Based on the comments here, it's hard to place the line between using this kind of argument in good faith vs bad faith. I'd propose that the line can be drawn a

Based on the comments here, it's hard to place the line between using this kind of argument in good faith vs bad faith. I'd propose that the line can be drawn at using contradictory premises. If you make two arguments, and one depends on not having a dog while the other depends on having a dog with certain characteristics, then only one of these premises can be true. So you are making at least one of the arguments in bad faith. It gets subtle, though. Compare "I have no dog, and if I do, my dog couldn't have made those particular bite marks" to "I have no dog, and even if I do, no dog in the world could have made those bite marks". The first does have contradictory premises: it can't be true that I have no dog and that my dog's teeth have certain characteristics different from other dogs. The second does not have contradictory premises: It's possible both that I have no dog and that the person was bitten by a non-dog animal.