Roberto Casati is research director at the Centre National de la Recherche Scientifique (CNRS), Paris. He is the author of The Shadow Cluband (with Achille Varzi) Parts and Places: The Structures of Spatial Representationand Holes and Other Superficialities.Achille Varzi is professor of philosophy at Columbia University. In addition to the books coauthored with Casati, he is the author of several volumes, including An Essay in Universal Semanticsand Theory and Problems of Logic.