Title: Underspecificity in Modal Contexts
Description: This dissertation is on the semantics of modal expressions and attitude verbs like English ‘must,’ ‘may,’ ‘ought,’ and ‘want’ — expressions that allow us to discuss socially important modal facts like obligations, permissions, and desires. When discussing them, we rarely spell out the modal facts with complete specificity. For example, I may say, ‘I want ice cream,’ without specifying that what I desire, in particular, is unmelted, non-toxic, chocolate ice cream. If, in response, someone were to give me melted, toxic, vanilla ice cream, it would be fair for me to reply that what I have been given is not what I wanted. Similarly, I can truly say ‘you must wash the dishes,’ or ‘you may have some wine,’ without specifying that there are exceptions, that is, specific ways of washing the dishes, or of having wine, that are not ways of doing what you must or are allowed. I call modal claims that have such exceptions underspecific. Since avoiding underspecificity may require explicitly ruling out an infinite number of exceptions, most of our ordinary modal claims are underspecific.

Our reliance on them is thus crucial to our very capacity to communicate about the modal facts. I argue that modal claims can be true and underspecific by virtue of the meanings of the modal expressions that figure in them, and I defend a general semantic framework for modals that explains how. In the simplest cases, my framework predicts that speakers may describe the contents of desires, permissions, and obligations using conditions that are merely necessary for their fulfillment. Since getting unmelted, non-toxic chocolate ice cream necessitates getting ice cream simpliciter, this explains how I may truly state ‘I want ice cream’ even if the content of my desire is more specific. Generalizing this account, however, poses significant challenges. Indeed, many philosophers and linguists have rejected semantic theories of modals that allow for true, underspecific modal claims for two main reasons. One is that previous accounts give rise to several well-known logical puzzles, including the puzzle of free choice permission, Ross’s puzzle, and the Samaritan paradox.

A second reason is that existing accounts generate the wrong truth value judgments in examples involving complex preferences and forms of uncertainty. In response, theorists have offered semantics for modals like ‘ought’ and ‘want’ that rely on the theory of rational choice and the notion of expected utility. Straightforward expected utility analyses succeed in generating the desired truth value judgments, but at the cost of giving up the possibility of underspecifying the modal facts in the ways that we manifestly do. I argue that we can meet both of these challenges, while still allowing for true, underspecific modal claims. In order to do so, I develop new solutions to the puzzle of free choice permission, Ross’s Puzzle, and the Samaritan paradox that improve on the empirical predictions of existing solutions. My framework also generates a methodologically desirable degree of independence between the proper semantics of modal expressions, on the one hand, and the proper analyses of desire or obligation in terms of rational choice, on the other.

As a result, the semantic framework I develop in this dissertation can succeed where theorists who have turned to decision-theoretic semantics for ‘want’ and ‘ought’ have thought that existing theories fail. Besides the advantages that my semantic framework gains with respect to these problems in particular, it more generally provides new insights into the rich linguistic capacities and conventions that speakers leverage in order to communicate about the modal facts.