@WadCheber I'm definitely open to that conclusion and want to hear about serious scholarship proposing it. But also other theories

The weakness of arguing a doublet (in general) implies two sources, IMO, is that doesn't really help explain why the author did it. I have often accidentally made the same point multiple times in my own writing, especially when editing and re-editing, but never because I started with two sources. And when read it back later with fresh eyes, I catch the mistake.

So unless we are assuming John (or whatever other text) went through minimal/no editing (an unlikely assumption), I don't see why saying he used two sources would make it any less likely that he would fix the doublet (assuming it is not intentional) on re-editing than if it had arisen through a confusion of his own thoughts as he wrote the first time.

@WadCheber Then you had better read Matitiahu Tsevat's exploration of "common sense and hypothesis" in biblical study. You'll be glad you did.

@Dan Minor correction on behalf of @ScottS. ;-)

^^ I have half a mind to put this on hold as off-topic unless/until he makes the change recommended by @ThaddeusB.

(Or scopes it so that we can migrate it to C.SE. But he knows well how C.SE works and hasn’t done that, so I can’t see that doing it for him is going to help.)

@Susan I had a whole mind. Does OP see the vote count? If so, my prompt into action.

@Davïd A whole mind, but only a fifth of a closure, it should be noted. :P

(Not sure about the vote count, but I think it’s visible to all.)

@Susan To be precise. (Just in case there are any Tintin fans lurking.)

(Four lines up should read: "may prompt into action", of course.)

@Davïd Had considered correcting it, but the following is also a noun, and you left me either without a subject or without a verb, so couldn’t quite decide. No subjects or verbs necessary in chat, of course.

@Susan What is the protocol here? Is there any reason not to just make the change so that the question is on topic? My understanding is that questions almost belong as much to the community as they do to the person asking.

@Soldarnal Well you would probably know better than me. ;-) The reason I didn't edit it was because it seemed like a very easy edit that the OP was quite capable of doing if that was consistent with his intentions. I edit things for people if I think they need help or if I am personally really interested in a question and want to see it fly - this didn't fit into either category for me. It's totally reasonable if you would like to do so, though.