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Article 4445 of comp.ai.philosophy:
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>From: santas@inf.ethz.ch (Philip Santas)
Newsgroups: comp.ai.philosophy
Subject: Re: Definition of understanding
Message-ID: <1992Mar13.143003.26132@neptune.inf.ethz.ch>
Date: 13 Mar 92 14:30:03 GMT
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In article <1992Mar12.233945.9244@psych.toronto.edu> michael@psych.toronto.edu (Michael Gemar) writes:
> santas@inf.ethz.ch (Philip Santas) writes:

MG:
>>>PE = 1/2 k x^2
>>>where PE = potential energy
>>>       k = spring constant
>>>       x = displacement from equilibrium
>>>How do you give definitions that have semantic content to a computer?
>>>How does it know that when you respond to the request "Please input
>>>the capacitance constant => " that you are talking about capacitance,
>>>and not number of cars?  The problem of generating "definitions" with
>>>semantic content for a computer *is* the central problem under discussion.

PS:
>>You can do type checking even statically in this example:
>>  PE GivePE(Distance displacementFromEquilibrium){
>>           Distance x = displacementFromEquilibrium;
>>           SpringConstantType k = SpringConstant;    // global variable
>>           return (1/2) * k * power(x,2); };
>>Relevant things can be done for capacitances, by changing the type
>>of the argument displacementFromEquilibrium.

MG:
>This does *not* ground the meaning of these terms.  How do these variables
>know that the numbers input are spring constant and displacement, rather
>than capacitance and potential.  Merely typing

PS:
>>Because of their type; there is a type differentiation.

MG:
>But there is no connection to what they *refer* to.  Sure they're

They can refer to another Type, to another Set of objects, to Text, to 
a space in the memory, to a drive, to sound, and whatever you want.

MG:
>differentiated, but there is nothing in the computer to say that they
>refer to distance and spring constants as opposed to potential and
>capacitance, or apples and oranges.  Just naming the type "Spring Constant"
>doesn't do squat.
>Distance x = displacmentFromEquilibrium
>does not tell the computer what "distance" and "displacement from equilibrium"
>*is*!  I could have just as easily typed:
>Qaatlus x = GwornsBleebArack
>and the program would *still* compute *both* Potential *and* electrostatic
>energy.

PS:
>>Notice that there are many human languages and you can say the same thing
>>with differnt words and syntax. What I do not understand is how can a
>>you calculate two irrelevant things by evaluating just one function.

This question remains unanswered from your side.
If there is differentiation in types, then there can be differentiation
in the functions accepted by these types. Notice that type information
is just one form of information: there are some more like membership,
satisfaction of inequalities etc. that help us to deal with well defined
and bad defined (although not all levels) of concepts. Research and
engineering methods can contribute a lot to the way such things are
modelled, implemented and evaluated.

PS:
>>The computer in my example has an internal representation for the type
>>Distance. This representation can be enriched for the purposes of more
>>complex tasks. What is YOUR internal representation of Distance?
>>What do you understand under the terms 'Distance from Sun to Star A' or
>>'speed of light'?

MG:
>I have a *lot* more than just a variable marked "distance".  I understand
>how distance relates to two points, how distance can be calculated, how
>the term "distance" can be used metaphorically, how distance can be
>measured, etc.  Your program only knows that it has a variable labelled
>with the characters "d", "i", "s", "t", "a", "n", "c", and "e".  This simply
>ain't the same thing.

You mix variables with types and other information related with them.
If your variable is of type Dinstance, it cannot be of type Resistance
except if you have created a relationship between these types (something
obvious for types Distance and Magnitude). Notice that such relationships
can be created dynamically, by mking the computer gathering statistical
data about their usages, etc.

MG:
>C++ may have the ability to distinguish between different variables.  It
>does *not* have the ability to provide semantics for those variables.

Their membership to a class (or type, or set), their sharing of functions
and other variables etc is a form of semantics. Such information is very
important for a program to run, as it is for a human to survive.

PS:
>>In many computer languages you have the ability to define data types,
>>relationships among them, rules, constraints and many other elements.

MG:
>All of these relations, rules, and constraints are *syntactic* ones.  They
>do not give *meaning* to the symbols, as the variables are not grounded
>in any way.  This is a point that has been batted back and forth a number
>of times.  If you don't buy it, then fine, but I'm not sure we can make
>any other progress then.

What do you mean by "meaning to the symbols"? This is a crucial problem
I suppose.

PS:
>>Are you aware of the semantical instantiation in a human brain?
>>If yes why is it impossible to implement this in a machine?
>>If no why do you argue against the abilities of these building blocks
>>for modelling semantics?

MG:
>You don't have to know how something's done to know how something *isn't*
>done.  There is a principled argument why shuffling symbols won't give
>you meaning, namely, that syntax can't alone produce semantics.  Even though
>I don't know how semantics *does* work, I know it *doesn't* work through
>shuffling symbols.

Sometimes you have to know. Imagine the case of a man painted in blue.
A small kid may say: "this is not a man", but she cannot define what it is.
Of course, a blue creature that looks like a non-man can be reduced to
a man. The same holds for the structure of the mind and semantics..

>In order to save bandwidth (and to make Chalmers happy :-) I'd like to
>suggest that if you understand the above claim, but don't believe it, then
>simply post so once to state your position, and we'll leave it at that.  There
>is no point in us exchanging articles back and forth if we've reached
>disagreement over first principles.

It is not a matter of belief, but of logical argumentation, search for
rational possibilities, and rejection of contradictions...

Philip Santas

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email: santas@inf.ethz.ch				 Philip Santas
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