 As a young Buddhist scholar monk, Vasubandhu is said to have traveled from his home in Gandhāra to Kashmir, then the heartland of the Vaibhāṣika philosophical system, to study. There, students were sworn to keep the tradition secret amongst themselves. Vasubandhu questioned Vaibhāṣika orthodoxy and made enemies there, but managed to return home an expert in the system. Immediately, he violated Kashmiri Vaibhāṣika norms by giving public teachings, going so far as to dare all comers to debate him at the end of each day. Vasubandhu’s Kashmiri colleagues were livid until they received a copy of the text from which he was teaching, the root verses of his Treasury of the Abhidharma. This brilliant summary of their system pleased them immensely. But then, Vasubandhu published his auto-commentary, which criticized the system in various ways, primarily from a Sautrāntika perspective. Livid again. Years later, Vasubandhu’s Vaibhāṣika contemporary Saṅghabhadra composed two treatises purporting to refute the Commentary, and traveled to Ayodhyā, where Vasubandhu was living under royal patronage, to challenge the master to a public debate (Vasubandhu refused). This narrative, reported in Chinese and Tibetan sources, accounts for the unusual fact that Vasubandhu’s Commentary often disagrees with positions affirmed in the Treasury’s root verses.