fallacy

From Middle English fallaci, fallace, fallas, from Old French fallace, from Latin fallācia (“deception, deceit”), from fallāx (“deceptive, deceitful”), from fallere (“to deceive”).

• (Received Pronunciation, General American, Canada, General Australian) IPA^(key): /ˈfæl.ə.si/

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fallacy (plural fallacies)

1. Deceptive or false appearance; that which misleads the eye or the mind.

   Synonyms: deception, deceitfulness

   • 1749, Henry Fielding, The History of Tom Jones, a Foundling, volumes (please specify |volume=I to VI), London: A[ndrew] Millar, […], →OCLC:

     Mr Jones expressed great gratitude to the lady for the kind intentions towards him which she had expressed, and indeed testified, by this proposal; but, besides intimating some diffidence of success from the lady’s knowledge of his love to her niece, which had not been her case in regard to Mr Fitzpatrick, he said, he was afraid Miss Western would never agree to an imposition of this kind, as well from her utter detestation of all fallacy as from her avowed duty to her aunt.

   • 1834, L[etitia] E[lizabeth] L[andon], Francesca Carrara. […], volume II, London: Richard Bentley, […], (successor to Henry Colburn), →OCLC, pages 108–109:

     I no longer believe in happiness, because I see the fallacy of my first belief; and the examination which that induced, has shewn me the fallacy of all. Shew me a heart without its hidden wound.

2. (logic) An argument, or apparent argument, which professes to be decisive of the matter at issue, while in reality it is not; a specious argument.

   Synonyms: logical fallacy; see also Thesaurus:incorrect argument

   Hyponyms: formal fallacy, informal fallacy

   • 1983, Richard Ellis, The Book of Sharks, Knopf, →ISBN, page 163:

     Baldridge also showed the "one molecule of blood," usually held to be the stimulus for attracting sharks, to be another common fallacy, since a molecule of blood does not exist.

• fail
• fallible

• sophism
• Appendix:Glossary of fallacies

• “fallacy”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.
• “fallacy”, in The Century Dictionary […], New York, N.Y.: The Century Co., 1911, →OCLC.
• “fallacy”, in OneLook Dictionary Search.
• “fallacy”, in Merriam-Webster Online Dictionary, Springfield, Mass.: Merriam-Webster, 1996–present.
• “fallacy”, in The American Heritage Dictionary of the English Language, 5th edition, Boston, Mass.: Houghton Mifflin Harcourt, 2016, →ISBN.
• “fallacy”, in Collins English Dictionary.
• “fallacy” (US) / “fallacy” (UK) in Macmillan English Dictionary.