Gaudium et Spes 42 covers some old ground from earlier in this document, beginning with the notion that Church unity contributes to the unity of human society as a whole. To the extent that the Church is a part of society, this is true, on a sociological level:
The union of the human family is greatly fortified and fulfilled by the unity, founded on Christ,(Dogmatic Constitution on the Church, Chapter II, n. 9: AAS 57 (1965), pp. 12-14) of the family of God’s (children).
Aside from the mission of religion, the Church has no “proper mission” in mainstream human society. This would likely have been an astounding statement in a day when monarchy or other human institutions were raised to a higher level in philosophy.
Christ, to be sure, gave His Church no proper mission in the political, economic or social order. The purpose which He set before her is a religious one.(Cf. Pius XII, Address to the International Union of Institutes of Archeology, History and History of Art, March 9, 1956: AAS 48 (1965), p. 212: “Its divine Founder, Jesus Christ, has not given it any mandate or fixed any end of the cultural order. The goal which Christ assigns to it is strictly religious. . . The Church must lead (people) to God, in order that they may be given over to him without reserve…. The Church can never lose sight of the strictly religious, supernatural goal. The meaning of all its activities, down to the last canon of its Code, can only cooperate directly or indirectly in this goal.”) But out of this religious mission itself come a function, a light and an energy which can serve to structure and consolidate the human community according to the divine law. As a matter of fact, when circumstances of time and place produce the need, she can and indeed should initiate activities on behalf of all … , especially those designed for the needy, such as the works of mercy and similar undertakings.
The second half of this statement is important. The Church does have something to say about aspects of human society which impact on morality and justice. GS claims the needy as a special interest of the Church.
The Church lauds non-religious elements that move congruently to religious aims. The Church is also intended to be a sign, an example for those aspiring to a deeper unity among human beings. This example is intended to be a stronger and more practical example than political domination. Sadly, mishandling of child sex abuse has severely clouded this aspect. I think the world is left with admiration for the more saintly individual examples of Christianity: Mother Teresa, John Paul II, among others. The Church itself as an institution has a more difficult path on the way of credibility.
The Church recognizes that worthy elements are found in today’s social movements, especially an evolution toward unity, a process of wholesome socialization and of association in civic and economic realms. The promotion of unity belongs to the innermost nature of the Church, for she is, “thanks to her relationship with Christ, a sacramental sign and an instrument of intimate union with God, and of the unity of the whole human race.”(Dogmatic Constitution on the Church, Chapter I, n. 1: AAS 57 (1965), p. 5) Thus she shows the world that an authentic union, social and external, results from a union of minds and hearts, namely from that faith and charity by which her own unity is unbreakably rooted in the Holy Spirit. For the force which the Church can inject into the modern society of (humankind) consists in that faith and charity put into vital practice, not in any external dominion exercised by merely human means.
This next paragraph raises an important issue, but again, the Church’s witness here is dulled because we have yet to achieve any kind of practical peace within our numbers. Even the universality of the Church, which might be seen as a factor transcending particular political, economic, or social systems, is often seen as a detriment to the Church’s role in providing an example of and the wisdom for a practical human unity. The witness of charity and justice, when strong, might serve to overcome this:
Moreover, since in virtue of her mission and nature she is bound to no particular form of human culture, nor to any political, economic or social system, the Church by her very universality can be a very close bond between diverse human communities and nations, provided these trust her and truly acknowledge her right to true freedom in fulfilling her mission. For this reason, the Church admonishes her own (children), but also humanity as a whole, to overcome all strife between nations and race in this family spirit of God’s children, an in the same way, to give internal strength to human associations which are just.
This following paragraph could be seen to express a sort of core value for the whole document. The Church is deeply concerned about human welfare. The Church praises elements outside of itself which promote the aims of justice, charity, and peace. The Church is willing to participate with human institutions outside of itself to develop the common good of human society.
With great respect, therefore, this council regards all the true, good and just elements inherent in the very wide variety of institutions which the human race has established for itself and constantly continues to establish. The council affirms, moreover, that the Church is willing to assist and promote all these institutions to the extent that such a service depends on her and can be associated with her mission. She has no fiercer desire than that in pursuit of the welfare of all she may be able to develop herself freely under any kind of government which grants recognition to the basic rights of person and family, to the demands of the common good and to the free exercise of her own mission.