These are some of the questions which John Maynard Smith attempts to answer in this book. In terms comprehensible to the reader with no previous knowledge of the subject, he describes the fundamental problems faced by modern biology, and provides a non-technical account of the recent advances in molecular genetics. Starting from the definition of life and the mechanisms of replication and heredity, he considers a wide range of topics—the pattern of nature, animal behaviour, the brain’s function, and, finally, the origin of life—concentrating on those problems, particularly in evolution, development, and cognition, to which biologists have as yet found no complete solution.