How to prove Proposition X in Y without Lemma Z?
Instead, they should be written to be self-contained (as Harry did):
]]>How to prove that F is true without H? (I'm asking because I'm reading Y and it has proposition X and the proof seems to rely on lemma K which doesn't require H)
Is every left fibration of simplicial sets a trivial Kan fibration?
I'm reading Lurie's Higher Topos Theory. Lemma 2.1.3.4 says blah blah blah, but I don't see where the proof uses this and that hypothesis. Can it be removed to strengthen the result?
You may also want to include something about (counter)examples you attempted to construct. If you also explain whether you think the result should be true without the hypothesis (something like "based on the intuition that contractibility gives you X, and a trivial Kan fibration is Y, it seems like you really need contractibility"), then I think it would be a great MO question.
In fact, I might even try to make the question more localized by turning your "I don't see why we need S_t to be contractible to extend f' as stated in the proof" into a question. (maybe that would be less localized; it doesn't really matter)
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