18 Taking up an idea expressed by Pope John XXIII at the opening of the Council, the Decree on Ecumenism mentions the way of formulating doctrine as one of the elements of a continuing reform. Here it is not a question of altering the deposit of faith, changing the meaning of dogmas, eliminating essential words from them, accommodating truth to the preferences of a particular age, or suppressing certain articles of the Creed under the false pretext that they are no longer understood today. The unity willed by God can be attained only by the adherence of all to the content of revealed faith in its entirety. In matters of faith, compromise is in contradiction with God who is Truth. In the Body of Christ, "the way, and the truth, and the life" ( Jn 14:6), who could consider legitimate a reconciliation brought about at the expense of the truth? The Council's Declaration on Religious Freedom Dignitatis Humanae attributes to human dignity the quest for truth, "especially in what concerns God and his Church", and adherence to truth's demands. A "being together" which betrayed the truth would thus be opposed both to the nature of God who offers his communion and to the need for truth found in the depths of every human heart.
Source: Ut Unum Sint (Vatican.va)