eolas/Logic/Negation_Elimination.md

tags
Logic propositional-logic derivation-rules

Like the introduction rule for negation, the elimination rule also works by deriving a contradiction. It is basically Negation Introduction in reverse. Instead of starting the subproof with a true proposition from which you derive a contradiction, you start with the negation of a proposition, derive a contradiction and then assert the positive of the negated proposition you started out with.