Free choice disjunction as a rational speech act

Abstract

The so-called free choice inference (from You may take an apple or a pear to You may take an apple) is mysterious because it does not follow from ordinary modal logic. We show that this inference arises in the Rational Speech Act framework (Frank & Goodman 2012). Our basic idea is inspired by exhaustification-based models of free choice (Fox 2007) and by game-theoretic accounts based on iterated best response (Franke 2011). We assume that when the speaker utters You may take an apple or a pear, the hearer reasons about why the speaker did not choose alternative utterances such as You may take an apple. A crucial ingredient in our explanation is the idea of semantic uncertainty (Bergen, Levy & Goodman 2016). Specifically, we assume that the speaker is uncertain whether or not the hearer will interpret You may take an apple as forbidding them from taking a pear. This uncertainty can be thought of as resulting from Fox’s (2007) optional covert exhaustification. Uttering the disjunction is a way for the speaker to prevent the hearer from concluding that any fruit is forbidden to take. Knowing this, the hearer concludes that they may choose either fruit.