Appointed by John XXIII to the Pontifical Secretariat for the Promotion of the Unity of Christians, and then to the Vatican Council as theologian (peritus), George Tavard directly contributed to the writing of the Decree on Ecumenism and afterward served in major ecumenical dialogues, both in the U.S. and internationally. Born from this ecumenical experience and theological reflection and influenced by theology in France, where Henri de Lubac was one of his professors and he was personally acquainted with Jean Danielou and Yves Congar, the author will guide the reader through the problems,...