Section: Refuting the Christians’ appeal to the earlier prophets as proof of the soundness of their religion

The very methods by which the prophethood of the former prophets is established serve equally to establish the prophethood of the Prophet, peace and blessings be upon him.

We have already explained that no one may cite a single verse of the Quran, or anything transmitted from Muhammad—peace and blessings be upon him—unless he first affirms his messengership. If his messengership is denied, one can neither acknowledge the prophethood of anyone else nor use any prophetic utterance as evidence, because to reject him is necessarily to reject them as well. Hence, whenever the prophethood of another prophet is conceded, his prophethood is likewise confirmed, and that confirmation invalidates their religion. In other words, the soundness of their proof would require the falsity of the very claim it is meant to establish, while the falsity of the claim demands the falsity of the proof. A proof is inseparably linked to what it proves: when the inseparable exists, the necessary follows, and when the necessary is negated, the inseparable is negated. Thus, when a proof is sound, the point proven is sound; and when the point proven is unsound, the proof must also be unsound, for falsehood can never rest upon a sound proof.

Accordingly, if Muhammad—peace and blessings be upon him—is indeed the Messenger of Allah, their religion is invalid, and once their religion is invalid, no sound evidence can be produced for its truth. If, on the other hand, he is not the Messenger of Allah, it is still impermissible to take his words as evidence. Therefore, in either case, their attempt to reason on the basis of his statement is null and void.