Trading Ontology for Ideology (and Vice Versa)

In this paper, I defend modal dimensionalism against the objection that it is ontologically and ideologically heavy. First, I briefly outline the theory and the objection against it. The objection relies on the widely accepted view that ontological and ideological parsimony are operational criteria when comparing metaphysical theories. Second, I outline the conventional distinction between ontology and ideology in the metaphysical tradition. Third, I challenge a particular kind of parsimony: reduction by identification. Fourth, even if reduction by identification is accepted, I show that theories that pursue this often minimize differences, and that such minimization paves the way to epistemic underdetermination. Finally, I demonstrate that some theories in modal metaphysics also suffer from difference minimization and should thus not be measured on the ontology/ideology scale (contra the objection from heaviness).