Question: The [Good Subjective/Bad Subjective guidelines](http://blog.stackoverflow.com/2010/09/good-subjective-bad-subjective/) talk a lot about what make for great questions and answers for subjective issues, and it primarily falls around Back It Up!: answers need to cite some kind of relevant material (scholarly works, authoritative discussions, relevant personal experience, something), and questions need to be written such that they encourage such answers.

And, of course, Back It Up! applies to objective questions and answers, too, the resources you use for backing those up just may be somewhat different.

So, we need to be pro-active, from the beginning, about demanding that answers Back It Up! This SE, in particular, I think, is closely tied to a lot of speculative fields – as several meta questions have already discussed, there are a number of SE sites that have significant overlap with this one, *but would not accept our kind of question* because of their speculative nature.

Thus, we need a policy, guideline, or at least discussion of what is too speculative, what questions cannot be answered in a way that Backs It Up! The “Primarily Opinion-Based” close reason exists for this, but we as a community have to decide where to draw the line for using it.

We also, as a community, need to enforce backing things up in answers. Everything about this endeavor is, by definition, highly speculative: the only way to be serious about this, to produce good answers, is to minimize, as much as possible, the “pure” speculation. Cite sources, compare to real-world history, sociology, physics, and so on. And flag or downvote answers that don’t.

Answer: 
Back It Up! *can* mean real-world history or physics or linguistics
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These are valuable fields that can give a fictional world a sense of realism, or at least credibility and verisimilitude. Answers that reference these things are often going to be better than those without them.

Back It Up! can mean *extrapolate* from reality
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Yes, many of us want to build worlds that are *unrealistic in specific ways* – but we are capable of reasoning how the things we *do* have experience with would react to this change. We can talk about building techniques, weapon technology, different social, ethical, and legal structures, linguistic developments, so on and so forth, to show how a given reaction to something new *fits in with all the things that are still the same.*

Back It Up! can *also* mean personal experience
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We want to encourage experience worldbuilders – people who have done it, who have put their work out there, have received feedback, who have seen what works and what doesn’t work. How great would it be to have a bestselling author or Hollywood movie director or prime-time television screenwriter answering questions? This is the kind of thing we want to encourage.

So someone could easily decide to Back It Up! not by citing journals or histories, but by talking about their own personal experience: what they have tried and put to the test and seen work or fail. What their fans have received well and what their fans have taken issue with. That would be a phenomenally backed up answer, and gets straight to the heart of the Good Subjective/Bad Subjective guidelines.

But failing to Back It Up! means you’re just guessing
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Every answer needs to justify the conclusions it comes to. “This sounds like a neat idea to me” simply *does not fit in well with how the Stack Exchange system works*. It probably is a neat idea. The next guy’s got another neat idea. How do I decide which one to vote for? They’re both neat ideas, so I guess I’ll vote for both? Or maybe just the one I happen to like more, because equal votes to everything make voting pointless. But then my vote is just going to my personal preference, that’s not right.

This is how the system breaks down when answers fail to Back It Up!. This is why we close questions that are Primarily Opinion-Based. It’s not (necessarily) that these are bad or invalid questions, or that these ideas aren’t neat. It’s that *the software that this website is based on is tailored for one specific thing,* and idea-generation *isn’t it.*
**This site is a site for asking speculative questions**  

If there was hard fact to back up a physics question, it would be on Physics.SE. If there was hard evidence on what benefits a Timelord's two hearts gave him, then it would be on Biology.SE. 

**That said...**  

If you have work that you draw upon or facts that you used to help make an estimate, please share your sources. I am always happy to see a question filled with links to aid in speculation and cause and effect, however I do not believe that this should not be a barrier to someone who has an insight or understanding that they can contribute.

Frankly, I believe that insisting upon sources for speculation and imagination will not only be detrimental to this site, but would *probably kill it*.

Sources:

* Gut feeling