Key events and influences in the evolution of Christianity:
About A.D. 100 to 300: While missionaries spread Christianity throughout the Mediterranean world, the largest population of early Christians could be found in Rome. Christianity was still considered a cult, and Roman Christians were often punished and even killed.
330: The Emperor Constantine legalizes Christianity, making it the official religion of the Roman Empire.
410: St. Augustine writes his Confessions, providing the foundation of Christian theology with his teachings on morality, predestination (a belief that the events of our lives are determined even before we are born), and original sin. St. Augustine is the most important and complex theologian of the late ancient world.
Around 800: Charlemagne rules the Holy Roman Empire in Europe. Christianity spreads as far north as Ireland.
900 to 1400 (the Middle Ages): Monasteries and cathedrals are built throughout Europe. Pilgrimages to the tombs or relics of saints/martyrs become popular.
About 1350 to 1600 (the Renaissance, beginning in Italy): Christianity focuses less on the sins of humankind, and there is more optimism about the fate of humanity.
1517 (the Reformation): In response to increasing corruption in the church, Martin Luther leads the Reformation, and Protestantism becomes an alternative to Roman Catholicism. The Catholic Church responds with the Counter-Reformation. To rebuild its damaged image, the Catholic Church emphasizes the importance of saints and miracles and the sanctity of the Virgin Mary.
1700s and 1800s (the Enlightenment): This philosophical movement is based on “reason” and the discoveries of science. It is skeptical of the Church and irreverent toward any religiosity. As a result, Christianity loses some of its authority.
Present day: Twenty-five percent of the world's population is Christian, making it one of the world’s major religions. Missionaries have spread Christian doctrine to every continent but Antarctica, often bringing to the indigenous peoples not only Christian faith but also the trappings and demands of Western culture. This has caused Christianity to be identified, for better or worse, with Western culture. Christianity is now categorized into three major sects: Eastern Orthodox (which maintains the traditions of Constantine and the Early Church), Protestantism (which has been divided into numerous smaller denominations), and Roman Catholicism.