Causality, Aspect, and Modality in Actuality Inferences
Bhatt (1999) observes a surprising interpretation for ability-oriented uses of the possibility modal in languages like French, which overtly indicate the contrast between an "internal" and "external" view of a reported events with aspectual marking. Under the internal view (imperfective aspect), the French modal pouvoir is compatible with a "pure" (unrealized) ability interpretation. By contrast, on the external view (perfective aspect), pouvoir produces an actuality entailment, forcing the inference that the modal complement was realized.
- Rebecca pouvait traverser le lac à la nage, mais elle ne l'a jamais traversé.
(Rebecca could-imperfective swim across the lake, but she never crossed it.) - Rebecca a pu traverser le lac à la nage, #mais elle ne l'a pas traversé.
(Rebecca could-perfective swim across the lake, #but she did not cross it.)
Actuality entailments have resisted explanation in a literature which aims to derive from the composition of modality and aspect. I propose an account which derives these inferences from a novel component in the semantics of ability: causal dependence. I argue that ability modals represent a type of hypothetical guarantee (Belnap 1991, Mandelkern et al 2017), attributing to an agent the possibility of taking some action which is presupposed to be causally sufficient for the realization of the modal complement.
I develop the analysis by examining two other types of complement-entailing constructions: implicative verbs (manage; Karttunen 1971) and enough and too constructions (be fast enough to win the race; Meier 2003, Hacquard 2005). I show that the complement inferences follow from causal dependencies in the lexical semantics and composition of these constructions, and demonstrate that this causal structure interacts with viewpoint aspect to produce inferential contrasts that parallel those in (1)-(2). On this approach, actuality entailments result from the composition of the "external" viewpoint of perfective aspect and the proposed causal structure of ability modals.
The success of a causal dependence analysis in explaining these inferences lends support to the broader program of the dissertation, which argues that the types of contrasting dependencies that can be defined over a formal causal model (e.g., Pearl 2000) play an important role in the semantic representations and linguistic reasoning associated with both overtly and non-transparently causal language.
University oral exam committee: Cleo Condoravdi (chairs), Itamar Francez, Daniel Lassiter, Beth Levin
University oral exam chair: Tobias Gerstenberg