|Rules of inference|
|Rules of replacement|
Negation introduction states that if a given antecedent implies both the consequent and its complement, then the antecedent is a contradiction.
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.
- Category:Propositional Calculus on ProofWiki (GFDLed)