The principal purpose of this book is to introduce a critically important Shiite writer from the fourth (Islamic)/tenth (Christian) century to a general, modern audience. This is an especially difficult task because the person in question, Abū Ya‘qūb al-Sijistānī, remains little known in the scholarly literature about Muslim thinkers or even in the discussions of Islamic thought by Muslims themselves. His contribution to the development of philosophical Shiism in his time was crucial; yet almost no record of him and no overtly recognizable trace of his thought much outlasted the century in which he lived. His works did not find a place in standard Islamic collections, but were copied and preserved by a small remnant of the once much more powerful and larger Ismaili movement to which he belonged. Increasingly, his writings fell into a dark obscurity as they were guarded from outsiders, only to be rediscovered by modern scholars in the second half of the twentieth century.

Al-Sijistānī, however, in his ardent support of a particular version of Shiism and in his intense pursuit of philosophical and scientific fact to explain and complement these religious views, was not born or bred in such obscurity. His role in the early Ismaili da ‘wa did not limit or confine his interests or his audience.