18. Taking up an idea expressed by Pope John XXIII at the opening of the Council,31 the Decree on Ecumenism mentions the way of formulating doctrine as one of the elements of a continuing reform.³² 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",³³ 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.

19. Even so, doctrine needs to be presented in a way that makes it understandable to those for whom God himself intends it. In my Encyclical Epistle Slavorum Apostoli, I recalled that this was the very reason why Saints Cyril and Methodius laboured to translate the ideas of the Bible and the concepts of Greek theology in the context of very different historical experiences and ways of thinking. They wanted the one word of God to be "made accessible in each civilization's own forms of expression".34 They recognized that they could not therefore "impose on the peoples assigned to their preaching either the undeniable superiority of the Greek language and Byzantine culture, or the customs and way of life of the more advanced society in which they had grown up".³⁵ Thus they put into practice that "perfect communion in love which preserves the Church from all forms of particularism, ethnic exclusivism or racial prejudice, and from any nationalistic arrogance".³⁶ In the same spirit, I did not hesitate to say to the Aboriginal Peoples of Australia: "You do not have to be divided into two parts ... Jesus calls you to accept his words and his values into your own culture".³⁷ Because by its nature the content of faith is meant for all humanity, it must be translated into all cultures. Indeed, the element which determines communion in truth is the meaning of truth. The expression of truth can take different forms. The renewal of these forms of expression becomes necessary for the sake of transmitting to the people of today the Gospel message in its unchanging meaning.³⁸

"This renewal therefore has notable ecumenical significance".³⁹ And not only renewal in which the faith is expressed, but also of the very life of faith. It might therefore be asked: who is responsible for doing this? To this question the Council replies clearly: "Concern for restoring unity pertains to the whole Church, faithful and clergy alike. It extends to everyone, according to the ability of each, whether it be exercised in daily Christian living or in theological and historical studies".⁴⁰

20. All this is extremely important and of fundamental significance for ecumenical activity. Thus it is absolutely clear that ecumenism, the movement promoting Christian unity, is not just some sort of "appendix" which is added to the Church's traditional activity. Rather, ecumenism is an organic part of her life and work, and consequently must pervade all that she is and does; it must be like the fruit borne by a healthy and flourishing tree which grows to its full stature.

This is what Pope John XIII believed about the unity of the Church and how he saw full Christian unity. With regard to other Christians, to the great Christian family, he observed: "What unites us is much greater than what divides us". The Second Vatican Council for its part exhorts "all Christ's faithful to remember that the more purely they strive to live according to the Gospel, the more they are fostering and even practising Christian unity. For they can achieve depth and ease in strengthening mutual brotherhood to the degree that they enjoy profound communion with the Father, the Word, and the Holy Spirit".41