About the explanatory gap: Chalmers on Perry


We shall have a class discussion at the end. So please read Chalmers' paper.

Explanatory gap

  • About phenomenal consciousness - concepts of consciousness
  • We might discover that phenomenal state Q is correlated with physical brain state B.
  • But this does not explain why what it is like to be in state B is the same as what it is like to be in state Q. Why can't it be like being in some other phenomenal state R? Or, why can't there be a zombie with state B?
  • What is the gap? Suppose P = conjunction of all physical truths. Q = truth about qualia.
    • Gap = P→Q is not a priori. (knowledge argument, inverted spectrum)
    • Compare: (P→water contains hydrogen) is a priori.
  • the knowledge argument about consciousness
  • Some possible responses:
  1. There is a gap because dualism is true.
  2. There is no explanatory gap. We can already close the gap.
  3. There is no explanatory gap, but we are not smart enough to understand why.
  4. There is an explanatory gap now, but more scientific research will fill the gap.
  5. There is an explanatory gap now, but a new kind of science is needed to fill the gap.
  6. There is an explanatory gap, but it is only due to a gap between our phenomenal and physical concepts. There are no ontological consequences.

concept of X vs. X itself

The zombie argument against physicalism

What are zombies?

  1. Zombies are conceivable. (No a priori contradiction in the idea of a zombie.)
  2. If zombies are conceivable, then they are possible.
  3. If zombies are possible, then physicalism is false.
  4. Therefore, physicalism is false.

The phenomenal concept strategy

@Proponents of this strategy argue that phenomenal concepts — our concepts of conscious states — have a certain special nature. Proponents suggest that given this special nature, it is predictable that we will find an explanatory gap between physical processes, conceived under physical concepts, and conscious states, conceived under phenomenal concepts. At the same time, they argue that our possession of concepts with this special nature can itself be explained in physical terms.@

Some proposals:

  1. Phenomenal concepts are recognitional concepts.
  2. Phenomenal concepts and physical concepts have different conceptual roles.
  3. Phenomenal concepts are indexical.
  4. Phenomenal concepts are quotational.

Attractive features

  1. Acknowledge intuitive puzzle.
  2. Deflate anti-physicalist conclusions. "conceptual dualism and ontological monism"

Perry's approach


@Sugar pours out of a bag in John Perrys shopping cart. He is looking for the person who is making a mess, and finally he realizes that it's himself.@

  1. I am making a mess.
  2. The one who is pouring sugar on the floor is making a mess.
  3. The only bearded philosopher in a Safeway store west of Mississippi is making a mess.
  4. John Perry is making a mess.
  • Claim #1 is not equivalent to any combination of non-indexical claims such as #2, 3, 4, etc.
  • Indexical knowledge cannot be reduced to (defined in terms of) non-indexical knowledge, but it does not show that physicalism is false.
  • Mary gains indexical knowledge when she sees something red for the first time.

@Mary gains new knowledge of the form "red things cause experiences of type P". This knowledge crucially involves a phenomenal concept P — a concept of what it is like to have a certain sort of experience. Perry's strategy (pp. 145-48) is to analyze Mary's phenomenal concept P as a demonstrative concept — which he labels this_i — that functions, like other demonstrative concepts, to pick out whatever sort of experience she is currently attending to.@

Chalmers' replies

Reply #1 - Mary's knowledge is not just indexical knowledge

  • Yes. Mary gains indexical knowledge, but this is not interesting. What is important is that she gains substantive qualitative knowledge using some non-indexical, qualitative concept. See especially the paragraph: "On the face of it, Mary's situation is precisely analogous. ..."
  • "The experience of seeing a red tomato is R." vs. "The experience of seeing a red tomato is this_i"
  • Why does Chalmers think that there is this concept R distinct from this_i?

@it seems that Mary could have had different thoughts of the form "this_I is G" had she been exposed to a different sort of experience, such as an experience of green. So it seems that the qualitative concept of the experiential type is quite different from the demonstrative concept.@

Reply #2 - Indexicals are irrelevant to the explanatory gap

  • Ignorance due to indexicals disappears from the 3rd person point of view.
    • An observer looking at Perry making a mess has no ignorance when all non-indexical knowledge is known.
  • But the explanatory gap about consciousness does not disappear from the 3rd person point of view, e.g. ignorance about what it is like for other people to have a certain experience.

Class discussion

  • Regarding the zombie argument, suppose someone wants to refute premise #2 as follows: "The fact that something is conceivable does not imply that it is possible. I can conceive of 70375 being divisible by 3. But it is actually not possible." Why is this not a good objection?
  • Evaluate the two replies from Chalmers to Perry.