fallacy
FAL-uh-see
/ˈfæl.ə.si/
A mistaken belief, or a flaw in reasoning that invalidates an argument.
Can refer to a structural flaw in logic (formal fallacy) or a deceptive trick in rhetoric (informal fallacy, like an ad hominem attack).
The story behind the word. From Latin 'fallere', meaning to trip up, trick, or deceive. In classical rhetoric, a fallacy was viewed as a mental trap designed to trip up an opponent during public debate.
Word relationships
- misconception: A misconception is a mistaken idea; a fallacy specifically involves faulty reasoning or logic.
- delusion: A delusion is a persistent false belief held despite overwhelming evidence, often psychological.
- truth: Truth represents accurate reality, whereas a fallacy is an error in reason or belief.
- validity: Validity means correct logical structure, the opposite of logical fallaciousness.
Commonly confused with
- phallacy: 'Phallacy' is a common misspelling; the correct spelling begins with 'f'.
Word family
- fallacious (adjective): Based on a mistaken belief or unsound reasoning.
- fallaciously (adverb): In a manner that contains a logical fallacy.
Collocations
- logical fallacy
- popular fallacy
- fallacy of composition
- commit a fallacy
Idioms & expressions
- fallacy of the single cause
Example sentences
- "The fallacies of relevance are arguments where the premises are logically irrelevant to the conclusion." Science Communication (Carl Sagan, The Demon-Haunted World)
- "Attacking the speaker's character rather than answering their point is a classic logical fallacy." Political Debate
Memory hook
FALLACY sounds like FALSE + ALLACY: a fallacy makes an argument FALL flat because it is FALSE. A fault that trips up your reasoning.
When not to use
Do not use as a simple synonym for an honest factual error like a typo or misreading of numbers.
Fun facts
- Medieval philosophers cataloged over 100 distinct logical fallacies in Latin, giving them memorable names like 'Argumentum ad Ignorantiam'.
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