Throughout the development of the Early Church, false and heretical teachings began to form within the church. In response, church councils were organized and held in order to address and debate theological topics or church functioning topics, and from these councils, creeds were formed, which became another standard for orthodox doctrine. The Early Church councils of Nicea (C.E. 325), Constantinople (C.E. 381), and Chalcedon (C.E. 451) played major roles in combating heresies.
The Council of Nicea
One of the theological controversies of the 4th century was focused on the Son. A teacher in Alexandria, named Arius, argued that the Son was not God but was created by God as the first of His creations. From this perspective, the Son was not coeternal with the Father, and so Arius’ motto was “once the Son was not” indicating that the Son was a creature or lesser being than God. Arius explained that in order to keep the monotheistic view of God intact, the divinity of the Son had to be rejected. He believed in the pre-existence of the Son before the incarnation but emphatically argued that at some point before the incarnation, the Son was created. According to Arius, the created Son through the incarnation paved the way for salvation by being obedient, even unto death, to his creator.
The bishop of Alexandria, named Alexander, clashed with the views of Arius by arguing that the Son was divine and coeternal with God-the Father. Therefore, the Son was not created before the incarnation, but rather God-the Son became incarnate in Jesus. Alexander believed that Jesus was the God-Man and argued that the earliest Christians worshipped Jesus as God and not as a created being. Alexander argued that God-the Son achieved the salvation of humans by entering into human history through the incarnation.
As a bishop, Alexander condemned Arius’ teachings and removed Arius from church leadership in Alexandria. Arius and others protested the decision which caused unrest in the Eastern church. With the threat of a split of the Eastern church, Imperial Constantine got involved and ordered the arrangement of the Council of Nicea (C.E. 325). Approximately three hundred bishops attended the Council of Nicea where the primary debate centered on two Greek words: ὁμοούσιος (homoousios) and ὁμοιούσιος (homoiousios). Those who followed Alexander described the Son in relation with the Father by using the term ὁμοούσιος (homoousios), meaning of the same substance with the Father. Those who followed Arius described the Son in relation with the Father by using the term ὁμοιούσιος (homoiousios), meaning of similar substance with the Father.
The Council of Nicea determined that the Son was ὁμοούσιος (homoousios) “of the same substance” with the Father. Thus, the council was in favor of Alexander’s views of the Son being consubstantial, coeternal and coequal with the Father. The council declared the divinity of the Son and condemned Arius’ views. From the Council of Nicea, the Nicene Creed was formed and was the foundational creed for the church and for other church councils.
 M. Ovey, “Nicea, Council of” in New Dictionary of Theology: Historical and Systematic (NDT) eds. Martin Davie et al. (Downers Grove, Ill: IVP Academic,2016), EPUB edition.  Justo L.González, The Story of Christianity, Rev. and Updated, 2nd ed. (New York: HarperOne, 2010), EPUB edition, pt.2, ch. 1, “The Outbreak of the Controversy.”  González, The Story, EPUB edition, pt.2, ch. 1, “The Outbreak of the Controversy.”  González, The Story, EPUB edition, pt.2, ch. 1, “The Outbreak of the Controversy.”  Robert C. Walton, Chronological and Background Charts of Church History, Revised and Expanded ed. (Grand Rapids, MI: Zondervan, 2005), Chart 28.