Difference between revisions of "Circular reasoning"

@@ Line 1: / Line 1: @@
-[[Circular reasoning]] is a form of [[Logical fallacy#Proof by assertion|proof by assertion]] in which one assumes the fact that one is trying to prove, and then "proves" the fact by a chain of inferences that lead back to the original assertion. This is also known as ''petitio principii'' or ''begging the question.''
-== An analysis ==
-The simplest argument is a single inference, as per the Law of Detachment:
-*If P, then Q.
-*P.
-*Therefore, Q.
-The Law of the Syllogism uses Detachment to establish an ''intermediate'' conclusion between the original premise and the eventual conclusion. Thus:
-*If P, then Q.
-*If Q, then R.
-*Therefore, if P, then R.
-*P.
-*Therefore, Q and R.
-''Contraposition'' uses Detachment in reverse to show that a thing is ''not'' true:
-*If P, then Q.
-*Not Q.
-*Therefore, not P.
-All these proofs start with a proposition already verified or denied.
-This is the classic structure of circular reasoning, that is an abuse of the Law of the Syllogism:
-*If P, then Q.
-*If Q, then R.
-*If R, then P.
-*P.
-*Therefore, Q.
-*Therefore, R.
-*Therefore, P.
-Each of these three conditional statements would be valid by itself. Together, they create a flawed argument, because P now depends on itself to be true. The line of reasoning ends where it began, and is thus a circle. The only difference between this and ''proof by assertion'' is that the latter attempts to use a single conditional statement--"if P, then P"--while circular reasoning uses at least two, and typically three or more, syllogisms.
-Circular arguments can be very difficult to detect. Circular arguments found in the professional literature, or in [[propaganda]], typically use five or six (or more) syllogisms.
-Every logical system ''must'' begin with a set of generally accepted assumptions called ''postulates'' or ''axioms'' (from the [[Greek]] '''αξιος''' or ''axios'' worthy or deserving). Similarly, any set of definitions must start with a set of fundamental terms that need no definition. An axiom is usually a fundamental property of nature upon which all agree. Persons attempting to show that something is a fundamental property of nature when it is not, or a value of that property that is contrary to fact, typically use circular reasoning to make such an attempt.
-== Reference ==
-<table style="border:1px solid #AAAAAA; background: #EDF1F1; float:right; width:100px; margin-left:15px;">
-<tr><td>{{fallacy|circular reasoning}}
-<tr><td>Use the <nowiki>{{fallacy|circular reasoning}}</nowiki> template to insert this warning on a page containing an example of ''[[circular reasoning]]''. The warning label will then link back to this page.
-</table>
-* [http://creationwiki.org/Circular_reasoning Circular reasoning] by [[CreationWiki]]
-[[Category:Logical fallacy]]

Difference between revisions of "Circular reasoning"

Revision as of 17:36, August 30, 2007

Navigation menu

Search