Contemporary science presents us with the remarkable theory that the universe began to exist about fifteen billion years ago with a cataclysmic explosion called "the Big Bang." The question of whether Big Bang cosmology supports theism or atheism has long been a matter of discussion among the general public and in popular science books, but has received scant attention from philosophers. This book sets out to fill this gap by means of a sustained debate between two philosophers, William Lane Craig and Quentin Smith, who defend opposing positions. Craig argues that the Big Bang that began the universe was created by God, while Smith argues that the Big Bang has no cause. Alternating chapters by the two philosophers criticize and attempt to refute preceding arguments. Their arguments are based on Einstein's theory of relativity and include a discussion of the new quantum cosmology recently developed by Stephen Hawking and popularized in A Brief History of Time.