The Council of Nicaea in 325 as depicted in a fresco in Salone Sistino at the Vatican. / Credit: Giovanni Guerra (1544-1618), Cesare Nebbia (1534-1614) e aiuti, Public domain, via Wikimedia Commons

Washington, D.C. Newsroom, Nov 28, 2025 / 10:00 am (CNA).

In the summer of A.D. 325, more than 300 bishops gathered in Nicaea — located in modern-day northern Turkey — 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 — a convert to Christianity — 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.

“That council represents a fundamental stage in the development of the creed shared by all the Churches and ecclesial communities,” Pope Leo XIV said in May, acknowledging the 1,700th anniversary.

“While 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,” the pontiff said.

The Arian heresy

The primary purpose of the council was to settle a major question about Christ’s 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.

“Arius 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,” Dominican Father Dominic Legge, the director of the Thomistic Institute and a professor of theology, told CNA.

Arius wrote in “Thalia” that he believed the Father “made the Son” and “produced him as a son for himself by begetting him.” He wrote that “the Son was not always [in existence], for he was not [in existence] before his generation.” He asserted that Christ was not eternal but “came into existence by the Father’s will.” Arius contested that Christ “is not true God” but was rather “made God by participation.”

Legge said that Arius understood that “there’s an infinite gap between God and creatures,” but where he was mistaken was that “he thought that the Son was on the ‘creature’ side of that gap” and “not equal in divinity to God.”

“Therefore, he considered him to be the highest creature,” Legge added. “The first creature, but nonetheless a creature.”

Legge said that at Nicaea there was “a 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 ‘God from God, true God from true God.’”

The language adopted at Nicaea expressly contradicted Arius, affirming Christ is “true God from true God, begotten not made, of one substance with the Father.” It condemned Arius’ 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 “the Scriptures declare the Son’s eternity.”

Athanasius notes, for example, the Gospel of St. John states that “in the beginning was the Word, and the Word was with God, and the Word was God.” He also cites Chapter 8 of the same Gospel in which Christ declares “before Abraham was, I am,” invoking the divine name used by God to indicate his eternity when appearing to Moses as the burning bush.

“The Lord himself says, ‘I am the Truth,’ not ‘I became the Truth,’ but always, ‘I am — I am the Shepherd — I am the Light‘ — and again, ‘Call me not, Lord and Master? And you call me well, for so I am,‘” Athanasius wrote. “Who, 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 ‘I am,‘ is signified that the Son is eternal and without beginning?”

Legge noted that Athanasius also warned that Arius’ position “threatened the central truth of Christianity that God became man for our salvation.”

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 “have a kind of binding authority — but they’re not global,” 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 “the opportunity to have a more broad, ecumenical council,” 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 “a certain sense of unity,” he said, at a time with theological disputes, debates about the date of Easter, conflicts about episcopal jurisdictions, and canon law questions.

“His role was to unify and to have [those] other issues worked out,” Clemmons said.

The pursuit of unity helped produce the Nicene Creed, which Clemmons said “helps to clarify what more familiar scriptural language doesn’t.”

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 “it’s later tradition that will affirm it.”

“I don’t know if the significance of it was understood [at the time],” 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 “convinces people over many decades but without the imperial enforcement you would expect.”

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 “is probably the most obvious” 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 “novelty” of the process and the teachings. He noted that bishops often gathered in local councils and that the teachings defined at Nicaea were simply “the confirmation of the faith of the early Church.”

This story was first published on June 5, 2025, and has been updated.

Pope Leo XIV and Ecumenical Patriarch Bartholomew I of Constantinople at an ecumenical event marking the 1,700th anniversary of Nicene Creed, in Iznik, Turkey, on Nov. 28, 2025. / Credit: Vatican Media/Screenshot

Iznik, Turkey, Nov 28, 2025 / 08:05 am (CNA).

Pope Leo XIV commemorated the 1,700th anniversary of the First Council of Nicaea on Friday in the Turkish city historically known as the birthplace of the Nicene Creed, calling Christians to overcome “the scandal of divisions” and to renew their commitment to unity.

The pope spoke during an ecumenical prayer service held at the archaeological site of the ancient Basilica of St. Neophytos on the shore of Lake Iznik, southeast of Istanbul. The gathering marked one of the most symbolic moments of his apostolic visit to Turkey, which has focused heavily on ecumenical and interreligious outreach.

“We are all invited to overcome the scandal of divisions,” he said, urging Christians to nurture “the desire for unity for which the Lord Jesus prayed and gave his life.”

Pope Leo and Ecumenical Patriarch Bartholomew I, considered first among equals among Eastern Orthodox bishops, were welcomed by two senior Orthodox bishops before proceeding to a platform beside the submerged ruins of the basilica. The two leaders stood before icons of Christ and of the council and lit candles together.

Iznik, formerly Nicaea, is located about 81 miles southeast of Istanbul. The remains of an early Christian basilica dedicated to St. Neophytos, a young martyr killed in 303 during the persecutions of Diocletian, were first identified in 2014 after aerial photographs revealed the outline of a submerged church. The basilica collapsed during an earthquake in 740, and its ruins are now visible from the lakeshore.

In his homily, Leo said the anniversary was “a precious opportunity to ask ourselves who Jesus Christ is in the lives of men and women today, and who he is for each one of us personally.” He cautioned against reducing Christ to “a kind of charismatic leader or superman,” recalling Arius’ denial of Christ’s divinity and the council’s defense of the full humanity and full divinity of Jesus.

“If God did not become man, how can mortal creatures participate in his immortal life?” the pope asked, emphasizing what was at stake in the fourth-century debate.

Leo said the Nicene confession of faith remains a foundation for unity among Christians worldwide. Quoting the creed, he underlined the proclamation of Christ as “consubstantial with the Father,” describing it as “a profound bond already uniting all Christians.” Citing St. Augustine, he added: “Although we Christians are many, in the one Christ we are one.”

A reconciled Christianity, he continued, can “bear credible witness to the Gospel” and offer “a proclamation of hope for all.”

The pope also extended his appeal for fraternity beyond the Christian world, insisting that authentic recognition of God as Father requires honoring all people as brothers and sisters. He warned against using religion “to justify war, violence, or any form of fundamentalism or fanaticism,” and called instead for “fraternal encounter, dialogue, and cooperation.”

Pope Leo’s schedule in Turkey includes a series of ecumenical events, among them the signing of a joint declaration with Patriarch Bartholomew I on Nov. 29 at the Patriarchal Palace. His trip also carries an interreligious dimension. Earlier on Friday he met the chief rabbi of Turkey, discussing the visit as a sign of peace and support for all religious communities. On Saturday, Nov. 29, he will visit the Sultan Ahmed Mosque.

Pope Leo XIV visits a care home for the elderly run by a community of the Little Sisters of the Poor in Istanbul, Turkey, on Nov. 28, 2025. / Credit: Vatican Media

Istanbul, Turkey, Nov 28, 2025 / 03:00 am (CNA).

Pope Leo XIV visited the Nursing Home of the Little Sisters of the Poor in Istanbul on Friday, telling the community that Christian charity begins not with doing but with being — i.e., living a real communion with those one serves.

“The secret of Christian charity is that before being for others, we must first be with others in a communion based on fraternity,” he said during the encounter on Nov. 28, the second day of his apostolic trip to Turkey, where he is marking the 1,700th anniversary of the First Council of Nicaea.

A papal stop at a charitable institution has become customary during international journeys, and Pope Leo chose to spend time with the elderly as a sign of closeness to those often marginalized in modern societies.

Founded in France in 1839 by St. Jeanne Jugan, the Little Sisters of the Poor serve elderly people in need around the world, including in Turkey, where they welcome residents of different religious backgrounds. The pope was greeted at the residence by the mother superior, former superior, and provincial leader before proceeding to the chapel to meet residents, staff, and benefactors.

Reflecting on the congregation’s name, the pope told the sisters that their mission mirrors the life of Christ himself. “The Lord has called you not only to assist or help the poor but has also called you to be their ‘sisters.’ You are to be like Jesus, whom the Father sent to us not only to help and serve us but also to be our brother.”

Turning to the residents, he warned that the word “elderly” risks losing its meaning in cultures driven by efficiency and materialism. Such attitudes, he said, lead societies to forget the dignity and value of older persons. Scripture and tradition, by contrast, present the elderly as bearers of memory and wisdom.

“As Pope Francis loved to repeat — the elderly are the wisdom of a people, a treasure for their grandchildren, families, and society as a whole,” he said.

Pope Leo concluded by thanking the community for its patient, prayerful witness and prayed that the Lord would strengthen all who live and serve in the home.

Pope Leo XIV encourages Catholic clergy, religious brothers and sisters, and lay pastoral workers to see the Catholic community’s small size as a strength during an encounter at the Cathedral of the Holy Spirit in Istanbul, Turkey, on Nov. 28, 2025. / Credit: Vatican Media

Istanbul, Turkey, Nov 28, 2025 / 01:55 am (CNA).

Pope Leo XIV encouraged Turkey’s small Catholic community Friday to rediscover what he called the Gospel’s “logic of littleness,” urging them not to be discouraged by their tiny numbers but to recognize in them the strength of authentic Christian witness.

The pope addressed bishops, priests, religious, pastoral workers, and laypeople at the Cathedral of the Holy Spirit in Istanbul on his second day in the country. Catholics in Turkey make up roughly 0.05% of the nation’s 85 million people.

Calling Turkey a “holy land” where the Old and New Testaments meet, the pope recalled the deep Christian roots of the region: Abraham’s journey through Harran, the early Christian communities in Antioch and Ephesus, and the long and influential history of Byzantine Christianity. He noted in particular that the Ecumenical Patriarchate of Constantinople, currently led by Patriarch Bartholomew I, remains “a point of reference” both for its Greek faithful and for other Orthodox churches.

The pope warned Christians not to treat this heritage merely as a memory of past greatness. Instead, he urged them to adopt “an evangelical vision” that sees their present reality through the Holy Spirit’s light.

“When we look with God’s eyes, we discover that he has chosen the way of littleness,” he said, pointing to the mustard seed, the little ones praised by Jesus, and the quiet growth of the kingdom of God. The Church’s true strength, he explained, “does not lie in her resources or structures,” nor in numbers or influence, but in remaining gathered around Christ and sent by the Holy Spirit.

Quoting Jesus’ words “Do not be afraid, little flock,” the pope encouraged Christians in Turkey to cultivate hope. He pointed to the growing number of young people approaching the Catholic Church as a sign of promise and asked communities to continue welcoming and accompanying them.

He urged particular dedication to ecumenical and interreligious dialogue, the transmission of the faith to local communities, and pastoral service to refugees and migrants — many of whom are among the most vulnerable people in the country. The pope also noted that many Catholics in Turkey come from abroad, a reality that calls for a deeper process of inculturation so that the language and culture of the country become “more and more your own.”

The pope highlighted Turkey’s unique role in the history of the Church, recalling that the first eight ecumenical councils were held on its soil. Marking the 1,700th anniversary of the First Council of Nicaea, he said the council continues to pose three questions to Christians today: What is the essence of the faith? Who is Jesus for us? And how should doctrine be expressed in ways that speak to contemporary culture?

He warned against what he described as a “new Arianism,” a version of the heresy that divided Christianity in its early centuries, that reduces Jesus to a moral teacher or heroic figure while denying his divinity and lordship over history.

Before concluding, the pope invoked the memory of St. John XXIII, who served in Turkey and wrote affectionately of its people. Reflecting on the saint’s image of Bosporus fishermen laboring through the night, he encouraged Turkish Catholics to persevere in the same spirit: working faithfully, joyfully, and courageously “in the Lord’s boat.”

The Cathedral of the Holy Spirit, where the meeting took place, was built in 1846 and houses relics of early popes, including St. Linus. A statue of Pope Benedict XV stands in its courtyard, erected in gratitude for his efforts to help victims of the 1915–1918 war. The inscription honors him as a “benefactor of peoples, without distinction of nationality or religion.”

Watch Pope Leo XIV’s full homily here.

Workers erect the Vatican’s 2025 Christmas tree in St. Peter’s Square on Thursday, Nov. 27, 2025. / Credit: Vatican Media

Vatican City, Nov 27, 2025 / 14:30 pm (CNA).

A towering Christmas tree now stands in the center of St. Peter’s Square after the spruce arrived at the Vatican on Thursday morning. 

The 88-foot-tall spruce tree from Italy’s Bolzano province was erected next to the ancient Egyptian obelisk that stands in the middle of the 17th-century Baroque square designed by Gian Lorenzo Bernini.

This year, the northern Italian municipalities of Lagundo and Ultimo gifted the Christmas tree to the Vatican. The tree was harvested in the alpine valley of Ultimo.

In an Oct. 20 interview published on the Vatican State website, Bishop Ivo Muser of the Diocese of Bolzano-Bressanone said the tree reaffirms the local Church’s “spiritual and emotional bond” with the pope. 

“It is a way of saying: ‘We are with you, Pope Leo; we wish to pray with you and share the joy of Christmas with you,” he said.

“The tree thus becomes an ‘ambassador’ of our territory, our culture, and our faith — a way of bringing a small piece of our local Church into the heart of the universal Church,” he added.

The Vatican’s large-scale Nativity display — donated by the Italian Diocese of Nocera Inferiore-Sarno — is currently under construction behind covered fencing in St. Peter’s Square.

The highly-awaited 2025 Nativity scene will honor St. Alphonus Maria de Liguori, whose remains lie in the southern Italian diocese. In Italy, St. Alponsus is famous for composing the famous Italian Christmas carol “Tu scendi dalle stelle” (“From Starry Skies Descending”).

Bishop Giuseppe Giudice of the Diocese of Nocera Inferiore-Sarno said the Nativity project for the Vatican, which involved a “long period of preparation,” will also showcase local Neapolitan Christmas traditions.  

“I am happy to say that everyone working on the project is from our wonderful region, and the Nativity scene will be rich in elements typical of our local Agro Nocerino-Sarnese area,” he said in an Oct. 24 interview published by Vatican City State.  

The Vatican will hold a special ceremony on Dec. 7 at 6:30 p.m. local time to present the Christmas tree and Nativity scene to the public. The display will be open to the public until mid-January 2026.

Interior of the Church of Jesus and Mary in Rome, Italy / Credit: Mentnafunangann / Wikimedia (CC BY-SA 4.0)

Rome, Italy, Nov 26, 2025 / 10:15 am (CNA).

At a Mass marking 25 years since the Holy See signed a foundational agreement with Slovakia, U.S. ambassador to the Holy See Brian Burch praised the “rich history” of Catholic peoples in Central Europe.

Pope Leo XIV meets with Ukrainian children who were welcomed by Caritas Italy during the summer on July 3, 2025, at the Vatican. / Credit: Vatican Media

CNA Staff, Nov 26, 2025 / 06:00 am (CNA).

At the forefront of the work of repatriation and recovery of Ukrainian children swept up in the country’s war with Russia is Caritas Ukraine.

null / Credit: Patrick Thomas/Shutterstock

EWTN News, Nov 26, 2025 / 05:00 am (CNA).

Slovenia rejected euthanasia legislation in a Nov. 23 referendum, with 53% voting against the law backed by Catholic bishops and civil groups.

Prince Albert II of Monaco in 2025. / Credit: VALERY HACHE/Getty Images

ACI Prensa Staff, Nov 25, 2025 / 17:01 pm (CNA).

Prince Albert II of Monaco has announced that he will not sign into law a bill that aims to relax the conditions for accessing abortion in the European microstate.

null / Credit: itakdalee/Shutterstock

EWTN News, Nov 24, 2025 / 16:08 pm (CNA).

Published on Oct. 30, the document is intended to serve as an orientation aid for Catholic and other schools in Germany.