  One of the highlights of recent informal epistemology is its growing
theoretical emphasis upon various notions of context. The present paper
addresses the connections between knowledge and context within a formal
approach. To this end, a "contextual epistemic logic", CEL, is proposed, which
consists of an extension of standard S5 epistemic modal logic with appropriate
reduction axioms to deal with an extra contextual operator. We describe the
axiomatics and supply both a Kripkean and a dialogical semantics for CEL. An
illustration of how it may fruitfully be applied to informal epistemological
matters is provided.
