25 Man's social nature makes it evident that the progress of the human person and the advance of society itself hinge on one another. For the beginning, the subject and the goal of all social institutions is and must be the human person which for its part and by its very nature stands completely in need of social life. Since this social life is not something added on to man, through his dealings with others, through reciprocal duties, and through fraternal dialogue he develops all his gifts and is able to rise to his destiny. Among those social ties which man needs for his development some, like the family and political community, relate with greater immediacy to his innermost nature; others originate rather from his free decision. In our era, for various reasons, reciprocal ties and mutual dependencies increase day by day and give rise to a variety of associations and organizations, both public and private. This development, which is called socialization, while certainly not without its dangers, brings with it many advantages with respect to consolidating and increasing the qualities of the human person, and safeguarding his rights. But if by this social life the human person is greatly aided in responding to his destiny, even in its religious dimensions, it cannot be denied that men are often diverted from doing good and spurred toward and by the social circumstances in which they live and are immersed from their birth. To be sure the disturbances which so frequently occur in the social order result in part from the natural tensions of economic, political and social forms. But at a deeper level they flow from man's pride and selfishness, which contaminate even the social sphere. When the structure of affairs is flawed by the consequences of sin, man, already born with a bent toward evil, finds there new inducements to sin, which cannot be overcome without strenuous efforts and the assistance of grace.
Source: Gaudium et Spes (Vatican.va)