Since the autumn of 2001, various politicians, scholars, and media figures have speculated about the root causes of the September 11 terrorist attack on America. Most accept the U.S. government’s determinations that al-Qaeda, the international terrorist network headed by the radical Muslim fundamentalist Osama bin Laden, was responsible for the attack. Yet experts continue to debate what role religion and culture played in motivating extremists to participate in such devastating suicide raids.

Some analysts maintain that the September 11 attack was one result of a basic and long-standing incompatibility between Islamic culture and Western civilization. In an often-cited and controversial 1993 article, Harvard professor Samuel P. Huntington defined the increase in radical Islamic terrorism during the twentieth century as evidence of a deep rift among the world’s major civilizations—a division he believed would influence international relations in...