In preparing this book, I have incurred many debts. Lynne Broughton, as throughout our married life, has been tireless in providing support of all kinds. Colin Austin, Jacques Brunschwig, Antonio Carlini, Christopher Gill, Pamela Huby and David Johnson have generously given offprints, or access to work in progress. Paul Cartledge, James Clackson, Susan Daruvala, Roger Dawe, Coulter George, Eric Handley, Sarah Hawkins, Neil Hopkinson, Geoff Horrocks, Geoffrey Lloyd, Malcolm Schofield, David Sedley and Gisela Striker have each been kind enough to let me pick their brains about various points of detail. John Palmer very helpfully alerted me to comparisons and contrasts between Plato's Alcibiades and Xenophon's Euthydemus; Myles Burnyeat no less helpfully alerted me to the significance of Peparethus. As editors of this series, Pat Easterling, Richard Hunter and Ted Kenney have given much encouragement and advice. Doug Hutchinson, Robert Wardy and Emma Woolerton generously scrutinised drafts of the entire commentary. And my debt to members of seminars in Cambridge and Leeds is no less real for being acknowledged only in this general fashion. Thanks to all these people, this book has been so much improved that I suspect it would have been perfect had I always followed their advice; certainly none of them can be blamed for any faults that remain.