The Modal Argument

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The Modal Argument
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Review The Hard Problem

• Remember that there are three arguments that make
  consciousness a hard problem.1. Knowledge
  Argument2. Modal Argument3. Explanatory Gap
  Argument
• Hard Problem we do not know how to go about
  solving it isolating neural or computational
  mechanisms is not enough.

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1. The Knowledge Argument

• P1 Physicalism says that all facts are physical
  facts.
• P2 In the room, Mary has complete physical
  knowledge of color perception.
• P3 When she leaves the room, Mary acquires new
  knowledge (i.e. what it is like to see red).
• C Physicalism if false there are facts (i.e.
  about phenomenal properties) which escape the
  physicalist story.

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Response 1

• P3? Churchland maintains that this is possibly
  false.
• We do not understand as much about the brain as
  Mary does.
• So perhaps Mary would say (when shown tomato)
  Ahh, just as I thought.

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Response 2

• Equivocation? What does it mean to say that Mary
  gains new knowledge when she sees the tomato?
• Churchland argues that, even if Mary does acquire
  new knowledge, this does not mean that there are
  facts that escape physicalism.
• Mary merely gains a new way of knowing old facts.
  

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Worry

• Are Churchlands responses consistent?
• It seems that his response to Jackson is that (a)
  Mary would know, before release, what it is like
  to see red and (b) Mary would learn what it
  is like to see red, but this new knowledge would
  not undermine physicalism.
• Charitable reading Mary might very well know,
  but even if she doesnt, it would not undermine
  physicalism.

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2. Modal Argument

• Today we turn to the second argument in the
  trilogy.
• This argument was presented by Saul Kripke (b.
  1940-) in a series of lectures he gave at
  Princeton in 1970.

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Zombies

• Kripkes argument is based upon what philosophers
  have called the zombie hunch.
• So let us be clear philosophical zombies are
  nothing like Hollywood zombies.

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Hollywood Zombies

• Hollywood zombies are reanimated dead-people who
  like to eat human flesh.
• They often have strange behavioral features (they
  usually walk slowly and awkwardly, although in 28
  Days Later they run really fast).

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Philosophical Zombies

• They look and behave just like you and me.
• But their defining feature is that they do not
  have any consciousness.
• So as philosophical zombie is physical identical
  to a normal human being, but there is nothing it
  is like to be them.

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Challenge to Physicalism

• Question Why are philosophers worried about such
  Zombies?
• Answer They are a serious threat to Physicalism.
  Physicalists cannot allow that you can have a
  zombie twin which is physically identical to you
  but who lacks consciousness.
• If all properties are physical properties, then
  someone who shares all your physical properties
  must have the same consciousness.

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The Zombie Argument

• A thumbnail sketch of the argument might look
  something like thisP1 Physicalism says that
  all truths are physical truths.P2 Zombie twins
  are possible.C Physicalism is false.

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Physicalist response?

• It is tempting to say, in response, that this
  merely shows that mind-body identity is a
  contingent truth.
• (Note This is what JJC Smart says in response to
  the objection that we can conceive of being
  turned to stone, yet feel pain).
• To make heads or tails of this response, we need
  some modal terminology.

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Modality

• Talk of modalities refers to the way we qualify
  the truth of judgments with respect to possible
  worlds.
• Possible world maximally complete (i.e. leaves
  out no information) consistent (i.e.
  non-contradictory) set of facts about the world. 
  
• Contingent truths These are truths that are
  true in some worlds, but false in others.
  Necessary truths These are truths that are
  true in all worlds.
• So the temptation is to say that MB is
  contingently true in our world. Thus, the fact
  that we can imagine zombies only shows that there
  are other worlds in which the identity does not
  hold.

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Kripke on A Posteriori Necessity

• Kripke argues that this is a mistake. He
  maintains that natural kind terms such as pain
  and c-fiber firing are rigid designators that
  have the same reference in every possible world.
  
• This entails that the following premise is
  trueP1 If MB, then NEC (MB).

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Clarifications

• It is contingent that mean kinetic energy causes
  sensation of heat but it is necessary that
  physical heat MKE.
• We often think that this theoretical identity is
  contingent because it is a posteriori (it
  required experience and scientific method to
  discover it).
• Philosophers used to think that all necessary
  truths were analytic but Kripke convinced most
  people that there are a posteriori necessary
  truths.

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The Modal Argument

• P1 If pain c-fiber firing, then NEC (pain
  c-fiber firing). P2 We can conceive of
  zombies whose c-fibers are firing but who do not
  feel pain.P3 Conceivability entails
  metaphysical possibility. P4 Zombies are
  metaphysically possible. C It is false that
  pain c-fiber firing.

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Kripkes Blocked Move

• Kripke recognizes that physicalists might offer
  the following move we can explain away the
  zombie hunch and deny P4.
• How so? Because it also seems possible that we
  could have water without H20. But they are
  necessarily identical. So we cannot trust such
  hunches. They are just modal illusions.
• Question Why does Kripke maintain that this
  strategy will not work in the case of pain?

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Kripkes Blocked Move
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Kripkes Blocked Move

• Kripke agrees that materialists can explain away
  the water hunch. But this will not work for
  the case of pain.
• The reason is that we recognize instances of
  WATER through their accidental features. It just
  so happens that water appears to us as clear,
  etc. But it might appear differently to
  creatures on Mars.
• But we cannot say this with PAIN. We recognize
  pain through its essential property. If it
  didnt hurt, it would not be pain!

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Hills Reply

• Question How does Hill respond to Kripke? Does
  he manage to avoid the block?