Eight principles form four pairs, external and interior, cold and heat, deficiency and excess, and yin and yang. These four pairs, however, are not isolated and static but are correlated* and dynamic.

Relationships of the eight principles can be generalized into* four aspects: combined patterns, complex patterns, true or false patterns and pattern conversion as shown in Fig. 9-2.

In combined pattern, location and nature of disease appear simultaneously. Clinically, location and nature of disease are always combined and co-exist. For example, clinically there are exterior excess cold pattern, interior excess heat pattern, and many more.

Exterior, interior, cold, heat, deficiency and excess reflect the condition of diseases from different aspects. Exterior and interior indicate disease location, while cold and heat, deficiency and excess are used to indicate the nature of diseases. Cold, heat, deficiency or excess pattern cannot exist without the location of exterior or interior; and exterior or interior pattern cannot exist without the nature of cold, heat, deficiency, or excess.

Complex pattern is the pattern in which both exterior and interior are involved, or cold and heat exist simultaneously, or deficiency and excess exist simultaneously, or even cold, heat, deficiency and excess all exist simultaneously. When both exterior and interior of the body are involved simultaneously, it is called dual disease of exterior and interior*, a complex condition. Heat in the upper body with cold in the lower body, or cold in the exterior and heat in the interior are the examples of cold-heat complex*. Excess of pathogenic qi and debilitation of healthy qi occurring in the same disease on a patient is an example of deficiency-excess complex*.

True or false pattern refers to the pattern in which the nature of some symptoms and /or signs is contradictory to the nature of the disease, especially in a critical condition.

For example, true heat with false cold pattern arises when exuberant pathogenic heat entraps yang qi in the interior, manifested by cold limbs, aversion to cold or even shivering, impaired consciousness, and dark purple complexion. It would appear that the patient has cold pattern. On the other hand, through further examination you can find out that the patient also has high fever with the chest and abdomen hot to touch and hot breath exhaled from mouth and nose, fetid month odor, coarse breathing, strong thirst, short voidings of yellow urine, reddened tongue with yellow dry coating and rapid string-like pulse, which verifies that the patient truly suffers from heat binding in the body.

Pattern conversion is quite common during the process of disease. Excess pattern can change into deficiency pattern and deficiency pattern can change into excess pattern; exterior pattern can change into interior pattern and interior pattern can change into exterior pattern; and disease of cold nature can transform into heat nature, and vice versa.