Wisdom of the Ages

The Roman Empire has won significance, and its rulers became famous and mighty, because numerous nobles and sages from various countries congregated there […] As settlers come from various countries and provinces, they bring with them various languages and customs, various instructive concepts and weapons, which decorate and glorify the royal court, but intimidate foreign powers. A country which has only one language and one kind of custom is weak and fragile. Therefore, my son, I instruct you to face [the settlers] and treat them decently, so that they will prefer to stay with you rather than elsewhere, because if you were to destroy all that I have built and squander what I have collected, then your empire would doubtless suffer considerable loss.

Thus King St Stephen I of Hungary, to his son, in an exhortation probably drawn up by a German monk. As quoted in The Hungarians by Paul Lendvai. Emphasis added.