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. The book consists of alternating chapters by Craig and Smith, with each chapter being either a criticism of a preceding chapter or being criticized by a subsequent chapter. Part One consists of Craig's arguments that the past is necessarily finite and that God created the Big Bang, and Smith's criticisms of these arguments. Part Two presents Smith's arguments that Big Bang cosmology is inconsistent with theism and Craig's criticisms of Smith's argument. The authors' arguments are based on Einstein's theory of relativity, and there is also a discussion of Stephen Hawking's new quantum cosmology.