Constantine VII, a 10th Century Byzantine Emperor wrote the following:
For each nation has different customs and divergent laws and institutions, and should consolidate those things that are proper to it, and should form and develop out of the same nation the associations for the fusion of its life. For just as each animal mates with its own tribe, so it is right that each nation should marry and cohabit not with those of other race and tongue but of the same tribe and speech. For hence arise naturally harmony of thought and intercourse among one another and friendly converse and living together; but alien customs and divergent laws are likely on the contrary to engender enmities and quarrels and hatreds and broils, which tend to beget not friendship and association but spite and division.
