From Pope Benedict XVI’s encyclical Caritas in Veritate (2009):
Another important consideration is the common good. To love someone is to desire that person’s good and to take effective steps to secure it. Besides the good of the individual, there is a good that is linked to living in society: the common good. It is the good of “all of us”, made up of individuals, families and intermediate groups who together constitute society.4 It is a good that is sought not for its own sake, but for the people who belong to the social community and who can only really and effectively pursue their good within it. To desire the common good and strive towards it is a requirement of justice and charity. To take a stand for the common good is on the one hand to be solicitous for, and on the other hand to avail oneself of, that complex of institutions that give structure to the life of society, juridically, civilly, politically and culturally, making it the pólis, or “city”. The more we strive to secure a common good corresponding to the real needs of our neighbours, the more effectively we love them. Every Christian is called to practise this charity, in a manner corresponding to his vocation and according to the degree of influence he wields in the pólis. This is the institutional path — we might also call it the political path — of charity, no less excellent and effective than the kind of charity which encounters the neighbour directly, outside the institutional mediation of the pólis. When animated by charity, commitment to the common good has greater worth than a merely secular and political stand would have. Like all commitment to justice, it has a place within the testimony of divine charity that paves the way for eternity through temporal action. Man’s earthly activity, when inspired and sustained by charity, contributes to the building of the universal city of God, which is the goal of the history of the human family. In an increasingly globalized society, the common good and the effort to obtain it cannot fail to assume the dimensions of the whole human family, that is to say, the community of peoples and nations,5 in such a way as to shape the earthly city in unity and peace, rendering it to some degree an anticipation and a prefiguration of the undivided city of God.
4 Cf. Second Vatican Ecumenical Council, Pastoral Constitution on the Church in the Modern World Gaudium et Spes, 26.
5 Cf. John XXIII, Encyclical Letter Pacem in Terris (11 April 1963): Acta Apostolicæ Sedis 55 (1963), 268-270.
— Caritas in Veritate 7