It should be said that anyone who knows a little about China's traditional culture will know the Four Books. It is the general name of The Analects of Confucius, Mencius, Daxue and The Doctrine of the Mean. Among them, The Analects of Confucius and Mencius are collections of speeches by Confucius, Mencius and their students respectively, while Daxue and The Doctrine of the Mean are two books in The Book of Rites. Zhu, a famous scholar in the Southern Song Dynasty, first linked the two. However, before Zhu, Cheng Hao and Cheng Yi strongly advocated these books. They believe that "University" is an important book of Confucius' "the door for beginners to enter Germany" and was compiled by Confucius' students. The Doctrine of the Mean is a book "Confucius teaches the mind", and it is a pen, which is written by Confucius' grandson Zisi. Together with The Analects of Confucius and Mencius, these two books express the basic ideology of Confucianism and are the most important documents for studying and treating Confucianism. It is from this perspective that Zhu compiled four books: The Analects of Confucius, Mencius, University and The Doctrine of the Mean. Because they came from four representatives of early Confucianism, namely, Confucius, Zeng Shen, Zi Si and Mencius, they were called "Four Books" for short. Zhu annotated the four books respectively. Among them, the annotations of Daxue and the Doctrine of the Mean are called "chapters and sentences", and the annotations of The Analects and Mencius are called "concentrated notes" because they quote many other people's sayings. It is worth noting that the order of Zhu's four books was originally The University, The Analects of Confucius, Mencius and The Doctrine of the Mean, which was arranged in the order of learning from the shallow to the deep. Later generations put The Doctrine of the Mean before The Analects of Confucius because the length of Daxue and The Doctrine of the Mean was short. In order to facilitate printing and publishing, it became the order of Daxue, The Doctrine of the Mean, The Analects of Confucius and Mencius.