Analytic philosophy has recently demonstrated a revived interest in metaphysical problems about possibility and necessity. Graeme Forbes here provides a careful description of the logical background of recent work in this area for those who may be unfamiliar with it, moving on to discuss the

distinction between modality de re and modality de dicto and the ontological commitments of possible worlds semantics. In addition, Forbes offers a unified theory of the essential properties of sets, organisms, artefacts, substances, and events, based on the doctrine that identity facts must be

intrinsically grounded, and analyzes and rejects apparent counterexamples to this doctrine.