The first is "the combination of articles and times, poetry and things." There are two meanings here: on the one hand, it reflects current events, that is, the preface to Qin Zhongyin says that "when Zhenyuan and Yuanhe are in harmony, they should be in Chang 'an, and those who are full of sorrow should tell their stories directly"; on the other hand, it is written for reality, that is, the so-called Nine Books with Yuanhe is "insufficient to make up for the time". What is reflected is not necessarily current events, but the purpose is for reality. Du Fu has written many works that face reality and satirize current affairs in his life, but he has not put forward his own views on current affairs. Bai Juyi inherited the realistic spirit of Han Yuefu and put forward the idea that "articles should be written in time, songs and poems should be written in time" from the social reality of the Middle Tang Dynasty, which is a great contribution to the theory of realistic poetry.
Bai Juyi's second valuable proposition is "only songs make people sick, I hope the emperor knows." Before Du Fu, the life and sufferings of working people were reflected in The Book of Songs and Han Yuefu. However, most of the literati's works are princes and nobles, bureaucratic hermits, and rarely write about the people. The life and sufferings of working people began to occupy a place in Du Fu's poems. Farmers, soldiers, boatmen, fishermen, women with negative wages and widows without grievances in Du Fu's works deeply sympathize with their sufferings and reveal the reasons for their poverty. However, Du Fu did not put forward the idea of reflecting people's sufferings, which was clearly put forward by Bai Juyi. There were examples of Du Fu's poems before, and Bai Juyi's thought after, which pointed out a new direction for later poets and opened up a new world for poetry creation. Many poets in later generations followed the path of Du Fu and Bai Juyi.
There is another small point. Since Bai Juyi writes for the people, he advocates that his articles should be easy to understand, so that everyone can understand his articles, even illiterate old ladies. Every time he writes an article, he will read it to illiterate people until they can understand it.