Tao te Ching: chapter 66
The mutual attraction between the yin and yang meridians generates an alternating energetic rotation analogous to the dynamic balance represented in the Tai Ji symbol. Consider how kinetic energy is generated by a bicycle rider. The continuous rotation of the wheels creates the necessary speed and momentum to keep the bicycle balanced and moving forward. The same logic of kinetic energy can be applied to the dynamic balance of the Tai Ji symbol. The force created by the attraction of polar opposites, yin and yang, shifts the body from a state of imbalance to a state of balance.
( excerpt: Dr. Tan's Strategy of Twelve Magical Points)
Tao te Ching: chapter 12