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Logical Fallacies
LSnK Central
Created: 09-Jun-2006
Updated: 19-Jan-2008
Logical Fallacies
A logical fallacy is a reasoning error in an argument that makes it meaningless or useless. You should never be convinced by a fallacious argument.
Below I explain and exemplify some common logical fallacies. Knowing them will help you to avoid mistakes in your reasoning and better your logical faculties. Note that even intelligent people are prone to these mistakes; they're more prone since they have a greater ability to rationalise away errors. What's more, while fallacies are often used mistakenly they are also used as a deceptive tactic to persuade those ignorant of them.
It's wise to know them well.
Ad Hominem: Latin for against the man. Someone commits this fallacy when they deride their opponenent as if it were a legitimate argument against their position. The human tendency to agree with people who are on their side makes this a powerful persuader. But it doesn't matter whether the opponent is an idiot or not, it has nothing to do with the validity of their argument. It's the argument itself that must be examined, not the person making it. For example, calling someone a paedophile in an argument about child porn.
Appeal to Emotion: Using emotionally manipulative techniques to persuade someone that a position is correct, regardless of the logical value of the argument. It's an extremely prevalent practise in advertisements and politics. Appeals to emotion are often used in conjunction with other fallacies to enhance their persuasiveness.
Appeal to Faith: "You have to have faith to understand. Non-believers can't see the truth..." Arguments that rely on faith are basically asking you to abandon logic altogether and just accept the conclusion as true. It should be obvious that an argument relying on faith alone is useless. Reason is all we have as a means of understanding the world; faith is by definition a belief without evidence, something fundamentally irrational.
Appeal to Ignorance: Attempting to use an absence of evidence as evidence when an investigation has not been undertaken. For example, someone claiming that because we don't know that aliens haven't visited Earth, it's evidence that they have. However, if something has been extensively researched, it is perfectly reasonable to dismiss it if no evidence has been found to support it.
Appeal to Tradition: Arguing that something is ethical or efficient on the basis that it's been done in the past. Whether something has been traditionally done or not is irrelevant in isolation. It can seem persuasive because of the non-fallacious notion that the best ideas tend to survive for longer. But it's a tendency, not a fact; terrible ideas can and do persist as well. Slavery has been defended with this fallacious reasoning, for example.
Argument from Omniscience: Someone commits this fallacy when they claim that everybody knows and supports their claim, for example: "All people believe in something. Everybody knows that."
Association Fallacy: Arguing that an idea is wrong because some evil person has supported it. For example: "Adolf Hitler was a vegetarian, so vegetarianism must be a sign of an evil person." Hitler's evil actions had nothing to do with vegetarianism, so the argument is absurd. The converse of this argument is also fallacious. For example, "They called the Wright brothers crazy too; we're revolutionaries just like they were. This perpetual motion machine is sure to work!"
Bandwagon Fallacy: This fallacy is committed when someone argues that something must be true because a large number of people believe it. Of course this has nothing to do with the reality of the situation. An argument must stand on its own merits, not the number of its advocates; truth isn't a democracy.
Begging the Question: Begging the question is when someone uses what they're arguing for as the premise for their argument, a form of circular logic. This is often done by stating something, rephrasing it and then stating it again as 'evidence'. For example: "The Bible is correct about God existing; it says so and it was written by God." Such arguments are effectively little more than an unreasoned statement, but careful wording can hide the fact and make it seem convincing.
Biased Sample: This is when someone generalises a sample of information that isn't representative of the whole. For example, if you were to do a survey on the opinion of the American people on gun control, asking only NRA members and making a conclusion based on that would be fallacious.
Composition Fallacy: Arguing that something is true of a larger whole because it's true of a smaller piece of it. For example, arguing that hurricanes are harmless because air molecules are harmless. The opposite of this fallacy is the fallacy of division; arguing that something is true of a small piece because it's true of the whole. An example of this would be arguing that someone must be rich because they live in a rich neighbourhood, or that cells have consciousness because humans have consciousness.
Cum Hoc Ergo Propter Hoc: Latin for with this, therefore, because of this. This fallacy is committed when someone argues that events are causally related because they correlate. For example: "This guy went out and killed three people after playing Grand Theft Auto. Violent video games cause violence." No doubt many people also went to the toilet after playing the game, but that doesn't mean the game caused them to urinate. To back such a claim up requires additional evidence that would support a causal relationship.
Equivocation: Equivocation is when terms with more than one meaning are used in an argument have their meaning changed. For example: "There's no such thing as a dark feather, all feathers are light." The property in question changes from shade to weight, making the argument nonsensical and irrelevant. This fallacy can be employed much more subtly and to greater effect. An example: "Faith in God isn't irrational... You have faith in your fellow man, don't you? Isn't that rational? So isn't faith rational?" The second instance of the word 'faith' means a sense of confidence in the ability or nature of others, not a religious belief.
Fallacy Fallacy: Arguing that someone's position is incorrect purely because they've used fallacious arguments to try and support it. Of course, the conclusion may still be true without being established by the associated argument. Note that it's not a fallacy to be unconvinced by a poor argument; this fallacy is comitted when one rejects the possibility of its conclusion outright because it's been argued for poorly.
False Analogy: A false analogy is an analogical argument in which the entities used are too dissimilar to make a meaningful inference from. Even good analogical arguments are never rock solid. For an example of a bad one, consider Paley's watchmaker argument: he argued that the Universe is like a watch, and like a watch, it's logical to assume that the Universe was designed by something. The Universe is about as similar to a watch as a baked bean. While we've observed watches being made, we haven't observed anything remotely like that with regards the Universe.
False Dilemma: A false dilemma is created when it is argued that only two (or more) choices can be taken, but at least one other viable option exists which is excluded. It's also called bifurcation or a false dichotomy. As an example, consider George Bush's infamous quote: "You're either with us, or you're with the terrorists." Obviously there's another viable stance to be taken; neutral individuals aren't allied with either side. Either that or rocks are terrorists.
Gambler's Fallacy: Erroneously thinking that past events affect future ones in random sequences. For example, somebody watching a horse race might notice that one of the horses is constantly losing and instead of avoiding placing a bet on that horse, they bet on it because it's "Due for a win." The fact that a random sequence has recently followed a specific pattern does not mean it will change soon or continue. It's random!
Half Truths: A half truth is when someone describes something and omits information about it, thereby disguising its true nature. It's highly effective because the inclusion of some facts makes arguments seem more convincing, even if the facts aren't relevant. This is another fallacy that sees frequent use in politics and advertisements. Conspiracy theorists thrive on it.
Infinite Regress: An arguer commits this fallacy when their argument has an explanation which, itself, requires an explanation, which needs another explanation, and so on; the explanation is never adequately supported. Take this for example: "All things must have a cause. The Universe must therefore have a cause. The cause must be God." But if all things must have a cause, then God must have a cause, and its cause must have a cause, and so on forever. Nothing is explained, the argument is useless.
Jingoism: Irrationally appealing to patriotism. Take the American 'Patriot Act' legislation; its title has connotations of freedom and justice in America, but the content of the act serves to make it easier for the authorities to spy on citizens without due knowledge or consent, hardly an activity that the population considers patriotic.
Loaded Question: Loaded questions are assumptions formed into questions, which when answered imply that the assumption is correct regardless of a negative or positive response. A classic example is, "Have you stopped beating your wife yet?" Whether you answer yes or no, you answer that you have a wife and that you beat her. It's like begging the question in inquisitive form.
Meaningless Phrases/Questions: Phrases and questions that don't really mean anything, or are implicitly absurd or paradoxical. For example, "Nothing is impossible," or "How high is up?" or, "What colour is transparent?" and so on and so forth. A nonsensical concept can't be used to support an argument.
Misrepresenting the Facts: This is simply giving false information as the premise of an argument. Giving false information obviously makes an argument irrelevant to the matter at hand. Be that as it may, this can still be convincing because it appears logically correct and isn't always immediately obvious. Unfortunately, most people don't corroborate information they receive - especially if they agree. Verify facts for yourself; if you can't then don't make up your mind.
Non Sequitur: Meaning it does not follow, these are arguments with conclusions or inferences that don't follow from the premises. All fallacious arguments are non sequiturs. Example: "Those who don't support the president refuse to do so because they're unpatriotic; they hate our country." Or do they oppose the president because they like the country and think the president is ruining it? The conclusion doesn't follow.
Naturalistic Fallacy: (Appeal to nature) Inferring ethical values on the basis of whether or not something is 'natural'. But what has naturalness got to do with morality? The underlying logic is that anything natural is good and anything unnatural is bad. The illogic of this is clear and makes for an easy reductio ad absurdum. To take such an argument to its logical conclusion the arguer would have to consider technology, marriage and medicine wrong as well; none of them are natural, after all. Conversely, being perfectly natural, death would have to be considered good. This fallacy is also employed in many advertisements for food, with the implicit assumption that 'natural' food is healthier and more nutritious.
Observational Selection: The pointing out of only positive events when there are also negative ones or vice versa. Casinos attempt to induce this by design; loud sounds effects play whenever somebody wins, but no indication is given when someone loses. It appears as if many people are winning and that the odds are favourable, but in fact the losers greatly outnumber the winners (otherwise the casino would quickly go bankrupt). Not really a fallacy, but worth being aware of.
Phantom Distinction: This is when someone tries to make an argument based upon a distinction that isn't really meaningful, often by substituting inert terms with loaded ones. Imagine someone saying, "You're clearly delusional and depressed. The container isn't half empty, it's half full." The container is still at 50% capacity. Nothing comes of it. Another example: "Terrorists are just freedom fighters..." So what? Freedom fighters who blow up innocent people are still bad. It doesn't matter what they're called.
Poisoning the Well: Attempting to stop people properly considering an opponent's argument by using ad hominems, lying about them, or otherwise attempting to instil bias where there should be none. This is unfortunately par for the course in political arguments and even mainstream politics. In America there are entire campaigns based on it. Consider people's arguments on their own merits. It's easy to dismiss someone's argument because you think they're a shithead, but it only makes you a moron.
Post Hoc Ergo Propter Hoc: Latin for after this, therefore because of this. This is a common fallacy in which someone assumes that, because a certain event occurs before another, the first event is the cause of the second. However, one thing occurring after the other isn't necessarily sufficient reason to assert a causal relationship. Imagine the following for example: a primitive tribe beat their drums during an eclipse, and when the Sun inevitably becomes visible again they conclude that they caused it to return, unaware of the fact that it was a natural astronomical phenomenon and that their actions had no influence.
Red Herring: When someone attempts to change the subject in order to divert attention from an argument, it's a red herring. This is often achieved by introducing an unrelated but emotionally charged topic.
Reification: This is inappropriately treating abstract concepts such as relationships or arbitrary groups as if they have the properties of definite, 'solid' entities. Fine for illustrative purposes in writing, but not for logical arguments. For example, an advertisement announcing that you should "Use Natural-Herb X, because nature always knows best." Nature doesn't know anything; it's a concept that encompasses a wide body of things, not a sapient being.
Regressive Fallacy: Failing to consider natural fluctuations in things when determining their causes. This is a common fallacy that leads to many erroneous beliefs. For example, quack 'medication' like magnetic healing rings. Someone may use it and feel better, concluding that it works. But that isn't necessarily the case. The severity of illnesses and their accompanying pains tend to fluctuate over time. The most likely time someone will take some medicine is when their pain is at its worst. The pain will fluctuate and become less severe, leading them to believe that the medicine had some effect, whether it did or not.
Shifting the Burden of Proof: Changing who has to provide the proof in an argument. For example, "UFOs have abducted people. Prove it's not true!" The burden of proof rests with the positive claimant, in this example the person arguing that UFOs have abducted people. Not only is it illogical to regard something as true until it's proven false, it's also impractical to the point of silliness.
Slippery Slope Fallacy: Arguing that that one action will inevitably lead to another, which will lead to more unfavourable ones and that the latter are good reason to disallow the first, when in fact there's no definite evidence that the initial action will actually lead to the later ones. For example: "If we legalise marijuana, then we'll end up legalising LSD, then crack, and the whole country will end up addicts." Legalising marijuana doesn't necessarily lead to legalising cocaine, so it can't be used as a legitimate objection. Note how the improbability builds with each additional step in the proposed chain of events.
Special Pleading: This fallacy is committed when someone supports their argument by asserting that their argument requires special consideration, when the consideration is not verifiable or relevant. Someone may argue that "You're male, you can't understand the arguments supporting abortion." The implied reason is that males can't empathise with females because they can't get pregnant. at hand?
Statistics of Small Numbers: Or hasty generalisation. Erroneously generalising very small samples (typically personal experience) as being representative of the overall statistic. For instance: "I bought a Ford at the same time you did and it works fine. They're reliable!" Another example: "I went to a gay nightclub once, they were all going at it. Gays are obsessed with sex." One may as well roll a dice once and conclude that all the sides have the same number. The wholes in question are so large that the samples are almost completely irrelevant.
Stolen Concept Fallacy: Supporting an argument with a concept that is explicitly or by implication denying another concept necessary to the validity of the argument, and therefore the argument itself. Consider this example: "It's impossible to prove a universal negative." The proposition's stolen concept is in actually claiming to prove a universal negative itself. If it is impossible then it's meaningless, if it isn't impossible then it's false. Not a whole lot of use.
Straw Man: This is misrepresenting an opponent's argument and refuting the misrepresentation instead of the actual argument. For example: "The Theory of Evolution says that complexity in the Universe increases over time. The Second Law of Thermodynamics says that any increase in complexity is impossible. Hence, the Theory of Evolution is inconsistent with the laws of thermodynamics." To the ignorant this may seem convincing. However, evolution only applies to biological organisms and the law in question doesn't forbid localised increases in complexity. Furthermore, it only applies to closed systems, and the Earth is not a closed system unless you forget about a certain ball of scathing-hot radioactive plasmatirelessly pouring energy onto the planet.
Tu Quoque Fallacy: Latin for you, too. Arguing that because someone has done something contrary to what they're arguing for, their position must be false. In other words, that when someone is hypocritical their argument is wrong. Wrong, too bad. While it may be emotionally unsavory to be told killing is wrong by a murderer, the fact that they have done so does not mean they are incorrect.
Two Wrongs Make a Right: This fallacy is made when one assumes that when someone does wrong, another wrong balances it out. For example, when being repremanded, it's relatively common to hear schoolchildren argue that their actions are justified by other children engaging in the same activity. Many of us have heard cries of "She lied too!" or perhaps even said it. Another example is supposing that it's okay to do something wrong to someone because you think they would've done it to you. In all of these cases, what is occuring is the erroneous justification of wrongdoing based solely on the fact that others have done the same - the fact that someone else does something wrong does not make it right.
Unfalsifiability Fallacy: Making an argument based on premises that can't currently be tested. For example, imagine someone arguing that you should believe in their god because if you don't, you'll suffer for eternity after you die. But does the god even exist? Does that kind of afterlife even exist? If they did would you really suffer for not believing? The catch is, you can only find out by dying. This particular example is also an appeal to emotion, exploiting the fear of death and non-existence to persuade, despite being logically vacuous.