Sounds like a No True Scotsman but does not seem to fit its description.

For example:

"You'll know a true libertarian when he takes bribes from the government he hates"

The conclusion is wrong, being a good/true libertarian (or a libertarian period) has nothing to do with accepting bribes from the government, and the claimant is aware of the fallacy yet uses it anyways to discredit his adversary.

What fallacy would this be?

  • I am guessing that this is intended to insinuate that libertarians do not practice what they preach. "You'll know a true X" is just a sarcastic turn of phrase that has nothing to do with no true Scotsman, or the substance, but can be rhetorically effective. This particular smear tactic is known as tu quoque, appeal to hypocrisy, a special case of ad hominem attacks.
    – Conifold
    Sep 15, 2021 at 10:41
  • Even if the premise is false? I always thought Tu Quoque was about rejecting an argument based on a "you more!" attack based on a actually true, yet irrelevant statement (for instance: "you didn't get into the basketball team because you are too short" -> answer: "You are shorter than me!" - which is actually true, yet irrelevant).
    – Juan
    Sep 15, 2021 at 11:01
  • It is not like those engaging in smears particularly care whether some parts of them are true. They care to make them effective. And "they say X but do Y" is effective if the audience is inclined to believe that they do it, because of bad rep or a stereotype. That they actually do it may help, but is not at all necessary.
    – Conifold
    Sep 15, 2021 at 11:10
  • Indeed, but I am trying to identify the name of the fallacy. Do you still stand by Tu Quoque even if the premise ("accepting bribes is a sign of a true libertarian") is false? To clarify, let's forget the government thing. What if the statement was "you'll know he's a true Italian if you hear him speaking Japanese" (unfounded premise).
    – Juan
    Sep 15, 2021 at 11:46
  • "The fallacy focuses on the perceived hypocrisy of the opponent rather than the merits of their argument. This is a fallacy regardless of whether you really did it or not, but it helps if you really didn't do it", RationalWiki. Is it still a fallacy when it is too dumb to do any rhetorical work? Maybe not, but only because it is too dumb, not because the insinuation is false. At some point, sentences stop having even appearance of reasoning, or even making sense. To "you'll know a true pear if you see it eat grass" the only reaction will be "Huh?"
    – Conifold
    Sep 15, 2021 at 12:14

1 Answer 1


First of all, a statement by itself (to be qualified below) is not an argumentative fallacy, however abusive, insulting, unfair or irrational it might be. For a fallacy to be spotted, there must be an argument in the first place, whose premisses stated in support of a position ought to intendedly warrant the supported position stated in the conclusion. Nonetheless, not any error in the argument is reckoned as an argumentative fallacy: The inferential route connecting the premisses and the conclusion has to fall short of being reasonable in a certain manner.

Our present concern is the arguments offered unregimented in natural language discourse. It is a good practice to take a regimenting step keeping to natural language so that we obtain a schematic argument text to test for a fallacy. We may illustrate this by the fallacy of ad hoc rescue, or more colourfully known as, "no true Scotsman" in dialogue form. For the sake of clarity, we shall carry on in a somewhat formulaic fashion with artificial expressions:

X: All Scotsman is/does P.

Y: S is a Scotsman and S is/does not P.

X: Therefore, S is not a true Scotsman; hence, S is not a falsifying counterexample.

The contested statement here is that S is a Scotsman:

  1. In case that P is, as a matter of fact, a constitutive attribute of Scotsmen, then the act of appealing to purity is warranted and there is no fallacy.
  2. In case that P is (right or wrong) irrelevant to being Scotsman, then the act of appealing to purity is not warranted and there is a fallacy.

As for the first case, it might be objected that the appeal to purity is unwarranted, just as a three-legged dog is still a dog despite the fact that anatomy dictates that a dog is a four-legged animal. But a crucial presupposition is that there has already been a (communal, etc.) agreement on what amounts to being a Scotsman; that is why the exclusion of S is judged to be ad hoc (consider the oft seen condemnation of a horrible terrorist attack by the politicians of the terrorists' religion or nation: "Someone of our religion/nation cannot do that," appealing to religious/national traits).

If we treat the statement in question as an elliptical argument, we have to provide a context to it. I shall try one as follows:

X: A libertarian hates the government on the basis of her scepticism of political authority and power.

Y: Libertarians are opportunist people; a libertarian will not hesitate to take bribes from the government, once she grabs a chance.

X: S is a libertarian and he is a firmly principled man; he has refused such a bribe.

Y: If S were a true libertarian, he would take bribes from the government.

As analysed above, in case that P is, in fact, a constituent of being libertarian, then the act of appealing to purity is warranted and there is no fallacy, otherwise, there is. In general, a definition of libertarianism does not involve common morals, therefore, we can assert that the extra qualification is irrelevant.

It should be remarked that the context of the statements has to be made satisfactorily clear for a fallacy to be objective enough. This is the twist of argumentative fallacies. Notice that a similar statement may well be a matter of pride. For example, a Z plainly holds without an argument for or against:

Z: I am a true religious fundamentalist, I hate the infidel governments. Because of that, I have no objection to get any advantage of them. A true religious fundamentalist does not hesitate to take bribes from an infidel government [and use them in the way of our cause].

For further information on this topic, I recommend the sources classified under the headings of argumentation theory and critical thinking.

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