Peter Ludlow, Professor of Philosophy at the University of Toronto, is the author of Semantics, Tense, and Time: An Essay in the Metaphysics of Natural Language (MIT Press, 1999), among other books, and the editor of Crypto Anarchy, Cyberstates, and Pirate Utopias (MIT Press, 2001) and High Noon on the Electronic Frontier (MIT Press, 1996).