GREGORY OF SINAI (d. 1347) was an ascetic and mystic canonized by the Eastern Orthodox church. The Greek church commemorates his life on February 11 and the Slavic churches on August 8. Much of the life and writings of this great church father is known from the life composed by his disciple Kallistos I, patriarch of Constantinople.

Born in Asia Minor, Gregory took his monastic vows on Mount Sinai. After travels to Cyprus and Crete he came to Mount Athos. Disturbed to find the holy men of Athos in ignorance of true silence and contemplation, he undertook to instruct both monks and solitaries in the contemplative art. Further travels took him to Constantinople and to Thrace, where he founded monasteries and taught the techniques of mental prayer.

Gregory did not write extensively. Most of his works are concerned with mental prayer and hesychasm, the spiritual life of...