This thesis is a study of the history of the establishment of the independent
Ismä i1i states in Yemen, which arose out of the Fatimid empire. It also analyses
Ismá`ili doctrines and some of their literature and focuses in particular on two little - known manuscripts which are anti- Ismá`fli refutations. The Introduction presents a
critical survey of the primary and secondary sources used in this study. The first chapter
is an attempt to summarise the origins of Shiism and to present the development of
Ismá`ilism as a result of the fragmentation of the Shiite entity into three groups: the
Zaydis, the Twelvers and the Ismá`ilis. The second is an historical analysis of the
consequences in Yemen of the decline of Abbasid authority, and of its impact on the
tribal powers, the Ziyddids, the Manákhids and the Yu`firids. It also mentions the arrival
of the two Ismá`ili dá cs in Yemen, their success in establishing the first Ismá`ili state
there, and the end of that state as a result of conflict between these two (id 'is. The third
chapter gives an edition of an early Zaydi manuscript with an introductory section
concerning the manuscript and its author. This work is an example of the way in which
after the downfall of the Ismá`ili state in Yemen and the spread of the Ismá`ili da'wa in
the Islamic regions, the enemies of the Ismá`ilis began by the fourth /tenth century to
attack the Ismá`ilis in their books. The Zaydis were one such Muslim group. The fourth
chapter shows how during the fifth /eleventh century, the Ismá`ilis organized themselves
and united their forces under the command of `Ali ibn Muhammad al- Sulayhi, who
together with his successors ruled Yemen for almost a century. The fifth chapter presents
an edition with selected translations of some unknown Sunni texts of the sixth /twelfth
century which attack Ismá`ili doctrines. Particular attention is given to the work entitled
Mukhtasar fi `Agá'id al- Thaldth wa Sab`in Firqa by Abú Muhammad
