The logic of conditional negation

Abstract

It is argued that the "inner" negation ∼ familiar from 3-valued logic can be interpreted as a form of "conditional" negation: ∼ A is read 'A is false if it has a truth value'. It is argued that this reading squares well with a particular 3-valued interpretation of a conditional that in the literature has been seen as a serious candidate for capturing the truth conditions of the natural language indicative conditional (e.g., "If Jim went to the party he had a good time"). It is shown that the logic induced by the semantics shares many familiar properties with classical negation, but is orthogonal to both intuitionistic and classical negation: it differs from both in validating the inference from A → ∼B to ∼(A → B). © 2008 by University of Notre Dame.