100 In my recent Letter to the Bishops, clergy and faithful of the Catholic Church indicating the path to be followed towards the celebration of the Great Jubilee of the Holy Year 2000 , I wrote that "the best preparation for the new millennium can only be expressed in a renewed commitment to apply, as faithfully as possible, the teachings of Vatican II to the life of every individual and of the whole Church ". The Second Vatican Council is the great beginning—the Advent as it were—of the journey leading us to the threshold of the Third Millennium. Given the importance which the Council attributed to the work of rebuilding Christian unity, and in this our age of grace for ecumenism, I thought it necessary to reaffirm the fundamental convictions which the Council impressed upon the consciousness of the Catholic Church, recalling them in the light of the progress subsequently made towards the full communion of all the baptized. There is no doubt that the Holy Spirit is active in this endeavour and that he is leading the Church to the full realization of the Father's plan, in conformity with the will of Christ. This will was expressed with heartfelt urgency in the prayer which, according to the Fourth Gospel, he uttered at the moment when he entered upon the saving mystery of his Passover. Just as he did then, today too Christ calls everyone to renew their commitment to work for full and visible communion.
Source: Ut Unum Sint (Vatican.va)