As for their objection—“Even when the possible alternatives are exhaustive, it may still be that the effective cause lies in the aggregate or in some component that is not found in the branch-case”—we answer: this can indeed occur in certain instances, such as conjectural questions in jurisprudence and the like. For example, when it is asked whether an emancipated bondwoman married to a slave, as in the incident of Barīrah, is granted the option of separation, one may argue that the reason is her having been under a deficient husband, or that it is her acquisition of mastery over herself, or perhaps the ruling results from the combination of the two.

Yet claiming that the rationale rests on something peculiar to the original case—whether that peculiarity be the whole or only a part—can be shown to be unfounded, just as we are able to establish the falsity of other negations. Consider the statement:

“Man is a sentient being that moves by volition by virtue of his animality, not his humanity; animality is shared between him, the horse, and all other animals; therefore he is a sentient being that moves by volition.”

In such a case it cannot be maintained that what is unique to man is the cause of his being sentient and voluntarily mobile; the cause lies solely in the element he shares with other animals.

The same applies when one says: “That which is eternal cannot be nonexistent, for its eternality is either intrinsic or owed to a necessitating cause that requires its being eternal in itself. Whatever is eternal in itself must, of necessity, exist in itself, because eternality is more specific than existence; whenever eternality holds, existence necessarily follows. Thus, if it is eternal in itself, it must be self-existent, and whatever exists in itself is necessarily self-sufficient; otherwise it would depend on an agent. Accordingly, the eternal is either necessary in itself or inseparably concomitant with that which is necessary in itself, and both are impossible to be nonexistent. For their non-existence would entail the non-existence of the Necessary Being; and if that Being could cease to exist, it would be susceptible to non-existence and therefore would not be necessary in itself. Hence, rational people are unanimously agreed that the eternal is either a self-existent Necessary Being or something inseparable from such a Being.”