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

To: ontolog-forum@xxxxxxxxxxxxxxxx
From: KCliffer@xxxxxxx
Date: Wed, 30 May 2007 07:28:18 EDT
Message-id: <c64.14a8cdbe.338eb9d2@xxxxxxx>
I think I agree with Waclaw, and also with Ingvar's recent comments.
It seems that the statement "p is true in context C" would be true under Pat's consideration, even though p is, in fact false, in context "reality". This, as I think Waclaw implies, becomes awkward, even if understandable after considerable explanation. It would make more sense to me to include the context as a part of the proposition, perhaps implicit (but more usefully to be made explicit), to be able to allow a proposition to have an unequivocal truth value (even if it's a truthlikeness other than fully true or false), just as a proposition stated in the present tense can be seen to have an implicit context of the time it is stated as part of its meaning. In that sense, a change in context BECOMES a change in meaning of a proposition, which allows (preserves the ability for) one to consider the truth value of the full proposition's meaning (i.e. of the proposition, including the context that is an implicit or explicit part of the proposition) to be invariable. A proposition that can change meaning in different contexts would then be a sort of open proposition, without all referents (implicit or explicit) fully defined, without a definable truth value. The propositions full truth-assignable meaning would be defined only in the appropriate context, in which the open proposition becomes "closed" and takes on a truth value, just as a proposition with unspecified indexicals does not have a truth value until the indexicals are specified.
(Please correct terminological issues here, if there are any, with my use of "open," "closed" etc.)
Waclaw.Marcin.Kusnierczyk@xxxxxxxxxxx writes:
Pat Hayes wrote:
>> 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'?
> 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.

From this and the previous explanations, I think I get the point.
Thanks for the explanation, I did get the idea wrong.

Would it not be better to say that a proposition p has a truth-value --
*the* truth-value of p -- which is not context-dependent in any way, but
that in different contexts it may be *said* to have another truth-value?
I think that "we allow that a proposition may have a different
truthvalue "in" a context than it has in fact" and "the very same
proposition may, in another context, have a different truthvalue" would
inevitably be misleading to most users, despite your clear (to me now)
Kenneth Cliffer, Ph.D.

See what's free at AOL.com.

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