\documentstyle[marc,doublespace,11pt,palatino]{article}

\setallmargins{1.25in}
\setstretch{2}
\parindent=0.3in

\def\tm{Turing machine}
\def\fct{functionalism}
\def\tmf{Turing-machine functionalism}

% behaviorism and identity theories

% connectionism?  good or bad?

% conscious/unconscious

% refute Block's objection from Clark

% the ``pain'' thing

% explicitly and non-explicitly represented beliefs/desires (Block p.
% 271-)

% the swamp creature

\begin{document}
\vspace*{0.1in}
\begin{center}
{\Large Why the Theory of Turing-Machine Functionalism Works}\\
{\large Marc Horowitz \\
April 1, 1992}
\end{center}
\vspace{0.5in}

If the computational theory of cognition is correct, the most general
model we can choose is a \tm.  Since a \tm{} operates on discrete
states and inputs, then there must be an internal representation of
mental states, a representation of external stimuli, and the output of
the machine must represent some action.  The theory of \tmf{}
satisfies these requirements and stands up well to objections.

It is fairly obvious that what is important about thinking is not the
details of the input or the output.  We should not be concerned with
how vision or hearing works, or how muscular contraction works.
Similarly, the chemistry of the brain is unimportant.  What is
important is how stimulus, beliefs, and desires bring about new
beliefs, desires, and actions.  \tmf{} puts forth a theory where we
abstract out the physical details of stimuli, belief, and desires into
intentional states which are independent of the individual, or even
the species.  According to Block, ``what gives internal symbols their
meanings is how they function.''  How they function is determined by
how they affect the output of the \tm{} which represents the cognitive
functions of the brain.

This can be compared to behaviorism, which states that ``mental states
were identical with sets of actual and counterfactual overt behaviors
and that inner states of the subject, though no doubt causally
implicated in such behaviors, were not theoretically important to
understanding what it {\em is} to be in certain mental states (Clark,
chapter 1).''  The major objection to this theory is that without
significant intentional states, we cannot form a computational model.
We need to treat the brain as more than a black box which takes
stimuli as input and produces actions as output.  On the other end of
the scale are identity theories, which attempt to link directly mental
states and physiological states.  This theory fails to explain the
possibility of intelligent beings who have a biology entirely
different than ours.  In the middle is \tmf{}.  Clark notes that
``What is essential to being in a certain mental state... is being in
a certain abstract functional state.''  These abstract functional
states are linked to physiological states, but this linkage is only an
artifact of our bodies, it is not important to the understanding of
mental states.

Clark describes an objection to functionalism raised by Block.  Block
claims that by abstracting out the physical instantiation of the mind,
you can arrive at systems, such as the Chinese message passing system,
which could appear to have mental states, but which intuitively lack
whatever it is which makes something ``intelligent''.  I think that
this argument is flawed.  Given sufficient structure and complexity, a
system should be capable of having mental states, regardless of how
oddly constructed it may seem at first glance.  The cognitive
significance of the state of a \tm{}, whether instantiated in human
brain tissue, silicon chips, or rubber bands and chewing gum, remains
the same.  This is what makes \tmf{} so attractive.

Another disagreement I have with Block is his notion of what makes a
mental state intentional.  He claims that ``Intentional states
represent the world as being a certain way.''  He gives the example of
tree rings having intentional states, representing the age of the
tree.  But, he then gives the example of the ``swamp replica'' of an
individual, which (he claims) possesses no intentional states.  I fail
to see why the representations of the world encoded in the swamp being
are any different from the representations of the world in the
original person.  Block thinks they are quite different.
\vspace{-\baselineskip}
\begin{singlespace}
\begin{quotation}
[The swamp creature's] utterance is not in any way causally affected
by Gorbachev or Thatcher or England, or by Gorbachevian or Thatcherian
or English states of the world, so how can it be regarded as being
{\em about} Gorbachev or Thatcher or England?  The swamp creature is
simply mouthing words.
\end{quotation}
\end{singlespace}
\vspace{-\baselineskip}
Hamlet, if written by an infinite number of monkeys pounding on
typewriters, rather than a single British playwright expounding on
human nature, would be no less a great work of literature.

Block also says that ``Pain, for example, would seem to be a mental
state that has no intentional content.''  I completely disagree.
Being in pain is a mental state closely associated with certain
physical states in the world.  For humans, this means having certain
nerves and receptors stimulated.  Even creatures which don't have the
same kind of pain receptors we do would probably react in similar ways
to pain, leading me to believe that being in pain is an abstract
intentional mental state, just the same as believing the earth is
round.

In general, I do believe that \tmf{} is the proper theory of mental
states.  It abstracts cognitive processes away from their medium, so
it represents all possible kinds of cognition, and at the same time,
allows analysis of how stimuli, beliefs, desires, and actions are
related.

\end{document}
