Daniel Dennett's philosophical method in Consciousness Explained could be described as the Jericho method. He believes that if he marches around a philosophical problem often enough, proclaiming what are, plausibly, relevant scientific truths, the problem will dissolve before our eyes. In so far as he is inviting us to adopt a new way of looking at things, this method is quite appropriate. It does mean, however, that moments of direct philosophical argument are rare, and are to be cherished when found. The knowledge argument for the existence of qualia is one strategy which condenses the issue of physicalism and consciousness sufficiently precisely to force Dennett to face his opponent directly. When he does face this argument head on his response is unconvincing. This matters, because if he cannot cope with the knowledge argument then his more indirect ways of 'deconstructing' our notion of consciousness must be futile. Dennett considers the argument in Jackson's famous 'what Mary didn't know' form. Mary knows everything that a completed physical science could tell her about the physical processes involved in visual perception, including colour perception, but has never been allowed to perceive colour, only black and white. If she is finally allowed to perceive colours she will discover something she previously did not know, namely what colour and seeing colour are like. As she previously knew everything physical and relevant, the new knowledge must relate to something non-physical. Dennett's response is that if we take seriously the premiss that Mary knew everything there was to know about the physical processes, then the conclusion that she would gain new knowledge on being allowed to see colour does not follow. He continues the story as follows.