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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: Wed, 30 May 2007 13:59:41 -0700
Message-id: <p06230903c28390d0b232@[]>
>John F. Sowa wrote:
>>  Ingvar,
>>  My position and Pat's position are compatible and for the same
>>  reasons:  we both have propositions, but we admit that their
>>  truth values in different contexts can be different.
>One could call it 'hard-headed language puristness', but it seems to me
>that Ingvar makes a valid point (if I understand him correctly);  to me,
>to say (as Pat did) that a proposition has a fixed truth value, which is
>not a function of anything (or is a nullary function), and then to say
>(as Pat did) that a proposition may have different truth values in
>different contexts is plainly confusing.    (01)

What I said is that propositions have fixed 
truthvalues, and that propositions may also stand 
in relations to other entities. One of these 
relations is conventionally denoted by "ist", 
holds between entities called 'contexts' and 
propositions, and is understood - externally to 
the actual logic - to have the interpretation 
that the proposition is 'true in the context'. 
This relationship of truth-in-a-context has 
absolutely no relationship with actual logical 
truth, and is indicated in the formalism simply 
by the ist relation: that is, we say that P is 
'true in C' simply to mean that "ist(C, P)" is 
logically true. Now, perhaps calling this 'having 
a different truth-value in a context' is 
confusing, since this truth-in-a-context is not 
really anything to do with actual truth-values: 
but it is simply an extension of the conventional 
nomenclature. So if you find this awkward, 
abandon this terminology and say instead that P 
is C-true, or something similar, which draws 
attention to the fact (and it is a fact, even in 
a context logic) that truth and C-truth are 
different; and the the latter has a parameter.    (02)

>While in the case of multiple possible worlds -- which seem a purely
>theoretic device that does not reflect the actual reality we live in --
>it does sound reasonable to say that a proposition may have different
>truth values in different worlds, as far as the worlds are truly
>different possible worlds, rather than consequtive stages of the same
>actual world (in which case we would have to admit that the truth of a
>proposition is time-dependent).  But it does not seem to me reasonable
>to say that a proposition may have different truth values in different
>contexts in the same actual world    (03)

My position is that I have no idea what a 
'context' is supposed to be (and I have spent 
more mental hours than I want to admit trying 
find out what others mean by this horribly 
evasive word) and I prefer to do without them 
altogether. There simply is no fact of any matter 
involving the term "context". But if someone 
wishes to speak of truth in a context - and many 
people do - and has some notion of what a context 
might be (and people do use it to mean possible 
worlds, by the way, among many other kinds of 
thing), then the IKL stance and formalism 
provides them with the ability to formalize their 
intuitions by writing axioms about some suitable 
relation between their kind of context and 
propositions. In other words, contexts are hereby 
brought into the scope of ontological 
engineering, rather than being some mysterious 
aspect of truth itself that we must resolve 
before we can even get started.    (04)

>-- especially after having said it has
>a fixed truth value.  It may be that a context considers, in any sense
>you like, a proposition to be true or false, independently of its actual
>truth or falsity, but the proposition does not thereby change its truth
>value.  We end up saying that a proposition is true, but (and?) false in
>some context, for example.  Awkward, as Ken says.    (05)

If you think this is awkward (and I agree) then I 
suggest you would be better off without having 
contexts at all. It is part of the very idea of 
contexts that they can change the meanings of 
things, so that sentences may be true but seem 
false in a context, or vice versa. They are 
inherently <it>de dicto</it>, inherently opaque, 
inherently elusive. Awkward, I agree, but 
awkwardness is inevitable when one sets out to 
write axioms (which are by their nature intended 
to be effectively eternal, or at the least 
long-lived) about such truth-shifting entities as 
contexts.    (06)

Pat    (07)

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