An extension of Tai Chi, Bagua originated in Zhouyi, too. It is recorded in Zhouyi that “Therefore there is in the Changes the Great Primal Beginning. This generates the two primary forces. The two primary forces generate the four images. The four images generate the eight trigrams. The eight trigrams determine good fortune and misfortune. Good fortune and misfortune create the great field of action.”

“Therefore there is in the Changes the Great Primal Beginning” indicates that the essence of Zhouyi is Tai Chi, the initially chaotic state of the universe. “This generates the two primary forces” means Tai Chi divides into yin and yang, where yang is heaven and yin earth, with yin and yang being the unity of opposites. “The two primary forces generate the four images” means that yin and yang further divide into great yin, lesser yang, lesser yin and great yang, which correspond to four directions, four seasons etc. In the sentence “The four images generate the eight trigrams” , the eight trigrams, namely Bagua, are abstract in meaning, which can be simply understood as eight directions arranged in alternate yin and yang - Qian, Dui, Li, Zhen, Xun, Kan, Gen and Kun, corresponding to the eight natural phenomena of sky (heaven), lake, fire, thunder, wind, mountain and earth. Of the trigrams, Qian and Kun have very important places, which are the origins of all phenomena in nature and human society.

In ancient China, the eight trigrams overlapped and intersected into sixty-four trigrams with three hundred and eighty four points of intersection, on the basis of which good fortune and misfortune were determined.