Hesychasm is a type of experiential prayer used primarily in the Eastern Orthodox Church. The prayer involves a series of breathing techniques and body posture – sort of like yoga and Buddhist monks do. The priest says the Jesus Prayer over and over (“Lord Jesus Christ, son of God, have mercy on me a sinner”). The idea that this type of praying should be used in church was put forth by St. Gregory Palamas who said the practice helped to see the light of God. On June 10, 1341, a church council in Constantinople approved the method.
