Adoptionism: Jesus was a creation of God became a son of God at his baptism. They understood the concept of the son of God in a very metaphysical way.

Jesus became a son of God at his baptism

Adoptionism was a Christian belief that Jesus was born of Joseph and Mary in the normal way. Jesus was adopted as God’s son at his baptism. By Jewish-Christian accounts, Jesus was chosen because of his sinless devotion to the will of God. Early Jewish Christians understood Jesus as the Messiah and the Son of God in terms of the anointing at his baptism which some see as in line with the radical monotheism of first century Judaism. The Jewish-Christian Gospels make no mention of a supernatural birth. Rather, they detail his experience in the River Jordan. ***

Adoptionism was declared heresy at the end of the second century, and was rejected by the First Council of Nicaea, which wrote the orthodox doctrine of the Trinity and identifies Jesus as eternally begotten of God. ***

Arianism is the theological teaching of Arius (ca. AD 250–336), a Christian presbyter from Alexandria, Egypt, concerning the relationship of the entities of the Trinity (‘God the Father’, ‘God the Son’ and ‘God the Holy Spirit’) and the precise nature of the Son of God. Deemed a heretic by the First Council of Nicaea of 325, Arius was later exonerated in 335 at the First Synod of Tyre,* and then pronounced a heretic again after his death at the First Council of Constantinople of 381.[2] The Roman Emperors Constantius II (337–361) and Valens (364–378) were Arians or Semi-Arians. The Arian concept of Christ is that the Son of God did not always exist, but was created by—and is therefore distinct from and inferior to—God the Father. **

Why Jesus could not be of the same substance as God

Arianism lasted well into the 7th century and was the majority element in

Arius - Born: 256 AD, Died: 336 AD, at 80 years of age.

the 4th century. Arius taught that God is absolutely unique and incomprehensible, is alone self-existent, unchangeable and infinite and must be understood in terms of his absolute oneness. *

The life of Jesus as portrayed in the canonical gospels demonstrates that Jesus was not self-existant, that he changed and grew over time, if in no other way than just passing through the stages of birth, childhood, adolecence and adulthood and that he was finite, having a definite time of conception and birth. *

Therefore Jesus was God’s created being who was called into exitence out of nothingness, who could not have shared in the absolute uniqueness, immutability and infinity of God without compromising them, who could not have been the same substance as God without compromising the oneness of God and who would have had no knowledge of God other that that which God chose to reveal to him. *

* Dr Jerald F. Dirks — Harvard Divinity School / Doctor of Psychology

** Wikipedia — Arianism

*** Wikipedia — Adoptionism