 The Hard Problem can be specified in terms of generic and specific consciousness (Chalmers 1996). In both cases, Chalmers argues that there is an inherent limitation to empirical explanations of phenomenal consciousness in that empirical explanations will be fundamentally either structural or functional, yet phenomenal consciousness is not reducible to either. This means that there will be something that is left out in empirical explanations of consciousness, a missing ingredient (see also the explanatory gap [Levine 1983]).