Pragmatic reasoning through semantic inference

A number of recent proposals have used techniques from game theory and Bayesian cognitive science to formalize Gricean pragmatic reasoning (Franke 2009, Frank & Goodman 2012, Goodman & Stuhmuller 2013, Jager 2012). We discuss two phenomena which pose a challenge to these accounts of pragmatics: M-implicatures (Horn 1984) and embedded implicatures which violate Hurford's constraint (Hurford 1974, Chierchia et al. 2012). While techniques have been developed for deriving M-implicatures, Hurford-violating embedded implicatures pose a more fundamental challenge, because of basic limitations in the models' architecture. In order to explain these phenomena, we propose a realignment of the division between semantic content and pragmatic content. Under this proposal, the semantic content of an utterance is not fixed independent of pragmatic inference; rather, pragmatic inference partially determines an utterance's semantic content. We show how semantic inference can be realized as an extension to the Rational Speech Acts framework (Goodman & Stuhmuller 2013). The addition of lexical uncertainty derives both M-implicatures and the relevant embedded implicatures, and preserves the derivations of more standard implicatures. We use this principle to explain a novel class of implicature, non-convex disjunctive implicatures, which have several theoretically interesting properties. In particular, these implicatures can be preserved in downward-entailing contexts in the absence of accenting, a property which is predicted by lexical uncertainty, but which violates prior generalizations in the literature (Horn 1989, Fox & Spector Forthcoming).