Essays on Existence and Essence presents a series of writings--including several previously unpublished--by Bob Hale on the topics of ontology and modality. The essays develop and consolidate a number of themes central to his work and to contemporary metaphysics, logic, and philosophy of language. They display Hale''s innovative approach to some of the most fundamental issues in philosophy, in dialogue (and, in some cases, in collaboration) with other leading philosophers. The notion of a definition is examined as it applies both to words--verbal definitions-and to things--real definitions--and the relations between these are brought out in order to address problems in the metaphysics of necessity and the semantics and epistemology of modality. Hale argues for an essentialist theory of the source of necessity and our knowledge of it, and provides rigorous and inventive responses to problems such a theory might face. This theoretical framework is applied to the recently influential truthmaking approach to semantics and logic, developing an exact truthmaker account of universal quantification and modal statements. Other topics covered include the Fregean theory of ontological categories, the status of second-order logic, the metaphysics of numbers, and the nature of analytic propositions. The volume opens with a substantial introduction by Kit Fine, providing a critical examination of Hale''s philosophy, and closes with a complete bibliography of Hale''s writings.