William Robert Webster
Chalmers (The Conscious Mind, Oxford Unversity Press, Oxford 1996) has argued for a form of property dualism on the basis of the concept of a zombie (which is physically identical to normals), and the concept of the inverted spectrum. He asserts that these concepts show that the facts about consciousness, such as experience or qualia, are really further facts about our world, over and above the physical facts. He claims that they are the hard part of the mind-body issue. He also claims that consciousness is a fundamental feature of the world like mass, charge, etc.
He says that consciousness does not logically supervene on the physical and all current attempts to assert an identity between consciousness and the physical are just as non-reductive as his dualism. They are simply correlations and are part of the problem of the explanatory gap. In this paper, three examples of strong identities between a sensation or a quale and a physiological process are presented, which overcome these problems. They explain the identity in an a priori manner and they show that consciousness or sensations (Q) logically supervene on the physical (P), in that it is logically impossible to have P and not to have Q. In each case, the sensation was predicted and entailed by the physical. The inverted spectrum problem for consciousness is overcome and explained by a striking asymmetry in colour space. It is concluded that as some physical properties realize some sensations or qualia that human zombies are not metaphysically possible and the explanatory gap is bridged in these cases. Thus, the hard problem is overcome in these instances.