"There is no clearer illustration of the importance of ideas to politics than the emergence of an Arab state under the Prophet Muhammad," Fukuyama writes. "The Arab tribes played an utterly marginal role in world history until that point; it was only Muhammad's charismatic authority that allowed them to unify and project their power throughout the Middle East and North Africa." Fukuyama's portrayal of religion as a unifying force in history will irk some atheists, for whom religion is at all times a source of intolerance, conflict, and violence. He does concede, however, that religion's role in the contemporary world is more problematic. Pluralistic societies require religions to coexist in proximity. As a result, he says, "integration today has to be based on shared political values, not deep, religiously rooted cultural beliefs."