🚀 go-pugleaf

Stevan Harnad writes,
> As the mint that coined the term, I think I speak with a little
> semantic authority when I say that that's decidedly *not* the symbol
> grounding problem but rather a symptom of it! Virtual worlds are not
> real worlds, and what goes on inside a simulation is just meaningless
> symbol crunching. The only way to ground symbols is in the real world.
> 
> Let me add the prediction that whereas a "virtual world" may allow one
> to ground a toy robot in the real world, it will never lead to what --
> for a psychobiologist, at any rate -- is the real goal: A robot that
> passes the Total Turing Test. The reason is again the symbol grounding
> problem: Virtual worlds cannot embody all the contingencies of the real
> world, they can only capture as many of them symbolically as we can
> anticipate. In ordinary AI this was known as the "frame" problem -- but
> of course that's just another manifestation of the symbol grounding
> problem.
 
Mr. Harnad, I think you're taking a practical argument and couching it,
misleadingly, in philosophical terms.  Here are three arguments you seem to
be making, and my commentary:

1. Existing symbolic AI systems live in simulated worlds which are a long
   distance away from reality.  The only reason some people think they are
   grounded in reality is because they're projecting.

   [ I agree that the distance to reality is large in most cases. ]

2. It's impractical to produce a simulated world which is a short distance
   from reality.  

   (My definition of "a short distance" would be that, if you were to
   replace the simulation with sensors and effectors which act in the real
   world, the AI system would be able to operate effectively in the real
   world if it does so in the simulation.  The construction of the
   sensors/effectors must not be allowed to hide complexities of the
   problem, of course; the simulation is a "short distance" from reality
   only if the sensor/effector system is a fairly direct translation.)

   [ I think this is a reasonable argument for someone to make, but I disagree
     on empirical grounds: I expect that we will soon see AI systems which
     run equally well on the real world and on fairly-detailed simulations. 

     Right here in our lab at CMU, we run a real robot with an extremely
     simple symbolic AI system.  The abstraction done by the sensor/effector
     system is considerable; I would say that when we decouple our system 
     from reality and run it under the simulation, it is a fairly "large
     distance" from reality, so it isn't a counterexample to claim (2).
     However, it's only a matter of degree, and powerful robotic performance
     systems must decrease that distance in order to be able to fully test
     their systems in simulation.  I believe they will succeed. ]
     
3. No matter what the simulation is, if it's _completely symbolic_, then 
   it's not _grounded_.

   [ This is the philosophical point.  I don't think this matters at all. ]


As a practicing roboticist, it's clear that when I consider an AI system
I should not be asking the question "Is it grounded?" but rather the question
"How interesting is it?", where _interest_ is positively correlated with
_realism_.  That's the way for me to produce good research results.  Asking
this question may lead me to ground my system in the lab, or it may not.

I think it's up to you to give reasons why the AI community should care about
the philosophical issue of _grounding_ rather than the practical issues of
_interest_ and _realism_.  And I think it behooves you to be more careful
to identify which of your arguments are practical and which are philosophical.

If you can't argue that the symbol grounding problem is worth considering 
on practical grounds, you might consider emphasizing your more practical
arguments in this forum.  For instance, if you wish to advocate connectionism,
you might wish to cite the fact that connectionist systems typically have a
"short distance" to reality, and that their _realism_ contributes to their
_interest_.


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 \\\ Marc Ringuette \\\ Carnegie Mellon University, Comp. Sci. Dept. \\\
  \\\ mnr@cs.cmu.edu \\\ Pittsburgh, PA 15213.  Phone 412-268-3728(w) \\\
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