"The first followers of Christ didn’t consider themselves ’’Christians’’; they were Jews who believed that a fellow Jew named Jesus Christ was the long-awaited messiah. It took centuries for Christianity to evolve and solidify as a distinct faith with its own doctrine and institutions.
"In 'Muhammad and the Believers: At the Origins of Islam,' University of Chicago historian Fred M. Donner wants to provide a similar back story for Islam — a religion which, in the popular imagination, sprang wholly formed from the seventh-century sands of Arabia. Mohammed preached at the juncture of the Roman and Sassanian empires, winning support from Christians, Jews, Zoroastrians, and various deist polytheists. According to Donner, Mohammed built a movement of devout spiritualists from many faiths who shared a few core beliefs: God was one, the end of the world was near, and the truly religious had to live exemplary lives rather than merely pay lip service to God’s laws. It was only a century after Mohammed founded his 'community of believers' and launched the great Islamic conquest that his followers started to define their beliefs as a distinct religious faith."
For the past 30-40 years, Islamic origins has been perhaps the single most contentious area of Middle Eastern history. There is a very strong, internally coherent picture found in the Islamic historical tradition; however, this material probably dates from the late 8th century or later, and was written from the perspective of a learned class of Muslim religious specialists and functionaries in a government which legitimized itself on an Islamic basis. For these reasons, scholars have debated the degree to which it reflects what people would have thought or said during the early 7th century.
Some scholars have chosen to throw it out as unreliable, while others argue for its fundamental soundness. Donner fits into what I see as the fruitful middle ground of understanding the written sources as the products of a long period of transmitting information about the past and forming ideas that we might truly call historical. As I suggested back in this MESA post, these are the types of questions about which we've come to know a fair amount, perhaps enough to proceed on this thorniest of questions.
Historians of religion will not find Donner's work shocking, as religious leaders generally claim to be restoring the old rather than creating the new, purifying the impurities in or restoring the true message of whatever religious material is around them and serving as the context for their own ideas. In a point I've made before, Islam's DNA still points to the idea that it is the religion of Abraham, whose life is commemorated in the hajj. The prophet most frequently mentioned in the Qur'an is Moses. I won't be able to read it until June at the earliest, but Donner's work is definitely a milestone which historians 50 years from now will probably refer to as making important contributions even if they come to reject its overall argument.