This volume collects the most important articles on the _ metaphysics of modality by noted philosopher Alvin _ Plantinga. The book chronicles Plantinga's thought from the late 1960's to the present. Platinga is here concerned with fundamental issues in mataphysics: what is the nature of _ abstract objects like possible worlds, properties, _ propositions, and such phenomena? Are there possible but _ non-actual objects? Can objects that do not exist exemplify properties? In this thorough and searching book, Plantinga addresses these and many other questions that continue to_ preoccupy philosophers in the field. This volume contains_ some of the best work in metaphysics from the past 30 years, and will remain a source of critical contention and keen interest among philosophers of metaphysics and philosophical logic for years to come.