The encounter of medieval Jewish scholars with Arabic linguistic literature during the last decades of the tenth century CE produced one of the most important branches of Hebrew linguistics, namely, that of comparative Semitic philology. This branch not only changed the nature of Hebrew philology but influenced considerably the philological exegesis of the Bible as well. The purpose of the present study is to give a detailed overview of the medieval theoretical framework in which fourteen Hebrew philologists practised comparative Semitic philology during the tenth and eleventh centuries, from R. Saʿadiah Gaʾon at the beginning of this period until R. Isaac ibn Barūn at its end. This literary activity spread in the Arabic-speaking area from Iraq in the east, through the Land of Israel, Egypt and North Africa, to Andalusia in the west. This study also describes the contribution of each of these philologists, focusing on his specific characteristics. The study presents a full-scale description of the lexical comparisons of Hebrew with Aramaic and Arabic and resorts to comparative grammar only when necessary for the purposes of the study. Certainly, medieval comparative Semitic grammar as reflected in the works of these scholars as well as the comparative philology of the successors of Ibn Barūn are worth a comprehensive study but such a descriptions is beyond the scope of the present volume. At any rate, as regards a comparative lexicon, it seems that the general principles revealed here did not undergo significant change after Ibn Barūn.
This study has its origins in a dissertation written at the Hebrew University of Jerusalem in the years 1980–84, under the joint supervision of Professor Moshé Bar-Asher and the late Professor David Téné. In the last two decades, several works touching upon medieval grammatical thought in general and on comparative philology in particular have been published, both by myself and by others, especially in the light of new materials from the Cairo Genizah and other manuscripts that were then either inaccessible or unknown. The time has come for the publication of an updated study, for the benefit of scholars interested in medieval Hebrew philology, comparative Semitic philology and even general comparative philology.