In epistemology and in philosophy of language there is fierce debate about the role of context in knowledge, understanding, and meaning. Many contemporary epistemologists take seriously the thesis that epistemic vocabulary is context-sensitive. This thesis is of course a semantic claim, so it has brought epistemologists into contact with work on context in semantics by philosophers of language. This volume brings together the debates, in a set of twelve specially written essays representing the latest work by leading figures in the two fields. All future work on contextualism will start here.