Terry Penner is Professor of Philosophy, Emeritus, and was, for a time, Affiliate Professor of Classics at the University of Wisconsin-Madison. In Spring 2005 he was A. G. Leventis Visiting Research Professor of Greek in the University of Edinburgh. His previous publications include The Ascent from Nominalism: Some Existence Arguments in Plato's Middle Dialogues(1986) and numerous articles on Socrates. Christopher Rowe is Professor of Greek at the University of Durham; he was Leverhulme Personal Research Professor from 1999 until 2004. His previous publications include commentaries on four Platonic dialogues; he has edited The Cambridge History of Greek and Roman Political Thought (with Malcolm Schofield, 2000) and New Perspectives on Plato, Modern and Ancient(with Julia Annas, 2002), as well as providing a new translation of Aristotle's Nicomachean Ethics to accompany a philosophical commentary by Sarah Broadie (2002).