Chalmers' Hard Problem and its solution:

2. Here are a few statements or definitions of Chalmers hard problem by leading thinkers:

• Here is Chalmers' (1995) statement of the hard problem:
  (For further study of the nature of the hard problem, please access Chalmers' 1994 Tucson I paper.)

  "Researchers use the word 'consciousness' in many different ways. To clarify the issues, we first have to separate the problems that are often clustered together under the name. For this purpose, I find it useful to distinguish between the 'easy problems' of consciousness and the 'hard problem' of consciousness. The easy problems are by no means trivial - they are actually as challenging as most in psychology and biology - but it is with the hard problem that the central mystery lies.

  "The easy problems of consciousness include the following: How can a human subject discriminate sensory stimuli and react to them appropriately? How does the brain integrate information from many different sources and use this information to control behavior? How is it that subjects can verbalize their internal states? Although all these questions are associated with consciousness, they all concern the objective mechanisms of the cognitive system. Consequently, we have every reason to expect that continued work in cognitive psychology and neuroscience will answer them.

  "The hard problem, in contrast, is the question of how physical processes in the brain give rise to subjective experience. This puzzle involves the inner aspect of thought and perception: the way things feel for the subject. When we see, for example, we experience visual sensations, such as that of vivid blue. Or think of the ineffable sound of a distant oboe, the agony of an intense pain, the sparkle of happiness or the meditative quality of a moment lost in thought. All are part of what I am calling consciousness. It is these phenomena that pose the real mystery of the mind."

• Here is Francis Crick and Christof Koch's insights on the solution to Chalmers' hard problem:
  (The hard problem was discussed in the December 1995 issue of Scientific American. The excerpt by Crick and Koch, below, was obtained from that article.)

  "We believe that at the moment the best approach to the problem of explaining consciousness is to concentrate on finding what is known as the neural correlates of consciousness - the processes in the brain that are most directly responsible for consciousness. By locating the neurons in the cerebral cortex that correlate best with consciousness, and figuring out how they link to neurons elsewhere in the brain, we may come across key insights into what David J. Chalmers calls the hard problem: a full accounting of the manner in which subjective experience arises from these cerebral processes."

• Here is John Searle's insights on the problem of consciousness:
  [Searle JR. 2000. Consciousness. Annual Review of Neuroscience 23:558-559.]

  "What exactly is the neurobiological problem of consciousness? The problem, in its crudest terms, is this: How exactly do brain processes cause conscious states and how exactly are those states realized in brain structures? So stated, this problem naturally breaks down into a number of smaller but still large problems: What exactly are the neurobiological correlates of conscious states (NCC), and which of those correlates are actually responsible for the production of consciousness? What are the principles according to which biological phenomena such as neural firings can bring about subjective states of sentience or awareness? How do those principles relate to the already well understood principles of biology? Can we explain consciousness with the existing theoretical apparatus or do we need some revolutionary new theoretical concepts to explain it? Is consciousness localized in certain regions of the brain or is it a global phenomenon? If it is confined to certain regions, which ones? Is it correlated with specific anatomical features, such as specific types of neurons, or is it to be explained functionally with a variety of anatomical correlates? What is the right level for explaining consciousness? Is it the level of neurons and synapses, as most researcher seem to think, or do we have to go to higher functional levels such as neuronal maps (Edelman 1989, 1992), or whole clouds of neurons (Freeman 1995), or are all of these levels much too high and we have to go below the level of neurons and synapses to the level of the microtubules (Penrose 1994; Hameroff 1998a, b)? Or do we have to think much more globally in terms of Fourier transforms and holography (Pribram 1976, 1991, 1999)?

  "As stated, this cluster of problems sounds similar to any other such set of problems in biology or in the sciences in general. It sounds like the problem concerning microorganisms: How, exactly, do they cause disease symptoms and how are those symptoms manifested in patients? Or the problem in genetics: By what mechanisms exactly does the genetic structure of the zygote produce the phenotypical traits of the mature organism? In the end I think that it is the right way to think of the problem of consciousness - it is a biological problem like any other, because consciousness is a biological phenomenon in exactly the same sense as digestion, growth, or photosynthesis."