I think it's hard to talk about the Muslim world and Christian world as blocks.

Thus, biologically speaking the American people are literally only half an immigrant people.

Some Westerners […] have argued that the West does not have problems with Islam but only with violent Islamist extremists. Fourteen hundred years of history demonstrate otherwise.

Countries will cooperate with each other, and are more likely to cooperate with each other when they share a common culture, as is most dramatically illustrated in the European Union. But other groupings of countries are emerging in East Asia and in South America. Basically, as I said, these politics will be oriented around, in large part, cultural similarities and cultural antagonism.

I wouldn't rule out the possibility of Muslim or at least Arab countries developing some form of organization comparable to the European Union. I don't think that's very likely, but it conceivably could happen.

But then I came to the conclusion that no, while there may be an immigration problem, it isn't really a serious problem. The really serious problem is assimilation.

It is my hypothesis that the fundamental source of conflict in this new [post-Cold-War] world will not be primarily ideological or primarily economic. The great divisions among humankind and the dominating source of conflict will be cultural. Nation states will remain the most powerful actors in world affairs, but the principal conflicts of global politics will occur between nations and groups of different civilizations. The clash of civilizations will dominate global politics. The fault lines between civilizations will be the battle lines of the future.