Anybody who is not shocked by quantum theory has not understood it. Niels Bohr's dictum bears witness to the bewildering impact of quantum theory, flying in the face of classical physics and dramatically transforming scientists' outlook on our relationship with the material world. While the theory has been supremely successful in its explanation of some of the major problems in twentieth-century physics, its meaning (presenting a number of basic philosophical contradictions) is nevertheless the subject of unprecedented controversy amongst scientists. In this book, which has its origin in a series of radio broadcasts, Paul Davies interviews eight physicists involved in debating and testing the theory, with radically different views of its significance.