Pope John XXIII
Pacem in Terris §97
Pacem in Terris: On Establishing Universal Peace in Truth, Justice, Charity, and Liberty
97 It is worth noting, however, that these minority groups, in reaction, perhaps, to the enforced hardships of their present situation, or to historical circumstances, frequently tend to magnify unduly characteristics proper to their own people. They even rate them above those human values which are common to all mankind, as though the good of the entire human family should subserve the interests of their own particular groups. A more reasonable attitude for such people to adopt would be to recognize the advantages, too, which accrue to them from their own special situation. They should realize that their constant association with a people steeped in a different civilization from their own has no small part to play in the development of their own particular genius and spirit. Little by little they can absorb into their very being those virtues which characterize the other nation. But for this to happen these minority groups must enter into some kind of association with the people in whose midst they are living, and learn to share their customs and way of life. It will never happen if they sow seeds of disaffection which can only produce a harvest of evils, stifling the political development of nations.
Source: Pacem in Terris (Vatican.va)