17 With regard to other Christians, the principal documents of the Commission on Faith and Order and the statements of numerous bilateral dialogues have already provided Christian Communities with useful tools for discerning what is necessary to the ecumenical movement and to the conversion which it must inspire. These studies are important from two points of view: they demonstrate the remarkable progress already made, and they are a source of hope inasmuch as they represent a sure foundation for further study. The increase of fellowship in a reform which is continuous and carried out in the light of the Apostolic Tradition is certainly, in the present circumstances of Christians, one of the distinctive and most important aspects of ecumenism. Moreover, it is an essential guarantee for its future. The faithful of the Catholic Church cannot forget that the ecumenical thrust of the Second Vatican Council is one consequence of all that the Church at that time committed herself to doing in order to re-examine herself in the light of the Gospel and the great Tradition. My Predecessor, Pope John XXIII, understood this clearly: in calling the Council, he refused to separate renewal from ecumenical openness. At the conclusion of the Council, Pope Paul VI solemnly sealed the Council's commitment to ecumenism, renewing the dialogue of charity with the Churches in communion with the Patriarch of Constantinople, and joining the Patriarch in the concrete and profoundly significant gesture which "condemned to oblivion" and "removed from memory and from the midst of the Church" the excommunications of the past. It is worth recalling that the establishment of a special body for ecumenical matters coincided with the launching of preparations for the Second Vatican Council and that through this body the opinions and judgments of the other Christian Communities played a part in the great debates about Revelation, the Church, the nature of ecumenism and religious freedom.
Source: Ut Unum Sint (Vatican.va)