This essential core text introduces readers to metaphysics. In thoughtful and engaging prose, Peter van Inwagen examines three profound questions: What are the most general features of the world? Why is there a world? And, what is the place of human beings in the world? The third edition includes an entirely new chapter on ontology. The new chapter presents a theory of the nature of being and proceeds to apply this theory to two problems of ontology: the problem of non-existent objects and the problem of universals. Equally valuable as a textbook in a university course or an introduction to metaphysical thinking for the interested layperson, Metaphysics remains a fascinating book for a wide range of readers, from first-time students to the most sophisticated philosophers.