Monism and pluralism are competing views about how unified the cosmos is. According to monism, the existence of many beings is at most a derivative fact, deriving from the existence and nature of a single fundamental being; and perhaps it is not a fact at all, but an illusion. According to pluralism, on the other hand, at the very least there are many fundamental beings; and perhaps the cosmos is so disjointed that the many fundamental beings bear no substantive relation to one another.  The two positions have widely divergent implications for other philosophical questions, and the divide between monism and pluralism is perhaps one of the deepest and most significant metaphysical divides. (William James once called it "the most central of all philosophic problems, central because so pregnant.") Presumably this partly explains the recurrence of the monism/pluralism debate at various points in the history of philosophy. And while the birth of analytic philosophy led to an almost total neglect of the issue for most of the twentieth century, the past few years have witnessed a resurgence of interest. In this course we will explore the debate through both historical works and contemporary readings.  Among other things we will investigate whether the “moderate” versions of monism and pluralism are coherent and whether it's possible to rationally believe the "radical" versions.