The Mumonkan shō 無門関抄 kept in the Tanimura Collection in Kyoto University is the lecture report on the Wumen guan 無門関 by the Sōtō sect monk named Ten’ei Shōtei 天英祥貞, active in the Muromachi period. It is the oldest lecture report on the text in existence. By studying the Mumonkan shō, we can investigate the thought of Ten’ei Shōtei and the actual situation of practicing Wumen guan in the medival Sōtō sect. The Wumen guan was extensively studied by monks, and the theories of schools interacted with each other. As a result, I conclude that the importance of Kōan Zen 公案禅 increased in the Sōtō sect.
