Fallacies are a part of everyday life. Our brains are extraordinary biological computers, but they are not infallible. People believe all manners of absurd things, and the reason is often that they weren’t able to identify the errors in their own reasoning or in the arguments of the people who convinced them. You’ll often get a sense that something isn’t quite right if you’re faced with a ridiculous conclusion, but without identifying exactly what has happened it’s hard to refute. In other cases, it’s hard to even notice a fallacy if you’ve never consciously thought about it.
\#12 Appeal to authority
An excellent example of this fallacy is the notion that humans only use 10 percent of their brains. It’s been famously associated with Albert Einstein, and this association with the well-known genius is used as “proof” of the claim. In fact, Einstein was a physicist, not a neurologist, so although he is being used as an “authority” on the topic, he actually isn’t one and his reported conclusion is false. If a neurologist told you how much of your brain you use, and showed that he had significant knowledge on the topic, you should believe him – of course. The trick is to identify when someone is being evoked as an “authority” on a topic and to determine whether they actually are or not. Even experts can be wrong, but it’s obviously rare.
\#11 Ad hominem
This is when somebody attacks the individual they’re arguing with rather than the argument being put forward. If one politician criticises another’s policy on pensions in a TV debate, but is slapped down with “You’re only saying that because you’re in the pocket of the unions” or “My opponent has no ideas of his own, all he does is point out flaws,” the original argument has in no way been refuted. Instead, the argument is merely made to look bad because it’s associated with the individual. The criticisms of the pension policy, however, are unaddressed and therefore probably valid; no counter-argument is offered.
\#10 Correlation and causation
Imagine a study came out which found a correlation between listening to blues and cancer, meaning that out of equal numbers of blues listeners and non-listeners in the test, more of the blues listeners had cancer. If correlation is incorrectly associated with causation, you’d conclude that listening to blues causes cancer. Obviously that would be absurd, but the same fallacy is used in more subtle ways. For example, a correlation might be found between kids who play computer games and those who commit crimes later in life, but this doesn’t mean that games cause criminal behaviour. It could well be that other variables (like a turbulent home life) are responsible for the differences. However, when variables are controlled (such as in a clinical trial), denying the results for the above reasons is a fallacy in itself. For example, the tobacco industry claimed “correlation is not causation” for as long as they could with regards to the link between smoking and lung cancer.
\#9 Slippery slope
“If we let A happen, then Z will eventually happen, so A is bad.” This fallacy is used to say, for example, that if gay marriage is legalised, it won’t be long before incestuous or cross-species marriage is legalised. There are no reasons offered to support this apparently inevitable slippery slope, and as a result the statement is meaningless. Just because we’ve made it illegal to drink alcohol and drive doesn’t mean we’ll eventually make it illegal to drink anything and drive, or to drink alcohol anywhere at all. A does not necessarily lead to Z, unless there is an infallible, cause-and-effect argument which suggests that it will.
\#8 Ad-hoc reasoning
This is when new elements to an argument are basically added as-needed, on the spot, in order to justify continuing support for a conclusion. For example, if someone believes he has psychic powers, when confronted with a test he might mention that “I can’t perform at will, it only comes sometimes” or “it doesn’t work in the presence of sceptics, everybody has to believe.” Similarly, a Christian pressed on the lack of dinosaurs in the Bible but the presence of fossils, might add that “God put them there as a test” as an ad-hoc justification.
\#7 Straw man
The “straw man” is a flawed version of an opponent’s argument, constructed specifically to have something that can be effectively shot down. For example, if somebody supports additional funding for sciences, a straw man response could be, “I think it’s wrong to neglect national defence like that, the safety of the nation is paramount.” The original argument said nothing about reducing spending on anything, but the argument is re-phrased as something easier to shoot down.
\#6 Tu quoque
Tu quoque means “you too.” Or in other words, to avoid having to respond to criticism, the same criticism (or even something completely unrelated) is flung right back. Again, there is no response to the original point; it simply shifts the blame away from the accused.
\#5 Black or white
Presenting a complicated issue as a case of one thing or another is an easy way to make people agree with your viewpoint. For example, if a politician argues that it’s either a case of cutting benefits or allowing people to leech off the system without trying to find a job, they are presenting their hard-line approach as the only way to prevent abuse of the system. In reality, there are numerous things that could be done to rectify the issue and those are not the only two options. Things are rarely either black or white.
\#4 The burden of proof
Bertrand Russell’s celestial teapot is the perfect example of the burden of proof fallacy. He asserts that there is a tiny china teapot in orbit of the Sun between the Earth and Mars which is too small to be detected by current telescopes. Although you can’t disprove it (“the teapot wasn’t where you were looking,” “the telescope isn’t powerful enough” etc.), it’s still an absurd proposition to accept. The rule basically states that the burden of proof rests with those making extraordinary claims, and extraordinary claims require extraordinary evidence.
Related: The mysteries of Mars explained
\#3 Appeal to emotion
If the crying parents of a kidnapped young girl beg for the perpetrator to be put to death, tearfully relating the emotional turmoil they’ve been through and asking what kind of monster would do such as thing, some will be tempted to agree. However, appeals to emotion are basically appeals to irrationality – however horrible the individual is, your anger is not a valid argument in favour of the death penalty
When a word is used in an argument, it must be used consistently with the same meaning. If the definition of the word shifts and changes, it’s a fallacy of equivocation. LogicalFallacies.info uses the example that since Christianity teaches that faith is needed for salvation, and faith is irrational belief in the absence of or contrary to evidence, that Christianity rewards irrationality. However, the Christian definition of the word “faith” is simply belief in something (saying nothing about evidence), so the word is being used differently at different points in the argument. Because the Christian “faith” has been mixed with the “irrational” definition of the word, then it’s incorrectly concluded that Christianity rewards irrationality.
\#1 The fallacy fallacy
Imagine somebody makes the following argument: my favourite colour is blue, therefore the sky is blue. This is obviously a flawed argument (a non-sequitur, where the propositions don’t lead to the conclusion), but yet the conclusion is true. Just because there is a fallacious argument doesn’t mean that the conclusion is incorrect, so saying that something is a fallacy and therefore wrong is – in itself – a fallacy. The argument hasn’t been made well, but that doesn’t mean that the conclusion is definitely wrong, just that those specific reasons don’t logically lead to that conclusion.