Council of Nicaea: 1,700 years of Christian unity amid division In the summer of A.D. 325, more than 300 bishops gathered in Nicaea \u2014 located in modern-day northern Turkey \u2014 to promulgate a common Christian creed, settle Christological disputes that arose from the Arian heresy, and promote unity in the Church. The first ecumenical council, known as the Council of Nicaea, is still accepted as authoritative by the Catholic Church, the Eastern Orthodox Church, and many Protestant denominations. The common beliefs still offer a strong element of unity in an otherwise fractured Christianity 1,700 years later. During the council, the bishops established the initial formulation of the Nicene Creed, which is the profession of faith still recited at the Catholic Mass, Orthodox liturgies, and some Protestant services. It also rejected heretical Arian claims that Christ was a created being who lacked an eternal divine nature and rather confirmed that the Son is eternally begotten of the Father. The council was called by Emperor Constantine \u2014 a convert to Christianity \u2014 less than 15 years after the empire halted the persecution of Christians and granted them the freedom to worship. It came just 20 years after the reign of Emperor Diocletian, who brutally persecuted Christians for their rejection of paganism. \u201cThat council represents a fundamental stage in the development of the creed shared by all the Churches and ecclesial communities,\u201d Pope Leo XIV said two weeks ago, acknowledging the 1,700th anniversary. \u201cWhile we are on the path towards the reestablishment of full communion among all Christians, we recognize that this unity can only be unity in faith,\u201d the pontiff said. The primary purpose of the council was to settle a major question about Christ\u2019s divine nature and address Arianism, which was a heresy promoted by the priest Arius asserting that Jesus Christ was a created being and not eternal. \u201cArius began to preach something that was scandalous to many Christian believers and [which] seemed incompatible to the Christian faith as witnessed to in Scripture and transmitted through the tradition of the Church,\u201d Dominican Father Dominic Legge, the director of the Thomistic Institute and professor of theology, told CNA. Arius wrote in \u201cThalia\u201d that he believed the Father \u201cmade the Son\u201d and \u201cproduced him as a son for himself by begetting him.\u201d He wrote that \u201cthe Son was not always [in existence], for he was not [in existence] before his generation.\u201d He asserted that Christ was not eternal but \u201ccame into existence by the Father\u2019s will.\u201d Arius contested that Christ \u201cis not true God\u201d but was rather \u201cmade God by participation.\u201d Legge said that Arius understood that \u201cthere\u2019s an infinite gap between God and creatures,\u201d but where he was mistaken was that \u201che thought that the Son was on the \u2018creature\u2019 side of that gap\u201d and \u201cnot equal in divinity to God.\u201d \u201cTherefore, he considered him to be the highest creature,\u201d Legge added. \u201cThe first creature, but nonetheless a creature.\u201d Legge said that at Nicaea there was \u201ca consensus of bishops with very different approaches to the mystery of God and they could see that Arius had to be wrong and so they condemned him and they affirmed that the Son is \u2018God from God, true God from true God.\u2019\u201d The language adopted at Nicaea expressly contradicted Arius, affirming Christ is \u201ctrue God from true God, begotten not made, of one substance with the Father.\u201d It condemned Arius\u2019 view as heresy. The vote was nearly unanimous with more than 300 bishops voting in favor of this text and only two siding with Arius. St. Athanasius, one of the most outspoken opponents of Arianism at the council and in its aftermath, wrote in his First Discourse Against the Arians in the mid-fourth century that \u201cthe Scriptures declare the Son\u2019s eternity.\u201d Athanasius notes, for example, the Gospel of St. John states that \u201cin the beginning was the Word, and the Word was with God, and the Word was God.\u201d He also cites Chapter 8 of the same Gospel in which Christ declares \u201cbefore Abraham was, I am,\u201d invoking the divine name used by God to indicate his eternity when appearing to Moses as the burning bush. \u201cThe Lord himself says, \u2018I am the Truth,\u2019 not \u2018I became the Truth,\u2019 but always, \u2018I am \u2014 I am the Shepherd \u2014 I am the Light\u2018 \u2014 and again, \u2018Call me not, Lord and Master? And you call me well, for so I am,\u2018\u201d Athanasius wrote. \u201cWho, hearing such language from God, and the Wisdom, and Word of the Father, speaking of himself, will any longer hesitate about the truth, and not immediately believe that in the phrase \u2018I am,\u2018 is signified that the Son is eternal and without beginning?\u201d Legge noted that Athanasius also warned that Arius\u2019 position \u201cthreatened the central truth of Christianity that God became man for our salvation.\u201d Unifying the Church in the fourth century Prior to the Council of Nicaea, bishops in the Church held many synods and councils to settle disputes that arose within Christianity. This includes the Council of Jerusalem, which was an apostolic council detailed in Acts 15, and many local councils that did not represent the entire Church. Regional councils \u201chave a kind of binding authority \u2014 but they\u2019re not global,\u201d according to Thomas Clemmons, a professor of Church history at The Catholic University of America. When the Roman Empire halted its Christian persecution and Emperor Constantine converted to the faith, this allowed \u201cthe opportunity to have a more broad, ecumenical council,\u201d Clemmons told CNA. Constantine embraced Christianity more than a decade before the council, though he was not actually baptized until moments before his death in A.D. 337. Constantine saw a need for \u201ca certain sense of unity,\u201d he said, at a time with theological disputes, debates about the date of Easter, conflicts about episcopal jurisdictions, and canon law questions. \u201cHis role was to unify and to have [those] other issues worked out,\u201d Clemmons said. The pursuit of unity helped produce the Nicene Creed, which Clemmons said \u201chelps to clarify what more familiar scriptural language doesn\u2019t.\u201d Neither the council nor the creed was universally adopted immediately. Clemmons noted that it was more quickly adopted in the East but took longer in the West. There were several attempts to overturn the council, but Clemmons said \u201cit\u2019s later tradition that will affirm it.\u201d \u201cI don\u2019t know if the significance of it was understood [at the time],\u201d he said. The dispute between Arians and defenders of Nicaea were tense for the next half century, with some emperors backing the creed and others backing Arianism. Ultimately, Clemmons said, the creed \u201cconvinces people over many decades but without the imperial enforcement you would expect.\u201d It was not until 380 when Emperor Theodosius declared that Nicene Christianity was the official religion of the Roman Empire. One year later, at the First Council of Constantinople, the Church reaffirmed the Council of Nicaea and updated the Nicene Creed by adding text about the Holy Spirit and the Church. Common misconceptions There are some prominent misconceptions about the Council of Nicaea that are prevalent in modern society. Clemmons said the assertion that the Council of Nicaea established the biblical canon \u201cis probably the most obvious\u201d misconception. This subject was not debated at Nicaea and the council did not promulgate any teachings on this matter. Another misconception, he noted, is the notion that the council established the Church and the papacy. Episcopal offices, including that of the pope (the bishop of Rome), were already in place and operating long before Nicaea, although the council did resolve some jurisdictional disputes. Other misconceptions, according to Clemmons, is an asserted \u201cnovelty\u201d of the process and the teachings. He noted that bishops often gathered in local councils and that the teachings defined at Nicaea were simply \u201cthe confirmation of the faith of the early Church.\u201d Follow Pope Leo XIV\u2019s first Apostolic Journey to T\u00fcrkiye (Turkey) and Lebanon This CNA article was first published on June 5, 2025, and has been updated. Receive the most important news from EWTN Vatican via WhatsApp. It has become increasingly difficult to see Catholic news on social media. Subscribe to our free channel today EWTN Vatican on WhatsApp Tyler Arnold Would you like to receive the latest updates on the Pope and the Vatican Receive articles and updates from our EWTN Newsletter. 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