What was Xuanzang’s historical viewpoint on the history of sectarian Buddhism?
He learned the Sarvāstivādin Abhidharma for two years in Kashmir. When he returned to China, he translated the Yibu zonglun lun (Cycle of the Formation of the Schismatic Doctrines) written by a Sarvāstivādin of Kashmir. From these facts, it seems that Xuanzang was influenced by, and cultivated his historical viewpoint according to, the Sarvāstivādins of Kashmir.
But this investigation has made clear that some records contained in the Datang xiyu ji by Xuanzang are inconsistent with the Buddhist history related in the Yibu zonglun lun. Those records in the Datang xiyu ji are based on the Dīpavaṃsa produced from the southern Theravāda, and the Shelifu wen jing composed by the Mahāsāṃghika. Therefore, it should not necessarily be concluded that Xuangzang’s historical viewpoint was entirely informed by the Sarvāstivādins of Kashmir.
The reason for this is as follows: (1) At the time when Xuanzang visited India, the opposition to the Sarvāstivādins and the other sects was moderated to some extent. (2) As a Chinese Mahāyāna Buddhist, Xuanzang was in a position to view sectarian Buddhism in India with some critical distance. (3) He studied the teachings of several sects in India with a positive attitude and a strong desire to learn.