42 It happens for example that, in the spirit of the Sermon on the Mount, Christians of one confession no longer consider other Christians as enemies or strangers but see them as brothers and sisters. Again, the very expression separated brethren tends to be replaced today by expressions which more readily evoke the deep communion — linked to the baptismal character — which the Spirit fosters in spite of historical and canonical divisions. Today we speak of "other Christians", "others who have received Baptism", and "Christians of other Communities". The Directory for the Application of Principles and Norms on Ecumenism refers to the Communities to which these Christians belong as "Churches and Ecclesial Communities that are not in full communion with the Catholic Church". This broadening of vocabulary is indicative of a significant change in attitudes. There is an increased awareness that we all belong to Christ. I have personally been able many times to observe this during the ecumenical celebrations which are an important part of my Apostolic Visits to various parts of the world, and also in the meetings and ecumenical celebrations which have taken place in Rome. The "universal brotherhood" of Christians has become a firm ecumenical conviction. Consigning to oblivion the excommunications of the past, Communities which were once rivals are now in many cases helping one another: places of worship are sometimes lent out; scholarships are offered for the training of ministers in the Communities most lacking in resources; approaches are made to civil authorities on behalf of other Christians who are unjustly persecuted; and the slander to which certain groups are subjected is shown to be unfounded. In a word, Christians have been converted to a fraternal charity which embraces all Christ's disciples. If it happens that, as a result of violent political disturbances, a certain aggressiveness or a spirit of vengeance appears, the leaders of the parties in question generally work to make the "New Law" of the spirit of charity prevail. Unfortunately, this spirit has not been able to transform every situation where brutal conflict rages. In such circumstances those committed to ecumenism are often required to make choices which are truly heroic. It needs be reaffirmed in this regard that acknowledging our brotherhood is not the consequence of a large-hearted philanthropy or a vague family spirit. It is rooted in recognition of the oneness of Baptism and the subsequent duty to glorify God in his work. The Directory for the Application of Principles and Norms on Ecumenism expresses the hope that Baptisms will be mutually and officially recognized. This is something much more than an act of ecumenical courtesy; it constitutes a basic ecclesiological statement. It is fitting to recall that the fundamental role of Baptism in building up the Church has been clearly brought out thanks also to multilateral dialogues.
Source: Ut Unum Sint (Vatican.va)