This book is about beliefs in the existence of God in two senses. It is about beliefs in God in the sense of their objects, the propositions believed. And it is about beliefs in God in the sense of states of minds. Classical arguments and evidence for and against propositions affirming God's existence are studied, as well as Pascalian practical arguments for and against cultivating states of belief in God.

Questions of truth, and of belief, concerning God's existence come after questions regarding what would be God's nature. Discussions of arguments in this book are predicated on several conceptions often combined, and sometimes moderated, of what God would be like. Chapter I, “ ‘GOD’ and ‘god’, and God,” goes into these conceptions. Its business is to establish the broad perspective from which issues concerning God's existence, and what would be This One's nature, are taken.

Then come chapters about theoretical arguments for beliefs in God. Chapters II through IV are about demonstrative arguments that would establish God's existence without the aid of contingent assumptions or premises – the classical ontological arguments of René Descartes, St. Anselm, and Baruch Spinoza (Chapter II); the modal ontological argument of Charles Hartshorne and Alvin Plantinga (Chapter III); and Kurt Göodel's ontological proof (Chapter IV). Chapters V and VI examine connected ordinary deductive arguments that make use of contingent premises: Thomas Aquinas' argument for a first cause, an argument of David Hume's character Demea, Samuel Clarke, and especially Gottfried Leibniz for ultimate reasons.