Equivalence, Pragmatics, and the Assertability of Conditionals- A Defense of Jackson’s Equivalence Thesis through Gricean Implicature

George Gao

The Equivalence Thesis holds that indicative conditionals (If P, then Q) share the same truth conditions as material conditionals (P  Q), thereby preserving semantic content across surface form. One argument that the unassertability of indicative conditionals due to a lack of causality and logic challenges the thesis’ applicability to conversation.

This paper advances a defense of the Equivalence Thesis grounded in Gricean pragmatics. First, the paper preserves the truth-conditional parity of this thesis by treating the semantic core as identical to the material conditional, thereby maintaining a rigorous standard for semantic content. Second, it accounts for the apparent unassertability through Gricean implicature, distinguishing between truth conditions and assertability, as articulated in the Logic and Conversation framework. The core claim is that pragmatic enrichment need not threaten semantic equality; rather, it explains why indicative conditionals often feel more informative, evidentially loaded, or contextually significant than their bare truth-conditional form would suggest.

Methodologically, the paper integrates Jackson’s original defense with a precise Gricean account of implicature, clarifying when such implicatures are cancellable and context-sensitive. It offers a formal scaffolding in which the semantic layer (truth conditions) remains stable across If P, then Q and P → Q, while the pragmatic layer (assertability) varies with discourse context and semantic norms. The resulting two-layer framework yields a principled reconciliation: semantic parity satisfied by the material conditional, and pragmatic enrichment licensed by Gricean reasoning, thereby preserving both the doctrinal integrity of Jackson’s thesis and the nuanced, often forceful readings characteristic of ordinary discourse. The analysis informs foundational discussions in both the philosophy of logic and the philosophy of language.