Instituut voor Taal- en Kennistechnologie
Institute for Language Technology and Artificial Intelligence
Roitblat's understanding of all the elements in this discussion
differs so radically from my own that space forces me to leave the
reader to adjudicate our difference. All I can do is itemize some of
our most prominent differences:
- For me, obeying differential equations is physics and
implementing symbol manipulations is computation. They are not the
same kind of thing, and indeed, the difference between them, the
hardware/software distinction, is what most of this discussion is
about. (Nor, as far as I can see, does this have anything to do with
the psychologists' hoary example (which is often cited to illustrate
one insight or another, but has not yet led to any concrete results)
that the dog (somehow) correctly estimates the trajectory of the
frisby without doing a conscious calculation.)
- Nor, from the equally venerable platitude that continuous
signals can be approximated arbitrarily closely by discrete ones, does
it follow that virtual objects are approximately real: Tighten the
approximation as close as you like, a simulated waterfall will never
be wet. Roitblat seems to conflate discrete approximation of
continuous signals -- a transducer function -- with systematically
interpretable symbolic representation (see Harnad 1987).
- Roitblat seems to think grounding has to do with ``specifying
the premises of formal arguments.'' I cannot see this it all; it has
to do with connecting symbols to what they are about by means other
than an external interpretation: my candidate is causal grounding via
whatever internal resources it takes to pass the TTT.
- Roitblat seems to be using the words ``syntax,''
``systematicity,'' and and especially ``semantics'' very differently
from the way I do. I think my usage is more standard (e.g., see Fodor
& Pylyshyn 1988), but let the reader judge.
- We also differ in our construal of the Chinese Gym and Chinese
Room Arguments, for which I can only refer the reader to the target
article and the original sources (Searle 1980, Harnad 1989 Harnad
1990a) for comparison.