inasmuch as its occurrence alongside prophethood constitutes a breach of the ordinary course—whereas the same occurrence, standing by itself, does not. Prophethood is itself an extraordinary event, so only what is likewise extraordinary can entail it.

Hence, when someone maintains, “His truthfulness is known only by the miracle, that is, by what breaks the natural order,” two possibilities arise. If by “miracle” he means the general sense—a sign whose very existence necessarily proves his veracity—then it is invalid to confine that proof to marvels produced outside the Prophet himself. But if he restricts the word to one particular class of miracles while admitting that all classes share the capacity to prove his claim, his denial is likewise unsustainable.

As for phenomena that may occur with or without prophethood—those that can be found with a truthful claimant and with an impostor alike—such things are no proof at all. By contrast, the categories of signs that God displays at a prophet’s hands, through which his truthfulness becomes known, include nothing that can appear at the hands of a liar.

Indeed, an impostor possesses no evidence save what necessarily exposes his deception. Whatever points to a liar’s falsehood can never point to the truthfulness of the truthful, and vice-versa: the proof of falsehood is inseparable from falsehood, and the proof of truthfulness inseparable from truthfulness. The two are opposites, and it is impossible for one who claims prophethood to be both a genuine prophet and a pretender; opposites cannot coexist. Accordingly, a single thing can never serve as evidence for both opposites.

This principle is of benefit in many contexts: