fal·​la·​cy | \ ˈfa-lə-sē How to pronounce fallacy (audio) \
plural fallacies

Definition of fallacy

1a : a false or mistaken idea popular fallacies prone to perpetrate the fallacy of equating threat with capability— C. S. Gray
b : erroneous character : erroneousness The fallacy of their ideas about medicine soon became apparent.
2a : deceptive appearance : deception
b obsolete : guile, trickery
3 : an often plausible argument using false or invalid inference

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Did You Know?

Philosophers are constantly using the word fallacy. For them, a fallacy is reasoning that comes to a conclusion without the evidence to support it. This may have to do with pure logic, with the assumptions that the argument is based on, or with the way words are used, especially if they don't keep exactly the same meaning throughout the argument. There are many classic fallacies that occur again and again through the centuries and everywhere in the world. You may have heard of such fallacies as the "ad hominem" fallacy, the "question-begging" fallacy, the "straw man" fallacy, the "slippery slope" fallacy, the "gambler's" fallacy, or the "red herring" fallacy. Look them up and see if you've ever been guilty of any of them.

Examples of fallacy in a Sentence

The fallacy of their ideas about medicine soon became apparent. the once-common fallacy that girls just weren't any good at math
Recent Examples on the Web This fallacy serves as justification for the deprioritization of Black trans lives while classifying our fight for liberation as a distraction from theirs. Ashlee Marie Preston, Harper's BAZAAR, "The Anatomy of Transmisogynoir," 9 Sep. 2020 Ashley Rogers, executive director of Whitney Plantation, which is centered on the lives of slaves and opened in 2014, said it’s a fallacy to think that visitors did not want to hear about slavery all along. Andrea Gallo, NOLA.com, "A special Labor Day offer for you $6.99 a month for 6 months," 4 Sep. 2020 Investing in fossil-fuel alternatives may or may not be good policy, but pretending that the green jobs created by eliminating fracking jobs, for example, will create economic prosperity is the latest incarnation of a very old fallacy. WSJ, "Biden Will Turn Fracking Jobs to Green Ones," 31 Aug. 2020 Surely, the argument goes, their mismanagement exposes the fallacy of the populist promise. Yasmeen Serhan, The Atlantic, "The Pandemic Isn’t a Death Knell for Populism," 22 Aug. 2020 These self-conscious times have furnished us with a new fallacy. Katy Waldman, The New Yorker, "Has Self-Awareness Gone Too Far in Fiction?," 19 Aug. 2020 This fallacy is painfully common in politics and media perception. Dan Carsen, al, "Thinking about thinking (without the BS)," 2 Aug. 2020 And this type of fallacy and others are everywhere. Dan Carsen, al, "Thinking about thinking (without the BS)," 2 Aug. 2020 The first fallacy is founded on the philosophy that wages are set by supply and demand. Karan Chopra, Fortune, "We shouldn’t chase economic recovery; we should chase economic redesign," 9 July 2020

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'fallacy.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of fallacy

15th century, in the meaning defined at sense 2b

History and Etymology for fallacy

Latin fallacia, from fallac-, fallax deceitful, from fallere to deceive

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Time Traveler for fallacy

Time Traveler

The first known use of fallacy was in the 15th century

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Statistics for fallacy

Last Updated

18 Sep 2020

Cite this Entry

“Fallacy.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/fallacy. Accessed 22 Oct. 2020.

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More Definitions for fallacy


How to pronounce fallacy (audio)

English Language Learners Definition of fallacy

: a wrong belief : a false or mistaken idea
: the quality of being false or wrong


fal·​la·​cy | \ ˈfa-lə-sē How to pronounce fallacy (audio) \
plural fallacies

Kids Definition of fallacy

1 : a false or mistaken idea
2 : false reasoning

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