First Council of Nicaea (325): The Nicene Creed and Arianism

The First Council of Nicaea was a gathering of Christian bishops called by the Roman emperor Constantine in AD 325 at Nicaea, now İznik in Turkey. It is regarded as the first ecumenical, or general, council of the Church. The bishops condemned the teaching of the Alexandrian priest Arius, adopted the Nicene Creed and agreed a common date for Easter, decisions that shaped Christian belief and the relationship between church and state for centuries.

Background: a church newly free

Only a few years earlier Christians had suffered the Great Persecution under Diocletian. The policy of religious freedom agreed by Constantine and Licinius in 313, known as the Edict of Milan, ended that era. When Constantine defeated Licinius in 324 and became sole emperor, he hoped that a united Church would help hold the empire together.

Instead he found the eastern churches divided. Two disputes concerned him most: a theological controversy that had spread from Egypt across the East, and disagreement over how to fix the date of Easter. There were also local schisms, such as the Melitian schism in Egypt, left over from the persecution.

The Arian controversy

Around 318 to 321 a dispute broke out in Alexandria between its bishop, Alexander, and Arius, a respected priest in charge of the city’s Baucalis church. The question was how the Son of God, Christ, was related to God the Father.

Arius taught that the Son was created by the Father before all ages. In his view the Son was divine in a lesser sense and had a beginning; his followers summed this up in the phrase “there was when he was not”. Alexander insisted that the Son had always existed with the Father and shared his divine nature fully.

A council of Egyptian bishops excommunicated Arius, but he found powerful supporters elsewhere, especially Eusebius, bishop of Nicomedia, the eastern imperial city. Letters, sermons and popular songs spread the dispute. Constantine sent his adviser, Bishop Hosius (or Ossius) of Corduba in Spain, to reconcile the two sides, but the mission failed. An episcopal synod at Antioch early in 325 condemned Arius’s teaching.

The council meets

Constantine summoned bishops from across the empire. The council was first planned for Ancyra (modern Ankara) but was moved to Nicaea, a city near the imperial residence at Nicomedia and easy to reach by land and sea. The emperor paid travel costs from the imperial post system, an unprecedented sign of state support for the Church.

The council opened in late May or June 325, probably in the imperial palace at Nicaea. Estimates of attendance range from about 250 to about 300 bishops. Eusebius of Caesarea, who attended, says more than 250; Athanasius gives about 300; the traditional figure of 318 appears later, echoing the 318 servants of Abraham in Genesis.

Almost all the bishops came from the Greek-speaking East. The western Church sent only a handful, including Hosius of Corduba, Caecilian of Carthage and two priests, Vitus and Vincentius, representing the aged Bishop Sylvester of Rome. A few came from beyond the frontier, among them a bishop from Persia and one from the Goths.

Constantine attended in person and, according to Eusebius, entered the hall in splendid robes and spoke in Latin, with interpreters translating into Greek. He urged peace and took part in the discussions, although bishops conducted the theological debate. Hosius probably presided over the sessions.

The supporters of Arius were a minority. A statement of faith presented by his allies was rejected. Eusebius of Caesarea then read out the creed of his own church, which was accepted as broadly orthodox, but it was revised to exclude Arian interpretations.

The key addition was the Greek word homoousios, meaning “of one substance” or “of the same essence”. By declaring the Son homoousios with the Father, the bishops ruled out the idea that the Son was a created being. The word was controversial because it does not appear in the Bible and some feared it blurred the distinction between Father and Son. Constantine himself is said to have backed its inclusion.

The Nicene Creed of 325

The creed adopted at the council, usually dated to 19 June 325, affirmed belief in one God, the Father almighty, and in one Lord Jesus Christ, the Son of God, begotten of the Father, “true God from true God, begotten not made, of one substance with the Father”. It ended briefly with belief in the Holy Spirit.

Attached to the creed were anathemas, or formal condemnations, rejecting those who said that there was a time when the Son did not exist or that he was made from nothing.

Almost all the bishops signed. Arius and two Libyan bishops, Theonas of Marmarica and Secundus of Ptolemais, refused and were exiled to Illyricum in the Balkans. Eusebius of Nicomedia and Theognis of Nicaea signed the creed but not the condemnation of Arius, and were exiled a few months later.

Other decisions

• Easter: The council agreed that all churches should celebrate Easter on the same Sunday, independently of the Jewish calendar for Passover. It did not lay down a detailed method of calculation; the practice of Alexandria gradually became the standard.
• Canons: Twenty canons, or rules, were issued. They addressed the ordination of clergy, the readmission of those who had lapsed during persecution, the rights of the great sees of Alexandria, Rome and Antioch, and the honour due to the bishop of Jerusalem. One canon forbade kneeling to pray on Sundays and during the season after Easter.
• Melitian schism: A compromise allowed Melitius of Lycopolis and his clergy to keep their positions under Alexander’s authority.

The council ended in July 325, when Constantine invited the bishops to a banquet celebrating the twentieth year of his reign. Eusebius describes the soldiers standing guard as the bishops passed into the palace, a scene he compared to a vision of the kingdom of Christ.

Key people

Constantine I was not yet baptised but saw himself as a servant of the Christian God with a duty to keep the Church united. He summoned the council and enforced its verdict.

Arius (c. 250/256–336) was a popular, ascetic priest in Alexandria, trained in the theological tradition of Antioch. Few of his writings survive, mostly in quotations by his opponents.

Alexander of Alexandria led the case against Arius as bishop of the most important see in the East after Rome. He died in 328.

Athanasius (c. 296–373) attended as Alexander’s deacon and secretary. As bishop he spent decades defending the council, and his writings are the main source for the creed’s later history.

Eusebius of Caesarea, bishop and historian, wrote the only eyewitness narrative, in his Life of Constantine and in a letter to his own congregation explaining why he signed.

Aftermath: the controversy continues

Nicaea did not end the dispute. Within a few years Constantine recalled Arius and the exiled bishops. Athanasius, Alexander’s young deacon at the council and bishop of Alexandria from 328, became the leading defender of Nicaea and was exiled five times. Arius died in Constantinople in 336, just before he was to be readmitted to communion, and Constantine himself was baptised in 337 by Eusebius of Nicomedia.

Under Constantine’s son Constantius II, compromise formulas that avoided homoousios were favoured, and missionaries of this kind spread Christianity among the Goths, as seen in Wulfila’s Gothic Bible. The Nicene position was finally confirmed at the Council of Constantinople in 381 under Theodosius I, which approved an expanded creed. That Niceno-Constantinopolitan Creed is still recited in Catholic, Orthodox, Anglican and many Protestant churches.

Myths and facts

Myth: Nicaea decided which books belong in the Bible. No surviving evidence suggests that the council discussed the canon of scripture. The idea was popularised in modern times, including by the novel The Da Vinci Code.

Myth: Nicaea invented the divinity of Christ. Christians had worshipped Christ as divine long before 325. The debate was about how to describe his relation to the Father, not whether he was divine at all.

Myth: Saint Nicholas slapped Arius at the council. This story appears only in much later legends. Nicholas of Myra’s name is missing from the earliest lists of participants, and the episode is not considered historical.

Fact: the emperor played a central role. Constantine summoned the council, paid for it, attended it and enforced its decisions with exile. This set a precedent for imperial involvement in church affairs that shaped the later Byzantine world centred on Constantinople.

Timeline

• c. 318–321: Arius is condemned by Bishop Alexander and a council in Alexandria.
• 324, 18 September: Constantine defeats Licinius at Chrysopolis and becomes sole emperor.
• 325, early: A synod at Antioch condemns Arian teaching.
• 325, May or June: The council opens at Nicaea.
• 325, c. 19 June: The Nicene Creed is adopted; Arius is exiled.
• 325, July: The council closes with a banquet for Constantine’s twentieth anniversary.
• 328: Athanasius becomes bishop of Alexandria.
• 336: Arius dies in Constantinople.
• 381: The Council of Constantinople confirms and expands the Nicene faith.

Why it matters

The First Council of Nicaea established the model of a general council of bishops settling doctrine for the whole Church, and its creed remains the most widely shared statement of Christian belief. It also marked a new partnership between the Roman state and the Church. Its 1,700th anniversary in 2025 was marked by Christians of many traditions, a sign of its lasting place in Christian history.