Science, David Deutsch argues, is about explanation. A series of extraordinary scientific discoveries has given us extremely deep explanations of the structure of reality, but most scientists have not taken them seriously enough. In this brilliant investigation, Oxford quantum physicist David Deutsch does take them seriously. The result is a startlingly integrated, rational and optimistic world view that combines four strands: quantum physics and the theories of knowledge, computation and evolution. Exploring these in turn, he lucidly demonstrates the profound and diverse connections that have been discovered between these four apparently independent subjects, revealing a fabric of reality that is objective and comprehensible, and in which human actions and ideas play essential roles.