 In his Al-Mawāqif, al-ʾĪjī challenges the reliability of mathematical sciences due to their engagement with estimative entities that are frailer (awhan) than a spider’s web. This analogy refers to the Quran 29:41 (Fazlıoğlu 2014: 6–7). A similarly skeptical view of mathematics is defended by Shams al-Dīn Muḥammad al-Bukhārī (d. 1429) in his commentary on al-Kātibī al-Qazwīnī’s Ḥikma al-ʿayn. Like many of his predecessors, al-Bukhārī contends that, compared to physics and metaphysics, mathematics is a less reliable source of knowledge regarding the concretely existing things. It is in response to such views that al-Jurjānī appeals to the machinery of nafs al-ʾamr to defend the reliability of mathematics. He accepts that mathematical objects are estimative and imaginary. But he believes that they are imagined correctly and in accordance with the extramental reality. In this respect, they are entirely different from fictional entities, like ruby mountains or two-headed men, which do not reflect anything in the extramental reality (Hasan 2017: 7). Although mathematics originates from estimation, it can still express significant truths about things as they are in nafs al-ʾamr. He therefore believes that the judgment of estimation can in principle conform to that of intellect; particularly in the context of mathematics where the products of estimation are constructed in accordance with what we perceive from the extramental world through our senses. Although mathematical objects are estimative entities, they are not the outcome of a fanciful imagination which has no connection to reality, or so al-Jurjānī seems to believe (Fazlıoğlu 2014; Hasan 2017). The theory of nafs al-ʾamr was, among other things, the most promising attempt by Muslim thinkers to reconcile an anti-realist account of the ontology of mathematics with a realist account of mathematical truths. This theory is intended to provide an explanation of how mathematics, as the study of purely estimative entities, can be useful in the study of the physical world. Unfortunately, the extent of the success of this project has not been comprehensively studied yet.