On Jul 17, 2007, at 11:33 AM, John F. Sowa wrote: (01)
> Pat,
>
> I'm traveling now, and I don't have my copy of the convenient
> selection from Tarski's papers with me. But he does not do
> that in his 1933 paper or the more philosophical paper of 1944,
> which is on my web site.
>
> JFS>> But if the issues for any empirical subject were indeed
>>> "blindingly obvious", Tarski would have given some examples.
>
> PH>> And he did.
>
> Where? He certainly did not do so for "Snow is white", and I
> could not find any other example. (02)
But he DID do that for 'snow is white'. The logical form of this is a
predication (of the property 'being white' ) for a thing ('snow'):
IsWhite(snow). The Tarskian model of this has to have one entity in
its universe D, called 'snow' and one property in R. What exactly
this 'snow' IS in some metaphysical sense does not need to be
specified, but it is pretty simple to think of it as a mereological
sum of all pieces of snow. The property of being white is also not
very hard to specify. I'd be happy to base it on a majority vote by
non-visually impaired human subjects, say. (03)
>
> PH> As did Russell, Quine and others.
>
> Could you please go through any of the publications by Russell
> or Quine and find one empirical example in which they started
> with an empirical subject and specified the sets D and R of
> the domain. (04)
They may not have specified D since D can be any set, so does not
need to be specified. There are several examples where they refer to
a set of physical entities. It will take me a few hours to dredge up
the references, but I have sent you a list on several earlier
occasions when we have had this debate. (05)
> I realize that they did such things for mathematical
> subjects, and I also realize that they have waved their hands
> about for a lot of empirical issues. (06)
But what you call hand-waving over empirical issues is exactly what
does NOT need to be done. There is no need to specify exactly what
counts as a piece of snow. The appropriate reply, when asked to give
such criteria, is that whatever criteria you choose, that will
specify a domain of pieces of (real) snow, and that domain will be
the universe of some Tarskian interpretation. Nothing in the Tarskian
theory turns on these criteria that you are so concerned with, so of
course the theory does not specify them. Calling this 'hand-waving'
misses the key point: there is no need to wave the hands. (07)
> And I also realize that
> many people in comp. sci. and AI (e.g. Lenat) have specified
> actual sets. But please show me where Russell and Quine have
> taken a single empirical subject (or even one complete sentence
> in English) and specified the sets D and R.
>
> PH> One does not have to go into all this detail in order to apply
>> a Tarskian semantics.
>
> Just saying that there exists unspecified sets D and R does not
> constitute an example. I'm not asking for all the detail, but
> just one example, even a toy one, by Tarski. (08)
There are two issues. One is whether or not a Tarskian model (D and
R) can be built from pieces of the actual world: whether the elements
of D can be real physical things. The other is whether D needs to be
specified in absolute detail. I claim that the answer to the first is
clearly Yes, and that this does not imply that the answer to the
second must be Yes. (09)
>
> PH> He probably didn't because he thought it was so obvious that
>> it didn't need to be given any exposition. Quine seems to have
>> taken a similar view.
>
> In other words, they're hand wavers. (010)
No, they recognize that there is no need to specify some thing that
is arbitrary on principle. (011)
> They did do the detailed work
> for mathematical subjects, but if it was so "blindingly obvious" for
> empirical subjects, why didn't they work out one serious example? (012)
What 'working out' do you think needs to be done? What constitutes a
'serious' example? (013)
Pat (014)
>
> John
>
>
>
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