The Matrix as Metaphysics

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The Matrixas Metaphysics

• David J. Chalmers

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The Matrix

• In The Matrix
• Neo is hooked up to a giant computer simulation.
• He has experiences of a normal reality in 1999.
• In fact, it is 2199, and his body is floating in
  a tank.
• A version of an old philosophical fable
• René Descartes evil genius
• The brain in the vat

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Brain in a Vat

• A brain in a vat, connected to a computer
  simulation of the world, might have the same
  experiences that I do.
• The brain in a vat has beliefs corresponding to
  mine.
• I have hands
• There is a table in front of me.
• I am in Tucson.
• These beliefs are massively false.

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Envatment

• Lets say
• A matrix an artificially-designed computer
  simulation of a world.
• X is envatted (or X is in a matrix) X has a
  cognitive system which receives its inputs from
  and sends its outputs to a matrix

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The Matrix Hypothesis

• The Matrix Hypothesis I am (and have always
  been) in a matrix.
• For all I know, the Matrix Hypothesis is true!
• I cant rule it out with certainty.
• There may be many matrices developed in the
  history of the universe.
• One real world, many simulated worlds.
• More likely Im in a simulated world?

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Envatment as Delusion

• Common view If the Matrix Hypothesis is true,
  then I have massively false beliefs
• I do not have hands
• There is no table in front of me
• I am not in Tucson
• I am completely deluded about reality.

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Reality as a Hoax

• Perception Our day-in, day-out world is real.
• Reality That world is a hoax, an elaborate
  deception spun by all-powerful machines of
  artificial intelligence that control us. Whoa.
• (from The Matrix DVD)

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Skeptical Hypothesis

• If so the Matrix Hypothesis is a skeptical
  hypothesis
• Its possibility suggests that we know very little
  about the world.
• Skeptical argument
• I dont know that Im not envatted
• If Im envatted, most of my beliefs are false
• I dont have hands, Im not in Tucson, etc.
• So I dont know most of the things I believe
• I dont know that I have hands, that Im in
  Tucson, etc.

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The Matrix Reconsidered

• Ill argue
• The Matrix Hypothesis is not a skeptical
  hypothesis
• Even if I am envatted, I still have hands, there
  is still a table in front of me, I am still in
  Tucson.
• Brains in vats have mostly true beliefs
• If I am in a matrix, things are perfectly real.

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Appearance and Reality

• George Berkeley
• Esse est percipi
• To exist is to be perceived
• Idealism reality a set of appearances
• If so the matrix yields reality.
• I dont accept idealism
• But will argue that nevertheless (for different
  reasons), the matrix yields reality.

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Envatment as a Metaphysical Hypothesis

• Ill argue the hypothesis that I am in a matrix
  is not a skeptical hypothesis, but a metaphysical
  hypothesis.
• It is equivalent to a hypothesis about the
  underlying metaphysical nature of the world.
• If accepted, this hypothesis might revise a few
  of our beliefs, but it would leave most of them
  intact.

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Three Metaphysical Hypotheses

• Ill present three metaphysical hypotheses about
  the nature of our world, none of which is a
  skeptical hypothesis.
• 1. A Creation Hypothesis.
• 2. A Computational Hypothesis
• 3. A Dualistic Hypothesis
• (Well then be considering their combination.)

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Creation Hypothesis

• Creation Hypothesis Physical space-time and its
  contents were created by agents outside physical
  space-time.
• Cf. religious views of creation.
• The Creation Hypothesis could be true.
• The Creation Hypothesis is not a skeptical
  hypothesis
• If the Creation Hypothesis is true, I still have
  hands, there is still a table in front of me, I
  am still in Tucson.

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Creation Hypothesis
Creator
Atoms
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Computational Hypothesis

• Computational Hypothesis Physics is
  computational.
• I.e., microphysical processes throughout
  space-time are constituted by underlying
  computational processes.
• Just as chemistry is constituted by physics,
  physics is constituted by computations
• Underneath particles are patterns of bits
• E.g. Wolfram, A New Kind of Science
• An underlying cellular automaton?
• Perhaps these computational processes are
  themselves implemented by more basic processes.

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Computational Hypothesis
Atoms
110101101011011010000111
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Computational Hypothesis II

• The Computational Hypothesis could be true.
• The Computational Hypothesis is not a skeptical
  hypothesis
• If it is true, there are still electrons and
  protons (they are just implemented, as are
  molecules).
• If it is true, I still have hands, and so on.
• To accept it would involve revision to some of
  our beliefs, but not massive revision.
• No more than quantum mechanics!

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Dualistic Hypothesis

• Dualistic Hypothesis My mind is nonphysical and
  interacts with the physical.
• My cognitive processes are outside physical
  space-time, and receives their inputs from and
  send their outputs to processes in physical
  space-time.
• Cf. Descartes dualism.
• The Dualistic Hypothesis could be true.
• The Dualistic Hypothesis is not a skeptical
  hypothesis
• If it is true, I still have hands, and so on.

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Dualistic Hypothesis
Mind
Atoms
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Combination Hypothesis

• Combination Hypothesis A combination of the
  Creation Hypothesis, the Computaional Hypothesis,
  and the Dualistic Hypothesis.
• Physical processes were created by other beings,
  are computationally implemented, and my
  nonphysical mind interacts with them..
• The Combination Hypothesis could be true.
• The Combination Hypothesis is not a skeptical
  hypothesis.
• If it is true, I still have hands, and so on.

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Metaphysical Hypothesis

• Metaphysical Hypothesis The Combination
  Hypothesis, plus
• The computational processes were designed by the
  creators in order to simulate a world.
• and maybe The implementing processes, my
  cognitive processes, and the creators are all
  part of a broader domain.
• The Metaphysical Hypothesis could be true.
• The Metaphysical Hypothesis is not a skeptical
  hypothesis.
• If it is true, I still have hands, and so on.

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Metaphysical Hypothesis
Atoms
110101101011011010000111
Mind
Creator
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Matrix/Metaphysics Equivalence

• Matrix Hypothesis
• My cognitive system receives its inputs from and
  sends its outputs to an artificially-designed
  computer simulation of a world
• Claim The Matrix Hypothesis is equivalent to the
  Metaphysical Hypothesis.
• If I accept the Metaphysical Hypothesis, I should
  accept the Matrix Hypothesis.
• If I accept the Matrix Hypothesis, I should
  accept the Metaphysical Hypothesis.

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Metaphysics ? Matrix

• Dualistic Hypothesis ? My cognitive system
  receives its inputs from and sends its outputs to
  physical space-time.
• Computational Hypothesis ? My cognitive system
  receives inputs from the computational processes
  implementing physical space-time.
• Creation Hypothesis ? These computational
  processes were artificially designed to simulate
  a world.
• Jointly My cognitive system receives its inputs
  from and sends its outputs to an
  artifically-designed computer simulation of a
  world
• The Matrix Hypothesis!

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Matrix Hypothesis
110101101011011010000111
Mind
Creator
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Matrix ? Metaphysics

• Matrix Hypothesis Underlying reality is just as
  Metaphysical Hypothesis specifies
• A computational implementation of physics,
  artificially designed, interacting with my
  cognitive system.
• Things are the same at the underlying level, so
  things are the same at all levels
• So the Matrix Hypothesis implies the Metaphysical
  Hypothesis.

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The Matrix Not Skeptical

• The Matrix Hypothesis is equivalent to the
  Metaphysical Hypothesis
• The Metaphysical Hypothesis is not a skeptical
  hypothesis
• So The Matrix Hypothesis is not a skeptical
  hypothesis
• Even if I am envatted
• I have hands
• There is a table in front of me
• I am in Tucson

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The Matrix as Metaphysics

• If I discover that I am in a matrix, I should not
  reject my ordinary beliefs about tables, etc.
• Instead, I have made a metaphysical discovery
  about what tables are made of.
• The world is fundamentally made of bits!

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Life in the Matrix

• So people in the Matrix have mostly true beliefs
• At least if the Matrix has been running for a
  long time.
• A multi-vat matrix is needed for true beliefs
  about other minds.
• Brains in vats are not deluded.
• If we are in a matrix, things are perfectly real
• Its just that the world is fundamentally
  computational.
• No worse than the world being fundamentally
  quantum-mechanical!

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Objection Simulation is not reality

• Objection The matrix is simulation, not reality
• Response The Computational Hypothesis tells us
• Computation could underlie real physical
  processes
• The computation must have all the detail of
  physics
• The computation can itself be implemented.
• The nature of the implementation doesnt matter.
• That it was designed as a simulation is
  irrelevant.
• So a computer simulation could underlie reality
• If it is the basis of our experiences.

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Objection Deluded BIV?

• Objection A brain in a vat might think Im out
  in the sun, when its in a dark lab. Deluded?
• Reply The surroundings of the BIV in the brains
  domains are irrelevant.
• Compare A person with a Cartesian mind might
  think Im out in the sun, while the mind is
  really solitary ectoplasm. Deluded?
• Surroundings in the ectoplasmic domain are
  irrelevant,
• What matters is the causal basis of the cognitive
  systems experiences and beliefs, not the
  systems surroundings.

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Objection Neo has hair?

• Objection Neo thinks I have hair.
• This thought will be true if the Neo has hair.
• But Neo does not have hair!
• So the Neos thought is false.
• Reply Hair means something different for a
  BIV.
• For BIV, hair refers to virtual hair,
  constituted by computational processes.
• BIV has virtual hair!
• Same for virtual chairs, tables, etc.

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Objection BIV has world all wrong

• Objection If we are envatted, the world is
  nothing like we think it is.
• Reply I deny this. Even if we are envatted,
  there are still people, tables, football games,
  particles, arranged in space-time just as we
  think they are.
• Deeper point Its just that the world has a
  further nature that goes beyond our common sense
  conception. E.g.
• quantum mechanics.
• science reveals worlds structure, leaving
  intrinsic nature open

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Residual Skepticism

• Matrix envatment is a non-skeptical hypothesis.
• But other skeptical hypotheses remain

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The Local Matrix

• Local Matrix Only my local environment is
  simulated, not all of physical space-time.
• E.g. The Thirteenth Floor
• Akin to Truman Show skepticism I still have
  hands, a body, a house, but false beliefs about
  things further from home.
• Moral Being in the Truman Show is much worse
  than being in the Matrix!

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Other Skeptical Hypotheses

• Recent Envatment My mind was recently isolated
  and connected to a computer simulation.
• Yields false beliefs about my present
  environment, although past beliefs are OK.
• Chaotic Envatment My mind is isolated and
  receives random stimulation from all sorts of
  sources that coincidentally yield apparent
  regularity.
• Arguably yields largely false or empty beliefs.

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Tentative Moral

• If we assume there is some explanation for the
  regularities in our experience, global
  external-world skepticism is ruled out.
• Explanation yields reality?

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Conclusion

• Its not so bad to be a brain in a vat.

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Next Time

• The mind-body problem
• DP, Chapter 2
• Descartes, Meditations 1 and 2