Transcript FoNS, Hist/Phil Module, Lecture 2

Neuro 95:
Foundations of Neuroscience
History & Philosophy Module
Brian Keeley
Philosophy, Pitzer College
Office: Broad Hall 107
Dion Scott-Kakures
Philosophy, Scripps College
Office: Humanities Bldg #215
Lecture 2
Housekeeping
 Assessment: An in-class exam on last
day of module (be able to identify and
talk about the significance of some
quotations & discuss some of the
philosophical arguments we’ll be
considering)
Today’s Reading
 Patricia Churchland, "Functionalist
Psychology"
Reductionism vs. Antireductionism
 Neuroscience, Psychology, Physics,
Economics are all sciences (purveyors of
different theories with different ontologies/
taxonomies/vocabularies)
 Question: What is the relationship
between these theories (especially as
they apply to the exact same region of
space-time; e.g., your suitemate)?
 “Completed Science”/ “The end of
Science”
Reductionism vs. …
 Reductionists are those who argue that
there really is only one, true scientific
theory.
 Ernest Rutherford (The “Father of Nuclear
Physics”): "All science is either physics or
stamp collecting”
… vs. Antireductionism
 Antireductionists are those who argue
that theories at different levels are
autonomous & independent of one
another.
 Psychology need not coordinate it’s
theory with neuroscience anymore than
Economists need to square their theories
of inflation with quantum mechanics.
 One influential set of arguments for
antireductionism comes from the
philosophical school known as
“Functionalism”
… vs. Antireductionism
 Jerry Fodor: “It isn't, after all, seriously in doubt that
talking (or riding a bicycle, or building a bridge) depends
on things that go on in the brain somewhere or other. If
the mind happens in space at all, it happens somewhere
north of the neck. What exactly turns on knowing how
far north? It belongs to understanding how the engine in
your auto works that the functioning of its carburettor is
to aerate the petrol; that's part of the story about how
the engine's parts contribute to its running right. But
why (unless you're thinking of having it taken out) does
it matter where in the engine the carburettor is? What
part of how your engine works have you failed to
understand if you don't know that?” (From Times
Literary Supplement)
Score-card
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Sterelny (& Fodor): Functionalist
Pat Churchland: Eliminativist
Reductionist (but spends time explaining
functionalism. She takes it seriously.)
Lycan: (Homuncular) Functionalist
Bechtel, Mundale, Zawidsky, Craver (to be
read during final integrative module): Trying to find
new ways of relating neuroscience and
psychology
So what is “reduction”?


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What’s at issue here is “theories” (not phenomena)
Theories—that is, structured sets of linguistic
statements—are what either do or don’t get reduced.
And, traditionally, it has been argued that one theory
(TR) is reduced by another theory (TB) when you can
logically derive TR from TB.
So what is “reduction”?
 So, we say that modern chemistry is
reduced by modern physics because the
laws of chemistry (how molecules bind
or don’t bind, how acid works, etc.) can
be deduced from the laws of physics
(the behavior of atoms and electrons,
etc.)
Or, for the visually-minded
The Explanandum or Explananda (pl)
S1
S2
Law in TR
Bridge
Law
Bridge
Law
The Explanans
P1
Law in TB
P2
Functionalism:
Levels of
explanation
In the Beginning…
There was AI

Back in the 1940s, Alan
Turing built one of the
first computers,
developed the science of
computation and along
the way, invented the
science of Artificial
Intelligence (AI).

(He also single-handedly won
WWII.)
(1912-1954)
Universal Computing



His idea: Computers can follow any
definable set of rules for converting
inputs into outputs.
This is the notion of a “Universal
Computer”. A device that can compute
any process that can be formally
described
Human, intelligent behavior is just a
complicated way of converting inputs into
outputs (Humans are very complex
information processing machines.)
Hardware & Software





The mind is the software that runs on the
hardware of the brain. Psychology figures out the
program and AI ports it to a new platform, the
digital computer.
(Cognitive) Psychology is the science of that
information processing.
Computer engineering is the study of computer
hardware
Neuroscience is the study of human hardware
(“wetware”?)
AI happens when you set up an artificial info
processor (a digital computer) to copy the formal
properties of another info processor (a human).
Levels

Example by way of analogy:
– Garry Kasparov vs. Deep Blue
3 Ways to explain Deep Blue’s
behavior



Hardware Design Level - wiring
diagram of the computer, the
transistors and gates, magnetic and
electrical states of the machine
Software Design Level - Deep Blue’s
computer program
“Folk Psychological” Level - Deep
Blue’s “knowledge,” “beliefs,” &
“desires”
Some considerations



Hardware Design Level - Most
complete explanation, but extremely
detailed and difficult to obtain
Software Design Level - Relatively
independent of the hardware level
(programmers are largely ignorant of
the details of hardware). Same
software can run on different
hardware.
Folk Psychological Level - A lot of
predictive power, but is this kind of
explanation merely a “useful
fiction”?
Can we do the same thing for
Kasparov?



Hardware Design Level - The
neuronal wiring of his brain,
states of his
neurotransmitters, etc.
Software Design Level - The
information processing of his
“cognitive systems” (memory
system, perceptual system,
etc.)
Folk Psychological Level - His
knowledge, beliefs, and
desires
Multiple realization
 An implication of the “computer
metaphor”
 The mapping from mind to physical
substrate is one-to-many. One and the
same mental state—being in pain,
believing George W. Bush is president,
etc.—can be realized in more than one
physical way.
 In a trivial fashion, each of us can be
said to have the same beliefs, even
though each of our brains is physically
unique.
Multiple realization
 More extreme cases:
 Left vs. Right hemispherectomy
cases
 Human pain vs. Octopi pain
 The possibility of artificial
intelligence
 Functionists take the phenomenon
of multiple realization to entail that
mental phenomena cannot be
theoretically reduced to brain
phenomena.
Fodor’s Picture
S1
S2
Law in TR
Wildly
Disjunctive
P1 P2 P3…Pn
P’1 P’2 … P’m
Many Disparate Laws in TB