The syllabic system, Σ, of the Arabic language is made up of no more than two patterns {Consonant-Vowel} and {Consonant-Vowel-Consonant}. Therefore two given strings of syllables CV and CVC cannot form a pair. There is, inevitably, a double opposition {C vs V}. In that chiasmus lies the organization of all Semitic languages. In the Arabic language that chiastic organization has been maintained until recently. Therefore the Arabic language constructed its system of nomination on combinations of consonants that constitute the roots of its units of nomination. And it used the end vowels of those units as the signifiants of its primitive function words. Another example of a chiasmus is the chiasmus that distinguishes the perfective aspect of Arabic verbs from their imperfective aspect. Some chiasmi occurring in the language seem rhetorical, but such cases are rare. In fact, the systematic organization of the language is a closed one, while the discourse is open. And it is in the discourse that rhetoric finds the liberty that it requires.