Qīngzhuō Zhèngchéng 清拙正澄 (Xiánchún 10 / 1274 → Yányòu 5 / 1339-02-17), Yuán-dynasty Chinese Línjì-school Chan master, dispatched to Japan in Kareki 1 / 1326 at the invitation of the Kamakura Bakufu and subsequently a foundational figure in the Japanese Rinzai-Zen establishment. Posthumous Japanese title Dàjiàn Chánshī 大鑑禪師 (Jp. Daikan Zenji), bestowed by Emperor Go-En’yū 後圓融天皇 in Eitoku 1 / 1377 (Hongwu 10) — hence the title of his monastic rules. Native of Fúzhōu 福州 in Fujian.
Tonsured young in his home prefecture; received transmission from Yúwèng Rúhuái 愚菴如懷 of the Pò-an Zǔxiān 破菴祖先 / Mì-an Xiánjié 密菴咸傑 sub-line of the Yángqí school. Already eminent in southern China when in his early fifties he accepted the Bakufu’s invitation conveyed through the Kenmin envoy circuit. On arrival in Japan he served successively as abbot of:
- Kenchō-ji 建長寺 in Kamakura (the senior of the Five-Mountains),
- Engaku-ji 圓覺寺 in Kamakura,
- Jōchi-ji 淨智寺 in Kamakura,
- Nanzen-ji 南禪寺 in Kyoto, and
- Kenninji 建仁寺 in Kyoto.
At the invitation of Ogasawara Sadamune 小笠原貞宗 (1294–1350), military governor of Shinano, Seisetsu founded Kaizen-ji 開善寺 at Mount Ina-zan 伊那山 in Shinano (modern Iida-shi, Nagano), where he established a strict pure-rules curriculum. His Daikan shōshingi 大鑑小清規 (“Lesser Pure Rules of Daikan”), the present text KR6t0283, is the most influential set of monastic rules introduced from continental Chan into Japanese Rinzai-Zen alongside the Sòng Chānyuàn qīnggǔi and the Bǎizhàng qīnggǔi. The text became standard at Kenchō-ji and was widely adopted thereafter.
Seisetsu died at Kenchō-ji in Yányòu 5 (1339) aged 66 (or 65 by some accounts). His Japanese dharma-heir was Gōnen Mokushiki 鄂隱慧奯 and others; one principal sub-lineage descends to Tessō Sōmon 鐵叟宗門 and is institutionally embedded in the Kamakura Five-Mountain establishment. The famous “Ogasawara family ritual” 小笠原家禮 — the funeral protocol used by the Ogasawara house and many subsequent samurai families — derives from Seisetsu’s monastic rules and is regularly cited as the secular ritual residue of Yuán-Chan in Edo-period etiquette manuals.