Why do there exist "logical fallacies" that are not really consistent logical fallacies?

By logical fallacy, consider e.g. ad hominem.

By consistent logical fallacy I refer to a type of logical fallacy. Logical fallacies are "reasoning", which is thought to be improper, because it doesn't follow "consistency" in the argumentation context. Ad hominem can be thought to be a logical fallacy, because it's claimed to "refer to things that are not related to the context in hand". However, what or who decides, what's the "correct context in hand"? Can't this be pretty subjective? Thus it should be impossible to refer to "correct context" in a scientific way and thus ad hominem is not a consistent logical fallacy.

A consistent logical fallacy is such, which can be unambiguously interpreted to exist "the same way", every time it's claimed to exist. But recognizing logical fallacies should be difficult on its own, because of the difficulty of deciding "what's the correct current context of discourse". It's possible for people to manipulate it as well, simply "lie" about the context. Then what's the purpose of logical fallacies that are non-consistent? Since they ought to be perceived to have no consistency and are thus considerable as unscientific (not suitable for scientific practice).

Are there examples of consistent logical fallacies?

Some of the biases listed in e.g. this paper:


can be thought to have "significant" empirical backing. Could they be thought as scientific logical fallacies then? Because they have bio-psychological support. Still they may not be consistent by default, but rather through observation. However, the point is, these are based on "harder measures", rather than something like ad hominem, which seems almost as naive as "whether you like this person or not". Which should be, a matter of taste, for independent adult people. In a similar way as "whether I like this music or not". Implying "you don't like this person" a logical fallacy is absurd. It's like suggesting that "your musical taste is wrong".

  • My father says my scar was caused by a dummy (pacifier), my mother says it was a tooth. One of them is unintentionally wrong. Both are presenting arguments from.authority. Regardless, perhaps one of them is correct. An argument may be a fallacy, and still be true. Recognising bad arguments is only one aspect of discerning truth, it's not a science. Fallacy covers a broad range of bad argument.. some worse than others. – Richard Mar 27 '19 at 11:46
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    What you call "consistent logical fallacy" is usually called formal fallacy. Fallacies like ad hominem are called informal. The notion of formal fallacy, exactly because it is content independent, is not terribly useful: they are rarely committed, except by novices, and easy to spot, but most of real-life reasoning is informal. The lure of informal fallacies is that they are heuristically valid in some contexts (as with credibility), and deciding when can be tricky, as it ought to be. – Conifold Mar 27 '19 at 12:12
  • As an aside, I recommend avoiding nonstandard terminology (like "consistent logical fallacy") where possible, as it can be confusing to readers. You can always create and label new properties with letters, i.e. "property (A)" or "property (β)," and so forth. Then it will (usually) be clear that you are the inventor of this property for the purposes of a specific context... – Ben W Mar 27 '19 at 15:23
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    ...That said, Conifold's comment is pretty much spot-on, but I think it's worth adding that informal fallacies are instructive by considering specific examples. Being familiar with such examples can make you a better judge of other arguments. So, in answer to your other question, you decide the correct context, because you're the one evaluating the argument. – Ben W Mar 27 '19 at 15:23

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