# Principle of explosion

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 Revision as of 15:43, 7 October 2014Jahsonic (Talk | contribs)← Previous diff Revision as of 15:44, 7 October 2014Jahsonic (Talk | contribs) Next diff → Line 1: Line 1: {{Template}} {{Template}} + The '''principle of explosion''' ([[Latin]]: ''ex falso quodlibet'', "from a falsehood, anything follows", or ''ex contradictione sequitur quodlibet'', "from a contradiction, anything follows"), or the '''principle of Pseudo-Scotus''', is the law of [[classical logic]], [[intuitionistic logic]] and similar logical systems, according to which any statement can be proven from a contradiction. That is, once a contradiction has been asserted, any proposition (or its negation) can be inferred from it. + + As a demonstration of the principle, consider two contradictory statements - “All lemons are yellow” and "Not all lemons are yellow", and suppose (for the sake of argument) that both are simultaneously true. If that is the case, anything can be proven, e.g. "Santa Claus exists", by using the following argument: + # We know that "All lemons are yellow" as it is defined to be true. + # Therefore the statement that (“All lemons are yellow" OR "Santa Claus exists”) must also be true, since the first part is true. + # However, if "Not all lemons are yellow" (and this is also defined to be true), Santa Claus must exist - otherwise statement 2 would be false. It has thus been "proven" that Santa Claus exists. The same could be applied to any assertion, including the statement "Santa Claus does not exist". + + ==See also== + * [[Consequentia mirabilis]] - Clavius's Law + * [[Dialetheism]] – belief in the existence of true contradictions + * [[Law of excluded middle]] – every proposition is either true or not true + * [[Law of noncontradiction]] – no proposition can be both true and not true + * [[Paraconsistent logic]] – a family of logics used to address contradictions + * [[Paradox of entailment]] – a seeming paradox derived from the principle of explosion + * [[Reductio ad absurdum]] – concluding that a proposition is false because it produces a contradiction + * [[Trivialism]] – the belief that all statements of the form "P and not-P" are true {{GFDL}} {{GFDL}}

## Revision as of 15:44, 7 October 2014

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The principle of explosion (Latin: ex falso quodlibet, "from a falsehood, anything follows", or ex contradictione sequitur quodlibet, "from a contradiction, anything follows"), or the principle of Pseudo-Scotus, is the law of classical logic, intuitionistic logic and similar logical systems, according to which any statement can be proven from a contradiction. That is, once a contradiction has been asserted, any proposition (or its negation) can be inferred from it.

As a demonstration of the principle, consider two contradictory statements - “All lemons are yellow” and "Not all lemons are yellow", and suppose (for the sake of argument) that both are simultaneously true. If that is the case, anything can be proven, e.g. "Santa Claus exists", by using the following argument:

1. We know that "All lemons are yellow" as it is defined to be true.
2. Therefore the statement that (“All lemons are yellow" OR "Santa Claus exists”) must also be true, since the first part is true.
3. However, if "Not all lemons are yellow" (and this is also defined to be true), Santa Claus must exist - otherwise statement 2 would be false. It has thus been "proven" that Santa Claus exists. The same could be applied to any assertion, including the statement "Santa Claus does not exist".