The doubt-whether puzzle

The English predicate doubt is known to exhibit a distinctive selec-tional restriction: it is compatible with declarative as well as whether-complements but is incompatible with constituent wh-complements. The interpretation of a whether-complement under doubt is also puzzling, as ⌜doubt whether p⌝ is almost—but not completely—synonymous with ⌜doubt that p⌝. I will argue that these behaviors of doubt can be given a semantic account, by making use of the mechanisms of HIGHLIGHTING and EXHAUS-TIFICATION. Doubt expresses an existential doxastic attitude toward the negation of the highlighted content of the complement while having pre-suppositions that are sensitive to the ordinary content of the complement. Given that ⌜that p⌝ and ⌜whether p⌝ are equivalent in the highlighted con-tent but non-equivalent in the ordinary content, the semantics explains fine-grained differences in interpretations between ⌜doubt whether p⌝ and ⌜doubt that p⌝. Furthermore, given the lack of a stronger scalemate, the interpretation of ⌜doubt that/whether p⌝ undergoes strengthening due to exhaustification, akin to the behavior of ‘scaleless’ modals reported in the literature.