Keith Hartley is deputy director at the Scottish National Gallery of Modern Art, Edinburgh. He co-organised the ground-breaking exhibition The Romantic Spirit in German Art and has written widely on modern and contemporary art, including Ron Mueck, Ed Ruscha and Duane Hanson.Images used: (c)Licensed by The Andy Warhol Foundation for the Visual Arts, Inc./ARS, New York, and DACS, London, 2007