The Tathbit al-imama attributed to the Fatimid Imam-Caliph al-Mansur (334–341/946–953) is an important early Ismaili treatise on the legitimacy of the Imamate of ʿAli b. Abi Talib and that of the Ismaili Imams from among his progeny. As one of the earliest Ismaili works on this crucial and fundamental Shiʿi subject it can thus be considered a major treatise on the doctrine of the Imamate.
The Tathbit al-imama does not deal with the metaphysical significance of the imamate. Rather, it concentrates on its legal and historical aspects, using proofs derived from the Qurʾan, hadith and logical arguments. In this regard, it is directed at the Islamic public in all its different religious affiliations.
In the way it discusses the necessity of the Imamate itself, the right of the Imams to the vicegerency of Prophet Muhammad, and the validity of Divine designation in contrast to election by the umma, it is likely that the Tathbit al-imama could have also meant to serve as a guide book for the Ismailis in legitimising the ʿAlid state ruled by the Fatimid Imam-Caliphs.
This edition has been compiled from two manuscripts of the Tathbit, both of which are now in the collections of the library of The Institute of Ismaili Studies, with the Arabic text carefully translated into idiomatic English to retain the character and flavour of the original text as much as possible.