Another instance of this is when carrion cannot be distinguished from lawfully slaughtered meat. Only one of the two is forbidden in the sense that eating it incurs punishment. Thus, if someone eats both, he is punished for eating one dead animal, not two. Avoiding the other is obligatory as a means.

Accordingly, the statement, “Both are forbidden,” is correct in this respect. The statement, “Only one of them is forbidden in itself,” is also correct in its corresponding respect. This parallels the statement, “One must use what is not itself obligatory as a means to fulfill an obligation.” The objection of Abū Hāmid al-Ghazālī and Abū Muhammad al-Maqdisī to those who say this, and to those who say that only one of the two is forbidden, does not accord with the jurists’ approach. Ultimately, it amounts to a “verbal dispute.” For the obligation and prohibition attaching to one do not attach to the other; rather, those attaching to the other are of a different kind.

Thus, even if a man could not distinguish his slave woman from an unrelated woman at night and had intercourse, believing intercourse with one to be lawful and with the other forbidden, his child by his slave woman would be legally recognized as his, unlike a child by the other woman. Suppose that he could not distinguish his slave woman from an unrelated woman, married one of them and was, hypothetically, subjected to the prescribed punishment, then married the other: he would not be liable to two prescribed punishments. In fact, no prescribed punishment applies in this case, since the woman he married might be the unrelated woman.

This also resolves “al-Kaʿbī’s objection.” Refraining from the forbidden act is itself intended, whereas engaging in one of its opposites is a means. Thus, if it is said that a permissible act is obligatory in the sense that means are obligatory—that is, it may serve as a means to perform an obligation or refrain from a forbidden act—this is true.