The Ismailis have had a long and complex history. On two occasions, they had states of their own and, especially during the Fatimid period of their history, they made important contributions to Islamic thought and culture. But until recently, the Ismailis were studied and evaluated almost exclusively on the basis of evidence collected or fabricated by their detractors. These sources included the heresiographical and polemical works that aimed to refute and discredit the Ismailis, who had challenged the established order. From early on, the numerous other Muslim dynasties had launched a literary campaign against the Ismailis and their cause.
The Crusaders came into contact with the Nizari branch of the Ismailis in the 12th century in Syria. In time, the Crusaders and their occidental chroniclers produced their own myths of the Nizari Ismailis, who were made famous in Europe as the Assassins, the followers of a mysterious Old Man of the Mountain. These so called Assassin legends culminated in Marco Polo's elaborate synthesis.
In the 19th century, orientalists correctly identified the Isrnailis as a Shi‘i Muslim community. But in their more scientific studies of the Ismailis, the orientalists were obliged to base their thought on the few available Muslim sources rooted in hostility, and accounts and fanciful tales of the Crusading circles, rooted in “imaginative ignorance”. It was not until the 1930s that Ismaili Studies began to be revolutionized as a result of discoveries of a large number of genuine Ismaili texts, preserved secretly in private collections. This paper concludes by briefly surveying a number of major phases in modern Ismaili scholarship, including the contributions of the Ismaili Society of Bombay and The Institute of Ismaili Studies, London.