Propositions: Ontology and Logic

This book is a defense of an ontology of propositions and of some logical resources for representing them. It begins with an austere formulation of a theory of propositions in a first-order extensional logic, but then uses the commitments of this theory to justify an enrichment to modal logic—the logic of necessity and possibility—as an appropriate framework for regimented languages that are constructed to represent any of our scientific and philosophical commitments. Both the proof theory and the model theory of a first-order quantified modal logic are developed in detail, and it is argued that these formal resources help to sharpen questions about ontology and predication. The clarification of predication helps to provide a motivation for extending our ontological commitment to properties and relations that are expressed by predicates, and for extending the logic to a higher-order modal logic that provides a conception of metaphysical modality that allows for the contingent existence, not only of persons and physical objects but also of properties, relations, and propositions. Even though both the specific ontological commitments defended (to propositions, properties, and relations) and the logical resources that are used to defend them (modal and higher-order logic) were famously rejected by W. V. Quine, the book adopts a self-consciously neo-Quinean methodology and argues that the theory that is developed helps to motivate and clarify Quine’s naturalistic metaphysical picture.