Written by David Caldwell · 15 November 2025

The Road to Nicaea: How Apostolic Succession Created Bishops, Canons and the First Popes

When people imagine “the early Church,” they usually import the finished product back into the first century: bishops in mitres, a pope in Rome, the Nicene Creed pinned to every vestry noticeboard, and a neat New Testament sitting on the altar.

That world did not exist when the first Christians were arguing in Jerusalem, or when Roman officials like Pliny were scratching their heads about this strange new superstition. For at least a century after the death of Jesus, Christianity is not yet a church in the institutional sense. It is a movement: diffuse, experimental, and far less tidy than later memory would like.

This article traces how that movement hardened into hierarchy. It runs from the martyrdom of Stephen to the Council of Nicaea, and along the way it introduces some of the texts and figures that shaped the road: 1 Clement, Ignatius of Antioch, the Epistle of Barnabas, the Shepherd of Hermas, the great 4th-5th century codices, Irenaeus, and the awkward figure of Marcion of Sinope, who forced the church to decide what “Scripture” even was.

Beneath all this lies a simple question: how did “apostolic succession” - the claim to hand on the apostles’ teaching - become a concrete system of bishops, canons and, eventually, papal primacy?

1. Stephen’s death and a scattered movement

The canonical story begins in Jerusalem. In the Acts of the Apostles, Stephen is hauled before the council, accused of speaking against the Temple and the Law. He responds with a long retelling of Israel’s history, climaxing in a blistering accusation: “you always resist the Holy Spirit” and have now betrayed and murdered “the Righteous One.” He is dragged out of the city and stoned.

Acts then adds a line that reads like a throwaway but is crucial for everything that follows:

“On that day a great persecution broke out against the church in Jerusalem, and all except the apostles were scattered throughout Judea and Samaria.” (Acts 8:1)

However we judge Luke’s exact history, the basic pattern is plausible. The Jesus movement begins as a Jewish sect centred on the Temple. Conflict with the authorities - both Temple and synagogue - pushes many of its Greek-speaking members outward, into Samaria, Syria and the wider Roman world. The apostles themselves, Luke says, remain in Jerusalem, at least for a while, as a kind of symbolic core.

That scattering matters. It means that when the Jewish War breaks out in 66 CE and the Temple finally falls in 70, a sizeable chunk of the movement is already living as outsiders to the city that once defined their worship. Later Christian texts talk about the destruction of the Temple with a mixture of grief, vindication and cool distance that feels more like commentary from the margins than lament from the ruins.

At this early stage, Rome is not yet in the business of organising persecutions. In the famous letter of Pliny the Younger to the emperor Trajan (c. 112), the governor of Bithynia describes how he interrogates people accused of being Christians. He is not hunting them; he simply does not know what to do. If they deny the name, sacrifice to the emperor’s image and curse Christ, he lets them go. If they stubbornly persist, he has them executed. Christianity appears here as an illicit cult defined by its obstinacy, not as a recognised “church” with bishops and canon law.

Internally, though, the movement already faces a problem that will only grow sharper: who has the authority to teach and to lead?

2. Before there was a New Testament

From about 30 to 70 CE, Christian life is governed far more by tradition and practice than by books. Communities gather to break bread, share news, recall Jesus’ sayings and deeds, and read the Jewish Scriptures in the light of his story. Letters by missionaries such as Paul begin to circulate. Oral memory and written fragments feed one another.

What does not yet exist is anything approaching a bound New Testament. There is no official list of Christian scriptures. Some communities may have early written collections of Jesus’ sayings; others rely entirely on the vivid memories of apostles, prophets, and local teachers.

Later Victorian historians, like Edward Burton in his “History of the Christian Church in the First Century,” liked to describe this period as a time when Jesus left no written constitution but did set apart a group - the apostles - who, by preaching and appointing successors, gave the movement its first skeleton. Burton looks at the appointment of “the seven” in Acts 6 - men chosen to oversee the daily distribution to the poor - as the first division of labour: the apostles retain the ministry of teaching and prayer; the new ministers handle practical care.

Whether or not we follow Burton’s churchmanship, his basic observation stands: structure follows pressure. You don’t invent new offices in abstraction. You invent them because you are overwhelmed.

As the Jesus movement spreads, leadership necessarily becomes more layered. There are apostles and missionaries, prophets who speak in the name of the Spirit, elders (presbyteroi) who keep local communities in order, and deacons who serve the poor. The vocabulary is fluid; the roles overlap. What binds them together is not a common constitution but a shared conviction that the apostles had authority from Christ, and that this authority can be in some sense passed on.

We see that conviction taking clearer shape in our first window into intra-Christian conflict: a long letter from Rome to Corinth.

3. 1 Clement: succession in embryo

Around the mid-90s, a crisis breaks out in the church at Corinth: certain presbyters (elders) have been removed from office. The church of Rome intervenes, sending a densely argued letter that later tradition attributes to Clement, a leading figure in the Roman community.

The document known as 1 Clement is not scripture in any modern Bible, but it is our earliest substantial Christian writing outside the New Testament, and for the question of church order it is dynamite.

Clement insists that the apostles, foreseeing disputes, appointed leaders and gave instructions that, when these leaders died, others approved men should succeed to their ministry. He connects this with Old Testament patterns - the orderly succession of high priests, Levites and temple officials - and with Christ’s own commission. The presbyters who were unjustly removed should, he says, be restored, because deposing them without cause violates this divinely established succession.

Two points stand out.

First, Clement freely appeals to the Hebrew Scriptures as authoritative and occasionally echoes Jesus’ words, but he never once cites “Matthew,” “Mark,” “Luke” or “John.” If written Gospels existed in Corinth or Rome at this date, they are simply not part of his argumentative toolkit. That does not prove they did not exist, but it underlines how non-canonical the early picture still is. Canon, in the strict sense, lies in the future.

Second, the letter is sent in the name of “the Church of God which sojourns at Rome”, not of “Pope Clement.” Rome clearly feels able to admonish another church, and Corinth is expected to listen, but the voice is corporate and fraternal, not yet that of a solitary pontiff issuing decrees.

Here, then, we see apostolic succession in embryo: the idea that particular ministries are legitimate because they stand in an ordered human chain back to the apostles. We also see Rome beginning to act as a moral reference point. But the structural picture is still a college of presbyters, not a single monarch.

4. Ignatius: the invention of “the bishop”

A few decades later, the tone changes dramatically.

On his way to martyrdom in Rome, Ignatius of Antioch writes a series of letters to churches in Asia Minor (c. 110-115). For Ignatius, the central mark of a properly ordered church is clear and uncompromising: one bishop in each city.

In letter after letter, he urges his readers:

• to do nothing without the bishop,
• to regard the presbytery as the council of the bishop,
• and to honour the deacons as the bishop’s trusted ministers.

Where 1 Clement spoke of “bishops and deacons” in ways that blurred into “presbyters”, Ignatius sharpens the triangle: bishop at the top, presbyters beneath, deacons assisting.

This “monarchical bishop” is the great administrative invention of the second century. In Ignatius’ eyes, he embodies unity; to gather around the bishop is to gather around Christ; to separate from the bishop is to fracture the church.

It is crucial, however, to notice where Ignatius does not apply this model. In his Letter to the Romans - a deferential, almost nervous note asking the Roman Christians not to interfere with his martyrdom - he praises the Roman church as “presiding in love” but never once names a bishop of Rome or tells the Romans to obey him. The monarchical episcopate appears entrenched in Asia Minor; Rome seems to lag behind, still led by a group of presiding presbyters.

Ignatius gives us a church that is structurally more familiar: one bishop per city, presbyters and deacons beneath him, and the beginnings of regional relationships between bishops. He also gives us the first intense rhetoric of loyalty to the bishop as the guarantor of true teaching and sacramental validity - the pastoral face of what will become apostolic succession.

5. Barnabas and the world before a Gospel canon

While leadership structures are stiffening, the textual landscape remains remarkably fluid. Two writings that sit just outside the later New Testament give us a feel for this world.

The Epistle of Barnabas is a fierce little treatise, probably written somewhere between 70 and 130 CE, often linked to Alexandria. It is not by the Barnabas of Acts; the name is pseudonymous. Its passion is to prove that Christians, not ethnic Israel, are the true heirs of God’s covenant. To that end, it reads the Old Testament in a wild allegorical key, turning food laws and rituals into symbols of moral purity and faith.

What Barnabas almost entirely lacks is dependence on written Gospels. It never names the evangelists. It contains sayings introduced as “the Lord says” or “the Son of God says” that do not match any canonical Gospel wording. There is one possible allusion to “Many are called, but few are chosen,” but even here scholars disagree whether the author is quoting Matthew or drawing on a proverbial saying that Matthew also used. Either way, Barnabas offers no firm evidence that its author has read any of our four Gospels as texts, let alone that he treats them as Scripture.

This silence fascinated 19th-century freethinkers. Writers in papers like the National Reformer gleefully pointed out that prominent Anglican scholars had conceded the point: from Barnabas we cannot prove that he had read any part of what we now call the New Testament. For those arguing that the four Gospels were already fixed and revered immediately after 70 CE, Barnabas is an awkward witness.

But whatever we do with that polemic, Barnabas certainly shows us a Christianity still living almost entirely from the Jewish Scriptures, read through a Christological lens, and not particularly interested in written narratives of Jesus’ life.

6. Hermas: Roman order without Nicene dogma

If Barnabas speaks with a sharp, Alexandrian tone, the Shepherd of Hermas gives us a Roman voice.

Hermas is a sprawling, allegorical work: visions, commandments, and parables, probably written in the mid-2nd century and set in Rome. Ancient sources claim that its author was the brother of Pius I, a Roman bishop. Whether or not that detail is accurate, the book clearly comes from within the Roman community.

Hermas is obsessed with two things:

• Repentance: is there forgiveness for serious sins committed after baptism? If so, how many times? How urgent is conversion?
• The Church: pictured as a tower under construction, into which stones (believers) are fitted, removed, cleansed and refitted.

The book presupposes a structured church with bishops, presbyters and deacons, but it has little interest in naming individuals or describing chains of office. Its world is not yet that of Nicene theology. Its language about Christ and the Spirit is strange enough that later readers suspected it of teaching that Jesus was “adopted” as Son; recent scholarship has shown it to be drawing on Jewish traditions where “spirit” can mean a heavenly, even angelic figure, but either way it does not use the later Trinitarian formulas.

What matters here is that for early Roman Christians, questions of discipline and repentance loom larger than metaphysical precision. The church is a moral community under shepherds, not yet a doctrinal tribunal.

The status of Hermas in early Christianity underlines how fuzzy the boundaries still were. Writers like Irenaeus and Origen cited it approvingly; others denied it canonical rank. In the 4th century, the great biblical manuscript Codex Sinaiticus copies it immediately after the Book of Revelation. It is not counted among the 27 books of the New Testament, but it sits right next to them, in the same codex, as a text worth preserving and reading.

Sinaiticus also includes, just before Hermas, the Epistle of Barnabas. Its sister manuscript, Codex Alexandrinus, copies 1 and 2 Clement after Revelation. These codices are not just piles of parchment; their tables of contents are theological statements. They tell us that for some late antique Christians, these fringe texts were close enough to scripture to share a binding with it, while not secure enough to be universally acknowledged as inspired.

7. Marcion and the shock of the “wrong” canon

So far, the story of structure and scripture has been mostly gentle drift: apostles, elders, bishops; letters and gospels gradually accumulating prestige. In the mid-2nd century, a single figure forces the Church to think much more aggressively about what belongs and what does not: Marcion of Sinope.

Marcion was a wealthy shipowner from Pontus who came to Rome around the 140s. His theology was radical. He drew a sharp line between the God of the Jewish Scriptures, whom he saw as a lesser, legalistic creator deity, and the Father of Jesus, a higher, previously unknown God of grace. The Old Testament God, in Marcion’s view, is just; the Father of Jesus is good. The two cannot be the same.

To support this, Marcion produced, in effect, the first known Christian canon. He accepted:

• a version of the Gospel of Luke (heavily edited to remove what he saw as Judaizing elements),
• and ten letters of Paul,

and rejected the Old Testament entirely.

For Marcion, the Law and the Prophets were not Christian scripture at all. The church had, in his notorious phrase, falsified the gospel by mixing it with Judaism.

Marcion’s critics - notably Irenaeus of Lyon and Tertullian - attacked him as a mutilator of the gospel and an enemy of the Creator. But in fighting him, they were forced to articulate something they had not previously needed to state clearly: that there is such a thing as a “New Testament” and that it stands in some relation, however complex, to the Jewish Scriptures.

Behind their polemic lies an uncomfortable truth: Marcion did not invent the question; he revealed it. Early Christian preaching had already put enormous weight on Paul’s letters and on certain gospel traditions; Christian assemblies already read “memoirs of the apostles” in their meetings. But no one had yet fixed, in writing, which texts belonged and how they related to the old.

Marcion’s “wrong” canon provoked the Church into constructing a “right” one. Over the next century, lists of accepted books emerge. The fourfold Gospel - Matthew, Mark, Luke, John - becomes the norm. The Old Testament is retained, but now it is reread strictly through Christ. Barnabas’ anti-Jewish polemic suddenly looks less eccentric; Hermas’ interest in repentance finds a home in emerging penitential practices; Clement’s appeal to succession bolsters bishops who claim to guard both Testaments against mutilation.

8. Irenaeus and the weaponisation of succession

No figure stands more clearly at the crossroads of hierarchy and canon than Irenaeus, writing around 180 CE.

Facing a bewildering range of Gnostic teachers who claimed secret revelations and alternative gospels, Irenaeus deploys a double strategy.

First, he insists on the fourfold Gospel. Just as there are four winds and four corners of the earth, he says, so there must be four and only four authoritative Gospels: Matthew, Mark, Luke and John. These are the public, apostolic accounts read everywhere. All other “gospels” are inventions of heretics.

Second, he pivots from texts to people. In book 3 of Against Heresies, he lays out lists of bishops in the major churches, beginning with Rome. The apostles, he says, appointed bishops and handed on their teaching to them; these bishops were succeeded in ordered lines down to his own day. If you want to know the apostolic faith, look at what these churches teach. Their succession lists are not just historical curiosities; they are arguments.

Here, apostolic succession ceases to be a vague claim about continuity and becomes a weapon. Irenaeus uses it to exclude. His own theology, echoed by the bishops who stand in the line from Peter and Paul, is apostolic; the wild cosmologies of the Gnostics, taught outside this succession, are not.

Rome, in this scheme, plays a special role. Irenaeus calls it “very great, very ancient, known to all” and says that “every church must agree with this church” because of its pre-eminent authority. Modern historians have pointed out that the early part of his Roman succession list is almost certainly reconstructed backwards and that Rome in the 1st century was probably led by a group of presbyter-bishops rather than a single monarchical figure. But again, what matters is how the list functions now: as the backbone of Roman primacy.

By the end of the 2nd century, then, three things have come together:

• monarchical bishops as normal in major cities,
• an emerging New Testament canon centred on the four Gospels and Paul,
• and the use of succession lists - especially Rome’s - as proof of orthodoxy.

The road to Nicaea is now fully open.

9. From bishops to patriarchs to popes

When we ask “when did the first pope appear?”, we are really asking when the bishop of Rome became something more than one patriarch among several.

If we mean “a single bishop of Rome” in the Ignatian sense, we probably have to wait until at least the mid-2nd century, when figures like Anicetus and Soter appear in our sources as distinct leaders. Earlier names on the Roman list may preserve genuine memories, but the structure is hazier.

If we mean “a bishop whose jurisdiction extends over the whole Church,” then we are talking about a much later, incremental process.

Already in the 2nd and 3rd centuries, Roman bishops intervene in disputes beyond their own region, for example over the date of Easter or the rebaptism of heretics. Sometimes other bishops accept their leadership; sometimes they push back. Councils give Rome a primacy of honour, but they also recognise the authority of Alexandria, Antioch and, later, Constantinople.

What makes the bishop of Rome different in the long run is not a single founding document but a convergence of narratives:

• the story (however embroidered) that Peter and Paul both died in Rome and that Peter held its episcopal see,
• Irenaeus’ enumeration of Roman bishops as a model succession,
• the sheer political weight of the imperial capital,
• and centuries of practice in which Rome becomes, in effect, a court of appeal.

By the time we reach the great councils of the 4th and 5th centuries, the Roman bishop is clearly “first among equals” in honour. The theological and juridical claims that will later be bundled together as “papal supremacy” develop on top of this foundation. They are not visible in Stephen’s Jerusalem, in Clement’s Rome, or even in Hermas’ tower - but the lines of force are running that way.

10. Nicaea: bishops on parade

The Council of Nicaea in 325 is often remembered as a purely doctrinal event: the moment when the church declared the Son to be “of one substance with the Father” and condemned Arius’ claim that “there was when he was not.”

It is that, but it is also an extraordinary snapshot of the episcopal system in action.

The assembled figures are almost all bishops in the Ignatian sense, some with dramatic backstories: confessors who have suffered in the last persecutions, new men fresh from imperial favour, grey-haired theologians, practical administrators. Many come from sees that have by now accumulated serious prestige: Alexandria, Antioch, Rome’s legates, and a new rising power - Constantinople.

The emperor Constantine presides, anxious for unity. The bishop’s debate, form factions, draft and redraft formulas, and finally adopt a creed that insists the Son is “God from God, Light from Light, true God from true God, begotten not made, of one substance with the Father.” They also issue canons regulating church discipline, acknowledging regional structures and confirming the privileges of the big sees.

Whatever else Nicaea is, it is the public coming-of-age of the bishop as a political and theological actor. The apostles are long dead; prophets like those implied in the Didache are no longer on centre stage. The guardians of doctrine are bishops meeting in council. The “road to Nicaea” is essentially the story of how that became true.

11. The strange texts in the margins

If we only read the story forwards from Nicaea and backwards from Vatican I, it is easy to treat bishops, creeds and popes as the obvious, even inevitable, forms of Christian leadership. It then becomes tempting to project them wholesale into the 1st century and read every early dispute as if a hidden Catholic Church were waiting to emerge.

The texts we have touched on - 1 Clement, Ignatius, Barnabas, Hermas, Marcion’s challenge, the great codices - resist that flattening.

1 Clement shows a Roman church anxious about order and succession, but still speaking in the voice of a community, not yet that of a papal monarch. Ignatius reveals how radical the idea of a single bishop per city once was, and how unevenly it spread. Barnabas and Hermas inhabit a world where the Old Testament still dominates Christian argument, where the Gospels are not yet a fixed canon, and where questions of repentance and allegory matter more than ontological precision.

Marcion, in his turbulent way, forces the church to decide that there is such a thing as a New Testament and that it must be read with, not against, the Old. Irenaeus, reacting to both Gnostics and Marcionites, turns lists of bishops into proof of apostolicity and makes Rome a touchstone of orthodoxy.

The scribes who copied Codex Sinaiticus and Alexandrinus, binding Barnabas, Hermas and Clement at the back of their big Bibles, show how long the edges of the canon remained fuzzy and how important these “almost-scriptures” remained for Christian self-understanding.

By the time Athanasius of Alexandria and his allies are battling Arius over the eternal Son at Nicaea and beyond, the church has acquired bishops, canons, and patriarchs. The logic of apostolic succession has been institutionalised in a network of offices. Popes, in the strong sense, are still to come, but their roots are already tangled deeply in these earlier developments.