W3C home > Mailing lists > Public > www-rdf-logic@w3.org > April 2001

Re: Reification

From: pat hayes <phayes@ai.uwf.edu>
Date: Wed, 11 Apr 2001 20:14:39 -0500
Message-Id: <v04210119b6f7d6158672@[130.107.66.237]>
To: "Seth Russell" <seth@robustai.net>
Cc: www-rdf-logic@w3.org
>From: "pat hayes" <phayes@ai.uwf.edu>
>
> >From Seth:
> > > > >Maybe that's because open world Truth is impossible too.  Rather
>Truth is
> > > > >relative to [an] active processes. Perhaps the best we can hope for
>is a kind
> > > > >of propositional attitude that each agent calculates for it's self.
>
> > >If someone creates a formal system in which all axioms, syntax, and
> > >operations are specified;  then the statements of such a system can be
> > >considered True\False and we can operate on that state with negation.  I
> > >would call such a system "closed".  The opposite situation is where the
> > >axioms and operations are not all known - perhaps the only thing that is
> > >known is the syntax of the statements.  I would call such a system
>"open".
>
> >From Pat:
> > OK. This is the normal case that formal logic deals with and to which
> > the terms 'true' and 'false' usually apply. If I say that P is true,
> > I havn't thereby said anything about anything else, or claimed that
> > the world is closed or limited in any way other than that P has to be
> > true in it, or pre-empted anything that anyone else might want to say
> > about the world (unless they diasagree with me on this one
> > proposition, of course) . For example, if I say that Foodles exist, I
> > am not saying that nothing but Foodles exist. (I am also not saying
> > that the opposite, by the way: I'm just not saying anything about the
> > rest of the world at all, so it can be anything it wants to be
> > without my claim being false; just so long as it has some Foodles in
> > it.)
>
>Well yes, but if literally all you say is {P is True}, you haven't said
>anything much at all.   Don't you also need to specifiy all of your axioms,
>operations, and syntactic structures before your single statement means
>anything ?

You may have to give more axioms, yes, of course. But that just means 
saying a rather larger P, or asserting a whole lot of P's. That 
doesn't change anything. The more you say, the more you restrain the 
world; that is the very nature of asserting propositions. (That is 
surely WHY we ever assert anything: to express that the world is 
constrained in some way.)
However, you don't need to specify any operations. I'm not sure quite 
what you mean by that word in this context.

>  So I am considering all of that which entails your {P is True}
>closes and restrains your world accordingly.    I had though that was
>necessary for a "formal logic" system to be functional.

Making an assertion does restrain the world, in that it makes some 
claims about the way the word is. But that doesnt 'close' the world 
in any useful sense. In fact it is notoriously difficult to close the 
world using logic: it is impossible to restrict the world to finite 
things, or to the natural numbers, etc..

>Why are you not mentioning that now?
>
> > > In other words Truth in the real world and on the web is
> > >relative.
> >
> > Relative to what?
>
>Relative to an active process (see first message above).

Truth arises from a relationship between expressions and 
interpretations, and has nothing to do with processes.

Pat Hayes

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Received on Thursday, 12 April 2001 11:30:41 GMT

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