the object seen is necessarily colored. To reject these self-evident facts about vision is to reject the first principles naturally known to everyone and to invalidate all the sciences of optics and geometry.

These people—that is, the Ashʿarīs—have said that one of the cases in which a judgment concerning the observable must be extended to the unseen is that of a condition. For example, we judge that every knowing being is living, because life is manifestly a condition for the existence of a knowing being in the observable realm. If that is so, we say to them: “Likewise, these things are manifestly conditions of vision in the observable realm. So extend this judgment to the unseen, in accordance with your own principle.”

Abū Hāmid sought, in his book known as al-Iqtisād, to