# Negation introduction

Transformation rules |
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Propositional calculus |

Rules of inference |

Rules of replacement |

Predicate logic |

**Negation introduction** is a rule of inference, or transformation rule, in the field of propositional calculus.

Negation introduction states that if a given antecedent implies both the consequent and its complement, then the antecedent is a contradiction.^{[1]} ^{[2]}

## Formal notation

This can be written as:

An example of its use would be an attempt to prove two contradictory statements from a single fact. For example, if a person were to state "When the phone rings I get happy" and then later state "When the phone rings I get annoyed", the logical inference which is made from this contradictory information is that the person is making a false statement about the phone ringing.

## External links

- Category:Propositional Calculus on ProofWiki (GFDLed)

## References

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