|Discussions of abstraction lead us to a philosophical problem, the mind body split. With the late 20th century interest in artificial intelligence, the brain and its function has become a matter of technological interest. Rene Descartes' dualism kick-started the mind/body problem 350 years ago. More recently, philosophers and neurologists have come to believe that consciousness is simply a material function of the squiggly slab of meat cradled in our skulls.
The book Toward a Science of Consciousness, by MIT Press, explores the convergence of quantum theory, neurology, and philosophy of mind. Several useful subjects are covered, such as the "explanatory gap"--the generally accepted notion that conscious experience can never be completely understood through knowledge of physiology--and "qualia"--the notion of intrinsic sense perceptions, such as the redness of red. The strangest concept discussed is "backwards time referral," which suggests that the brain employs the spooky action of quantum mechanics to actually send signals backwards through time.
During neuroscience experiments in the 1970s, patients were poked on the arm, and asked to note the exact moment when they became conscious of the stimulus. Brain activity was recorded. Next, the patients were poked directly on the area of the brain that had previously been stimulated. Astonishingly, the brain pokes were "noticed" significantly later than the arm pokes were. This suggested that the brain was receiving information after it was first perceived, but sending that information back in time to coincide with the moment of stimulus. Too trippy? Yes, it is, and of course a lot of people have perfectly non-spooky ways of explaining this data.
Daniel C. Dennett, a philosopher of consciousness, chalks up the phenomenon to a "temporal smear." He explains that there is no fixed point when external events are registered in the mind, but rather consciousness is a process; a multi-track continuum. In his book, Consciousness Explained, he presents a fluid model of consciousness, in which, "at any point in time there are multiple drafts of narrative fragments at various stages of editing in various places in the brain."
Dennett also chides us (and his colleagues) for clinging to Cartesian Dualism; the old idea that consciousness resides on some separate special metaphysical plane, distinct from lumpen matter. While most people nowadays agree that the mind is a physical process (adhering to the theory of materialism), many of us still cling to a model of the Cartesian Theatre, in which our perceptions play like film on a screen, a "functional place of some sort where the items of phenomenology are projected." But according to Dennett, "there is no such theatre, there is no such audience." This would still require an entity separate from the system. Rather, he holds that the continuous, multiple narratives running in our brains are all there is to consciousness. Dennett's extreme materialism is very influential, though many people feel he goes too far, especially in his 1998 article "Quining Qualia," published in Consciousness in Modern Science, in which he denies the existence of perceptual phenomena. Nonetheless, by strictly adhering to physiology, Dennett confronts us with the idea that consciousness does not give us access to a definable external reality.
As with quantum physics (see Schroedinger's cat), the role of the observer carries a great deal of weight.