Logical Fallacies | Definition, Types, List & Examples
A logical fallacy is a common type of error that undermines the validity or soundness of an argument. Logical fallacies include both structural errors (i.e., formal fallacies) and errors of content or context (i.e., informal fallacies).
Although logical fallacies are often based on flawed reasoning, some are also used deliberately to mislead and manipulate.
This argument exemplifies a type of logical fallacy known as an appeal to authority. The speaker avoids responding to ethical concerns about AI in law enforcement by changing the subject to an expert’s endorsement.
The ability to recognize logical fallacies is essential to developing strong critical thinking and media literacy skills. This knowledge can help us avoid both committing logical fallacies and being misled by them.
Logical fallacy list (free download)
Download a list of some of the most common logical fallacies with concise explanations.
Logical fallacy list (Google Docs)
What is a logical fallacy?
A logical fallacy is a flawed approach to argumentation. Logical fallacies often result from honest mistakes, but they are sometimes used deliberately as disingenuous methods of persuasion.
Logical fallacies are errors in an argument’s approach to reasoning, without respect to factual accuracy. The essential problem that logical fallacies describe is that an argument’s premises don’t adequately support its conclusion.
An argument can commit a logical fallacy even if its premises and conclusion are true (e.g., “Exercise is good for you because engaging in physical activity benefits your health”). Likewise, an argument can be free of logical fallacies but include incorrect claims (e.g., “If all birds are invisible, and I own a parrot, then my parrot must be invisible”).
Logical fallacies are found in explicit arguments. However, the same flawed patterns of reasoning found in fallacious arguments can often be reflected in other forms of persuasive communication where an argument is only implied.
Types of logical fallacies
Logical fallacies are typically divided into two main categories: formal and informal.
- Formal logical fallacies are errors in deductive reasoning that make an argument invalid.
- Informal logical fallacies are flaws in inductive arguments that render them weak.
Formal logical fallacies
Formal logical fallacies occur in deductive reasoning (also called formal arguments), which begin with a general rule or premise and apply it to a specific case. The structure of a formal argument must follow the rules of formal logic, meaning that the premises must logically necessitate the conclusion.
A formal argument is considered valid if it would be illogical to affirm the argument’s premises and yet deny its conclusion.
An argument is invalid (i.e., it contains a formal fallacy) if it’s possible for the conclusion to be false even if all the premises are affirmed.
Premise 2: The streets are wet.
Conclusion: Therefore, it has rained.
This argument demonstrates the formal fallacy of affirming the consequent. Even if both premises are assumed to be true, the conclusion could be false. There are numerous reasons a street could be wet other than rainfall (e.g., street cleaning or a burst water pipe).
In formal logic, arguments are usually labeled explicitly as a set of premises and a conclusion. Formal arguments also frequently use symbolic notation to represent logical relationships (e.g., “¬” means “not,” and “→” means “implies”).
Informal logical fallacies
Informal fallacies are found in inductive arguments (also called informal arguments), which begin with specific observations and infer a generalization. Informal arguments can be found in many domains outside of academia (e.g., discussion forums, opinion articles, or legal debates).
A well-constructed inductive argument must have premises that all support its conclusion. An informal fallacy, or weak argument, includes at least one premise that doesn’t logically imply the conclusion.
Many informal fallacies fall into the category of fallacies of relevance, which attempt to persuade using irrelevant information. Fallacies of ambiguity, which distort the meanings of words, are another category of common fallacies.
“Making more natural lifestyle choices is the key to healing the planet. That’s why we make Harvest Delight cereal with 100% natural ingredients. Start your day by doing something good for yourself and the planet with a bowl of Harvest Delight.”
In this example, the term “natural” is used to refer to both an eco-conscious lifestyle and the absence of synthetic ingredients in a food product. In reality, the claim that a food is “natural” doesn’t imply that it’s produced in an environmentally friendly way.
What are common logical fallacies?
Logical fallacies can be found in various forms of persuasive communication, in contexts such as academic writing, political discourse, advertising, law, and business strategy. The following are common examples of fallacies that might be encountered in various contexts.
Red herring logical fallacy
Red herrings are distraction-based informal fallacies, also known as fallacies of relevance. Often used deliberately, red herrings can effectively divert attention from an argument’s weak points. Red herrings can be especially effective at distracting an audience if they are subtle, or if they shift attention to an emotionally charged topic or accusation.
The use of a red herring fallacy often indicates that a speaker is avoiding a specific question or topic. In this example, the candidate might be attempting to distract the audience from her unpopular or underdeveloped policies by shifting to a controversial subject that’s popular with her voter base.
Hasty generalization logical fallacy
The hasty generalization fallacy occurs when an argument draws a broad conclusion from a small, unrepresentative sample of information. Hasty generalizations can prompt us to make snap judgments based on insufficient or unreliable data.
In this example of a hasty generalization, a few outliers are used as the basis of an extremely broad generalization.
Straw man logical fallacy
The straw man fallacy occurs when one party deliberately presents a distorted, easily refuted version of the other party’s position. This deceitful debate tactic not only impedes constructive discussion but can also unfairly cast doubt on an opponent’s intelligence or moral character.
Speaker 2: My opponent is suggesting that we should eliminate free speech and that the government should control what people are allowed to say and think.
In this example of a straw man argument, Speaker 2 exaggerates, distorts, and oversimplifies Speaker 1’s position. The straw man version of Speaker 1’s argument is not only easy to refute but also portrays Speaker 1 as an irrational and untrustworthy person.
Bandwagon logical fallacy
The bandwagon fallacy, also known as argumentum ad populum (Latin for “argument to the people”), is based on the cognitive bias sometimes referred to as “groupthink.” Bandwagon appeals take advantage of the common human tendency to think that if most people believe something, it must be true.
In this bandwagon argument, the fact that many people hold a certain belief is presented as the sole rationale for accepting that belief.
Slippery slope fallacy
The slippery slope fallacy is the error of asserting that a single decision will trigger a sequence of events or a shift in values, leading inevitably to an exaggerated outcome. Fallacious slippery slope arguments typically lack supporting evidence and exaggerate the likelihood of the predicted outcome.
This example demonstrates how a fallacious slippery slope argument typically exaggerates the certainty of extreme adverse consequences without providing clear reasoning.
Logical fallacy examples
Examples of logical fallacies can be found in many everyday contexts. Fallacious reasoning is often used in marketing campaigns for persuasive purposes.
“It’s all up to you: support our green initiative or face a dark future.”
The slogan employs a false dilemma, presenting a misleading and unrealistic choice between two options. The ad suggests that the future of the environment rests entirely on consumers choosing to give this oil company another chance by supporting its “green” initiative.
Beyond marketing campaigns, fallacious reasoning often surfaces in many other forms of persuasive communication that we’re exposed to daily, especially in the realm of news media and political discourse.
While it’s true that education funding can contribute to improved communities in many ways, this argument implies that education funding is the sole, direct cause of reduced crime rates, overlooking other potential factors such as economic conditions and social programs.
This is an example of a questionable-cause logical fallacy, also known by the Latin name cum hoc, ergo propter hoc, meaning “with this, therefore because of this.” This post hoc fallacy is often refuted with the aphorism “correlation does not imply causation.”
Frequently asked questions about logical fallacies
- What is the difference between cognitive biases and logical fallacies?
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Cognitive biases and logical fallacies are distinct but related concepts that both involve errors in reasoning.
- Cognitive biases refer to inherent human tendencies toward specific erroneous thought patterns.
- Logical fallacies are errors in persuasive communication that undermine the validity or soundness of an argument.
Logical fallacies sometimes result from, or appeal to, cognitive biases.
- Is an appeal to ignorance a logical fallacy?
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Yes, an appeal to ignorance is a type of logical fallacy. It involves asserting that because something hasn’t been proven true, it must be false, or because something hasn’t been proven false, it must be true (e.g., “Scientists can’t prove that the Egyptian pyramids don’t have extraterrestrial origins”).
There is an aphorism that is often used to counter arguments from ignorance: “Absence of evidence is not evidence of absence.”
A similar mistake is the burden of proof fallacy, which occurs when someone makes a claim but doesn’t offer evidence, instead claiming that others must disprove it (e.g., “There’s a secret society manipulating world governments. Prove me wrong”).
- Is an ad hominem a logical fallacy?
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Ad hominem is the informal logical fallacy of attacking a person instead of refuting an argument. Based on the Latin “to the person,” ad hominems focus on irrelevant criticisms of an individual rather than making a good-faith rebuttal.
Name-calling is one common form of ad hominem fallacy. It’s used to dismiss an argument by simply ridiculing the individual presenting it (e.g., “Now that we’ve heard the bleeding-heart proposals from my naive young colleague, let’s move on to discussing realistic solutions”).
