Arabic grammatical thinking provides one of the richest and most significant contributions of medieval Islamic sciences to the history of human civilization. For the first time, this book traces down its formation during the second century of Islam (eighth century A.D.), before the age of the famous Halil b. Ahmad and his disciple Sibawayhi. Some 240 excerpts extracted from the earliest sources of the eighth and ninth centuries create a unique database, which is then analyzed critically. Consequently a clear scheme emerges of the sophisticated grammar of this pre-Halilian era. As a result, Halil's and Sibawayhi's revolt on this tradition is considered in detail.