David Rosand is Meyer Schapiro Professor of Art History at Columbia University. He is the author of several books, including "The Meaning of the Mark: Leonardo and Titian"; "Painting in Sixteenth-Century Venice: Titian, Veronese, Tintoretto"; "Robert Motherwell on Paper: Drawings, Prints, Collages"; "Myths of Venice: The Figuration of a State"; and "Drawing Acts: Studies in Graphic Expression and Representation,"