Book excerpt: The debate over scientists' social responsibility is a topic of great controversy today. Peter J. Kuznick here traces the origin of that debate to the 1930s and places it in a context that forces a reevaluation of the relationship between science and politics in twentieth-century America. Kuznick reveals how an influential segment of the American scientific community during the Depression era underwent a profound transformation in its social values and political beliefs, replacing a once-pervasive conservatism and antipathy to political involvement with a new ethic of social reform.