Christianity is the world's largest religion, built around a single claim: that Jesus of Nazareth, a first-century Palestinian Jew, was and is the Christ — the Anointed One promised by Israel's God, and God himself made human. As Encyclopædia Britannica's overview records, what began as a small Jewish movement became, over two millennia, the professed faith of roughly a third of humanity. This collection gathers the index's writing and teaching on Christianity into one reading — neutral but attentive, tracing what the tradition says about itself.
The claim at the centre
The New Testament scholar N. T. Wright frames the faith through three words: belonging, believing, behaving. To be a Christian, in his account, is to belong to a family that cuts across ethnic and social lines, to believe in the God revealed in Jesus, and to live the way Jesus taught — the first followers called their movement simply The Way. C. S. Lewis's *Mere Christianity* attempts something similar at the level of doctrine, defending the beliefs common to the major branches rather than any one of them. Distinctive to Christianity is its picture of God as one being in three persons — Father, Son, and Holy Spirit. The source text behind all of it is the Bible, the scripture the tradition reads as the record of God's dealings with the world.
How it began — and how it spread
Bart D. Ehrman takes up the historical question: how did a handful of followers around 30 CE become the religion of the Roman emperor within three centuries? His answer sets aside the familiar stories — that paganism had collapsed, or that Christianity was self-evidently superior — in favour of the exponential arithmetic of personal conversion and the faith's unusual demand for exclusive worship. That early movement was never monolithic. Elaine Pagels's *The Gnostic Gospels*, drawing on the Nag Hammadi manuscripts, recovers the rival early Christianities that the emerging church set aside as it defined its canon and creed.
The books that defined the faith
Much of Christianity's literature is the record of people reasoning their way toward or through belief. Blaise Pascal's *Pensées* gathers the fragments of an unfinished defence of the faith, including his famous wager; Lewis's *The Screwtape Letters* inverts the genre, letting a senior devil instruct a junior tempter and so exposing ordinary self-deception by reflection. John Bunyan's *The Pilgrim's Progress* renders the Christian life as an allegorical journey, while Dietrich Bonhoeffer's *The Cost of Discipleship* sharpens its demand, attacking what he called "cheap grace" from inside a church compromising with power. Leo Tolstoy arrives from the far edge: A Confession narrates the crisis of meaning that drove him back to the Gospels, and *The Kingdom of God Is Within You* reads the Sermon on the Mount as a literal call to nonviolence — a reading that would later shape Gandhi.
The contemplative interior
Beneath the doctrine runs a quieter stream that this index pays particular attention to. Richard Rohr reintroduces the contemplative roots of the faith — the Desert Fathers and Mothers, the prayer of quiet, the mutuality of the Trinity, and a spirituality of inner transformation into Christ. Kathleen Norris's *The Cloister Walk* lives that tradition from the inside, recounting a year among Benedictine monks and the slow work of the monastic hours. It is the same contemplative impulse that, in other traditions, presses past the personal God toward the Absolute — and the comparison is one of the deepest questions in the study of religion.
How to read this collection
Read together, these works hold scripture, history, scholarship, apologetics, fiction, and memoir side by side — a tradition large enough to contain Bunyan's allegory and Pagels's archaeology, Bonhoeffer's resistance and Norris's silence. For the authoritative outside frame, Encyclopædia Britannica's Christianity entry sets the doctrine and history in order. This essay describes the tradition and the conversation around it; it does not adjudicate the claims. The collection is the longer answer to a short question — what is Christianity? — assembled from the voices best placed to give it.