Both good and educated answers, but I think you miss my point: I'm into falsification. A believer says something like "Paul wrote ..... so ...... must be a fact". That is a falsifiable scenario, and to falsify it, all you need is to provide a different scenario that fits the observations.
I don't think "falsifiability" ever meant "argument from ignorance", though.
I mean, "There is a widow in Nigeria who needs my bank account to transfer 80 million dollars" is equally falsifiable, and there is even an observation there: the emails from said widow. But sometimes it's ok to just conclude that the source is too unreliable to support the positive claim that such a widow exists, rather than have to falsify it.
But let's see... other equally good scenarios for Paul include:
1. Paul is a con-man, just like Joseph Smith, Ron Hubbard, and pretty much the majority of people who ever started a religion.
Even the motive is basically there, since suddenly we see Paul traveling all over the place and being treated as a superstar. Plus, he's obviously having no problems staying away from whatever business he had in Jerusalem, and even travels some sort of a personal assistant he dictates letters to. He seems to be making a better living out of it, than, say, if he kept kneading leather in crap like a leatherworker (if we believe Acts, which is a big if.) Probably not a luxurious living, but even just being able to travel and be fed on someone else's expense is still more than most people back then would get.
Red flags there would include, basically, that not many normal people would keep avoiding straight questions and do a dozen pages of handwaving instead of answering (like the donation money issue he had with the Corinthians), nor would feel a need to preemptively tell you you can't check their claims. You don't hear people saying stuff like "I studied in Paris, but nobody there would recognize me, of course. And then I got encouraged to write a book by some important guys you wouldn't know anyway." Yet Paul does exactly that. He supposedly persecuted Christians... but nobody would know his face. He got some people in Jerusalem to agree with him... but he doesn't say who, or what authority they had to greenlight Paul's apostleship, or anything. He just says they looked important.
2. Paul is genuinely schizophrenic.
For a start he's obsessed with Jesus, but never shows any interest in sharing or even finding out anything about Jesus. He even insists that he didn't get his message from any man, and according to his own chronology he was preaching for years before even meeting Peter (or any other apostle.) It's like meeting a guy who's obsessed with Eminem and rants for hours about Eminem, but isn't even interested in any information about the singer, the music, or the lyrics, nor is sharing any. That's a schizophrenic kind of behaviour.
Paul's logic is also bizarre to the extreme. Literally stuff like the law is good, but we keep it by being Christians instead of doing what it says, but we're not rejecting the law, and it's good, but it's a curse from which Christ saves us, but it's still good for keeping crooks straight, but we don't have to keep it, but actually we keep it by being Christians. No, really, that screwed up in the head.
He also reads whole pages of meaning specifically about him and his congregation, and meant for him and his congregation, in half-sentences said by minor characters in the OT, just like Charles Manson would find cryptic prophecies in Beatles lyrics.
In fact he even spells out something which, if taken at face value, pretty much is what Kapyong and Doherty and the gang are trying to tell us: Jesus is revealed by those cryptic passages in the OT. That's where Paul finds Jesus. In his vision and reading some paragraphs in a schizophrenic way, not as a real person.
And if we take some passages from him at face value, he talked to Jesus after that first vision again and even got at least one detailed answer. Also in one place he actually claims to have been stoned, and in another place that he himself was crucified and is now dead and is some kind of zombie animated by Jesus's will. If you take that literally, Paul is a textbook case of Cotard delusion. Which incidentally also often includes delusion of immortality resulting from that undead condition.
Etc. That's not even the only good scenarios, but just for illustration sake, they'll have to do.
