How the Council of Nicaea changed Christianity forever

National Geographic

30-05-2025

Icon depicting the Emperor Constantine and the fathers of the Council of Nicaea of ​​325 with the Greek text of the Nicene-Constantinopolitan Creed of 381 in its liturgical form. Artist unknown. Photograph by Signal Photos/Alamy Stock Photo
This May marks 1,700 years since the convening of what is arguably the most important and influential council in Christian history. For three months in 325 CE, Emperor Constantine gathered hundreds of bishops from across the empire in Nicaea, on the northern coast of what is now Turkey. The resulting statement of belief—the Nicene Creed—was the first official declaration of Christian faith and remains foundational for Christians around the world to this day. Attend Sunday school or a Christian church of nearly any denomination, and you will encounter principles derived from the Nicene Creed. The debate
The task of the council was enormous: to establish correct Christian doctrine, fix the date of Easter, define episcopal jurisdictions, and devise protocols for addressing local schisms and dissent. But the most urgent matter under discussion at the council concerned the teachings of Arius, a prominent presbyter from Alexandria who had come into conflict with his bishop, Alexander of Alexandria.
Despite common misrepresentations, both Arius and Alexander affirmed that Jesus was the Son of God and divine. Both agreed—following the opening of the Gospel of John—that Jesus was present at the creation of the universe. Their disagreement did not concern whether Jesus was divine, but rather the manner of that divinity and his relationship to God the Father.
Arius contended that 'there was a time when [Jesus] was not'—a brief, primordial moment in which the Son did not yet exist. This view implied that Jesus was subordinate to the Father, or at least that the Son's divinity was contingent on that of the Father. Alexander, by contrast, asserted that Jesus had eternally coexisted with God the Father and was fully equal to him. The First Council of Nicaea as depicted by Italian painter Cesare Nebbia (1536-1614), on display at the Vatican Museums, Rome. Photograph by Album/Alamy Stock Photo
Underlying this theological dispute were key philosophical concepts drawn from Greek thinkers such as Plato. If the Father and the Son were too unified, as Alexander and his successor Athanasius argued, then the suffering experienced by the Son during the crucifixion would also have been experienced by God—an impossibility according to Platonic philosophy. On the other hand, if they were too separate, as Arius proposed, then Christianity appeared to abandon its monotheistic roots and embrace multiple deities. Each side emphasized a different concern about the nature of God.
At the council, representatives of each faction proposed a different term to express the relationship between the Father and the Son. Arius and his supporters favored homoiousios—meaning 'of a similar substance'—while Alexander's camp insisted on homoousios, or 'of the same substance.' Remarkably, the entire controversy hinged on the inclusion of a single Greek letter, iota—giving rise to the expressions 'an iota of difference' or 'a jot of difference.'
(What archaeology can tell us about Jesus' crucifixion) The Emperor weighs in
Constantine himself had a fairly tenuous grasp of the philosophical and theological nuances of the debate. At one point, according to his biographer Eusebius of Caesarea, he complained that the dispute was a fight 'over small and quite minute points.' Why, then, did he bother to convene such an expensive and time-consuming meeting? Roman emperors had long maintained that concord and uniform religious practices were essential to the success and stability of the empire. Constantine spent much of his career using force to reunify a divided realm; he could not tolerate discord within the Church. As renowned historian of early Christianity Paula Fredriksen puts it in her recently published book Ancient Christianities, Constantine and church leaders agreed that 'proper religion should be unanimous, the identity of and unity of the true church unambiguous.' Division in the church, Constantine said, was worse than war.
(Why Orthodox Christians celebrate Christmas in January) The outcome
The deliberations at the Council of Nicaea were marked by intense conflict. According to a14th-century legend, Saint Nicholas—the figure later associated with Santa Claus—became so enraged during the proceedings that he struck Arius across the face. While the historical accuracy of this episode is doubtful, it accurately reflects the fierceness of the debate.
Ultimately, the council ruled against Arius and produced a formal theological declaration: the Nicene Creed. The vote was overwhelmingly in favor. Only about 20 bishops initially refrained from supporting the creed, and just three—Arius and his two closest allies—refused to sign it. The remaining dissenters were later compelled to endorse the statement under pressure from Emperor Constantine. Although Constantine did not vote himself, he did intervene in the drafting, insisting on the inclusion of the term homoousios ('of one substance') in the final creed. The oldest surviving copy of the Nicene Creed, dating to the 6th century. Photograph by Pictorial Press Ltd/Alamy Stock Photo
For supporters of Arius, as Fredriksen notes, there were significant financial and political incentives to break ranks: Constantine transferred wealth to orthodox bishops, allowed them to travel at public expense, granted them legal authority as magistrates, and provided grain distributions for their churches.
Arius himself was exiled from Egypt and branded a heretic. Even after his death, orthodox Christians continued to attack him. They spread rumors of an undignified death—alleging that he died of explosive diarrhea in a public toilet. According to the legend, the force of his bowel movements caused his intestines to be expelled from his body. The story feels far-fetched. As Ellen Muehlberger, a professor at the University of Michigan, has written, this is one of a slew of early Christian fictions in which heretics and schismatics die in dramatic bathroom incidents. It had the effect of smearing Arius's teachings with excrement and bolstering the reputation of Nicaea and its decisions.
(Where is Santa buried? The resting place of the real St. Nick.) The lost church
For all its influence, the actual location for the meeting of the Council of Nicaea was, until very recently, completely unknown. Then, in 2018, after a century of fruitless efforts, scientists announced the discovery of ancient Roman ruins beneath the surface of the lake in Iznik, Turkey. Mustafa Şahin, the current head of archaeology at Bursa Uludağ University, had been searching the shores for years before he was shown some government survey pictures in 2014 that clearly revealed the outline of a large church beneath the water. The structure, which is located 165 feet off the coast of Iznik, is submerged 6-10 feet beneath the surface of the lake. Şahin and his collaborator biblical scholar Mark Fairchild believe that this is the place where the Council of Nicaea met.
Archeological investigation revealed that the underwater basilica collapsed during an earthquake in 740 CE and was never rebuilt. Over time changes in the water level of the lake submerged the ruins entirely. For intrepid travelers there are plans to make the ruins accessible to visitors. In 2018 the mayor of Iznik, Alinur Aktas, said that professional diving classes would be available to tourists who want to visit the site.
For Christians today, Nicaea remains a symbol of a time when the Church was less divided. Though the attendees were anything but unified and civil at the time, religious leaders now see the Nicene Creed as a symbol of shared agreement and belief among the denominations that make up modern Christianity. It predates the schisms that eventually separated the various branches of Orthodox Christianity from Roman Catholicism. Prior to his death, Pope Francis had hoped to join the Eastern Orthodox Patriarch of Constantinople, Bartholomew I, in Nicaea for the anniversary. Pope Leo XIV will make the trip in November, expressing a desire to 'continue the dialogue between East and West [Orthodox Christianity and Roman Catholicism].' All of which shows that even when submerged under water, Nicaea still stands as a beacon of hope for Christians around the world.