Fā-hé-sī-bā 發合思巴 (also written 八思巴 / 帕思巴; Tibetan ʼPhags-pa Blo-gros-rgyal-mtshan, 1235–1280) was the great Tibetan Sa-skya hierarch and Imperial Preceptor (帝師) of Khubilai Khan, instrumental in the Mongol-Yuán court’s Buddhist policy and famous as the inventor of the ʼPhags-pa script — the imperial alphabet promulgated by Khubilai in 1269 to provide a unified writing system for Mongolian, Chinese, Tibetan, Sanskrit, and Uyghur within the Yuán empire. He was a nephew and chief disciple of Sa-skya Paṇḍita (Sa-skya paN-Di-ta Kun-dgaʼ-rgyal-mtshan, 1182–1251), whom he accompanied to the Mongol court in 1244; on Sa-skya Paṇḍita’s death in 1251 he succeeded as head of the Sa-skya school and as the religious authority over Tibet under Mongol patronage. In 1260 he was named Imperial Preceptor (國師) by Khubilai, then Imperial Preceptor (帝師) in 1270 with formal jurisdiction over Buddhist affairs across the empire.
The Zhāng suǒ-zhī lùn 彰所知論 KR6o0049 (T1645) was composed by ʼPhags-pa in Tibetan in 1278 for the heir-apparent Činggim 真金 (the Crown Prince, son of Khubilai), and translated into Chinese in the same year by Shā-luo-bā 沙囉巴 (Saraba, an Indian translator at the Yuán court). The work is a doctrinal compendium covering Buddhist cosmology, the path of the bodhisattva, and the major doctrines of vinaya, abhidharma, and Mahāyāna; it is the only Tibetan Buddhist śāstra canonised in the Chinese Tripiṭaka. ʼPhags-pa died in Sa-skya in 1280; his lineage continued as the Mongol-Yuán imperial school for nearly a century. The Chinese transcription 發合思巴 reflects an early Yuán convention; the more familiar 八思巴 is later.