11 logical fallacies examples that undermine an argument

Great philosophers and rhetoricians throughout time have studied how to make compelling arguments and persuasive techniques that can undermine an argument. Errors in the structure of an argument are called logical fallacies, which many people usually make accidentally on a regular basis. By identifying and avoiding these fallacies, you can make more convincing arguments both at a business or academic level and during your daily life. In this article, we explain what logical fallacies are and outline some of the most common examples of logical fallacies.

11 logical fallacies that undermine an argument

You can find examples of logical fallacies every day in both formal and casual arguments. Here is a list of 11 common logical fallacies using the same basic statement to help you follow what logical flaws are occurring:

1. The anecdotal evidence fallacy

The anecdotal evidence fallacy is a common occurrence where speakers use anecdotes of their personal experience to justify a statement without facts or data. The speaker suggests that what they are saying is correct because they support it with experience. The speaker's experience may also have emotional baggage, which implies that the argument relies on emotional pressure to succeed. The following is an example of anecdotal evidence that includes an emotional attachment to try and support an argument:

Speaker: 'Bananas increase productivity at work because Person A ate bananas while they completed a piece of work for which they received an award.'

2. The bandwagon fallacy

This fallacy suggests that if many people agree on a point, that point is necessarily true. An argument's popularity does not prove the truth of a statement. It usually suggests that more people believe in a statement that could still be false. These fallacies are common and can cause both minor errors of judgement every day and serious problems when business leaders agree with untested statements based on popularity. For example, the argument below relies on the bandwagon fallacy of an argument's popularity rather than data:

Speaker: 'Most of our employees believe that eating bananas increases their productivity at work. Therefore, bananas must increase productivity at work.'

3. The correlation/causation fallacy

This fallacy occurs when a speaker suggests that correlation equals causation. It implies that two related events (correlation) necessarily have a cause and effect relationship between them (causation). Many events correlate due to other forces outside of those in comparison; therefore the two in comparison do not necessarily have a cause/effect relationship. In the below example, the speaker has presented two events as causally related when they may only relate in terms of time:

Speaker: 'Person A ate a banana for lunch today. After lunch, Person A finished twice as many tasks during the working day than usual. Therefore, Person A eating a banana increased their productivity.'

Related: Inductive reasoning in the workplace

4. The false dilemma fallacy

False dilemma fallacies result from the assumption that you can separate all arguments into two opposing views. Most arguments usually have multiple viewpoints. By representing an argument as a binary choice, critics can make speakers appear unreasonable and make their points appear weak or inflexible. Politicians often use this technique to make moderate and considered views appear radical. In the example below, a critic presents the speaker's point as a false dilemma:

Speaker: 'Eating bananas increases productivity.'

Critic: 'Either you believe that eating bananas doubles your productivity, or you believe there is absolutely no way that bananas could increase productivity.'

Related: How to mediate conflicts (With definitions and steps)

5. The straw man fallacy

The straw man fallacy is when a critic attacks an argument by attacking a weaker position that the speaker is not asserting. The name comes from the idea that instead of attacking the speaker, the critic sets up a straw man or scarecrow and attacks that straw man instead. Critics usually attack another weaker position than the speaker's so that their own position may seem stronger and win the argument overall. In the example below, the critic does not address the speaker's point but attacks a different perspective and still presents it as a valid counterargument:

Speaker: 'Eating bananas increases productivity.'

Critic: 'Eating an excess of bananas causes employees health problems.'

6. The slothful induction fallacy

Using the slothful induction fallacy, speakers often ignore substantial evidence in favour of claims based on irrelevant data or coincidences. They may deliberately ignore clear and convincing evidence to focus on their own weaker evidence that remains which the critic cannot disprove. Radical politicians and public figures often deploy this fallacy to promote misinformation and commonly refuted theories. Here, we see the speaker using slothful induction to resist the critic's argument:

Speaker: 'Eating bananas increases productivity.'

Critic: 'In a month-long trial of eating bananas at lunch, 98% of employees had completed no more tasks during the day on average.'

Speaker: 'The 2% of employees that did have their productivity increase are a positive confirmation that eating bananas increases productivity.'

Related: What is quantitative analysis? (With definitions and examples)

7. The ad hominem argument

A critic who attacks the speaker personally rather than attacking the argument itself is using a fallacy called argument ad hominem, meaning an argument against the man. Speakers using argument ad hominem usually hold a position that is difficult to defend and may lack evidence for their own points. As a result, they choose to point out the speaker's flaws since they cannot provide any evidence against their point. Here's a simple example of this fallacy:

Speaker: 'Eating bananas increases productivity.'

Critic: 'This speaker is unproductive in their job and is therefore not a valid source of productivity advice.'

8. The tu quoque fallacy

The tu quoque fallacy follows a similar idea to the ad hominem fallacy in that it focuses on attacking the speaker rather than the speaker's point. This fallacy is when a critic tries to demonstrate that the speaker does not personally behave according to the statement they are supporting. However, that they do not behave as if their statement is true does not prove that the statement is false, as there could be other reasons behind the speaker's behaviour. Here's an example:

Speaker: 'Eating bananas increases productivity.'

Critic: 'The speaker does not eat bananas despite knowing this. Therefore, I cannot believe their statement is correct.'

9. The no true Scotsman fallacy

This fallacy involves protecting a claim by changing its terms to invalidate counterexamples that critics put forward. The name comes from a famous example where the speaker amends "no Scotsman puts sugar on his porridge" to "no true Scotsman...". This implies that the counterexamples of Scotsmen who put sugar on their porridge are not 'true' Scotsmen by a subjective standard. Here, we have an example of this fallacy that follows the banana example rather than Scotsmen to help you understand it:

Speaker: 'Eating bananas increases productivity.'

Critic: 'In a month-long trial of eating bananas at lunch, 98% of employees had completed no more tasks during the day on average.'

Speaker: 'Those were poor-quality bananas. Only eating good-quality bananas increases productivity.'

10. The burden of proof fallacy

The burden of proof fallacy assumes the truth of a statement because a critic cannot disprove it, so many often use it for hypothetical arguments and abstract concepts. The fallacy allows the speaker to hold onto their opinions until a critic disproves them. This fallacy is popular in casual conversations as a way to end debates since disproving the speaker might require time which the critic may not give.

Speaker: 'Eating bananas increases productivity.'

Critic: 'That has never been tested or proven with data.'

Speaker: 'It has therefore never been disproven either, so the statement is correct until proven otherwise.'

Related: 6 Persuasive techniques to strengthen your writing

11. The appeal to authority fallacy

This fallacy results from a speaker using the authority of another party or themselves to force confidence in a statement. This is usually common in politics and speakers often use this technique when they show expertise in an unknown field. If a speaker lacks evidence, citing a known scholar or public figure often makes their argument appear stronger even though the known scholar may also be incorrect. Here's an example:

Speaker: 'A world-famous dietician has argued that eating bananas increases productivity.'

What is a logical fallacy?

A logical fallacy is an error in argument structure which, when targeted, can undermine an entire line of thinking. Targeting particular flaws in an opponent's logic is often a key technique that politicians, lawyers, philosophers and academics use in debates. Logical fallacies have two main categories. Formal fallacies are structural errors in a line of argument. Informal fallacies show that an argument relies on bad arguments and the use of misleading persuasive devices.

Related: Problem-solving skills: definitions and examples

How do logical fallacies undermine an argument?

Formal fallacies undermine arguments because they often imply that some part of an argument is not convincing. They may show that your argument depends on information that is either untrue or assumed to be true by the argument's structure. Informal fallacies can undermine arguments by suggesting they are based on poor evidence or rely more on persuasion than evidence. Formal fallacies often happen in structured debates and philosophy whereas informal fallacies are more common in the workplace and everyday conversations.