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From: lambert@mcvax.uucp (Lambert Meertens)
Newsgroups: sci.physics
Subject: Re: Reverse causality
Message-ID: <7134@boring.mcvax.UUCP>
Date: Sun, 9-Nov-86 07:00:58 EST
Article-I.D.: boring.7134
Posted: Sun Nov  9 07:00:58 1986
Date-Received: Sun, 9-Nov-86 21:00:22 EST
References: <240@sri-arpa.ARPA>
Reply-To: lambert@boring.uucp (Lambert Meertens)
Organization: CWI, Amsterdam
Lines: 50
Keywords: falsifiability, theory, scientific principles
Apparently-To: rnews@mcvax


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