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From: roelw@cs.vu.nl
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Subject: Chinese room argument
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Date: 27 Mar 89 11:01:37 GMT
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In <4532@pt.cs.cmu.edu>, kck@g.gp.cs.cmu.edu (Karl Kluge) writes:

>What do you mean by "knowing the denotations of the symbols it
>manipulates",

By "symbol" I mean any abstract or concrete entity which 1. is
distniguishable from other entities and 2. can be mechanically
recognized as being the same symbol every time it occurs. This
last requirement assumes that there is a distinction between a
symbol and its occurrences, and that no human faculty is needed
to classify occurrences as occurrences of the same symbol. By the
"denotation" of a symbol I mean an abstract or concrete entity
which is assigned to the symbol. This is in itself a meaningless
exercise, but acquires meaning from a context such as proving
program correctness or formally proving a theorem. The assignment
of a denotation to a symbol can be formalized as a mathematical
function; given a set SYM of symbols and a set DEN of possible
denotations we can specify any function in [SYM -> DEN] as
denotation function.

"Knowledge" is not formally defined in my statement; but we have
some knowledge of what it means, from first-hand experience,
psychological theory, etc. What I mean by my statement is that
with respect to the symbols it manipulates, a computer is in the
position of a human being who manipulates symbols on a piece of
paper without knowing "the" denotation of these symbols. More
precisely: 
1. I assume "knowing" means something for human beings, although
we cannot say precisely what it means; 
2. I don't assume that the computer "knows" something in the same
sense that the human being knows something (versus assuming that
the computer cannot know anything, for that is what I want to
show, whithout assuming it); 
3. a computation is a symbol manipulation for which a denotation
function has been selected; if the computation is sound, the
output has a denotation if the input has; 
4. the human being need not be aware of the denotation function
selected in order to carry out the symbol manipulation;
5. so it may be possible to interpret a single symbol-
manipulating process as a computation of an answer to a Chinese
question and, using a different denotation function, as the
computation of the solution to a differential equation, and,
using a different function again, as the computation of the
square root of a number. This is only imposible for those symbol-
manipulations for which it can be proven that there is only one
denotation function for which the computation is sound. (Cf.
Reiter's closed-world hypotheses for databases, which restrict
the set of possible models of the theory to a singleton set of 1
model).

Given this independence of syntac and semantics, there is no
sense in which a computer can "know" the denotations of the
symbols it manipulates; simply because in general is not a single
priviliged denotation. (Reiter's closed-world DB's are hardly a
candidate for thinking computers).

The hard part is how a denotation function of a set of symbols
links with our ability to think and know things. I have nothing
to say about that, except that the onus of proof (or plausible
argument) is on those who say that we think by manipulating
symbols.

Note that of the set DEN is again a set of symbols, we can define
the denotation function formally and even store (a finite part
of) it in a computer and manipulate it. This is what a computer
actually does. This shifts the problem to what the denotation of
the symbols in DEN is. I am not convinced that symbol grounding
is at all the answer for a machine to transcend symbol-
manipulation. The letters I know type are symbols which are
stored in a computer and manipulated on the basis of their
syntactic (and physically recognizable) form. They are grounded
in my hitting certain physical keys, but this does not make my
computer intelligent.

I don't think proof is attainable here. The error may be that the
desire to prove things may cloud the view of the possibility that
rational argument is possible outside the realm of provable
statements, and this clouding may open the way for irrationality.

> If we can agree that people can "think" without "knowing" the
> notations of the symbols they use (regardless of whether people
> are "symbols all the way down"), then why is the ability of a
> TM to "know" the denotations of its symbols relevent to the
> question of whether it can think?

The question is whether people think by manipulating symbols. If
so, then we may ask whether they can do so without knowing the
denotation of these symbols. (presumably yes, for we are not
aware of manipulating symbols when thinking). Not assuming that
people are symbols all the way down, let's take an
uncontroversial example: a mathematician rehearsing a proof s/he
is going to explain for a class. Can s/he do this whithout
knowing what the symbols stand for? I would say not. But I agree
that this is not a proof that s/he does not actually manipulate
symbols "all the way down" without knowing their denotation.
Neither do I think such a proof is possible, or required.

> I don't understand your concern about the system's "knowing"
> this arbitrary property, [the denotation of a symbol] when it
> can (by hypothesis) do all the right things in terms of
> interacting with the world without "knowing"/representing this
> property.

I am concerned with the independence of syntax from
(denotational) semantics because I think that it the crux of
Searle's argument. However, Searle's argument is not a proof and
many people are not convinced (let alone converted) by it. (It
would almost be a contradiction in terms if it were a proof, for
then it would be formalizable, and hence verifiable by a
computer).

I am more concerned however with the tendency to identify thought
with the capability to causally interact with the world in the
proper way. "The proper way" is often taken to mean
"indistinguishable from the way human beings interact." This last
assumption is made in the Turing test (in any of its forms). I
disagree with this on two points:
1. There is more to human thought than causal interaction with
the world. To demand that everything that exists must be
describable as causal interaction is a form of philosophical
idealism, for it is the requirement that what exists must be
knowable in a certain way. There is no reason the universe should
be constituted such that we, insignificant parts of it, can know
it in a certain way. This does not mean that the drive to explain
events causally is bad, or wrong, etc., just that it has limits,
and the explanation of human subjectivity may be one of those
limits. I agree mostly with Thomas Nagel's book "The View From
Nowhere" on this (Oxford UP 1986). See also his "What is it like
to be a bat", reprinted in "Mortal Questions," Cambridge UP,
1979, 165-180.
2. To interpret "the proper way of interacting with the world"
with "acting indistinguishably from human beings" is to confuse
ontology with epistemology. Searle also say as much; the question
is not how we know that a person things, nor how we can logically
or empirically justify such knowledge claims, but what it is we
ascribe to a person when we say that s/he thinks.

Roel Wieringa