Logical Fallacies | Definition, Types, List & Examples
A logical fallacy is an argument that may sound convincing or true but is actually flawed. Logical fallacies are leaps of logic that lead us to an unsupported conclusion. People may commit a logical fallacy unintentionally, due to poor reasoning, or intentionally, in order to manipulate others.
Because logical fallacies can be deceptive, it is important to be able to spot them in your own argumentation and that of others.
Logical fallacy list (free download)
There are many logical fallacies. You can download an overview of the most common logical fallacies by clicking the blue button.
Logical fallacy list (Google Docs)
What is a logical fallacy?
A logical fallacy is an error in reasoning that occurs when invalid arguments or irrelevant points are introduced without any evidence to support them. People often resort to logical fallacies when their goal is to persuade others. Because fallacies appear to be correct even though they are not, people can be tricked into accepting them.
The majority of logical fallacies involve arguments—in other words, one or more statements (called the premise) and a conclusion. The premise is offered in support of the claim being made, which is the conclusion.
There are two types of mistakes that can occur in arguments:
- A factual error in the premises. Here, the mistake is not one of logic. A premise can be proven or disproven with facts. For example, If you counted 13 people in the room when there were 14, then you made a factual mistake.
- The premises fail to logically support the conclusion. A logical fallacy is usually a mistake of this type. In the example above, the students never proved that English 101 was itself a useless course—they merely “begged the question” and moved on to the next part of their argument, skipping the most important part.
In other words, a logical fallacy violates the principles of critical thinking because the premises do not sufficiently support the conclusion, while a factual error involves being wrong about the facts.
Types of logical fallacy
There are several ways to label and classify fallacies, such as according to the psychological reasons that lead people to use them or according to similarity in their form. Broadly speaking, there are two main types of logical fallacy, depending on what kind of reasoning error the argument contains:
Informal logical fallacies
An informal logical fallacy occurs when there is an error in the content of an argument (i.e., it is based on irrelevant or false premises).
Informal fallacies can be further subdivided into groups according to similarity, such as relevance (informal fallacies that raise an irrelevant point) or ambiguity (informal fallacies that use ambiguous words or phrases, the meanings of which change in the course of discussion).
“Some philosophers argue that all acts are selfish. Even if you strive to serve others, you are still acting selfishly because your act is just to satisfy your desire to serve others.”
At first, perhaps, this sounds reasonable. But notice how the word “selfish” changes meaning throughout the argument. When we say a person is selfish, we usually mean that they do not strive to serve others. To say that a person is selfish because they are doing something they want, even when what they want is to help others, is to use the term “selfish” with a substantially different meaning.
Formal logical fallacies
A formal logical fallacy occurs when there is an error in the logical structure of an argument.
Premise 2: The citizens of New York know that Spider-Man saved their city.
Conclusion: The citizens of New York know that Peter Parker saved their city.
This argument is invalid, because even though Spider-Man is in fact Peter Parker, the citizens of New York don’t necessarily know Spider-Man’s true identity and therefore don’t necessarily know that Peter Parker saved their city.
As such, even though both the premises of the argument are true, there is a flaw in the argument’s logical structure, which renders it invalid.
What are common logical fallacies?
A logical fallacy may arise in any form of communication, ranging from debates to writing, but it may also crop up in our own internal reasoning. Here are some examples of common fallacies that you may encounter in the media, in essays, and in everyday discussions.
Red herring logical fallacy
The red herring fallacy is the deliberate attempt to mislead and distract an audience by bringing up an unrelated issue to falsely oppose the issue at hand. Essentially, it is an attempt to change the subject and divert attention elsewhere.
Politicians often try to avoid difficult questions (e.g., on their own shortcomings) by raising an important but irrelevant issue like unemployment.
Bandwagon logical fallacy
The bandwagon logical fallacy (or ad populum fallacy) occurs when we base the validity of our argument on how many people believe or do the same thing as we do. In other words, we claim that something must be true simply because it is popular.
This fallacy can easily go unnoticed in everyday conversations because the argument may sound reasonable at first. However, it doesn’t factor in whether or not “everyone” who claims x is in fact qualified to do so.
Here, the argument is that the growing popularity of an idea is a sufficient reason to accept it as true. However, popularity alone is not enough to validate an argument.
Straw man logical fallacy
The straw man logical fallacy is the distortion of an opponent’s argument to make it easier to refute. By exaggerating or simplifying someone’s position, one can easily attack a weak version of it and ignore their real argument.
Person 2: “So you are fine with children taking ecstasy and LSD?”
In this example, Person 1 never suggested that it’s fine for children to do drugs. Person 2 takes the original argument to its logical extreme and creates an absurd, easy-to-defeat argument.
Slippery slope logical fallacy
The slippery slope logical fallacy occurs when someone asserts that a relatively small step or initial action will lead to a chain of events resulting in a drastic change or undesirable outcome. However, no evidence is offered to prove that this chain reaction will indeed happen.
In this example, there is no evidence that a prohibition on drugs will inevitably lead to the other policies that follow.
Hasty generalisation logical fallacy
The hasty generalisation fallacy (or jumping to conclusions) occurs when we use a small sample or exceptional cases to draw a conclusion or generalise a rule.
Here, there is insufficient evidence (i.e., the exceptional case of one person) to draw a conclusion (smoking is not that bad).
Logical fallacy examples
A false dilemma (or either/or fallacy) is a common persuasion technique in advertising. It presents us with only two possible options without considering the broad range of possible alternatives.
In other words, the campaign suggests that animal testing and child mortality are the only two options available. One has to save either animal lives or children’s lives.
However, this is a false dilemma, since there are other alternatives to animal testing in research. The campaigners choose to ignore this and play to their audience’s feelings instead, which is emotionally manipulative.
People often confuse correlation (i.e., the fact that two things happen one after the other or at the same time) with causation (the fact that one thing causes the other to happen).
It’s possible, for example, that people with MS have lower vitamin D levels because of their decreased mobility and sun exposure, rather than the other way around.
It’s important to carefully account for other factors that may be involved in any observed relationship. The fact that two events or variables are associated in some way does not necessarily imply that there is a cause-and-effect relationship between them and cannot tell us the direction of any cause-and-effect relationship that does exist.
Correlation is often used to infer causation because it is a necessary condition: that is, if A causes B, then A and B must also be correlated. However it is not a sufficient condition (i.e., A and B may well be correlated without having any cause-and-effect relationship).
Other interesting articles
If you want to know more about fallacies, research bias, or AI tools, make sure to check out some of our other articles with explanations and examples.
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Frequently asked questions about logical fallacies
- Is ad hominem a logical fallacy?
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An ad hominem (Latin for “to the person”) is a type of informal logical fallacy. Instead of arguing against a person’s position, an ad hominem argument attacks the person’s character or actions in an effort to discredit them.
This rhetorical strategy is fallacious because a person’s character, motive, education, or other personal trait is logically irrelevant to whether their argument is true or false.
Name-calling is common in ad hominem fallacy (e.g., “environmental activists are ineffective because they’re all lazy tree-huggers”).
- Is appeal to ignorance a logical fallacy?
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An appeal to ignorance (ignorance here meaning lack of evidence) is a type of informal logical fallacy.
It asserts that something must be true because it hasn’t been proven false—or that something must be false because it has not yet been proven true.
For example, “unicorns exist because there is no evidence that they don’t.” The appeal to ignorance is also called the burden of proof fallacy.
- What is the difference between cognitive bias and logical fallacy?
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People sometimes confuse cognitive bias and logical fallacies because they both relate to flawed thinking. However, they are not the same:
- Cognitive bias is the tendency to make decisions or take action in an illogical way because of our values, memory, socialization, and other personal attributes. In other words, it refers to a fixed pattern of thinking rooted in the way our brain works.
- Logical fallacies relate to how we make claims and construct our arguments in the moment. They are statements that sound convincing at first but can be disproven through logical reasoning.
In other words, cognitive bias refers to an ongoing predisposition, while logical fallacy refers to mistakes of reasoning that occur in the moment.
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