In 8 13 AD (the eighth year of Yuanhe in Tang Xianzong), Yuan Zhen took the opportunity to write an inscription for Du Fu's grave, expounded the realistic tradition in the history of China literature in detail, and published his insights. Yuan Zhen especially praised the "style" and "elegance" in The Book of Songs, which reflected the fighting tradition of realistic interference in politics. Yuan Zhen believes that Jian 'an literature has made progress in reflecting reality than Han Dynasty. During the Song and Qi Dynasties, poets categorically denied Liang and Chen's poems, such as "chanting the spirit, lingering in the scenery", "coquettish carving, clever sketches" and so on. The poet went on to point out that the early Tang Dynasty inherited the poetic style of Qi-Liang formalism, and poetry has not yet become a tool to reflect social reality and shout for people's livelihood. In this case, Yuan Zhen believes that only by restoring the cultural tradition of The Book of Songs and Han Yuefu, especially Du Fu's realistic tradition, can the style of poetry be saved and poetry be advanced along the correct road of reflecting reality and interfering in politics. Since Yuan Zhen rebelled against the prosperous Tang Dynasty and neglected Du Fu's social thoughts for a long time, he was the first to stand up bravely and made an unprecedented high evaluation of Du Fu and his realistic tradition. Yuan Zhen's high evaluation of Du Fu was accepted by historians. The Biography of Old Tang Fu quoted Yuan Zhen's praise of Du Fu and said:
"In the last years of Tianbao, poets were just like Li Bai, vain and conceited, contemptuous and dirty, and there was a scorn for Daoshan. Yuan He, a poet, commented on Du Li's merits and demerits ... Since then, scholars have taken the theory of Ci as positive. "
It was in the atmosphere of the times that Yuan Zhen compared Du Fu's poems with Li's, thus gaining a unique understanding.
In the middle Tang Dynasty, when eunuchs were autocratic, the country was declining and the people were poor, Yuan Zhen's full affirmation of the realistic tradition of Du Fu's poems was undoubtedly correct and a pioneering work. For thousands of years, China ancient poetry writers took Du Fu as their own creation model, and quite a few China classical poetry researchers also took Du Fu's poems as their research objects, and Yuan Zhen was the first person to give high praise to Du Fu and Du Fu's poems. Du Fu's poems have gone abroad to the world today. Just as people in China know Shakespeare, Tolstoy and Tagore, people in many countries in the world also know Du Fu and Qu Yuan in China and are familiar with their poems. Yuan Zhen was the first person who spoke highly of Du Fu and Du Fu's poems. It should also be pointed out that the Epitaph of Yuan Wailang Du Jun written by the Ministry of Industry in the Tang Dynasty (preface to parallel prose) played an important role in Bai Juyi's writing of Yu Jiu Shu [2], which is an important literary theoretical document in the history of China literature.
Of course, Yuan Zhen changed his view of "the great enemy of Du Li's poems" in his early years, and instead thought that Li Bai could not learn from Du Fu's "Fan Han", which was an excessive preference for Du Fu, and it was indeed inappropriate and one-sided. This inappropriate preference is closely related to the poet's world outlook and his literary theory. Many works in Du Fu's poems are realistic about life and satirical about society. However, Li Bai's works are rarely outspoken about life, but they often express their thoughts in a romantic style, thus reflecting the darkness of society and personal misfortune in a tortuous way. This is the difference between them, but it is unfair to favor one over the other. It is not appropriate to promote Li and suppress Du, and it is not appropriate to promote Du and suppress Li. But this is the difference of ancient people's understanding and preferences, and we can't force the ancients. As far as Yuan Zhen and Du Fu are concerned, Du Fu just can't help telling the truth that he doesn't have many literary opinions. Yuan Zhen not only tells the truth, but also puts forward their reasons for telling the truth, that is, their literary opinions. This is also the difference between the two, and the latter is undoubtedly a step further than the former.