Monasticism and the spiritual life of monks has always been an essential element in Orthodoxy. In the fourth century, Cappadocia became the centre for the concept of the monastery, which in time spread throughout Europe, initiated by the Cappadocian Fathers, Saint Basil the Great (c.329-379), Saint Gregory of Nazianzus and Saint Gregory of Nyssa. Saint Basil the Great defended the doctrine of the established religion against heretics. He held that the way to render perfect service to God was through asceticism. He developed the system of rules for the Orthodox monastery after visiting the monasterial establishments in Egypt and Syria. He rejected the introverted isolation and concept of suffering of the monks who tortured their own flesh. He established organized communities which encouraged the principles of cooperation and of individual independent worship. The monastic system he developed was influential on the whole Christian world for centuries. The day of his death is a commemorative day in both Orthodox and Catholic-Churches.