Part of my reasoning that the Bible is true is that the New Testament gospels share many embarrassing details about the writers themselves, such as how they were dim-witted doubting cowards, especially during the events leading up to the crucifixion, while the women were faithful and brave. The disciples recorded that Jesus called their own 'lead' disciple Peter "Satan". They recorded that the Messiah they were following was called crazy by his own family, his brothers didn't believe him, he let a prostitute wipe his feet with her hair, etc. etc.
If I were writing a "made up story", I wouldn't in my wildest dreams choose to write it like that. I wouldn't portray myself as a dim-witted doubting sissy.
In the early centuries of Christianity, there were over 200 Christian gospels in circulation, all of them containing wildly varied stories and theologies1. As the Church became organized there was much worry that no-one truly knew what Jesus had said or done, so they ratified just four Gospels: They picked the number four because "there were four winds, four points of the compass, four corners of the temple", mirroring the arguments of Irenaeus in the 2nd century - "just as the gospel of Christ has been spread by the four winds of heaven over the four corners of the earth, so there must be four and only four Gospels"2. The four canonical gospels comprise of synoptic gospels (Matthew, Mark and Luke) plus John. None are eye-witness accounts of Jesus' life and they are all written in Greek, not in the native tongues of anyone who met and followed Jesus. Many of the stories in the Gospels are copied from Greek god-man legends, especially those of Dionysus and Osiris. Although we now know them by the names of Matthew, Mark, Luke and John, they are all originally anonymous3.
Mark is the earliest gospel, composed between 60 and 80CE, by a Roman convert who was unfamiliar with Jewish customs and who had not met Jesus. The oldest versions of Mark all ended at Mark 16:8 with the words "according to Mark", and an unknown author at some point added Mark 16:9-20.
Matthew and Luke both used Mark as their source material (92% and 54% copied, respectively), except they corrected many of his blunders about Jewish life and added additional material from a second source document that historians call "Q"4. Matthew was written after 70CE and before 100CE. The first two chapters of Matthew were not present in the first versions and were added later by an unknown author. Luke was written after 93CE and uses Josephus's Jewish Antiquities. It claims to have been written by a travelling partner of Paul but the text contains too many mistakes with regards to Paul, and was written too late, for that to be true. Matthew and Luke copied such a large portion of their texts that it is clear neither were eye-witnesses, or friends-of-eyewitnesses, of Jesus.
John was written last. Our earliest fragment of it dates from 125CE. It has Jesus speak using completely different language, sentence structure and style to the other gospels. It contradicts the others on almost every point of history. Most people assume that John was writing figuratively writer and not attempting to record history, but was instead set out to write interesting and meaningful stories about Jesus, who was by then, famous. John is considered the least trustworthy of all the gospels.
Who Wrote the Four Gospels of the New Testament? An Introduction to Matthew, Mark, Luke and John.