The Western concept of the separation of church and state-indeed, the idea of the modern state itself-grew out of a centuries long struggle between the kings and popes of medieval Europe. Few controversies have so indelibly influenced the course of Western civilization, both past and present. The Crisis of Church State brings to the contemporary reader the major documents of the prolonged debate, revealing the ideas behind the conflict and relating them to the practical politics of medieval world. Among the items recorded here are Henry IV's defiance of the papacy over the issue of lay investiture, the rise of the papacy to political power under lawyer-pope Innocent III and Philip IV's humiliation of Boniface VIII.