In the January/February 2008 issue of Foreign Policy magazine, Graham E. Fuller, former Vice Chair of the National Intelligence Council of the CIA, engages in an interesting thought experiment.
Here it is:
Imagine, if you will, a world without Islam—admittedly an almost inconceivable state of affairs given its charged centrality in our daily news headlines. Islam seems to lie behind a broad range of international disorders: suicide attacks, car bombings, military occupations, resistance struggles, riots, fatwas, jihads, guerrilla warfare, threatening videos, and 9/11 itself. Why are these things taking place? “Islam” seems to offer an instant and uncomplicated analytical touchstone, enabling us to make sense of today’s convulsive world. Indeed, for some neoconservatives, “Islamofascism” is now our sworn foe in a looming “World War III.”
That's a spectacular counterfactual. If Muhammad hadn't spread his poison, then the history of the Middle East would have been profoundly altered in the 7th century. (It's likely that Jews would still be living in Makkah and Medina!) It's nonsensical to say that our world would be likely the same without that scourge.