This volume contains a close translation, suitable for students without a knowledge of Greek, of the seventh and eighth books of Aristotle's Metaphysics, together with a thorough and careful philosophical commentary. In these difficult books, which are central to his metaphysical system, Aristotle discusses the nature of perceptible reality. In particular, he discusses which of matter and form might be the basic reality of things, and he frequently contrasts his own view of form with the Platonic view. Several other topics are treated which are of central importance to his metaphysics, such as the notions of essence and definition, the status of universals, and the concept of a unity.