user6: We have a few of question on the site that are purely hypothetical, more like thought experiments. I don't want to pick on anyone specifically, but I'll add some examples to make clear what kind of questions I mean:

Would a plant need light if the chemicals gained by photosynthesis were given through the roots or as a foliar spray?
Could an organism theoretically produce a metamaterial-like structure? [closed]
If I put a cup over a spider, and leave it there for a day, will the spider survive?

Should these question be on-topic here? Where do we draw a line here?

user66: It depends. 
Thought experiments require broad knowledge in the specific domain, that makes these question non-trivial. In contrast to "look-up questions" (like this about galls) that theoretically can be answered by mere googling and reading available sources, the "though experiment" questions often require a solid knowledge base and those types of questions, in my opinion, are very much welcome here.
On the other side some questions might be too speculative (if there is too little known in the domain), non-ethic (experiments on humans, eugenics etc.) etc. But any question might be of these type, not specifically "mind experiment" questions.
This is why, at least in my opinion, there is no way to elaborate an unambiguous rule how to distinct "good" and "bad" questions in this case -- let's decide individually in every single case.

6: <p>We have a few of question on the site that are purely hypothetical, more like thought experiments. I don't want to pick on anyone specifically, but I'll add some examples to make clear what kind of questions I mean:</p>

<ul>
<li><a href="https://biology.stackexchange.com/questions/1100/would-a-plant-need-light-if-the-chemicals-gained-by-photosynthesis-were-given-th">Would a plant need light if the chemicals gained by photosynthesis were given through the roots or as a foliar spray?</a></li>
<li><a href="https://biology.stackexchange.com/questions/625/could-an-organism-theoretically-produce-a-metamaterial-like-structure">Could an organism theoretically produce a metamaterial-like structure?</a> [closed]</li>
<li><a href="https://biology.stackexchange.com/questions/910/if-i-put-a-cup-over-a-spider-and-leave-it-there-for-a-day-will-the-wolf-spider">If I put a cup over a spider, and leave it there for a day, will the spider survive?</a></li>
</ul>

<p>Should these question be on-topic here? Where do we draw a line here?</p>
 66: <p><strong>It depends.</strong> </p>

<p>Thought experiments require broad knowledge in the specific domain, that makes these question non-trivial. In contrast to "look-up questions" (like <a href="https://biology.stackexchange.com/questions/761/how-do-galls-form">this about galls</a>) that theoretically can be answered by mere googling and reading available sources, the "though experiment" questions often require a solid knowledge base and those types of questions, in my opinion, are very much welcome here.</p>

<p>On the other side some questions might be too speculative (if there is too little known in the domain), non-ethic (experiments on humans, eugenics etc.) etc. But any question might be of these type, not specifically "mind experiment" questions.</p>

<p>This is why, at least in my opinion, there is no way to elaborate an unambiguous rule how to distinct "good" and "bad" questions in this case -- let's decide individually in every single case.</p>
