In his quest for the historical Muhammad, Zeitlin's chief aim is to catch a few reliable glimpses of the birth of Islam and the role played by its extraordinary founder. Islam, as its Prophet came to conceive it, was a strict and absolute monotheism. How Muhammad had arrived at this view is not a problem or question for devout Muslims, who believe that the Prophet had received a revelation from Allah or God, mediated by the Angel Gabriel. For scholars, however, interested in placing Muhammad in the historical context of the 7th-century Arabian Peninsula, the source of the Prophet's inspiration is, in fact, a significant and even momentous question. For it is apparent that the two earlier monotheisms, Judaism and Christianity, constituted a definite and influential presence in the Hijaz, the region comprising Mecca and Medina. Indeed, Jewish communities were salient in the region, especially in Medina and in other not-too-distant oases. Moreover, in addition to the presence of Jews and Christians, there appears to have existed a third category of individuals, going by the name of Hanifs, who had grown dissatisfied with their polytheistic beliefs and who developed vague monotheistic ideas. Zeitlin tries to assess the extent to which these various religious influences shaped the emergence of Islam and the development of the Prophet's beliefs. Zeitlin also seeks to understand how it was that the process set in motion by Muhammad led, not too long after his death, to the establishment of a world empire. In a counter-factual thought experiment, he proposes that if Muhammad had remained in Mecca and never had migrated to Medina, Islam either would have remained a small sect or would have been absorbed by the earlier monotheisms, thus disappearing altogether.