A book which has many levels, Mayr's magnificent tour-de-force can be read as a `life-history' of the discipline - from its roots in the work of Aristotle, through its dormancy through the Scientific Revolution and its flowering in the hands of Darwin, to the spectacular growth with the advent of molecular techniques. It also has a evangelical element: biology until recently has been the neglected stepchild of science, and many educated people have little grasp of how biology explains the natural world. Yet to address the major political and moral questions that face us today, we must acquire an understanding of their biological roots. Mayr's persuasiveness will go far to remedy this situation and will help to redirect how people think about the natural world. As he argues, the physical sciences cannot address many aspects of nature that are unique to life. Living organisms must be understood at every level of organization; they cannot be reduced to the laws of physics and chemistry.