A 10th century master of the Chinese Zen (Chan) tradition, and one of the most influential teachers in its history, Yunmen Wenyan shows up in many famous koans, and is credited with the adage, "Every day is a good day." In this modern Zen classic, historian and Buddhist scholar Urs App introduces Yunmen and translates his teachings, elucidating the encompassing and penetrating nature of his talks and dialogues. App also includes a brief history of Chinese Zen, a biography of the master, and a wealth of resource materials.