The author argues that man differs from all other animals in his ability for social teaching and learning and that this provides him with a second method of evolutionary advance, in addition to biology. He advances this through the idea that man has the capacity to entertain ethical ideas, which is an essential and necessary feature of this new mode of evolution. From here he draws the conclusion that a consideration of the broad trends of evolution provides a framework within which we can rationally discuss the relative merits of the various systems of ethical belief current in the world. In presenting his argument, Waddington draws on research in biology, psychology, the social sciences, and philosophy. He concludes with a short consideration of some of the most important ethical problems facing mankind at the time of the book’s publication.