This book gathers together thirteen of Peter van Inwagen's essays on metaphysics, several of which have acquired the status of modern classics in their field. They range widely across such topics as Quine's philosophy of quantification, the ontology of fiction, the part-whole relation, the theory of 'temporal parts', and human knowledge of modal truths. In addition, van Inwagen considers the question as to whether the psychological continuity theory of personal identity is compatible with materialism, and defends the thesis that possible states of affairs are abstract objects, in opposition to David Lewis's 'extreme modal realism'. A specially-written introduction completes the collection, which will be an invaluable resource for anyone interested in metaphysics.