Annual Host-Qi Model of the Three Yin and Three Yang

Opposed to, and conceptually orthogonal with, the guest-qi model representing variable disturbance is the annual host-qi model of the Three Yin and Three Yang. Within the framework of the study of Heaven and humanity, host qi preserves the constant baseline in the principle of constancy and change—the element of constancy. It represents the basic natural order of terrestrial climate that recurs year after year. Host qi divides the year into six periods, from the initial qi through the terminal qi, each governing sixty days. Its fixed symbolic sequence is: Jueyin → Shaoyin → Shaoyang → Taiyin → Yangming → Taiyang. Its starting point is also strictly specified: the cycle must begin precisely at the solar term Great Cold (Dahan). Classical support for this model is found in passages such as the “Discourse on the Manifestations of the Six Seasonal Divisions” in the Huangdi Neijing: Suwen. The dialogue refers to the “six-by-six divisions” and to completing six periods in the circuit of heavenly qi. In this interpretation, the numerical structure—10 × 6 = 60 in the sexagenary cycle and 60 × 6 = 360 days—describes the annual rotation of host qi.