When it comes to theories of human consciousness, there are basically two schools of thought.
The first says that the hard questions of consciousness have been answered: that what we have historically thought of as consciousness doesn’t exist because we can trace various components of personality and memory to brain tissue, and that all that’s left is to explicate how all of this works. This point of view is generally called reductive physicalism.
The second school of thought says that we haven’t answered the hard questions of consciousness—that there’s something else to it all that we haven’t found yet. Into this general category fall the non-reductive physicalists, the interactionists, the panpsychists, and so on, all trying to figure out what the reductive physicalist model of consciousness is missing and where we might find it.
John Searle, a philosopher who has spent over a half-century studying consciousness and the mind-body problem, describes it all brilliantly:
Enter this month’s New Scientist cover story, written by MIT physicist Max Tegmark. Citing the quantum observer effect as reason enough to believe that consciousness is a unique condition, Tegmark argues that consciousness is, in fact, a state of matter—that consciousness is, in his words, “the way information feels when processed in certain complex ways.” He aligns himself with Giulio Tononi’s integrated-information theory, which is (like most theories of its kind) both valid and impossible to test.