The previous volume of this trilogy left off by summarizing momentous changes that, cumulatively, had transformed American society from its premodern state to modernity by the second decade of the twentieth century. As employed in that volume and this one, the term modernity means the presence of a world characterized by maturing industrial capitalism, a political culture featuring increased participatory democracy, the weakening of a hierarchical, class-based social order predicated on relatively fixed status distinctions, and the emergence of secular theories of knowledge and “scientific” methods of intellectual inquiry as competitors to theories and methods based on religious beliefs. By the close of the 1920s, all of those features of American life were in place....