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reductio ad absurdum

 
Dictionary: re·duc·ti·o ad ab·sur·dum   (rĭ-dŭk'tē-ō ăd əb-sûr'dəm, -zûr'-, -shē-ō) pronunciation
 
n., pl. -o·nes ad absurdum ('nēz, -nās).

Disproof of a proposition by showing that it leads to absurd or untenable conclusions.

[Medieval Latin reductiō ad absurdum : Latin reductiō, a bringing back, reduction + Latin ad, to + Latin absurdum, absurdity, from neuter of absurdus, absurd.]


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Philosophy Dictionary: reductio ad absurdum
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(Latin, reduction to absurdity) The process of reasoning that derives a contradiction from some set of assumptions, and concludes that the set as a whole is untenable, so that at least one of them is to be rejected. Formally, if {A1…An} ⊦ (B & ¬B), then {A1…An-1} ⊦ ¬An.

 
Law Encyclopedia: Reductio Ad Absurdum
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This entry contains information applicable to United States law only.

[Latin, Reduction to absurdity.] In logic, a method employed to disprove an argument by illustrating how it leads to an absurd consequence.

 
Wikipedia: Reductio ad absurdum
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Reductio ad absurdum (Latin: "reduction to the absurd") is a form of argument in which a proposition is disproven by following its implications to a logical but absurd consequence.

An example of a reductio ad absurdum would be to note the consequences of an ad coelum theory of property would be that a land owner would have ownership over other planets.

Example

Attempts at making a reductio ad absurdum argument can easily create a straw man fallacy if it distorts the proposition which one is trying to disprove. The example above can very easily lead to a straw man fallacy in that it states that:

  • a person cannot own land because no one person has the right to own a planet if other people require the land.

The fallacy, thus, lies in the difference between the ability to own land and the right to own land, which are not equivalent.

See also


 
Best of the Web: reductio ad absurdum
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Some good "reductio ad absurdum" pages on the web:


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mathworld.wolfram.com
 
 
 
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indirect proof (philosophy)
indirect proof (mathematics)
absurd (philosophy)

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Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
Philosophy Dictionary. The Oxford Dictionary of Philosophy. Copyright © 1994, 1996, 2005 by Oxford University Press. All rights reserved.  Read more
Law Encyclopedia. West's Encyclopedia of American Law. Copyright © 1998 by The Gale Group, Inc. All rights reserved.  Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Reductio ad absurdum" Read more