<P> Many philosophers have argued that consciousness is a unitary concept that is understood intuitively by the majority of people in spite of the difficulty in defining it . Others, though, have argued that the level of disagreement about the meaning of the word indicates that it either means different things to different people (for instance, the objective versus subjective aspects of consciousness), or else is an umbrella term encompassing a variety of distinct meanings with no simple element in common . </P> <P> Ned Block proposed a distinction between two types of consciousness that he called phenomenal (P - consciousness) and access (A-consciousness). P - consciousness, according to Block, is simply raw experience: it is moving, colored forms, sounds, sensations, emotions and feelings with our bodies' and responses at the center . These experiences, considered independently of any impact on behavior, are called qualia . A-consciousness, on the other hand, is the phenomenon whereby information in our minds is accessible for verbal report, reasoning, and the control of behavior . So, when we perceive, information about what we perceive is access conscious; when we introspect, information about our thoughts is access conscious; when we remember, information about the past is access conscious, and so on . Although some philosophers, such as Daniel Dennett, have disputed the validity of this distinction, others have broadly accepted it . David Chalmers has argued that A-consciousness can in principle be understood in mechanistic terms, but that understanding P - consciousness is much more challenging: he calls this the hard problem of consciousness . </P> <P> Some philosophers believe that Block's two types of consciousness are not the end of the story . William Lycan, for example, argued in his book Consciousness and Experience that at least eight clearly distinct types of consciousness can be identified (organism consciousness; control consciousness; consciousness of; state / event consciousness; reportability; introspective consciousness; subjective consciousness; self - consciousness)--and that even this list omits several more obscure forms . </P> <P> There is also debate over whether or not a-consciousness and p - consciousness always co-exist or if they can exist separately . Although p - consciousness without a-consciousness is more widely accepted, there have been some hypothetical examples of A without P. Block for instance suggests the case of a "zombie" that is computationally identical to a person but without any subjectivity . However, he remains somewhat skeptical concluding "I don't know whether there are any actual cases of A-consciousness without P - consciousness, but I hope I have illustrated their conceptual possibility ." </P>

Where does the conscious awareness of sound begin