François Ascher, an urban theorist and sociologist, was a professor at the French Institute of Urbanism and President of the Scientific Board of the City on the Move Institute, and organized the colloquium on which this book is based. He died in 2009. Jacques Lévy is Professor of Geography at the Ecole Polytechnique Fédérale de Lausanne. He is the author of, among other works, the Dictionnaire de la géographie et de l’espace des societies with Michel Lussault.