Need to Know: Questions and the Paradox of Epistemic Obligation

Åqvist’s paradox of epistemic obligation can be solved, if we use knowledge-wh instead of knowledge-that in specifications of the ‘need to know’: the knowledge which an agent in a certain organisational role is required to have. Knowledge-wh is knowledge of an answer to a question, which depends on the context. We show how knowledge-wh can be formalised in a logic of questions, which is combined with standard deontic logic to represent epistemic obligations. We demonstrate that under the new interpretation, the paradox can no longer be derived. The resulting logic is useful for representation of access control policies.