The answer is: the three major poetic propositions in the Song Dynasty are: quip theory, kung fu poetry theory and different materials and different tastes theory.
In Song Dynasty, Yan Yu thought that Li Bai and Du Fu's poems had their own beauty. The artistic features of Li Bai's poems are elegant, while those of Du Fu's poems are gloomy. Li Bai's poems are natural, while Du Fu's poems have rules to follow.
"Beyond Kung Fu Poetry" says: It is a poem written by Lu You, and it is also written by Zhang Xu, which means that what is intended to be pursued can or even must be obtained by other means.
The theory of "different materials and different interests", referred to as "interest theory", comes from Yan Yu's Cang Shi Lang dialect in the Song Dynasty: "Poetry has different materials and has nothing to do with poetry; Poetry has other interests and has nothing to do with reason. ..... The poets in the prosperous Tang Dynasty are only interested in it, and there is no trace to be found. "
I hope you are satisfied, please adopt it, thank you!