Crispin Weston (crispinw@dircon.co.uk)
Tue, 14 Sep 1999 09:38:09 +0100
From: "Crispin Weston" <crispinw@dircon.co.uk> Subject: Predictability Date: Tue, 14 Sep 1999 09:38:09 +0100
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Martin wrote
<<Predictions remain useful as long as we think they are useful>>
I wrote:
<<So if I predict that swallowing arsenic will cure my flu, then so long as
I believe this prediction to be useful, it *is*?>>
Martin replied:
<<Of course Crispin, That is what has been happening for centuries. we have
been doing stuff because we think it is right: Blood letting, leaching,
taking laudenum, using belladona to make our eyes more beautiful, using
organo-phosphate pesticides, administering anti-biotics for viral diseases
and to fatten pigs, the widespread use of itolin in the US, blamming fats
for obesity.. I could go on.>>
But you have not answered my question again - you have answered a completely
different one. You have answered the question '...so long as I believe this
prediction to be useful, I will take the arsenic' and the principle that you
illustrate is not <<Predictions remain useful as long as we think they are
useful>> but <<People act on predictions as long as they think they are
useful>> Of course they do that. Of course that has been happening for
centuries and always will, because people's actions are inevitably shaped by
their beliefs. But their beliefs can be wrong.
The question I asked was, do you really mean to say that <<so long as I
believe this prediction to be useful, it *is*?>>. In other words, if I
*believe* the arsenic will cure my flu, then it *will* cure my flu? If I
*believe* that angels will catch me when I jump off the Empire State
Building then they *will* catch me when I jump off the Empire State
Building? No - of course they won't. But to be useful, a prediction has to
achieve a level of accuracy, a means has to be effective at achieving its
desired end. And means don't always achieve their desired ends. Some means
are demonstrably better than others at achieving the same end.
>>Optimism/pessimism are characteristics which distort prediction and are
>>therefore always irrational. If I go to the doctor I don't want an
>>optimistic or pessimistic diagnosis
>yes... but the doctor will be working on a belief system. Medicine is one
>of the most socially constructed bodies of knowledge we support
True but irrelevant. To say that something is a belief system does not mean
that it is not a knowledge system: on the contrary - the most widely
accepted definition of knowledge is 'true, justified *belief*'. In other
words if you *don't* believe something, then you *can't* claim it as
knowledge. Do you not believe that some doctors, some belief systems, are
more effective, that their predictions are more accurate, than others? Of
course you do. But your ideology which says that there is no truth and that
one social construct is ultimately no better than another simply cannot
account for the different levels of effectiveness - the different predictive
accuracies - shown by different belief systems.
Crispin.
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