\magnification\magstep1
\baselineskip=2\baselineskip
\parskip=6pt plus 2pt minus 1pt

\font\lf=pbkd at 20pt

\newbox\foobox

\def\problem#1{\vskip20pt\noindent\hbox to\parindent{\bf #1.\hss}}
\def\ul#1{\setbox\foobox=\hbox{#1}\lower.5pt\hbox to 0pt{\vrule height0pt
depth.6pt width\wd\foobox \hss}\copy\foobox}

\line{\hss Albert Dvornik}

\centerline{\lf Minds and Machines}
\centerline{\lf Problem Set 6}

\vskip20pt

\problem 1
Putnam believes in the ``hidden scientific essence'' theory.  He
argues that the mental content of a term like {\it water\/} shouldn't be
able to change more or less arbitrarily over time (and space).

The superficial property theory {\it defines\/} each term in terms of a
certain set of its properties.  But who chooses what that particular
set of properties is?  Is a man a ``rational animal'' or a
``featherless biped?''  Different ``experts'' will invariably claim
different answers to questions similar to this one.

Problems also occur with increasing our (or our experts') knowledge.
When the appropriate experts find a way of distinguishing water and
twin-water, the meaning of ``water'' in the superficial property
theory suddenly {\it stops\/} including twin-water, since the property
gets added to the property list.  This ``jump'' is not consistent with
our standard conception of meaning.

\problem 2
The answer to this question depends entirely on one's understanding of
the term ``meaning.''  Superficial property theory is (in my opinion)
a good description of how our brain processes meaning recognition;
however, I usually associate the term ``meaning'' with ``{\it broad\/}
meaning.''  I tend to agree with Putnam's answer, and here are some of
my reasons.

We seem to have an intuitive notion of ``pure water'' that has a
certain set of physical and properties in our world (even if we don't
know all of these properties).  If we acknowledge twin-water to be a
substance somehow {\it different\/} from water (for a 20th-century
scientist, at least), then it necessarily {\it doesn't fit\/} our
experiences with normal water.  In fact, the very idea of ``pure
water'' doesn't make sense in the superficial property theory.  There
is no way to classify a ``colorless odorless thirst-quenching liquid
found in lakes on Earth and Twin-Earth'' as being ``pure'' at all.

Any {\it finite\/} superficial property approach is flawed, since there
will always be properties that are missing.  But the larger our list
of properties grows, the less likely we are to run into a problem of
the ``water---twin-water'' sort.  Suppose we accumulated a list of
{\it all\/} properties of water (a lot of them probably far beyond the
limits of the 20th century science).  It seems obvious that such a
list needs to be infinite (since a finite list can't exhaust all the
things we could know about water).

But suppose we accumulated such a list.  It seems to me that such a
list would be {\it equivalent\/} to the ``hidden essence'' definition of
water; if twin-water has all of these properties, it {\it is\/} the same
thing as water.  (I think Putnam would have to agree with this.)
[Note that twin-water can't have additional properties that water
doesn't have, since properties like ``water doesn't have the property
...'' must be included in the list of {\it all\/} properties.]

\problem3
It is clear that, at this point, we are beginning to have problems
with the meaning of the word ``meaning.''  We have seen two completely
opposite theories, and both seem to make sense on completely different
levels; but they clearly cannot coexist.  Therefore, it's natural to
start distinguishing between these two ideas of meaning.

``Narrow meaning'' denotes the {\it internal\/} set of properties that
we associate with something.  A narrow content is equivalent to a
``word'' in Mentalese.  Narrow meaning places the limit on our ability
to understand the external world.  Our actions are based primarily on
our narrow-meaning interpretation of the ``world outside.''  Two
individuals don't have to have identical or even compatible narrow
meanings for the same term.

``Broad meaning'' is almost completely {\it external.\/} It denotes the
real-world reference, a pointer to a somewhat metaphysical ``hidden
scientific essence.''  Broad meanings are a basis for language: if
each word didn't denote a broad meaning shared between the people
using the language, communicatin would be impossible.

\problem4
Putnam attacks the Conceptual Role Semantics in two fundamental ways.
First of his arguments is that CRS does not really serve well to fix
the meanings of words.  He points out examples of problems with
syntactical determination of meaning, and asserts that even when
meaning {\it is\/} largely syntactically determined, it is not
exclusively the product conceptual meaning.

His other, and in my opinion more important, objection is that
determining the narrow meanings of words {\it cannot\/} be done by a
purely syntactical system.  He points out that meanings {\it are\/}
connected to conceptual roles of words, but conceptual roles in a
very loose, nonsyntactic sense.

I mostly agree with Putnam's reasoning, and I believe this conclusion
is true. 

There {\it can\/} be purely syntactical models of language, and they can
definitely serve as a basis for quasi-intelligent machines.  But they
will be devoid of meaning.  I believe that machine intelligence is
possible, but not by sheer syntactical symbol manipulation.

\end

