Why you should distrust all religions.

[The Grand Nudger]

If you're content with magic book as a historical source then you're content with magic book as a historical source.  I have reservations.  Cheifly, that the christian textual apparatus is known to have produced massive fabrications out of absolutely nothing, lol.  

They're taking magic books word for it.  A theological and -historic- explanation of the character, and changing character of "Paul"...however, does not depend upon the existence of a historical paul.  

Perhaps you could present what you feel to be the strongest point in that argument?

There are books (or copies of manuscripts, rather) which we know exist.

Yep.  Magic book.

Some of them are letters written to the various churches. Among these letters are letters attributed to a single person called Paul with consistency in style of writing/language (as determined by scholars). So, according to scholars, it's reasonable to assume (in the absence of controversial evidence) there was a single guy who authored these letters.

Sure.  The "letters" were authored by a single guy.

Now, there were other letters also attributed to Paul, but using textual analysis, scholars were able to detect inconsistencies and/or forgeries, considering several other factors (such as agenda of the author, the theologies described, the aim of the message), so they reason that this could not have been the same Paul who authored the other letters. For specific details on this and that, refer to the scholars of course.

You can read Richard Carrier at your own pace, when you're in the mood for it.

Well, I read his conclusion and found nothing in it that provides criticism of the position that early or authentic paul is legendary.  We're only discussing items that exist on a continuum from "obviously legendary" -to- "marginally less legendary".  Carrier himself posits that..limited to early paul, there is still no vouching for the accuracy of the details of the text.

per your link-

The logically correct conclusion is that Paul probably existed and wrote the six authentic letters in the 50s A.D. (albeit we are now seeing only fractions of the actual letters he wrote, and somewhat meddled with). And that conclusion follows even when the same logic and methodology leads to the conclusion that, unlike Paul, Jesus probably did not exist. Except, originally, in the fevered imaginations of the revelators of a schizotypal cult (OHJ, Chapter 4, Elements 15 and 16, pp. 124-41).

The crux of the entire essay is why his standard for mythicism doesn't apply to paul.  I agree.  I don't think that the character of paul was ever taken to be a myth.  I think it's been a legend from the getgo. Carrier thinks there's a probable paul, somehow related to some of early paul, though not every detail, or any detail in specific - and whomever this cypher is supposed to be would be the "historic paul".

Whereas Carrier thinks that paul began as someone who was or was at least taken to be a real person in history (to whatever extent he'd entertain the notion), his standard of mythicism for christ proposes that christ -began- as myth.