Fallacies are faulty reasoning used in the construction of an argument. They make an argument appear to be better than it is. Here are some major fallacies of reasoning that you be able to recognize. All of the following fallacies are known as informal fallacies because they originate in a reasoning error. In contrast, formal fallacies, also known as non sequiturs, arise from the logical form of the argument. The following article introduces the most common fallacies.
In this video example we see rapid fire deployment of straw man, false dichotomy, and some formal fallacies on a kid who, impressively, recognizes each flaw of reasoning.
Remember that arguments begin with premises that are related to each other using valid forms of reasoning to arrive at a logical conclusion.
Once you have analyzed the parts of an argument, evaluate:
Is the reasoning faulty?
- If the error in the argument is in the logical connection between two premises in drawing a conclusion it is likely to be a formal fallacy, also known as a non sequitur.
- If the truth revealed by the conclusion is a cause-effect relationship, it may be a questionable cause fallacy.
- Does the reasoning neglect many other possibilities? The argument might be a false dilemma or slippery slope fallacy.
Is/are the premise(s) faulty?
- If the premise of the argument must assume the conclusion to be true then read the section on improper premise fallacies.
- If weak premises and incomplete information lead to a strong conclusion, the argument contains a weak premise fallacy, also known as a faulty generalization.
Are the premises and/or the arguments a distraction from the actual issue in question?
- If any part of the argument is irrelevant to the actual issue, a relevance fallacy or red herring is at work.
Are you still not able to identify the error in reasoning?
- Consult the comprehensive list of fallacies at Wikipedia or ask your instructor for assistance.
An error in the argument's form. Invalid logic is applied to the premises.
Fallacy fallacy. This is the inferrence that an argument containing a fallacy must have a false conclusion. It is entirely possible for someone to pose a bad argument for something that is true. Try not to get so caught-up in identification of logical fallacies that you are quick to dismiss a flawed argument—instead, try to make the argument reasonable.
- Example: "Some of your key evidence is missing, incomplete, or even faked! That proves I'm right!"
Syllogistic fallacies. There are many kinds of these. Syllogisms are generally three step arguments that use two premises to derive a conclusion. The premises and conclusion all take the form of categorical propositions that somehow relate two categories. These fallacies derive from incorrect application of logic. These fallacies are often more obvious if you draw a Venn diagram of the categories and shared features.
- Example: "All birds have beaks. That creature has a beak. Therefore, that creature is a bird."
- Form: All Z is B. This Y is B. Therefore, all Y is Z.
- Problem: B cannot be generalized as an exclusive feature of Z. Y could be an octopus.
- Example: "People in Kentucky support a border fence. People in New York do not support a border fence. Therefore, people in New York do not support people in Kentucky."
- Form: All Z is B. All Y is not B. Therefore, all Y is not Z.
- Problem: From the lack of shared B, nothing more can be logically implied about the features of either Z or Y. Z and Y may in fact agree on the desired outcomes for the question at issue but disagree over the means for achieving the outcomes.
The proposed conclusion is not supported by the premises.
Whereas formal fallacies can be identified by form, informal fallacies are identified by examining the argument's content. There are many subcategories.
Improper Premise Fallacies
Any form of argument in which the conclusion occurs as one of the premises.
Begging the question. Providing what is essentially the conclusion of the argument as a premise. You assume without proof the stand/position that is in question. To "beg the question" is to put forward an argument whose validity requires that its own conclusion is true. Formally, begging the question statements are not structured as an argument and are harder to detect than circular arguments. Some authors consider circular reasoning to be a special case of begging the question. In the following examples, notice that the question at issue answers itself without argument.
- Example: "This whole abortion debate about when human life begins is ridiculous. We should be thinking about the rights of the baby."
- The question at issue: Should with examine when rights begin under the law? Premise: Rights begin after a baby is born. Conclusion: The debate is ridiculous.
Circular reasoning. Formally, circular reasoning differs from begging the question by specifically referring to arguments in which the reasoner simply repeats what they already assumed beforehand in different words without actually arriving at any new conclusion. Circular reasoning is not persuasive because a listener who doubts the conclusion will also doubt the premise that leads to it. This may sound silly, but people make such statements quite often when put under pressure.
- "Whatever is less dense than water will float, because such objects don't sink in water."
- "Of course smoking causes cancer. The smoke from cigarettes is a carcinogen."
- "The rights of the minority are every bit as sacred as the rights of the majority, for the majority's rights have no greater value than those of the minority."
- "Everyone wants the new iPhone because it is the hottest new gadget on the market!"
- Note that this could be factually true in the situation that popularity was the sole driver of consumer desire for the new iPhone. Even so, it is still a fallacy of circular reasoning because its popularity must be logically explainable for reasons other than the conclusion.
- Video example
Loaded question. Asking a question that has an assumption built into it so that it can't be answered without appearing guilty.
- Example: Prosecutor to defendant: "So how did you feel when you murdered your wife?"
- The question at issue: Did the suspect murder his wife? Premise: "you murdered your wife." Conclusion: "you murdered your wife." Possible responses: Any answer that the defendant gives to "how did you feel?" could construed as admission that he murdered his wife. The best response is to point-out the fallacy and refuse to answer the question as stated.
Weak Premise Fallacies
These reach a conclusion from weak premises. Unlike fallacies of relevance, the premises are related to the conclusions and yet only weakly support the conclusions. A faulty generalization is thus produced.
Cherry Picking / Card Stacking. The presentation of only that information or those arguments most favorable to a particular point of view.
- Example: "I'm a really good driver. In the past thirty years, I have gotten only four speeding tickets." (What other kind of tickets has he gotten? How long has he been driving?)
Faulty/Weak analogy. Comparison is carried too far, or the things compared have nothing in common.
- Example: Apples and oranges are both fruit. Both grow on trees. Therefore, apples and oranges taste the same.
Hasty Generalization (from an Unrepresentitve Sample). A judgment is made on the basis of inaccurate or insufficient evidence. They are extremely common because there is often no agreement about what constitutes sufficient evidence. Generalization from one person's experience is a common example of this fallacy.
- Example: "My grandfather smoked four packs of cigarettes a day since age fourteen and lived until age ninety-two. Therefore, smoking really can't be that bad for you."
- Example: "Ducks and geese migrate south for the winter. Therefore, all water-fowl migrate south for the winter."
- Video example
No True Scotsman. Making what could be called an appeal to purity as a way to dismiss relevant criticisms or flaws of an argument.
- Example: Angus declares that Scotsmen do not put sugar on their porridge, to which Lachlan points out that he is a Scotsman and puts sugar on his porridge. Furious, like a true Scot, Angus yells that no true Scotsman sugars his porridge.
Questionable Cause Fallacies
The primary basis for these errors is either inappropriate deduction (or rejection) of causation or a broader failure to properly investigate the cause of an observed effect.
Correlation Without Causation / Cum Hoc. A faulty assumption that, because there is a correlation between two variables, one caused the other.
- Coincidence. The two variables aren't related at all, but correlate by chance.
- Third Cause. A third factor is the cause of the correlation.
Example: Young children who sleep with the light on are much more likely to develop myopia in later life. Therefore, sleeping with the light on causes myopia. (In 1999, this was conclusion was popularized by the media from a study containing such a correlation. It is more likely that myopia has a genetic cause and myopic parents use nightlights because they have poor night vision without their glasses.)
- Wrong direction. Cause and effect are reversed. Example: The faster windmills are observed to rotate, the more wind is observed to be. Therefore wind is caused by the rotation of windmills. Real Life Example: When a country's debt rises above 90% of GDP, growth slows. Therefore, high debt causes slow growth.
Gamblers Fallacy. The incorrect belief that separate, independent events can affect the likelihood of another random event.
- Example: After having multiple children of the same sex, some parents may believe that they are due to have a child of the opposite sex. (In reality, the probability is still 0.5.)
False Cause / Post Hoc. Treating coincidence of one event following another as causation.
- Example: Every time we wash our car, it rains. Therefore, if we wash our car today, it will rain.
- Example: Specific vaccinations are given at the same age that obvious symptoms of autism typically manifest. When some parents see their children diagnosed with autism shortly after receiving vaccinations they assume that the vaccinations caused the autism (even though the autism could have been diagnosed by a professional
- Video example
Single Cause Fallacy / Causal Oversimplification. It is assumed that there is one, simple cause of an outcome when in reality it may have been caused by a number of only jointly sufficient causes or a third cause.
- Example: The "Gateway Drug Theory" argues that marijuana usage leads to usage of harder drugs and has been a major justification for why marijuana laws should be highly restrictive. However, the same data could be explained by marijuana simply being easier to obtain and therefore more likely to be the first drug tried by people who were likely to become hard drug users for many other reasons such as genetic factors or simple illegality of marijuana making it attractive to risk-taking people.
- Example: Traffic fatalities were cut when the highway speed limit was reduced to 55 mph Therefore, the lower speed limit has resulted in safer highways. (The fact that people are driving less and seat belt laws were also passed may be equally or more important.)
These are distractions from the argument typically with some distracting sentiment that seems to be relevant but isn't really on-topic. Red Herrings are a specific sub-category Relevance fallacy that is distinguished by an intent to mislead often due the lack of a real argument.
Ad Hominem Argument. Rejection of a person's view on the basis of personal characteristics, background, physical appearance, or other features irrelevant to the argument at issue. Pay close attention to words that question an opponent's character. Examples: slob, prude, moron, embarrassing, stubborn.
Ambiguity. Using double meanings or other ambiguities of language to mislead or misrepresent the truth. Meaning in language can be so slippery that there are at least a dozen sub-fallacies including ambiguous grammar, equivocation, and quoting out of context (a tactic most often encountered on the Internet).
Appeal to Authority. This fallacy happens when we misuse an authority. This misuse of authority can occur in a number of ways. We can cite only authorities — steering conveniently away from other testable and concrete evidence as if expert opinion is always correct. Or we can cite irrelevant authorities, poor authorities, or false authorities.
Appeal to Emotion. The use of non-objective words, phrases, or expressions that arouse emotion having the effect of short-circuiting reason. Common examples include appeals to fear, flattery, outrage, pity, pride, ridicule of opponent's argument, spite, wishful thinking. Emotional appeals are also a powerful tool in propaganda.
- Example: A commercial for a security company that shows someone breaking into a home in the middle of the night.
- Example: "Any intelligent person knows... " (appeal to pride).
Appeal to Nature. Any argument that assumes "natural" things are "good" and "unnatural" things are "bad" is flawed because concepts of the natural, good, and bad are all vague and ambiguous. The person creating the argument can define these in any way that supports their position. Appeals to Nature also employ the begging the question fallacy (above).
- Example: This tobacco ad claims that their product is more natural and thus better for you.
- Example: This ad attempts to convince the reader that margarine, one the most processed foods in a grocery store, is natural and aligns with the readers assumed yearning for a simpler, better life in the country.
- The marketing copy for products in a store like Whole Foods is rife of appeals to Nature. Practice spotting them.
Argument from ignorance / burden of proof. It asserts that a proposition is true because it has not yet been proven false or a proposition is false because it has not yet been proven true. This type of argument asserts a truth and shifts the burden of providing counter-evidence onto someone else. Logically, we should remain skeptical and demand legitimate evidence from the person asserting the proposition.
- Example of two contradictory positions using this fallacy: "No one has ever been able to prove definitively that extra-terrestrials exist, so they must not be real." "No one has ever been able to prove definitively that extra-terrestrials do not exist, so they must be real."
- Video Example
Argument from incredulity (appeal to common sense). Saying that because one finds something difficult to understand that it's therefore not true.
Association fallacy. Inferring either guilt or honor by association. It is an irrelevant attempt to transfer the qualities of one thing to another by merely invoking them together. Sometimes fallacies of this kind may also be appeals to emotion, hasty generalizations, and/or ad hominem arguments.
- Example: An attractive spokesperson will say that a specific product is good. The attractiveness of the spokesperson gives the product good associations.
- Example: "Galileo was ridiculed in his time but later acknowledged to be right. Likewise, Dr. Andrew Wakefield's work demonstrating that vaccines cause autism will later be recognized as correct too." (Taking an unpopular position is no guarantee of its correctness. Additionally, the two scenarios are not comparable. Galileo was ridiculed by the Catholic Church. His scientific peers generally confirmed his work. In contrast, Dr. Wakefield's scientific peers have failed to replicate his observations and have invalidate his conclusions based on methodological flaws. The source of negative public opinion around Dr. Wakefield derives from valid expert criticism.)
Bandwagon / FOMO. The use of the fear of being "different" or "missing-out" is used to influence behavior.
- Example: "Twenty million people jog for their health. Shouldn't you?
Genetic fallacy. Judging something good or bad on the basis of where it comes from, or from whom it comes.
- Example: "You're not going to wear a wedding ring, are you? Don't you know that the wedding ring originally symbolized ankle chains worn by women to prevent them from running away from their husbands? I would not have thought you would be a party to such a sexist practice." There are numerous motives explaining why people choose to wear wedding rings, but it would be a fallacy to presume those who continue the tradition are promoting sexism. (page 196 of ref)
Ignoring The Question. Digression, obfuscation, or similar techniques are used to avoid answering a question.
- Example: When asked about the possibility of a tax increase, a senator replies: "I have always met my obligations to those I represent."
Missing the point / Irrelevant Conclusion. Presenting an argument that may or may not be logically valid and sound, but whose conclusion fails to address the issue in question.
- Example: The Chewbacca Defense from South Park.
Straw Man Argument. Appearing to refute an opponent's argument by instead creating an oversimplified or extreme version of the argument (a "straw man") and refuting that instead.
Texas sharpshooter. A conclusion is drawn from data with a stress on similarities while ignoring differences. An example is seeing localized patterns where none exist. The name comes from a joke about a Texan who fires some gunshots at the side of a barn, then paints a target centered on the tightest cluster of hits and claims to be a sharpshooter.
Tu Quoque Fallacy. Latin for "you too," is also called the "appeal to hypocrisy" because it distracts from the argument by pointing out hypocrisy in the opponent. This tactic doesn't prove one's point, because even hypocrites can tell the truth.
Informal Fallacies with Multiple Structural Problems
Composition / Division. The fallacy of composition infers that something is true of the whole from the fact that it is true of a part of the whole. The opposite reasoning is the fallacy of division.
False dilemma / false dichotomy / black and white. Reducing an issue to only two possible decisions.
- Example: Either we go to war, or we appear weak.
- Video example
Middle ground / false compromise / argument to moderation. Arguing that a compromise, or middle point, between two extremes is the truth.
- Example: Holly said that vaccinations caused autism in children, but her scientifically well-read friend Caleb said that this claim had been debunked and proven false. Their friend Alice offered a compromise that vaccinations cause some autism. (ref)
Slippery Slope. Moving from a seemingly benign premise or starting point and working through a number of small steps to an improbable extreme when many other outcomes could have been possible. Although this form of slippery slope is a sub-type of the formal appeal of probability fallacy (it assumes something will occur based on probability and thus breaks rules of formal logic), slippery slope arguments can take on many other forms and should are generally categorized as informal fallacies.
- Video examples: Don't Wake Up In A Roadside Ditch commercial and the children's book If You Give a Mouse a Cookie.
Special pleading. Moving the goalposts to create exceptions when a claim is shown to be false. Applying a double standard, generally to oneself.