The Gateless Gate is a collection of 48 Chan (Zen) koans compiled in the early 13th century by the Chinese Zen master Wumen Huikai. Wumen's preface indicates that the volume was published in 1228. Each koan is accompanied by a commentary and verse by Wumen. The common theme of the koans of the Wumen Guan and of Wumen's comments is the inquiry and introspection of dualistic conceptualization. Each koan epitomizes one or more of the polarities of consciousness that act like an obstacle or wall to the insight. The student is challenged to transcend the polarity that the koan represents and demonstrate or show that transcendence to the Zen teacher.