iousness might be metaphysically identical to physical phenomena even if it is conceivable that consciousness is not a physical phenomenon (as the logical possibility of zombies shows). This response explains the contingency Chalmers points out, while at the same time avoiding the conclusion that consciousness cannot be physically instantiated. Materialist theories will hold that the identity of consciousness and physical processes is similar to the identity of water and H2O. It is logically possible (i.e., conceivable) that water might have been XYZ (God could have made the world in that way); however, water just is H2O in our world; therefore, in all possible worlds, the term 'water' refers to H2O. Similarly, materialists would argue that although it is logically possible for a being physically identical to you or me to exist without being conscious, in our world consciousness just is physically instantiated. Therefore, in all possible worlds, this same physical phenomena should be called "consciousness." A zombie world is logically possible, though metaphysically impossible according to this revised version of materialism. Presumably, materialists who fall back on the notion of metaphysical identity believe that someday a conceptual revolution in physics and psychology will allow us to physically explain consciousness. Only after we possess a true and complete theory of nature (i.e., of physics) will a physical reduction of consciousness be possible; however, because we currently lack such a theory, Chalmers' argument from the conceivability of zombies does not refute materialism. We cannot be expected to understand the connection between consciousness and physical phenomena a priori, but the limits of our conceptual powers do not impose limits on how consciousness is instantiated. A common analogy is that of explaining the phenomenon of life. Hundreds of years ago it would have been inconceivable that a complex phenomenon such as li...
