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The history of the quest for the "historical" Muhammad in the modern Western literature has its origins from the time (c. 1850 CE) of Sir William Muir and Alois Sprenger. Both of them suspected that much of the Islamic traditions on Muhammad, which were accepted by Muslims as authentic, were in fact forged. Their views were given a further impetus by Ignaz Goldziher who became convinced that the tradition literature had grown up after the Arab conquests, i.e., the aḥādīth did not reflect the life of Prophet Muhammad; rather they reflect the beliefs, conflicts and controversies of the first generation of Muslims. In other words, the aḥādīth reflect reality, but not the reality of seventh century Arabia but of Umayyad and early Abbasid empires. About half a century after Goldziher, Joseph Schacht applied the former's methodology and came up with what is called the backward growth of isnāds. Isnāds, he argued, tended to grow backward with time. In other words, traditions with worse isnāds are likely to be earlier and the ones with perfect isnāds betray their late development. Therefore, the legal rules formulated during later times, enshrined in ḥadīth and projected back to the life of the Prophet in order to give them an Islamic justification.