The basic template of this argument is as follows:

One sample of a population says X. Another sample of the same population says Y. Y conflicts with X. Thus members of this population are inconsistent because they claim both X and Y.

I find this argument used very commonly, and it's obviously flawed. The error here, of course, is that there's no attempt made to see if there's any overlap between the sample that says X and the sample that says Y. So it's not clear that any significant number of individuals are holding these conflicting views.

Here's an example of an every day use of this flawed argument: "First conservatives say that banning guns won't do anything because the bad guys will get their hands on them regardless. But then they want to ban drugs so that people can't get their hands on them. They are inconsistent."

Is this a known logical fallacy?

  • I am not sure that your example fits the fallacy you are describing. It is known from polls that many conservatives favor both banning narcotics and not banning guns. Pollsters usually ask a number of questions, not one at a time, and correlate the data, there is no need to assume a correlation. This said, holding both views is not necessarily inconsistent, there can be reasons that justify banning one but not the other, indeed reasons that follow from conservative social philosophy (e.g. self-reliance and its impairment by drugs).
    – Conifold
    Jun 19 '17 at 20:37
  • @Coinfold I agree with you that it's not an example of the flawed argument I'm illustrating to say that conservatives are inconsistent for wanting to ban drugs and not wanting to ban guns. But it is an example of the argument if you stipulate that they appeal to the reasons illustrated in the quote for banning drugs and not banning guns. It may also be a straw man to even assume they use those arguments in the first place, but assuming you've heard some variant of those arguments from different sources it's then an example of the fallacy I'm asking about. Jun 19 '17 at 20:45
  • No, still not. We currently have Congressmen and have had Presidents who make those arguments, pretty much as supplied. You really need a better example, where the intersection cannot be filled by citing a given example, say, Nixon. Generalizing from a few examples to 'Conservatives' is unfair, but that is not part of your argument.
    – user9166
    Jun 19 '17 at 21:18

Assuming something false is not necessarily a logical fallacy (which has more to do with errors in reasoning than errors in fact), but there is a common cognitive bias that likely contributes to the kinds of bad arguments of which your example is one: out-group homogeneity effect. According to Wikipedia:

The out-group homogeneity effect is one's perception of out-group members as more similar to one another than are in-group members, e.g. "they are alike; we are diverse".

  • But there are logical fallacies that involve assuming something you can't infer from the information given. For example, affirming the consequent is making the false assumption that A -> B == !A -> !B. Similarly, the argument I'm referring to is the false assumption that A ⊂ C & B ⊂ C -> A = B or A ⊂ C & B ⊂ C -> A ∩ B != Ø.Granted, it's a specific case of that, though if there's a general logical fallacy for that statement I still want to know. Jun 21 '17 at 18:58

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