As a general practise across different Stack Exchange communities, is it true that that one of these two questions should always be closed as a duplicate, since both questions have similar answers?

  1. "What is the capital of France?"
  2. "What is the largest city of France, in terms of population?"

The questions are clearly different, they only happen to have the same answer.

This issue came up recently when people tried to close one of my questions as a duplicate, and succeeded. I posted this comment:

Just because there are duplicate answers, that does not mean the questions are duplicates necessarily. "Paris" is the answer to both "what is the capital of France?" and "what is the largest city of France?"

To my amazement, some people responded that having a duplicate answer is enough of a reason to close a question as duplicate (some of these comments have since been deleted). They pointed to this meta post as the authoritative evidence to argue their reasoning:

How should duplicate questions be handled?

And they quoted:

Questions may be duplicates if they have the same (potential) answers. This includes not only word-for-word duplicates, but also the same idea expressed in different words.

Is it really the rule that different questions should always be closed if they have the same answers?

(I'm asking about the general and simplified case. The post that raised the issue for me obviously isn't quite as simple as the questions about France, and I don't want to get caught in the weeds of the specifics, my question post can remain closed as far as I am concerned.)

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    Well, except that quote specifically says "the same idea expressed in different words"... "largest" and "capital" aren't "the same idea". 200/20 = 10 and 2*5 = 10 but they're clearly not duplicates any more than this is... Heck, "largest" isn't even defined - largest in land area? population? – Catija Aug 27 '18 at 13:07
  • @Catija I clarified the example question to refer to population. – Flimm Aug 27 '18 at 13:12
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    You might be better off taking this to Unix & Linux Meta. While we do have guidance for this, each site has their own flavor of how to address it and the users and moderators there will likely be better able to explain why this example should be open/closed. – Catija Aug 27 '18 at 13:26
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    Yeah, this very much depends on the specific site. Some SE sites have a policy of dupe-closing based on having the same answer; others have a policy to dupe-close based on questions only. – Rand al'Thor Aug 27 '18 at 13:27
  • @Catija The meta post they used as the authority for closing different questions with similar answers was one posted on Meta StackExchange, so I think it needs to be raised here in Meta StackExchange. As I said, I'm interested in the general case, not in my particular post. – Flimm Aug 27 '18 at 13:28
  • There's no way to judge every case on the network based on one sample question that would probably be closed or downvoted for including no research whatsoever. Sites are allowed some leeway - canonical questions, for example... they're never going to be the same question but the answers are specifically designed to cover a broad collection of answers to help keep micro-questions like the ones in your example from being everything asked on the site. – Catija Aug 27 '18 at 13:33
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    See also my question about whether these questions actually exist. Spoiler: since "Paris" is an answer with no explanation and would be downvoted or deleted on most SE sites, it doesn't count for my criteria there. – Nathan Tuggy Aug 28 '18 at 2:30
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    /me votes to close "Are strings mutable in Java?" as a duplicate of "Is the moon made of green cheese?" – Robert Columbia Aug 28 '18 at 18:06

I will go out on a limb here and argue that those two are not the same answer. The word Paris happens to describe two distinct "ideas" (if you will).

I have seen this best described by Richard U in chat here:

Even if a common answer is "A pound", it doesn't mean "What is a unit of measurement that represents 16 ounces", "Where is a stray dog taken", and "What is the standard currency of the UK" are duplicate questions.

Wikipedia has lots of disambiguation pages to enlist the same word/term being used differently in different contexts.

A better example of two questions being duplicates for having the same answer would be:

  1. Which is the largest city in France in terms of population?
  2. In which French city do most people live?


  1. Which is the capital city of France?
  2. Which city houses most of the administrative setup of the French government?

Those are differently worded questions describing the same idea.

One of the reasons why we mark questions as duplicates is Search Engine Optimization (SEO), or in other words, to allow people posting different phrases into internet search engine box to arrive at their answer here. Marking questions as duplicates because they happen to have homonymous answers goes against it.


Each site has some leeway in this but in general, the questions, as that quote states, should be largely the same question.

If you asked the same question about the US or India, they'd quite clearly not be duplicate questions because the cities in each case aren't the same, so you wouldn't even be having this discussion in the first place.

So, there are a couple of alternate examples here that might be useful to keep in mind:

  1. What is the most populous city in France?
  2. What are the top ten cities in France by population?

I think you'd argue that these are duplicates, no? They're about the same subject, the same metric, one is broader than the other but they are the same and number 2 is more useful to a bigger audience because it has more information in it.

So, what if we compare question one with question three:

  1. What are the capital and most populous cities for each country in Europe?

These, too, are similar enough to be useful to a wide audience in a way the individual questions for each wouldn't be - they'd even be arguably less useful if asked individually because you'd have to find each one (and ask a new one if one didn't already exist), so sometimes grouping information is helpful - Wikipedia even has such a page for all countries.

On Stack Exchange, this would be called a canonical question. They can be difficult to get right but they're useful to sites that get many very similar questions that are generally answered the same way or that make more sense as a collection because of how related they are. For example, on Cooking, instead of having one question for "What's the difference between biscuit in American English and British English", there's a helpful glossary of differences between English variants all in one post.

Admittedly, in some cases, canonical questions can get too big and may be overwhelming for users, so it's important to balance the breadth of the canonical question with ease of use. If it's going to take 20+ minutes to sift through a giant answer to find the exact thing you're looking for, then it may be better to divide things up.

When it comes to an answer on one question being broader than the question needs and answers another question - as in the example:

Q: What is the capital city of France?
A: Paris is the capital city and also the most populous city in France.

If this is going to be a dupe target for "What is the most populous city in France?" I'd much rather someone edited the question to ask both than just outright closing the new question as a dupe. Why? Because that leads to a lot of potential for overreach with duplicate closures.

With this example question, this is very simple because both the question and answer are very brief, so handling both questions simultaneously is going to be more useful in the end than having two separate questions. It may even eventually turn into question three above if this one question starts spawning identical versions for every country in Europe. Yes, we should consider whether editing the question would invalidate existing answers or not... keep reading...

If someone asks a specific question that's complicated and needs a longer answer and someone goes out of their way to write an exhaustive answer that covers tons more information than the question asks for they may be obscuring the answer to the question asked in their long answer, making it less useful to the OP and others coming after and they may also be over-answering - broadening the question beyond what would normally be OK on the site.

Stack Exchange thrives on having multiple answers to the same question - we even look for it in determining which sites are ready to graduate from Beta. If someone asks a question that is answered in another, but only in one of several answers because that wasn't the intent of the original question, there may be alternate or even better solutions or explanations that are never addressed because of it.

This is what I encourage duplicate close voters to be wary of - they should ask themselves:

  1. Is this information so related that failing to include it does the question a disservice and most if not all of the existing answers already address it?
  2. Is this information added to an answer because it's an interesting related piece of information and only one person thought to mention it?

If it's the former, then the older question can probably be edited to include the new question and all of the best answers (rather than a single one) should have already taken it into account. If it's the latter, we're forcing the person asking the new question to filter through several answers to find the one that actually addresses their question and it may not even do so adequately. In this case, the questions should not be considered duplicates.


If "What is the capital of France?" was closed as a duplicate of "What is the largest city of France, in terms of population?" where an answer say

The largest French city is Paris, which is also the French Capital

then the duplicate would be ok because the answer there covers both questions.

That's on the 'It is easy to figure out my answer is there' side of the guidances for duplicates:

It depends how easy it is to figure out one example from the other.

Your exemple here is a little problematic as the answers are coincidentally related only and have no reasons to be the same, a more proper analogy would be a question about the reasons of Paris district 16th being the 16th closed as a duplicate of another question asking about how much districts are inner Paris where an answer address all districts and the reasons of their numbering.

Answering both question may raise a plagiarism problem for cases of where you search for a duplicate, think it worth being tailored to question and end up using the other answer as a start base. It also bring duplicated answers, from various persons on multiple question, each with its bit of specificity but spread this in multiple places less useful for future readers, closing as duplicate helps putting more complete answers on a unique place which are more likely to help future readers with their specific point also.

To continue on your exemple and assuming there's few answers covering more than just the largest city and capital, dropping a word of two about Paris population in time and how it is split in districts, then more questions can be closed as duplicate and answers can be edited to better address the new duplicate when needed, bringing a better overview for someone searching about the subject than separated answers on multiple questions with no link to each others.

  • The third paragraph answers my question, but I'm not sure I understand it. Are you saying "What is the capital of France" should be closed as a duplicate, or should not be closed as a duplicate? – Flimm Aug 27 '18 at 13:32
  • @Flimm it should be closed if the duplicate has an answer which already answer the question, so if the question about the largest city mention the largest city is the capital, then closing as dupe is the way to go. – Tensibai Aug 27 '18 at 13:33
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    Thank you for clarifying. I disagree. I don't think questions should be closed, just because there is a post somewhere out there that happens to contain the answer, even if the questions are completely different. – Flimm Aug 27 '18 at 13:36
  • As said above (under your question), there's per site policy, but the rule I'm with is that if there's an answer to the question, closing as duplicate and not repeating the other answer is the way to go, to avoid plagiarism of the other answer, and just to not waste time saying again what is already available. – Tensibai Aug 27 '18 at 13:37
  • @Flimm edited to give a better background of my reasoning and for the advantages of closing as duplicates – Tensibai Aug 27 '18 at 13:48
  • Thanks, I think your edited answer is clearer. (I deleted my previous comment) But I'm not sure I understand your new final paragraph. I think you're saying that we want to have one big answer post talking about Paris as both the capital and the largest city, and we want to close more specific questions as duplicates. Did I understand you correctly? – Flimm Aug 27 '18 at 13:57
  • Not always one big answer, this could be the case, but usually multiple answer tackling the problem from different perspectives, if a new question comes with yet another perspective and is mostly answered by answers in another, it's usually better to close as duplicate and add (or edit) an answer with this new perspective as long as it still answer both question of course. – Tensibai Aug 27 '18 at 13:59
  • @Flimm the objective here is to provide a useful repository of knowledge. If question A is adequately answered by the answers to question B, then answering question A does not increase the net amount of knowledge available on the site and is therefore a waste of effort. Closing as dupes is the right thing to do since that avoids wasting effort and provides an answer to the question. – terdon Aug 27 '18 at 14:08
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    @terdon Thank you for your comment. I think you're right about the objective. It's because I want more knowledge that I don't want to close different questions as duplicates. If I were to search for the "largest city in Paris", but I only ever got questions about the capital, the repository of knowledge would have failed me. "Paris is the capital of France" is a different piece of information than "Paris is the largest city in France". Closing questions prevents this new information from being posted, edited, voted on and so forth, or at leasts hides it and frowns upon it. – Flimm Aug 27 '18 at 14:14
  • @Flimm of course. But they are only dupes if the dupe target adequately answers the question. In your example, if the answer of the dupe states that "Paris is the capital and largest city of France". If it doesn't, then it doesn't answer the question so cannot be a dupe. But it would be much easier to have this discussion if you asked it on U&L meta, where it belongs. – terdon Aug 27 '18 at 14:17
  • @Flimm All closed questions can still receive votes, edits, comments... the only thing closing does is prevent answers. Closing as a duplicate points users to the other question where they can see if their version of the answer is already covered. – Catija Aug 27 '18 at 14:18

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