Christianity is the world’s largest religion, with approximately 2.4 billion adherents — roughly 31 percent of the global population. It originated in the first century CE as a movement within Second Temple Judaism, centered on the life and death of Jesus of Nazareth in Roman-controlled Judea.
Over the course of two millennia, it has grown from a small group of Jewish followers into a global tradition encompassing more than 45,000 denominations across every inhabited continent.
The following facts about Christianity draw on historical scholarship, demographic research, and textual analysis to present the religion as scholars understand it — its origins, its texts, its growth, and its diversity.
Origins and Founding
Christianity began as a Jewish movement.
Jesus of Nazareth was a Jewish teacher and itinerant preacher in the Galilee and Judea during the first three decades of the first century CE. He was crucified under the Roman prefect Pontius Pilate, most likely around 30 CE.
His earliest followers were Jewish, and they understood his message within the framework of Jewish messianic expectation — the hope that God would intervene to restore Israel.
The movement’s expansion beyond Judaism was driven primarily by Paul of Tarsus, whose missionary journeys through Asia Minor and Greece between roughly 50 and 62 CE established congregations in major Roman cities. Paul’s letters — the earliest surviving Christian documents — predate the Gospels by at least a decade and provide the first written evidence of Christian theology.
The question of who founded Christianity depends on what one means by “founding.” Jesus did not establish a new religion — he operated within Judaism. Paul did not consider himself a founder — he considered himself an apostle. The movement that became Christianity coalesced gradually through the work of many communities across the eastern Mediterranean.
The Texts
The Christian Bible contains 66 books in the Protestant canon, 73 in the Catholic canon (which includes the deuterocanonical books), and 81 in the Ethiopian Orthodox canon.
These texts were composed over approximately 1,100 years, from the earliest portions of the Hebrew Bible (~950 BCE) to the latest books of the New Testament (~120 CE).
The 27 books of the New Testament were composed in koine Greek — the common dialect of the eastern Mediterranean — between roughly 50 and 120 CE. They include four Gospels, one narrative history (Acts), 21 letters (epistles), and one apocalyptic text (Revelation). Most scholars consider the Gospels originally anonymous; the traditional attributions to Matthew, Mark, Luke, and John were added in the second century CE.
The oldest complete manuscript of the New Testament is the Codex Sinaiticus, dating to the mid-fourth century CE — roughly 300 years after the original texts were composed.
For the intervening centuries, scholars rely on earlier fragmentary manuscripts, quotations in the church fathers, and early translations. The textual scholar Bart Ehrman, in Misquoting Jesus (2005), documented how scribal changes accumulated over centuries of hand-copying, producing the thousands of textual variants that modern scholars must navigate.
No original manuscript of any biblical text survives. Every surviving copy is a copy of a copy, separated from the original by generations of hand transmission.
Growth and Global Reach
Christianity’s growth from a handful of Galilean followers to the world’s largest religion followed a distinctive trajectory.
The sociologist Rodney Stark estimated that the movement grew at roughly 40 percent per decade during its first three centuries — a rate consistent with relational growth through personal networks rather than mass public events.
Key milestones in that growth:
- ~30 CE: A few hundred followers in Judea and Galilee
- ~100 CE: An estimated 7,000-10,000 Christians, primarily in the eastern Mediterranean
- ~200 CE: Roughly 200,000 adherents across the Roman Empire
- ~300 CE: An estimated 5-7 million, constituting perhaps 10 percent of the empire’s population
- 313 CE: Constantine’s Edict of Milan legalized Christianity
- 380 CE: Theodosius I declared Nicene Christianity the official state religion of the Roman Empire
By the medieval period, Christianity dominated Europe. Missionary movements, colonial expansion, and immigration carried the faith to the Americas, sub-Saharan Africa, and East Asia over the following centuries.
Today, the Pew Research Center reports the largest Christian populations in the Americas (~804 million), Europe (~565 million), and sub-Saharan Africa (~667 million).
The geographic center of Christianity has shifted 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 Asia. The historian Philip Jenkins, in The Next Christendom (2002), documented this shift as one of the most significant demographic developments in modern religious history.
Denominational Diversity
Christianity is not a single institution. It encompasses three major branches and thousands of smaller traditions.
Roman Catholicism (~1.3 billion adherents) is the largest single Christian body, led by the Pope in Rome. It claims institutional continuity with the apostolic church through an unbroken chain of bishops. The Catholic canon includes 73 books — the 66 of the Protestant canon plus seven deuterocanonical texts.
Eastern Orthodoxy (~220 million adherents) comprises a family of self-governing national churches — Greek Orthodox, Russian Orthodox, Coptic Orthodox, and others — united by shared theology and liturgical tradition but governed independently. The Orthodox churches separated from Rome in the Great Schism of 1054, though the division had been developing for centuries.
Protestantism (~900 million adherents across 45,000+ denominations) originated with the Protestant Reformation in the 16th century. The principle of sola scriptura (the Bible as the sole ultimate authority) meant that disagreements about biblical interpretation produced new denominations — Lutheran, Reformed, Baptist, Methodist, Pentecostal, and thousands more.
Protestantism is not a single tradition but a family of traditions united by shared origins and a set of broad principles.
The Center for the Study of Global Christianity at Gordon-Conwell Theological Seminary counts over 45,000 Christian denominations worldwide. That number includes independent congregations, national variants of international bodies, and small local traditions. The practical diversity within Christianity — in worship style, theological emphasis, ethical teaching, and institutional structure — is far greater than any single denominational label captures.
Key Councils and Doctrinal Milestones
Christianity’s core doctrines were not established all at once. They emerged through centuries of debate, disagreement, and conciliar definition.
The Council of Nicaea (325 CE) addressed whether the Son was co-eternal with the Father (as Athanasius argued) or a created being (as Arius claimed). The council affirmed the Son as homoousios (of one substance) with the Father and produced the Nicene Creed — a statement that remains central to Catholic, Orthodox, and most Protestant worship.
The Council of Chalcedon (451 CE) defined Christ as having two natures — fully divine and fully human — in one person.
This formulation was rejected by several Eastern churches (Coptic, Ethiopian, Armenian, Syriac), producing the Oriental Orthodox communion, which holds to a “miaphysite” Christology (one united nature). This split, predating the Great Schism by six centuries, remains unresolved.
The Council of Trent (1545-1563), convened in response to the Protestant Reformation, formally defined the Catholic biblical canon, reaffirmed doctrines that Protestants had rejected (including transubstantiation, purgatory, and the authority of tradition alongside the Bible), and reformed internal abuses. Trent drew the doctrinal boundary between Catholicism and Protestantism that largely persists today.
Christianity and Its Source Texts
The relationship between Christianity and its texts has evolved over two millennia.
For most of the religion’s history, the majority of Christians could not read the Bible in any language — literacy rates were low, manuscripts were expensive to produce, and in Western Christianity, the Latin Vulgate remained the standard text even as Latin ceased to be a spoken language.
The invention of the printing press (~1440) and the translation of the Bible into vernacular languages (Luther’s German Bible in 1534, the King James Version in 1611) transformed this relationship. For the first time, individual Christians could read the text for themselves — a development that both enabled and accelerated the denominational fragmentation of Protestantism.
Modern biblical scholarship — the application of historical, linguistic, and literary methods to the biblical texts — has produced a detailed understanding of when and how these texts were composed.
The documentary hypothesis, first articulated by Julius Wellhausen in the 1870s, proposed that the first five books of the Bible are woven from multiple sources composed over several centuries. Twentieth- and twenty-first-century scholarship has refined and complicated this picture, but the basic insight — that the biblical texts were composed, edited, and compiled over time by multiple hands — remains foundational.
Understanding these texts in their historical context — who wrote them, when, and why — provides a different way of reading from the devotional tradition. Both approaches engage the same texts. They ask different questions.
If you want to read the biblical texts in the order scholars think they were composed, with historical context before every passage, Uncanon provides the scholarly setting — what was happening, what scholars say, and what to notice as you read.