but demonstratives do not distinguish between the nominative, accusative, and genitive in either the singular or the plural, and the same therefore applies to the dual. They said: qāma hādhā (“this one stood”), akramtu hādhā (“I honored this one”), and marartu bi-hādhā (“I passed by this one”). The plural hā’ulā’i (“these”) likewise remains unchanged. The same applies to the dual: hādhāni (“these two”), akramtu hādhāni (“I honored these two”), and marartu bi-hādhāni (“I passed by these two”). The proper grammatical analogy here is therefore to assimilate its dual to its own singular and plural, rather than to the dual of another kind of noun, which is itself governed by its own singular and plural.

With declinable nouns, the dual follows the singular and plural. Thus, one says rajulun (“a man”), rajulāni (“two men”), and rijālun (“men”). The noun is declinable in all three forms: case inflection appears in its dual just as it appears in its singular and plural.

It thus becomes clear that those who claim that Arabic grammar requires inna hādhayni (“indeed, these two”) have no transmitted evidence for this from the known language of the Quran—the language in which it was revealed. Rather, that language requires the dual demonstrative to remain indeclinable, retaining a single form in all three cases, just like singular and plural demonstratives.

On this basis, whether one says that the alif is the singular’s alif with a nūn added, or that it is a dual marker and the original alif has been omitted, or, rather, that this alif combines both functions—this is the substance of Ibn Kaysān’s answer. Al-Farrā’s statement is equivalent in meaning, as is al-Jurjānī’s, and likewise the statement of those who say that its alif resembles the alif in yafʿalāni (“the two of them do”).