This is the theory of poetry creation put forward by Bai Juyi. He said in "Nine Books with the Same Yuan": "Since I came to North Korea, I have become older and more knowledgeable. Every time you talk to people, ask more current events, read more history and seek more truth. I just know that articles are written in time and songs and poems are written for things. "
"When writing articles, songs and poems are written in things" has two meanings: on the one hand, it reflects current events, that is, in the Preface to Qin Zhongyin, it is said that "when Zhenyuan and Yuanhe are in harmony, they will be given to Chang 'an, and those who are full of sorrow will tell their stories directly. "On the other hand, it is written for reality, which is the so-called" stoppage time "in the nine books of Yuan Zaju. 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.