They have cited this point, and the logicians mention it as well in their discussion of the Muḥaṣṣal and the like.

This appears in purely schematic illustrations: when the object is to establish the predicate C for the subject A and the middle term is B, they say, “Every A is B, and every B is C; therefore every A is C.”

Yet this requires that both the major and the minor premise first be verified. If, instead, one says, “Every A is C by analogy with D, because D is C—and it is C only insofar as it is B, while A too is B—therefore A is C, since both A and D share the property that entails C, namely B,” the meaning is sound, just as in the first form, but it introduces an additional example—D—to which A is compared, even though the middle term, B, is present in them both.

As for their claim concerning demonstration (burhān), they maintain that it yields the perfective sciences. They hold that a demonstration must contain a universal proposition; hence it can establish only a universal conclusion, and they affirm that demonstration conveys universals alone.

The noblest of these universals are the purely intelligible ones that admit neither change nor alteration. Through them the soul attains perfection and becomes an intelligible world parallel to the existent world, unlike propositions that are liable to variation.

Thus, when the sought objects are intellectual universals that do not admit alteration or change, these are secured only by rational propositions whose acceptance is necessary—in fact, only in propositions whose modality is necessity, such as “Every human being is an animal,” or “Every existent is either necessary or contingent.”