I have noticed several questions that deal with whether any Christian group allows or does not allow some practice or belief, and that these questions often go unanswered because it is difficult to prove a negative I.e. To definitively say that no group allows or disallows something. Is this considered problematic? My concern is that by not answering due to the phrasing of the question, we are not presenting Christian thought on why something is allowed or not allowed.
Of course, you are right that proving a negative is impossible. However, it's still possible to provide a good answer even when the answer's basic message is, "no, no such thing exists" (replace "thing" with "tradition" or whatever you are looking for). Such answers might:
- Demonstrate that an effort was made to find the requested thing
- Quote the writings of scholars who write on the subject, particularly those who explicitly or implicitly say that no such thing exists
- Describe things that might be expected to be answers, but actually aren't
- Describe things that are similar to the thing requested, but aren't quite the same
- Provide arguments for why the thing does not exist
Any of these five things by themselves will usually not be a particularly good answer (with the possible exception of #2). But by combining two or more of them, you can end up with an answer that, though it does not prove a negative, often is enough to be helpful to the person asking the question.
For example, this answer only provides #5, so it's not a particularly good answer (and it wouldn't be even if examples hadn't been found by other answerers).
On the other hand, this answer employs #1, #2 (arguably), and several examples of #4. Some might not find it particularly satisfying, but it is nonetheless a helpful answer to the question.