This wide-ranging study focuses upon the controversies surrounding the meaning and significance of Social Darwinism. It clarifies the nature of Social Darwinism and its relationship to the ideas of Darwin, Lamarck and Herbert Spencer. After examining the development of Social Darwinist theories by a number of European and American thinkers, Mike Hawkins explores the use of these theories in a number of ideological debates and movements of the period 1860–1945. These include socio-political reform, national and racial conflict, eugenics, the position of women and Nazism/Fascism. The aim is to illuminate, through detailed comparative analyses, both the flexibility and the limits of Social Darwinism - limits which derive from the view of nature which lies at the very heart of Social Darwinism. The study concludes with a discussion of modern sociobiology in order to assess the continuing vitality of Social Darwinism.