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Contradiction (logic)

A logical conflict: a statement that is necessarily false.

Note: This should not be confused with a contraposition.

Example for a contradictive statement:

: It is raining and it is not raining.

Since it cannot rain and not rain at the same time, the statement as a whole is necessary false.

Description

A contradiction is a statement that is necessary false under all circumstances. Usually it is the result of putting two contradictory statements together, as in the example above.

No contradictions are statements that only evaluate as false due to experience or additional information. For example, take the following statement:

It is raining.

If looking out of the window proves that it is actually not raining at the moment, then the statement is false, but it is not a contradiction, because we need additional information to know if it is true or false.

Significance

Contradictory statements can not be used as premises for logical conclusions. Even if they appear in the concluding sentence, they only signify that something must have gone wrong at some point – which can of course be used to prove the invalidity of a statement.

Opposite

The opposite of a contradiction, i.e. a statement that is always (necessary) true, is called a tautology.

Symbols

On this site, the logical symbol is used to indicate a contradiction. Since every contradiction is always inherently false, it can also be replaced or described by the expression “false” or “F” or the equivalent expression in the respective formal system (e.g. 0).

See also

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About this site

Ad Hominem Info is a project to explain and categorize the most common systematic fallacies and fallacies. On this page, you will find a background article that briefly explains an important logical concept, which may be needed to better understand another article in this area.
For more information, please see the main category “logic

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