A History of the Desire for Christian Unity is a multi-volume reference work on the history of ecumenism. The ecumenical movement is understood as a twentieth-century movement of European origin with a global reach. This reference work is a reconstruction of the arc of time in which the Christian churches transitioned from a position of hostility to one of dialogue, and from separation to forms of communion. Scholars across the continents and disciplines explore a history of individuals and groups, generations and assemblies, documents and programs, theologies and practices, all firmly placed within the framework of a desire for unity. This first volume traces the long-term roots and reconstructs the historical, theological, and political junctures that marked the beginning of a distinctive movement that runs throughout the nineteenth and into the heart of the twentieth century.