This sentence expresses that there is no more effective way to adjust the relationship between husband and wife, to urge people to respect their elders, to make interpersonal relationships mellow, to educate people to become virtuous, and to change customs over time. Preface to Poetry is also called Preface to Mao Poetry. After the pre-Qin classics were burned by Qin fire, there were few left, and the Book of Songs was passed down from mouth to mouth. There were four schools of poetry in the early Han Dynasty, namely Lu School, Qi Zhiguan Gu School, Yan School and Lu Maoheng School. They are called Lu Poetry, Qi Poetry, Han Poetry and Mao Poetry respectively. The "Three Poems" of Lu, Qi and Han have been lost today, and the solo poems have been passed down from generation to generation.
The preface expounds the characteristics, content, classification, expression and social function of poetry, which can be called a systematic summary of Confucian poetics in pre-Qin period.