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← Mary's Room: A philosophical thought experiment - Eleanor Nelsen

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Showing Revision 4 created 03/17/2017 by Jessica Ruby.

  1. Imagine a brilliant neuroscientist
    named Mary.
  2. Mary lives in a black and white room,
  3. she only reads black and white books,
  4. and her screens only display
    black and white.
  5. But even though she has never seen color,
    Mary is an expert in color vision
  6. and knows everything ever discovered
    about its physics and biology.
  7. She knows how different
    wavelengths of light
  8. stimulate three types of cone cells
    in the retina,
  9. and she knows how electrical signals
  10. travel down the optic nerve
    into the brain.
  11. There, they create patterns
    of neural activity
  12. that correspond to the millions
    of colors most humans can distinguish.
  13. Now imagine that one day,
  14. Mary's black and white screen
  15. and an apple appears in color.
  16. For the first time,
  17. she can experience something
    that she's known about for years.
  18. Does she learn anything new?
  19. Is there anything about perceiving color
    that wasn't captured in all her knowledge?
  20. Philosopher Frank Jackson proposed
    this thought experiment,
  21. called Mary's room, in 1982.
  22. He argued that if Mary already knew
    all the physical facts about color vision,
  23. and experiencing color still teaches
    her something new,
  24. then mental states, like color perception,
  25. can't be completely described
    by physical facts.
  26. The Mary's room thought experiment
  27. describes what philosophers call
    the knowledge argument,
  28. that there are non-physical properties
    and knowledge
  29. which can only be discovered
    through conscious experience.
  30. The knowledge argument contradicts
    the theory of physicalism,
  31. which says that everything,
    including mental states,
  32. has a physical explanation.
  33. To most people hearing Mary's story,
  34. it seems intuitively obvious
    that actually seeing color
  35. will be totally different
    than learning about it.
  36. Therefore, there must be some quality
    of color vision
  37. that transcends its physical description.
  38. The knowledge argument isn't just
    about color vision.
  39. Mary's room uses color vision
    to represent conscious experience.
  40. If physical science can't entirely
    explain color vision,
  41. then maybe it can't entirely explain
    other conscious experiences either.
  42. For instance, we could know every
    physical detail
  43. about the structure and function
    of someone else's brain,
  44. but still not understand
    what it feels like to be that person.
  45. These ineffable experiences
    have properties called qualia,
  46. subjective qualities that you can't
    accurately describe or measure.
  47. Qualia are unique to the person
    experiencing them,
  48. like having an itch,
  49. being in love,
  50. or feeling bored.
  51. Physical facts can't completely explain
    mental states like this.
  52. Philosophers interested
    in artificial intelligence
  53. have used the knowledge argument
  54. to theorize that recreating
    a physical state
  55. won't necessarily recreate
    a corresponding mental state.
  56. In other words,
  57. building a computer which mimicked
    the function of every single neuron
  58. of the human brain
  59. won't necessarily create a conscious
    computerized brain.
  60. Not all philosophers agree that
    the Mary's room experiment is useful.
  61. Some argue that her extensive knowledge
    of color vision
  62. would have allowed her to create
    the same mental state
  63. produced by actually seeing the color.
  64. The screen malfunction wouldn't
    show her anything new.
  65. Others say that her knowledge
    was never complete in the first place
  66. because it was based only
    on those physical facts
  67. that can be conveyed in words.
  68. Years after he proposed it,
  69. Jackson actually reversed his own
    stance on his thought experiment.
  70. He decided that even
    Mary's experience of seeing red
  71. still does correspond to a measurable
    physical event in the brain,
  72. not unknowable qualia beyond
    physical explanation.
  73. But there still isn't a definitive answer
  74. to the question of whether Mary would
    learn anything new
  75. when she sees the apple.
  76. Could it be that there are fundamental
    limits to what we can know
  77. about something we can't experience?
  78. And would this mean there are certain
    aspects of the universe
  79. that lie permanently beyond
    our comprehension?
  80. Or will science and philosophy allow
    us to overcome our mind's limitations?