Christianity is centered upon the life and teachings of Jesus of Nazareth, as chronicled in the Gospels and elaborated in the broader texts of the New Testament. It is the world's largest religion, with approximately 2.4 billion adherents across a vast array of denominations and cultural expressions, from Roman Catholicism and Eastern Orthodoxy to the thousands of Protestant churches established since the sixteenth-century Reformation.
The Historical Jesus
Jesus of Nazareth is believed to have been born around 4 BCE in Judea, then a province of the Roman Empire, during the reign of Herod the Great. The Gospel accounts place his birth in Bethlehem, though he grew up in Nazareth in Galilee — hence the epithet by which he was widely known. He began his public ministry around 30 CE, during the reign of the Emperor Tiberius Caesar, preaching a message of the coming Kingdom of God, repentance, and a radical ethic of love, forgiveness, and care for the poor and marginalised.
Jesus gathered a close group of disciples and attracted large crowds, performing what the Gospel accounts describe as healings and other miraculous acts. His ministry lasted perhaps two to three years before his arrest in Jerusalem, brought about at the instigation of the Jewish religious authorities and carried out under the Roman prefect Pontius Pilate. He was executed by crucifixion, the standard Roman punishment for political insurgency. The Gospels agree that on the third day after his death, his tomb was found empty, and that he appeared to his disciples risen — an event understood by Christian faith as the resurrection, the definitive sign of his divine identity and the basis of Christian hope for salvation.
The title "Christ" derives from the Greek Christos, itself a translation of the Hebrew Mashiach — Messiah, meaning "anointed one." The Latin rendering of his Hebrew name Yeshua would be Josua or Joshua. The compound "Jesus Christ" is therefore less a personal name than a confessional statement: Jesus the Messiah.
Formation of the Christian Canon
The earliest Christian writings are not the Gospels but the Epistles of Saul of Tarsus — known after his conversion as Paul — composed in the 50s CE, two decades before the first Gospel (generally dated to Mark, c. 70 CE). Paul's letters to communities in Corinth, Galatia, Thessalonica, Rome, and elsewhere address theological questions that arose in the first generation of the new movement: the relationship of Jewish law to Christian practice, the meaning of the resurrection, the nature of the Church, and the expectation of Christ's imminent return.
The process of establishing which texts were authoritative (canonical) extended over several centuries of debate. Diverse communities held diverse texts in varying degrees of esteem. It took the consolidating will of the Roman Emperor Constantine — who had converted to Christianity and seen in it a unifying force for the empire — to convene the Council of Nicaea in 325 CE. This council, attended by Christian bishops from across the empire, addressed most urgently the Arian controversy (whether Christ was fully divine or a created being), formulating the Nicene Creed as the orthodox statement of Trinitarian faith. Questions of the complete biblical canon were not finally settled at Nicaea, but continued through subsequent councils.
The New Testament as now received by all major Christian traditions comprises 27 books: four Gospels (Matthew, Mark, Luke, John), the Acts of the Apostles, 21 Epistles (including 13 attributed to Paul), and the Book of Revelation. The Old Testament, accepted as authoritative by all Christian traditions, corresponds to the Hebrew Bible (Tanakh), though Catholic and Orthodox traditions include additional texts (the Deuterocanonical or Apocryphal books) not found in the Protestant canon.
Core Doctrines
Central to orthodox Christian theology is the doctrine of the Trinity: the claim that the one God exists in three persons — Father, Son, and Holy Spirit — distinct in relation but one in substance (homoousios, of the same essence, in the Nicene formulation). This was the doctrine at stake in the Arian controversy. Related is the doctrine of the Incarnation: the belief that the second person of the Trinity, the eternal Son of God, took on full human nature in the person of Jesus of Nazareth — fully God and fully human, in the formula of the Council of Chalcedon (451 CE).
The doctrine of Atonement addresses the salvific meaning of Christ's death: his crucifixion is understood as a sacrifice that atones for the sin of humanity since Adam, making possible reconciliation between humanity and God. How exactly this atonement works has been the subject of extensive theological debate across the tradition — ranging from Anselmian satisfaction theory to moral influence theories to Christus Victor models. Christian ethics is grounded in the dual commandment attributed to Jesus: love of God and love of neighbour, with the parable of the Good Samaritan providing its most radical extension.
Major Traditions
Roman Catholicism is the largest single Christian denomination, with approximately 1.3 billion adherents, centered on papal authority and a sacramental theology. Eastern Orthodoxy — the churches of Greece, Russia, Serbia, and others — split from Rome in the Great Schism of 1054 CE, preserving a distinctive liturgical and theological tradition. Protestantism, originating with the Reformation movements of the sixteenth century led by Martin Luther, John Calvin, and others, encompasses thousands of denominations united chiefly by the principles of scripture alone (sola scriptura) and faith alone (sola fide) as the basis for salvation.
For authoritative reference, the Encyclopaedia Britannica entry on Christianity is comprehensive and scholarly. Primary texts are accessible at sacred-texts.com's Christianity section. The Wikipedia article on Christianity provides extensive further reading. For the historical Jesus, the Stanford Encyclopedia of Philosophy entry treats the philosophical and historical questions rigorously.
On this site, see also Judaism — the tradition from which Christianity emerged — and Islam, the third Abrahamic religion which regards Jesus as a major prophet.