During the Qin Shihuang period, most Confucian classics were burned or banned from spreading. Dr Fu Sheng hid the Book of History in the wall. After the Qin and Han wars, most of them were lost, leaving only 29 articles. On this basis, Fu Sheng taught Shangshu for life. When he was in his nineties, Wendi sent Chao Cuo to his home to study. At this time, Fu Sheng lisped, and his daughter finished the teaching by relay. Although the differences in dialects spoken by the two sides led to some misunderstandings in Chao Cuo, the basic content was still spread. "Do your best to spread" depends on the immortal fire. Chinese civilization can last forever and flourish, relying on the passing of generations.
The development of printing ensures the circulation of books to a great extent, but man-made destruction will destroy some books from now on, and often there is no successor to a subject. Moreover, for rigorous scholars, there will always be some research results or a specific result that cannot be compiled in words, or it has not been published for various reasons and can only be passed on by word of mouth.