157 Probably the most difficult problem today concerns the relationship between political communities that are economically advanced and those in the process of development. Whereas the standard of living is high in the former, the latter are subject to extreme poverty. The solidarity which binds all men together as members of a common family makes it impossible for wealthy nations to look with indifference upon the hunger, misery and poverty of other nations whose citizens are unable to enjoy even elementary human rights. The nations of the world are becoming more and more dependent on one another and it will not be possible to preserve a lasting peace so long as glaring economic and social imbalances persist.
Source: Mater et Magistra (Vatican.va)