This book offers a new edition, with English translation and commentary, of the Kitab al-Madal, which opens Avicennas (d. 1037) most comprehensive summa of Peripatetic philosophy, namely the Kitab al-Sifa. For the first time, the text is established together with a stemma codicum showing the genealogical relations among 34 manuscripts, the twelfth-century Latin translation, and the literal quotations by Avicennas first and second-generation students. In this book, Avicennas reappraisal of Porphyrys Isagoge is examined from both a historical and a philosophical point of view. The key-features of Avicennas theory of predicables are analyzed in the General Introduction and in the Commentary both in their own right and against the background of the Greek and Arabic exegetical tradition. Readers shall find in this book the first systematic study of the Madal which, in addition to being the only logical work of the Sifa ever transmitted in its entirety both in Arabic and in Latin, is crucial for understanding Avicennas conception of universal predicables at the crossroads between logic and metaphysics.