The first is from a mod, not a question-poster or a regular commenter. Well, actually it's from John Meier. I've not read all three volumes of "A Marginal Jew," but I read the first eons ago and I've read enough otherwise about Meier to be kind of dumbfounded that he thinks there actually were 12 disciples. I'm neutral at best on the idea of Israel-symbolism attesting to vs. detracting from, the idea of authenticity. I can see where Meier would think that this is part of Jesus proclaiming himself as the new Israel.
That said, the mod notes that — duh — it's clear that more than 12 followed Jesus.
So, other than symbolic value by gospelers, why would he believe that Jesus picked out 12?
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Why would Paul "invent" the 500 witnesses to the resurrection in 1 Corinthians 15, per this question? And, why does Dale Allison believe it's real?
Dale, in reality, that's Corinth 2,000 years ago. Like some Corinthian Jesus-fearer is trekking off to Jerusalem, Judea and Galilee with a checklist asking people within the Jesus-fearer communities there "did you witness the resurrection"?
As for another post from a few years ago, the idea that 1 Corinthians 15:3b-5 was an earlier creedal statement but 6-7 may be Pauline? Per the chapter, verse 3a has Paul's "what I have received." While this does not have the added "from the Lord," the language which he uses to introduce the Eucharist, which many scholars believe he invented, it at least leaves open the possibility he's claiming divine revelation.
Beyond that, since Paul was an irregular visitor to Jerusalem and Caesarea after starting his missionizing, and as far as we know, never went to Galilee, how would he know a certain number of these 500 were still alive anyway?
Add this all up and Allison doesn't have much credibility. It should be added that, per a long-ago piece by me, Allison is at the conservative end of critical scholarship.
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Side note: I recently left the similar (and also blocking) subreddit r/AskBibleScholars, after seeing the creator saying he was going to migrate it elsewhere or something. (His reasoning made it look self-serving, and besides, even if he moves, he can't kill the subreddit. They live forever, even if it will be a shell.) I also blocked him.