The problem of metaphysical omniscience

Modal accounts of knowledge, mind, and language, as prominently defended by Lewis, leave no room for enquiry into non-contingent matters. According to Lewis, there is only one necessarily true proposition, and it is vacuously known by everyone. What, then, are we doing when we do metaphysics, which often seems to deal with non-contingent questions? Lewis never gave a satisfactory answer, or even acknowledged the problem. I explore some options. Can we understand the relevant parts of metaphysics as dealing with contingent questions about our concepts? Can we understand them in terms of a hyperintensional conception of “explicit” knowledge? Both options have some promise. Ultimately, however, I don’t think they succeed at squaring Lewis’s empiricist epistemology with his metaphysical realism.