This book is a comprehensive study of the Kitāb of Sībawayhi (d. 180/796), undoubtedly the most authoritative work in the long history of Arabic grammar. It carefully examines the methodological concepts and methods that underline Sībawayhi’s analysis of Arabic and the way in which these methods evolved at the hands of later grammarians. Placing the Kitāb within the context of early Arabic philological activity, this book analyzes a wide range of its passages and demonstrates the coherency of its author’s system of grammatical analysis and the interrelatedness of his analytical tools and notions. In particular, Sībawayhi’s huge influence on the overall Arabic grammatical tradition is highlighted throughout the book. This notwithstanding, it is argued that most later grammarians largely neglect the semantic dimension which vividly features in Sībawayhi’s approach to language as a social behavior and his reconstruction of the internal thinking of the speaker and the listener.