This book is a celebration of the life and work of the distinguished French theologian Yves Congar (1904-95). In the words of Avery Dulles: "No theologian of the twentieth century is more deserving of a commemorative volume than Yves Congar." The primary aim of the present work is to examine Congar's role as theologian of the Church and assess the significance of his immense contribution. The volume reflects on Congar's contribution to theology, ecumenism, the history of ecclesiology, twentieth-century church history, pneumatology, and interreligious dialogue. The contributors, experts in the fields of theology, ecumenism, philosophy and history, are in many respects representative of Congar's intellectual and ecumenical interests. An important objective of the work is to facilitate continued engagement with the Second Vatican Council and to contribute to a new reception of its key teachings. If the volume helps to make the documents of the council more accessible and, therefore, more widely read and applied, it will have rendered fitting tribute to Congar.