Kōsai

Kōsai (幸西, 1163 – May 20, 1247) or Kōsai Jōgakubō, was a former monk of the Tendai Buddhist sect and disciple of Hōnen's Pure Land Buddhist lineage. Kōsai, along with another monk called Gyōkū, were famous as advocates of the ichinen-gi (一念義, "Single thought doctrine" or “the doctrine of a single nenbutsu”) which proved to be quite popular as well as controversial. Kōsai was eventually exiled to Shikoku during a period of persecution of Hōnen's lineage by the Japanese government.

Kōsai's teaching emphasizes a single faithful moment in which a single recitation of Amitābha's name (nembutsu), would cause a transformative religious experience that was itself sufficient to attain birth in the Pure Land. His teaching emphasizes true faith over practice. This doctrine of "single nembutsu" (ichinen) drew criticism from established Buddhist sects at the time, and even Hōnen's other disciples like Benchō. Kōsai's teaching may have also influenced Shinran (1173–1262), the founder of Jōdo Shinshū, who also emphasizes the primacy of true faith (shinjin) and whose teaching is similar to Kōsai's.