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In article <240@sri-arpa.ARPA> KFL@MX.LCS.MIT.EDU writes:
>    I doubt that it is possible to design an experiment whose results could
>    require reverse causality for their explanation.	[Frank Adams]
>
>  I don't think there is any reverse causality, and if there is, I
>think it is much more likely to be discovered by peering at an
>oscillosope in a high energy physics lab than by peering at cards with
>mystical symbols on them by candlelight,

Here here!

>					  HOWEVER, I think experiments
>CAN and HAVE been designed which would require reverse causality to
>explain a possible outcome of.

Could you go into detail on this?  That "require" seems a bit strong.

I would say that Frank Adams' assertion is on par with Poincare's famous
claim that given a choice between a physical theory using non-Euclidean
geometry and its mathematically equivalent embedding in a Euclidean space,
physicists would of course opt for the latter.

I for one cannot think of a physical theory where reverse causality is
the preferable explanation.  Nor have I tried.

>			         Saying that no such experiment is
>possible is saying that belief in forward-only causality is non-
>scientific.  All scientific beliefs are in principle falsifiable by
>experiment.

Yes and no.  I'd say a lot of so called "scientific beliefs" are in the
category of semantic conventions.  For example, does the earth go around
the sun, or vice versa, or around their mutual center of gravity, etc?
All those questions are answered "yes" in an appropriate frame of refer-
ence.  One can trivially come up with coordinate systems where the earth
is "hollow", etc.  The modern attitude is that while certain frames are
clearly more natural, and our terminology reflects those frames, the ac-
tual physical "reality" lies above particular reference frames.

According to Martin Gardner, people used to get in intense flame wars
over the question of whether the moon rotates or not.

Willard Quine and others would go further and maintain that NO scientific
beliefs are falsifiable in principle.

ucbvax!brahms!weemba	Matthew P Wiener/UCB Math Dept/Berkeley CA 94720
 "Do not believe astrophysical observations until confirmed by theory."

Regarding causality and reverse causality, isn't any kind of causality
an illusion? I assume that causality is a manifestation of entropy
increase.

The arrow of time. What is it anyways? All nonstatistical laws of
physics are symmetric under time reversal. The statistical laws,
actually, are symmetrical, also, but they don't seem to apply in the
reverse direction, because, in typical applications, some `scientist'
(speaking loosely), creates an unusual situation of low entropy and
watches it evolve into high entropy, where statistical mechanics
suggests it should be.  So the question is not why does entropy
increase, but why isn't it already at the maximum? The universe
apparently began as a system of very low entropy. If the state of the
universe in the future is preordained (Remember, causality is bunk, so
why not? It's only twice as outrageous as the fact that the universe
exists at all.) to have low entropy, then eventual entropy increase is
inevitable.  In fact, the backwards evolution of this `preordained'
state should obey the familiar laws, except in reverse.  We are riding
a wave of entropy away from the beginning of the universe.  Maybe alien
intelligence is/will be riding a wave in the reverse direction from the
end of time, although to them, we would be in their future, although
moving backwards.

Between our realm and their realm, there would probably be a realm of
very high entropy, where the universe would consist of a very thin gas,
and there would be no phenomena that distinguish one direction of time
from another.

At least globally. Perhaps there will be local arrows of time, which
disagree with each other. Is communication possible between
intelligences with opposing arrows of time? John Brunner (in the novel
"The Wrong End of Time") and Martin Gardner have considered these
questions. The physisist and science-fiction writer Gregory Benford has
considered the possibility and possible consequences of communication
backwards in time in his novel "Timescape".

If causality it bunk, then maybe time travel is possible, after all.
Read Benford's novel for a resolution of the practical paradoxes via
the many-possible worlds interpretation of quantum mechanics.

It's something to think about. I think this is consistent with known
physical theory.

ucbvax!brahms!carrier	Stephen Carrier/UCB Math Dept/Berkeley CA 94720
"Riding the entropy wave,...Wow! Tubular!"  -surfer in the universe.

> All scientific beliefs are in principle falsifiable by experiment.

For example, I suppose, the scientific belief that all scientific
beliefs are in principle falsifiable by experiment...

In article <240@sri-arpa.ARPA> KFL@MX.LCS.MIT.EDU (Keith Lynch) writes:

[>> = franka@UCB-Vax.arpa (Frank Adams)]
>>    I doubt that it is possible to design an experiment whose results could
>>    require reverse causality for their explanation.

> [...] HOWEVER, I think experiments CAN and HAVE been designed which would
> require reverse causality to explain a possible outcome of.

So tell us what they are/were.

> [...] All scientific beliefs are in principle falsifiable by experiment.

This last claim is not a scientific belief either, then, I'm afraid.
To me, "scientific belief" is a contradiction in terms.  The whole fuss
about falsifiability can be reduced to the self-evident observation that a
theory that does not produce sufficiently specific predictions (which then,
of course, might turn out false) is pretty useless, at least as far as
predictive power is concerned.  This is just one of many reasons why a
theory might be predictively worthless, others being that it consistently
predicts false things, or that it predicts the same as some simpler theory,
or that it is too specific.  (A predictively worthless theory may still
have redeeming qualities, such as providing a framework that facilitates
the construction of predictively powerful theories.)  These requirements on
theories are basic scientific principles; they are not scientific theories
themselves--nor does anyone claim they are--but follow from plain good
old-fashioned common sense.
To come back to the original point in question: at least in the exact
sciences (and in particular physics), for which theories take the form of a
mathematical model, causality is not a concept built into the theories, but
a manner of speaking informally about them.  At least in the way I use the
word "cause", I only say that event A causes event B if A precedes B in
time.  If someone would come up with a "reverse causality" contraption with
a knob that I can turn freely, and it appears that something in the past
(B) is consistently correlated with the way I choose the knob setting (A),
there is a paradox unless I can observe B only after A.  There are then two
possibilities: (I) For some reason it is (given the set-up) *in principle*
impossible to observe B before A.  (II) The correlation only holds if I
refrain from observing B before A.  In either case, the true event is of
course B' = my observing B.  Now B' follows A.  Causality (my use of the
word) is not violated.

HAPPY ENDING:  The inventor of the contraption is awarded the Nobel prize
in physics.  Endless discussions in sci.physics ensue whether B "really"
happens or is just "observed to have happened".  New Capras and Zukovs
helpfully point out to us that this is what Zen was about all the time.

-- 

Lambert Meertens, CWI, Amsterdam; lambert@mcvax.UUCP

>> All scientific beliefs are in principle falsifiable by experiment.
>For example, I suppose, the scientific belief that all scientific
>beliefs are in principle falsifiable by experiment...

Actually this does make sense.  This doesn't lead to a contradiction unless
one such experiment produces the paradoxical result.  As long as such an
experiment doesn't produce such a result, there's nothing to worry about.
Being falsifiable in principle isn't going to produce contradictions unless
real falsification occurs.
--
Never look a gift horse in the mouth, but beware of Greeks bearing gifts.

Kenneth Arromdee
BITNET: G46I4701 at JHUVM and INS_AKAA at JHUVMS
CSNET: ins_akaa@jhunix.CSNET              ARPA: ins_akaa%jhunix@hopkins.ARPA
UUCP: {allegra!hopkins, seismo!umcp-cs, ihnp4!whuxcc} !jhunix!ins_akaa

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In article <3942@jhunix.UUCP> ins_akaa@jhunix.UUCP (Ken Arromdee) writes:

>>> All scientific beliefs are in principle falsifiable by experiment.

>>For example, I suppose, the scientific belief that all scientific
>>beliefs are in principle falsifiable by experiment...

>Actually this does make sense.  This doesn't lead to a contradiction unless
>one such experiment produces the paradoxical result.  As long as such an
>experiment doesn't produce such a result, there's nothing to worry about.
>Being falsifiable in principle isn't going to produce contradictions unless
>real falsification occurs.

   Actually, this doesn't make sense. The proposition "all scientific
beliefs should in principle be falsifiable by experiment" is not itself
a scientific belief, but a philosophical belief. One does not determine
whether this belief is correct by doing an experiment, because there is
no such experiment to be performed. Instead, one engages in philosophical
argumentation. What we can see from this is that the philosophy of science
is not a branch of science, but of philosophy; which really should come
as no surprise.

ucbvax!brahms!gsmith    Gene Ward Smith/UCB Math Dept/Berkeley CA 94720
ucbvax!weyl!gsmith                The Josh McDowell of the Net

In article <3942@jhunix.UUCP>, ins_akaa@jhunix.UUCP (Ken Arromdee) writes:
> >> All scientific beliefs are in principle falsifiable by experiment.
> >For example, I suppose, the scientific belief that all scientific
> >beliefs are in principle falsifiable by experiment...
> 
> this does make sense... doesn't lead to a contradiction unless
> one such experiment produces the paradoxical result.

What is "the paradoxical result"? If it is true that "All scientific
beliefs are falsifiable by experiment" (F) and F is itself a
scientific belief, then either (1) F is falsifiable (and I'd be
interested to hear a potential scenario for getting such a result), in
which case the generalization is valid, or (2) F is not falsifiable,
in which case the generalization is simply false. There's no paradox here; no
self-denying statements. Just the (Popperian variant) on a problem as
old as Hume: The apparent impossibility of justifying induction
without already presupposing or relying on it in doing so.
-- 

Stevan Harnad                                  (609) - 921 7771
{allegra, bellcore, seismo, rutgers, packard}  !princeton!mind!harnad
harnad%mind@princeton.csnet