I was just asking Is it appropriate to ask for references and point to a blog with the same question and started to read http://blog.stackoverflow.com/2011/07/its-ok-to-ask-and-answer-your-own-questions/ which says: " To be crystal clear, it is not merely OK to ask and answer your own question, it is explicitly encouraged."

I do not feel very positive about following that rule at MO.

blog.stackoverflow.com says "For example, when I ran into a nasty issue with Java exploits in Google Chrome when browsing for images, I documented that on Super User by asking and answering my own question. Now, others can benefit from my misfortune β€” and best of all, I got new even better answers beyond what I offered! Overall, a huge win all around."

In that case, I totally agree. But on MO, it doesn't seem typical to have problems solved that will be used and improved much by MANY others. It more sounds like "Do you know how to solve this or that problem in analytic number theory? -- I can, see my newest paper on the arXiv!"

Do you think that posting questions to which I already know the answer in advance (as in the example above) is appropriate on MO?

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    $\begingroup$ One reasonable situation may be: "How do you prove $X$? I have a proof (sketch follows) but suspect a more elementary approach may be possible, and would appreciate such a proof or appropriate references". And obvious variants: "Would Euler have been able to prove $X$? Note my sketch uses $Y$, which was not available in Euler's time, etc." $\endgroup$ Jul 15, 2013 at 17:37
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    $\begingroup$ I could easily see someone asking mathoverflow.net/questions/93330/… who knew one of the proofs posted, but I would be surprised if someone knew all of the proofs posted. I think the variety of answers to that question was very educational and would be sad if questions of that form weren't posted simply because the person wanting to post them happened to know one way to solve them. $\endgroup$ Jul 16, 2013 at 1:04
  • $\begingroup$ Another way you can ask a question you already know the answer to is "I can prove $X$ under hypotheses $H_1, H_2, ...$ but I haven't been able to show that all of these hypotheses are necessary. Does someone have proofs or counterexamples?" $\endgroup$ Jul 16, 2013 at 1:10
  • $\begingroup$ @AndresCaicedo: The OP does not know the answer to the MO question in your example. She only knows an answer to the mathematical problem, but the question was not about a first solution to the given problem. Thus, such a question should be a totally valid MO question. $\endgroup$ Jul 16, 2013 at 8:24
  • $\begingroup$ @QiaochuYuan: same for your example (MO didn't let me add both of your names to my previous comment). $\endgroup$ Jul 16, 2013 at 8:25

2 Answers 2


The MO documentation did (I strongly believe but cannot find at the moment) contain a phrase like: "please ask only questions you actually have" in the sense that MO should be used (mainly) as a tool to get information one needs and not as a means to disseminate interesting information (there might be people that have a different opinion on this, but this is at least one not too rare point of view).

In that sense, no in general one should not ask a question whose answer one knows (before asking). And, I agree the phrase form the documentation encouraging posting question and answers should likely be modified for MO.

Related to the example you give (added to clarify, I mean the abstract one not your specific case I did not look into this in detail as this is a general request for discussion) there is a point in general SE documentation, which was not explicity in MO documentation I think but implictly understood to apply (interpreted properly): Avoid overt self-promotion. See https://mathoverflow.net/help/behavior for details.

Thus also under SE "rules" your specific example might be excluded.

That being said, I can imagine situations where it is still reasonable to ask a question where one knows an answer. In particular, if there are (or at least one suspects) multiple different answers possible. An example could be a list-type question where I would consider it as perfectly alright for OP of question to also contribute their own answer(s). (One might do so also in the question, but it can be clearer to maintain a clear distinction between question and answers.)

Or, if somebody where, say, interested in diffeent ways of proving the same result (while knowing one or some), to hava quetion 'In which ways can one prove this' and also answer 'This is one way.' would seem fine to me, as for most relevant matters it would be the same as 'Q: this is a way to prove this are there others?' no answer.

Also, the example that is mentioned in the blog-post was such that other answers than the one by asker where still possible (and it was sort of likely this was so).

Mainly, I would see an issue with question-answer packages of one person that are more or less finalized from the start on, without much reasonable possibility or even interest from OP of having others' contributions in addition.

To avoid confusion: Of course the situation for learning the answer after having asked the question is completely different and here one certainly should provide the answer, or make clear in another way that one no longer has a need for an answer (say via flagging for closure) but the former seem preferable. But as far as I understood this was not the question here.

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    $\begingroup$ I have nothing against unexplained downvotes in general, in particular not on meta, however in this case to have it without explanation makes it impossible to know for me if you find my position "too strict" or "too permissive" on this matter. $\endgroup$
    – user9072
    Jul 15, 2013 at 14:33
  • $\begingroup$ "please ask only questions you actually have" in the sense that MO should be used (mainly) as a tool to get information one needs and not as a means to disseminate interesting information. +1 for this, but it is in contradiction to the example in SE "It’s OK to Ask and Answer Your Own Questions" which is directly linked from the "Ask Question" page. $\endgroup$ Jul 16, 2013 at 8:26
  • $\begingroup$ I agree there is some actual contradiction here. I am not sure what will be the best way to resolve it. Perhaps there could be cases where it makes sense to document the answer to a question somebody knows/just learned and feels many others have too on MO. I do not know, say, some experts finds an obscure reference for somethings that used to be known as 'folclore' by 'everybody' but it was well-known 'nobody' knew where it actually came from. However, this should be very rare and tricky. I don't know, but assume (perhaps in error? anybody know this?) also on SO and other sites this is rare. $\endgroup$
    – user9072
    Jul 16, 2013 at 9:02

I don't know how acceptable this is on MO, this answer is mainly to clarify what is acceptable on other SE sites.

I think it is fine under SE rules to ask jeopardy questions or answer your own question even at the time of asking it. There used to be an item in FAQ stating that asking jeopardy questions is fine. SE seems to view its sites as building libraries of questions and answers by experts and with that view if you had a question and then tried to solve it (as we expect) and did solve it, it is fine to post the question and the answer at the same time. The option for posting an answer at the time of posting a question was added for this reason. Others might come up with better answers but that is not a required condition.

But that is different from self-promotion of one's own work, it is unlikely to be well received on any site. If you have posted something on arXiv then it is already accessible to others and posting a question to draw attention to it seems inappropriate.


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