Derek Zahn wrote:
Related obliquely to the discussion about pattern discovery
algorithms.... What is a symbol?
I am not sure that I am using the words in this post in exactly the same
way they are normally used by cognitive scientists; to the extent that
causes confusion, I'm sorry. I'd rather use words in their strict
conventional sense but I do not fully understand what that is. These
thoughts are fuzzier than I'd like; if I was better at de-fuzzifying
them I might be a pro instead of an amateur!
Proposition: a "symbol" is a token with both denotative and
model-theoretic semantics.
The denotative semantacs are what makes a symbol refer to something or
"be about" something. The model-theoretic semantics allow symbol
processing operations to occur (such as reasoning).
These are deep waters, methinks. Model-theoretic semantics refer to
"objects" that are assumed to exist as functions on possible worlds, so
how would you couple that up to a denotational semantics without getting
into a complicated fight between the two different ways of carving the
world up into entities. What would compel them to point to the same things?
Richard Loosemore
I believe this is a somewhat more restrictive use of the word "symbol"
than is necessarily implied by Newell and Simon in the Physical Symbol
System Hypothesis, but my aim is engineering rather than philosophy.
I'm actually somewhat skeptical that human beings use symbols in this
sense for much of our cognition. We appear to be a million times better
at it than any other animal, and that is the special thing that makes us
so great, but we still aren't very good at it. However, most of the
things we want to build AGI *for* require us to greatly expand the
symbol processing capabilities of mere humans. I think we're mostly
interested in building artificial scientists and engineers rather than
artificial musicians. Since computer programs, engineering drawings,
and physics theories are explicitly symbolic constructs, we're more
interested in effectively creating symbols than in the totality of the
murky "subsymbolic" world supporting it. To what extent can we separate
them? I wish I knew.
In this view, "subsymbolic" simply refers to tokens that lack some of
the features of symbols. For example, a representation of a pixel from
a camera has clear denotational semantics but it is not elaborated as
well as a better symbol would be ("the light coming from direction A at
time B" is not as useful as "the light reflecting off of Fred's pinky
fingernail"). Similarly, and more importantly, subsymbolic products of
sensory systems lack useful model-theoretic semantics. The "origin of
symbols" problem involves how those semantics arise -- and to me it's
the most interesting piece of the AGI puzzle.
Is anybody else interested in this kind of question, or am I simply
inventing issues that are not meaningful and useful?
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