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Fallacy Fallacy

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The Fallacy Fallacy:

Also called

  • Appeal to Fallacy
  • Mister Spock Fallacy
  • Fallacy means Wrong
  • Zeroth Law of Fallacies
  • Bad Reasoning Fallacy

Claiming that a position must be false because the argument used to get to that position is invalid or used a fallacy. It may sound like a rational thing to do since by definition a fallacious argument does not make sense, and this rule may seem like a mindscrewy special case, but...


Tom: All cats are animals. Ginger is an animal. This means Ginger is a cat.
Bill: You just committed the "affirming the consequent" logical fallacy. Sorry, you are wrong, which means that Ginger is not a cat.

Bill's rebuttal is an argument from fallacy, because Ginger may very well be a cat; we just can't assume so from Tom's argument.

In other words, pointing out somebody's fallacy is not fallacious in itself (you're doing it right), but using this as "proof" that their claim is false is the Fallacy Fallacy. Somebody arguing their point badly doesn't automatically mean they are wrong. The best you can say is that they have not convincingly supported it. This also applies to the Fallacy Fallacy itself: Bill's argument is a fallacy, but it would be the same fallacy to conclude that Ginger is a cat because of that, since Tom's only "proof" is not a valid argument.


It should be noted that the burden of proof applies here: if the only reason to accept a claim is a fallacious argument, accepting the claim anyway is unreasonable. If our null hypothesis is that Ginger is not a cat, Tom has given us no reason to change this assumption. As above, it may well be that Ginger actually is a cat, but logic doesn't decide what's true, it decides what makes sense.

Another excellent example of how a false argument is combined with a true conclusion: in medicine, pressure around the brain can cause severe headaches. Ancient surgeons assumed that it must be demons in the patient's head causing the pain, and that exposing them to light would kill them or drive them out; therefore, they drilled holes in the patient's skull. The end result relieved the pressure and actually did cure the headaches, even though their reasoning was entirely faulty.


An argument using fallacious reasoning is consequentially capable of being true. In logic, "invalid" (fallacious argument) and "false" are not synonymous (See Sound/Valid/True for a more complete explanation of this. There are reasons why extensive Critical Thinking courses exist.) This is related to how logical argument is used as a tool rather than as a fact-in-itself, and that logical validity can sometimes be surpassed by an objective scientific fact.

It should be noted that there are some exceptions: namely, fallacies of distraction or relevance. A Strawman argument may still have a true conclusion, for example, but by definition it is an irrelevant conclusion since it does not address the opponent's real argument. Demonstrating the opposing argument is a strawman is therefore a valid rebuttal.

Compare Argumentum Ad Lapidem, which is when an argument is dismissed as absurd without explaining why it's absurd.

See also Right for the Wrong Reasons, Dumbass Has a Point, and Don't Shoot the Message.


  • Any Straw Vulcan character is bound to be written as if "illogical" is a synonym for "wrong".
  • A good many theories about the world over the years including many scientific ones are mostly Wild Mass Guessing for their time that led to the right conclusions but for the wrong reasons. Freud's theories, for example, are sometimes useful but are based on dated inaccurate knowledge of the mind.
  • One of the standard examples of this is Continental Drift: Alfred Wegener was right in that the continents moved, but the process he postulated was dismissed by geologists as being absurd (and they were right). It was the discovery of the mid-ocean ridges and the trenches in the 1950s and 1960s that finally demonstrated the how of plate tectonics.
  • Of course, a proposition may fallaciously be declared correct due to an argument against it fallaciously declaring it incorrect due to a particular argument for it being fallacious, thus committing the Fallacy Fallacy Fallacy.
  • "Reason Bros" on the internet. These people have a working knowledge of other fallacies except this one. They look to find one fallacy in the other person's (or just one member of a group)'s argument (or something that looks like a fallacy) and will then declare themselves the winner when they have found one. Amusingly sometimes reason bros will be on the opposite side and you can watch amusing conversations about which persons argument has the most fallacies, quickly derailing the argument from its original topic.
  • Kinda inverting: Martin Gardner, the math popularizer, coined the Ycallaf, which is an argument that *looks* like a fallacy but is nevertheless true. (Beloved example: The otherwise fallacious 0=1-1+1-1+...=1-(1-1+1-)...=1 argument is actually valid when properly interpreted in the context of knot theory.) note 
  • Pointing out a slippery slope argument doesn't necessarily mean its impossible to slide down the slope or even unlikely. Indeed it is often much easier to metaphorically get from B-Z than from A-B.


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