for calling bodies that screen things “veils” is a matter of self-evident linguistic knowledge, universally acknowledged by speakers of the language. Thus, a ruler’s chamberlain and an eyebrow are both called hājib (one that screens). To deny that a body can veil or be veiled is therefore to deny what is self-evidently known from the language.
Moreover, “veiling” and “screening” are closely related in meaning. His statement, “These screening bodies are only said to be a veil for such-and-such,” affirms that they screen things. How, then, can he affirm that they screen things while denying that they veil them? Furthermore, knowing that bodies prevent a person from seeing what lies behind them is a matter of sensory knowledge: a veil interposed between a person and the object of sight prevents him from seeing it.
As for his statement that what prevents a thing from being seen is the impediment that comes into being, this contradicts his earlier statement that, in his view, the veil consists in sight not being created. This is an absence, which does not require an existing contrary to prevent sight. This is plain, since hearing and sight both have positive existence in his view.
It should then be said: even if an impediment to sight inheres in the eye, this does not preclude a body from being an impediment, nor does it preclude that obstructing, veiling body from being the cause of this obstructing accident. Indeed, this does not preclude its bearing the designation