!!'''[[http://en.wikipedia.org/wiki/Fallacy_fallacy The Fallacy Fallacy]]''':
!!! Also called
* Appeal to Fallacy
* [[StrawVulcan Mister Spock Fallacy]]
* Fallacy means Wrong
* Zeroth Law of Fallacies

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 ''makes no sense'', and this rule may seem like a {{mindscrew}}y special case, but...

->Tom: All cats are animals. Ginger is an animal. This means Ginger is a cat.
->Bill: Ah, 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 [[ShiftingTheBurdenOfProof 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 [[RightForTheWrongReasons 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 SoundValidTrue for a more complete explanation of this. There are reasons why extensive Critical Thinking courses exist.) This is related to how [[TropesAreTools 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 ArgumentumAdLapidem, which is when an argument is dismissed as absurd without explaining ''why'' it's absurd.