On August 25, 325, the First Council of Nicaea ended with adoption of the Nicene Creed establishing the doctrine of the Holy Trinity. An excerpt from the article:
"The Arian controversy (not to be confused with the Indo-Europeans known as Aryans) was a discourse that occurred in the Christian church of the 4th century CE, that threatened to upend the meaning of the church itself.
The Christian church, like the Judaic church before it, was committed to monotheism: all the Abrahamic religions say there is only one God. Arius (256–336 CE), a fairly obscure scholar and presbyter at Alexandria and originally from Libya, is said to have argued that the incarnation of Jesus Christ threatened that monotheistic status of the Christian church, because he was not of the same substance as God, instead a creature made by God and so capable of vice. The Council of Nicea was called, in part, to resolve this issue.
The Council of Nicea
The first council of Nicea (Nicaea) was the first ecumenical council of the Christian church, and it lasted between May and August, 325 CE. It was held in Nicea, Bithynia (in Anatolia, modern Turkey), and a total of 318 bishops attended, according to the records of the bishop at Nicea, Athanasius (bishop from 328–273). The number 318 is a symbolic number for the Abrahamic religions: basically, there would be one participant at Nicea to represent each of the members of the Biblical Abraham's household. The Nicean council had three goals:
1) to resolve the Melitian controversy—which was over the readmission to the Church of lapsed Christians,
2) to establish how to calculate the date of Easter each year, and
t3) o settle matters stirred up by Arius, the presbyter at Alexandria.
Athanasius (296–373 CE) was an important fourth-century Christian theologian and one of the eight great Doctors of the Church. He was also the major, albeit polemical and biased, contemporary source we have on the beliefs of Arius and his followers. Athanasius' interpretation was followed by the later Church historians Socrates, Sozomen, and Theodoret.
Church Councils
When Christianity took hold in the Roman Empire, the doctrine had yet to be fixed. A council is an assembly of theologians and church dignitaries called together to discuss the doctrine of the church. There have been 21 councils of what became the Catholic Church—17 of them occurred before 1453).
The problems of interpretation (part of the doctrinal issues), emerged when theologians tried to rationally explain the simultaneously divine and human aspects of Christ. This was especially difficult to do without resorting to pagan concepts, in particular having more than one divine being.
Once the councils had determined such aspects of doctrine and heresy, as they did in the early councils, they moved on to church hierarchy and behavior. The Arians were not opponents of the orthodox position because orthodoxy had yet to be defined.
Opposing Images of God
At heart, the controversy in front of the church was how to fit Christ into the religion as a divine figure without disrupting the notion of monotheism. In the 4th century, there were several possible ideas that would account for that.
The Sabellians (after the Libyan Sabellius) taught that there was a single entity, the prosōpon, made up of God the Father and Christ the Son.
The Trinitarian Church fathers, Bishop Alexander of Alexandria and his deacon, Athanasius, believed there were three persons in one god (Father, Son, Holy Spirit).
The Monarchianists believed in only one indivisible being. These included Arius, who was presbyter in Alexandria under the Trinitarian bishop, and Eusebius, Bishop of Nicomedia (the man who coined the term "oecumenical council" and who had estimated participation at a substantially lower and more realistic attendance of 250 bishops).
When Alexander accused Arius of denying the second and third person of the Godhead, Arius accused Alexander of Sabellian tendencies.
Homo Ousion vs. Homoi Ousion
The sticking point at the Nicene Council was a concept found nowhere in the Bible: homoousion. According to the concept of homo + ousion, Christ the Son was consubstantial—the word is the Roman translation from the Greek, and it means that there was no difference between the Father and the Son.
Arius and Eusebius disagreed. Arius thought the Father, Son, and Holy Spirit were materially separate from each other, and that the Father created the Son as a separate entity: the argument hinged on the birth of Christ to a human mother.
Here is a passage from a letter Arian wrote to Eusebius:
" (4.) We are not able to listen to these kinds of impieties, even if the heretics threaten us with ten thousand deaths. But what do we say and think and what have we previously taught and do we presently teach? — that the Son is not unbegotten, nor a part of an unbegotten entity in any way, nor from anything in existence, but that he is subsisting in will and intention before time and before the ages, full God, the only-begotten, unchangeable. (5.) Before he was begotten, or created, or defined, or established, he did not exist. For he was not unbegotten. But we are persecuted because we have said the Son has a beginning but God has no beginning. We are persecuted because of that and for saying he came from non-being. But we said this since he is not a portion of God nor of anything in existence. That is why we are persecuted; you know the rest."
Arius and his followers, the Arians, believed if the Son were equal to the Father, there would be more than one God: but Christianity had to be a monotheistic religion, and Athanasius believed that by insisting Christ was a separate entity, Arius was taking the church into mythology or worse, polytheism.
Further, opposing Trinitarians believed that making Christ a subordinate to God diminished the importance of the Son.
Wavering Decision of Constantine
At the Nicean council, the Trinitarian bishops prevailed, and the Trinity was established as the core of the Christian church. Emperor Constantine (280–337 CE), who may or may not have been a Christian at the time—Constantine was baptized shortly before he died, but had made Christianity the official state religion of the Roman Empire by the time of the Nicean council—intervened. The decision of the Trinitarians made Arius's questions heresy akin to revolt, so Constantine exiled the excommunicated Arius to Illyria (modern Albania).
Constantine's friend and Arian-sympathizer Eusebius, and a neighboring bishop, Theognis, were also exiled—to Gaul (modern France). In 328, however, Constantine reversed his opinion about the Arian heresy and had both exiled bishops reinstated. At the same time, Arius was recalled from exile. Eusebius eventually withdrew his objection, but still wouldn't sign the statement of faith.
Constantine's sister and Eusebius worked on the emperor to obtain reinstatement for Arius, and they would have succeeded, if Arius hadn't suddenly died—by poisoning, probably, or, as some prefer to believe, by divine intervention.
After Nicea
Arianism regained momentum and evolved (becoming popular with some of the tribes that were invading the Roman Empire, like the Visigoths) and survived in some form until the reigns of Gratian and Theodosius, at which time, St. Ambrose (c. 340–397) set to work stamping it out.
But the debate by no means was over in the 4th century. Debate continued into the fifth century and beyond, with:
" ... confrontation between the Alexandrian school, with its allegorical interpretation of scripture and its emphasis on the one nature of the divine Logos made flesh, and the Antiochene school, which favoured a more literal reading of scripture and stressed the two natures in Christ after the union." (Pauline Allen, 2000)
Anniversary of the Nicene Creed
August 25, 2012, marked the 1687th anniversary of the creation of the upshot of the Council of Nicea, an initially controversial document cataloging the basic beliefs of Christians -- the Nicene Creed.