Constantine the Great
The situation of the Christian church changed greatly in the early 300s. When Constantine I (“the Great”) became Roman emperor, he issued the Edict of Milan (313 AD) declaring freedom of religion. Soon after, he made Christianity the state religion. In just two decades, Christianity changed from being severely persecuted to being officially favoured.
Why did Constantine do this? He professed to be a Christian and was actively involved in church affairs. However, his motives might have been political, at least in part.
Constantine’s decisions resulted in profound changes, both in the church and in society. The church suddenly had freedom, financial support, and magnificent basilicas (large church buildings). In the Roman empire, laws were enacted that reflected Christian principles. Many of these have survived into our Western society: humane treatment of prisoners, more rights for slaves and wives, protection of newborn and unborn life. Also, Sunday was officially declared a holiday in which no work was to be done.
Besides the obvious advantages, these changes also had disadvantages for the Christian church. For instance, many joined the church without sincerity or depth of faith.
The Trinity
At the heart of the Christian faith is the conviction that Jesus Christ is God in the flesh. It is a profound challenge to explain how this is possible. Especially in the 3rd and 4th centuries AD, the church was forced to make statement about two profound mysteries.
The first mystery is that of the Trinity. The Bible speaks about God (“the Father”), about the Son of God (Jesus Christ), and about the Holy Spirit as individual, divine persons. At the same time, it insists that there is only one true God. How can the “Threeness” be reconciled with the “Oneness”?
Various solutions were proposed and rejected as heresy. The church rejected the idea that Father, Son, and Spirit are merely parts of the one God (partialism), as well as the idea that they are merely different modes of presentation of one God (modalism).
The church developed terminology to formulate the doctrine of the Trinity. God consists in “one divine Essence in three Persons”.
The two natures of Christ
The second mystery is that of the two natures of Jesus Christ. From the beginning, the church underscored that Jesus as the Son of God is fully divine; yet in the Incarnation he also became fully human. (This is also known as the hypostatic union.) It is a challenge to reconcile these two “natures” in one Person. This was the subject of many discussions and councils in the 4th and 5th centuries.
Arius
Arius, bishop of Alexandria, rejected the divinity of Jesus Christ. While he superficially agreed with the orthodox terminology (e.g. Jesus is the only-begotten Son of God), he insisted that the Son of God is not himself the High God, and did not exist eternally. One of his favourite mottoes was: ên hote ouk ên, “there was a time when he was not.”
Arius’s heresy is not only about the mystery of Jesus’s two natures. Ultimately it presents a more man-centred view of salvation.
The Council of Nicaea (325)
Arius’s teachings caused much trouble in the church. In 325 AD, Emperor Constantine called the bishops of the church together to resolve the issue. About 300 bishops met in Nicaea (northwestern Turkey).
The main opponents of Arius were Alexander and Athanasius. They convinced the council to condemn Arius’s teachings as heresy. Emperor Constantine banished Arius and some of his followers.
The Council produced a statement, summarizing the core of the Christian faith and the orthodox view of Jesus’s divinity. A key confession in this Nicene Creed is that Jesus Christ is “of the same essence” as the Father (Greek: homo-ousios).
The aftermath of Nicaea
However, Arius’s teaching remained extremely popular throughout the 4th century. As a compromise some taught that Jesus is homoiousios, “of similar essence” as the Father. The one-letter distinction between homo-ousios and homoiousios made for over 80 years of fierce debate!
In 381, a second Council was held in Constantinople. Here, the Arian view (in all its versions) was rejected once again. A more detailed statement (the Nicene-Constantinopolitan Creed) was written. It is the most widely accepted creed in the Christian church.
The discussions about Christ’s two natures would continue through another century and a number of councils.