Chalmers dismisses the possibility that we could possibly expand our knowledge of physics in such a way that we would see that consciousness does logically supervene on the physical. Ultimately, I believe that materialism will be justified by a better understanding of physics. However, materialism's success will not rest on the logical supervenience of consciousness. We can at least grant Chalmers that it would require a very different sort of physical theory from the one we presently have to physically explain consciousness. (3) If consciousness does not logically supervene on the physical, then one cannot reduce facts about consciousness to physical facts, and hence one cannot explain the occurrence of consciousness just by appeal to the physical facts. This premise depends upon what a reductive explanation of consciousness would consist of. Chalmers argues that given only the physical facts about a person, there is no way you could ever infer the existence of consciousness in that person because of the logical possibility of zombies. Since zombies are logically possible, and because a zombie and its human counterpart would be physically identical, just knowing all of the physical information about a person is not enough to infer the existence of consciousness. Therefore, one cannot explain consciousness physically. Chalmers seems to equate explanation with a bottom-up process of illustrating how low-level properties produce high-level properties. The notion of what constitutes a reduction is very important in the debate between physicalists and dualists, and different notions imply different things about the prospects of reducing consciousness to physical terms. In one sense, some fact is reducible to other facts when the lower facts explain the higher fact (in the sense of "explain" mentioned above). This is how Chalmers uses the term reduction. According to this conception, it is impossible to reduce consciousness to physical stru...
