An influential Japanese Rinzai zen monk of the Kamakura period. He came from a minor aristocratic family in Ise, and entered the monastic order at a young age, at first joining the esoteric Shingon school but later transferring his allegiance to Rinzai Zen after the painful, lingering death of his Shingon master left him shaken, and after two famous Chinese Ch'an masters appeared to him in a dream during a period of solitary practice. From that point, even as he looked for a teacher to guide him, Musō practised Zen in several places, and eventually reached enlightenment (satori) on his own in 1305, although the experience was confirmed and authenticated by Kōhō Kennichi (1241–1316), which technically made him the latter's disciple. After that, he found himself called by a succession of seven emperors to engage in a project or to take charge of a large temple, despite his own wish to retire from the world and live quietly in the country. For the first twenty years after his enlightenment, he lived in a succession of small hermitages, most of which he himself founded, but after a time was forced to move on because so many clergy and laity were attracted to his teachings that the hermitages grew into temples through his own charisma. Finally, in 1325, the Emperor Go-Daigo called him to take over one of the major temples of Kyoto.the Nanzen-ji. Leaving this post after only one year, he spent time in Ise where he built the Zennō-ji, and then in Kamakura in the Jōchi-ji. In 1329 he was called to the Engakuji.a once-prominent temple that had fallen to corruption and decay. After a year reforming this temple, he moved on again. The remainder of his life conformed to this pattern: official appointment to a large temple followed by retreat to smaller temples away from the centres of power. Some authorities credit him with a keen eye for the political instabilities of the time and his ability to know when to draw near to the court or the shōgun and when to withdraw.
Musō's style mixed academic learning (carried forward from his early years in the Shingon school) and the kōan method of the Rinzai school. While officially, Zen has represented itself as a ‘special teaching outside of the scriptures’ that ‘does not rely on words and letters’, Musō saw no contradiction: he once said when questioned on this, ‘to explain the sūtras is to speak of Zen’. For him, the point of all practice and learning was to direct the student to a realization of reality as it is; if kōan practice can accomplish this, then one makes use of the kōan; if doctrinal study proves effective, then one instructs the student in doctrine. Biased clinging to one method and rejection of the other only betray the master's own lack of enlightenment and insight. Musō's involvement in so many different temples, particularly those that had fallen into corruption and needed reform, led him to compose books of monastic rules (particularly the shingi or ‘Pure Rules’ variety, which sets forth the ‘house rules’ for a Zen temple) as well as admonitions for strict practice. He was also well known for his artistic accomplishments. He is credited with the establishment of a ‘Musō line’ of Rinzai Zen, which has sustained itself to the present day.