Did Job originally end at the end of chapter 41? What's existentialism got to do with it?

I doubt it; I hugely doubt it.

That's as, per the Blake painting, to riff on a biblical phrase, I wonder: "Who watches the comforters?"

I digress. Back to the main point.

Someone at one of the biblical subreddits made such a claim about the ending of the book of Job a while back. He based that claim by the comment just before the speeches of Yahweh starting, at the end of Job's last response to his "comforters" in Job 31:40, which ends:

The words of Job are ended.

This meant that chapter 42 had to be an addition. 

I first said, in essence, that no, that could mean, "Job is done speaking for now," not "done, period."

Then, the better answer hit me in the face, namely the start of Job 40:

40 The Lord said to Job:

2  “Will the one who contends with the Almighty correct him? Let him who accuses God answer him!”

3 Then Job answered the Lord:

4  “I am unworthy—how can I reply to you?  I put my hand over my mouth. 5  I spoke once, but I have no answer — twice, but I will say no more.”

6 Then the Lord spoke to Job out of the storm:

7  “Brace yourself like a man;  I will question you, and you shall answer me.

There you go. If you really believe Job 42 is a later addition because of 31:40, then you also have to believe Job 40:3-5 is, and for linguistic smoothness, you must also believe that either 40:1-2 or 40:6 is also an interpolation.

There's also the text-historical issue. We have a copy of Job at Qumran, and it ends pretty much the way today's does, and is dated to circa 100 BCE. Given the estimated compositional history of Job, it is just possible for a later redactional addition to have been made, but not likely. See discussion here; I agree with it that IF there were an earlier version, the "whirlwind speech" of 40-41 in general was likely not part of it. 

Mainly, though, I agree that, given the prose section is clearly older, there would have had to have been SOME prose conclusion. And, there's no way of knowing whether the current and original one was the same. We DO know that, by the time of scrolls being saved at Qumran, the current prose ending was where it ended.

The correspondent, who appears to be like me, a secularist with a graduate religious degree, seemed to be looking for an "existentialist" Job. Albert Camus is in the top rank of my philosophy pantheon. I've read a fair amount of Kierkegaard, some Sartre, and in even more modern times, lots of Walter Kaufmann. It's one thing to wish for that being true; it's another thing make unsustainable redaction-critical claims to that end.

As for one other claim there, I also don't believe David Clines' insinuation (page 7 of the PDF) that there was no wager between Yahweh and (the) Satan. (Here's the homepage to download the PDF if needed.)

Rather, as I said elsewhere on the thread, gods wagering with one another is a common enough thread in antiquity, and not just in the Ancient Near East, but in Greek myth, and also in the blinding of Baldur in Norse myth that it probably has its own subsection entry in Stith Thompson's encyclopedia of folklore motifs.

I think there was a bet, and as I said in my review of "God: An Anatomy," by Francesca Stravrakopoulou (saying she gets Job wrong, too), that, the wager may have been, if Satan won, he got to sit on Yahweh's throne a week or something. And, no, that's not being facetious. Then, when this thread started, I figured Yahweh's side of the wager would be that, if he won, Satan had to ONLY "wander the earth to and fro" for a while and couldn't sit in on the divine council. (Doorknob forgive me for sounding like David Heiser.)

The problem is, as I see it, is not only that the wager idea isn't spelled out completely, in the presumably older prose stratum, but that the shift to a monotheistic framework makes the whole divine wager more problematic when it's fused with the patient sufferer poetic narratives. (Clines is right, IMO, that Yahweh is the ultimate beneficiary of Job's suffering, but IMO, that doesn't make much sense if you're denying a wager was laid.)

And so, I stand by my comment to the correspondent that, even without Paul citing a mix of Isaiah and Job in his doxology at the end of Romans 15, Job is problematic at best. Reading the book either with or without Chapter 42, he looks like a capricious cad and you're in the middle of the problem of evil. Eliminating Chapter 42 is no answer otherwise. Rather, the correspondent's claim that Yahweh's monologue is "no answer" is wrong. Rhetorical questions at staccato tempo and high volume are indeed an answer.

With chapter 42, to put it in today's terms, Job as a whole reads to me like capriciousness being covered up with a success gospel conclusion.

The prose beginning, with the implied wager, is that Job is faithful precisely because, at least in modern dual-omni god terms, he doesn't have to fear god's capriciousness. In other words, the "natural evils" portion of "the problem of evil" is something that he doesn't have to worry about. That said, given the Chaldean raiders, Job faces both natural and human evils in chapter 1, but the ancient author probably wasn't thinking of the problem of evil.

The real problem, per the "see discussion here" is that Job is internally jumbled. By Chapter 10, Job himself is saying that he can't call Yahweh to account, but yet he hints at trying anyway, and later calls out for a "defense attorney" (NOT "redeemer"). And, of course, there's the problem of Elihu jumping in out of nowhere, without either being introduced earlier, OR without being listed in need of expiation in Job 42.

There's the option of going beyond C.L. Seow, Clines elsewhere and others, and postulating that Job originally ended at 31:40 with perhaps some brief speech by Yahweh, not Elihu's five chapters followed by Yahweh's four-chapter blast. That might satisfy my existentialist friend's ideas, but, if true, would have to be early indeed in the redactional history. And, it's not the theory he presented.

Otherwise, the archaicizing language? Assuming that it is an affectation, that makes sense as far as this being a post-exilic book. The (primary/original) author is trying to provide the idea of a sage of antiquity bringing wisdom to emerging Judaism. That "emerging Judaism" as well as looking for more orthodoxy could explain the addition of Elihu. Interestingly, C.L. Seow, cited by my correspondent as believing Job 42 is an addition, thinks the Elihu speeches are original. So does the author linked there, Ragnar Andersen, who doesn't explain why Elihu is missing at both beginning and end prose segments.

There's other problems. While Elihu's speeches do foreshadow Yahweh's in talking about divine power, they don't really offer anything different than the original three friends on the problem of evil and Job allegedly having a secret sin. It is possible that the foreshadowing is why Elihu's not seen in need of expiation, and just possible that this is why he's not mentioned with Job's other friends at the start. It's still awkward literarily.

That's more than enough.

The real puzzler is why, if under my idea, the "divine gamble" idea is at least halfway botched when moving it to a monotheistic deity, Job became "canonical" for Jews. For dual-omni Christians following in Paul's misinterpretation and misthinking tracks, it's a different story.

Also, as I said to a first-time questioner there asking about Ecclesiastes being "existential" or "nihilist" (after telling him the two are not the same) that I'm hesitant about using modern philosophy terms to describe the background or authorial mindset of biblical books, starting with the much different metaphysics. If you mean "existential" in a pop psychology sense, I get where you're coming from, but I'm then going to say that you need to treat the biblical book in question like pop psychology. (That's done plenty enough anyway.)

And, that's more than enough on Job.