The Meaning of Tai Chi
A contemporary philosopher, Dr. Nie Zhi-fei explained "Tai-chi can be treated as the driving force of the universe, which generates two poles (Yang, Yin), then evolving the four phases (sky, earth, men, and matter), which then produce the eight sections (sky, earth, men, matter, time, space, material and spirit). They give rise to all kinds of activities in the earth."
(Seen in the Principle of Tai-chi Chuan, 1980)