The essence of the Book of Changes can be summarized in one sentence.

The first sentence is: "first frost, go to the ice". Literally, when you step on the thin frost, you should know that it is not far from freezing. And its actual meaning is "walking on thin ice with fear" in the Book of Songs, which tells us to be vigilant and know how to plan ahead.

The second sentence is "straight, square and big". Zhou Wuwang's emphasis on being "straight, square and big" tells us to be "straight, square and big", but it is not easy to achieve these three points. This is the essence of the three sentences of the Book of Changes.

The third sentence "including Zhang Kejian". From Yijing Kunsanliu: including Zhang Kezhen. Or from the king, there is no end. "Including Zhang Kejian" means to have a strong connotation. In this society that likes to seek the outside world, many people finally make themselves look like human beings and ghosts in order to compete for fame and profit.

Extended data:

The Book of Changes is an outstanding representative of China culture. Vast, subtle and all-encompassing, it is also the source of Chinese civilization. Its content involves philosophy, politics, life, literature, art, science and many other fields. It is the first of the group classics and a classic of Confucianism and Taoism.

The Book of Changes holds that everything in the world is constantly developing, and expounds this "natural" law, which is "Tao". This law reveals the characteristics of the whole universe, including the attributes of everything in the world.

Baidu encyclopedia-Yijing