This study examines the introduction of the Three Natures theory, using the Qunyi lun 群疑論 of the Tang monk Huaigun 懐感 as an example. Before Huaigun, Pure Land Buddhism held an orthopraxis according to the Two Truths theory. However, in addition to the Two Truths theory, the Three Natures theory is also explained in the Qunyi lun. This study explores the development of the argument, and as a result points out two things. First, the historical necessity of the “acceptance of the new translation texts,” that is, those tied to Xuanzang and his workshop. Second, the shift in Chinese Pure Land-centric debates leading to more detailed consideration of “awareness of Buddha body and Buddhist land.”