Lately I have been thinking about Frank Jackson's thought experiment, variously called Mary the super-scientist or Mary's Room . I have even preached about it a couple of times, and a recording of the last time, at St. Matthew's Dunedin, is here . The thought experiment goes something like this: Mary is the world's most brilliant neurophysiologist. her specialty is the perception of colour. She knows absolutely everything there is to know about colour: how the retina is affected by light, how the brain processes the information etc. When it comes to colour perception, there is not one fact that it is possible to know that she does not know. By a huge irony, however, Mary is herself only able to see monochromatically. That is, though she knows all it is possible to know about colour, she has never experienced colour vision herself. One day, due to some freak happenstance, her monochromatism is ended, and she is able to see colours. The question is: does she know a...