This book is a study of ontological arguments for the existence of God. These arguments are supposed to have premises that are knowable a priori. On one simple version of an ontological argument, God is by definition a being that has every perfection, and since existence is a perfection, God exists. There are a number of more sophisticated ontological arguments, which have been defended and attacked by the most famous philosophers.
All significant versions of the argument from medieval, modern and contemporary philosophers are presented and evaluated here. The first chapter presents a history of the argument, and subsequent chapters digest and explain different versions of the arguments. Various objections against ontological arguments are considered, with an extensive treatment of parodies of the arguments and the most influential objection from Kant.
Oppy argues that some of the most influential objections against the arguments fail, but develops and defends other objections in original ways. He concludes that all ontological arguments are unpersuasive and of no use in supporting theism.
This is likely the most comprehensive and detailed study of ontological arguments available. It is generally clear and well organized, and often original and insightful. Extensive bibliographical and literature notes are provided, and this makes the book particularly useful for those interested in studying the arguments further. The book should be of interest to advanced undergraduate and graduate students and philosophers working in the philosophy of religion. Those unfamiliar with contemporary analytic philosophy will find it extremely difficult.
Readers may also be interested in Foster's "The Divine Lawmaker" and Gellman's "Experience of God and the Rationality of Theistic Belief" for more promising arguments for the existence of God.