The Arian ControversyArius denied the divinity of Christ. If Jesus was born, then there was time when He did not exist. If He became God, then there was time when He was not. The Council declared Arius' teaching a heresy, unacceptable to the Church and decreed that Christ is God. He is of the same essence "homoousios" with God the Father.
The first part of the seven articles of the Creed were ratified at the First Ecumenical Council. The text reads as follows:
"We believe in one God. The Father Almighty. Maker of heaven and earth, and of all things visible and invisible. And in one Lord Jesus Christ, the Son of God, the only begotten, begotten of the Father before all ages. Light of Light; true God of true God; begotten not made; of one essence with the Father, by whom all things were made; who for us men and for our salvation came down from heaven, and was incarnate of the Holy Spirit and the Virgin Mary, and became man. And He was crucified for us under Pontius Pilate, and suffered, and was buried. And the third day He rose again according to the Scriptures; and ascended into heaven, and sits at the right hand of the Father; and he shall come again with glory to judge the living and the dead; whose Kingdom shall have no end."
Defenders of Orthodoxy
St. Athanasios the Great (297-373)
Fearless champion of Orthodoxy; spent sixteen of his forty-five years as Bishop of Alexandria in exile; one of the most profound theologians; Father of the Church.
St. Basil the Great (330-379)
A natural leader and organizer; spoke and wrote against Arianism; Founded hospitals, orphanages, welfare agencies; revised and updated the Divine Liturgy; made a great contribution to Monasticism (East and West); one of the famous Cappadocian Fathers (together with St. Gregory of Nyssa; his younger brother and St. Gregory of Nazianzus the Theologian; his close friend). The Cappadocians, along with St. Athanasius the Great, laid the pattern for formulating the doctrines related to the mystery of the Holy Trinity. St. Basil the Great, along with St. Gregory of Nazianzus (the Theologian) and St. John Chrysostom are called the Three Hieararchs.
Read about the other Ecumenical Councils: