This book makes available to scholars the unpublished proto-scholastic "Commentary on the Psalms," composed by one of the outstanding figures of the early twelfth century, Gilbert of Poiters (Gilbert Porreta). The commentary had its origins in the atmosphere of experimentation which characterized the schools of Laon, Chartres and Paris in the first decades of the century. Its unique "mise en page," its methodology and its connection to other texts - especially glossed classical texts, the "Glossa ordinaria" and the writings of Peter Lombard - are explored. Gilbert's "Commentary" is a text critical for the understanding of the development of the discipline of theology in the twelfth century schools.