David W. Lightfoot is Dean of the Graduate School at Georgetown University. Until recently he was Professor of Linguistics and Associate Director of the Neural and Cognitive Science Program at the University of Maryland with a joint appointment as Professor of Linguistics at the University of Reading. His books include Principles of Diachronic Syntax (CUP 1979), The Language Lottery: Toward a Biology of Grammars (MIT Press, 1982), How to Set Parameters: Arguments from Language Change (MIT Press, 1991), and The Development of Language: Acquisition, Change, and Evolution (Blackwell, 1999).