The logical fallacy of insisting on information that isn't required to determine the truth of something.
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Original Question
In argument people will demand that certain information needs to be known to determine the truth about a matter but that information may simply not be required because there is sufficient evidence to determine the truth without it, for example, people often focus on wanting to know motive when regardless of the knowledge of motive there is sufficient evidence to determine guilt and even if you know there is a motive and what that motive is, motive generally I'd say doesn't really have high evidentiary value in any case.
How would this logical fallacy be classified?
Comments on Question
This is an example of an appeal to evidence or examples that are not relevant to the argument at hand. It commonly appears as a last resort when evidence or rational arguments fail to convince the listener. Look up the term fallacies of relevance, which appeal to evidence or examples that are not relevant to the argument at hand.
Thanks, Shawn. I'm not sure one of those fallacies really fits. The thing is, it's not that the information isn't relevant exactly, it's that it doesn't need to be known because there's sufficient evidence to prove the case without it. We would expect the information to be there, just that it doesn't need to be found or explained.
While I do believe in many conspiracies, one event I believe to be as reported are the moon landings, an astonishing achievement. Moon hoaxers constantly demand that this or that piece of information needs to be known or explained but if the evidence provided is sufficient to make the case then all the pieces of the jigsaw don't need to be known because the jigsaw pieces available are sufficient. If, for example, certain pieces weren't available then it might be reasonable to demand the unknown pieces be found, for example, if there weren't masses of pieces of visual and audio evidence from the moon landings then certain information might need to be put forward to convince people they happened but as there are masses of pieces of visual and audio evidence, other information isn't necessarily required whether it's available or not.
Essentially, what moon hoaxers do is focus on elements of space they know very little about and make lots of assertions that this that or the other is impossible while ignoring the very clear artefactual evidence or they claim the artefactual evidence isn't genuine when they cannot put forward a good argument to make that case.
Answers
4YES! I was going to ask this question, but within 5 seconds I already knew that it's just a red herring. Asking for evidence for something that doesn't necessarily require evidence is a red herring 100%
I'm not sure that looking for a motive in addition to other convincing evidence is a logical fallacy.
I understand a logical fallacy to be something within an argument that leads to an error in reasoning (and that is generally presented to be deceptive). I don't see how adding a search for a motive (when a crime has been committed and other evidence support guilt) can be deceptive. The only way I can see a search for motive as leading to an error in reasoning would be for someone to claim that, despite all other evidence, the absence of motive means the individual cannot be guilty.
I know of no situation (but I'm far from an expert in criminal convictions) where absence of motive was accepted as proof of innocence. (Perhaps there are some, but I'm not aware of any.)
It seems important to note that criminal cases are not an exercise in proving innocence ... rather, they are exercises in proving guilt – and when it is not possible to prove guilt resulting, the accused is presumed innocent. In accounts I've read about criminal prosecutions, other evidence plus motive makes for a stronger argument for guilt than just the "other" evidence without motive. My guess (although it is just a guess) is that the search for motive comes from a desire to strengthen a case already supported by other evidence and not from an understanding that absence of motive means the person cannot be guilty. In other words, motive is a helpful factor in proving guilt, but not a necessary one.
I suspect that what you've described isn't a logical fallacy ... just a misunderstanding of why there was a desire to find knowledge of a motive in addition to other evidence.
I don't understand the question. Are you asking, for example, what is the fallacy if you are measuring distance and the other person claims the question cannot be answered unless you know the temperature?
Two possible examples came to mind
Example 1
John: In order to know whether A was guilty of homicide against B, we need to know A's motive.
Sally: That's not true. We only need to establish whether A was responsible for B's death. Based on the evidence, A hit B with a pick-axe, killing them. This clearly points to homicide.
John: We don't have A's motive, though, so we can't draw any conclusions.
John's argument is, "we don't have a motive, therefore we can't establish guilt." This is a non sequitur. Motive is irrelevant to whether the deed was committed or not.
Example 2
John: A may have been involved with B's homicide, but what about the motive? What if they didn't intend to do it?
Sally: Motive is not required to determine guilt.
John: But A's motive hasn't been established. You need evidence for that, too.
John is incorrect and trying to redirect the conversation. This is a red herring. We're focused on whether the deed was done or not, and he's trying to talk about intent.
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I don't know if this is a fallacy or not. For example, in the case of a murder trial, we know a murder has been committed and we may even know that the suspect is guilty. But in a court of law we also have to determine a motive in order to carry out sentencing. There is a difference between murder in the first degree, second-degree murder and manslaughter. All of these have to do with intent and not about whether the murder was carried out or not, or whether the person is guilty or innocent, but what was their motive or intent.