Mr. Wansbrough insisted that the text of the Koran appeared to be a composite of different voices or texts compiled over dozens if not hundreds of years. After all, scholars agree that there is no evidence of the Koran until 691 -- 59 years after Muhammad's death -- when the Dome of the Rock mosque in Jerusalem was built, carrying several Koranic inscriptions.

These inscriptions differ to some degree from the version of the Koran that has been handed down through the centuries, suggesting, scholars say, that the Koran may have still been evolving in the last decade of the seventh century. Moreover, much of what we know as Islam -- the lives and sayings of the Prophet -- is based on texts from between 130 and 300 years after Muhammad's death.

In 1977 two other scholars from the School for Oriental and African Studies at London University -- Patricia Crone (a professor of history at the Institute for Advanced Study in Princeton) and Michael Cook (a professor of Near Eastern history at Princeton University) -- suggested a radically new approach in their book ''Hagarism: The Making of the Islamic World.''

Since there are no Arabic chronicles from the first century of Islam, the two looked at several non-Muslim, seventh-century accounts that suggested Muhammad was perceived not as the founder of a new religion but as a preacher in the Old Testament tradition, hailing the coming of a Messiah. Many of the early documents refer to the followers of Muhammad as ''hagarenes,'' and the ''tribe of Ishmael,'' in other words as descendants of Hagar, the servant girl that the Jewish patriarch Abraham used to father his son Ishmael.

In its earliest form, Ms. Crone and Mr. Cook argued, the followers of Muhammad may have seen themselves as retaking their place in the Holy Land alongside their Jewish cousins. (And many Jews appear to have welcomed the Arabs as liberators when they entered Jerusalem in 638.)

The idea that Jewish messianism animated the early followers of the Prophet is not widely accepted in the field, but ''Hagarism'' is credited with opening up the field. ''Crone and Cook came up with some very interesting revisionist ideas,'' says Fred M. Donner of the University of Chicago and author of the recent book ''Narratives of Islamic Origins: The Beginnings of Islamic Historical Writing.'' ''I think in trying to reconstruct what happened, they went off the deep end, but they were asking the right questions.''