There is a particular philosophical position on consciousness that can roughly be summarized as the following:
Since the early 1970s, philosophers, scientists, and intellectuals of all stripes have come to slowly learn to never take the above position. The above stance is what I am going to call the "Third Rail of Consciousness". Writers and debators have learned through trials and tribulations to never take the position, because they know that the philosophers will seize on it, and paint the claimant into a corner."Consciousness is a turing-computable function being performed by the biomechanics of the brain."
To a person who has already adopted various strict forms of reductionist materalism (for example Eliminative Materialism), the above claim appears to be reasonable, even self-evident. On deeper inspection, it turns out to be baseless, even hopelessly reaching. To see how a philosopher paints the reductionist into a corner, we can imagine a fictitious conversation between a vanilla materialist, and a philosopher.
vanilla materialist: "I hereby claim consciousness is a function of the brain."
Philosopher: "If consciousness is a function, what does that function do?"
vanilla materialist: "I hereby claim consciousness is a function of the brain!"
Philosopher: "Alright, that's fine. So what does the function do?"
vanilla materialist: "I hereby claim consciousness is a function of the brain!"
Philosopher: "Yes, I understand. Now what does the function perform exactly?"
vanilla materialist: "I hereby claim consciousness is a function of the brain!"
Philosopher: "And what is the use of this function?"
vanilla materialist: "I hereby claim consciousness is a function of the brain!"
Philosopher: "And what function are we talking?"
vanilla materialist: "I hereby claim consciousness is a function of the brain!"
Philosopher: "WHAT DOES IT DO?"
Even a novice philosopher can paint the most elite debater into a corner by simply sticking to two questions and not letting up. Namely,
1. What function does consciousness perform?
2. and Why did it evolve?
Neuroscientists and intellectuals of the last 40 years are now fully aware that these probing questions are always lurking around the corner. And so taking a position that consciousness is just brain function is something they have learned to completely avoid. In doing so, a number of more subtle approaches have been adopted by them. Before elaborating on these more subtle approaches, we should review the historical backdrop upon which all this started.
Thomas Nagel and bats.
Nagel, argued in a 1974 article that there is something that it is like to be a humnan. The title of his article was "What Is It Like to Be a Bat?". In it he argued that there is something that it is like to be a bat. This set the stage for what was to come. Nagel's position was not that of cartesian dualism, or humonculi in theatres, but something entirely new. In coming decades, Nagel's ambiguous ideas were going to be refined into a more rigorous system.
Joseph Levine and gaps.
In a 1983 paper, Levine coined the term "explanatory gap". In short, a scientific account of human existence is insufficient to explain the existence of internal, first-person experiences. Again, this was not a re-hashing of any argument about mental phenomenon existing independently of physical phenomena in biological brains. Instead it was simply a statement of fact: that modern science lacked an explanation for mental states in terms of physical states. To summarize -- science contains an explanatory gap when it comes to consciousness.
David Chalmers and zombies.
Levine's philosophy sparked a heated debate about whether the explanatory gap was really just a lack of technological progress in neuorscience. We could ask the question: Will advanced neuroscience of the future simply gain enough knowledge on the brain that the explanatory gap will be bridged? Chalmers took this argument to the bank -- and actually answered this question in the negative! Chalmers claimed that even if you had a complete, highly-detailed, blueprint of the human brain, there is still nothing about that blueprint that would entail logically that the brain was having internal experiences. Whereas Levine had shown an explanatory gap, Chalmers had posited a gap in reasoning itself. Chalmers' argument was so subtle, yet so powerful, that many could not understand it completely. In order to help the less clever, Chalmers came up with a cartoonish mental exercise to help elucidate his argument. Given that a blueprint of the brain only ever shows mechanisms of chemicals and cells, one could plausibly account for all human behavior in terms of unconscious zombies. Like robots, the zombies map input to output; they map perception to behavior; but do not ever feel anything. One has to imagine androids who look and act exactly as we do, but don't have any internal experience.
Dual Aspect Theory
What Chalmers had shown to us seems impossible to argue against. A mechanistic blueprint of the brain simply does not get you to consciousness taking place therein -- and showed this is not entailed because scientific materialism cannot rule out zombies. (i.e. entailment would require ruling out functional zombies. You can't rule them out. You don't get the entailment.) What was spearheaded by Thomas Nagel in the 1970s is now fully formed into a system called "Dual Aspect Theory" by contemporary philosophers in 2012CE. I will not elaborate further on Dual Aspect, but just point the reader to investigate on his or her own time.
We can come full circle now and see how literate intellectuals have responded to all this. In every case, we will see them adeptly avoiding the Third Rail. (As you read the following sections below, keep your eyes peeled and notice that, at no point, do any of these people claim consciousness is a function that does something.)
Giulio Tononi and fundamental properties.
Dr. Tononi is a researcher of sleep and consciousness at the University of Wisconsin at Madison. He is a neuroscientist. Tononi gave a long lecture on a theory of consciousness called Phi Integration. After finishing the lecture, he was accosted immediately by philosophers in the audience. They wanted to know what function consciousness performs and why it had evolved in humans ... (no suprise there!).
Tononi shot back an answer that demonstrated his intellectual dexterity. He declared that consciousness did not evolve at all. And instead described consciousness as, (and I quote), "... a fundamental property like mass or charge."
Tononi was positioning himself subtly here. His comparison of consciousness to mass and charge meant to highlight that even in the "hard" science of physics, scientists do not know what charge is. Physicists accept that charge exists, without further explanation. Tononi was saying that consciousness is simply a fundamental property of systems of connected units. An "explanation" of its function is then not required since the question doesn't make sense. It would be like asking why a circle contains roundness.
Gerald Edelman and epi-phenomena.
Edelman is a neuroscientist, and a winner of the Nobel Prize in immunology. He has authored six books on the subject of consciousness. His books read like functional neuroanatomy, and their focus is on the Neuronal Correlates of Consciousness. The books are intended for a general reading audience. Edelman's work does indeed contain references to philosophers, but his position is directly contrary to Chalmers'. Edelman's system segregates C states from C' states (pronounced "C-prime" states). C states are activity of real neurons in brains that can be measured emperically in a lab, (i.e. the neuronal correlates). C' states are the conscious states experienced internally by the person. Using very strong arguments from neuroanatomy and contemporary neuroscience, Edelman posits that the C' states are indeed entailed by the C states.
However, in public and even on camera, Edelman has admitted that C' states are not causal. To summarize Edelman's philosophy in a single sentence: Consciousness is not causal. He understands that this drives philosophers crazy, because it is a form of epiphenomenalism. Consciousness exists in a strange way, "on top" of the dynamics of physical matter. In other words, consciousness comes along for the ride, but itself does nothing and indeed can't do anything. Consciousness is there. Get used to it. But don't expect anything of it.
Daniel Dennett and unwitting fictions.
Daniel Dennett is an american philosopher who lives in New England. Dennett's work spans numerous fields of study, from biology, to psychology, philosophy of science, and consciousness. For our purposes here, we will focus very narrowly on a single book authored by Dennett titled "Consciousness Explained" , which was published in 1991.
Dennett's book appears superficially to be written to a general audience. Personally, I disagree. In my opinion, 'Consciousness Explained' constitutes a direct frontal attack on Nagel and Levine. Dennett drives his attack directly to the premises that started this whole modern discourse on consciousness.
Dennett's arguments always loose something crucial in a summary, so the following summary will be a course overview.
Let's return to what it is like to be a bat. This was what started the whole thing to begin with in 1974. Dennett points out that explanatory gaps abound in modern life when it comes to science, and indeed we can manufacture explanatory gaps at will. For example take the plot of the movie Star Wars. I could demand of you that you produce a scientific explanation for the plotline of Star Wars. I could then parade around with your inability to provide one as an EXPLANATORY GAP. ("You cannot explain Star Wars using objective scientific accounts. That's an explanatory gap! Check mate, scientists!") Fortunately, we can tell each other that the existence of this explanatory gap is not a problem -- because Star Wars is a work of fiction. We say it is fiction, and the conversation is safisfactorily finished. Any other book or television show suffices as an example, as long as it is a work of fiction.
Dennett shows that human beings often converse in a normative manner and we can take an example of two human beings having a "normative" conversation on a subway. One persons asks another "What is it like to jet ski?" The second person produces the expected normative response; something like, "It's exciting because you go fast. You feel like you are out of control but you still maintain the ski machine underneath you."
When asking someone "What is like to do X?" the answer that comes out of their mouth is, (what Dennett calls), an unwitting fiction. Being a fiction, science is no more obligated to explain it than it is obligated to explain the plotline of Star Wars, Twilight, or any other fictitious story.
Dennett relies on the fact the primary evidence of internal experience is that it is reported on by the person having them. There is certainly no emperically-measured neurological data showing that internal experience is happening. When Nagel said that there is something that it is like to be an X, he was merely pointing out that there are entities in our world which produce verbalizations of (something which) they believe to be internal experience. Going in circles trying to explain what people believe is a scientific foul. (Beliefs of people are inexorably intertwined with culture, religion, upbringing, level of education, language itself, et cetera.)
Dennett's book from 1991 ended up being very influential on an entire generation of neuroscientists. Gerald Edelman's philosophy is, in a subtle way, a re-hashing of the foundation layed down by Dennett. Dennett can appropriately be considered the anti-Nagel.
The spearhead of the Dennett approach contains, on one hand, a denial of the "problems" of consciousness being problems at all -- and on the second hand, an adept caution to never touch the Third Rail.