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

To: Waclaw Kusnierczyk <Waclaw.Marcin.Kusnierczyk@xxxxxxxxxxx>
Cc: "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Pat Hayes <phayes@xxxxxxx>
Date: Mon, 28 May 2007 20:59:56 -0700
Message-id: <p0623090cc2815118fecc@[]>
>>  In that sense, its meaning (and also its truth or
>>  falsity) also would not actually change over time, if one includes a
>>  temporal referent as part of the (implicit, at least) meaning of the
>>  proposition - but the meaning interpreted by perceivers over time might
>>  change as the context of their interpretation changes, just as the
>>  meaning interpreted by different interpreters (including the proposer)
>>  might vary at the same time.
>>  If one allows the actual temporal referent to change with time (e.g. an
>>  explicit or implicit "now" is always the time at which the proposition
>>  is interpreted), then the meaning implicitly changes with time, as can
>>  the truth or falsity.
>This encourages me to ask another question:  do propositions involve
>indexicals?  (Would there be proposition-indexicals?)  Does the
>statement 'he is wise' correspond to a (number of) proposition(s) about
>a particular individual at a particular time each, or can it correspond
>to a proposition which still does not have the 'he'-part resolved?
>Can we talk about the proposition denoted by the 'he is wise' statement
>without resolving the indexical first?    (01)

Let me respond to this question from the IKL 
point of view, as it - the question - touches on 
a central point in the design of our formalism, 
and one that produced a lot of controversy in the 
design process (and indeed remains controversial).    (02)

The IKL answer to the above questions is a firm 
'no'. Propositions are not indexical or 
parameterized in any way. They are not sentences, 
which must be interpreted differently when the 
names which occur in them (actually, occur free 
in them) are reinterpreted. A proposition in IKL 
is an object which simply has a truth-value: it 
is a 'bearer of truth'. Formally, in fact, it is 
indistinguishable from a relation with no 
arguments, and the IKL model theory treats them 
exactly in that way. It is not itself subject to 
linguistic interpretation: it is the result of a 
certain kind of linguistic interpretation 
process. So all 'contextual' matters, including 
any indexicality in the sentence which is being 
used to express the proposition in English (IKL 
itself has no indexicals), is understood to have 
been resolved by some process of translation from 
English into IKL. One cannot express "He is 
wealthy" in IKL, but one can express the 
proposition intended by a particular use of that 
indexical sentence (say, as a reply to the 
question "Is Bill Gates a rich man?", or when 
spoken while pointing to someone physically 
present and known to the hearer) by something 
like the IKL sentence (Wealthy BillGates), ie by 
the use of a name for the person identified. 
Another way of putting it is to say that all 
propositions are about some thing or things: they 
are already attached to the referents of the 
names in the sentence, not to the names 
themselves. Yet another way to say it is to say 
that a proposition is like a sentence but with 
all its free names (and indexicals) already 
interpreted to refer to things. This has the 
consequence that propositional expressions are 
referentially transparent in IKL, so we had to 
invent an 'opaque name' construction to capture 
the intended meaning of opaque contexts.    (03)

My favorite example of an implicit indexical, by 
the way, is the highway warning signs in New 
Mexico, which say "Gusty Winds May Exist". 
Understood indexically, the intended meaning is 
that such winds may be present near the sign at 
the time you are reading it. Understood strictly 
as written in IKL mode, however, they are a 
surprisingly cautious statement in philosophical 
ontology. But then of course NM is a rather blue 
state.    (04)

Pat Hayes    (05)

>>  It's hard for me to imagine a case in which the truth or falsity of a
>>  proposition that has a clear implicit or explicit time referent in its
>>  meaning can change without its meaning changing, since its
>  > correspondence with reality (including a time referent) should not
>>  change. Reality should not change, except with time, which would be
>>  covered by the time referent in the meaning of the proposition.
>It is not only time that can be referred to by indexicals.  the
>statement 'he is wise' may be (correctly interpreted as) true or false
>at the same time, depending on whom 'he' refers to.
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