Christianity is an Abrahamic monotheistic religion based on the Bible and the teachings of Jesus. The Gospels state that Jesus is the Son of God and rose from the dead after his crucifixion, whose coming as the messiah (Christ) was prophesied in the Old Testament and chronicled in the New Testament. It is the world's largest and most widespread religion with over 2.3 billion followers, comprising around 28.8% of the world population. Its adherents, known as Christians, are estimated to make up a majority of the population in 120 countries and territories.
Christianity remains culturally diverse in its Western and Eastern branches, and doctrinally diverse concerning justification and the nature of salvation, ecclesiology, ordination, and Christology. Most Christian denominations, however, generally hold in common the belief that Jesus is God the Son—the Logos incarnated—who ministered, suffered, and died on a cross, but rose from the dead for the salvation of humankind; this message is called the gospel, meaning the "good news". The four canonical gospels of Matthew, Mark, Luke and John describe the life of Jesus and teachings as preserved in the early Christian tradition, with the Old Testament as the gospels' respected background.
Christianity began in the 1st century, after the death of Jesus, as a Judaic sect with Hellenistic influence in the Roman province of Judaea. The disciples of Jesus spread their faith around the Eastern Mediterranean area, despite significant persecution. The inclusion of Gentiles led Christianity to slowly separate from Judaism in the 2nd century. Emperor Constantine I decriminalized Christianity in the Roman Empire in 313 with the Edict of Milan. In 325, Constantine convened the Council of Nicaea, where the Nicene Creed was adopted, and where Early Christianity was consolidated into what would become the state religion by around 380. The Church of the East and Oriental Orthodoxy both split over differences in Christology during the 5th century, while the Eastern Orthodox Church and the Catholic Church separated in the East–West Schism in 1054. Protestantism split into numerous denominations from the Catholic Church during the Reformation era (16th century). Following the Age of Discovery (15th–17th century), Christianity expanded globally via missionary work, evangelism, immigration, and trade. Christianity played a prominent role in the development of Western civilization, particularly in Europe from late antiquity and the Middle Ages.
The three main branches of Christianity are Catholicism (1.3 billion people), Protestantism (800 million), and Eastern Orthodoxy (300 million), while other prominent branches include Oriental Orthodoxy (60 million) and Restorationism (35 million). Smaller church communities number in the thousands. In Christianity, efforts toward unity (ecumenism) are underway. In the West, Christianity remains the dominant religion even with a decline in adherence, with about 70% of that population identifying as Christian. Christianity is growing in Africa and Asia, the world's most populous continents. Many Christians are still persecuted in some regions of the world, particularly where they are a minority, such as in the Middle East, North Africa, East Asia, and South Asia.
Etymology
Early Jewish Christians referred to themselves as being of 'The Way' (), an expression possibly coming from Isaiah 40:3, "prepare the way of the Lord". According to Acts 11:26, the term "Christian" (, ), meaning "followers of Christ" and referring to Jesus' disciples, was first used in the city of Antioch by the non-Jewish inhabitants there. The earliest recorded use of the term "Christianity/Christianism" (, ) was by Ignatius of Antioch around 100 AD. The name Jesus comes from (), probably from ().
History
Early Christianity
Apostolic Age
Christianity originated as a Jewish movement in Judaea during the 1st century AD, within the context of late Second Temple Judaism. The earliest followers of Jesus were Jews who understood his life, death and expected return through familiar Jewish apocalyptic and messianic frameworks. They remained embedded in Jewish religious life and did not initially conceive of themselves as departing from Israel or founding a new faith. Following their conviction that Jesus had been raised from the dead, they established a community in Jerusalem that awaited Jesus's return and eschatological renewal, seeking to spread this message throughout Israel and the Jewish diaspora. Early Jewish Christianity maintained a high Christology alongside monotheism. This early community was led by the three Pillars of the Church, namely James the Just, Peter, and John. What eventually became of this earliest Christ-following community remains unclear; they were possibly displaced, relocated, or killed when the Romans destroyed Jerusalem in 70 AD.
Meanwhile, as the message about Jesus spread beyond Judea and Galilee into the broader Greco-Roman world, it increasingly attracted Gentile adherents, especially among "God-fearers": non-Jews who were attracted to Judaism and participated in synagogal worship without fully converting. This created a challenge for the movement's Jewish religious outlook, which insisted on close observance of the Jewish commandments. Against this backdrop, Paul the Apostle, a Jew of the Pharisaic school who had initially persecuted the Jesus movement, became one of its most influential missionaries following his conversion, focusing on spreading the message to non-Jews in the Eastern Mediterranean. Paul argued that Gentiles could participate in the promises of Israel through exclusive devotion to the God of Israel, faith in Christ, baptism, and participation in his death and resurrection, without full adherence to the Torah, including circumcision. This had a formative effect on the emerging Christian identity as separate from Judaism. Over time, such developments contributed to the gradual differentiation between the Jesus movement and other Jewish communities, a process that resulted in the emergence of Christianity as a separate religion.Wylen, Stephen M., The Jews in the Time of Jesus: An Introduction, Paulist Press (1995), , pp. 190–192; Dunn, James D.G., Jews and Christians: The Parting of the Ways, A.D. 70 to 135, Wm. B. Eerdmans Publishing (1999), , pp. 33–34.; Boatwright, Mary Taliaferro & Gargola, Daniel J & Talbert, Richard John Alexander, The Romans: From Village to Empire, Oxford University Press (2004), , p. 426.
Ante-Nicene period
This formative period was followed by the early bishops, whom Christians consider the successors of Christ's apostles. From the year 150, Christian teachers began to produce theological and apologetic works aimed at defending the faith. These authors are known as the Church Fathers, and the study of them is called patristics. Notable early Fathers include Ignatius of Antioch, Polycarp, Justin Martyr, Irenaeus, Tertullian, Clement of Alexandria and Origen.
During this period, there was no unified Christian movement but rather multiple competing sects, which held radically different beliefs. Christian authors began using the Greek term hairesis, meaning "school of thought", to describe rival communities, which gave rise to the concept of heresy. In the second and third centuries, figures like Justin Martyr, Irenaeus, Tertullian, and Clement of Alexandria, often retrospectively referred to as "proto-orthodox", insisting that there was one original apostolic teaching and that all rivals had deviated from it. Meanwhile, Valentinus, an Alexandrian teacher, developed a Gnostic theology in which Christ brought saving knowledge (gnosis) that enabled believers to be redeemed from the material world. Marcion, from Sinope, drew a distinction between high, purely good god, father of Christ, and the lower, merely "just" god of Israel, who demanded sacrifice and procreation. Marcion is also known to have assembled a collection of Christian texts, including his own gospel, and in doing so created one of the earliest known Christian scriptural canons. Justin Martyr, from Neapolis, disagreed with both, arguing the God of the Jewish scriptures was Christ himself before his incarnation. A gradual splitting off of Gentile Christianity left Jewish Christians continuing to follow the Law of Moses, including practices such as circumcision. By the fifth century, they and the Jewish–Christian gospels would be largely suppressed by the dominant sects in both Judaism and Christianity.
Christianity occupied an unstable position within the Roman world. In antiquity, what moderns call "religion" was closely associated with ancestral traditions and embedded within other aspects of ethnic identity. It is possible that Gentile Christians, having rejected their native gods, were perceived by their pagan neighbors as disrupting the relationship between the divine and the community, on which civic welfare depended. Early examples of persecution of Christians include the Acts of the Apostles, which portrays Saint Stephen as being killed by a mob in Jerusalem, while Paul writes that he himself had persecuted Christians prior to his vision of Christ. Additionally, Tacitus wrote that Emperor Nero blamed Christians for the Great Fire of Rome in 64 AD. In the following centuries, Church Fathers recorded accusations that Christians were responsible for droughts, famines, and plagues. Nevertheless, before the mid-3rd century, persecutions were often reactive, sporadic and local. This changed in 249, when the emperor Decius, who ruled the empire following a long period of instability, ordered all residents of the empire (except Jews) to perform a sacrifice to the Roman gods. Jews had long been excused on the basis of ancestral custom in ways that Christians, lacking any such established tradition, were not. The Diocletianic Persecution beginning in 303 was particularly severe; Christians were accused of attracting demons that disrupted traditional cult practices and threatened public order, and were subjected to confiscations, destruction of buildings, expulsions, imprisonment, and demands for sacrifice. The situation changed under Constantine (r. 306–337), who granted imperial support to Christianity, though under his rule and that of his successors, forms deemed heretical were suppressed.
Spread in the Roman Empire
Christianity spread to Aramaic-speaking peoples along the Mediterranean coast and also to the inland parts of the Roman Empire and beyond that into the Parthian Empire and the later Sasanian Empire, including Mesopotamia, which was dominated at different times and to varying extents by these empires.Michael Whitby, et al. eds. Christian Persecution, Martyrdom and Orthodoxy (2006) online edition The presence of Christianity in Africa began in the middle of the 1st century in Egypt and by the end of the 2nd century in the region around Carthage. Mark the Evangelist is claimed to have started the Church of Alexandria in about 43 AD; various later churches claim this as their own legacy, including the Coptic Orthodox Church.Eusebius of Caesarea, the author of Ecclesiastical History in the 4th century, states that St. Mark came to Egypt in the first or third year of the reign of Emperor Claudius, i.e. 41 or 43 AD. "Two Thousand years of Coptic Christianity" Otto F.A. Meinardus p. 28. Important Africans who influenced the early development of Christianity include Tertullian, Clement of Alexandria, Origen of Alexandria, Cyprian, Athanasius, and Augustine of Hippo.
King Tiridates III made Christianity the state religion in Armenia in the early 4th century, making Armenia the first officially Christian state. It was not an entirely new religion in Armenia, having penetrated into the country from at least the third century, but it may have been present even earlier.