fallacy
FAL-uh-see
/ˈfæləsi/
A flaw in logical reasoning or a mistaken belief that renders an argument invalid.
Refers specifically to structural breakdown in logic rather than a simple misstatement of factual data.
The story behind the word. Stemming from Latin 'fallacia' (deceit or trickery), which comes from 'fallere' ('to deceive'). The word originally described deliberately deceptive tricks before narrowing in logic to describe broken reasoning.
Word relationships
- misconception: 'Misconception' is a mistakenly held idea, whereas 'fallacy' implies broken logical reasoning.
- delusion: 'Delusion' implies severe psychological belief in unreality, whereas 'fallacy' is an error in formal or informal logic.
- validity: 'Validity' means logical soundness, while 'fallacy' represents logical defectiveness.
Commonly confused with
- error: An error can be a factual typo or miscalculation; a fallacy is a structural defect in logic.
Word family
- fallacious (adjective): Containing a logical flaw or false belief.
- fallaciously (adverb): In a logically flawed manner.
Collocations
- logical fallacy
- sunk cost fallacy
- expose a fallacy
- fallacy of assuming
Example sentences
- "Assuming that because two events happen simultaneously one must cause the other is a widespread logical fallacy known as false cause." Debate analysis
- "The belief that money can buy happiness is a common economic fallacy that ignores psychological research on human well-being." Skepticism and philosophy
Memory hook
FAL-lacy is FULL of FALSE logic that FAILS test. A flaw in logic that tricks you into a wrong conclusion.
When not to use
Do not use for a simple incorrect stat or factual mistake (e.g. saying 'Paris is in Spain' is a factual error, not a fallacy).
Fun facts
- The 'sunk cost fallacy' causes people to keep investing time or money into failing projects simply because they've already spent so much.
Explore more words
Take your vocabulary further with LangBlitz
Our English vocabulary app: FSRS spaced repetition, 5,000+ curated words across 119 topic groups, CEFR A1 to C2. Explore your mastery with the beautiful Vocabulary World feature.