How a Jewish Sect Became the World's Largest Religion
The history of Christianity spans roughly 2,000 years, from a Jewish movement in Roman-controlled Judea around 30 CE to the world's largest religion, with about 2.4 billion adherents today. Its arc runs through Paul's mission, Constantine's conversion, the councils that defined orthodoxy, and the schisms of 1054 and 1517.
No single founding moment marks the beginning. No single founder built the institution. And no straight line connects a handful of Galilean followers of an executed preacher to the global tradition that now claims roughly a third of humanity.
What follows is the connective arc — the story that links the world Jesus was born into with the divided, worldwide Christianity of the present. It is deliberately a bird's-eye view. Each turning point along the way has its own deeper history, and this hub links out to those at every stage.
The story moves through seven stages: the Jewish world that produced the movement, the ministry of Jesus and Paul's expansion, three centuries under Roman rule, the councils that fixed doctrine, the thousand-year medieval church, the Reformation-era fracture of the West, and the demographic transformation still unfolding today.
Second Temple Judaism: The World That Produced the Movement
Christianity began inside Second Temple Judaism, the diverse Jewish world of the period between roughly 516 BCE and 70 CE, named for the rebuilt Jerusalem temple that stood at its center.
That world was not religiously uniform. Under Roman occupation, Judaism encompassed competing parties — Pharisees, Sadducees, Essenes, and others — who disagreed about the law, the afterlife, the priesthood, and how Israel should relate to its imperial rulers.
Running through much of it was apocalyptic expectation: the hope that God would intervene in history, overthrow oppression, and restore Israel, often through an anointed figure (a mashiach, or messiah). The Dead Sea Scrolls, composed and copied between roughly 250 BCE and 68 CE, preserve a community steeped in exactly this expectation.
Jesus of Nazareth emerged from this matrix, not from outside it.
He was a Jewish teacher who preached repentance and the imminent arrival of God's kingdom to Jewish audiences in a Jewish idiom. To understand the movement's beginnings is to understand the geography and politics of Roman Judea — the subject explored in depth in where Christianity originated. It also means seeing Christianity as one branch of a shared tradition, a story traced across the Abrahamic religions of Judaism, Christianity, and Islam.
The Jesus Movement and Pauline Expansion (c. 30-70 CE)
The movement's foundational events compressed into a single generation. Jesus was crucified under the Roman prefect Pontius Pilate around 30 CE — an execution that, by every ordinary expectation, should have ended the story.
Instead, his followers' conviction that he had been raised from the dead turned a Galilean reform movement into something that would outgrow its origins.
The earliest surviving Christian texts are not the Gospels. They are the letters of Paul of Tarsus, a Pharisee-educated Jew who never met Jesus during his lifetime and who composed his letters between roughly 50 and 62 CE — at least a decade before the earliest Gospel. Those letters already show a movement arguing over its deepest questions: whether Gentile converts had to keep the Jewish law, what Jesus's death accomplished, and who belonged.
Paul's mission to Gentile communities across the eastern Mediterranean did more than any other single factor to carry the movement beyond its Jewish base.
Then, in 70 CE, Roman legions destroyed the Second Temple in Jerusalem, ending the sacrificial system at the heart of Judaism and reshaping both the synagogue and the church that were growing apart from it. The historian Daniel Boyarin, in Border Lines (2004), argued that this "parting of the ways" was not a clean break but a gradual, contested process that unfolded differently across communities and took centuries to complete. For much of the first century, the line between "Jewish" and "Christian" was one that most people living it would not yet have recognized.
Persecution, Constantine, and Empire (c. 64-380 CE)
Over the next three centuries, a scattered network of house churches became an imperial institution — a transformation covered in depth in early church history, which this hub summarizes rather than repeats.
Growth was steady rather than explosive. The sociologist Rodney Stark, in The Rise of Christianity (1996), estimated the movement expanded at roughly 40 percent per decade across its first three centuries — a rate consistent not with mass conversions but with relational growth through households, kinship networks, and community care during epidemics. By that arithmetic the movement went from a few thousand adherents around 100 CE to perhaps five to seven million by 300 CE.
Persecution punctuated the period but was mostly local and intermittent — flaring under Nero (64 CE), Decius (250 CE), and Diocletian (303-311 CE) rather than running continuously. Martyrdom nonetheless became central to how early Christians understood themselves.
Then the situation reversed entirely.
The Edict of Milan (313 CE) legalized Christianity across the Roman Empire under Constantine. By 380 CE, Emperor Theodosius had declared Nicene Christianity the empire's official religion. A movement that had operated at the margins now shaped Rome's laws, politics, and culture. Much of what we know about these centuries comes from Eusebius of Caesarea, whose Ecclesiastical History (completed around 324 CE) was the first comprehensive account of the church's first 300 years.
Councils and Creeds: Defining Orthodoxy (325-451 CE)
Once Christianity had imperial backing, its internal disagreements became matters of state, and a series of ecumenical councils set out to define what Christians were required to believe.
The Council of Nicaea (325 CE) was the first. It confronted the teaching of Arius, a priest in Alexandria who held that the Son was a created being subordinate to the Father. The council's answer — that the Son was homoousios (of one substance) with the Father — produced the first version of the Nicene Creed. The interplay between this council and the biblical texts is examined in the Council of Nicaea and the Bible.
Nicaea did not settle the matter. The doctrine of the Trinity was refined across the rest of the fourth century, culminating in the First Council of Constantinople (381 CE), which affirmed the divinity of the Holy Spirit and produced the creed most churches still recite. In How Jesus Became God (2014), Bart D. Ehrman emphasizes that this fully developed trinitarian formula postdates the New Testament and uses philosophical categories its authors never employed.
A less familiar fracture opened next.
The Council of Chalcedon (451 CE) defined Christ as one person in two natures, fully divine and fully human. Several Eastern churches — Coptic, Ethiopian, Armenian, and Syriac among them — rejected that formula in favor of a "miaphysite" understanding (one united nature), forming what became the Oriental Orthodox communion. That division predates the more famous East-West schism by more than six centuries, and it has never been formally healed — a reminder that Christianity was fracturing long before the Middle Ages.
The Medieval Church (c. 500-1500 CE)
For the thousand years between the fall of Rome and the Reformation, the church was the central institution of European life — preserving literacy, shaping law, and carrying Christianity into lands the empire had never converted.
Monasticism organized much of that work. Around 529 CE, Benedict of Nursia founded the monastery at Monte Cassino and composed his Rule, a practical code balancing prayer, labor, and study that became the template for Western monastic life. Benedictine houses copied manuscripts, cleared and farmed land, and anchored their communities — for centuries they were Europe's schools, libraries, and hospitals at once.
Missionaries carried the faith north and east, beyond the old imperial frontier. Patrick in fifth-century Ireland, Augustine of Canterbury sent to the English in 597 CE, and Boniface among the Germanic peoples in the eighth century reached populations Rome had never ruled. By roughly 1000 CE most of Europe, from Scandinavia to the Slavic lands, had been Christianized — often through the conversion of a king whose subjects followed.
The high medieval centuries brought both militarized religion and systematic thought. Beginning in 1095 CE, when Pope Urban II called the First Crusade, waves of armed pilgrimage toward the Holy Land continued until the fall of Acre in 1291 — reshaping relations among Christianity, Judaism, and Islam, often violently. In the new universities, meanwhile, scholasticism worked to reconcile Christian doctrine with classical philosophy; Thomas Aquinas, in his Summa Theologiae (1265-1274), synthesized Aristotle with Christian theology so thoroughly that his framework still anchors much Catholic teaching. Even so, the unity of that church was already straining — the first of its two great splits fell within this very period.
Two Great Fractures: 1054 and 1517
The second Christian millennium is defined by two divisions that produced the major branches recognizable today.
The first was the Great Schism of 1054, which formalized the split between the Latin-speaking West and the Greek-speaking East. Differences in language, liturgy, theology (especially the filioque clause added to the creed in the West), and the authority of the pope had been accumulating for centuries. When Cardinal Humbert laid a bull of excommunication on the altar of the Hagia Sophia, he ratified a division most ordinary believers had already been living. The result was Roman Catholicism and Eastern Orthodoxy, each claiming unbroken continuity with the apostolic church — a divergence traced in Catholic vs Protestant.
The second fracture split the West itself.
The Protestant Reformation began in 1517, when Martin Luther circulated his 95 Theses against the sale of indulgences. His challenge quickly widened into two principles that reframed the whole tradition: sola scriptura (the Bible alone as final authority) and sola fide (justification by faith alone). Within a generation the movement had fragmented further — the magisterial reform of Luther, Zwingli, and Calvin; the radical Anabaptists; the politically driven English Reformation under Henry VIII.
The Catholic Church answered with the Council of Trent (1545-1563), which reaffirmed Catholic doctrine point by point and formally fixed its biblical canon, including the deuterocanonical books that Protestants set apart. The historian Diarmaid MacCulloch, in Christianity: The First Three Thousand Years (2009), traced how these sixteenth-century arguments over authority and scripture helped shape the wider political modernity of the West.
Global Christianity Today: 2.4 Billion and Shifting South
Christianity is now the world's largest religion, with approximately 2.4 billion adherents — roughly 31 percent of the global population, according to the Pew Research Center.
It is also the most internally divided. The Center for the Study of Global Christianity at Gordon-Conwell Theological Seminary counts more than 45,000 distinct Christian denominations worldwide, a figure that includes major bodies, national variants, and small independent congregations alike. Three broad branches account for most adherents: Roman Catholicism (about 1.3 billion), Protestantism (about 900 million across those tens of thousands of denominations), and Eastern Orthodoxy (about 220 million).
Much of the modern reshaping runs through mission and revival. The Protestant and Catholic missionary expansion of the eighteenth and nineteenth centuries planted churches across Africa, Asia, and the Pacific, and in 1906 CE the Azusa Street Revival in Los Angeles sparked Pentecostalism — a movement centered on direct experience of the Holy Spirit that grew, within a century, into one of the fastest-expanding forms of Christianity, most of all across the Global South.
The geographic center of the faith has moved dramatically.
In 1900, roughly 80 percent of the world's Christians lived in Europe and North America. By 2020, the majority lived in the Global South — Latin America, sub-Saharan Africa, and parts of Asia. The historian Philip Jenkins, in The Next Christendom (2002), documented this shift as one of the most significant developments in modern religious history: the tradition's demographic heartland is no longer where its institutional centers were built.
The texts at the root of all this diversity were themselves composed over roughly 1,100 years, in Hebrew, Aramaic, and Greek, by dozens of authors. How that library was written, edited, and assembled is the subject of the history of the Bible, and the question of authorship is explored in who wrote the Bible.
Two Thousand Years at a Glance
The milestones below mark the turning points along the arc — each one reshaping Christianity's identity, structure, or boundaries, even as the fuller story unfolded gradually between them.
| Date | Event |
|---|---|
| c. 30 CE | Crucifixion of Jesus of Nazareth under Pontius Pilate in Roman Judea |
| c. 50-62 CE | Paul composes his letters — the earliest surviving Christian texts |
| 70 CE | Roman destruction of the Second Temple in Jerusalem |
| 313 CE | Edict of Milan — Constantine legalizes Christianity across the empire |
| 325 CE | Council of Nicaea — the first ecumenical council and the Nicene Creed |
| 381 CE | Council of Constantinople affirms the Spirit's divinity |
| 451 CE | Council of Chalcedon — the Oriental Orthodox churches diverge |
| 529 CE | Benedict of Nursia founds Monte Cassino, shaping Western monasticism |
| 1054 CE | Great Schism — the Latin West and Greek East formally split |
| 1095-1291 CE | The Crusades — armed pilgrimage to the Holy Land |
| 1517 CE | Martin Luther posts the 95 Theses — the Protestant Reformation begins |
| 1545-1563 CE | Council of Trent defines the Catholic response to the Reformation |
| 1906 CE | Azusa Street Revival sparks global Pentecostalism |
The first century compressed the movement's founding events into a few decades. The next three fixed its institutions and its creeds. The thousand years that followed made the church the central institution of European life, even as the two great fractures — East from West in 1054, Protestant from Catholic in 1517 — produced the branches we know. And the last century relocated the faith's center of gravity to the Global South.
Every stage of this arc traces back to a library of ancient texts. Uncanon presents those texts in the order scholars think they were composed, with the historical context set before each passage — who wrote it, and what was happening in the world that shaped it.