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The history of Christianity began with the life of Jesus, an itinerant Jewish preacher and teacher, who was crucified in Jerusalem c. AD 30–33. His followers proclaimed that he was the incarnation of God, and had risen from the dead. In the two millennia since, Christianity has spread across the world, becoming the world's largest religion with over two billion adherents worldwide.

Christianity was initially a grassroots movement spread by apostles, in cities, reaching critical mass by the third century when it grew to over a million adherents. The support of the Roman emperor Constantine in the early 300s was important in transforming it into an organized religion with a formalized religious text. Art, architecture, and literature blossomed. Competing theological doctrines led to divisions, the response of the Nicene Creed of 325, which led to the 5th-century Nestorian schism and created the Church of the East and Oriental Orthodoxy. While the Western Roman Empire ended in 476, its successor states and its eastern compatriot—which became the Byzantine Empire—remained Christian.

In the Middle Ages, western monks preserved culture and provided social services. The Arab conquests devastated many Christian communities in the Middle East and North Africa, but Christianization continued in Europe and Asia and helped form the states of Eastern Europe. The 1054 East–West Schism saw the Byzantine Empire's Eastern Orthodoxy and the Catholic Church of the West separate. In spite of differences, the East requested western aid against the Turks resulting in the Crusades. Faced with internal and external challenges, the church fought heresy and established courts of inquisition. Gregorian reform led to a more centralized and bureaucratic Catholicism. Artistic and intellectual advances among western monks laid the foundations for the Renaissance and the scientific revolution.

The Western Schism and various European crises in the 14th century led to intense criticism of the Church and the 16th-century Reformation, out of which arose Protestantism. Quarrelling royal houses precipitated the European wars of religion. Different parts of Christianity variously influenced European colonialism, the Age of Enlightenment, the American and French Revolutions, the Industrial Revolution, and the Atlantic slave trade. Some Protestants created biblical criticism while others responded to rationalism with Pietism and religious revivals that created new denominations. Protestants advocated for religious tolerance, the separation of church and state and moral reform while nineteenth century missionaries laid the foundation for many nations. In the 20th century, Christianity declined in parts of the West but grew vastly in the East and the Global South.

Christianity began with Jesus of Nazareth a Jewish man and itinerant preacher in Galilee and the Roman province of Judea during the first century.^[1][2] Much about Jesus is uncertain, but his crucifixion c. 30 is well attested.^[3][4][5] The religious, social, and political climate in both regions was extremely diverse and characterized by turmoil with numerous religious and political movements.^[1][6][7] One such movement, Jewish messianism, promised a messianic redeemer descended from Israel's ancient king, David, who would save Israel. Those who followed Jesus, called disciples, saw him as that Messiah.^[8][9][10]

Jesus was a prophetic figure who proclaimed an "end-of-the-world" eschatological message of the coming kingdom of God.^[11] Incarnation, the belief that God was embodied in Jesus,^[10][12] and resurrection, the belief that after his crucifixion, he rose from the dead,^[1][13] were Christianity's earliest beliefs.^[14][10] Baptism, and the communal Eucharist celebration in memory of Jesus' last meal before death, were its earliest rituals.^[15][16]

The first Christian communities were predominantly Jewish.^[17][18] They gathered in small groups inside private homes, where the typical setting for worship was the communal meal.^[19][20] Elders (called presbyters or bishops) oversaw the small groups, providing for the economic requirements of the meal and for charitable distributions.^{[21][22][23][24]}

Numbers of adherents are approximations, but indications are Christianity began with fewer than 1000 believers.^[25] Out of these original followers, called disciples, Jesus kept twelve close to him. They became Apostles whose function was to bear witness.^[26] After Judas Iscariot died, there remained 11 original apostles to which two were then added: Matthias and Saul of Tarsus who became Paul.^[27] These thirteen Apostles, which included Peter and James, Jesus' brother, crossed the ancient world to share their message.^[28][29] Their converts then traveled to nearby towns establishing churches which then established others.^[30] Christianity grew to around one hundred small household churches consisting of an average of seventy members each by the year 100.^[25]

Christianity was largely an urban religion^[31] that spread through the Jewish diaspora^[32][33] along the trade and travel routes.^[34][35][36] Despite the martyrdoms of Stephen and James the brother of John, and the imprisonment of Peter, the movement grew, reaching Antioch, where converts were first called "Christians".^[37] From Antioch, Barnabas and Paul went out as missionaries to Cyprus, then Asia Minor, where the gospel was received by non-Jewish people as well as the Jews.^[38] The largest cities in the Roman Empire, such as Rome, Alexandria, Antioch, Ephesus and Carthage, all had Christian congregations by the end of the first century.^[39]

At the Council of Jerusalem, (c. 49), the church gathered to determine if the increasing numbers of non-Jews needed to follow Old Testament Jewish law.^[40] The council decided against it.^[41] Disagreements about Jewish law and other factors such as the departure of Christians before the destruction of Jerusalem by the Romans in 70, the development of what would become Rabbinic Judaism, and insurrections against Rome, contributed to Jewish Christianity and Gentile Christianity growing apart.^[42][43] Nevertheless, Jewish Christianity remained influential in Palestine, Syria, and Asia Minor into the second and third centuries.^[44][45]

The Jews of Alexandria had produced a Greek translation of their Hebrew Bible between the third and first centuries BC, which Christians referenced in the first two centuries.^[46][47] In the early centuries, the languages most used to spread Christianity were Greek, Syriac (a form of Aramaic), and Latin.^[48] Christian writings in Koine Greek, including the four gospels (the accounts of Jesus' ministry), letters of Paul, and letters attributed to other early Christian leaders, were written in the first century and had considerable authority even in the formative period.^[49][50] The letters of the Apostle Paul sent to the early Christian communities were circulating in collected form by the end of the first century.^[51]

Paul's missionary journeys had spread the Christian faith east into Syria and Mesopotamia where the population spoke Aramaic, not Greek. Aramaic Christians were in Adiabene (northern Iraq) by the second century.^[52] By the third century, it had spread into North Africa and across the Mediterranean region, from Greece and Anatolia into the Balkans in the East and as far as Roman Britain in the northwest.^[53][54]

Roman society reached a tipping point in the years between 150 and 250, when Christianity grew from fewer than 50,000 adherents to over a million.^[35][36] A more formal church structure developed at different times in different locations. Bishops were essential to the development of Christianity, and they rose in power and influence as they began to preside over larger areas with multiple churches.^{[55][56][57][58]} Baptism was free, and there were no fees, which made Christianity more affordable than traditional Roman religions.^[59][60] Belief was the crucial and defining characteristic of membership, and early Christianity was highly inclusive of any who expressed belief.^[61][62] Believers were separated from "unbelievers" and "heretics" by a strong social boundary.^[63][64] This unique type of exclusivity gave Christianity the psychological attraction of elitism.^[65][66]

Jesus as the Good Shepherd; catacombs of Rome, c. 300

Virgin consecrated to God in the clothes of her office, praying in orans position; Catacomb of Priscilla c. 275.

Christianity's inclusivity extended to women who comprised significant numbers of its earliest members.^[67] Women could attain greater freedom through religious activities than Roman customs otherwise permitted.^[68][69] Women in the church were prominent in church rolls,^[70][71] the Pauline epistles,^[72][73] and in early Christian art,^[74] while much early anti-Christian criticism was linked to "female initiative" indicating their role in the movement.^{[68][75][76][note 1]} There are few early records of early Christian art, but the oldest emerged in tombs c. 200.^[81][82][83] It typically fused Graeco-Roman style and Christian symbolism: the most common image was Jesus as the good shepherd.^[84][85]

The four gospels and the letters of Paul were generally regarded as authoritative, but other writings, such as the Book of Revelation and the epistles to the Hebrews, James, and I John, were assigned different degrees of authority.^[86][87][88] Gnostic texts challenged the physical nature of Jesus, Montanism suggested that the apostles could be superseded, and Monarchianism emphasized the unity of God over the Trinity.^[89] In the face of such diversity, unity was provided by the shared scriptures and the bishops.^[90][91] In the early church, canon law did not yet exist.^[92]

The Ante-Nicene period included sporadic but increasing persecution from Roman authorities, and the rise of Christian sects, cults, and movements.^[93] In the 250s, the emperors Decius and Valerian made it a capital offence to refuse to make sacrifices to Roman gods, resulting in widespread persecution of Christians. Official persecution reached its height under Diocletian in 303–311.^[94][95][96] Authorities in the Sasanian Empire also periodically persecuted Christians.^[97][98]

Late Antiquity was an age of change in which Christianity became a permitted religion, then a favored one that transformed in every capacity.^[99] In 313, the emperor Constantine, a self-declared Christian, issued the Edict of Milan expressing tolerance for all religions.^[100] Thereafter, he supported Christianity, giving bishops judicial power, and legally establishing them as equal to polytheistic priests.^[101] He devoted personal and public funds to building churches and endowed them with funds for maintenance and support of their clergy.^[102] There were churches in the majority of Roman cities by the end of the fourth century.^[103]

Christian art, literature and architecture blossomed under Constantine.^[104][105] The basilica, a type of Roman municipal court hall, became the model for Christian architecture.^[106] Frescoes, mosaics, statues, and paintings blended classical and Christian styles.^[107] Similarly, a hybrid form of poetry written in classical styles with Christian concepts emerged.^{[108][109][110]} In the late fourth century, Jerome was commissioned to translate the Greek biblical texts into the Latin language; this translation was called the Vulgate.^[111] Church fathers of this period, such as Augustine of Hippo, John Chrysostom, Gregory of Nyssa, Athanasius of Alexandria, Basil of Caesarea, Gregory of Nazianzus, Cyril of Alexandria, and Ambrose of Milan, wrote vast numbers of works.^[112]

The ascetic ideal of these early church fathers was also embraced by monasticism, which had begun early, in Syria, and was key to the development of Christianity.^{[113][114][115]} In Late Antiquity, these communities became associated with the urban holy places in Palestine (which became a center of pilgrimage), Cappadocia, Italy, Gaul, and Roman North Africa.^[116] In the 370s, Basil the Great founded the Basileias, a monastic community in Caesarea (Mazaca) which developed the first health care system for the poor, a forerunner of modern public hospitals.^[117]

Christianity's social impact, especially its charitable practices,^[118] contributed to its spread, despite competition from traditional polytheism and alternative cults and creeds.^{[119][120][note 2]} There was no legislation forcing the conversion of pagans before the Eastern Emperor Justinian I (r. 527–565), and polytheism remained in some places into the ninth century.^{[126][127][128][129]} Even so, blood sacrifice, which had been a central rite of virtually all religious groups in the pre-Christian Mediterranean, disappeared by the end of the fourth century due to hostile imperial laws.^[130][131]

While there was occasional hostility, actual religious violence between pagans and Christians was not a general phenomenon. Speech, in the form of polemical rhetoric, was the main form of violence.^[132][133] Argument centered on the true meaning of "logos". Pagans asserted logos could be found in ancient myths and poetics as allegory.^[134] Christian responses formed their first true ontologies, distinct from earlier apologetics, asserting the Christian logos.^[133][135] However, the primary focus of biblical commentators between 300 and 600 was not on polemical responses to pagans but on aiding ordinary Christians whose primary concern was sin and salvation.^[136][137] Christian baptism was distinctive and demonstrated how Christians understood these concepts in terms of the death of Christ.^[138] As theology until 640 evolved, it held to the paradox of God’s incarnation, and the decisive human contribution to redemption seen in Jesus Christ as "the new human being, who is God".^[139]

Before the fourth century, Judaism had been an approved religion, while Christianity was persecuted as an illegal superstition; during the fourth century, Christianity became favored by emperors and Judaism came to be seen as a heresy.^[140] Still, Augustine of Hippo argued that Jews should not be killed or forcibly converted; they should be left alone because they preserved the teachings of the Old Testament and were "living witnesses" of the New Testament.^[141] Most Jews and Christians (with the exception of the Visigoths in Spain) lived peacefully alongside each other into the High Middle Ages.^{[142][143][note 3]}

Constantine and his successors attempted to fit the church into their political program.^[147] Church leaders responded with the first fully articulated limitation on secular authority, arguing that the empire was part of the universal church, not the reverse.^[148] For most of Late Antiquity, the popes – the successors to Saint Peter as bishop of Rome – had limited influence, and did not yet have the power needed to break free of secular involvement in church affairs. However, papal power began to rise as eastern patriarchs looked to the Roman Pope to resolve disagreements.^{[149][150][151]}

Christianity grew rapidly throughout this period.^[152][153] Christians in Persia, (present-day Iraq), were deeply persecuted in Late Antiquity, but their numbers still grew. A form of Christianity made inroads among Arabs in Palestine, Yemen, and Arabia.^[154] In the fourth century the percentage of Christians was as high in the Sasanian Empire as in the Roman Empire.^[155] Even as the Huns, Ostrogoths, Visigoths, and Vandals caused havoc in the Roman Empire in the fourth and fifth centuries, many converted to Christianity.^{[156][157][158]} Syria was home to a vibrant Christianity.^[154] The gospel was first brought to Central Asia and China by Syriac-speaking missionaries.^[52]

Christian institutions in Asia or East Africa never developed the kind of influence the European churches and Byzantium did.^[159] However, Armenia became the first state to adopt Christianity as its religion in 301 followed by Caucasian Albania, Ethiopia and Eritrea.^{[160][161][162]} Christianity, a minority faith in Britain since the second century,^[163] began to be displaced by Anglo-Saxon paganism in the fifth century;^[164] this process began reversing after the Gregorian mission of 597.^[165] Missionaries also began to convert the Irish in the early fifth century.^[166]

Regional Christianities produced diverse and sometimes competing theologies.^[167][168] Ancient Christian authors identified any practice or doctrine which differed from apostolic tradition as heresy.^{[169][64][170]} The number of laws directed at heresy indicate it was a much higher priority than paganism for Christians of this period.^{[171][172][note 4]}

For decades, Arianism embroiled the entire church, the laity (people who were not clergy) and clergy alike, in arguing whether Jesus' divinity was equal to the Father's.^{[18][176][177]} The First Council of Nicaea in 325 attempted to resolve the controversy with the Nicene Creed though some refused to accept it.^[178][179] The development of heresy demonstrated the importance of boundaries, and became a force that shaped identity, providing a path for cultural assimilation and social stability.^[168] Along the Eastern Mediterranean, where Christian factions struggled without resolution, Christian communities were weakened, affecting their long-term survival.^[180]

Christian scriptures were formalized as the New Testament and distinguished from the Old Testament by the fourth century.^[181][182] Despite agreement on these texts, differences between East and West were becoming evident.^{[183][184][185]} The West was solidly Nicean while the East was largely Arian.^[186] The West condemned Roman culture as sinful and resisted state control, whereas the East harmonized with Greek culture and aimed for unanimity between church and state.^{[187][188][189]} The marriage of clerics was accepted in the East but forbidden in the West.^[190][191] The East advocated sharing the government of the church between five church leaders, arguing that the Patriarchs of Constantinople, Alexandria, Antioch, and Jerusalem were equal to the Pope. Rome asserted papal primacy.^[192][193]

Controversies over how Jesus' human and divine natures coexisted peaked when Nestorius declared Mary as the mother of Jesus' humanity, not his divinity, thereby giving Jesus two distinct natures.^[194] This led to a series of ecumenical councils: the Council of Ephesus was the church's third council, and it condemned Nestorius. Held in 431, the church in the Persian Empire refused to recognize its authority. This led to the first separation between East and West. Two general groups of Persians and Syrians became the Church of the East (also known as the Assyrian, Nestorian, or Persian Church), while the majority of Christians in Syria and Mesopotamia became Syrian Orthodox (Jacobite).^{[195][note 5]} This cut off the flourishing school of Syrian Semitic Christian theologians and writers from the rest of Christendom.^[198] The Church of the East lay almost entirely outside the Byzantine Empire.^[199] It became the principal Church in Asia in the Middle Ages.^[200]

In 451 the fourth council was the influential Council of Chalcedon.^{[201][note 6]} While most of Christianity accepted the Chalcedonian Definition which emphasizes that the Son is "one person in two natures", there were those who found that description too close to the duality of Nestorianism, so after 484, they separated into Oriental Orthodoxy that sees only "One Nature of God the Incarnate Logos".^{[203][204][205]}

After 476 and the breakup of the Western Roman Empire, there was no center of political power in the European West. The ensuing socio-political fragmentation left the church with responsibility for the folk.^[206][207] Thereafter, western Europe developed in a manner distinctively different from the remaining empire in the East. For the next five centuries, Western culture and civilization were preserved and passed on primarily by monks while the Eastern Roman Empire continued to be a Roman Empire with an emperor, a civil government, and a large army.^{[208][209][210][211]}

The religious policies of the Eastern Roman Emperor Justinian I (r. 527–565) reflected his conviction that the unity of the Empire presupposed unity of faith: he persecuted pagans and religious minorities and purged government and church bureaucracies of those who disagreed with him.^[212][211] He contributed to cultural development,^[213] and integrated Christian concepts with Roman law in his Corpus Juris Civilis which remains the basis of civil law in many modern states.^[92][214]

In Gaul, the Frankish king Clovis I converted to Catholicism; his kingdom became the dominant polity in the West in 507, gradually converting into a Christian kingdom over the next centuries.^[208][209] Papal influence rose as competition within the church continued to lead people to Rome to resolve their problems.^[192][215] Gregory the Great (590-604) gained prestige and power for the papacy by leading the response to invasion by the Lombards in 592 and 593, reforming the clergy, standardizing music in worship, sending out missionaries and founding new monasteries.^[216][217] Until 751, the Pope remained a subject of the Byzantine emperor.^[193]

By the early 600s, Christianity had spread around the Mediterranean.^[218] However, between 632 and 750, the Islamic caliphates conquered the Middle East, North Africa and the Iberian Peninsula.^{[219][220][221]} Muslim rule devastated Asian churches in the cities, but between the fifth and the eighth centuries Christianity had also been adopted in remote areas^{[note 7]} better enabling their survival.^[223][224] In the same period, war on multiple fronts contributed to the Eastern Roman Empire becoming the independent Byzantine Empire.^[225] Until the eighth century, Germanic Europe remained largely impoverished, politically fragmented and dependent on the church.^[208][209]

The Early Middle Ages was the formative period of Western "Christendom" which emerged at the end of this age.^[226][227] In and around this largely Christian world, barbarian invasion, deportation, and neglect produced large "unchurched" populations for whom Christianity was one religion among many that could be fused with aspects of local paganism.^[228][229] The church of this age was only indirectly influenced by the Bible.^[230]

Until the end of the Early Middle Ages, Western culture was preserved and passed on primarily by monks known as "regular clergy" because they followed a regula: a rule.^[210][151] The rule included chastity, obedience and poverty sought through prayer, memorization of scripture, celibacy, fasting, manual labour, and almsgiving.^[231][232]

Monasteries served as orphanages and inns for travelers, and provided food for those in need.^{[233][234][235]} They supported literacy, practiced classical arts and crafts, and copied and preserved ancient texts in their scriptoria and libraries.^[236][237] Dedicated monks created illuminated manuscripts.^[238] From the sixth to the eighth centuries, most schools were connected to monasteries, but methods of teaching an illiterate populace could also include mystery plays, vernacular sermons, saints' lives in epic form, and artwork.^{[227][239][240]}

This was an age of uncertainty, and the role of relics and holy men able to provide special access to the divine became increasingly important.^[241][242] Donations for the dead to receive prayers (with that special access) provided an ongoing source of wealth.^[243][244] Monasteries became increasingly organized, gradually establishing their own authority as separate from political and familial authorities, thereby revolutionizing social history.^[245][246] Medical practice was highly important, and medieval monasteries were best known for their public hospitals, hospices and their contributions to medicine.^[247][248] The sixth-century Rule of Saint Benedict has had extensive influence.^{[249][250][251]}

The East developed an approach to sacred art unknown in the West, adapting ancient portraiture in icons as intercessors between God and humankind.^[252] In the 720s, the Byzantine Emperor Leo banned the pictorial representation of Christ, saints, and biblical scenes, and destroyed much early representational art.^[253] The West condemned the Byzantine iconoclasm of Leo and some of his successors.^[254] By the tenth and early eleventh centuries, Byzantine culture began to recover its artistic heritage.^[255][256]

Eastern Europe had been exposed to Christianity during Roman rule, but it was Byzantine Christianity, brought by the ninth-century saints Cyril and Methodius, that was integral to the formation of its modern states.^{[257][258][198]} The brothers developed the Glagolitic alphabet to translate the Bible into the local language. Their disciples then developed the Cyrillic script which spread literacy and became the cultural and religious foundation for all Slavic nations.^{[259][260][261]}

In 635, the Church of the East brought Christianity to the Chinese Emperor whose decree to license the Christian faith was copied onto the Sianfu stele.^[262] It spread into northwestern China, Khotan, Turfan, and south of Lake Balkash in southeastern Kazakhstan, but its growth was halted in 845 by Emperor Wu-Tsung, who favoured Taoism.^[263] The Church of the East evangelized all along the Silk Road and was instrumental in converting some of the Mongol/Turkic peoples.^[264] After 700, when much of Christianity was declining, there were flourishing Christian societies along all the main trade routes of Asia, South India, the Nubian kingdoms, Ethiopia, and in Caucasian Armenia and Georgia.^[154][265]

In Western Europe, canon law was instrumental in developing key norms concerning oaths of loyalty, homage, and fidelity.^[266] These norms were incorporated into civil law, where traces remain.^[267] Within the tenets of feudalism, the church created a new model of consecrated kingship unknown in the East, and in 800, Clovis' descendant Charlemagne became its recipient when Pope Leo III crowned him emperor.^[268] Charlemagne engaged in a number of reforms which began the Carolingian Renaissance, a period of intellectual and cultural revival.^[269] His crowning set the precedent that only a pope could crown a Western emperor enabling popes to claim emperors derived their power from God through them.^[270] The Papacy became free from Byzantine control, and the former lands of the Exarchate became States of the church.^[270][271] However, the papacy was still in need of aid and protection, so the Holy Roman emperors often used that need to attempt domination of the Papacy and the Papal States.^[270] In Rome, the papacy came under the control of the city's aristocracy.^[271][272]

In Russia, the baptism of Vladimir of Kiev in 989 is traditionally associated with the conversion of the Kievan Rus'.^[273] Their new religious structure included dukes maintaining control of a financially-dependent church.^{[274][275][note 8]} Monasticism was the dominant form of piety for both peasants and elites who identified themselves as Christian while retaining many pre-Christian practices.^[277]

Viking raids in the ninth and tenth centuries destroyed many churches and monasteries, inadvertently leading to reform. Patrons competed in rebuilding so that "by the mid-eleventh century, a wealthy, unified, better-organized, better-educated, more spiritually sensitive Latin Church" resulted.^[278] There was another rise in papal power in the tenth century when William IX, Duke of Aquitaine, and other powerful lay founders of monasteries, placed their institutions under the protection of the papacy.^{[279][280][281]}

Membership in the Christendom of this age began with baptism at birth.^{[282][283][284]} Every follower was supposed to have some knowledge of the Apostles' Creed and the Lord's Prayer, to rest on Sunday and feast days, attend mass, fast at specified times, take communion at Easter, pay various fees for the needy, and receive last rites at death.^[285][286] The medieval papacy gained authority in every domain of European life as it gradually came to resemble the monarchies of its day.^[287][288]

Canon law became a huge, highly complex legal system, and yet these hundreds of laws largely omitted Christianity's earlier principles of equity and inclusivity.^[289][290] The High Middle Ages saw the formation of several fundamental Christian doctrines, such as the seven sacraments, the just reward for labour, "the terms of Christian marriage, the nature of clerical celibacy and the appropriate lifestyle for priests".^[291] Heresy was more precisely defined.^[292] Purgatory became an official doctrine. In 1215, confession became required for all.^[293][294] The rosary was created after veneration of Mary, mother of Jesus became a central aspect of the period.^[295]

Beginning at Cluny Abbey (910), which used Romanesque architecture to convey a sense of awe and wonder and inspire obedience, monasteries gained influence through the Cluniac Reforms.^{[296][297][note 9]} However, their cultural and religious dominance began to decline in the mid-eleventh century when secular clergy, who were not members of religious orders, rose in influence.^[299] Monastery schools lost influence as cathedral schools spread,^[300] independent schools arose,^[301] and universities formed as self-governing corporations chartered by popes and kings.^[302][303] Canon and civil law became professionalized, and a new literate elite formed, further displacing monks.^[304][305] Throughout this period, the clergy and the laity became "more literate, more worldly, and more self-assertive".^{[306][note 10]}

The reform of Pope Gregory VII (1073–1085) began "a new period in church history".^[192][310] Previously, the power of kings and emperors had been at least partly founded on connection to the sacred.^[311][304] Gregorian Reform intended to divest Western rulership of its sacramental character, and to establish the preeminence of the church by freeing it from state control.^[312] This reinforced the popes' temporal power, enabling a reorganization of the administration of the Papal States which brought a substantial increase in wealth. This enabled popes to become patrons in their own right,^{[313][314][315]} which allowed them to consolidate territory, centralize authority, and establish a bureaucracy.^{[316][317][304]}

State administrations were also centralizing, and competition between church and state, who claimed legal and tax jurisdiction over the same populace, created conflicts.^[308][318] A major example was the Investiture Controversy in the Holy Roman Empire, a conflict between the Holy Roman Emperor Henry IV and Pope Gregory VII over the secular appointment of bishops and abbots and control of their revenues.^{[319][320][321][322]} For the church, ending lay investiture would support independence from the state, encourage reform, and provide better pastoral care. For the kings, who could better control the powers and revenues of appointed bishops than those of hereditary noblemen, ending lay investiture meant the power of the Holy Roman Emperor and the European nobility would be reduced.^{[323][324][325][326]}

The Dictatus Papae of 1075 declared the pope alone could invest bishops.^[327] Disobedience to the Pope became equated with heresy;^[328] when Henry IV rejected the decree, he was excommunicated, which contributed to a civil war.^{[329][330][331]} A similar controversy occurred in England.^[332]

The Oriental Orthodox Church (the Church of the East), which had separated after Chalcedon, survived against the odds with help from Byzantium.^[333] At the height of its expansion in the thirteenth century, the Church of the East stretched from Syria to eastern China and from Siberia to southern India and southern Asia.^[334] The second separation between east and west took place in 1054 when the church within the Byzantine Empire formed Byzantine Eastern Orthodoxy, which thereafter remained in communion with the Ecumenical Patriarchate of Constantinople, not the Pope.^[335]

Along with geographical separation, there had long been many cultural differences, geopolitical disagreements, and a lack of respect between east and west.^[336][337] Nevertheless, the Byzantine emperor Alexios I Komnenos still asked Pope Urban II for help with the Seljuk Turks in 1081,^[338] and Urban appealed in 1095 to European Christians to "go to the aid of their brethren in the Holy Land".^{[339][340][341]}

Urban's message had great popular appeal. Drawing on powerful and prevalent aspects of folk religion, the First Crusade connected pilgrimage, charity, and remission of sin with a willingness to fight.^[342][343] It gave ordinary Christians a tangible means of expressing brotherhood with the East and carried a sense of historical responsibility.^[344] The Crusades contributed to the development of national identities in European nations and, eventually, increased division with the East.^[345] The evolving cult of chivalry of the Christian knight became a powerful social and cultural influence before its decline during the 1400s.^[346][347] One significant effect of the Crusades was the invention of the indulgence.^[348]

Christianity was declining in Mesopotamia and inner Iran, although some Christian communities continued to exist further to the east.^[349][350] As churches in Egypt, Syria, and Iraq became subject to fervently Islamic militaristic regimes, Christians were designated as dhimma, a status that guaranteed their protection but enforced their legal inferiority.^[351] Different communities adopted various survival strategies: some withdrew from interaction, others converted to Islam, and others sought outside help.^[352]

The Christianization of Scandinavia occurred in two stages: first, in the ninth century, missionaries operated without secular support; then a secular ruler would begin to oversee Christianization in their territory until an organized ecclesiastical network was established.^[353] By 1350, Scandinavia was an integral part of Western Christendom.^[354]

The Christian wars of reconquest, which lasted over 200 years, had begun in Italy in 915 and in Spain in 1009 to retake territory lost to Muslims, causing fleeing Muslims in Sicily and Spain to leave behind their libraries.^[355] Between 1150 and 1200, monks searched those libraries and found the works of Aristotle, Euclid and other ancient writers.^[356] The West's rediscovery of the complete works of Aristotle led to the Renaissance of the twelfth century. It also created conflict between faith and reason, resolved by a revolution in thought called scholasticism.^[357][358] The scholastic writings of Thomas Aquinas impacted Catholic theology and influenced secular philosophy and law into the modern day.^{[359][360][361]} The renaissance revived the scientific study of natural phenomena which led to the scientific revolution in the West.^{[362][363][364]} There was no parallel renaissance in the East.^[252]

Byzantine art exerted a powerful influence on Western art in the twelfth and thirteenth centuries.^[365] Gothic architecture, intended to inspire contemplation of the divine, began in the same centuries.^[366][367] The Cistercian movement was a wave of monastic reform after 1098; Cistercians became instrumental in technological advancement in medieval Europe.^{[368][369][370]}

The twelfth century saw a change in the goal of a monk from contemplative devotion to active reform.^[371][372] Among these new activist preachers was Saint Dominic who founded the Dominican Order and was significant in opposing Catharism.^[373][283] A military campaign to eliminate the Albigensian heresy also known as Catharism, conducted by Pope Innocent III and the King of France, Philip Augustus, was begun in 1209.^[374][375] The campaign took a political turn when the king's army seized and occupied strategic lands of nobles who had not supported the heretics, but had been in the good graces of the Church.^[376] It ended in 1229 when the region was brought under the rule of the French king, creating southern France, while Catharism continued until 1350.^[377][378]

Moral misbehaviour and heresy committed by either laity or clergy were prosecuted in inquisitorial courts that were only established when needed and were composed of both church and civil authorities.^{[379][380][381]} Though these courts had no joint leadership nor joint organization, the Dominican Order held the primary responsibility for conducting inquisitions.^{[382][383][384]} The Medieval Inquisition brought between 8,000 and 40,000 people to interrogation and sentencing; death sentences were relatively rare.^[385] The penalty imposed most often was an act of penance which might include public confession.^[386] Bishops were the lead inquisitors, but they did not possess absolute power, nor were they universally supported.^[387][388] Inquisition became stridently contested as public opposition grew and riots against the Dominicans occurred.^{[389][390][391]} The Fourth Lateran Council of 1215 empowered inquisitors to search out moral and religious "crimes" even when there was no accuser. In theory, this granted them extraordinary powers. In practice, without sufficient local secular support, their task became so overwhelmingly difficult that inquisitors were endangered and some were murdered.^[392]

From 1170-80, the Jewish philosopher Moses ben Maimon (Maimonides) wrote his fourteen-volume code of Jewish law and ethics, titled the "Mishneh Torah".^[393] A turning point in Jewish-Christian relations occurred when the Talmud was put "on trial" in 1239 by Pope Gregory IX because of contents that mocked the central figures of Christianity.^[394] Talmudic Judaism came to be seen as so different from biblical Judaism that old Augustinian obligations to leave the Jews alone no longer applied.^{[395][394][396]} A rhetoric with elaborate stories casting Jews as enemies accused of ritual murder, the blood libel, and desecration of the Christian eucharist host grew among ordinary folk. The spread of the Black Death led to attacks on Jewish communities throughout the Holy Roman Empire by people who blamed them for the epidemic.^{[397][398][399]} Jews often acted as financial agents for the nobility, providing them loans with interest while being exempt from certain financial obligations. This attracted jealousy and resentment.^[400] Count Emicho of Leiningen massacred Jews in search of supplies and protection money, while the York massacre of 1190 also appears to have originated in a conspiracy by local leaders to liquidate their debts.^[401]

The nobility of Eastern Europe prioritized subduing the Balts, the last major polytheistic population in Europe, over crusading in the Holy Land.^{[402][note 11]} In 1147, the Divina dispensatione gave these nobles indulgences for the first of the Northern Crusades, which intermittently continued, with and without papal support, until 1316.^{[404][405][406]} The clergy pragmatically accepted the forced conversions the nobles perpetrated despite continued theological emphasis on voluntary conversion.^[407]

The many calamities of the "long fourteenth century" – plague, famine, wars, and social unrest – led European people to believe the end of the world was imminent.^{[408][409][410]} This belief ran throughout society and became intertwined with anticlerical and anti-papal sentiments.^{[411][283][note 12]} Criticism of the church became an integral part of late medieval European life, and was expressed in both secular and religious writings, and movements of heresy or internal reform,^[413][414] although most attempts at reform between 1300 and 1500 failed.^[415][416]

In 1320, Dante Alighieri completed the Divine Comedy, a Christian allegory of reason and divine revelation, sin and ultimate truth, using Catholic doctrine on Hell, Purgatory, and Paradise. It became one of the greatest works in literary history.^[417]

In 1309, Pope Clement V fled Rome's factional politics by moving to Avignon in southern France. This Avignon Papacy, consisting of seven successive popes, unintentionally diminished papal prestige and power.^[418][419] Pope Gregory XI returned to Rome in 1377.^{[420][421][409]} After Gregory's death the following year, the papal conclave elected Urban VI to succeed him, but the French cardinals disapproved and elected Robert of Geneva instead. This began the Western Schism, during which there was more than one pope.^[422] In 1409, the Council of Pisa's attempted resolution resulted in the election of a third separate pope. The schism was finally resolved in 1417, with the election of Pope Martin V.^[423][424]

Throughout the Late Middle Ages, the church faced powerful challenges and vigorous political confrontations.^[425][426] The English scholastic philosopher John Wycliffe (1320–1384) urged the church to again embrace simplicity by giving up its property and wealth, to stop being subservient to secular politics, and to deny papal authority.^[427][428] Wycliffe's teachings were condemned as heresy, but he was allowed to live out the last two years of his life in his home parish.^[429] In 1382, Wycliffe created the first English translation of the Bible.^[430] Wycliffe's teachings influenced the Czech theologian Jan Hus (1369–1415) who also spoke out against what he saw as corruption in the church.^[431] Hus was convicted of heresy and burned at the stake.^[432] This was the impetus for the Bohemian Reformation and led to the Hussite Wars.^{[433][434][435]}

Meanwhile, a vernacular religious culture called the Devotio Moderna attempted to work toward a pious society of ordinary people.^[436] Through the Dutch scholar Desiderius Erasmus Roterodamus (1466–1536), Christian humanism grew and impacted literature and education.^[437] Between 1525 and 1534, William Tyndale used the Vulgate and Greek texts from Erasmus to create the Tyndale Bible.^[430] King James commissioned the King James Version in 1604, using all previous versions in Latin, Greek, and English as sources. It was published in 1611.^[438]

A 1452 reunion agreement between the Orthodox and Catholic churches was negated by the Fall of Constantinople to the Ottoman Empire in 1453, which sealed off Orthodoxy from the West for more than a century.^{[439][440][441]} Islamic law did not acknowledge the Byzantine church as an institution, but a concern for societal stability allowed it to survive. Financial handicaps, constant upheaval, simony, and corruption, impoverished many, and made conversion an attractive solution.^{[442][443][444]} This led to the state confiscating churches and turning them into mosques.^[444] The patriarchate became a part of the Ottoman system under Suleiman the Magnificent (1520–1566),^[445][443] and by the end of the sixteenth century, widespread desperation and low morale had produced crisis and decline. When Cyril I Loukaris (1572 – 1638) became Patriarch in 1620, he began leading the church toward renewal.^[444] A shared hostility towards Catholicism led Cyril to reach out to the Protestants of Europe and to be deeply impacted by their Reformation doctrines.^[446] Protestant pressure produced the Lukaris Confession.^[447]

The flight of Eastern Christians from Constantinople, and the manuscripts they carried with them, were important factors in stimulating literary renaissance in the West.^[448][196] The Catholic Church became a leading patron of art and architecture, commissioning work, and supporting renowned artists.^[449][450] Even while fifteenth-century popes struggled to reestablish papal authority, the Renaissance Papacy transformed Rome by rebuilding St. Peter's Basilica and establishing the city as a prestigious centre of learning.^[451] Reformation Protestants condemned these popes as corrupt for their lack of chastity, their nepotism, and the selling of "hats and indulgences".^[452]

In Russia, Ivan III of Russia adopted the style of the Byzantine imperial court to gain support among the Rus' elite who saw themselves as the new 'chosen' and Moscow as the New Jerusalem.^[453] Jeremias II (1536–1595), the first Orthodox patriarch to visit north-eastern Europe, founded the Orthodox Patriarchate of Russia during his journey.^[454][443]

The sixteenth-century success of Christianity in Japan was followed by one of the greatest persecutions in Christian history.^[455][456]

Colonialism, which began in the fifteenth century, originated either on a militaristic/political path, a commercial one, or with settlers who wanted land.^[457] Christian missionaries soon followed with their own separate agenda.^{[458][459][460][461]} "Companies, politicians, missionaries, settlers, and traders rarely acted together" and were often in conflict.^[458] Some missionaries supported colonialism while just as many took stances against colonial oppression.^{[462][463][464]} Between 1500 and 1800, Catholic Christianity gained followers worldwide through missionaries from the Spanish, Portuguese, and French empires.^{[465][460][466]}

Long before the first European colonists arrived, indigenous Christian communities, which were often in conflict with the newcomers, had existed in Asia and Africa.^[467] Prior to the Portuguese' landing, St.Thomas Christian communities in southern India had existed continuously for more than 1000 years.^[468] In the 16th century, baptized Kongolese Christians were taken by Portuguese slavers to the Caribbean and Brazil where there are clear traces that they evangelized among their fellow sufferers. Former slaves returned to West Africa "with Bible in hand" preceding European Protestant missionaries, founding Freetown, which would play a central role in the Christianization of West Africa.^[334]

During the Hispanic colonization of the Americas, the merging of native and Spanish traditions created a multitude of indigenous Christianities.^[469] In the seventeenth and eighteenth centuries, reductionist villages for natives in regions of Paraguay, Argentina and Brazil were established by Jesuits and other orders. Jesuits promoted local skills and technical innovations, working exclusively in the native language to form an "agrarian collective" kept separate from the rest of colonial society, with serfdom and forced labor forbidden. The Spanish crown resented this autonomy, and the Jesuit order was banned; its members were expelled from Spain in 1767. Thereafter, reduction territories became open to settlers, and natives often became bondmen.^{[470][note 13]}

Women in the Middle Ages were considered incapable of moral judgment and authority.^{[292][note 14]} However, there were women who became distinguished leaders of nunneries, exercising the same powers and privileges as their male counterparts, such as Hildegard of Bingen (d. 1179), Elisabeth of Schönau (d. 1164/65), and Marie d'Oignies (d. 1213).^[473][474] Although the Catholic Church had long ruled that witches did not exist, the conviction that witches were both real and malevolent developed throughout fifteenth-century European society.^[475][476] No single cause of "witch frenzy" is known, although the Little Ice Age is thought to have been a factor.^[477] Approximately 100,000 people, of whom 80% were women accused by those in their own villages, were prosecuted in mostly civil trials between 1561 and 1670; 40,000 to 50,000 were executed.^[478][476]

While the medieval church never officially repudiated Augustine's doctrine of protecting the Jews, defining them as heretical outsiders became increasingly common in European society of the fifteenth century.^[479] Local rulers repeatedly evicted Jews from their lands and confiscated Jewish property.^{[480][481][482]}

Between 1478 and 1542, the Spanish and Portuguese inquisitions were initially authorized by the church but soon became state institutions.^{[483][484][485]} Authorized by Pope Sixtus IV in 1478, the Spanish Inquisition was established to combat fears that Jewish converts were conspiring with Muslims to sabotage the new state.^[486][487] Five years later a papal bull conceded control of the Spanish Inquisition to the Spanish crown making it the first national, unified, centralized institution of the nascent Spanish state.^{[488][489][490]} The Portuguese Inquisition, controlled by a state board of directors, incorporated anti-Judaism before the end of the fifteenth century and forced conversion led many Jewish converts to Portuguese colonies in India, where they suffered as targets of the Goa Inquisition.^[491][484] The bureaucratic and intellectual Roman Inquisition, best known for its condemnation of Galileo, served the papacy's political aims in Italy.^[492]

In 1517, Martin Luther initiated the Reformation with his Ninety-five Theses.

The fourteenth century had been among the most violent for minorities, and canon law had done little to reduce oppression, giving rise to protests against the church that led to the Protestant Reformation.^[289][493] Traditionally said to have begun when the Catholic monk Martin Luther nailed his Ninety-five Theses to the church door in Wittenberg in 1517, Luther challenged the nature of the church's role in society and its authority.^[494][495] For Catholics, authority meant the Pope. For the protesters, authority was in the priesthood of believers and Scripture.^{[495][note 15]}

After protracted and acrimonious struggle, three primary religious traditions emerged alongside Roman Catholicism: the Lutheran, the Reformed, and the Anglican traditions.^[498][499] For Luther, the church's role in society was determined by two realms of human existence, the secular and the sacred, where one is not allowed to dominate the other, and only secular authority has the right to use force.^[500][495] The Reformed churches, formed by followers of theologian John Calvin, argued that the church had the right to function without interference from the state, and established the ideal of a constitutional representative government in both the church and in society.^[501][502] Puritans and other Dissenter groups in England, Huguenots in France, the “Beggars” in Holland, the Covenanters in Scotland who produced Presbyterianism, and the Pilgrim Fathers of New England are Reformed churches that trace their theological roots to Calvin.^[502] The Anglican church was first created as the Church of England by Henry Tudor. Anglicanism preserved Catholic doctrine and the church's established role in society, but changed its authority from the pope to the king.^[503][504]

The Roman Catholic Church responded in the Counter-Reformation, spearheaded by ten reforming popes between 1534 to 1605. The Council of Trent (1545–1563) denied each Protestant claim, and laid the foundation of modern Catholic policies. New monastic orders were formed, including the Society of Jesus – the "Jesuits" – who adopted military-style discipline and strict loyalty to the Pope.^[505][506] Monastic reform also led to the Spanish mystics and the French school of spirituality,^[507] as well as the Uniate church which used Eastern liturgy but recognized the authority of Rome.^[508]

Quarreling royal houses, already involved in dynastic disagreements, became polarized into the two religious camps.^[509] In 1562, France became the centre of a series of wars, of which the largest and most destructive was the Thirty Years' War (1618–1648).^[510][511] While some scholars argue that these wars were varieties of the just war tradition for religious liberty and freedom,^[512] most historians argue that the wars were more about nationalistic state-building and economics, and less about religion.^{[513][514][511]}

The era of political absolutism followed the breakdown of Christian universalism in Europe.^[515] Abuses from absolutist Catholic kings gave rise to a virulent critique of Christianity that first emerged among the more extreme Protestant reformers in the 1680s as an aspect of the Age of Enlightenment.^[516][517] For 200 years, Protestants had been arguing for religious toleration,^[518][519] and by the 1690s, secular thinkers were rethinking the state's reasons for persecution, and they too began advocating for religious toleration.^[520][521] Concepts of freedom of religion, speech, and thought became established in the West.^{[522][523][524]}

Secularisation spread at every level of European society.^[525] Pioneered by Protestants, Biblical criticism advocated historicism and rationalism to make study of the Bible more scholarly and secular in the 1700s.^{[526][527][528]} In reaction to rationalism, Pietism, a holiness movement, began in Europe and spread to the Thirteen Colonies where it contributed to the First Great Awakening, a religious revival of the 1700s.^{[529][530][531]} Pietist Moravians, out of the Lutheran church, came to Georgia in 1732 where they influenced John Wesley, an Anglican missionary in Savannah.^[532][533] Wesley returned to England, and began preaching in open-air meetings leading to creation of the Methodist church.^{[534][535][536][537]} In the colonies, Presbyterians and Baptists contributed to revival, and to divisions over it, which formed political parties and leant crucial support for the American Revolution.^{[538][539][540]} In 1791, the new United States became the first Christian nation to mandate a separation of church and state; religious pluralism became the norm.^[541][542]

The rise of Protestantism contributed to human capital formation,^[543] the development of a new work ethic,^[544] economic growth,^[545] the European state system,^[546] and the development of modern capitalism in Northern Europe.^[547] However, urbanization and industrialisation created a plethora of new social problems.^[548][549] In Europe and North America, both Protestants and Catholics provided massive aid to the poor, supporting family welfare, and providing medicine and education.^[550]

The French Revolution led to a 1794 attempt by radical revolutionaries to violently de-Christianize France.^[551] As a result, the Eastern Orthodox Church rejected Enlightenment ideas as too dangerous to embrace.^[443]

The Second Great Awakening - a religious revival of the 1800s–1830s - produced Mormonism, Restorationism and the Holiness movement.^[552] Mormons preached the restoration of first-century Christianity, upheld millennialism and premillennialism, and sought to create a religious utopia.^[553] Restorationists, such as the Churches of Christ, Jehovah's Witnesses, and Seventh Day Adventists, also focused on restoring practices of the early church, emphasizing baptism as the crucial conversion experience, and biblical authority.^[554][555] The Holiness movement contributed to the development of Pentecostalism by combining Restorationism with the goal of sanctification defined as a deeper spiritual experience.^[556]

This revival focused on evidencing conversion through active moral reform in areas such as women's rights, temperance, literacy, and the abolition of slavery. The pursuit of women's rights established "prayer, worship, and biblical exegesis as weapons of political warfare",^[557] while the accent on human choice and activism influenced evangelicalism thereafter.^{[558][559][560][561]} The 300-year-old trans-Atlantic slave trade, in which some Christians had participated, had always garnered moral objections, and by the eighteenth century, individual Quakers, Methodists, Presbyterians and Baptists began a written campaign against it.^[562] Congregations led by black preachers kept abolitionism alive into the early nineteenth century when some American Protestants organized the first anti-slavery societies.^[563] This ideological opposition eventually ended the trans-Atlantic slave trade, changing economic and human history on three continents.^[564][565]

The Third Great Awakening began in 1857 and took root throughout the world, especially in English-speaking countries.^[560] Nineteenth-century Protestant missionaries, many of them women, played a significant role in shaping nations and societies.^{[566][567][568][550]} They translated the Bible into local languages, generating in the process a written grammar, a lexicon of native traditions, and a dictionary of the local language.^[569] These were used to teach in missionary schools, resulting in the spread of literacy and indigenization.^{[570][571][572]} According to historian Lamin Sanneh, Protestant missionaries thus stimulated the "largest, most diverse and most vigorous movement of cultural renewal" in African history.^{[573][464][574]}

Liberal Christians embraced seventeenth-century rationalism, but its disregard of faith and ritual in maintaining Christianity led to its decline. Fundamentalist Christianity rose in the early 1900s as a reaction against modern rationalism.^[575][576] By 1930, Protestant fundamentalism in America appeared to be dying.^[577][578] However, in the second half of the 1930s, a theology against liberalism that also included a reevaluation of Reformation teachings began uniting moderates of both sides.^[579][580]

The Roman Catholic Church became increasingly centralized, conservative, and focused on loyalty to the Pope.^[528] As Nazism rose, Pope Pius XI declared the irreconcilability of the Catholic position with totalitarian fascist states which placed the nation above God.^[581] Most leaders and members of the largest Protestant church in Germany, the German Evangelical Church, supported the Nazi Party when they came to power in 1933.^[582] About a third of German Protestants formed the Confessing Church which opposed Nazism; its members were harassed, arrested, and otherwise targeted. In Poland, Catholic priests were arrested and Polish priests and nuns were executed en masse.^[583]

The Church reform of Peter I in the early 1700s had placed the Orthodox authorities under the control of the tsar who involved the church in various campaigns of russification which contributed to antisemitism.^[585][586] The communist revolutionaries who established the Soviet Union saw the Church as an enemy of the people and part of the tsarist state.^{[587][588][589][590]} The communist Soviet Union heavily persecuted the Russian Orthodox Church,^[591] executing up to 8,000 people by 1922.^[592] The League of Militant Atheists adopted a five-year plan in 1932 "aimed at the total eradication of religion by 1937".^[593] Despite this, the Orthodox Church continued to contribute to theology and culture.^[594]

Before 1945, about a third of the people in the world were Christians, and about 80% lived in Europe, Russia, and the Americas.^[596] After WWII ended, decolonization strengthened the emancipation efforts of Christian missionaries, leading to explosive growth in the churches of former colonies.^{[597][598][599][600]} In 1900, there were just under nine million Christians in Africa; by 1960, this number had increased to 60 million, and by 2005, to 393 million, about half of the continent's population, a proportion which has remained constant as of 2022.^[569][595] This expansion has been labeled a "fourth great age of Christian expansion".^{[601][note 16]}

Christianity in Southeast and East Asia, especially Korea, grew faster after colonialism.^{[606][607][608]} Rapid expansion began in the 1980s.^[609][610] The Council on Foreign Relations data shows a 10% yearly growth in Chinese Christian populations since 1979, with growth especially prominent among young people.^{[611][612][613]} In Sri Lanka, in 1948, Lakdasa De Mel (1902–1976) was the first native priest to be ordained an Anglican bishop. As bishop, Anglican Metropolitan, and one of the most distinguished Christian leaders in post-war Asia, he funded the Anglican cathedral at Kurunagala, built in 1956, which incorporated indigenous sacred Sinhalese architectural styles, and served as a model for other ecclesiastical buildings.^[614]

With the collapse of communism, Christianity also expanded in Eastern Europe and Russia.^{[597][598][599][600]} Christianity has had multiple regional "centers" since its beginnings, and these have produced different indigenous forms, initiatives, and expressions that have all contributed to its global expansion.^[615] In the first quarter of the twenty-first century, Christianity is present in all six continents and a multitude of different cultures;^[616] most Christians live outside North America and Western Europe; white Christians are a global minority, and slightly over half of worldwide Christians are female.^[617][618] It is the world's largest religion with roughly 2.4 billion followers constituting around 31.2% of the world's population.^{[460][541][619]}

In the twentieth century, Christianity faced the challenges of secularism, and the changing moral climate concerning sexual ethics, gender, and exclusivity, leading to a decline in church attendance in the West.^{[620][621][622]} However, in the late twentieth century, religion around the world left the private sphere and revitalized its public role, undermining theories of secularization.^[623]

In 2000, approximately one-quarter of all Christians worldwide were part of Pentecostalism and its associated movements.^[624] By 2025, Pentecostals are expected to constitute one-third of the nearly three billion Christians worldwide, making it the largest branch of Protestantism and the fastest-growing Christian movement.^[625][626]

The three main branches of Eastern Christianity are the Eastern Orthodox Church, the Oriental Orthodox Communion, and the Eastern Catholic Church.^{[335][333][627]} Roughly half of Eastern Orthodox Christians live in post-Eastern Bloc countries.^[628] Its oldest communities in Jerusalem, Antioch, Alexandria, Constantinople, and Georgia, are decreasing due to forced migration from religious persecution.^[629] Highly authoritarian and totalitarian governments have brought about crises and decline in many areas.^{[630][464][631]} In 2013, 17 Muslim majority states reported discrimination against religious minorities, including Christianity.^[632] Anti-Christian persecution has become a consistent human rights concern.^[633]

Orthodox Christians in the East tend to be more conservative on most issues than Westerners.^[628] Less than four-in-ten Orthodox Christians favor reconciliation with the Roman Catholic Church.^[628] Roman Catholic ecumenical goals are to re-establish full communion amongst all the various Christian churches, but there is no agreement amongst evangelicals.^{[634][635][636]} There is, however, a trend at the local level toward discussion, pulpit exchanges, and shared social action.^[637][638] In Hugh McLeod's view, "A liberal Catholic is likely to have a lot in common with a liberal Methodist," and the influence of the internet will probably increase this.^[639]

For theologians writing after 1945, theology depended on the context of those applying it.^[640] The multiple wars of the twentieth century brought questions of theodicy to the forefront.^[641] For the first time since the pre-Constantinian era, Christian pacifism became an alternative to war.^[642] The Holocaust forced many to realize that supersessionism, a replacement theology begun in Late Antiquity, can underlie hatred, ethnocentrism, and racism. Supersessionist texts are increasingly challenged.^[643]

Liberation theology combined with the social gospel to redefine social justice and expose institutionalized sin to aid Latin American poor, but its context limited its application in other environments.^{[644][645][640]} Different historical and socio-political situations produced black theology and Feminist theology. Combining Christianity with questions of civil rights, aspects of the Black Power movement, and responses to black Muslims produced a black theology that spread to the United Kingdom, parts of Africa, and confronted apartheid in South Africa.^[646][647] The feminist movement of the mid-twentieth century began with an anti-Christian ethos but soon developed an influential feminist theology dedicated to transforming churches and society.^[648][649] Feminist theology developed at the local level as womanist theology of African-American women, the "mujerista" theology of Hispanic women, and Asian feminist theology.^[650]

In the mid to late 1990s, postcolonial theology emerged globally from multiple sources.^[651] It analyzes structures of power and ideology to recover what colonialism erased or suppressed in indigenous cultures.^[652] The missionary movement of the twenty-first century has transformed into a multi-cultural, multi-faceted global network of NGO's, short-term amateur volunteers, and traditional long-term bilingual, bicultural professionals who focus on evangelism and local development.^[653][654]

• Historical background of the New Testament
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