From: platt@watson.ibm.com (Daniel E. Platt)
Subject: Re: STRUCTURE OF TIME
Date: Thu, 08 Oct 1992 20:06:37 GMT
Disclaimer: This posting represents the poster's views, not necessarily those of IBM
Organization: IBM T.J. Watson Research Center

In article <1992Oct8.171639.29802@murdoch.acc.Virginia.EDU>, crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:
|> In article <1992Oct8.154736.680@CSD-NewsHost.Stanford.EDU> pratt@Sunburn.Stanford.EDU (Vaughan R. Pratt) writes:
|> >In article <1992Oct8.004124.5221@murdoch.acc.Virginia.EDU> crb7q@kelvin.seas.Virginia.EDU (Cameron Randale Bass) writes:
|> >>     Faith is very powerful, and I hope we can keep it far far away from
|> >>     physics.
|> >>
|> >
|> >Too late.  Feynman, Vol. III, Ch. 1, sect. 1-4:  "This experiment has
|> >never been done in just this way.  The trouble is that the apparatus
|> >would have to be made on an impossibly small scale to show the effects
|> >we are interested in.  We are doing a `thought experiment,' which we
|> >have chosen because it is easy to think about.  We know the results
|> >that *would* be obtained because there *are* many experiments that have
|> >been done, in which the scale and the proportions have been chosen to
|> >show the effects we shall describe."
|> >
|> >Asking the student to believe that *had* this experiment been done
|> >things would have turned out as described, *even though this particular
|> >experiment has never been done*, is without a shadow of doubt asking
|> >the student to have faith.  And it shows the great faith of physicists
|> >in QM: they can predict with sufficient confidence the outcome of a
|> >gedanken experiment that they are comfortable describing it in great
|> >detail even though it has not been done.
|> 
|>      Faith is certainly not the foundation of this belief.  This is
|>      an inference from previous experimental results, and if the
|>      experiment were performed and the results were different than
|>      our expectation, faith in the expected result would not matter
|>      diddly.

This statement is essentially correct (ackkk!!! I'm actually almost
agreeing with CD Bass... there must be something wrong!), with one
proviso (ah... that's better...): the above is an extrapolation
into a situation where experiment cannot easily be constructed.
Feynmann freely admitted the experiment wasn't do-able.

It is also not a statement of faith in that gedanken experiments are
statements describing consequences of principles and theories which
may have already been supported in do-able experiments.

|> 
|>      You are confusing the colloquial definition of 'faith' as the expectation
|>      derived or derivable from experience (and hence admitting falsifiability)
|>      with the 'Faith' that admits no falsifiability.

Falsifiability may end up being the issue with gedanken experiments --
if you actually ever get to do one :-).  Some experiments have actually
been built that are approaching the limits of what were once only realizable
in the mind.  (Thinking of various quantum optical systems.)

|> 
|> >A gedanken experiment is an act of faith.
|> 
|>      A gedanken experiment is a construct that admits falsifiability if
|>      it is physics.  It is not an act of Faith.

Now this I feel misses the point.  I think gedanken experiments are
ways of exploring the consequences of principles or theories in a
more practical setting.  Einstein's relativistic railroads were never
things that one could do falsifiable tests on.  However, they did
provide a good way to articulate consequences.

These constructs also allowed the exploration of the consequences of
quantum mechanics in areas that lay at the foundation of the field,
such as EPR, Bell's theorems, etc.  So, in this sense, they provide
a way of exploring the scope of theories more than being a way of
enforcing falsifiability.

<much on issues of theology and 'faith' deleted>

|> 
|>      If you understand the meaning of Faith as being separate from
|>      falsifiability, then you can not comment on Faith from your perspective.
|> 
|> >>To deny faith is to deny that you ever take the easy way out by just
|> >>following the formula blindly instead of reasoning things out from
|> >>scratch.  But to come to rely on faith altogether is to inhibit your
|> >>ability to adapt.
|> 
|>      There is a great deal of difference between Faith and blindly
|>      treading down the path.  Faith is actually the antithesis of
|>      blind treading.  However the discussion of such issues
|>      is certainly best left elsewhere.

It sounds like you are on the edge of saying faith is not blind, but has
an origin and direction...  Some people have based theology on an idea like
'the universe was created good' ("In the beginning...").  While the textual
sources are flasified (the Babylonian cosmology in the P source, and the more
primitive J source doesn't hold water, even if creationsists want equal time
in our schools), the intent that the universe is good is not
falsifiable; yet it is something derived from experience.  People spend
lots of time talking about it in communicating their experience. 

|> 
|> >Faith is a good thing, but like all good things it should be taken in
|> >moderation.
|> 
|>      Like all non-scientific concepts, Faith should be kept out of 
|>      science.

Here's a point I tend to agree with.  One point I feel worth making is
that science is description.  There's lots of people who feel very 
confident in talking about the characteristics of my coffee cup's
quantum state vector, without reference to the idea that this kind of
language presupposes that quantum state vectors are real tangible things
with substance.  I'd tend to say that they are descriptions, just as
'mass', 'momentum', 'temperature', and even 'time' are descriptions
constructed to understand, organize, and predict the behavior of the
universe around us.  Attaching substance to these descriptions is a
*non-falsifiable* interpretation of the descriptions, and seems to 
fall into the area of 'faith.'

|> 
|>                               dale bass
|> 
|> -- 
|> C. R. Bass                                           crb7q@virginia.edu
|> Department of Mechanical and Aerospace Engineering
|> University of Virginia
|> Charlottesville, Virginia                            (804) 924-7926

Dan Platt