This volume brings together papers by participants in the fourth annual USC/Rutgers conference in Aristotle, held at USC in December of 1992 on Aristotle's theory of matter. Five papers take up different applications of Aristotle's fundamental hylomorphic hypothesis: the account of human soul as form to the human body as matter; the unity of the substantial form and proximate matter in the individual substance; and the account of mixture at a lower level of matter. A final paper attempts to bring Aristotle's account of compound material substances in Metaphysics Zeta under the rubric of Aristotelian science. The distinguished contributors are James Bogen, Robert Bolton, Alan Code, Kit Fine, Frank Lewis, and Michael Wedin.