 Developing an account more or less similar to that of Avicenna, al-Bīrūnī accepts that some mathematical entities like lines and points exist in the physical world but they cannot be grasped by our external senses. Nevertheless, the data we receive through our sense experiences enable us to perceive these objects and/or to produce idealized constructions that do not exist in the extramental world (Samian 2011). However, he does not seem to have a clear picture of cognitive psychology in which the roles of different faculties are explicitly distinguished. That is why he wavers between two pictures, in one of which estimation (wahm) is the first faculty to apprehend mathematical objects, while in the other, this role must be played by intellect (ʿaql). On the latter view, nothing below the level of the intellect can perceive mathematical objects. Al-Bīrūnī’s hesitation between the two rival views becomes more apparent especially when we accept that both the Persian and Arabic versions of Kitāb al-tafhīm are written by himself. For instance, in the Arabic version, he claims that points cannot be conceived by any faculty other than the intellect (al-Bīrūnī [Astro]: 3). By contrast, in the Persian version, he attributes this role to estimation (al-Bīrūnī [Instr]: 7). He does not seem to consider any clear boundary between the intelligible (maʿqūl) and the estimative (mawhūm).