On Quantitative and Qualitative Parsimony

The distinction between quantitative and qualitative parsimony is supposed to allow David Lewis to dismiss one of the charges against his modal realism: that is, the charge of bloated ontology. The aim of this paper is to undermine Lewis's response to this objection. In order to do this, a distinction between multipliable and nonmultipliable objects is introduced. Based on this it is argued that the acceptance of Lewis's response requires one to believe in modal realism in the first place—that is, one has to believe in the view that the existence of nonactual spatiotemporal worlds does not affect the quality of the ontological commitment. Although the paper focuses on the problem of the metaphysics of possible worlds, this should be regarded merely as a case study. Accordingly, the results of this analysis should find applications in other metaphysical debates as well.