Focusing on the medieval reception of Book Zeta of Aristotle's Metaphysics, Volume One of this work offers an unprecedented and philosophically oriented study of medieval ontology against the background of the current metaphysical debate on the nature of material objects. Volume Two makes available to scholars one of the culminating points in the medieval reception of Aristotle's metaphysical thought by presenting the first critical edition of Book VII of Paul of Venice's Commentary on Aristotle's Metaphysics (1420-1424).