Professor Frank Jackson (Australian National University) came up with one of the most influential arguments against materialism about consciousness, a version of the 'knowledge argument', involving the story of Black and White Mary. Ironically, Jackson later recanted and is now a committed materialist. Keith and Philip will discuss with Frank the knowledge argument, why he changed his mind, and what he thinks about consciousness now. (Philip secretly hopes to bring Frank back to the fold of anti-materialists, but it's a long shot).