Questions, answered with the evidence

Almost all historians of the ancient world, whether Christian, Jewish or secular, think that Jesus of Nazareth existed. The strongest evidence is Paul, who within about five years of the crucifixion stayed with Jesus' leading disciple Peter and met his brother James, and who wrote letters in the 50s CE that survive. Four Gospels followed within about forty to eighty years, and two non-Christian writers mention him: the Jewish historian Josephus around 93 CE and the Roman historian Tacitus around 116 CE. The theory that Jesus was a myth, argued today by Richard Carrier and a few others, has almost no support among specialists. Historians can establish that he lived, was baptised by John and was crucified under Pontius Pilate; what he was is a question of faith.

Not in the sense the question usually means. Paul's own letters, the oldest Christian writings, show that the core of Christian belief and practice was in place before him: the creed that Christ died, was raised and appeared to Peter and others, the Lord's Supper, baptism, and prayer to Jesus as Lord in Aramaic. Paul says he received these from those who were believers before him. What Paul did was fight for one decisive position: that non-Jews could belong to Israel's Messiah without being circumcised or keeping the Jewish law. That choice, made in the 40s and 50s CE, made a separate religion possible, though Paul himself never used the word 'Christian' and saw himself as a Jew. Since the nineteenth century some writers have called him the real founder of Christianity, and Wrede in 1904 its 'second founder'; most scholars now see him as a decisive interpreter of a movement that already existed.

Nobody knows for certain. None of the four Gospels names its author in the text. The titles 'according to Matthew', 'Mark', 'Luke' and 'John' are attested from the second century: Papias, around 110–130, links Gospel writing to Mark and Matthew, and Irenaeus, around 180, names all four. Tradition holds that two were written by apostles (Matthew and John) and two by companions of apostles (Mark, for Peter, and Luke, for Paul). Most critical scholars think the authors were Greek-speaking Christians of the second and third generation who used written sources and oral tradition, writing between about 70 and 110 CE, and that the names were attached as the books gained authority. A significant minority, notably Richard Bauckham, argue that the Gospels rest closely on named eyewitnesses.

'Gnostic gospels' is a popular name, given currency by Elaine Pagels' book of 1979, for early Christian writings outside the New Testament, most of them found in a jar near Nag Hammadi in Egypt in December 1945. They include the Gospel of Thomas, a collection of 114 sayings of Jesus; the Gospel of Philip; the Gospel of Truth; the Secret Book of John; and, from other finds, the Gospel of Mary and the Gospel of Judas. Most date from the second century or later, after the four canonical Gospels. They are a mixed collection: some teach that the world was made by a lesser, ignorant god and that salvation comes through knowledge (gnōsis) of the true God, while others, like Thomas, are not clearly Gnostic at all. They were left out of the New Testament because the churches that shaped it judged them late, not apostolic, or contrary to their teaching; no single council made the decision.

No single person or council. The books of the New Testament were chosen by use, over about three centuries, as churches read some texts in worship and stopped reading others. Marcion made the first fixed list around 144; by about 180 Irenaeus insisted on exactly four Gospels; the first list of exactly today's 27 books is Athanasius' Easter letter of 367, and synods at Hippo (393) and Carthage (397) adopted it for North Africa. Some churches went on reading a shorter or longer New Testament for centuries. No surviving record of the Council of Nicaea in 325 shows it discussing the canon. For the Old Testament, Catholics and Protestants still differ: the Council of Trent made the Catholic list, including books Protestants call the Apocrypha, a dogma in 1546.

No. Constantine, emperor from 306, ruler of the whole West from 312 and sole ruler from 324, ended the persecution of Christians, gave them back their property, favoured their bishops and built great churches, but he left the traditional cults legal and remained pontifex maximus, head of the Roman priesthoods, all his life. The step usually counted as making Christianity the state religion came under Theodosius I. His edict Cunctos populos of February 380, addressed to the people of Constantinople and later read as binding the whole empire, required the faith of the bishops of Rome and Alexandria and called only its followers 'Catholic Christians'. Laws of 391–392 then banned pagan sacrifice and temple worship.

In the summer of 325 the emperor Constantine gathered roughly 250 to 300 bishops, almost all from the Greek-speaking East, at Nicaea in north-west Asia Minor to settle a dispute started by Arius, a priest of Alexandria who taught that the Son of God had a beginning and was created. The council issued a creed declaring the Son 'of one substance' (homoousios) with the Father and condemning Arius' views; agreed that all churches should keep Easter on the same Sunday; and passed twenty canons on church discipline. Only two bishops refused to sign. Nicaea did not choose the books of the Bible, and it did not vote Jesus divine for the first time: Christians had worshipped him for nearly three centuries. Nor did it end the argument, which ran for another sixty years.

In stages, over about three centuries. The New Testament speaks of Father, Son and Holy Spirit together, most clearly in the baptismal formula of Matthew 28:19, but it has no word for their unity and no account of how they relate. The Greek word trias, 'triad', is first used of God by Theophilus of Antioch around 180, and the Latin trinitas, with three persons (personae) of one substance, by Tertullian around 213. The Council of Nicaea in 325 declared the Son 'of one substance' with the Father; theologians from Cappadocia then distinguished one divine being from three 'persons', and the Council of Constantinople in 381 declared the Holy Spirit fully divine. That is the doctrine most churches hold today. The clearest Trinitarian verse in some Bibles, 1 John 5:7–8, is a later Latin addition.

Nobody knows for certain. The Gospels give no date or season for Jesus' birth. The earliest secure evidence for a feast of his birth on 25 December is a Roman list of feast days dated to 336 and preserved in an almanac of 354; an earlier mention by Hippolytus, around 204, is widely suspected of being a later addition. There are two main explanations. One holds that the church chose the day of a Roman festival of the Unconquered Sun in order to replace it. The other, the 'calculation theory', holds that Christians dated Jesus' death, and therefore his conception, to 25 March, and counted nine months forward. Neither is proved, and both may have played a part. Many Eastern churches kept 6 January instead, and the Armenian Apostolic Church still does.

The Church of the East is the church of the Christians of the Persian Empire and their successors. It was organised at a synod in Seleucia-Ctesiphon in 410, became in effect independent of the church of the Roman Empire in 424, worshipped in Syriac and followed the theology of Theodore of Mopsuestia. Its opponents called it 'Nestorian', a label scholars now regard as misleading. Between the seventh and fourteenth centuries it was geographically one of the most widespread churches in the world, with bishops from Iraq to Central Asia, India and China, where a monk named Alopen arrived in 635. War, plague, the conversion of the Mongol khans to Islam and the campaigns of Timur reduced it by 1400 to the mountains of northern Iraq and its borders and the coast of Kerala. Its heirs today are the Assyrian Church of the East, the Ancient Church of the East, and, in communion with Rome, the Chaldean Catholic Church.

By the sixth century at the latest, and possibly much earlier. The Christians of Kerala, the Saint Thomas Christians, hold that the apostle Thomas landed on the Malabar coast in 52 CE and was martyred near modern Chennai in 72. That tradition cannot be proved or disproved: the third-century Acts of Thomas sends Thomas to a real Indo-Parthian king in the north-west, not to Kerala. The first firm evidence is the report of the merchant Cosmas Indicopleustes around 550 of a church on the pepper coast and a bishop appointed from Persia, and the Tharisapalli copper plates of about 849 show a well-established Christian community at Quilon. These Christians belonged to the Church of the East and worshipped in Syriac. Catholic missions arrived with the Portuguese after 1498, Protestant missions from 1706, and today Christians are about 2.3 per cent of India's population.

No. Nothing in the New Testament says that Mary Magdalene was a prostitute or even a sinner. The Gospels say that Jesus had cast seven demons out of her, that she travelled with him and helped support his followers from her own resources, that she watched the crucifixion, and that she was the first to find the tomb empty; in John, she is the first to see the risen Jesus and is sent to tell the disciples. In a sermon of 591, Pope Gregory the Great identified her with an unnamed 'sinful woman' in Luke and with Mary of Bethany, and read her sins as sexual. Western art and legend then made her a former prostitute. The Eastern churches never accepted the merger, and in 1969 the Roman Catholic calendar separated the three women again; in 2016 her memorial was raised to a feast, with the old title 'apostle of the apostles'.

From prayer for the dead, which is older than Christianity, and from a few biblical texts that later writers read as describing a cleansing after death. Augustine and Gregory the Great wrote of a purifying fire for lesser sins. The noun purgatorium, treating purgatory as a place, first appears in the Paris schools around 1170–1180, as the historian Jacques Le Goff showed; critics argue the idea itself had grown continuously for centuries. The Latin church set out the teaching at the Second Council of Lyon in 1274, at Florence in 1439 and at Trent in 1563, without defining it as a place or a fire. It became the basis of masses for the dead and of indulgences, which the Reformers attacked; the Orthodox churches pray for the dead but never adopted the doctrine.

There was no single moment. The Latin West and the Greek East drifted apart over centuries, divided by language, by the pope's claim to authority over the whole church, by the filioque (the Western addition 'and the Son' to the creed), and by customs such as unleavened bread and clerical celibacy. In 1054 a papal legate excommunicated the patriarch of Constantinople and a Greek synod excommunicated the legate, but these were personal sentences, and contacts continued. What turned estrangement into lasting schism was the Fourth Crusade's sack of Constantinople in 1204 and the Latin occupation that followed. Attempts at reunion at Lyon in 1274 and Florence in 1439 were rejected in the East. In 1965 the pope and the patriarch lifted the excommunications of 1054, but the two churches remain out of communion.

Perhaps, but not in the way the famous picture shows. What is certain is that on 31 October 1517 Luther sent his ninety-five Latin theses on indulgences to Archbishop Albrecht of Mainz with a covering letter that survives. The story that he posted them on the door of the Castle Church in Wittenberg first appears in print in an account by his colleague Philip Melanchthon published after Luther's death in 1546, and in 1961 the Catholic historian Erwin Iserloh argued that the posting never happened. In 2006 a handwritten note by Luther's secretary Georg Rörer, written in Luther's lifetime, was identified; it says the theses were posted on the doors of Wittenberg's churches on the eve of All Saints. Many historians now think a posting is likely, since church doors served as the university's notice board, but the question remains open. The hammer and the defiant crowd are later embellishments.

The word comes from the Latin rapiemur, 'we shall be caught up', in the Vulgate of 1 Thessalonians 4:17, where Paul, writing around 50 CE, says believers alive at the Lord's coming will be caught up to meet him in the air. For most of Christian history that verse was read as part of a single Second Coming at the end of history. The distinctive modern doctrine, a secret Rapture of the church before a seven-year tribulation, followed later by Christ's visible return, was systematised by the Anglo-Irish Brethren leader John Nelson Darby in the early 1830s. It spread in North America through Bible conferences such as Niagara (1876–1897) and the notes of the Scofield Reference Bible (1909), and reached a mass audience through Hal Lindsey's The Late Great Planet Earth (1970) and the Left Behind novels (1995–2007). Catholic, Orthodox, Lutheran, Reformed, Anglican and Methodist teaching does not include it.

Pentecostalism grew out of the nineteenth-century Holiness movement, which taught a second experience after conversion and often called it baptism in the Holy Spirit. Its usual starting points are 1 January 1901, when Agnes Ozman spoke in tongues at Charles Parham's Bible school in Topeka, Kansas, and the Azusa Street revival in Los Angeles, led from April 1906 by the African American preacher William J. Seymour, which drew Black, white and Latino worshippers together and sent missionaries across the world. Revivals with similar features broke out in the same decade in Wales, at Pandita Ramabai's Mukti mission in India, in Pyongyang and in Valparaíso, Chile, and many historians now describe Pentecostalism as having several origins rather than one. By the early twenty-first century Pentecostals and charismatics numbered in the hundreds of millions, about 27 per cent of all Christians in 2010 (Pew, 2011).