H. Richard Niebuhr may have influenced more different kinds of students of religion than any other religious thinker in the twentieth century. Sociologists of religion, church historians, social and theological ethicists, theologians, and ministers all look to the works of Niebuhr for insights that enrich their own understanding of religion. Other sages may have been more dominant in any given discipline, but few have so influenced so many over such a wide range of issues. The breadth and richness of his insights allow Niebuhr to appeal to people from a variety of theological perspectives. Yet, above all, Niebuhr was a churchly person who spent his life struggling to determine and to express the church’s proper relationship to the world. That struggle is the focus of this book.