One of the enduring problems in the philosophy of mind is the nature of consciousness. Exactly what it is and where it comes from has baffled philosophers and neuroscientists alike. Philosopher David Chalmers, one of the leading thinkers in this field, has a good paper on the matter in which he lays out the arguments against the materialist view that consciousness is reducible to material entities like atoms and chemical reactions. He begins the paper with this:
Consciousness fits uneasily into our conception of the natural world. On the most common conception of nature, the natural world is the physical world. But on the most common conception of consciousness, it is not easy to see how it could be part of the physical world. So it seems that to find a place for consciousness within the natural order, we must either revise our conception of consciousness, or revise our conception of nature.
The word 'consciousness' is used in many different ways. It is sometimes used for the ability to discriminate stimuli, or to report information, or to monitor internal states, or to control behavior. We can think of these phenomena as posing the "easy problems" of consciousness. These are important phenomena, and there is much that is not understood about them, but the problems of explaining them have the character of puzzles rather than mysteries. There seems to be no deep problem in principle with the idea that a physical system could be "conscious" in these senses, and there is no obvious obstacle to an eventual explanation of these phenomena in neurobiological or computational terms.
The hard problem of consciousness is the problem of experience. Humans beings have subjective experience: there is something it is like to be them. We can say that a being is conscious in this sense - or is phenomenally conscious, as it is sometimes put - when there is something it is like to be that being. A mental state is conscious when there is something it is like to be in that state. Conscious states include states of perceptual experience, bodily sensation, mental imagery, emotional experience, occurrent thought, and more. There is something it is like to see a vivid green, to feel a sharp pain, to visualize the Eiffel tower, to feel a deep regret, and to think that one is late. Each of these states has a phenomenal character, with phenomenal properties (or qualia) characterizing what it is like to be in the state.
There is no question that experience is closely associated with physical processes in systems such as brains. It seems that physical processes give rise to experience, at least in the sense that producing a physical system (such as a brain) with the right physical properties inevitably yields corresponding states of experience. But how and why do physical processes give rise to experience? Why do not these processes take place "in the dark," without any accompanying states of experience? This is the central mystery of consciousness.
What makes the easy problems easy? For these problems, the task is to explain certain behavioral or cognitive functions: that is, to explain how some causal role is played in the cognitive system, ultimately in the production of behavior. To explain the performance of such a function, one need only specify a mechanism that plays the relevant role. And there is good reason to believe that neural or computational mechanisms can play those roles.
What makes the hard problem hard? Here, the task is not to explain behavioral and cognitive functions: even once one has an explanation of all the relevant functions in the vicinity of consciousness - discrimination, integration, access, report, control - there may still remain a further question: why is the performance of these functions accompanied by experience? Because of this, the hard problem seems to be a different sort of problem, requiring a different sort of solution.
A solution to the hard problem would involve an account of the relation between physical processes and consciousness, explaining on the basis of natural principles how and why it is that physical processes are associated with states of experience. A reductive explanation of consciousness will explain this wholly on the basis of physical principles that do not themselves make any appeal to consciousness.[*] A materialist (or physicalist) solution will be a solution on which consciousness is itself seen as a physical process. A nonmaterialist (or nonphysicalist) solution will be a solution on which consciousness is seen as nonphysical (even if closely associated with physical processes). A nonreductive solution will be one on which consciousness (or principles involving consciousness) is admitted as a basic part of the explanation.
It is natural to hope that there will be a materialist solution to the hard problem and a reductive explanation of consciousness, just as there have been reductive explanations of many other phenomena in many other domains. But consciousness seems to resist materialist explanation in a way that other phenomena do not. This resistance can be encapsulated in three related arguments against materialism, summarized in what follows.
Go to the link to read the rest of this interesting paper.
One of the important things to note about it is that if consciousness is not reducible to physical entities then it becomes more plausible that it has a non-physical cause, but non-physical causes would be beyond the scope of science and indeed could be considered extra-natural or super-natural. Chalmers himself doesn't go this far but much of the argumentation in his paper lends support to this hypothesis.
