I once had a New Testament professor who thought that the Gospels and Acts were largely unhistorical. His reason was that they seem to mirror stories from the Hebrew Bible.
For example, in Matthew 26-27, Judas delivers Christ to the high priest for thirty pieces of silver. In Genesis 27, Judah (or, in the Septuagint, Judas) sells Joseph for twenty shekels of silver.
In Matthew 27:5, Judas hangs himself because he feels bad about betraying Jesus. In the Septuagint of II Samuel 17:23, Ahithophel hangs himself, and he was the betrayer of David.
My professor also saw a parallel between Saul the Benjamite in the Book of Acts, and Saul the Benjamite in I Samuel. As far as he's concerned, Paul wasn't called "Saul" in real life, but the author of Acts is calling him that because he has the Old Testament figure in mind. And there is a similarity, for King Saul hunted down David, and Saul of Tarsus hunted down the early Christians.
Here's an example my professor didn't use in my class, but others have cited it: In Acts 10, God shows Peter a sheet with unclean animals, which he commands him to kill and to eat. Peter responds that he never ate anything common or unclean. Similarly, in Ezekiel 4, God instructs Ezekiel to eat defiled bread that's been cooked with cow dung (I always thought Ezekiel's Bread tasted funny!). And Ezekiel reacts much like Peter: "Ah Lord GOD! I have never defiled myself; from my youth up until now I have never eaten what died of itself or was torn by animals, nor has carrion flesh come into my mouth" (4:14 NRSV).
For my professor, the New Testament authors must have made up these stories, for they so obviously resemble tales from the Old Testament. As far as my professor was concerned, the Gospel authors got their ideas from the Hebrew Bible, not from real life.
But I noticed something when I was reading the Book of Acts. In Acts 9:23-25, the Jews plot to kill Paul, so his disciples help him escape by lowering him down a wall. In its commentary on this passage, The HarperCollins Study Bible cited Joshua 2:15 and II Corinthians 11:32-33.
Both passages are significant. In Joshua 2:15, Rahab rescues the Israelite spies from the wrath of the king of Jericho, and she does so by lowering them down a wall. That allows them to escape from the city. This sounds a lot like what the believers do for Paul in Acts 9:23-25.
In II Corinthians 11:32-33, we read: "In Damascus, the governor under King Aretas guarded the city of Damascus in order to seize me, but I was let down in a basket through a window in the wall, and escaped from his hands."
As far as I know, the vast majority of New Testament scholars treat Paul's letters as historically accurate. After all, they are primary sources from an apostle who talks about his own life. So if Paul says that he was "let down in a basket through a window in the wall" to escape the wrath of a ruler, then it most likely happened.
But it sounds so much like the story in Joshua. Does that matter? It's in a primary source, so it probably happened!
Can life ever mirror art? Is it possible that betrayers can hang themselves more than once in human history? Or that a man named Judas can sell someone? Or that God can appear to two separate people and tell them to eat non-kosher food? Why can't these things happen more than once? Why is something unhistorical just because it resembles an Old Testament story.