The document from the Second Vatican Council that deals most extensively with the Church's social doctrines is Gaudium et Spes, the Church in the Modern World.  "The modern world," it states, "shows itself at once powerful and weak, capable of the noblest deeds or the foulest; before it lies the path to freedom or to slavery, to progress or retreat, to brotherhood or hatred" (9).  How choose the right path forward?  By keeping one great truth always in view, a truth which might be called the theme of the document: "All things on earth should be related to man as their center and crown" (12).  This truth is expressed another way by the title of the opening chapter of the document: "The Dignity of the Human Person."  Vatican II was convened shortly after the horrors of Nazi Germany, with the horrors of Soviet Russia still present, and an increasingly secular consumerist culture growing in the West.  All of these put human dignity at grave risk.  The social doctrines of the Church are directed to this goal: to preserve human dignity by insisting on the proper social, political, cultural, and economic frameworks for all of humanity within which we can become fully and truly human.  This is often spoken of as concern for the "common good."
After laying out the general principles involved in protecting human dignity, Gaudium et Spes goes on to deal with what it calls "problems of special urgency."  Among them are economic conditions, political oppression, war and the community of nations, and questions of enculturation.  But the first problem tackled is this one: "Fostering the nobility of marriage and the family."  The family, says the document, is "a kind of school of deeper humanity" (52).  If individuals are to achieve fulfillment, and if the good of the whole society is to be

preserved, family life must be strengthened.  It is the place in which "the various generations come together and help one another grow wiser and harmonize personal rights with the other requirements of social life." As such the family is "the foundation of society."  The stronger and more healthy the family, the more both individual and social life will be preserved, and human dignity protected.
Sociological data have overwhelmingly supported this fundamental doctrine.  With all of its difficulties, the traditional family continues to be the place where people do best, and this is especially true of children.  Where are the rates of child poverty lowest?  In two-parent families.  Where are rates of sexual and physical abuse, drug and alcohol abuse, gang involvement among children lowest?  In two-parent families.  Where are rates of educational and economic success and psychological health highest?  In children of two-parent families.  For this reason, the Church is always trying to find ways to support and strengthen such families, even as she tries to aid those families that have been wounded or broken.
The Church understands that the family is not a merely human arrangement, but rather a God-given relationship which corresponds to the depths of our human nature.  We are not free simply to do away with it, or to redefine it, without seriously harming ourselves and others.  This is why the Church demands of governments and of civil society, as a matter of social justice, that marriage and family life should be acknowledged, protected, and promoted by the government and society as the basis of a truly humane society.  If the family is weakened, other human rights eventually go by the wayside, and human dignity is put in peril.