I ching said the weather.

Tracing the origin of hexagrams ── Yin-Yang classification of sixty-four hexagrams

The essence of the Book of Changes is the unity of opposites of Yin and Yang, and the mystery is also in Yin and Yang.

Sixty-four hexagrams are divided into yin and yang. Fang Jing has already discussed this point:

Yang divination: Gan, Yi, Bi, Wu, Xun, Xiao beast, Ke, Yi, Gen, Ben, Da beast, Loss, Kun, Fu, Pro, Tai, Zhen, Yu, Jie, Heng, Hui, Kun, Cui, Xian, Kan, Kun.

Yin hexagrams: viewing, peeling, gold, being big, naive, gnawing, eating, squatting, walking, crouching, gradual, being big and strong, squatting, needing, comparing, rising, um, biggish, following up, being modest, being small, being younger, and reforming.

The basis of this classification has not been carefully investigated by predecessors, but the results are difficult to be recognized intuitively. It is simply unacceptable that such hexagrams as Kun hexagrams and Kan hexagrams should be classified as Yang hexagrams. In fact, it seems that it has not been recognized by future generations, so it has no practical value. But later generations could not solve this problem, and the problem was shelved for two thousand years.