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Re: What is truth anyways? was: Re: MISC: Internet Media Type registration: proposed TAG finding

From: patrick hayes <phayes@ai.uwf.edu>
Date: Wed, 12 Jun 2002 14:49:59 -0500
Message-Id: <p05111a0eb92d4e9f819e@[65.217.30.94]>
To: Jim Hendler <hendler@cs.umd.edu>
Cc: www-rdf-logic@w3.org

>>>What
>>>is the harm in being so draconian in how we define truth?
>>>
>>>Isn't that how the internet works ... let a thousand flowers bloom ... and
>>>so why not allow a thousand truths?
>>
>>OK, provided you agree that when the ATM talks to the bank and 
>>credit union computers, and those computers talk to the IRS 
>>computers, and they all use their own notions of truth, that you 
>>are happy with what happens to your bank account. And then of 
>>course there are the FBI computers and the NIMA computers....
>
>
>Interesting Pat, so you're saying that when I stick my little 
>plastic card into the Automated teller in Italy, and it hands me 
>Euros charging an appropriate exchange rate against my machine in 
>the US, that they are using a formal model theory to make it work

No, Im not saying that. In fact I have never, at any time, suggested 
that the computers will be USING a formal model theory. What I do 
however insist on is that they are built using conventions that are 
based on a pretty sharply defined set of mutually agreed conceptions 
of what it is that the programs are talking to one another about, and 
that model theory is one very good way to make such conceptions 
precise.

Further to that point, the vision of the semantic web is that these 
machines will be drawing conclusions, and publishing conclusions 
which are then used by other machines, and so on, so that the final 
content that is an integral part of what causes the ATM to either 
give or not give me some hard cash will have been derived by what 
could be quite a long chain of inference from anything written by a 
human being; and moreover a whole lot of different machines, in 
different places, will have contributed to the chain of inference 
that finally produces the conclusion that determines whether or not I 
get my money. Under these circumstances, the idea of letting a 
thousand flowers bloom about what counts as 'truth' is rather risky, 
seems to me. I would much prefer it if they all conformed to a common 
set of conventions about what counts as an assertion, a proof, 
consistency, and so on. And a model theory is just a way to give a 
precise statement of those conventions. (It has the advantage over 
some other ways that it is independent of any particular formalism, 
so that it is, ironically, *more* like a social agreement - about how 
to connect the formalism to a world - than a translation into another 
formalism would be.)

>-- can you show it to me??

Well, actually, I could, although I bet you wouldn't think much of 
it. A lot of what goes on in bank computers right now involves 
database searches, and databases are indeed based on a semantics that 
can be expressed model-theoretically.

>  err, perhaps sometimes you underestimate what can be done with 
>"social agreements" instead of pure logic...

I don't think I do. But your phrasing here is revealing. Why do you 
*contrast* social agreements with logic? Hasnt it ever occurred to 
you that human society uses logic all the time? That every time 
people talk or think, that they are using logic? That when you and I 
argue, our mutual understanding depends, in part , on our having a 
shared logic - we both know what 'and' and 'or' and 'not' and 'all' 
mean, pretty much; and if we didn't, then we wouldn't be able to 
communicate. I know you know the Talmud, so this shouldn't come as a 
surprise, surely. Of course we humans aren't using *formal* logic, 
but formal logic is only a distillation of whatever it is that we do 
when we use these words, a distillation that we know how to install 
into computers.

I know you have a built-in aversion to anything called "logic". This 
is a problem that you  need to come to terms with, and I sincerely 
hope that you eventually manage to work your way through it. However, 
in the meantime, I still want my bank to use software that conforms 
to a very carefully checked protocol for transmitting 
machine-readable content. If you have found a better way to be 
precise about meaning, by all means put it forward as a suggestion; 
but for Gods sake don't imply that "social agreements" must be 
expressed in poetry and metaphor, and therefore the computers can all 
make up their own minds about whether it is true that
Overdrawn PatHayes _:x .
_:x date "6_12_02" .

Pat
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Received on Wednesday, 12 June 2002 15:50:04 GMT

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