43. It happens more and more often that the leaders of Christian Communities join together in taking a stand in the name of Christ on important problems concerning man's calling and on freedom, justice, peace, and the future of the world. In this way they "communicate" in one of the tasks which constitutes the mission of Christians: that of reminding society of God's will in a realistic manner, warning the authorities and their fellow-citizens against taking steps which would lead to the trampling of human rights. It is clear, as experience shows, that in some circumstances the united voice of Christians has more impact than any one isolated voice.

Nor are the leaders of Communities the only ones joined in the work for unity. Many Christians from all Communities, by reason of their faith, are jointly involved in bold projects aimed at changing the world by inculcating respect for the rights and needs of everyone, especially the poor, the lowly and the defenceless. In my Encyclical Letter Sollicitudo Rei Socialis, I was pleased to note this cooperation, stressing that the Catholic Church cannot fail to take part in these efforts.72 In effect, Christians who once acted independently are now engaged together in the service of this cause, so that God's mercy may triumph.

This way of thinking and acting is already that of the Gospel. Hence, reaffirming what I wrote in my first Encyclical Letter Redemptor Hominis, I have had occasion "to insist on this point and to encourage every effort made in this direction, at all levels where we meet our other brother Christians".⁷³ I have thanked God "for what he has already accomplished in the other Churches and Ecclesial Communities and through them", as well as through the Catholic Church.⁷⁴ Today I see with satisfaction that the already vast network of ecumenical cooperation is constantly growing. Thanks also to the influence of the World Council of Churches, much is being accomplished in this field.