In his famous Wager, Blaise Pascal (1623–62) offers the reader an argument that it is rational to strive to believe in God. Philosophical debates about this classic argument have continued until our own times. This volume provides a comprehensive examination of Pascal's Wager, including its theological framework, its place in the history of philosophy, and its importance to contemporary decision theory. The volume starts with a valuable primer on infinity and decision theory for students and non-specialists. A sequence of chapters then examines topics including the Wager's underlying theology, its influence on later philosophical figures, and contemporary analyses of the Wager including Alan Hájek's challenge to its validity, the many gods objection, and the ethics of belief. The final five chapters explore various ways in which the Wager has inspired contemporary decision theory, including questions related to infinite utility, imprecise probabilities, and infinitesimals.