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Re: [ontolog-forum] Ontology, Information Models and the 'Real World': C

To: Ingvar Johansson <ingvar.johansson@xxxxxxxxxxxxxxxxxxxxxx>
Cc: "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Tue, 29 May 2007 19:29:47 -0700
Message-id: <p06230921c2825d6bda31@[]>
>John F. Sowa schrieb:
>>  Wacek and Ingvar,
>>  It happens that English has no tenseless verb forms.
>>  In predicate calculus, you could write:
>>      ~(Ex)(rose(x) & blue(x)).
>>  This statement has no reference to any time or place.
>>  In English, it is possible to make a statement without
>>  reference to place, but not to time.
>And isn't this the reason why Quine introduced his notion of 'eternal
>sentence'? And propositions expressed by eternal sentences cannot change
>truth-values, can they?
>>  vQ> The sentence "no roses are blue" was true some time ago,
>>   > and is false now;  but does it correspond to the same
>>   > proposition in both cases?
>>  I would like to express the proposition stated by the
>>  above formula in predicate calculus.  That statement
>>  is independent of any time, place, or context.  The
>>  proposition it states has no unbound variables that
>>  could be bound, explicitly or implicitly, to any context.
>>  Yet that proposition can have different truth values
>>  in different contexts despite the fact that its meaning
>>  does not change.
>Are you denying the old truth: 'same meaning, same reference'?    (01)

Yes. The whole point of introducing 'contexts' is 
to provide for alternative views of what is true 
and what is not. The very same proposition may, 
in another context, have a different truthvalue. 
That is not to say it ACTUALLY has that 
truth-value: the ACTUAL truthvalue of any 
proposition is a given. But there is some utility 
in allowing the existence of entities which 
correspond to alternative ways the world might be 
(it allows one to reason about counterfactual or 
fictional circumstances, for example.) And when 
one does allow such things, it is pointless to 
insist that they must correspond to the way 
things actually are. So, we allow that a 
proposition may have a different truthvalue "in" 
a context than it has in fact. This does not 
actually make its truthvalue different from what 
it is, it simply introduces a new notion of 
truth-in-a-context.    (02)

Pat    (03)

>  To me,
>this truth implies 'same proposition, same aboutness', which you are
>>  IJ> I would say that there is only one *sentence meaning*
>>   > "no roses are blue", but two *used sentence meanings* and
>>   > two propositions, one which is true and one which is false.
>>   > Propositions cannot change truth-values.
>>  I would identify 'sentence meaning' with 'proposition'.
>>  Then you could apply the word 'used' to either one, if you
>>  like.  I wouldn't say that propositions or sentence meanings
>>  change -- they just represent configurations of individuals,
>>  properties, and relations, real or hypothetical.  But they
>>  can be used for different purposes.
>>  vQ> Note that I do not argue for this or other theory of
>>   > propositions;  I am just curious, and it seems to be
>>   > an issue that should not be just neglected (e.g., for
>>   > the purpose of precise documentation of IKL, a very
>>   > practical task).
>>  Since IKL (like predicate calculus and conceptual graphs) has
>>  no default tenses, it has no implicit context dependencies.
>>  vQ> As above;  if a proposition is fixed to a fact, it cannot
>>   > be refixed to another fact -- or would this be what you suggest?
>>   > If the fact is (was) that Osama slept at t1, the proposition
>>   > that Osama slept at t1 was true, remains true, and will always
>>   > be true.
>>  That raises some important questions:
>>    1. What is a fact?
>>    2. What are the references in a proposition bound to?
>>       To individuals in a particular fact?  To individuals
>>       independent of any specific fact?  Or to configurations
>>       of individuals, which may be considered independently
>>       of any specific binding?
>>  I would claim that facts (at least facts about the world,
>>  not facts such as 2+2=4) are bound to specific chunks of
>>  space-time.
>  >
>>  But I would say that propositions are abstractions about
>>  configurations, which could characterize different facts in
>>  different contexts.  If a proposition names an individual,
>>  such as Osama or Bob, it is not necessarily bound to a
>>  particular fact in which that individual participates.
>>  For example, you might ask "How often did Bob wake up last night?"
>>  To answer that question, I would consider the proposition that
>>  Bob wakes up and try to determine how many times the corresponding
>>  configuration was a correct characterization.  (Perhaps Bob fell
>>  asleep in front of his web cam, which was on for the whole night.)
>>  I could answer that by checking each event in the record for which
>>  the configuration of Bob waking up occurred.
>>  An interpretation of that kind is required to support hypothetical
>>  statements, which may refer to actual individuals.  For example:
>>      If Gerald Ford had been elected president in 1976,
>>      Ronald Reagan would not have been elected president in 1980.
>>  That counterfactual statement refers to actual individuals and
>>  possible outcomes of actual events.  Both of the propositions
>>  in the antecedent and the consequent could be translated to
>>  different languages while retaining the same meaning, but there
>>  are no facts to which either of the propositions could be bound.
>>  This interpretation is consistent with the claim that a proposition
>>  represents an abstract configuration, which might include references
>>  to actual individuals independent of any specific facts in which
>>  those individuals participate.
>>  John
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>Ingvar Johansson
>IFOMIS, Saarland University
>      home site: http://ifomis.org/
>      personal home site:
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>    (04)

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