 are often referred to as principles of negative introspection. Negative introspection is quite controversial as it poses very high demands on knowledge and belief. The schema 5 may be seen as a closed world assumption (Hendricks 2005): The agent has complete overview of all the possible worlds and own information. If \(\neg\psi\) is considered possible (\(\widehat{K}_{a}\neg\psi\), i.e., \(\neg K_{a}\psi\)), then the agent knows it is considered possible (\(K_{a}\neg K_{a}\psi\)). Such a closed world assumption is natural when constructing hyper-rational agents in, e.g., computer science or game theory, where the agents are assumed to reason as hard as logically possible about their own information when making decisions.