and can what is purely intelligible exist anywhere but in a living, rational being? For what is purely intelligible, whose existence in the realm of sense is inconceivable, exists only in the mind; and what exists only in the mind does not exist outside it. Thus, the investigation that extracted from perceptible things what is not perceptible extracted purely intelligible concepts peculiar to rational beings: the universals established in their minds. When a person conceives of Zayd or Amr and observes the resemblance between them, his mind abstracts from this a general, universal, intelligible meaning that cannot conceivably exist outside the mind.

This, then, is how universals exist. These intelligible universals are accidents inhering in the rational subject. Indeed, particular entities may exist externally without a person apprehending their universals, while intelligible universals may exist in minds without having any corresponding reality outside them—as when one conceives of intrinsically impossible kinds, and so forth. Whoever infers that something is possible and exists among external entities merely because it can be conceived in the mind is, in this matter, more astray than brute beasts.

Allah Most High says:

“We have certainly created for Hell many of the jinn and mankind. They have hearts with which they do not understand, eyes with which they do not see, and ears with which they do not hear. They are like livestock; rather, they are more astray.”
Al-A'rāf: 179.

And Allah Most High says:

“Those who deny Our signs are deaf and mute, in darkness.”
Al-An'ām 39.