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Article 5764 of comp.ai.philosophy:
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>From: harnad@shine.Princeton.EDU (Stevan Harnad)
Newsgroups: comp.ai.philosophy
Subject: Re: Grounding: Virtual vs. Real
Summary: Reply to Throop and Gemar; P.S. to Minsky
Keywords: transduction, analog
Message-ID: <1992May20.034459.8223@Princeton.EDU>
Date: 20 May 92 03:44:59 GMT
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In article <60703@aurs01.UUCP> throop@aurs01.UUCP (Wayne Throop) writes:

>Consider a robot interacting and demonstrating competence against a
>virtual world, and another robot interacting and demonstrating
>competence against the real world.  The two robots will (by hypothesis)
>end up in identical physical states, yet one "has semantics" and the
>other doesn't.

Just three important points to keep in mind and then the point of
grounding and the TTT is easily seen: (1) Transduction must be real,
(2) it is part of of the robot's internal functioning, and (3) how much
of the rest of the robot's internal functioning is likewise analog
rather than computational is moot (and certainly cannot be presupposed
without begging the question).

Now:

A real person whose real senses interact with computer-generated
sensory input rather than real-world input is still grounded (because
people's brains are grounded and the person could just as well pass
the TTT with natural or synthetic sensory input).

Exactly the same is true of a real TTT-capable robot in the same
situation(s). The grounding still comes from its REAL TTT-passing
capacity, not from the source of its sensory stimulation (but the
sensory stimulation must be real stimulation, i.e., real transduction).

A computer, on the other hand, subdivided into a part that simulates
a robot symbolically and a part that simulates the world symbolically
is NOT grounded because it is not doing real transduction and could
not pass the TTT. This is true even if the simulation contains
all the necessary information out of which we could implement
the requisite transducers and build the real robot that really would
pass the TTT: That robot (once built) would be grounded, but the
simulation on which it was based in every nontrivial respect was not
grounded -- despite being a simulation that could correctly
second-guess its every move in response to any real-world contingency
second-guessed in its world-simulation!

This should be no more difficult to understand than the fact
that real flying, like real TTT-passing, requires "transducers"
to deal with the air, etc., and even if a flight simulation
were so complete that it contained every piece of nontrivial
information needed to design and build a plane that actually
flew, the simulation does not fly.
---------------------------------------------------------
PS In response to Marvin Minsky: I, at least, don't think
real-time history or development is at all critical to
grounding. A robot could spring fully formed out of the
head of Zeus and if it had full TTT capacity, it would be
grounded.

And in response to another poster who thought that discrete
versus continuous physics might have something to do with it:
It doesn't. Even if the the real world is discrete, that doesn't
make it just implemented symbol manipulation (computation).
-- 
Stevan Harnad  Department of Psychology  Princeton University
harnad@clarity.princeton.edu / harnad@pucc.bitnet / srh@flash.bellcore.com 
harnad@learning.siemens.com / harnad@elbereth.rutgers.edu / (609)-921-7771


