Revisiting McGee's counterexample to Modus Ponens

MARIELA RUBIN; LO GUERCIO, NICOLÁS FRANCISCO

Seminario; Work in Progress Seminar (WIP); 2023

Buenos Aires Logic Group - IIF(SADAF)

In this work, we explain away McGee’s famous counterexample to Modus Ponens through pragmatics. We argue that in the examples provided by McGee (1985) two different phenomena are involved in our dispositions to accept the premises and yet reject the conclusion. Neither of them is a semantic phenomenon. Arguably, neither of them is specific to indicative conditionals. In particular, we will show that the use of the indefinite determiner phrase “a republican” that appears in both premises of McGee’s most famous example is ambiguous. There is an ambiguity between a specific and a non-specific reading of the article. Neither version of the argument, once disambiguated, looks like a counterexample to Modus Ponens. Finally, we argue that there is a second and more general phenomenon that concerns the three examples. Namely, an ignoranceimplicature triggered by the conditional. Yet, even if the conditional is the one to blame for the presuppositions of ignorance, this phenomenon is shared by many terms, in particular by some truth-functional connectives.