The late 8th/14th century saw a renaissance of high occultism throughout Islamdom—a development alarming to puritan scholars. This includes Ibn Ḫaldūn (d. 808/1406), whose anti-occultist position in the Muqaddima is often assumed to be an example of his visionary empiricism; yet his goal is simply the recategorization of all occult sciences under the twin rubrics of magic and divination, and his veto persuades more on religious and social grounds than natural-scientific. Restoring the historian’s argument to its original state of debate with the burgeoning occultist movement associated with the Mamluk sultan Barqūq’s (r. 784/1382-791/1389 and 792/1390-801/1399) court reveals it to be not forward-thinking but rather conservative, fideist and indeed reactionary, as such closely allied with Ibn Qayyim al-Ǧawziyya’s (d. 751/1350) puritanical project in particular; and in any event, the eager patronage and pursuit of the occult sciences by early modern ruling and scholarly elites suggests that his appeal could only fall on deaf ears. That it also flatly opposed the forms of millennial sovereignty that would define the post-Mongol era was equally disqualifying. I here take Šaraf al‑Dīn ʿAlī Yazdī (d. 858/1454), Ibn Ḫaldūn’s younger colleague and fellow resident in Cairo, as his sparring partner from the opposing camp: the Timurid historian was a card-carrying occultist and member of the Iḫwān al-Ṣafāʾ network of neopythagorean-neoplatonic-monist thinkers then gaining prominence from India to Anatolia via Egypt. I further take geomancy (ʿilm al-raml) as a test case, since Yazdī wrote a tract in defense of the popular divinatory science that directly rebuts Ibn Ḫaldūn’s arguments in the Muqaddima. To set the stage for their debate, I briefly introduce contemporary geomantic theory and practice, then discuss Ibn Ḫaldūn’s and Yazdī’s respective theories of occultism with a view toward establishing points of agreement and disagreement; I also append a translation of Yazdī’s tract as a basis for this comparison.