fallacy

American  

[fal-uh-see] / ˈfæl ə si /

noun

plural

fallacies

1. a deceptive, misleading, or false notion, belief, etc..

   That the world is flat was at one time a popular fallacy.

   Synonyms:

   misapprehension, delusion, misconception

2. a misleading or unsound argument.

3. deceptive, misleading, or false nature; erroneousness.

4. Logic. any of various types of erroneous reasoning that render arguments logically unsound.

5. Obsolete. deception.

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fallacy British  

/ ˈfæləsɪ /

noun

1. an incorrect or misleading notion or opinion based on inaccurate facts or invalid reasoning

2. unsound or invalid reasoning

3. the tendency to mislead

4. logic an error in reasoning that renders an argument logically invalid

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fallacy Cultural  

1. A false or mistaken idea based on faulty knowledge or reasoning. For example, kings who have divorced their wives for failing to produce a son have held to the fallacy that a mother determines the sex of a child, when actually the father does. (See sex chromosomes.)

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Etymology

Origin of fallacy

First recorded in 1350–1400; from Latin fallācia “a trick, deceit,” from fallāc- (stem of fallāx ) “deceitful” + -ia -y ³; replacing Middle English fallace, from Middle French

Example Sentences

In such a predicament, many would fall prey to a mixed-up way of thinking called the “sunk cost fallacy,” which is best explained by telling a brief story.

From Literature

That would be a fallacy, but Mr. Bottum didn’t commit it.

From The Wall Street Journal

“There’s this fallacy that companies were lowering the bar,” she says.

From The Wall Street Journal

I place that term in quotation marks since, as many people have said and continue to say, the version of “debate” that Kirk popularized is a wrestling match in a mud pit of logical fallacies.

From Salon

Even neomercantilists have a little point buried in a heap of fallacies.

From The Wall Street Journal

Related Words

• deception
• falsehood
• heresy
• inconsistency
• misinterpretation
• paradox
• untruth