http://www.nationalreview.com/articles/300131/uncovering-early-islam-daniel-pipes
The year 1880 saw the publication of a book that ranks as the single most important study of Islam ever. Written in German by a young Jewish Hungarian scholar, Ignaz Goldziher, and bearing the nondescript title Muslim Studies (Muhammedanische Studien), it argued that the hadith, the vast body of sayings and actions attributed to the Islamic prophet Mohammed, lacked historical validity. Rather than provide reliable details about Mohammed’s life, the hadith, Goldziher established, emerged from debates two or three centuries later about the nature of Islam.
(This is like today’s Americans debating the Constitution’s much-disputed Second Amendment, concerning the right to bear arms, by claiming newly discovered oral transmissions going back to George Washington and Thomas Jefferson. Obviously, their quotations would inform us not what was said 225 years ago but about current views.)
Since Goldziher’s day, scholars have been actively pursuing his approach, deepening and developing it into a full-scale account of early Islamic history, one that disputes nearly every detail of Mohammed’s life as conventionally understood — born in a.d. 570, first revelation in 610, flight to Medina in 622, death in 632. But this revisionist history has remained a virtual secret among specialists. For example, Patricia Crone and Michael Cook, authors of the synoptic Hagarism (Cambridge University Press, 1977), deliberately wrote obliquely, thereby hiding their message.
Now, however, two scholars have separately ended this secrecy: Tom Holland with In the Shadow of the Sword, and Robert Spencer with Did Muhammad Exist? As their titles suggest, Spencer is the bolder author, and so is my focus here.