Renée van de Vall, PhD (1992) Philosophy, Amsterdam University, is associate professor of media culture at the University of Maastricht. She has published on philosophy of art, spectatorship and contemporary visual culture, including At the Edges of Vision (2008). Robert Zwijnenberg, PhD (1995) Philosophy, Amsterdam University, is professor of art history at Leiden University. He publishes on philosophy of art, and on the relation between the arts and sciences, including The Writings and Drawings of Leonardo da Vinci (1999).