The religious movement that began as a Jewish sect in Roman Palestine, became the official religion of the Roman Empire, shaped Western civilization's law, art, philosophy, and political thought for two thousand years, and now claims more than two billion adherents worldwide — the largest and most geographically diverse religion in history.
Christianity began as a rumor in a province of the Roman Empire: that a executed Jew had risen from the dead. Within three centuries, that rumor had become the official religion of the empire that killed him. Within fifteen centuries, it had reshaped every aspect of European civilization. Understanding why is one of the central questions of world history.