Book excerpt: The papacy is clearly the greatest difficulty facing ecumenical dialogue today, and particularly the dialogue between Catholicism and Orthodoxy. Yet there is a doorway of hope. In his encyclical, Ut unum sint, John Paul II expressed a desire for common reflection on the exercise of papal primacy. In You Are Peter the great Orthodox theologian Olivier Clement brilliantly responds to this request. He emphasizes the history and experience of the undivided Church, before recalling the contrasting developments of eastern and western Christianity and concluding with the tasks that call us to unity. Professor Clements response to John Paul II [is] solidly rooted in the Orthodox tradition, [and] represents the cordial and open mentality characteristic of the theologians of Saint Sergius. I would judge that it is almost exactly the kind of response for which Pope John Paul II was hoping. It is a pleasure to be able to present to English-speaking readers this concise, learned, and articulate presentation.... Professor Clements contribution ... is a sign of the progress [in ecumenism] thus far made and a beacon of hope for the future. From the Foreword by Avery Cardinal Dulles, S.J. Laurence J. McGinley Professor Fordham University, New York