Knowing whether a proposition is true means knowing that it is true or knowing that it is false. In this paper, we study logics with a modal operator Kw for knowing whether but without a modal operator K for knowing that. This logic is not a normal modal logic, because we do not have Kw(φ → ψ) → (Kwφ → Kwψ). Knowing whether logic cannot define many common frame properties, and its expressive po...

This paper offers an account of the fact that certain verbs license wh-questions as their complement but not whether-questions. For instance, it is felicitous to say It is surprising who Bill had invited but not to say It is surprising whether Bill had invited his wife. We refer to this contrast as the *whether puzzle. We propose an account which crucially rests on the assumption that the relev...