In news stories and political commentary, we hear daily about measures of public opinion. But why, exactly, does public opinion matter? How is it shaped, and to what extent does it influence public policy? These questions are explored in the Fall 2012 issue of Dædalus. Guest-edited by Lee Epstein, professor of law and political science at the University of Southern California, the volume features eight essays by political scientists, legal scholars, and public policy experts.