A much revered theologian, bishop of Alexandria, and leader of the 4th century, Athanasius was famous for his defense of the deity of Christ against Arius and his followers at the First Council of Nicea. His works, such as “Apology Against the Arians” and “The Incarnation of the Word of God”, were pivotal in the development of later doctrines on the Trinity and are some of the first documents to show a developed orthodox theology. He served at the First Council of Nicaea.