X-Message-Number: 4044
Date: Sun, 19 Mar 1995 00:10:19 -0500 (EST)
From: Bruce Zimov <>
Subject: SCI.CRYONICS: Re: Symbols

Donaldson, Ettinger, and others have been perplexed by Mr. Clark's
idiosyncratic definition of a symbol.  It would appear that the
definition, though poorly worded by Mr. Clark, is not at all his fault,
but comes almost entirely from the reference he gave to Godel, Escher,
Bach by Hofstadter. 

GEB p. 349: "Let us from now on refer to these hypothetical neural 
complexes, neural modules, neural packets, multineuron
units....as symbols." 
            "An active symbol is one which has been triggered- that is,
one in which a threshold number of neurons have been caused to fire by
stimuli coming from outside." 

    p. 350 "The high-level description should eliminate all reference to
neurons, and concentrate exclusively on symbols." 

    p. 358 "Then intelligence will have been shown to be a property that
can be 'lifted' right out of the hardware in which it resides- or in other
words, intelligence will be a software property.  This will mean that the
phenomena of consciousness and intelligence are indeed high-level in the
same sense as most other complex phenomena of nature: they have their own
high-level laws which depend on, yet are 'liftable' out of, the lower
levels." 

    p. 385 "There is no reason to expect that 'I', or 'the self' , should
not be represented by a symbol.  In fact, the symbol for the self is
probably the most complex of all the symbols in the brain.  For this
reason, I choose to put it on a new level of hierarchy and call it a
subsystem, rather than a symbol.  To be precise, by 'subsystem', I mean a
constellation of symbols, each of which can be separately activated under
the control of the subsystem itself." 

    p. 387 "A very important side effect of the self-subsystem is that it
can play the role of 'soul',in the following sense:  in communicating
constantly with the rest of the subsystems and symbols in the brain, it
keeps track of what symbols are active, and in what way.  This means that
it has to have symbols for mental activity-in other words, symbols for
symbols, and symbols for actions of symbols." 
             "Of course, this does not elevate consciousness or awareness
to any 'magical', nonphysical level." 

Remarks:  

Since GEB was written in 1979, it predated the work of Rumelhart and 
McClelland in PDP which explained alot of what Hofstadter, coming from 
the traditional Minsky/Papert AI perspective, was overtaxing the concept 
of 'symbol' to do.  The last 10 years of connectionist research in vision 
and other areas stands as a convincing argument that Hofstadter's symbols 
are a historical curiosity at this point.  It is interesting that in the 
quotes above, Hofstadter regards consciousness as 'liftable' but not to 
any abstract nonphysical level.  Going beyond Hoftstadter's views, better 
arguments in the symbolic/ sub-symbolic process debate in AI are found in 
the works of Fodor and Smolensky.  Wilks' conclusion in THE FOUNDATIONS 
OF ARTIFICIAL INTELLIGENCE sound familiar: 

   p.336 "A reasonable intellectual position at this time sould be
charitable and well-disposed agnosticism: one that combines total distrust
of Smolensky and Fodor's demonstrations of the impossibility of each
other's positions, with eager anticipation of news of the performances of
devices."

  No matter who is correct on the symbolic/ sub-symbolic issue
for intelligence, one can see that the 'liftability' of consciousness is a
separate issue, and Hoftstadter, Moravec, et. al. are not justified in
implying an answer to the latter based on arguments for the former.

  Bruce Zimov 

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