MUSŌ SŌSEKI (1275–1351), a monk of the Rinzai school of Zen Buddhism in medieval Japan. Born into an aristocratic family, he entered the religious life at an early age, rose to become head of some of Japan's most influential Zen monasteries, and left his stamp on Rinzai Zen and medieval culture.

Musō's earliest Buddhist training was not in Zen, but in esoteric Tendai and Shingon Buddhism. He was drawn to Zen at about the age of twenty and went to study under the Chinese Zen master Yishan Yining at the monastery of Engakuji in Kamakura. Although an able pupil, Musō was unable to convince Yishan that he had attained a valid enlightenment experience. Finally, he left Engakuji to seek his understanding of the buddha-nature in a life of solitary wandering and meditation, and to test...