In the final analysis the two procedures yield the same result, and I have expanded on this in other writings.

What I wish to add here is the following: we have already made it clear that a categorical (universal) syllogism can be recast as an analogy, and an analogy can likewise be expressed as a categorical syllogism. Thus, when someone argues in the question of homicide committed with a heavy instrument that it is deliberate, unmitigated aggression against an equal and therefore entails retaliation (qiṣāṣ) just as killing with a sharp weapon does, he has identified the shared element that grounds the ruling—namely, deliberate, unjust aggression against an equal.

This shared element is variously called the ʿilla (effective cause), the manāṭ (operative factor), the jāmiʿ (common denominator), the mushtarak (shared attribute), the muqtaḍā, the mujib, the bāʿith, the amārah, and other similar terms.

If he wishes to cast the argument in the form of a universal syllogism, he would say: “This act constitutes deliberate, unmitigated aggression against an equal; and every act that is deliberate, unmitigated aggression against an equal necessitates retaliation; therefore this act necessitates retaliation.”

The disagreement in both formulations centers on whether the act is in fact purely intentional, for the opponent contends that the intentional element is not fully established. My purpose here is not to debate the particulars of the case but merely to provide an illustration. The dispute concerns the minor premise—that is, whether the attribute is present in the subsidiary case. In analogical reasoning one may contest the presence of the attribute in the original case, deny its presence in the subsidiary case, or deny that it is the effective cause of the ruling.

This objection is called the “demand for proof” (suʾāl al-muṭālabah); it is the most serious challenge to an analogy, and its answer constitutes the backbone of qiyās, for qiyās stands or falls on proving that the shared attribute is indeed the operative factor in the ruling—the major premise. It is as though the objector were to say in this case: “We do not concede that every purely intentional homicide warrants retaliation.” Denying the ruling in the original case or denying the attribute in the original likewise amounts to denying the major premise in the categorical syllogism.

The only exception would be if the proponent produces independent evidence for the causal efficacy of the attribute without relying on any specific original case; this is pure causal reasoning. An example would be the claim: “An intoxicating beverage made from dates is forbidden because the intoxicating property itself necessitates the prohibition.”