Frank Lewis is Professor of Philosophy at the University of Southern California. He has also taught at the University of California, Los Angeles, at Stanford University, and at the University of Arizona. He is the author of Substance and Predication in Aristotle (1991), and of numerous articles in ancient philosophy, especially the philosophy of Aristotle. Robert Bolton is Professor of Philosophy at Rutgers University. He has also taught at MIT, the University of Pittsburgh, the University of Virginia, and the University of Maryland. He is the author of Science, Dialectique, et Ethique chez Aristotle (1996) and of many papers in ancient philosophy.