The French Dominican theologian Yves Congar is recognized by many as the most important Roman Catholic ecclesiologist of the 20th century. He was the impetus behind some of the major decrees of the Second Vatican council, and a leader in the ecumenical movement in Europe throughout most of the century. Despite his importance, very little has been written about Congar in English. In this book, Groppe argues that Congar significantly advanced contemporary pneumatology through his elaboration of a theology of the Holy Spirit that is at once a theology of the church and a theological anthropology. Congar's pneumatology, argues Groppe, can enrich various ongoing theological discussions, including reflection as to whether the church should be hierarchy or a democracy, the development of "persons in communion" as a framework for contemporary theological anthropology and ecclersiology, and deliberations about the personhood of the Holy Spirit.