The Implicative Conditional

This paper investigates the implicative conditional, a connective intended to describe the logical behavior of an empirically defined class of natural language conditionals, also named implicative conditionals, which excludes concessive and some other conditionals. The implicative conditional strengthens the strict conditional with the possibility of the antecedent and of the contradictory of the consequent. p double right arrow q is thus defined as notsign (sic) lozenge (p <^> (sic)q) <^> (sic) p <^> lozenge (sic)q. We explore the logical properties of this conditional in a reflexive normal Kripke semantics, provide an axiomatic system and prove it to be sound and complete for our semantics. The implicative conditional validates transitivity and contraposition, which we take to be integral parts of reasoning and communication. But it only validates restricted versions of strengthening the antecedent, right weakening, simplification, and rational monotonicity. Apparent counterexamples to some of these properties are explained as due to contextual factors. Finally, the implicative conditional avoids the paradoxes of material and strict implication, and validates some connexive principles such as Aristotle's theses and weak Boethius' thesis, as well as some highly entrenched principles of conditionals, such as conjunction of consequents, disjunction of antecedents, modus ponens, cautious monotonicity and cut.

Automated summary

This paper investigates the logical behavior of implicative conditionals in natural language. The implicative conditional strengthens the strict conditional while allowing for the possibility of the antecedent and contradictory of the consequent. The paper explores the logical properties of this conditional in a reflexive normal Kripke semantics and provides an axiomatic system that proves to be sound and complete.