  Epistemic modal logic normally views an epistemic situation as a Kripke
model. We consider a more basic approach: to view an epistemic situation as a
set W of possible states/worlds -- maximal consistent sets of propositions --
with conventional accessibility relations determined by W. We find that in many
epistemic situations, W is not a Kripke model: a necessary and sufficient
condition for W to be a Kripke model is the so-called `fully explanatory
property' - a propositional form of common knowledge of the model - which has
been a hidden (and overlooked) assumption in epistemic modal logic. We sketch a
theory that describes epistemic models in their generality. We argue for
conceptual and practical value of new models, specifically for representing
partial knowledge, asymmetric knowledge, and awareness.
