Athanasius was bishop of Alexandria from 328 until his death (337). His fight for the right faith, his writings and his ability to win the pope of Rome for his aims and to integrate monkhood into the church made him the most important figure in the 4th century church.
With his letters to Serapion, bishop of the Egyptian city of Thmuis, he initiated a new phase in the formulation of the faith by introducing into theology the question of the deity of the Holy Spirit with regard to the Nicene Creed (creed of the first ecumenical council in Nicaea).