Abstract
Islamic heresiography has a long history whose roots go back to the second century of Hegira. The development process, which started with individual articles (maqālah), continued with encyclopedic works. As far as we know, the alphabetical classification of firqahs is the first attempt at Islamic heresiography. This classification, which was written by Muṣṭafá ibn Ibrāhīm in the late period of the Ottomans and reached the present day as a single copy, is remarkable in terms of both the author’s environment and the subjects it contains. This article suggests that the author lived in the 18th century and belonged to the Qāḍīzādelī environment. First, the identification of the author is clarified, and then the content of the heresiographical treatise is analyzed. Finally, the Arabic version of the text with the developed text structure is presented as an appendix.