ogy (Gray 1995; Velmans 1995a). In short, while it is likely that consciousness will eventually be found to be associated with given forms of processing, it looks increasingly likely that consciousness cannot be reduced to such processing. Or, to put matters another way, "first-person perspective facts" cannot be fully reduced to "third-person perspective facts" (cf Goldman 1993; Velmans 1991a,b, 1993a). In his recent "keynote" article (this issue), Chalmers (1995) comes to the same conclusion. But if consciousness cannot be reduced to a state or function of the brain, how might one fill the explanatory gap left by dualism? Logically, it might be possible to reduce matter to forms of existence in the mind, for example to argue along with Berkeley (1710) that material events only exist in so far as they are perceived to exist (idealism). Idealism has its modern defenders, for example in some interpretations of the observer effect in quantum mechanics (the view that the Shrodinger wave equation only collapses into an actuality once an observation is made). In the macroworld it may also be true that the world as-perceived only exists if there are perceivers (Velmans 1990). However, as a general theory of the ontology of macroevents this position has its own well-known problems. It might be that the material world cannot have an appearance without perceivers, but it seems counterintuitive that its very existence is similarly vulnerable. Closing one's eyes, for example, does not seem to be enough to make unpleasant events go away....
