, fire and air. The Greek ideas were adapted by the Arabian physicians as eight working principles (umur-e-tabia) and included elements, temperament, humors, organs, life, spirit, energy and actions. The body is made up of simple and complex organs, which obtain their nourishment from the four humors mentioned earlier. These humors also have their specific temperament. In the healthy state of the body, there is equilibrium among the humors and the body functions in the normal manner as per its own temperament and environment. The disease condition is considered to be due to the imbalance between the humors and the treatment is given accordingly.

In this system of medicine, prime importance is given for the preservation of health. It is stated that six essential factors are required for the maintenance of healthy state. They are (a) air, (b) food and drink, (c) bodily movements and response, (d) psychic movement and repose, (e) sleep and wakefulness and (f) evacuation and retention. The human body is considered to be made up of six components, which have direct bearing on the health status of a person. They are (a) elements (Arkan), (b) temperament (Mijaz), (c) humors (Aklat), (d) organs (Aaza), (e) faculties (Quwa) and (f) spirits (Arwah). These components are taken into consideration by the physician for diagnosis and also for deciding the line of treatment. The Unani system of medicine aims at treating the cause of disease and not its symptoms. Hence, the complete history of the patient is recorded in addition to his pulse, urine and stool examinations.