Some philosophers insist that the difference between the old and the new concepts in this case is such that there must be a difference in the world between the properties these concepts stand for or denote (Jackson 1993, Chalmers 1996). Some of these properties Mary knew in her cell; others she becomes cognizant of only upon her release. This is necessary for Mary to make a real discovery: she must come to associate with the experience of red new qualities she did not associate with it in her ro