We introduce a new operator on information structures which we call `knowing whether' as opposed to the standard knowledge operator which may be called `knowing that'. The di erence between these operators is simple. Saying that an agent knows that a certain event occurred implies that this event indeed occurred, while saying that the agent knows whether an event occurred does not imply that th...

In his seminal work [Plaza, 1989], Plaza proposed the public announcement logic (PAL), which is considered as the pilot logic in the field of dynamic epistemic logic. In the same paper, Plaza also introduced an interesting “know-value” operator Kv and listed a few valid formulas of PAL+Kv. However, it is unknown that whether these formulas, on top of the axioms for PAL, completely axiomatize PA...

Abstract In Knowing and Seeing , Michael Ayers presents a view of what he calls primary knowledge according to which one who knows in that way both perspicuously how they know. Here, I use some general considerations about seeing, knowing, knowing order raise questions this view. More specifically, consider putative limits on one’s capacity know knows. The main question pursue concerns whether ...