There’s a type of ancient literature called
Why did people write such things? Well like I said, fanfiction. They wanted to teach their ideas, and figured the best way to do it was with a book supposedly written by an Old Testament or New Testament saint. Sometimes they wanted people to really believe it was written by that saint, so they’d take the book seriously. Sometimes they were okay with people knowing better. Problem is, people would believe that saint wrote that book… and might change their beliefs accordingly. After all if an archaeologist dug up a book which Christ Jesus himself appears to have written, and you believed Jesus literally wrote it, you’d follow it, right? If I believed it, I certainly would. (But I’m pretty sure he never did.)
So when the ancient Christians determined which books they consider scripture—which books are now part of our New Testament—some of their favorite books were actually pseudepigraphal books. Like the Gospel of Peter. Yep, there’s a gospel of Simon Peter! Egyptian Christians knew of it, which is why both Origen of Alexandria and Titus Flavius Clemens wrote of it. But Peter didn’t write it, and once the ancient Christians figured this out, they stopped treating it as scripture.
Anyway because such books exist, sometimes we get bible scholars who wonder whether some of the books which are in our New Testament… aren’t actually pseudepigrapha. Maybe some of Paul’s letters aren’t really Paul’s letters, but written by some overzealous Christian who wanted people to think these were Paul’s letters, and get Christians to take their ideas more seriously because they were “Paul’s.”
Of course it’s just as likely we got a bible scholar who wants to make a name for themselves by questioning the authenticity of a book of the New Testament.