The Theory of Arabic Sentences in the Mughni

The second major section of the Mughni al-Labib presents Ibn Hisham's systematic account of Arabic sentence types and their grammatical properties. This section goes considerably beyond the treatment in the Shudur adh-Dhahab, which focused on practical sentence analysis. The Mughni's sentence theory is analytically more ambitious, addressing questions about the nature of sentences and clauses that go to the foundations of Arabic grammatical theory.

Ibn Hisham's central distinction in this section is between the jumlah (sentence) proper and the shibh al-jumlah (quasi-sentence) — prepositional phrases and adverbial phrases that share some but not all properties of full sentences. This distinction has important consequences for grammatical analysis: when a phrase with sentence-like properties appears in a position that would normally be occupied by a sentence, does it count as a sentence and carry the grammatical properties of sentences, or does it function differently because it is not a full sentence? Ibn Hisham's analysis of this question is one of his most original contributions.

The treatment of sentence embedding is equally important. Arabic allows sentences to appear in positions normally occupied by single words — as predicates, as subjects, as complements of particles, as modifiers of nouns (relative clauses). The grammar of these embedded sentences — what grammatical position they occupy, whether they carry i'rab marking, how they relate to the sentence in which they are embedded — requires careful analysis that the Mughni provides comprehensively.

Ibn Hisham also addresses the phenomenon of sentence conjunction (al-atf ala al-jumlah) — joining two sentences with a coordinating conjunction — and distinguishes it from the joining of two words or phrases within a sentence. The grammatical relationships between conjoined sentences are different from those between conjoined words, and the conditions under which each conjunction particle can join sentences (as opposed to joining smaller constituents) are specified in detail.

The section culminates in a treatment of the general conditions governing the use of sentences in Arabic discourse — conditions related to information structure, topic and focus, and the relationship between a sentence and its discourse context. Ibn Hisham's attention to these discourse-level phenomena reflects his awareness that grammar does not operate sentence-by-sentence in isolation but that the grammatical choices in a sentence are affected by what has come before and what is expected to come after. This discourse sensitivity distinguishes the Mughni's sentence theory from more narrowly syntactic accounts.