Unfalsifiability

This error in explanation occurs when the explanation contains a claim that is not falsifiable, because there is no way to check on the claim. That is, there would be no way to show the claim to be false if it were false.

Example:

He lied because he's possessed by demons.

This could be the correct explanation of his lying, but there's no way to check on whether it's correct. You can check whether he's twitching and moaning, but this won't be evidence about whether a supernatural force is controlling his body. The claim that he's possessed can't be verified if it's true, and it can't be falsified if it's false. So, the claim is too odd to be relied upon for an explanation of his lying. Relying on the claim is an instance of fallacious reasoning.