Abu Ya'qub Ishaq al-Sijzi

Abu Ya'qub Ishaq al-Sijzi, called Khayshafudi (a conjectural reading), was an Ismaili dai and one of the sect's most important authors. His surviving work on the philosophical wing of Ismailism is the main source for that tradition in the 4th/10th century, and the date and identity of his death are disputed.

The same EI entry, following al-Khuraymi and unsigned, treats Ishaq-i Sijzi, the Ismaili dai, nicknamed Khayshafudi (a conjectural reading), one of the sect's most important authors. Rashid al-Din reports that after the execution of al-Nasafi in Bukhara in 331/942 he fell into the hands of the amir Khalaf b. Ahmad, of the second Saffarid dynasty, who probably had him killed. The usual statement that Abu Ya'qub was executed in 331 with al-Nasafi is therefore wrong. His surviving books are many; the chief one seems to be al-Iftikhar, dated after internal evidence to about 360/971. Only the Kashf al-Mahjub has been published (Corbin, Tehran 1949), in a Persian version, the Arabic original being lost. His system is largely based on that of al-Nasafi, who introduced Neoplatonic philosophy into Ismailism around 300 AH, and he wrote a lost defence of al-Nasafi's al-Mahsil against Abu Hatim al-Razi. His books are the main source for the philosophical wing of Ismailism in the 4th/10th century. The article doubts that he is the same person as the Abu Ya'qub, dai of Rayy in the middle of the 4th/10th century, whom the Fihrist mentions. ¹