Christianity: From a Galilean Teacher to More Than Two Billion People

Follows: The World's Religions, One Page Each and How the Sacred Texts Were Written. Companion pieces: the Most Influential Mystics pieces on Meister Eckhart, Teresa of Ávila, John of the Cross and Julian of Norwich; the Religions long reads on Judaism, Islam and Religion in the Modern Age; and, in Spanish, El Auge Evangélico en América Latina.

On a Sunday morning, somewhere around the world, the same short meal is being eaten in thousands of languages. In a cathedral in Lagos it comes with drums. In a Russian village church it is spooned to the faithful from a golden chalice after three hours of standing. In a Baptist chapel in Texas it is a cube of bread and a tiny cup of grape juice passed along the pews. In a Pentecostal warehouse church in São Paulo it may be skipped altogether in favour of an hour of singing, prayer for healing and speaking in tongues. All of these people would tell you they are doing what a Galilean teacher asked of his friends on the night before he died: "this do in remembrance of me" (Luke 22:19).

That is the puzzle this long read tries to explain. How did a movement that began with a few dozen Jews in a corner of the Roman Empire, following a man the empire had crucified, become a faith of about 2.3 billion people, according to the Pew Research Center's 2025 count, spread across every continent and split into tens of thousands of churches? And how did it become, in the same two thousand years, both a source of hospitals, universities, abolitionism and some of humanity's greatest art, and an institution that blessed crusades, ran inquisitions, baptised conquest and hid the abuse of children?

A note on approach: this piece describes what Christians believe in their own terms, and beside it what historians say, keeping the two clearly apart and treating both with respect. It does not try to prove or disprove the faith. Christians disagree with each other on almost every point below, and Catholics, Orthodox, Protestants and Pentecostals are each described as their own members would recognise. Bible quotations are from the King James Version (1611), which is in the public domain.

In this long read

1. Two ways to tell the story: the Jesus of faith and the Jesus of history
2. Paul and the first communities (c. 30–150)
3. From persecution to empire: Constantine, councils and creeds (150–451)
4. How the Bible was assembled
5. Monks, the medieval church and the split of East and West (500–1453)
6. Crusades and inquisitions: what happened and what historians now say
7. The Reformations (1517–1648)
8. Missions and empire: harm and agency
9. The Orthodox world
10. Reason, criticism and the Bible (1650–1950)
11. Slavery: Christian abolitionists and a complicit church
12. The twentieth century: Pentecostal fire, the Global South and Vatican II
13. What Christians actually do: sacraments, prayer and the year
14. Christianity in 2026: abuse, the papacy and the numbers

Part 1 — Two ways to tell the story: the Jesus of faith and the Jesus of history

The Gospels' account

The four Gospels, Matthew, Mark, Luke and John, tell a story that Christians read not as a biography but as good news (gospel comes from the Old English for "good tidings"). Jesus is born to Mary, a young Jewish woman, in the days of King Herod; Matthew and Luke say she conceived him without a human father. He grows up in Nazareth, a village in Galilee. As an adult he is baptised by a fiery prophet, John the Baptist, and begins to preach. Mark's Gospel sums up the message in one line:

"The time is fulfilled, and the kingdom of God is at hand: repent ye, and believe the gospel." — Mark 1:15

He gathers disciples, twelve of them chosen as an inner circle. He heals the sick, casts out demons, eats with tax collectors and prostitutes, and tells parables: the prodigal son welcomed home, the Samaritan who stops for a beaten stranger, the mustard seed that grows into a tree. In the Sermon on the Mount he blesses the poor in spirit and the meek and tells his hearers: "Love your enemies, bless them that curse you" (Matthew 5:44). Asked which commandment is greatest, he joins two from the Hebrew Bible: love God with all your heart, soul, mind and strength, and "love thy neighbour as thyself" (Mark 12:30–31).

He goes up to Jerusalem for Passover, overturns the tables of the money-changers in the Temple, shares a last supper with his disciples, is betrayed by one of them, arrested, tried before the Jewish high priest and the Roman governor Pontius Pilate, and crucified. On the third day, the Gospels say, women going to anoint his body find the tomb empty, and he appears to his followers alive. For Christians this is the centre of everything: the resurrection shows that Jesus is the Messiah (in Greek, Christos, "anointed one") and the Son of God, and that through his death and rising, sin and death have been defeated. John's Gospel opens with the boldest claim of all, that Jesus is God's own Word made human: "In the beginning was the Word, and the Word was with God, and the Word was God" (John 1:1).

What historians say

Historians work differently. They cannot test a resurrection or a virgin birth, which are claims of faith, so they ask a narrower question: what can be said about Jesus of Nazareth using the ordinary methods applied to any ancient figure?

The first answer is that he existed. Virtually all scholars of antiquity, Christian, Jewish and secular, accept that Jesus was a real person; the theory that he was invented is a fringe position. Beyond the Gospels and Paul's letters, the evidence includes two Roman writers. The historian Tacitus, writing around 115, explains that the emperor Nero blamed the great fire of Rome on a hated group "called Christians by the populace", and that their founder, Christus, "suffered the extreme penalty during the reign of Tiberius at the hands of one of our procurators, Pontius Pilatus" (Annals 15.44). Pliny the Younger, governor of Bithynia in what is now Turkey from about 111 to 113, wrote to the emperor Trajan that Christians met before dawn on a fixed day to sing "a hymn to Christ as to a god" (Letters 10.96). The Jewish historian Josephus also mentions Jesus, though the main passage was later expanded by Christian copyists and scholars argue over what he originally wrote.

The second answer is that only a few events are close to certain. Almost all historians accept that Jesus was baptised by John and crucified on Pilate's orders, because these are things early Christians would hardly have invented: a sinless saviour submitting to a baptism of repentance, and a Messiah dying the death reserved for rebels and slaves. Pilate governed Judea from about 26 to 36 CE, and most scholars put the crucifixion around 30 or 33. Matthew dates the birth to the reign of Herod the Great, so most historians place it a few years "before Christ", around 6–4 BCE: the calendar that counts years from his birth was worked out centuries later and missed by a few years.

That dating comes from mainstream New Testament scholarship, as summarised, for example, by L. Michael White for the PBS series From Jesus to Christ: Mark first, around 70; Matthew and Luke a decade or two later, both using Mark and, many scholars think, a lost collection of sayings they call "Q"; John last, around 95. Some scholars, especially conservative ones, date them earlier; a few date them later.

Three quests, and a Jewish Jesus

Since the 18th century, scholars have made repeated "quests" for the historical Jesus. The first, ending with Albert Schweitzer's The Quest of the Historical Jesus (1906), found that each generation had painted a Jesus who looked like itself: a rational moralist for Enlightenment readers, a gentle romantic for the Victorians. Schweitzer's own Jesus was stranger: a prophet who expected the world to end soon.

The most important change since the 1970s has been the recovery of Jesus the Jew. Scholars such as E. P. Sanders, Géza Vermes and Paula Fredriksen insist that he must be understood inside the Judaism of his time: a Galilean who kept the Sabbath, went to the Temple for the festivals, argued about the Law as other teachers did, and spoke of a kingdom God was about to bring. This matters because for most of Christian history the Gospels' conflict stories were read as "Jesus against the Jews", and that reading fed centuries of contempt (see Part 12 on what the Catholic Church said about this in 1965).

The historian and the believer are not always asking the same question. One asks "what can the evidence show?"; the other, "who is this for me?" Both questions are honest, and neither answers the other.

Many Christians hold that the Jesus of history and the Christ of faith are the same person seen from two angles. Some scholars are believers, some are not, and the field includes both. What it does not support is either extreme: that nothing can be known, or that the Gospels can be read as a modern news report.

Part 2 — Paul and the first communities (c. 30–150)

The earliest Christian writings are not the Gospels but the letters of Paul, written roughly twenty years after the crucifixion. Paul, a Greek-speaking Jew and, by his own account, a Pharisee from Tarsus, had persecuted the new movement until, he says, the risen Christ was revealed to him; Acts describes "a light from heaven" on the road to Damascus (Acts 9:3). He then spent his life founding small house churches around the eastern Mediterranean and writing to them.

Of the thirteen letters that carry his name, scholars broadly agree that seven are his: Romans, 1 and 2 Corinthians, Galatians, Philippians, 1 Thessalonians and Philemon, all usually dated to the 50s. The others are disputed; many scholars think followers wrote them in his name, a common practice in the ancient world, while others defend Paul's authorship. In 1 Corinthians Paul passes on a creed he says he himself had received, which takes us back very close to the beginning:

"Christ died for our sins according to the scriptures; and that he was buried, and that he rose again the third day according to the scriptures." — 1 Corinthians 15:3–4

The great argument: did Gentiles have to become Jews?

The first Christians were Jews who believed the Messiah had come. The explosive question was whether non-Jews who joined had to keep the Law of Moses: circumcision for men, the food laws, the Sabbath. Paul said no. A meeting in Jerusalem, usually dated around 48–50 and described in Acts 15 and Galatians 2, agreed, with some conditions, that Gentile converts need not be circumcised. Paul's letter to the Galatians gives his vision:

"There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female: for ye are all one in Christ Jesus." — Galatians 3:28

That decision turned a Jewish renewal movement into something that could spread among any people. It also set Christianity on the path to separation from Judaism, a parting that happened slowly, unevenly and painfully over the following century, especially after the Romans destroyed the Jerusalem Temple in 70.

What the first churches were like

Acts paints an idealised picture of the Jerusalem community: "all that believed were together, and had all things common" (Acts 2:44). The letters show something messier: quarrels over leadership, over eating meat offered to idols, over the role of women, over whether the end was imminent. Followers were first "called Christians" in Antioch (Acts 11:26). They met in homes, shared a common meal that became the Eucharist, baptised converts, cared for widows and the poor, and expected Christ's return.

How fast did they grow? Nobody knows. The sociologist Rodney Stark, in The Rise of Christianity (1996), argued that steady compound growth, through family and friendship networks and through Christians' care for the sick during epidemics, could explain the church's rise without any mass conversions. Historians debate his numbers, but his central point, that Christianity spread mostly person to person, is widely shared.

Part 3 — From persecution to empire: Constantine, councils and creeds (150–451)

Persecution

For its first two and a half centuries Christianity was an illegal and suspect religion. Persecution was local and intermittent rather than constant: Nero's in Rome after the great fire of 64, Pliny's trials in Bithynia, outbreaks of mob violence in particular cities. Christians refused to sacrifice to the gods or to the emperor's spirit, which looked to Romans like atheism and disloyalty. Empire-wide campaigns came later, under Decius in the 250s and above all the "Great Persecution" launched by Diocletian in 303, when churches were destroyed and scriptures burned. The memory of the martyrs (the word means "witnesses") became central to Christian identity: their tombs became shrines, and their feast days filled the calendar.

Constantine

Then, within a decade, everything changed. In 311 the emperor Galerius issued an edict of toleration. In 312 Constantine, fighting for control of the western empire, defeated his rival Maxentius at the Milvian Bridge outside Rome on 28 October, after, by the Christian accounts, seeing a sign of the cross and putting Christ's monogram on his soldiers' shields. In 313 he and his co-emperor Licinius agreed the policy known as the Edict of Milan, granting freedom of worship to Christians and everyone else and ordering confiscated church property returned. Constantine was baptised only on his deathbed in 337.

Historians still argue about how sincere his conversion was and what it meant. What is clear is the result: bishops gained imperial favour, money and buildings; Sunday became a public day of rest; and the church, once persecuted, became tied to power. In 380 the emperor Theodosius I decreed that all his subjects should follow the faith "delivered to the Romans by the divine Apostle Peter" and branded dissenters heretics. Within a few years pagan sacrifice was banned. The persecuted had become the established.

The councils and the creeds

With imperial support came imperial pressure to settle disputes. The biggest was about who Jesus was. An Alexandrian priest named Arius taught that the Son was the first and greatest of God's creatures, but not eternal like the Father. His bishop, Alexander, disagreed, and the quarrel split the eastern church. Constantine called the bishops to Nicaea (now İznik in Turkey) in 325; tradition counts 318 of them. The council declared the Son "of one substance" (in Greek homoousios) with the Father and produced a creed. The Council of Constantinople in 381 affirmed the divinity of the Holy Spirit, and the expanded creed associated with it, the "Nicene Creed" said in churches every Sunday, is still the one statement of faith shared by Catholics, Orthodox and most Protestants.

The next fight was over how Christ could be both God and man. The Council of Ephesus (431) rejected the teaching associated with Nestorius, bishop of Constantinople, and approved calling Mary Theotokos, "God-bearer". The Council of Chalcedon (451) defined Christ as one person "in two natures", divine and human, united without confusion or change and without division or separation.

Chalcedon caused the first lasting split. Churches in Egypt, Ethiopia, Syria and Armenia rejected its "two natures" formula as a betrayal of the earlier teaching of Cyril of Alexandria, insisting on one united nature of the incarnate Word. Their opponents called them "Monophysites"; they call themselves the Oriental Orthodox churches (Coptic, Ethiopian, Eritrean, Armenian, Syriac and Malankara), and many of their theologians today say the dispute was largely about words. Further east, the Church of the East, rooted in Persia and later reaching China and India, followed a theology closer to Nestorius's. These are not breakaways from "real" Christianity but some of its oldest branches, older in their lands than the Christianity of most of Europe.

Part 4 — How the Bible was assembled

How the Sacred Texts Were Written, in this library, tells the general story; here are the Christian specifics.

The first Christians' Bible was the Jewish scriptures, mostly read in Greek translation. Their own writings, letters and Gospels, circulated for decades before anyone asked which of them counted as scripture alongside the old. The question was forced by rivals. Around 144 a wealthy shipowner named Marcion founded a church in Rome that rejected the Jewish scriptures and the God they described, and accepted only an edited Gospel of Luke and ten of Paul's letters. Mainstream bishops answered by insisting on the old scriptures and on four Gospels, no more and no fewer; Irenaeus of Lyon, around 180, argued for exactly four. Other groups produced other gospels, such as the Gospel of Thomas, a collection of sayings, some of which were rediscovered in Egypt in 1945.

In his 39th Festal Letter of 367, Athanasius, bishop of Alexandria, listed the four Gospels, Acts, seven "catholic" letters, fourteen of Paul (counting Hebrews) and Revelation: the 27 books of today's New Testament. The process was not a single vote but a slow convergence on books that were old, linked to apostles, widely used in worship and consistent with the "rule of faith". Some books, such as Hebrews, James, 2 Peter and Revelation, were long disputed, and some churches, especially in the East, kept slightly different collections for centuries.

The Old Testament differs too. Catholics and Orthodox include books such as Tobit, Judith and the Maccabees that were in the Greek Jewish scriptures; Protestants, following Luther, use only the books of the Hebrew Bible and call the rest the Apocrypha.

Part 5 — Monks, the medieval church and the split of East and West (500–1453)

Into the desert

As Christianity became respectable, some Christians fled respectability. In Egypt, Anthony went into the desert to live in prayer and fasting; his biography by Athanasius made him famous across the empire, and by his death, which St Jerome put at 356–357, thousands had followed him. Pachomius organised monks into communities under a rule. In the West, Benedict of Nursia (c. 480–543) wrote a short Rule for his monastery at Monte Cassino that balanced prayer, work and study, and it became the pattern for Western monastic life. Its first word is "Listen".

For the next thousand years monasteries were the West's libraries, schools, hospitals, farms and hostels. Monks copied the classical texts that survived the fall of Rome. Irish monks carried the faith and Latin learning back to a Europe that had half-forgotten both. Later, the friars, Franciscans and Dominicans, took the religious life out of the cloister and into the towns, and Dominican scholars such as Thomas Aquinas built the great intellectual systems of the medieval universities.

The mystical tradition grew in this soil. The library's pieces on the Dominican Meister Eckhart, the anchoress Julian of Norwich, and, later, the Spanish Carmelites Teresa of Ávila and John of the Cross show what it produced: maps of the soul's journey to union with God that still guide Christian contemplatives.

Two churches drifting apart

The Roman Empire split into a Latin-speaking West and a Greek-speaking East, and so, slowly, did the church. The West, after Rome fell, looked to the pope as the one stable authority. The East had an emperor in Constantinople and a tradition of governing the church through councils of bishops, with the pope honoured as first among the patriarchs but not as their ruler. They argued about whether the Western churches could add the word Filioque, "and the Son", to the Nicene Creed, so that the Spirit "proceeds from the Father and the Son"; about leavened or unleavened bread at the Eucharist; about clerical celibacy; and above all about papal authority.

On 16 July 1054 the pope's legate, Cardinal Humbert, laid a bull excommunicating Patriarch Michael Cerularius on the altar of Hagia Sophia; the patriarch and his synod excommunicated the legates in return. At the time few thought this was final, and historians now see 1054 less as the moment of schism than as a symbol of a long estrangement. What made it permanent was violence: in 1204 the knights of the Fourth Crusade, diverted from the Holy Land, sacked Constantinople, Christian against Christian, and set up a Latin empire there. Attempts at reunion, notably at the Council of Florence in 1439, failed, and in 1453 Constantinople fell to the Ottoman Turks.

In 1965 Pope Paul VI and Patriarch Athenagoras of Constantinople issued a joint declaration lifting the excommunications of 1054 and committing them, in its words, "to oblivion". The churches remain separate, but they speak of each other as "sister churches".

"They commit these excommunications to oblivion."
— Joint Catholic-Orthodox Declaration of Pope Paul VI and Patriarch Athenagoras I, 7 December 1965

The medieval Western church

At its height, the medieval Latin church was the most powerful institution in Europe. It was a great landowner, ran most of the schools, kept the records of birth, marriage and death, and claimed authority over kings. Popes such as Gregory VII (in the 11th century) and Innocent III (in the 13th) fought emperors over who appointed bishops. Ordinary life was shaped by the parish, the saints' days, pilgrimages (see Pilgrimage: Why Humans Walk to Holy Places) and the sacraments. The church also produced the cathedrals of Chartres and Cologne, the universities of Paris, Oxford and Bologna, the hospital as an institution, and much of the art and music Europe is still proud of.

Part 6 — Crusades and inquisitions: what happened and what historians now say

Few subjects are as wrapped in myth, from both directions, as these. Here is what happened, and how scholars have revised the popular picture.

The Crusades

In November 1095, at Clermont in France, Pope Urban II called on Western knights to go to the aid of the Byzantine Christians against the Seljuk Turks and to free Jerusalem, promising remission of sins to those who went. The response astonished everyone. Armies marched east; on the way, some bands massacred the Jewish communities of the Rhineland. In July 1099 the crusaders took Jerusalem and killed much of its population, Muslim and Jewish. They set up "crusader states" along the coast of the Levant, which lasted until the fall of Acre in 1291. Later crusades were aimed at Muslims in Spain, pagans around the Baltic, heretics in southern France, and the pope's political enemies; the Fourth sacked Christian Constantinople.

How historians see it has shifted:

None of these revisions makes the massacres less real. On 12 March 2000, in a "Day of Pardon" Mass, Pope John Paul II asked forgiveness for "the violence some have used in the service of the truth" and for hostility towards followers of other religions, without naming each case; Christians and others still debate whether that was enough.

The inquisitions

"The Inquisition" was not one thing. The medieval inquisition grew from the 1180s as bishops and then papally appointed judges, often Dominican or Franciscan friars, were charged with hunting heresy, especially the Cathars of southern France. Inquisitors could use torture (authorised by Pope Innocent IV in 1252) and hand the unrepentant to the secular authorities for burning.

The Spanish Inquisition was different: a royal tribunal, set up with papal permission granted by Sixtus IV on 1 November 1478 at the request of Ferdinand and Isabella, and controlled by the crown. Its first targets were conversos, Jews who had converted to Christianity, often under pressure, and who were suspected of secretly keeping Jewish practices; later, moriscos (converted Muslims), Protestants, and people accused of blasphemy or sexual offences. It was suppressed and restored several times before its final abolition in the early 19th century. A 2021 study in PNAS assembled records of more than 67,000 of its trials between 1480 and 1820, and found that Spanish towns where it was most active have lower trust, schooling and income today. The Roman Inquisition, founded by Paul III in 1542 to fight Protestantism, is the body that tried Galileo in 1633.

The revision here, led by historians such as Henry Kamen (The Spanish Inquisition: A Historical Revision), is about scale and character, not innocence. The trial records show that most cases ended in penances, fines or reconciliation rather than death, and that executions were heaviest in the tribunal's first decades. Most scholarly estimates put the total executed by the Spanish Inquisition in the low thousands over three and a half centuries, not the hundreds of thousands of legend; the exact figure is disputed. At the same time, the institution terrorised Spain's converso and morisco families, encouraged denunciation by neighbours, made "purity of blood" a condition for many offices, and censored books for centuries. Both things are true.

Revisionist history is not apologetics. Smaller numbers do not make a burning less of a burning; they make the past more accurate.

In 1998 the Vatican convened historians for a symposium on the inquisitions. When the proceedings were published in 2004, John Paul II wrote that "before asking for forgiveness it is necessary to have exact knowledge of the facts."

Part 7 — The Reformations (1517–1648)

Luther

By 1500 many Western Christians wanted reform: of corrupt and absent clergy, of a papacy behaving like an Italian principality, of the sale of indulgences, certificates said to reduce time in purgatory for oneself or a dead relative. On 31 October 1517, by long tradition, Martin Luther, an Augustinian friar and professor at Wittenberg in Saxony, posted 95 theses against indulgences on the door of the castle church (some historians doubt the posting; it is certain that he sent the theses to the archbishop of Mainz that day). The printing press spread them across Germany within weeks.

At the root of Luther's protest was a spiritual discovery from Paul's letter to the Romans: "The just shall live by faith" (Romans 1:17). Salvation, he concluded, is a free gift of God's grace received through faith, not something earned by good works or bought from the church. Scripture, not popes or councils, is the final authority (sola scriptura), and every baptised Christian is a priest before God. Summoned before the emperor Charles V at the Diet of Worms in 1521, Luther refused to recant. Hidden in the Wartburg castle by his prince, he translated the New Testament into German, published in 1522. Catholics answered with the Letter of James: "faith, if it hath not works, is dead" (James 2:17), a letter Luther ranked below the New Testament's chief books, placing it near the end of his 1522 translation.

Calvin, the radicals and England

The Reformation quickly became several reformations.

• The Reformed tradition. In Zurich, Huldrych Zwingli went further than Luther, treating the Lord's Supper as a memorial rather than a real presence of Christ's body. In Geneva, the French lawyer John Calvin (1509–1564) wrote the Institutes of the Christian Religion (first edition 1536, final Latin edition 1559), stressing God's sovereignty and predestination, and built a disciplined city church. Calvinism spread to Scotland (Presbyterians), the Netherlands, Hungary, France (the Huguenots) and, through the Puritans, New England.
• The Anabaptists ("re-baptisers") argued that baptism should be for believers who chose it, not infants, and that the church should be a voluntary community separate from the state. In Zurich in January 1525 a group around Conrad Grebel baptised each other, and in 1527 the Schleitheim Confession set out their principles, including refusal of oaths and of the sword. Catholics and Protestants alike drowned, burned and beheaded them by the thousands. A violent apocalyptic takeover of the city of Münster (1534–35) was used to tar the whole movement, though most Anabaptists were pacifists. Their heirs, the Mennonites, Amish and Hutterites, pioneered ideas, such as the separation of church and state and freedom of conscience, that later became mainstream.
• England. Henry VIII broke with Rome when the pope would not annul his marriage to Catherine of Aragon; the Act of Supremacy made the king head of the Church of England. Under his son Edward VI the church became more Protestant, with Thomas Cranmer's Book of Common Prayer; under Mary I it returned to Rome, and hundreds of Protestants were burned; under Elizabeth I, from 1558, a settlement emerged that the Church of England describes as both "catholic and reformed", the ancestor of today's worldwide Anglican Communion.

The Catholic Reformation

Rome's response used to be called the "Counter-Reformation", as if it were only a reaction. Historians now prefer "Catholic Reformation", because reform movements inside the church were already under way. The Council of Trent (13 December 1545 to 4 December 1563) restated Catholic doctrine against the Protestants, on scripture and tradition together, the seven sacraments, the Mass as sacrifice and justification, and also cracked down on abuses, requiring seminaries to train priests and bishops to live in their dioceses. New orders brought fresh energy: the Society of Jesus (the Jesuits), approved by Paul III on 27 September 1540, became the church's teachers and missionaries. Teresa of Ávila's reform of the Carmelites, described in this library, belongs to this moment too, as does the Roman Inquisition and the Index of Forbidden Books.

Wars of religion

The splits were not only theological. Princes chose churches for their territories; the Peace of Augsburg (1555) let each German ruler decide whether his lands were Lutheran or Catholic. Religious wars tore through France, the Netherlands and the German lands, ending with the Thirty Years' War and the Peace of Westphalia in 1648, after which European states largely stopped fighting each other over doctrine. The exhaustion of those wars is one root of the modern idea of religious toleration.

Part 8 — Missions and empire: harm and agency

From the 1490s Christianity travelled with European ships, and the story of how it spread across the Americas, Africa and Asia is both a story of conquest and a story of peoples who took the faith and made it their own.

The harm

In 1493, a year after Columbus's first voyage, Pope Alexander VI issued bulls dividing newly found lands between Spain and Portugal; jurists later built on such texts the so-called "doctrine of discovery", used to claim that Christian nations could take land from non-Christian peoples. Spanish conquistadors read out a demand, the Requerimiento, telling indigenous people to accept the pope and the king or face war and enslavement. Forced labour and imported disease killed a very large share of the native population of the Americas. Missionaries often supported colonial rule, destroyed sacred objects and suppressed languages, and in later centuries churches ran residential and boarding schools designed to separate indigenous children from their cultures.

In Canada, more than 150,000 First Nations, Inuit and Métis children attended residential schools, most run by churches for the federal government; the first church-run school opened in 1831. Canada's Truth and Reconciliation Commission, which finished its work in 2015, documented abuse, neglect and thousands of deaths. In July 2022 Pope Francis travelled to Canada and apologised in person. In March 2023 the Vatican issued a statement saying that the "doctrine of discovery" "is not part of the teaching of the Catholic Church", that the papal bulls "did not adequately reflect the equal dignity and rights of indigenous peoples", and that the church "repudiates" such concepts.

The critics inside

From the start, some missionaries were the conquest's fiercest critics. In 1511 the Dominican Antonio de Montesinos preached in Hispaniola that the colonists were in mortal sin for their cruelty. Bartolomé de las Casas, a former colonist turned Dominican friar, spent fifty years documenting atrocities in his Brief Account of the Destruction of the Indies and arguing, at a famous debate in Valladolid in 1550–51 against Juan Ginés de Sepúlveda, that indigenous people were fully rational human beings with rights. The Jesuits built mission towns, the reducciones, in Paraguay that protected Guaraní communities from slavers (and also organised their lives on Jesuit terms). Matteo Ricci, a Jesuit who reached Beijing and died there in 1610, learned classical Chinese, dressed as a scholar and tried to present Christianity in Confucian terms.

The agency of converts

The other half of the story, emphasised by historians such as Lamin Sanneh and Andrew Walls, is that Christianity spread most of all through local people, often far from missionary control.

• Translation. Missionaries translated the Bible into hundreds of languages, and Sanneh argued in Translating the Message (1989) that this had an unintended effect: it dignified local languages and cultures, and gave converts the tools to judge missionaries by their own scriptures.
• African prophets. In 1913 William Wadé Harris, a Liberian Grebo, walked into the Ivory Coast preaching, dressed in white with a cross and a Bible, and more than 100,000 people were baptised within about eighteen months, before most had met a European missionary. In 1921, in the Belgian Congo, Simon Kimbangu, a Baptist catechist, began a healing and preaching mission that became a mass movement; the colonial authorities imprisoned him for the rest of his life, but the church that bears his name became one of the largest African-founded churches and later joined the World Council of Churches.
• African-initiated churches, from the Aladura churches of Nigeria to the Zion Christian Church in South Africa, blended Christian faith with African forms of prayer, healing and prophecy, and are now among the continent's largest denominations.

Christianity arrived in much of the world on colonial ships. It stayed, and grew, after the ships left, because Africans, Asians and Latin Americans made it their own.

The two stories do not cancel each other. A Kenyan or Filipino Christian today may hold both: grief at what colonial Christianity did, and conviction that the faith itself was a gift that their own people carried furthest.

Part 9 — The Orthodox world

For many Western readers, Christian history is Rome and the Reformation. For about 260 million Orthodox Christians, the Pew Research Center's 2017 estimate, it runs through Constantinople, Kyiv, Moscow, Alexandria and Addis Ababa.

What the Orthodox believe. The Eastern Orthodox churches see themselves as the one church of the apostles, continuous and unchanged in faith, holding to the seven ecumenical councils from Nicaea (325) to Nicaea II (787). They are a family of self-governing ("autocephalous") churches, among them Constantinople, Alexandria, Antioch, Jerusalem, Russia, Serbia, Romania, Bulgaria, Georgia and Greece, united in faith and worship rather than under one head; the Ecumenical Patriarch of Constantinople is honoured as first among equals. Orthodox theology stresses theosis, the transformation of human beings by grace into partakers of God's life; icons, defended at the Second Council of Nicaea as windows onto heaven, not idols; and the Divine Liturgy, often sung, long and largely unchanged since the time of St John Chrysostom.

Kyiv and Moscow. In 988, by the traditional account, Prince Vladimir of Kyiv was baptised and had his people baptised, after envoys he had sent to inspect the religions of his neighbours came back overwhelmed by the beauty of the Greek liturgy in Constantinople's Hagia Sophia. After Constantinople fell in 1453, Russian churchmen spoke of Moscow as a "Third Rome". Under the Ottomans, Orthodox Christians in the Balkans and the Middle East lived for centuries as a protected but subordinate community. In the 20th century, the Soviet state closed most churches and killed or imprisoned many thousands of clergy; after 1991 the Russian Orthodox Church revived dramatically.

Ukraine. In January 2019 the Ecumenical Patriarch granted independence (a tomos of autocephaly) to a new Orthodox Church of Ukraine; the Moscow Patriarchate, which had already broken communion with Constantinople over the plan in 2018, rejected it. Since Russia's full-scale invasion of Ukraine in 2022, Patriarch Kirill of Moscow's support for the war has deepened the divide, both within Ukraine and across world Orthodoxy. Supporters of the Moscow Patriarchate argue that it defends canonical order and the historic unity of the Rus' church; supporters of the Orthodox Church of Ukraine argue that an independent nation has a right to an independent church, free of a Moscow hierarchy that blesses the invasion. The dispute is live.

Ethiopia. The Ethiopian Orthodox Tewahedo Church, one of the Oriental Orthodox family, traces its Christianity to the 4th-century kingdom of Aksum. Pew's 2017 survey found Ethiopian Orthodox Christians among the most observant Christians in the world. Its estimated 36 million members make it the largest Orthodox population outside Eastern Europe, about 14 percent of all Orthodox Christians. Orthodoxy overall, Pew found, has shrunk as a share of Christians, from about 20 percent in 1910 to 12 percent, because other branches grew faster.

Part 10 — Reason, criticism and the Bible (1650–1950)

The wars of religion left many Europeans wanting a faith that reason could referee. In the 17th and 18th centuries, philosophers such as Spinoza questioned whether Moses wrote the first five books of the Bible; English Deists argued for a reasonable God who made the world and left it to its laws; Voltaire attacked the church's power; and Thomas Jefferson later assembled his own version of the Gospels with the miracles left out. Others, such as John Locke, argued that Christianity itself was reasonable, and many leading scientists of the age, Newton among them, were devout.

Reading the Bible as a historical book

In the 19th century, German universities developed historical criticism: reading the Bible with the same tools as any ancient text. In 1835 David Friedrich Strauss's Life of Jesus treated the Gospel miracles as myth, and cost him his career. Scholars proposed that the first five books of the Bible were woven together from several earlier sources (the "documentary hypothesis", in its classic form by Julius Wellhausen), that Mark was the first Gospel, and that the Gospels show the theology of their communities. In 1859 Charles Darwin's On the Origin of Species offered a natural account of the variety of life that seemed to many to undercut Genesis.

Christians responded in at least three ways, and all three are still present:

The Catholic Church, battered by revolution and the loss of the Papal States, turned inward. The First Vatican Council defined papal infallibility in the constitution Pastor aeternus (18 July 1870): when the pope speaks ex cathedra to define a doctrine of faith or morals, Catholics hold that he is protected from error. In 1907 Pius X's encyclical Pascendi condemned "modernism", and suspected scholars were silenced. Then the tide turned: in 1943 Pius XII's Divino Afflante Spiritu encouraged Catholic scholars to study the Bible's original languages and literary forms, and the Second Vatican Council's Dei Verbum (18 November 1965) taught that "God speaks in Sacred Scripture through men in human fashion", so that readers must ask what the human writers really meant.

The question every Christian tradition has had to answer since 1800 is not whether the Bible was written by human beings, but what follows if it was.

Today most mainline Protestant, Catholic and Orthodox scholars use critical methods while holding to the creeds; many evangelicals accept much critical scholarship while defending the Bible's reliability; and a large share of Christians worldwide read the Bible in a more direct, literal way. Many Christian thinkers, from Augustine onwards, have also argued that faith and science answer different questions and need not compete.

Part 11 — Slavery: Christian abolitionists and a complicit church

Christianity's record on slavery is one of the clearest examples of a tradition arguing with itself, using the same Bible on both sides.

Complicity

For most of Christian history, churches accepted slavery as part of the social order. The New Testament tells slaves to obey their masters (Ephesians 6:5) and nowhere demands abolition. Papal bulls of the 15th century, such as Dum Diversas (1452), gave the Portuguese crown sweeping rights over the lands and persons of non-Christians, and Catholic and Protestant powers alike built the Atlantic slave trade, which carried some 12.5 million Africans across the ocean. (There were dissenting voices: in 1537, in the bull Sublimis Deus, Paul III declared that the peoples of the Americas were not to be deprived of their liberty, "nor should they be in any way enslaved", a ruling widely ignored.) Churches owned enslaved people directly. The Anglican missionary Society for the Propagation of the Gospel ran the Codrington plantations in Barbados, inherited in 1710. In 1838 the Maryland Jesuits, whose province ran Georgetown University, sold 272 enslaved people to two Louisiana planters; Georgetown, prompted by a 2019 student referendum, now funds projects with the descendants' communities. In the American South, preachers defended slavery from the Bible, and the Southern Baptist Convention was founded in 1845 after a split over whether slaveholders could be missionaries. In 1995 the Convention formally apologised, acknowledging "the role that slavery played in the formation of the Southern Baptist Convention".

Abolition

And yet the movement that ended the Atlantic slave trade was, to a striking degree, a Christian movement. Quakers in Germantown, Pennsylvania, drafted one of the first written protests against slavery in the Americas in 1688, and Quakers were the backbone of the British campaign that formed in 1787. Evangelicals such as William Wilberforce and the "Clapham Sect" led the parliamentary fight that produced the Slave Trade Act of 1807 and the Slavery Abolition Act of 1833. Former slaves who were Christians, such as Olaudah Equiano in Britain and Frederick Douglass, Sojourner Truth and Harriet Tubman in the United States, gave the movement its moral force. Abolitionists appealed to the creation of all people in God's image, to the Exodus, and to Paul's "neither bond nor free". Black churches, founded because white churches excluded or segregated them, became the institutional heart of the later civil rights movement led by a Baptist minister, Martin Luther King Jr.

Douglass, who had been enslaved by men who prayed, drew the line himself in the appendix to his Narrative (1845):

"between the Christianity of this land, and the Christianity of Christ, I recognize the widest possible difference" — Frederick Douglass

Historians weigh the two sides differently. Some stress that Christianity supplied the arguments that finally made slavery unthinkable in societies where it had seemed natural; others stress that it took eighteen centuries, and that the institutions profited until the end. Both are telling true parts of the story.

Part 12 — The twentieth century: Pentecostal fire, the Global South and Vatican II

Pentecostalism

In April 1906, at the Apostolic Faith Mission at 312 Azusa Street in Los Angeles, an African-American preacher named William J. Seymour led a revival in which Black and white, rich and poor worshipped together, and people spoke in tongues, prophesied and reported healings. Within eighteen months, the World Council of Churches notes, Azusa Street had sent evangelists across North America and missionaries to Europe, Africa and Asia. Independent Pentecostal churches arose in Chile (1910) and elsewhere in Latin America without North American missionaries, and the movement grew enormously across Africa and Asia; Yoido Full Gospel Church in Seoul is usually described as the largest single Pentecostal congregation in the world.

Pentecostals believe that the gifts of the Holy Spirit described in the New Testament, speaking in tongues, healing, prophecy, are meant for Christians today, received in a "baptism in the Spirit" after conversion. Worship is emotional, participatory and often loud. Later in the century a "charismatic renewal" brought the same experiences into Catholic, Anglican and Lutheran churches. Counting is hard, but the Center for the Study of Global Christianity at Gordon-Conwell estimates 644 million Pentecostal and charismatic Christians in 2020, about 26 percent of all Christians, a movement that barely existed in 1900. (The count includes charismatic Catholics and Protestants, so it overlaps the other branches.)

Critics, including many Christians, worry about the "prosperity gospel" preached in some Pentecostal churches, the teaching that faith brings wealth and health, and about pastors who become wealthy celebrities. Defenders point to churches that give poor people dignity, community, sobriety and a voice, often led by women and the poor themselves. The sociologist Harvey Cox, in Fire from Heaven (1994), called it the reshaping of religion in the 21st century.

The centre moves south

In 1910, two-thirds of the world's Christians lived in Europe and about 1 percent in sub-Saharan Africa. By 2020, Pew found, sub-Saharan Africa held 31 percent of all Christians and Europe 22 percent; Latin America and the Caribbean held another 24 percent. Africa now has more Catholics than Europe: 288 million against 287 million at mid-2024, according to the Vatican's statistics. The historian Philip Jenkins called this The Next Christendom (2002). A typical Christian today is not a European but, as scholars often put it, a young woman in Nigeria, Brazil or the Philippines.

Sources: Pew Research Center (2025); Fides/Vatican statistics (2026); Center for the Study of Global Christianity.

That shift is changing the faith itself. Southern Christianity tends to be more conservative on sexual ethics, more open to miracles and spiritual warfare, more Pentecostal in style, and more likely to be lived as a minority among Muslims or followers of other religions. It is also why the global Anglican Communion has been strained almost to breaking point over same-sex marriage, with conservative provinces, many of them African, organised in the Gafcon movement, which calls itself a fellowship of "authentic Anglicans".

Vatican II

The Catholic Church's biggest modern event was the Second Vatican Council, opened by Pope John XXIII on 11 October 1962 and closed under Paul VI on 8 December 1965. Bishops from every continent produced sixteen documents. Among the most important:

• Sacrosanctum Concilium (1963) allowed the "mother tongue" in the liturgy, so that within a few years Catholics worldwide heard Mass in their own languages rather than Latin.
• Lumen Gentium (1964) described the church as the "people of God", stressing the role of lay people and the shared authority of bishops with the pope.
• Nostra Aetate (28 October 1965) said the church "rejects nothing that is true and holy" in other religions and rejected the charge that the Jewish people as a whole were guilty of Jesus's death, deploring antisemitism. It transformed Catholic-Jewish relations.
• Dignitatis Humanae (7 December 1965) affirmed religious freedom as a human right.
• Gaudium et Spes (7 December 1965) turned the church towards "the joys and hopes" of the modern world.

The council's meaning is still fought over. Progressive Catholics see it as a beginning whose promise (on the role of women, or of local churches) was never fully kept. Traditionalists think it went too far, especially in the liturgy; Archbishop Marcel Lefebvre's Society of St Pius X broke with Rome over it, and in 2021 Pope Francis restricted the old Latin Mass with Traditionis Custodes. Most Catholics live somewhere in between.

Part 13 — What Christians actually do: sacraments, prayer and the year

An ordinary day and week

Christian practice varies enormously, but some things are close to universal. Many Christians pray daily, often using the prayer Jesus taught, the Lord's Prayer ("Our Father which art in heaven, Hallowed be thy name", Matthew 6:9). Many read the Bible, alone or in groups. Catholics may pray the rosary; Orthodox Christians may repeat the Jesus Prayer ("Lord Jesus Christ, Son of God, have mercy on me") and pray before icons at a home corner; monks and nuns and many lay people pray the "hours" at fixed times of day. Evangelicals often speak of a daily "quiet time" with scripture.

Sunday, the day of the resurrection, is the day of worship. The heart of Catholic, Orthodox, Anglican and Lutheran worship is the Eucharist (also called Mass, Divine Liturgy, Holy Communion or the Lord's Supper): readings from scripture, a sermon, prayers, and the sharing of bread and wine. Many Protestant services centre on preaching and song, with communion monthly or quarterly. In the United States, Pew's 2026 surveys found 34 percent of adults saying they had attended religious services in person in the past month, and 45 percent in person or online.

The sacraments

A sacrament, in the classic definition, is a visible sign of an invisible grace. Christians disagree on how many there are and what they do.

The other Catholic and Orthodox sacraments are confirmation (chrismation), confession (reconciliation), anointing of the sick, marriage and ordination.

The year

Most churches follow a liturgical year that retells the life of Christ:

Western and Orthodox churches usually celebrate Easter on different dates, because they calculate it with different calendars, and church leaders on both sides have long talked about agreeing a common date. In November 2025 Pope Leo XIV made a pilgrimage to İznik, the ancient Nicaea, to mark the council's 1700th anniversary.

Part 14 — Christianity in 2026: abuse, the papacy and the numbers

The abuse crises

The gravest crisis of modern Christianity has been the sexual abuse of children and vulnerable adults by clergy, and its cover-up by church leaders. It has been documented most fully in the Catholic Church, the largest and most centralised church, but it is not only a Catholic story.

The pattern repeated across countries: abusers moved between parishes instead of being reported to police; bishops protected the institution's reputation; victims were disbelieved or silenced with payments. Researchers and church commissions have pointed to clericalism (treating clergy as above question), secrecy, poor training and a culture of deference, rather than to celibacy alone, since abuse has also been found in churches with married clergy. Survivors' groups argue that reforms have been slow and uneven, and that bishops are still too rarely held to account. The Vatican and many national churches point to new safeguarding rules, independent reporting and a Pontifical Commission for the Protection of Minors. Both can be true at once: much has changed since 2002, and much has not.

The papacy as of 2026

Pope Francis, the first pope from the Americas, died on Easter Monday, 21 April 2025, aged 88. On 8 May 2025 the cardinals elected Robert Francis Prevost, who took the name Leo XIV. Born in Chicago in 1955, he is the first pope from the United States and the first from the Augustinian order. He studied mathematics at Villanova before becoming a friar and canon lawyer, spent most of his ministry in Peru (he became a Peruvian citizen in 2015 and was bishop of Chiclayo), led the worldwide Augustinians for twelve years, and from 2023 ran the Vatican office that advises the pope on choosing bishops.

His first major document, the apostolic exhortation Dilexi Te (4 October 2025), on the church's love for the poor, completed a text Francis had been preparing. His first encyclical, Magnifica Humanitas (15 May 2026), is about artificial intelligence and human dignity, published on the 135th anniversary of Leo XIII's Rerum Novarum, the founding text of Catholic social teaching that his chosen name recalls. In 2026 he has travelled to Algeria, Cameroon, Angola and Equatorial Guinea (April), Spain (June), and France and UNESCO (September), and in November he is visiting Uruguay, Argentina and Peru. How he will handle the questions Francis left open, such as the role of women, the blessing of same-sex couples, the old Latin Mass and the church's finances, is what Catholics are watching.

In the Church of England, mother church of the Anglican Communion, Sarah Mullally became the first woman to serve as Archbishop of Canterbury after Welby's resignation.

How many Christians?

Figures differ by method. The Gordon-Conwell center, which also counts church membership records, gives higher totals than Pew, which relies mainly on censuses and surveys of self-identification. Either way, the title of this piece rounds down.

Christianity is still the world's largest religion, but its share is falling. Pew found that for every person who joined Christianity in the 117 countries it studied, about 3.1 people raised Christian had left, mostly to no religion. Christians are now less than half the population of the United Kingdom (49%), Australia (47%) and France (46%). Growth comes from births and conversions in Africa; decline from people leaving in Europe, the Americas and Oceania.

Open questions

• Who speaks for Christianity? A Nigerian Anglican bishop, a Brazilian Pentecostal, a German Lutheran and a Russian Orthodox priest may disagree about nearly everything except the creed.
• Sex and gender. Same-sex marriage, women's ordination and the place of LGBT Christians divide churches internally more than any doctrinal question.
• Power and politics. From Russian Orthodoxy's support for the war in Ukraine to Christian nationalism in the United States and Christian democracy in Europe, Christians disagree about how close faith should stand to the state (see Religion in the Modern Age).
• Can it recover trust? After the abuse crises, whether churches can be trusted with children, money and power is, for many people, the first question, not the last.
• Unity. The ecumenical movement, embodied in the World Council of Churches, a fellowship of 356 churches representing over 580 million Christians (the Catholic Church is not a member but works with it), has made real progress since 1948. Full communion between Rome, Constantinople and the Protestant churches is not in sight.

The takeaway

Christianity began with a Jewish teacher from Galilee whom Rome crucified around the year 30, and with followers who proclaimed that he had risen and was the Son of God. Historians can confirm far less than believers affirm, but they agree he lived, was baptised by John and was crucified under Pilate. Paul opened the movement to non-Jews; Constantine brought it to power; councils at Nicaea and Chalcedon defined its creeds; monks preserved learning; East and West divided; the Reformation broke the West into many churches; colonial empires spread it, with great harm, while local converts made it their own. It inspired abolition and justified slavery, built hospitals and hid abusers. Today it is about 2.3 billion people, more African and Latin American than European, increasingly Pentecostal in style, and still arguing, as it always has, about what its founder meant.

Try this: read one Gospel straight through in a single sitting. Mark is the shortest, about the length of a long magazine article, and most scholars think it is the earliest. Read it once as a believer might, asking what it claims about who Jesus is, and once as a historian might, noticing what it assumes its readers already know. Then notice which reading you found easier, and why.

Sources & Further Reading

Sources
- Pew Research Center, How the Global Religious Landscape Changed From 2010 to 2020 (9 June 2025) and its chapter "Christian population change"; Decline of Christianity in the U.S. Has Slowed, May Have Leveled Off (Religious Landscape Study, 26 February 2025); Religion Remains Stable in the U.S., With Mixed Signals for Young Adults (28 October 2026); Orthodox Christianity in the 21st Century (8 November 2017); Religion in Latin America (13 November 2014); Spirit and Power (2006).
- Fides News Agency, Catholic Church Statistics 2026 (October 2026), from the Vatican's Statistical Yearbook of the Church (data to 30 June / 31 December 2024).
- Center for the Study of Global Christianity, Gordon-Conwell Theological Seminary: "Quick Facts About Global Christianity" and "Global Pentecostalism" pages.
- Tacitus, Annals 15.44 (Church and Brodribb translation, MIT Internet Classics Archive); Pliny the Younger, Letters 10.96 (Internet History Sourcebooks, Fordham University); Lactantius on the edicts of 311 and 313 and the Theodosian Code XVI.1.2 (Fordham sourcebooks); Council of Chalcedon acts (NPNF, Fordham); Athanasius, Festal Letter 39 (NPNF via New Advent); Urban II at Clermont (Fordham).
- L. Michael White and Paula Fredriksen, interviews for From Jesus to Christ (PBS Frontline, 1998), on Gospel dating; Dale B. Martin, Introduction to the New Testament, lecture 1 (Yale Open Courses).
- The Catholic Encyclopedia (1907–1913, via New Advent): articles on the councils of Nicaea, Constantinople and Ephesus, the Muratorian Canon, Marcionites, St Anthony, St Benedict, Constantine, Theodosius, the Eastern Schism, the Crusades, the Inquisition, Luther, Calvin, Trent, the Society of Jesus, St Vladimir and Matteo Ricci (used for dates; its century-old judgements are not followed).
- Vatican: joint Catholic-Orthodox declaration of 7 December 1965; Vatican II documents (vatican.va archive, with dates); Pastor aeternus (1870); Pascendi (1907); John Paul II, homily for the Day of Pardon (12 March 2000) and letter on the Inquisition symposium (15 June 2004); Vos estis lux mundi (2019); Joint Statement on the "Doctrine of Discovery" (30 March 2023); Leo XIV's official biography, Dilexi Te, Magnifica Humanitas, and travel pages; Vatican News on the death of Pope Francis (21 April 2025).
- M. Drelichman, J. Vidal-Robert and H.-J. Voth, "The long-run effects of religious persecution: Evidence from the Spanish Inquisition", PNAS 118 (2021).
- Henry Kamen, The Spanish Inquisition: A Historical Revision (Yale University Press, 4th ed. 2014), publisher's description.
- Church of England, "History of the Church of England"; press release on the Makin review (November 2024); archbishopofcanterbury.org (October 2026).
- National Centre for Truth and Reconciliation (Canada), residential school history and TRC pages.
- Dictionary of African Christian Biography: entries on William Wadé Harris and Simon Kimbangu.
- Southern Baptist Convention, "Resolution on Racial Reconciliation on the 150th Anniversary of the Southern Baptist Convention" (1995); Georgetown University, Slavery, Memory and Reconciliation.
- Frederick Douglass, Narrative of the Life of Frederick Douglass (1845), appendix (Project Gutenberg).
- John Jay College of Criminal Justice, The Nature and Scope of Sexual Abuse of Minors by Catholic Priests and Deacons in the United States, 1950–2002 (2004); Commission to Inquire into Child Abuse (Ireland); CIASE, Summary of the Final Report (5 October 2021).
- World Council of Churches, "About the WCC" and "Pentecostal churches" pages.
- King James Version (1611) via Project Gutenberg, for all Bible quotations.
- Wikipedia articles on the historical Jesus, Pontius Pilate, the Pauline epistles, the Council of Jerusalem, the Diocletianic persecution, the Spanish Inquisition and others were consulted as leads only.

Go deeper
- 📘 A History of Christianity: The First Three Thousand Years — Diarmaid MacCulloch (the best single-volume history: fair to every branch, strong on the Orthodox and the global story, and very readable)
- 📘 The Historical Figure of Jesus — E. P. Sanders (a careful, non-polemical account of what historians can know, from one of the scholars who put Jesus back into Judaism)
- 📘 The Orthodox Church — Timothy (Kallistos) Ware (the classic introduction by an English convert who became an Orthodox bishop; how Orthodoxy sees itself)
- 📘 The Next Christendom — Philip Jenkins (why the typical Christian is now African or Latin American, and what that means)
- 📘 God's War: A New History of the Crusades — Christopher Tyerman (the crusades in full, without myth in either direction)
- 📘 Translating the Message — Lamin Sanneh (a Gambian-born historian's argument that missions empowered the cultures they entered)
- ▶️ From Jesus to Christ: The First Christians — PBS Frontline (four hours of leading scholars on the first century; the companion website is still online)
- 🌐 Companion pieces in this library: How the Sacred Texts Were Written, Mysticism 101, the Mystics pieces on Eckhart, Teresa, John of the Cross and Julian, and the Religions long reads on Judaism, Islam and Religion in the Modern Age