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Re: Fwd: Re: Underdetermination and Scientific Realism

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Dear Nick,

Thanks for your reply. I am mostly in agreement with what you are saying about
epistemology so I will leave that at that. I just have a few more brief comments
on UT.

> I?m intrigued by the arguments you give for the underdetermination thesis, but
> I
> fear we?re talking slightly at cross purposes. ?In his original e-mail Tasker
> denies UT on the basis that under a certain reading of 'equally well supported
> by the evidence' you can categorically specify the universe.? I hope I?m not
> displaying too much ignorance when I observe that this assertion is one which I
> neither understand nor recognise as my own position. 

Sorry if I have misinterpreted you. However I believe that, unless this is your
position, you have not refuted UT. It is all very well extending our
confirmatory instances beyond observable instances, but if then we still cannot
categorically specify which world we are in (that is, the number of worlds
compatible with our theory is narrowed down to one) we have not refuted UT. As I
stated it UT says that the number of worlds empirically equivalent with ours is
strictly greater than 1.

> The interpretation of
> ?equally well supported? with which I am concerned in the first e-mail is
> elaborated by the following principle of evidence: all and only the observed
> instances of a theory?s empirical consequences are confirmatory instances.
> While I admit that there may be an indefinite number of theories which are
> equally well supported by the data given this principle of evidence, I flat out
> deny that the principle is correct.

I am aware there is some cross talk going on here, in my first e-mail I was
pushing the suggestion that it is your interpretation that is at cross purposes
with UT. As I said, UT is most often described in terms of empirical equivalence
as defined by me. That confirmatory instances are just the observed instances of
a theory is not a premise of UT. Confirmatory instances of a theory, in this
loose sense, plays no role in empirical equivalence or UT. The point I am making
is that, although your arguments may belittle the philosophical import of UT,
they do not refute it.

Having said this, I am still interested to know what you mean by evidence, and
confirmatory instance (these notion have been left a little vague in this
discussion). Could an application of Occams razor confirm a theory? 

> In the meantime, I?ll just note
> one point about argument (a). It seems that the structure of time ? in the
> sense you describe ? would be more a matter for metaphysics than for natural
> science. So the fact that the empirical evidence underdetermines theory choice
> in this case need not threaten the rationality of choice between theories in
> the day to day world of natural science. 

Its funny you should say that, and I would say exactly the same - this is
metaphysics not physics. However, as I said in my last e-mail, a lot of what
theoretical physicists are doing today *is* metaphysics in my opinion. For
example, if we look at the results of Kurt Gödel: there are solutions to the
field equations of General Relativity in which there are closed time like curves
(CTC's). This is exactly the topological situation my example was concerned
with. This is not the only time theoretical physicists have talked about the
topology of time: the many worlds interpretation of quantum mechanics postulates
branching time, i.e. time is ascribed a topology where the temporal relation
'before' is a partial but not a total ordering of events. Another example is
(I'm not positive about this one though) in quantum loop gravity the topology of
time is postulated to be discreet, not dense. There are, I'm sure, plenty of
other examples - but I would have to refer to someone who studied physics for
the details.


-- 
Andrew Bacon
Lady Margaret Hall
07830048336
http://users.ox.ac.uk/~lady1900



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