A Semantic Account of Free Choice for Ability ‘can’ in STIT Logic
Summary
The free choice effect appears in natural language when an interaction between a disjunction and a modal gives rise to a quasi-conjunctive interpretation. Problematic is that free choice inferences are not valid in classical modal logic. Free choice inferences are typically studied for the deontic modal ‘may’, but have also been observed for other modals, including ability ‘can’. STIT logic is a framework that can model agency, but it does not account for free choice inferences for ability modals. Fusco (2020) offers a semantic account for free choice ability with possible world semantics. In this thesis, I incorporate elements from from her account into STIT logic in order to create a modified version of STIT logic in which free choice inferences are valid for ability ‘can’. These elements include a two-dimensional account of disjunction that is sensitive to the ‘actual world’, and a view of ability as the historical possibility to externally realize something. This resulted in a STIT logic in which disjunctions are treated non-classically when in the scope of modal operators, allowing for free choice ability inferences.