Identity Theory - Eli Alshanetsky

Report
Summer 2011
Thursday, 07/07
Loose Ends: Wittgenstein’s Beetle
• Each of us carries a box with something that each of us calls
a beetle.
• We can only look inside our own boxes, not anyone else’s
box.
• How, then, can I know that what I’m calling beetle is the
same type of thing as what you’re calling beetle?
Maybe your box has something completely different…
Loose Ends: Wittgenstein’s Beetle
• Similarly, for the Dualist, each of us has a mind that
sometimes contains something that each of us calls
pain.
• We can only look inside our own minds, not anyone
else’s minds.
• How, then, can I know that what I’m calling pain is
the same type of thing as what you’re calling
pain? Maybe your mind has something
completely different in it and we’re using the
same word to talk about radically different things.
• This problem does not arise for the behaviorist.
Philosophical Methodology
• Concepts = Ways of Thinking, General Ideas.
• Some concepts have analyses or definitions,
E.g,
Vixen =def Female Fox
Bachelor =def Unmarried Adult Male
Opthomologist=def Doctor who
specializes in eyes
Philosophical Methodology
• Some (putative) analyses or definitions are
Philosophically important, e.g,
Knowledge=def Rational True Belief
Moral Action=def Action That Maximizes
Collective Pleasure.
• Sometimes it’s difficult to come up with a complete
analysis or definition of a concept and only partial or
incomplete definitions may be available.
Philosophical Methodology
•
An Analytic Claim is (roughly) one that’s true
by definition: it is a claim that either (a)
articulates a definition or (b) one that follows
from a definition, e.g,
Opthomologists are Doctors
Bachelors are males
Philosophical Methodology
Analytic claims are true by logical necessity,
which is the strongest of all forms of necessity
(stronger even than physical necessity).
• A claim is logically necessary just in case it is true
in all conceivable or imaginable situations (or
logically possible worlds).
• Contrast: a claim is physically necessary (or
necessary, given the Laws of Physics) just in case
it is true in all physically possible worlds.
•
Philosophical Methodology
• Let’s look at an example.
• The simplest way of creating a concept is by
explicitly defining it, e.g,
BLUP =def Any person who is enrolled in
Eli’s Minds and Machines Course this
term.
Philosophical Methodology
• Now consider some claims that follow from this definition:
1. All BLUPs are enrolled in Eli’s Minds and
Machines course this term.
2. All BLUPs are persons.
• Since these claims follow from the definition of BLUP,
denying them would not just be false, it would be
nonsense. There is no conceivable situation where the
negation of these claims would be true.
Philosophical Methodology
We can thus say:
1. Necessarily, all BLUPs are enrolled in Eli’s Minds and
Machines course this term.
2. Necessarily, all BLUPs are persons.
Contrast this with:
3. Necessarily, nothing travels faster than the speed of light.
4. Necessarily, gravity attracts us to the earth.
3 and 4 involve claims that are true in all physically
possible scenarios. 1 and 2 involve claims that are true in
all conceivable scenarios, or are true in all scenarios
period.
Philosophical Methodology
• I’ve said that if a claim is a definition (or is true
by definition), then it is true in all conceivable
cases or scenarios.
• So: if we find at least one conceivable or
imaginable scenario where the claim is false,
then the claim does not articulate a definition
(nor does it follow from one).
• This method is parallel to the one used in
physics, math…
Philosophy and Science Fiction
• We can now see how remote science fiction scenarios
can help refute Philosophical claims.
• The Logical Behaviorist says:
Pain =def A pattern of actual/potential
behavior that involves wincing, making certain
reports, etc.
Putnam argues that there are conceivable scenarios
where this claim is false (e.g. Super-Spartans, Xworlders). If Putnam is right, then the above claim is
not true by definition: our concept of pain is not that of
a certain pattern of behavior. So logical Behaviorism is
false.
Identity Theory vs. Behaviorism
• Behaviorism: Mental States =def Patterns of
Actual/Potential Behavior.
• Putnam’s Thesis: Mental States =def Whatever
Causes our patterns of Actual/Potential Behavior.
(notice that this is compatible with Dualism!)
• Identity Theory: Mental States =met
States/Processes in the Brain.
Identity Theory vs. Behaviorism
• Since the logical behaviorist is making a claim
about our concepts or ways of thinking, it is
important that the behavior she appeals to is
overt and publicly observable.
• Brain states/processes cannot be instances of
behavior (in the behaviorist’s sense), since it’s
implausible that we think about them when
we think and talk about mental states.
Identity Theory vs. Behaviorism
• The identity theorist does not claim that our
concepts of mental states/processes are
concepts of brain states/processes.
• Rather, she makes a claim about the relation
between the mental and the physical items
themselves.
• Compare: our concepts of water/light/weight
vs. what water/light/weight really are.
Two theses about the mind-brain
relation
• Mind-Brain Correlation Thesis: For each type
M of mental event that occurs to an organism
o, there exist a brain state of kind B (M’s
“neural correlate” or “substrate”) such that M
occurs to o at time t if and only if B occurs to o
at t.
Two theses about the mind-brain
relation
Some motivation for the correlation thesis:
• brain lesions are correlated with changes in mental states
– strokes
– brain injuries
– concussions
• chemical changes in the brain are correlated with changes
in mental states
–
–
–
–
–
caffeine
alcohol
Hallucinagenic drugs (e.g. LSD)
anesthesia
Opiates
Two theses about the mind-brain
relation
• Mind-Brain Identity Thesis: There are no mental
events over and above, or in addition to, the
neural processes in the brain. Mental event types
are identical to types of brain events, e.g. pain =
C-fiber firing, belief that snow is white = cortical
configuration X.
• Notice that the second thesis implies the first
(and explains it), but not vice versa.
Arguments for the identity theory
Occam’s razor: Advocates theoretical simplicity.
I. Entities must not be multiplied beyond
necessity.
II. What can be done with fewer assumptions
should not be done with more.
• Most of what we know of consists of some
arrangement of physical stuff. To suppose the
mind to be nonphysical would be to admit a
completely new type of entity. So it would be a
gain in simplicity to identify mental processes
with physical processes.
Arguments for the identity theory
Scientific Precedent:
• gene =def. occupant of such and such a causal role, i.e., the
role of "an internal factor in the organism that is causally
responsible for the transmission of heritable
characteristics."
• We find that DNA molecules are what perform that causal
role.
• Conclusion: genes = DNA molecules.
• Analogous situation: pain =def. effect of bodily damage &
cause of pain-behavior
• neurophysiology reveals C-fiber activation occupies this
role.
• Conclusion: pain = C-fiber activation.
Arguments for the identity theory
Mental Causation:
We discover that some brain-state (e.g. C-fiber
activation) causes pain-behavior.
If pain ≠ C-fiber activation, then either:
A. Overdetermination: unlikely.
B. Epiphenomenalism: implausible.
So, pain = C-fiber activation.
Leibniz’s Law of Numerical Identity
The Indiscernibility of Identicals: If X is identical
with Y, X and Y have all their properties in
common -- that is, for any property P, either both
X and Y have P (at time t) or both lack it (at t).
Leibniz’s Law of Numerical Identity
Applications in Arguments:
X is P
Y is not P
Conclusion: X ≠ Y
• Example
– Eli lives in Brooklyn.
– Obama does not live in Brooklyn.
– Conclusion: Eli is not Obama.
Using LL to argue against the identity
theory
- Pain has the property of being known to
Aristotle.
- C-fiber activation lacks the property of being
known to Aristotle.
- Pain ≠ C-fiber activation.
Using LL to argue against the identity
theory
- physical property instances (e.g., c-fiber
activations) have spatial locations.
- mental property instances (e.g., pains) have
no spatial locations.
- Mental property instances (e.g., pains) ≠
physical property instances (e.g., c-fiber
activations).
Using LL to argue against the identity
theory
- physical property instances (e.g. activation of
the visual cortex) have no experiential
properties (e.g. a yellowish feel).
- mental property instances (e.g. color
experiences) have experiential properties (e.g.
a yellowish feel).
- mental properties (e.g., color experiences) ≠
physical properties (e.g., activation of the
visual cortex)
Multiple Realization Argument against
the identity theory
- The identity theorist says that pain is C-fiber
excitation.
- But that implies that unless an organism has
C-fibers, it cannot have pain.
- But how can we be sure that all pain-capable
animals have C-fibers? Could there not be
intelligent extraterrestrial creatures with a
complex mental life but whose biology is not
even carbon based?
Quiz
• What is the Mind-Brain Identity Theory and
how is it different from Logical Behaviorism?
For Monday
• We’ll talk about Functionalism, a completely
different way of looking at the mind, that
takes the multiple realization argument very
seriously.
• Read Chapter 1 of the Yellow Book.
• Turing’s article “Computing Machinery and
Intelligence” is highly recommended.

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