This book is a historical overview of the search for unity between the churches of East and West over the past millennium. The author pays attention to the theological, canonical and socio-historical aspects of this search, in particular, interfaith relations in Eastern Europe and the Balkans. This study introduces the reader to the historical and theological context of modern ecumenical dialogue and inter-church relations. Ernst Suttner - Doctor of Theology, Professor of Pathology and Oriental Theology at the University of Vienna, specialist in the history and theology of the Eastern Church, member of the International Mixed Theological Commission.