Why Jesus, Constantine, and 380 AD Don’t Give Us a Simple Answer

When was the Catholic Church founded? It sounds like a simple historical question, but there really isn’t a simple answer.

Catholics traditionally trace the Church directly back to Jesus and Peter in the first century. Others point to Constantine and the Council of Nicaea in 325 AD. Still others argue that the Catholic Church was effectively created in 380 AD, when the emperor Theodosius I issued the Edict of Thessalonica. Each answer points to something important, but none of them adequately explains the history by itself.

If we say the Roman Catholic Church simply appeared around 30 AD, we risk projecting centuries of later institutional development backward onto the earliest followers of Jesus. If we say Constantine created it at Nicaea, we have to explain Christians who were already talking about the “Catholic Church” generations before Constantine was born. And if we choose 380 AD, we encounter Christian communities already using the language of catholicity, governed by bishops, claiming apostolic succession, holding councils, defining orthodoxy and heresy, and looking back on centuries of theological development.

The problem may be the question itself. We are looking for a birthday for something that developed over centuries.

Before There Was a Catholic Church

To understand where the Catholic Church came from, we have to begin with Jesus.

Alfred Loisy famously observed in The Gospel and the Church that Jesus announced the Kingdom, and the Church came. The line is frequently quoted as though Loisy were simply accusing Christianity of abandoning Jesus, but that wasn’t his point. Loisy was defending the idea of development: institutions and doctrines could develop beyond their earliest forms without necessarily representing a betrayal of them.[1]

Whatever we make of Loisy’s theology, the historical observation is useful. The movement surrounding Jesus began within Judaism. Jesus was Jewish. His earliest followers were Jewish. The earliest disputes preserved in Christian sources make sense within that Jewish context.

But the movement changed rapidly, and Paul’s Gentile mission was especially consequential. One of the great controversies of the first Christian generation concerned whether Gentiles who followed Jesus needed to become Jews, including whether men needed to be circumcised. Galatians 2 and Acts 15 preserve accounts of the negotiations surrounding this question that do not line up neatly in every detail.[2] Whatever reconstruction we adopt, the result was enormously important: major Gentile Christian communities did not require complete adherence to the Law of Moses as a condition of membership.

Even here, though, we should resist making the history cleaner than it was. Christianity did not simply cease being Jewish on a particular afternoon in Jerusalem. Jewish followers of Jesus continued to exist, and different Christian communities separated from Jewish communities at different rates and under different circumstances.[3] There was not one clean “parting of the ways.” There were partings.

At the same time, Christian institutions were developing.

When Christians Started Calling the Church “Catholic”

The earliest Christian communities had leaders, but we should be careful about assuming their offices functioned exactly like their later counterparts. The New Testament refers to apostles, prophets, teachers, elders, overseers and deacons. The terminology isn’t always consistent, and episkopos, from which we eventually get “bishop, ”and presbyteros, or elder, do not yet appear everywhere as the clearly separated offices we encounter later.

By the early second century, however, we encounter Ignatius of Antioch. Ignatius was traveling toward Rome to be executed when he wrote a collection of letters to Christian communities along the way. In them, he vigorously defended a particular model of Church government: one bishop presiding over the local Christian community, assisted by presbyters and deacons.[4]

Ignatius did not merely describe bishops; he argued for their authority. His repeated insistence on unity around the bishop actually gives us reason to be cautious about assuming this structure was already universal.

Ignatius also gives us something else. Writing to the Christians at Smyrna, he uses the expression katholikē ekklēsia: the “Catholic Church.” This is the earliest surviving use we possess of the phrase.[5] That does not mean Ignatius invented it, nor did “Catholic Church” necessarily carry everything that “Roman Catholic Church” would eventually mean. Catholic carried the sense of universal or according to the whole.

But the chronology is important. Christians were using the language of the Catholic Church in the early second century, long before Constantine.

The Catholic Church Before Constantine

By the late second century, the picture becomes clearer. Around 180 AD, Irenaeus of Lyons wrote Against Heresies, attacking Christian groups whose teachings he considered false. His problem was straightforward: different Christians claimed to possess the authentic teaching of Jesus and the apostles. How could anyone know who was right?

One of Irenaeus’ answers was apostolic succession. Rather than accepting claims about secret teachings supposedly handed down from Jesus or the apostles, Irenaeus pointed toward the public teaching of churches whose leadership could be traced through earlier generations.[6] Rome received particular attention. Irenaeus described it as the church founded and organized by Peter and Paul and traced its episcopal succession through Linus, Anacletus and Clement and onward to his own time.[7]

Exactly what Irenaeus believed Rome’s special position meant remains debated. The surviving Latin describes Rome in terms commonly translated as “preeminent authority.” Catholic interpreters have understandably seen this as important early evidence for Roman primacy. Other interpretations place greater emphasis on Irenaeus’ immediate argument: apostolic teaching was public and traceable, rather than a secret tradition possessed by his opponents.[8] We do not need to settle that dispute here. Either way, Rome already mattered.

But Irenaeus also exposes a problem with making the early Church too tidy. He wrote five books attacking competing Christian movements precisely because Christians disagreed about which teachings were authentically apostolic. The claim to catholic unity should not be confused with evidence that complete Christian unity already existed. It clearly didn’t.

By the following century, Catholic identity becomes even harder to miss. Around 250 AD, Cyprian, bishop of Carthage, wrote On the Unity of the Catholic Church.[9] We are approximately seventy years before Constantine’s rise and more than a century before the Edict of Thessalonica, and a major Christian bishop is already writing specifically about the unity of the Catholic Church. Whatever Constantine did, he did not invent that.

Cyprian envisioned a universal Church united through its bishops and used strong language about Peter and ecclesiastical unity. But he also demonstrates that the meaning and limits of Roman authority were still contested. During the baptismal controversy of the 250s AD, Cyprian came into direct conflict with Stephen, bishop of Rome, over the validity of baptism performed outside the Catholic Church. Cyprian and the North African bishops maintained a position opposed by Stephen, while Firmilian of Caesarea sided strongly with Cyprian.[10]

Cyprian therefore gives us evidence in both directions. Peter and Rome mattered, but so did the authority Cyprian believed belonged to other bishops. His dispute with Stephen should not be used to pretend Roman primacy didn’t exist, but neither should Cyprian’s Petrine language be treated as though the later doctrine of universal papal jurisdiction already existed in its mature form.

What we are watching is development, including disagreement over what that development meant.

What Constantine Actually Changed

Then came Constantine, and this is where popular history often gets the story badly wrong.

Constantine did not sit down at Nicaea in 325 AD and create Christianity. He did not invent the divinity of Jesus. And he did not manufacture the Catholic Church from an assortment of unrelated Christian communities. The Christian churches Constantine encountered already possessed bishops, sacraments, councils, Christian scriptures, claims of apostolic succession, major centers of authority, theological controversies, and an increasingly developed language of catholicity and orthodoxy.

What Constantine changed was the environment in which all of this operated. Christianity did not become the official religion of the Roman Empire under Constantine, but the shift was still enormous. Imperial hostility gave way to official recognition, money and patronage. Bishops gained new public importance, and Constantine’s support helped transform Christianity into a public institution with a recognized legal presence.[11]

The Council of Nicaea in 325 AD is the clearest example. The controversy that brought the bishops to Nicaea did not originate with Constantine. Constantine became directly involved after taking control of the eastern empire in 324 AD and summoned bishops in an attempt to resolve an already existing Christian dispute.[12]

But Constantine convening the council does not mean Constantine dictated its theology. The bishops were arguing about an existing Christian controversy using Christian scriptures, theological traditions and arguments that predated the council. Nor did Nicaea end the controversy. Arian and related theological positions continued, bishops were deposed and restored, imperial support shifted, and disputes surrounding Nicene theology continued for decades.[13]

That is the real Constantinian change. Constantine did not invent Catholicism. He fundamentally changed the relationship between the Church and the Roman Empire.

What Actually Happened in 380 AD?

On February 27, 380 AD, the emperors Theodosius I, Gratian and Valentinian II issued what became known as Cunctos populos, or the Edict of Thessalonica.[14] This is sometimes presented as the moment when the Catholic Church was created, but Christians had been using the language of the Catholic Church for more than two centuries.

So what did the edict actually do?

The answer is right there in the law. The emperors prescribed a Trinitarian form of Christianity associated with Damasus of Rome and Peter of Alexandria. Its adherents were authorized to bear the title “Catholic Christians,” while those who rejected it were classified as heretics and threatened with imperial punishment.[14]

That is incredibly important, but notice what the edict does not do. It does not create bishops. It does not invent apostolic succession. It does not invent the word Catholic. It does not create the Roman church. It does not invent Nicene Christianity. And it certainly does not create Christianity. Those things already existed.

What changes in 380 AD is the nature of Christianity’s relationship to Roman law. Imperial power was no longer simply recognizing and supporting Christianity. The state was now formally identifying one Christian theological position as Catholic orthodoxy and legally distinguishing its adherents from Christians it classified as heretics.[14]

Even here, though, we should not imagine that one decree instantly transformed religious life throughout the Roman Empire. The fourth century remained a period of substantial religious and theological conflict, and imperial involvement in defining and enforcing Christian orthodoxy continued after 380 AD.[15]

The Edict of Thessalonica is therefore better understood as a major legal and ideological landmark than as the moment the Catholic Church suddenly came into existence. It did not create the Catholic Church. It marked a decisive stage in a much larger transformation, where an already centuries-old Christian tradition claiming catholicity was becoming an imperially defined and legally privileged orthodoxy.

And the Story Still Wasn’t Finished

There is one final problem with making 380 AD the birthday of the Roman Catholic Church: Roman authority continued developing afterward.

Damasus, the bishop of Rome specifically named in the Edict of Thessalonica, was a major promoter of Rome’s preeminence and the “primacy of Peter.” Those claims did not begin with Damasus, but they became increasingly explicit during this period.[16]

The development continued during the fifth century. By the pontificate of Leo I, from 440 to 461 AD, Roman claims concerning Peter and the authority of his successors had become considerably more developed.[17] Rome clearly possessed considerable authority, but the story of what that authority meant, how far it extended, and how it related to councils, emperors and other major sees was not finished.

Leo’s role at the Council of Chalcedon in 451 AD illustrates the complexity. His Tome was enormously influential, but its theology was still examined within the conciliar process and compared with earlier authorities.[18]

We do not need to follow that story through another thousand years to see the point. The Roman Church continued developing after 380 AD.

So When Was the Catholic Church Founded?

So when was the Catholic Church actually founded?

It depends on what we mean by the Catholic Church.

If we mean the movement from which Catholic Christianity ultimately developed, its origins belong to Jesus and his earliest followers in the first century.

If we mean Christians explicitly speaking about the “Catholic Church,” our earliest surviving evidence takes us to Ignatius in the early second century.

If we mean a recognizable episcopal Christian tradition claiming catholicity and apostolic continuity, distinguishing orthodoxy from heresy and attaching particular importance to major apostolic churches such as Rome, we can clearly see it developing during the second and third centuries. Irenaeus and Cyprian alone make it impossible to push all of this forward into the age of Constantine.

If we mean Christianity receiving extraordinary imperial patronage and becoming deeply intertwined with Roman political authority, Constantine represents an enormous turning point. His reign placed Christianity on a fundamentally different institutional footing without making it the official religion of the empire.

If we mean the Roman state explicitly identifying a particular form of Christianity as Catholic orthodoxy and classifying its Christian rivals as heretics, 380 AD is a landmark.

And if we mean the highly centralized Roman Catholic institution familiar from later Western Christianity, its development continued long after Theodosius.

There is no single date because we are really asking several different historical questions and pretending they are one.

None of this, however, tells us whether that development was legitimate. A Catholic can look at this history and see the organic development of the Church established by Christ, with institutions and doctrines becoming more explicit as circumstances demanded them. A critic can look at the same history and argue that institutions created by human beings were gradually invested with divine authority. Simply showing that development occurred does not decide between those positions.

History can test the historical claims made by both sides. It can trace institutions, texts, offices and disputes. It can tell us when particular claims appear in our surviving evidence and how those claims changed over time. What it cannot tell us is whether those developments were guided by God.

But that still leaves us with some conclusions.

The Catholic Church wasn’t created by Theodosius on February 27, 380 AD. Constantine didn’t invent it at Nicaea in 325 AD. But the Roman Catholic Church familiar to us today did not simply appear fully formed in the first century either.

What history gives us instead is development. Sometimes it was gradual. Sometimes it was contested. And sometimes it was accelerated dramatically by political power.

That answer is less convenient than choosing a founder and a date, but it is much closer to what actually happened.

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Endnotes

1. Alfred Loisy, The Gospel and the Church, trans. Christopher Home (London: Isbister & Co., 1903). Loisy’s famous observation about Jesus announcing the Kingdom and the subsequent emergence of the Church belongs to his larger argument about historical development within Christianity, rather than simply asserting that the Church represented an abandonment of Jesus.

2. Galatians 2:1–14; Acts 15:1–35. The accounts are not identical in their presentation, but both preserve evidence for first-century disputes involving Gentiles, circumcision, Jewish law and relations between Jewish and Gentile followers of Jesus.

3. See, among others, James D. G. Dunn, ed., Jews and Christians: The Parting of the Ways, A.D. 70 to 135; Judith M. Lieu, Neither Jew nor Greek? Constructing Early Christianity (London: T&T Clark, 2002); Paula Fredriksen, When Christians Were Jews: The First Generation (New Haven: Yale University Press, 2018); and Annette Yoshiko Reed, Jewish-Christianity and the History of Judaism (Tübingen: Mohr Siebeck, 2018). The older model of one clearly identifiable “parting” has increasingly given way to reconstructions emphasizing multiple boundaries, communities and chronologies.

4. See especially Ignatius of Antioch, Letter to the Magnesians 6–7; Letter to the Trallians 2–3; and Letter to the Smyrnaeans 8. Ignatius repeatedly presents the bishop, presbyters and deacons as a structured leadership within the local church.

5. Ignatius, Letter to the Smyrnaeans 8.2. The passage contains the earliest surviving occurrence of katholikē ekklēsia. This establishes our earliest surviving attestation, not necessarily the invention of the expression by Ignatius.

6. Irenaeus of Lyons, Against Heresies 3.2–3. Irenaeus contrasts alleged secret traditions with publicly accessible apostolic tradition preserved through the churches and their succession of leaders.

7. Irenaeus, Against Heresies 3.3.2–3. He associates the Roman church with Peter and Paul and supplies a succession through Linus, Anacletus, Clement and later bishops.

8. Against Heresies 3.3.2. Interpretation of Irenaeus’s propter potentiorem principalitatem remains disputed. The passage has long figured prominently in discussions of early Roman primacy, while its immediate context concerns Irenaeus’s attempt to demonstrate publicly traceable apostolic teaching against rival claims to hidden tradition. The argument of this article does not depend upon resolving the stronger claims made for the passage.

9. Cyprian of Carthage, On the Unity of the Catholic Church. Cyprian’s discussion of unity, episcopacy and Peter demonstrates a developed concept of the Catholic Church in the middle of the third century.

10. See Cyprian, Epistles 71 and 73 and the conciliar material commonly known as On the Baptism of Heretics or Sententiae Episcoporum. See also Firmilian of Caesarea’s letter preserved among Cyprian’s correspondence. The dispute is especially valuable because it simultaneously demonstrates the importance of the Roman bishop and serious resistance to his position.

11. See The Cambridge History of Christianity, vol. 2, Constantine to c. 600, ed. Augustine Casiday and Frederick W. Norris (Cambridge: Cambridge University Press, 2007), especially its treatment of Constantine, bishops and Christian society. Constantine’s reign fundamentally changed Christianity’s legal, financial and public position without making Christianity the official religion of the Roman Empire.

12. For Constantine’s role in the controversy and convocation of Nicaea, see Lewis Ayres, Nicaea and Its Legacy: An Approach to Fourth-Century Trinitarian Theology (Oxford: Oxford University Press, 2004), together with modern treatments of the Council of Nicaea. The theological controversy preceded Constantine’s intervention.

13. Ayres, Nicaea and Its Legacy. The decades after 325 AD demonstrate that Nicaea was not the instantaneous end of the controversy. Bishops were exiled and restored, formulas competed, emperors intervened, and what later became recognized as Nicene orthodoxy emerged through a much longer fourth-century struggle.

14. Codex Theodosianus 16.1.2, Cunctos populos, issued February 27, 380 AD by Theodosius I, Gratian and Valentinian II. The law identifies the religion associated with Damasus of Rome and Peter of Alexandria, permits its adherents to assume the designation “Catholic Christians,” and classifies dissenters as heretics subject to imperial punishment.

15. Cunctos populos should therefore be situated within the wider development of late Roman religious legislation rather than treated as though one law instantaneously produced a uniformly Nicene Christian empire. Subsequent imperial legislation and continuing Christian controversies themselves demonstrate that the transformation remained incomplete.

16. Samuel J. B. Barnish and Marianne Sághy, “Damasus I, Bishop of Rome, 366–384 CE,” Oxford Classical Dictionary. See also Henry Chadwick, The Church in Ancient Society: From Galilee to Gregory the Great (Oxford: Oxford University Press, 2001). Damasus represents an important stage in increasingly explicit Roman claims concerning Peter and Roman preeminence.

17. On Leo I and the development of Roman/Petrine authority in the fifth century, see Chadwick, The Church in Ancient Society, along with modern scholarship on Leo’s pontificate and ecclesiology.

18. Leo I, Tome to Flavian; Acts of the Council of Chalcedon, 451 AD. Leo’s Tome exercised enormous influence at Chalcedon, while its reception occurred within a conciliar process in which its compatibility with earlier theological authorities was examined.

Selected Sources

Primary Sources

New Testament

Acts of the Apostles, especially Acts 15.

Paul. Epistle to the Galatians, especially Galatians 2.

Early Christian Sources

Cyprian of Carthage. Epistles.

Cyprian of Carthage. On the Unity of the Catholic Church.

Ignatius of Antioch. Letter to the Magnesians.

Ignatius of Antioch. Letter to the Smyrnaeans.

Ignatius of Antioch. Letter to the Trallians.

Irenaeus of Lyons. Against Heresies, especially Book 3.

Leo I. Tome to Flavian.

Council of Nicaea. Nicene Creed and surviving conciliar materials.

Council of Chalcedon. Acts and Definition of Faith.

Theodosius I, Gratian and Valentinian II. Cunctos populos. Codex Theodosianus 16.1.2. 380 AD.

Modern Scholarship

Ayres, Lewis. Nicaea and Its Legacy: An Approach to Fourth-Century Trinitarian Theology. Oxford University Press, 2004.

Barnish, Samuel J. B., and Marianne Sághy. “Damasus I, Bishop of Rome, 366–384 CE.” Oxford Classical Dictionary.

Casiday, Augustine, and Frederick W. Norris, eds. The Cambridge History of Christianity. Vol. 2, Constantine to c. 600. Cambridge University Press, 2007.

Chadwick, Henry. The Church in Ancient Society: From Galilee to Gregory the Great. Oxford University Press, 2001.

Dunn, James D. G., ed. Jews and Christians: The Parting of the Ways, A.D. 70 to 135. Eerdmans.

Fredriksen, Paula. When Christians Were Jews: The First Generation. Yale University Press, 2018.

Lieu, Judith M. Neither Jew nor Greek? Constructing Early Christianity. T&T Clark, 2002.

Loisy, Alfred. The Gospel and the Church. Translated by Christopher Home. Isbister & Co., 1903.

Reed, Annette Yoshiko. Jewish-Christianity and the History of Judaism. Mohr Siebeck, 2018.