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 fallacies
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).
Formal logical fallacies
A formal logical fallacy occurs when there is an error in the logical structure of an argument.
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.
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.
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.
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.
Hasty generalization logical fallacy
The hasty generalization fallacy (or jumping to conclusions) occurs when we use a small sample or exceptional cases to draw a conclusion or generalize a rule.
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.
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).
