On relative ignorance

I discuss relative ignorance of an agent with respect to the knowledge or ignorance of other agents. It turns out, not surprisingly, that even the two-agent case is quite complex and generates a rich variety of naturally arising non-equivalent operators of relative ignorance. In this paper I explore these in a more systematic way and put together several simple, though technically laborious, observations about their inter-relations. For the technical proofs of these I employ the software tool MOLTAP, which implements, inter alia, tableaux for the underlying multi-agent epistemic logic. “Against logic there is no armor like ignorance” (Laurence J. Peter)