Athanasius of Alexandria (circa 298 373) is also given the titles St. Athanasius the Great, Pope St. Athanasius I of Alexandria, St Athanasius the Confessor and (in the Coptic Orthodox Church, mainly) St Athanasius the Apostolic. He was the 20th bishop of Alexandria, but he was often in exile, which was ordered by several different emperors. He is best known for being a Christian theologian and an Early Church Father, including a leading role against the Arians in the First Council of Nicaea. At the time, he was a deacon and personal secretary of the 19th Bishop of Alexandria, Alexander. Nicaea was convoked by the Emperor Constantine in May–August 325 to address the Arian heresy that Christ is of a distinct substance from the Father. His writings were well regarded by all Church fathers who followed, in both the West and the East. His writings show a rich devotion to the Word-become-man, great pastoral concern, and profound interest in monasticism. Among his writings was On the Incarnation, his earliest work, believed to have been written around 320. In it, he invokes Plato and used a definition from the Organon of Aristotle. He was also familiar with the theories of various philosophical schools, and in particular with the developments of Neo-Platonism. In this, St. Athanasius defends the incarnation of Christ and explains why God chose to take human form. Athanasius heavily cites Scripture as well as Early Church teachings, while also attempting to defend against objections to his account, some of which still persist today.