After apostolic times, some Christian thinkers began to ask themselves: How was the Son related to the Father?"

In 312 AD, Alexander became Bishop of Alexandria and during one of his sermons explained the mystery of the Trinity in which he affirmed that the Son was equal to the Father, that is, of the same divine nature as the Father.

Arius, one of his priests in Alexandria, did not agree and began to preach and teach that the Son was the first-born of the Father, meaning created by the Father. "Arius denied the full deity of the preexistent Son of God who became incarnate in Jesus Christ. He held that the Son, while divine and like God ('of like substance'), was created by God as the agent through whom he created the universe. Arius said of the Son, 'there was a time when he was not.'" (Webpage: Arianism) Arius further asserted that the Son being a creature had no direct knowledge of the Father. Bishop Alexander in his deposition pointed out that this contradicts Christ who claimed "Just as the Father knows me and I know the Father" (Jn 10:15) And how would Arius have explained the following, "'My Father is at work until now, so, I am at work.' For this reason they tried all the more to kill him, because he not only broke the sabbath but he also called God his own father, making himself equal to God." (Jn 5:17-18)

The Arian controversy was upsetting the Christians of the Roman Empire so Emperor Constantine convened the Council of Nicea in 325 AD. Three hundred and twenty eight bishops participated. "The Council interrogated Arius using Scripture, only to find that he had a new way of interpreting every verse they brought before him. Finally, they used the argument that Arius' view had to be wrong because it was new." (Webpage: The Council of Nicea)

Athanasius was a deacon, a theological expert and appointed secretary to Bishop Alexander of Egypt. He refuted with zeal the Arian Heresy. In essence he said that only God by becoming man could have redeemed mankind from the corruption of sin and restore him to eternal life. If Christ, then, was not true God as the Arians claimed, redemption from sin could not have occurred. Athanasius than lead the council in formulating the Creed (Nicean Creed) by which we now express our belief in the Eternal Sonship of Christ every Sunday at Mass --

"We believe in one Lord, Jesus Christ,
the only Son of God,
eternally begotten of the Father,
God from God, Light from Light,
true God from true God,
begotten, not made,
of one Being with the Father."

Theotokos