Ismā‘īlism appeared in the Iraqi region at the end of the second century. Through the activities of secret da‘wah carried out for almost a century, the sect has spread in Iraq, Khorasan, Mawarannahr, Bahrain, Yemen and North Africa. The establishment of the Fatimid Caliphate in the 3th/10th century was a turning point in the history of the sect because the first time in its history, Ismā‘īlism gained an official state support. However, in the early periods, the sovereignty of this state was limited to North Africa. By the second half of the 4th (11th) century, the Fatimids became an important political rival to the Abbasids. They managed to conquer Egypt, where Sunnis lived mostly, and then Syria. With this rapid rise, its opponents’ discourse of Ismā‘īlism began to become very negative. For example, al-Qādir Billāh, the Abbasid caliph, issued a manifesto in 402/1012 and claimed that they came from Daysan b. Sa‘id al-Khurrami. Abd al-Kahir al-Baghdadi, who lived in the same period with him, went one step further and claimed that they were Dahri (Materialist). In the post-Baghdadi period, Nizam al-Mulk, Gazzâlî and Fahruddin al-Râzî continued similar claims. In this article we will focus on these scholars’ claims on the non-Islamic origin of Ismā‘īlism and try to analyze historical and religious background of these discourse.