2. Individual political communities may indeed enjoy a high degree of culture and civilization. They may have a large and industrious population, an advanced economic structure, great natural resources and extensive territories. Yet, even so, in isolation from the rest of the world they are quite incapable of finding an adequate solution to their major problems. The nations, therefore, must work with each other for their mutual development and perfection. They can help themselves only in so far as they succeed in helping one another. That is why international understanding and co operation are so necessary. (Papal Encyclical, Mater et Magistra, 15 May 1961).
3. If a nation were to succumb more or less deliberately to the temptation to close in upon itself and failed to meet the responsibilities following from its superior position in the community of nations, it would fall seriously short of its clear ethical duty. When the West gives the impression of abandoning itself to forms of growing and selfish isolation, and the East in its turn seems to ignore for questionable reasons its duty to cooperate in the task of alleviating human misery, then we are up against not only a betrayal of humanity's legitimate expectations, betrayal that is a harbinger of unforeseeable consequences, but also a real desertion of a moral obligation. (Papal Encyclical, Sollicitudo Rei Socialis, 30 December 1987).