Definition

Noun: A logical fallacy is an error in reasoning or a flaw in the structure of an argument that renders the argument invalid or unsound. It is a mistake that undermines the logical connection between the premises and the conclusion.

Usage

A logical fallacy is identified when an argument's conclusion does not logically follow from its premises, even if the premises themselves are true. Recognizing these fallacies is crucial for critical thinking and constructing valid arguments.

Examples

• The argument "If you don't support this policy, you are unpatriotic" is a common logical fallacy known as a false dilemma.
• Detecting a logical fallacy in a debate can weaken your opponent's position.
• Her essay was persuasive but relied on the logical fallacy of appealing to emotion rather than facts.

Advanced Usage

• Formal vs. Informal Fallacies: A formal logical fallacy is a structural defect that can be identified by examining the argument's form alone (e.g., affirming the consequent). An informal logical fallacy is a content-based error that requires examining the meaning of the argument (e.g., ad hominem).
• In Rhetoric: While a logical fallacy indicates faulty reasoning, it can sometimes be used effectively in rhetoric to persuade an audience emotionally or psychologically.

Variants and Related Words

• Fallacy (n): A more general term for a false or mistaken idea, which includes but is not limited to errors in logical argumentation.
• Fallacious (adj): Describing something that contains or is based on a fallacy.
  • His reasoning was fallacious.
• Fallaciously (adv): In a fallacious manner.

Synonyms

• Faulty reasoning
• Flawed argument
• Sophism (a clever but fallacious argument)

Common Logical Fallacies (as Related Terms)

• Ad Hominem: Attacking the person making the argument instead of the argument itself.
• Straw Man: Misrepresenting an opponent's argument to make it easier to attack.
• Slippery Slope: Arguing that a relatively small first step will inevitably lead to a chain of related, extreme events.
• Appeal to Authority: Claiming a conclusion is true because an authority figure says it is, without other supporting evidence.
• False Cause (Post Hoc): Assuming that because one event followed another, the first event caused the second.

Noun

1. a fallacy in logical argumentation