This book is a centenary tribute to the distinguished French Dominican theologian Cardinal Yves Congar (1940-95). In the words of Cardinal 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 contribution. In the context of interdisciplinary scholarship, the volume reflects on Congar's contribution to theology, ecumenism, history of ecclesiology, pneumatology and interreligious dialogue. The contributors, experts in the fields of theology, ecumenism, philosophy and history from nine countries, are in many respects representative of Congar's intellectual and ecumenical interests. An important objective of the work is to facilitate a renewed engagement with the Second Vatican Council. If the volume contributes to making the documents of Vatican II more accessible to the modern person and, therefore, more widely read and applied, it will have rendered fitting tribute to Cardinal Congar.