St Symeon the New Theologian was abbot of the monastery of St Mamas in Constantinople at the turn of the eleventh century. He was also perhaps the most remarkable and certainly the most forceful advocate of the mystical experience of God in the history of the Byzantine Church. Though they were on occasion suppressed by ecclesiastical authorities wary of his fierce enthusiasm, as well as of his claims to charismatic authority, St Symeon's writings survived in the Orthodox Church and continued to play a vital role in the several renewals of spiritual life and prayer which has sustained the Church in its often difficult history over the past millennium.