My focus here will be Rudolf Carnap’s views on ontology, as these are presented in the seminal “Empiricism, Semantics and Ontology” (1950). I will first describe how I think Carnap’s distinction between external and internal questions is best understood. Then I will turn to broader issues regarding Carnap’s views on ontology. With certain reservations, I will ascribe to Carnap an ontological pluralist position roughly similar to the positions of Eli Hirsch and the later Hilary Putnam. Then I turn to some interrelated arguments against the pluralist view. The arguments are not demonstrative. Some possible escape routes for the pluralist are outlined. But I think the arguments constitute a formidable challenge. There should be serious doubt as to whether the pluralist view, as it emerges after discussion of these arguments, will be worth defending. Moreover, there is an alternative ontological view which equally well subserves the motivations underlying ontological pluralism.