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levels of belief



Hi --

Feynman said that in science, one should never believe anything entirely,
nor disbelieve anything entirely. He eloquently described the "level of
belief" in terms of a pointer on a scale running from 0% to 100%. Any
level such as 99% or even 99.999% is OK, because it means there is some
finite weight of evidence that will change your mind. The extreme levels
(0% and 100%) are different -- they are unscientific -- because they imply
your mind cannot be changed by the evidence.

This applies not only to levels of belief in theories, but levels of
confidence in experimental data.

We have all sorts of words to describe levels of belief: conjecture,
hypothesis, theory, et cetera. We even have words for the extremes:
falsehood, impossibility, certainty, immutable fact, et cetera -- but we
have relatively little use for them.

Probems arise when talking with nonscientists.

To a minor extent, there is a problem with divergent definitions. When
nonscientists say "that's just a theory" they probably mean not only that
the belief level is less than 100%, but indeed that the belief level hardly
rises above the level of an implausible and unsubstantiated conjecture.

But vocabulary isn't the major issue. The problem is one of unmet
expectations. If the nonscientist is expecting and demanding a statement
of fact -- 100% immutable fact -- there is nothing a reputable scientist
can say that will meet the demand.

Scientists are accustomed to belief levels less than 100%. Indeed we revel
in the politeness and the honesty of non-extreme beliefs. But we need to
recognize that many other people have been led to expect categorical
immutable truths, and any lower level of belief leaves them uncomfortable
and unsatisfied.

I have some partially-baked ideas on how we might address this problem, but
I've said enough for now. Does anybody else have ideas on this?