Five Thought Experiments on the Nature of Consciousness

1
Five Thought Experiments on the Nature of
Consciousness
2
Alien Personhood
Lets define a person as a being that is
self-conscious. Now imagine that you are a
space explorer who has just landed on another
planet. How would you decide whether or not to
classify members of any alien species you
encounter as persons? What difference would your
classification make?
3
What is it Like to Be a Bat?

• Imagine that you are a scientist investigating
  the behavior and physiology of a creature which
  possesses a sense you lack, for example, a bat.
  These animals, which are mammals with powerful
  brains, navigate by sonar, probing their
  surroundings with a stream of high-pitched
  squeaks the echoes allow them to distinguish
  shape, depth, motion and texture. Imagine that
  you are working in the distant future, when
  neuroscience can deliver a complete account of
  the bats inner workings. Suppose, as most of us
  do, that bats are conscious. Would mastering
  this account inform you of what it is like to be
  a bat?

4
The Difference that Color Makes

• Imagine you had been born completely color blind
  and could see the world only in shades of gray.
  One day scientists are able to restore your
  vision. Would you now know notice anything
  different?

5
The Inverted Color Spectrum

• Imagine that a mad scientist caused your color
  sensations (but not mine) suddenly to be
  inverted. Apples would look tomato colored to
  you and we would therefore no longer agree about
  the colors of objects--what I call green, you now
  call red. If so, our behavior will differ the
  physical facts which describe us will have
  changed, as our experience changes. So far this
  is perfectly consistent with the view that the
  physical facts tell all. Now imagine that you
  gradually adjust to the change in sensation. You
  begin to call apples green again (everyone else
  does, and it avoids a lot of explaining if you do
  the same) as time passes, they start to remind
  you of emeralds and Ireland, in the way they
  always did (after all, emeralds now look red, and
  so does Ireland). You get back on terms with
  tomatoes, as well after a couple of months you
  call them red, like the rest of the world, and
  you can appreciate the poetry of their French
  designation, pommes damour. Gradually your
  behavior reverts entirely to normal. You
  forget about the disturbing inversion of your
  color vision, a nasty shock from which you have
  now pretty well recovered. Then one day I ask
  you (rather unkindly) When you see apples
  nowadays, do they really look green to you, like
  in the old days, or are they actually red, just
  like tomatoes were? How would you respond?

6
The Earth Brain

• Suppose that the entire planet Earth was
  reordered to simulate the workings of a single
  brain (that is, to act as a mind according to
  functionalism). Lets imagine that each human
  being acted as a neuron, and communicated by
  special two-way radio in the corresponding way to
  all the other people. The current mental state of
  the Earth Brain would be displayed on satellites
  that could be seen from anywhere on Earth. The
  Earth Brain would then be connected via radio to
  a body, one that provides the sensory inputs and
  behavioral outputs of the Earth Brain. So the
  Earth Brain would possess all the elements of a
  functional description of the mind sensory
  inputs, behavioral outputs, and internal mental
  states causally connected to other mental states.
  If the planet Earth could be made to act in this
  way, would it then be conscious?