In this chapter, I offer a reading of the central nodes of Alain Badiou's mathematical ontology of multiplicity, highlighting those elements which I take to be most significant for the secularising naturalist, and paving the way for my attempt to link Badiou's philosophy — his mathematical ontology (here) and his "generic" conception of truth (Chapter 5) — with contemporary trends in analytic philosophy of science. It is my contention that Badiou's metaphilosophical insights, properly reinterpreted and recast in the service of naturalism, can be of use for a fully secularised metaphysical worldview. In the course of this reading I will encounter an obstacle offered by Badiou's philosophy, that of the unsettled relationship between the ontological and the ontic, empirical realms.