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According to the elite newspapers and journals of opinion, the future of foreign affairs mainly rests on ideas: the moral impetus for humanitarian intervention, the various theories governing exchange rates and debt rebalancing necessary to fix Europe, the rise of cosmopolitanism alongside the stubborn vibrancy of nationalism in East Asia and so on. In other words, the world of the future can be engineered and defined based on doctoral theses. And to a certain extent this may be true. As the 20th century showed us, ideologies -- whether communism, fascism or humanism -- matter and matter greatly.

But there is another truth: The reality of large, impersonal forces like geography and the environment that also help to determine the future of human events. Africa has historically...