 He believes that it is only our mind which can impose a unity to a plurality of four distinct sensible entities. There is nothing in the extramental world which can naturally bind four detached things in such a way that they collectively accept the accident of four-ness. Thus, for Suhrawardī numbers (and mathematical objects in general) are only mind-dependent (iʿtibārī) things (Ziai 1990: 108; Walbridge 2000: 63 and 78–79). A similar line of argument is developed by Mullā Ṣadrā (d. 1640). He accepts that there are pluralities in the extramental world. But he insists that it is only through the activity of our mind that a group of distinct objects can be considered a unity. There is nothing in the extramental world which bestows unity to an arbitrary group of distinct objects (Mullā Ṣadrā, Al-Shawāhid al-rubūbīya, [1982: 65]). This line of argument against the consideration of numbers as properties of physical objects reminds us of Frege’s criticism of this idea (Frege 1884: §§ 21–25).