His account of the origin of Islam met with criticism from other scholars such as John Wansbrough of the University of London's School of Oriental and African Studies, and Patricia Crone and Michael Cook, in their book "Hagarism: The Making of the Islamic World (1977)", and Crone's "Meccan Trade and the Rise of Islam". However, Both Patricia Crone and Michael Cook have later suggested that the central thesis of the book "Hagarism" was mistaken because the evidence they had to support the thesis was not sufficient or internally consistent enough.