This dissertation examines the Fāṭimid Ismā‘īlī text kitāb al-fatarāt wa-l-qirānāt, attributed to the fourth/tenth-century missionary Ja‘far b. Manṣūr al-Yaman. While this text is widely-known in scholarship to address the Islamicate occult sciences (astrology, divination, lettrism, and other varieties of magical practices), the majority of prior scholarly work on k. al-fatarāt wa-l-qirānāt is limited to questions of authorship and dating. The main goal of this dissertation is to set aside those questions and instead investigate how the text presents a specifically Ismā‘īlī view of the occult sciences, as well as to examine the overall structure, contents, and arguments of the text. This study thus reveals several important features that will hopefully allow for fruitful further study of k. al-fatarāt wa-l-qirānāt. First, the text contains perhaps the most detailed discussion in medieval Ismā‘īlī literature on fatarāt (chapter 2), or the interim times between imams and prophets, a feature alluded to in other Ismā‘īlī works on prophetic histories but its implications for the ongoing necessity of the imamate not examined. Second, with respect to the Ismā‘īlī occult sciences, chapters 3 and 4 examine the ways that ta’wīl sensibility-- the wider applicability of a ẓāhir and bāṭin to all phenomena and not merely scripture--creates an astrology (chapter 3) and lettrism (chapter 4) that is separate from and superior to “ordinary” occult sciences with its origin in the hidden knowledge of the prophetic lineage. Lastly, this dissertation also contains an English-language outline of k. al-fatarāt wa-l-qirānāt (chapter 1) as well as an edition of the Arabic text compiled from available manuscripts (appendix I).