And a person may conceive of many things, regard them as possible, and not know that they are impossible, even though they are impossible in external reality for other reasons.

If he says, “I mean possibility in the mind,” this does not help him, for it amounts merely to not knowing that it is impossible for that attribute to belong necessarily to the thing.

If he says, “I mean possibility in external reality: I know that anything possessing an attribute, or anything possessing a size, could be otherwise,” he is making an unwarranted assertion. This is a universal proposition encompassing individual instances that none but Allah Most High can enumerate, yet he has no evidence establishing this possibility in external reality for all those instances. At most, he has seen certain things possessing attributes and sizes that admit of being otherwise. If he then reasons by analogy from the observed to the unobserved, this is among the most unsound forms of analogy, because their realities differ and because the same argument can be turned against him.

He may be told: “We have only ever seen things possessing attributes; therefore, let the unobserved be judged by analogy with the observed.”

It may also be said: “Everything that subsists in its own right possesses attributes and a size.” This is closer to reason than their analogy, since no counterexample to it is known.

As for the assertion, “Anything possessing attributes and a size admits of being otherwise,” it is not known to hold universally. How, then, can an analogy not known to be lacking compare with an analogy not known to hold universally?

People agree that they have never seen anything existing without attributes and a size. They do not, however, agree that everything they have seen could exist with different attributes