The Council of Nicaea and the Arian Controversy (318-381)
In AD 325 the Roman emperor Constantine convened the first ecumenical council of Christian bishops at Nicaea to settle a dispute over the nature of Christ that had divided the churches of the empire. This story chronicles the Arian controversy, the creed and canons the council produced, and the decades of theological and political struggle that followed until Nicene orthodoxy was affirmed at Constantinople in 381.
Events
The Arian Controversy Begins in Alexandria
Arius, a presbyter of the parish of Baucalis in Alexandria, began teaching that the Son was created by the Father and therefore subordinate to him, using the formula that "there was when he was not." Bishop Alexander of Alexandria rejected the teaching as denying the Son's full divinity. Scholars place the start of the dispute between 318 and 322; Arius's own views survive only in fragments quoted largely by his opponents.
Location: Alexandria, Egypt
Alexander of Alexandria Condemns Arius
Alexander convened a local synod of Egyptian and Libyan bishops that condemned Arius's teaching and exiled him from Alexandria. Arius found support outside Egypt, most importantly from Eusebius of Nicomedia, a bishop with close ties to the imperial court, and spread his views through letters and popular songs composed for travelers, sailors, and merchants. The dispute ceased to be a local matter.
Location: Alexandria, Egypt
Constantine Becomes Sole Emperor and Moves to Mediate
After defeating his rival Licinius at Chrysopolis, Constantine became sole ruler of the Roman Empire. Wary that the Alexandrian dispute threatened unity in a recently unified empire, he sent the Spanish bishop Hosius of Corduba to investigate and urged both sides in letters to reconcile, comparing the quarrel to a philosophical debate unworthy of such passion. The mediation failed, and Constantine resolved to settle the matter with an empire-wide council.
Location: Chrysopolis (near Nicomedia)
The First Council of Nicaea Convenes
Constantine convened a council of Christian bishops at Nicaea, close to his residence at Nicomedia. At least 200 bishops attended, with the traditional figure being 318; only a handful came from the western church, and Hosius of Corduba may have presided. The council was the first attempt to reach consensus for all Christendom through an assembly of bishops, and the emperor attended in person.
Location: Nicaea, Bithynia (now Iznik, Turkey)
The Nicene Creed and the Council's Canons
By the end of July the council produced the creed declaring the Son "of one substance" (homoousios) with the Father, anathematizing Arius's teaching with explicit formulae. It also promulgated twenty canons on church discipline and mandated a uniform date for Easter. Historians note that the term homoousios was novel and ambiguous, and debate how far the settlement reflected genuine consensus, theological argument, or imperial pressure; only two bishops reportedly refused to sign.
Location: Nicaea, Bithynia (now Iznik, Turkey)
Arius Recalled; Athanasius Becomes Bishop of Alexandria
Within a few years Arius was recalled from exile through the influence of Eusebius of Nicomedia and the imperial court, and Constantine pressed for his readmission to communion. Athanasius, a deacon at Nicaea, became bishop of Alexandria in 328 and refused to restore Arius, becoming the leading defender of the Nicene formula. The controversy shifted from theology to a long contest over episcopal authority and imperial favor.
Location: Alexandria and Constantinople
Athanasius Deposed and Exiled; Arius Dies in Constantinople
A council at Tyre deposed Athanasius on charges brought by his opponents and sent him into exile, the first of several expulsions he suffered over the following decades. Arius, restored to imperial favor, died suddenly in Constantinople in 336 on the eve of a scheduled ceremony to receive him back into communion; church historians reported the death in striking terms, and later Nicene writers treated it as divine judgment. The sources for these events are largely the work of partisans on both sides.
Location: Tyre and Constantinople
The Councils of Ariminum and Seleucia
Under the emperor Constantius II, the eastern and western churches met at Seleucia and Ariminum and were pressed to adopt a creed describing the Son as "like" the Father without further qualification. The resulting formula, imposed with imperial pressure and the detention of bishops, marked the high point of anti-Nicene ascendancy; Athanasius spent years in hiding, and the Nicene cause seemed nearly extinguished in the empire.
Location: Ariminum (Rimini) and Seleucia (Silifke)
The Edict of Thessalonica
The emperor Theodosius I issued the Edict of Thessalonica making Nicene Christianity the religion of the Roman Empire and ordering other Christians to accept the doctrine of the Trinity as defined at Nicaea. The edict reversed decades of imperial support for anti-Nicene positions and gave the Nicene settlement the force of state law, with state persecution following for those who refused.
Location: Thessalonica and Constantinople
The First Council of Constantinople Confirms Nicene Orthodoxy
Theodosius convened a second ecumenical council at Constantinople, attended by about 150 bishops, all from the eastern empire. It reaffirmed the faith of Nicaea and expanded the creed with clauses on the Holy Spirit, condemned the remaining anti-Nicene parties, and left Arianism marginalized within the empire. The Nicene-Constantinopolitan creed that resulted remains the baptismal profession of most Christian churches.
Location: Constantinople (now Istanbul, Turkey)