Huáigǎn 懷感 (d. 699?)
A late seventh-century Tang Buddhist monk and one of the Five Patriarchs of the Chinese Pure Land tradition (in the standard wǔ zǔ enumeration: Lúshān Huìyuǎn → 曇鸞 Tánluán → 道綽 Dàochuò → 善導 Shàndǎo → Huáigǎn → Shǎokāng → Yánshòu, etc.). Native of Cháng’ān 長安. He was originally trained in the Yúqié 瑜伽 / Faxiang 法相 (Dharma-character) school of 玄奘 Xuánzàng (602–664) and his disciple 窺基 Kuíjī (632–682), and was a noted scholar of the Yúqié shīdì lùn. According to the standard biography in Sòng gāosēng zhuàn 宋高僧傳 juǎn 6, Huáigǎn was sceptical of Pure Land devotion until he encountered Shàndǎo and engaged in an intensive niànfó retreat — after which he experienced a personal vision of Amitābha and was definitively converted to the Pure Land path.
His major work is the Shì jìng-tǔ qún-yí lùn 釋淨土群疑論 KR6p0039 (T47N1960), a substantial seven-juǎn doctrinal treatise that collects and answers the principal Yogācāra-school objections to Pure Land devotion. The text is one of the longest and most doctrinally sophisticated Tang Pure Land works and represents the Faxiang-school engagement with Pure Land doctrine — the application of vijñaptimātratā (consciousness-only) ontology to the question of the Pure Land’s metaphysical status. Modern scholarship (Mochizuki, Ueyama) treats Huáigǎn as the principal Tang Pure Land thinker engaging the Yogācāra tradition.
He died at Qiānfúsì 千福寺 in Cháng’ān, conventionally placed at 699. The Qúnyí lùn was completed by his disciple Huáiyùn 懷惲 — Huáigǎn died before finishing the manuscript, and the closing portions were edited and arranged by his pupil.
Sources: Sòng gāosēng zhuàn 宋高僧傳 vol. 6; Lèbāng wénlèi KR6p0048 vol. 3; Fó zǔ tǒng jì 佛祖統紀 vol. 28; Mochizuki, Chūgoku jōdo kyōrishi (1942/1964). DILA Authority id A001296.