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From: harnad@mind.UUCP (Stevan Harnad)
Newsgroups: net.ai,net.cog-eng
Subject: Re: Searle, Turing, Symbols, Categories
Message-ID: <166@mind.UUCP>
Date: Fri, 10-Oct-86 09:47:46 EDT
Article-I.D.: mind.166
Posted: Fri Oct 10 09:47:46 1986
Date-Received: Sat, 11-Oct-86 19:43:08 EDT
References: <158@mind.UUCP> <150@cwrudg.UUCP> <160@mind.UUCP> <4865@ukmf.ukma.uky.csnet>
Organization: Cognitive Science, Princeton University
Lines: 65
Keywords: Robotics, Symbol-Crunching, Category Representation, Analog Representation, Induction
Summary: Symbols vs "Symbols": The symbolic/nonsymbolic distinction is not clarified by nonliteral use of the terms
Xref: mnetor net.ai:1182 net.cog-eng:281

In response to what I wrote in article <160@mind.UUCP>, namely:

>On my argument the distinction between the two versions
>[of the turing test] is critical,
>because the linguistic version can (in principle) be accomplished by
>nothing but symbols-in/symbols-out (and symbols in between) whereas
>the robotic version necessarily calls for non-symbolic processes
>(transducer, effector, analog and A/D).

Drew Lawson replies:

>	This is not clear.  When I look at my surroundings, you are no
>	more than a symbol (just as is anything outside of my being).
>	Remember that "symbol" is not rigidly defined most of the time.
>	When I recognize the symbol of a car heading toward me, I respond
>	by moving out of the way.  This is not essentially different from
>	a linguistic system recognizing a symbol and responding with another
>	symbol.

It's important, when talking about what is and is not a symbol, to
speak literally and not symbolically. What I mean by a symbol is an
arbitrary formal token, physically instantiated in some way (e.g., as
a mark on a piece of paper or the state of a 0/1 circuit in a
machine) and manipulated according to certain formal rules. The
critical thing is that the rules are syntactic, that is, the symbol is
manipulated on the basis of its shape only -- which is arbitrary,
apart from the role it plays in the formal conventions of the syntax
in question. The symbol is not manipulated in virtue of its "meaning."
Its meaning is simply an interpretation we attach to the formal
goings-on. Nor is it manipulated in virtue of a relation of
resemblance to whatever "objects" it may stand for in the outside
world, or in virtue of any causal connection with them. Those
relations are likewise mediated only by our interpretations.

This is why the distinction between symbolic and nonsymbolic processes
in cognition (and robotics) is so important. It will not do to simply
wax figurative on what counts as a symbol. If I'm allowed to use the
word metaphorically, of course everything's a "symbol." But if I stick
to a specific, physically realizable sense of the word, then it
becomes a profound theoretical problem just exactly how I (or any
device) can recognize you, or a car, or anything else, and how I (or it)
can interact with such external objects robotically. And the burden of
my paper is to show that this capacity depends crucially on nonsymbolic
processes.

Finally, apart from the temptation to lapse into metaphor about
"symbols," there is also the everpresent lure of phenomenology in
contemplating such matters. For, apart from my robotic capacity to
interact with objects in the world -- to recognize them, manipulate
them, name them, describe them -- there is also my concsiousness: My
subjective sense, accompanying all these capacities, of what it's
like (qualitatively) to recognize, manipulate, etc. That, as I argue
in another paper (and only hint at in the two under discussion), is a
problem that we'd do best to steer clear of in AI, robotics and
cognitive modeling, at least for the time being. We already have our hands
full coming up with a model that can successfully pass the (robotic
and/or linguistic) turing test -- i.e., perform exactly AS IF it had
subjective experiences, the way we do, while it successfully accomplishes
all those clever things. Until we manage that, let's not worry too much
about whether the outcome will indeed be merely "as if." Overinterpreting
our tools phenomenologically is just as unproductive as overinterpreting them
metaphorically.

Stevan Harnad
princeton!mind!harnad