The Nichiren doctrinal term jigu sanzen 事具三千 is used to represent the truth taught in the honmon 本門 (second half) of the Lotus Sūtra, and is a term sourced in the Tendai debate concerning jikkai gogu 十界互具 (mutual possession of the Ten Worlds). The debate concerns whether the buddha inherent in ordinary beings is a principle (ri 理) or is actual (ji 事).
This question was first brought up by Annen 安然 (841?–915?), and in Tendai the term jigu jikkai 事具十界 came to be used, meaning that buddha is inherent in ordinary beings in an actual sense. In the Muromachi period, Chōjun 貞舜 (1334–1422) developed this thought into the term jigu sanzen in his Shūyō kashiwabara anryū 宗要柏原案立.
Nichiryū 日隆 (1385–1464), who lived in the same period as Chōjun, was the first to use jigu sanzen as a Nichiren doctrinal term. Nichiryū used and explained this term in his Kaishaku kenpon shūyōshū 開迹顕本宗要集 in the same way as Chōjun did in the Shūyō kashiwabara anryū. Nichiryū adapted the Tendai term jigu sanzen to more accurately express Nichiren’s teachings.
