The epistemic modals possible, probable, likely, and certain require a semantics which explains their behavior both as modal operators and as gradable adjectives. An analysis of these items in terms of Kennedy & McNally's (2005) theory of gradability suggests that they are associated with a single, fully closed scale of possibility. An implementation using the standard theory of modality due to Kratzer is shown to make incorrect predictions in several domains. However, identifying the scale of possibility with standard numerical probability explains the facts about gradability and avoids the undesirable predictions of Kratzer's theory.Keywords: gradability, comparison, epistemic modals, probability
Gradable modalsMost discussion of the semantics of English modals has focused on the meanings of modal auxiliaries such as must, should, and can, illustrated in (1).(1) a. Harry should be in Sacramento by now.b. My brother can bench press 250 pounds.c. All cameras must be checked at the door.However, English also has a substantial number of adjectival modals such as likely, obligatory, able, and evident. These items are readily gradable, just like the large and well-studied class of gradable adjectives. Some examples are given in (2a)-(2d). * Special thanks to Chris Barker and Seth Yalcin, both of whom have been enormously helpful and inspiring regarding this project. Thanks also to Anna Szabolcsi, Philippe Schlenker, Chris Kennedy, Larry Horn, Angelika Kratzer, Paul Portner, Pauline Jacobson, Julien Dutant, Chris Collins, Bob Frank, Tom Leu, Eytan Zweig, Tricia Irwin, Salvador Mascarenhas, Tim Leffel, Simon Charlow, and Mike Solomon for inspiration, discussion, copies of unpublished work, data, ideas, and/or help. My initial exposure to the idea of thinking about modality and gradability together came in Seth Yalcin's philosophy of language seminar at NYU in 2008, where he floated the idea that possible and probable were instances of minimum-and relative-standard adjectives in K&M's theory and that probability provided the relevant scale. Though most of our subsequent work was done independently, we have reached similar conclusions, as can be seen by comparing the present paper to the forthcoming Yalcin 2010b.