This paper will focus on the Arabic grammatical tradition and, in particular, on the new arrangement, in the 4th/10th c., of grammatical matters already elaborated in the first centuries of Islam. With this aim in mind we will take into consideration two representative grammatical treatises of the 8th c. and the 10th c.: Sībawayh’s Kitāb and Ibn al-Sarrāj’s al-Uṣūl fī l-naḥw, which both represent watershed moments in the history of the Arabic grammatical tradition. Abū Bakr ibn al-Sarrāj’s philosophical training is obvious in the way he approaches the subject through the precise description of single items and in the laboured logic of the subdivision of his treatises. He follows the principle of “comprehensive subdivisions” (taqāsīm) borrowed from the logic he had studied under the direction of al-Fārābī. Ibn al-Sarrāj’s method of organizing and introducing linguistic matters will be contrasted with the approach of the father of Arabic grammar, Sībawayh, who wrote – two centuries earlier – the most comprehensive description of Arabic.