In an argumentation where speaker A suggests an idea, we sometimes encounter this kind of fallacious proof from speaker B that speaker A's idea is bad (a very common form is known as passive-agressive behaviour of speaker B):

— I think that P is true.
— Yes but then it would make Q true. And you see, since Q is true, then [... long discussion... ] ... then it's absurd. Thus P is a bad idea.


  • in such situations, speaker B usually goes very briefly on the the fallicious implication P => Q...

  • ... but speaker B spends lots of time to describe how Q is bad, and thus the initial idea should be rejected.

What is the name of this kind of unpleasant proof?

This is usually disappointing for at least three reasons:

  • speaker A who generally didn't imply Q at all in his idea, sees the debate moving from discussion about P to a discussion about Q's drawbacks (even if, in an objective manner, P and Q are not really linked-to-each-other).
  • speaker A has the burden of proving that P and Q are unlinked, and the debate has then moved to something else than the original idea P
  • in such situations, anyone could be easily fooled by speaker B (except speaker A who studied the initial idea in detail and has the big picture in mind)


TL;DR: is there a name for this: speaker A suggests an idea P, speaker B fallaciously moves from P to Q, and demonstrate how Q is bad, instead of refuting P directly?

  • What does "bad" mean? If P is false and P => Q is valid there is no need to discuss P directly, it is false as well. If the reasoning involved in the generalization is similar to the original one, and it is just easier to see that generalized Q is false, the tactic is legitimate too. Being "unpleasant" or "disappointing" to a speaker is not a fallacy. If the speaker denies that P => Q (s)he should focus on undermining the inference. But discussion of P itself is in any case moot, refuting consequences is as legitimate as refuting "directly". – Conifold May 3 '18 at 22:29
  • @Conifold I'm speaking about cases where the link between P and Q is dubious (and cannot be in evidence). In such situations, speaker B makes a long discussion about how Q shoud be refuted instead of refuting P. This is fallacious. – Basj May 3 '18 at 22:32
  • You need to show how q is irrelevant to p in the first place. Perhaps p does bring forth q & the result is negative. You need to address the actual claim speaker b makes. You seem angry that this person always acts unacceptably when you speak. If you can prove his statements are irrelevant to what you are saying the advantage is yours. Your statement by the way is it true, false or you don't know? This also weigh in on rejections you may receive. You would be better off knowing the material well & showing how or why q is not in the picture. – Logikal May 3 '18 at 22:34
  • @Logikal Exactly. The point is that Speaker A has to interrupt Speaker B's long answer about idea P and clarify that P and Q are unlinked. Then the time is wasted by Speaker A having the burden of proof that P and Q are unlinked, instead of discussing of the initial idea, P. That's why I described it as unpleasant and wondered if there is a name for such kind of false proof? – Basj May 3 '18 at 22:38
  • The link may be dubious to you but not to your opponent, and they are entitled to make their case for it. There is nothing unfair about the burden of proof being on you if you claim that the inference is invalid. And your opponent is not obligated to discuss things the way you want them discussed. You may have to consider that there is no "fallacy" involved here, and set your feelings aside. – Conifold May 3 '18 at 22:45

You can name it anything you like. I would call it "wasting time," and immediately dig in on the P => Q that was their logic.

You could call it a Hasty Generalization or a False Generalization or a False Equivalence if you really wanted names. But the big issue is in how they managed to assert P => Q. The particular fallacy is really there, not in the following rambling about the consequences of Q. We can't name that fallacy in general because there's any number of ways to make that incorrect assertion, many of which have their own name.

In reality, the only issue that arises here is that speaker B got to spend time discussing how Q is bad. This wastes time, and might bias third parties. But it's not actually the fallacy itself. The fallacy is in the logic that wasn't correct.

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