Gaudium et Spes §40

⁴⁰ Everything we have said about the dignity of the human person, and about the human community and the profound meaning of human activity, lays the foundation for the relationship between the Church and the world, and provides the basis for dialogue between them. In this chapter, presupposing everything which has already been said by this council concerning the mystery of the Church, we must now consider this same Church inasmuch as she exists in the world, living and acting with it. Coming forth from the eternal Father's love, founded in time by Christ the Redeemer and made one in the Holy Spirit, the Church has a saving and an eschatological purpose which can be fully attained only in the future world. But she is already present in this world, and is composed of men, that is, of members of the earthly city who have a call to form the family of God's children during the present history of the human race, and to keep increasing it until the Lord returns. United on behalf of heavenly values and enriched by them, this family has been "constituted and structured as a society in this world" by Christ, and is equipped "by appropriate means for visible and social union." Thus the Church, at once "a visible association and a spiritual community," goes forward together with humanity and experiences the same earthly lot which the world does. She serves as a leaven and as a kind of soul for human society as it is to be renewed in Christ and transformed into God's family. That the earthly and the heavenly city penetrate each other is a fact accessible to faith alone; it remains a mystery of human history, which sin will keep in great disarray until the splendor of God's sons, is fully revealed. Pursuing the saving purpose which is proper to her, the Church does not only communicate divine life to men but in some way casts the reflected light of that life over the entire earth, most of all by its healing and elevating impact on the dignity of the person, by the way in which it strengthens the seams of human society and imbues the everyday activity of men with a deeper meaning and importance. Thus through her individual matters and her whole community, the Church believes she can contribute greatly toward making the family of man and its history more human. In addition, the Catholic Church gladly holds in high esteem the things which other Christian Churches and ecclesial communities have done or are doing cooperatively by way of achieving the same goal. At the same time, she is convinced that she can be abundantly and variously helped by the world in the matter of preparing the ground for the Gospel. This help she gains from the talents and industry of individuals and from human society as a whole. The council now sets forth certain general principles for the proper fostering of this mutual exchange and assistance in concerns which are in some way common to the world and the Church.