 Abū l-Barakāt and al-Rāzī’s definition of motion was in turn picked up by the polymath, Athīr al-Dīn al-Abharī (d. 1262 or 1265), who used it in his highly successful textbook of natural philosophy, Hidayat al-ḥikma. The definition would be common at least until it was challenged by the great Shia philosopher and theologian, Mullā Ṣadrā (d. 1636). Drawing on Avicenna’s earlier account of motion, which Mullā Ṣadrā defends at least in his Sharḥ al-Hidaya (Mullā Ṣadrā, 2001, 103–105), he reminds his reader that motion is itself an equivocal term and is said in no less than two ways: traversal-motion and intermedial-motion. Abū l-Barakāt and Fakhr al-Dīn al-Rāzī’s rejoinder to Avicenna’s original charge of circularity works, observes Mullā Ṣadrā, only if the sense of motion is the same in the two converted premises. They are not maintains Mullā Ṣadrā. While it is true that time-better-know-to-us can be used to understand motion, the motion in question is traversal-motion, that is, the idea of motion that, according to Avicenna, exists only mentally. In contrast, the sense of motion used to explain the nature of time is not traversal-motion but intermedial-motion, that is, the extra-mental motion that exists in the world. Thus the actual premises are not those noted by Abū l-Barakāt and Fakhr al-Dīn al-Rāzī, but the following two: