The first of two forms of ontological uncertainty arising in previous chapters is examined in detail. This first form stems from situations in which our best scientific theorizing or modeling with respect to one and the same target system or phenomenon in the world generates what appear to be mutually inconsistent descriptions. A recent, popular response to the challenge this represents—for anyone hoping for a coherent conception of scientific ontology—is to invoke a form of “perspectivism” regarding these descriptions. However, while certain forms of pluralism may be apt in such cases, perspectivism is not one of them. It is argued that perspectival accounts of ontology are subject to a fatal trilemma. Two forms of non-perspectival pluralism are described, supporting the introduction of a novel, contrastive theory of ontological explanation.