Five Ways Logical Fallacies Get Misidentified and Abused

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A logical fallacy is fundamentally an error in reasoning. Ardent practitioners of scientific thinking are probably aware of many of these fallacies and can point out when an opponent succumbs to one during a debate. However, the human mind is the irrational elephant in the room, causing many thinkers to misidentify and abuse logical fallacies over the course of a debate. Steven Novella, president of the New England Skeptical Society, pointed out a variety of these abuses in his book, The Skeptics' Guide to the Universe.What follows are five logical fallacies, along with descriptions of how they can be misused and abused.

1. Argument From Authority. Just because a group or person is an authority or expert does not mean that they are necessarily correct about a certain claim. To assert that something is true because an authority says it's true is a logical fallacy. However, too often people misapply the "argument from authority" fallacy to dismiss a solid scientific consensus. GMOs are safe. Vaccines don't cause autism. Earth's climate is changing and, at present, humans are the primary cause. Organisms evolved. These are all scientific facts touted by prominent scientific organizations based upon mountains of evidence. Claiming an "argument from authority" because somone referenced, for example, the National Academies of Sciences, doesn't change that.

2. Correlation and Causation. Correlation does not prove causation. To say that it does is a logical fallacy. However, correlation absolutely can be evidence for causation, the quality of which depends upon, for example, whether the correlation is actually feasible, how strong studies show the link to be (effect size), and whether or not the variables in question demonstrate a dose response (if X fluctuates, does Y also change in a predictable way?).

As Novella noted in his book, the tobacco industry once attempted to argue that smoking doesn't cause cancer because correlational studies can't prove it. Those studies, however, were so convincing that only an ideologue (or tobacco lobbyist) could deny their findings.

3. Ad Hominem. When you attack a person rather than their assertions, you are committing an ad hominem fallacy. It should be noted, however, that personal attacks aren't necessarily ad hominem fallacies. As Novella wrote, "If I impolitely state that someone with whom I disagree is a jackass, that's not an ad hominem fallacy. If I say their argument is wrong because they are a jackass, then that is a fallacy. But they may still be a jackass."

4. Argument From Ignorance. We don't know that something isn't true, therefore we should assume it is true. So goes a fallacious argument from ignorance. The fallacy can occasionally be massaged slightly into a much more palatable and seemingly wise saying: "Absence of evidence is not evidence of absence."

"While this sounds pithy, it's not strictly true," Novella writes. "Absence of evidence is, in fact, evidence of absence. It's just not absolute proof of absence."

5. The Fallacy Fallacy. It is itself a fallacy to reason that just because you proved an opponent's argument to be logically fallacious, you've shown their conclusion to be wrong. For example, someone could argue that evolution is true because the Earth is old. You could point out that their argument is a non-sequitur and claim victory, but you'd still be wrong if you're arguing against evolution. Evolution really happened.

It is also a fallacy to incorrectly claim that somebody else is using a fallacy, so brush up on your fallacies and always strive to remain intellectually honest and ideologically neutral!

This post was inspired by the recently-released book The Skeptics' Guide to the Universe, by Steven Novella, Cara Santa Maria, Jay Novella, Bob Novella, and Evan Bernstein. Those uninitiated to scientific and skeptical thinking will find Skeptics' Guide to be an engaging and in-depth introduction, while current practitioners will get their BS detectors honed and feel their love for rationality reinvigorated. Both groups will undoubtedly return to the Guide again and again to help navigate a world increasingly ignorant to fact.

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