One Qi, Yin-Yang, Clear and Turbid, and the Pivot of Central Qi

Modern researchers have already tried to find suitable mathematical language for describing the motion of spiral curves associated with Taiji. What the ancients were attempting to describe as qi-transformation can be understood as recurring trajectories taken by qi as it moves between Heaven and Earth.

Several features are emphasized:

A. Two opposing tendencies—outward expansion and inward contraction—act as the basic drivers of change. These correspond to Yang and Yin.

B. When Yang predominates over Yin, expansion dominates. When Yin predominates over Yang, contraction dominates.

C. The direction of motion may be forward or reverse, depending on the observer’s frame of reference.

D. When Taiji rotates, the axis that runs through the direction of motion is the central axis. In a typhoon, this can be compared to the axis through the eye of the storm. In Taijiquan, it can be compared to an elastic axis extending from the heel through to the fingertips.

E. When viewing the plane of Taiji rotation, different phase intervals of the rotation correspond to the different stages of the Five Phases.

F. The beginning of expansion is Wood; expansion at its maximum, when the radius is also greatest, is Fire. The beginning of contraction is Metal; contraction at its maximum, when the radius is smallest, is Water.

G. Earth appears during the transitions between these four stages. This is the model in which Earth “irrigates the four directions” (see the Spacetime section).

H. Circular motions at different time scales can all form Taiji-like spirals. Their differences lie mainly in temporal period and spatial radius.

I. Why a spiral? If two circular motions with sufficiently different periods are superimposed, the tangent motion of the longer-period cycle appears nearly linear relative to the shorter-period cycle. Superimposing the shorter circular motion on that longer movement, and observing from far enough away, produces a spiral-like trajectory.

Readers may compare this with the “Diagrammatic Exploration of Origins” compiled by the elder Chen Dingsan in Exploring the Sources of Medicine. The two are describing the same general idea: the movement of Taiji.

Diagrammatic Exploration of Origins

Before Yin and Yang are differentiated, one qi is mixed and condensed. Qi contains Yin and Yang, and therefore has clear and turbid aspects. The clear floats and rises; the turbid sinks and descends. Rising is Yang and descending is Yin. Once Yin and Yang occupy different positions, the Two Modes are established. Between clear and turbid is what is called Central Qi. Central Qi is the pivot of the rising and descending of Yin and Yang, and this is what is called Earth. When the pivot moves, clear qi turns to the left and rises, becoming Fire and heat; turbid qi turns to the right and descends, becoming Water and cold. When the rising is only halfway and has not yet become Fire, it is called Wood qi. When warming ascent reaches its extreme, accumulated warmth becomes heat and transforms into Fire. When descending is only halfway and has not yet become Water, it is called Metal qi. When cooling descent reaches its extreme, accumulated coolness becomes Cold and transforms into Water.