Book of Luke / (some of) Acts - yes, probably the same person, traditionally thought to be a physician friend of Paul / Saul, but again, no authorship provided or sources cited, so we don't really know.
So much in the NT was written to satisfy various OT prophecies that it can all feel a bit contrived - but again, AIUI, the writings in 'Mark' (the first of the four) strongly suggest post-70CE, but perhaps much later.
I suppose anything is 'not implausible' if you're inclined in a certain direction.
We know the "disciple who Jesus loved" is John from John, and in the last chapter, the book is explicitly attributed to him as "the one who testifies of these things and wrote them down", in the typical third-person way of this sort of literature.
If you care what other people close in time thought, we know that for example, Clement of Alexandria believed this based on tradition as well. Of course, we can suspend judgement: we have no way of knowing. But in the absence of clear contradictory evidence, I don't think it's unreasonable to rest on the side of "whatever the text and the closest contemporaries we have thought."
> sources cited,
What do you mean by this?
> AIUI, the writings in 'Mark' (the first of the four) strongly suggest post-70CE, but perhaps much later.
This argument rests entirely on what I alluded to earlier. As I mentioned, from a purely secular perspective, it isn't surprising that someone could guess that Jerusalem would someday be destroyed. It happened many times before! On top of this, the political situation was delicate, and very similar to the last time Jerusalem had been destroyed. But setting all that aside:
https://www.kingjamesbibleonline.org/Mark-Chapter-13/
Read this and tell me if this is a clear, definite allusion to the Roman destruction of Jerusalem in 70, or a vague handwavy prophecy about "Bad Things Will Happen and the Temple will be destroyed".
Eventually. If anything, it's very confused, since if you assume the passage is talking about the 70AD war, it's clearly also being mixed up with the actual end of the world. It seems just as likely as vague statements that could easily be fit into later actual events. The Greek world was certainly absolutely rife with these things. No doubt it helped the Christians to point to a vague "prophecy" and say "see, we told you!" and helped its spread, which in turn made it more likely for the text to survive to present day.
Historiography is not really an exact science, and it's very fad-driven. The academic consensus goes back and forth over time, depending on what's in fashion and who has died. That’s why relatively unsurprising archeological finds often result in major historiographical shifts.
Clement - a religious (read indoctrinated and partisan) person born 120 years after Jesus was meant to have died, is neither 'close in time' nor relevant.
We have plenty of historical works from the actual time about other things where authors identified themselves, cited their sources, did not obfuscate their meanings, etc - so it's not like that skill was unknown. As you say, 'literature' is an apt word for these stories.
As to before / after 70 CE, I guess we'll have to move on from there also, as I don't have a horse in that race.
I'm not saying the book is written by John. In fact, I'm saying it's unknowable. What I'm doing is laying out the arguments for and against:
For: The book internally claims to be written by John, and very early authors claim to have been told that traditionally.
Against: John was the latest of the Gospels, and since John was written last based on it's style and on the traditional commentary, and since Mark was written after 70AD because we think it alludes to the Siege of Jerusalem, and because we're told in Acts that John wasn't particularly scholarly, John could not have been written by John because he was most likely dead by the time it was written and he wasn't sufficiently scholarly.
You can see that neither one of these are logical proofs. That's the nature of this type of historiography. There's nothing even close to proof. Consensus, such as it is, is just based on the opinions of the current people in the field, who have to publish or perish (thus we're subjected to papers like "Xenophon couldn't have been at the battle of Cunaxa because his description of Cyrus's head wound differs very slightly from the doctor's"). "Everyone was right" is not publishable, so the debate goes on forever and the fashion changes. Of course some arguments can be stronger than others! For example, a common type of argument goes like this:
Passage X is an interpolation. It exists in tons of the later texts we have, but none of the earlier ones.
This is a probabilistic argument: we can never be certain. It could be the case that Passage X was included in the original manuscript, but that an early, popular copyist elided the passage and his copy spawned many others. But this is how it all goes. We're not making certain arguments. It's really more of a persuasive sport. Assuming you have read a given text carefully and are reasonably well-informed on contemporary history, there is no particular reason you have to accept the current consensus. It isn't based on super obscure expert knowledge. If as a layman, you (reasonably!) want to just accept the current academic consensus, that's fine! It's just important to understand what it is actually based on, and that it doesn't constitute anything close to knowledge or certainty.
> As to before / after 70 CE, I guess we'll have to move on from there also, as I don't have a horse in that race.
That's actually a very important point for the dating of the gospels, which is in turn a major point in the authorship debate.
> Clement - a religious (read indoctrinated and partisan) person born 120 years after Jesus was meant to have died, is neither 'close in time' nor relevant.
Unless you know anyone closer in time and nonpartisan, people like him and Irenaeus are all we've got. And that's typical. Disinterested parties don't usually write popular surviving historical works. This is reminiscent of a popular line of historiography: X isn't true because the author was motivated to believe it. Of course this is always possible but it's a very tiresome argument in the absence of some other evidence.