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C00002 00002	nonmon[w84,jmc]		Applications of non-monotonic reasoning (circum)
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nonmon[w84,jmc]		Applications of non-monotonic reasoning (circum)

	Non-monotonic reasoning in general and circumscription
in particular provide a way to understand certain phenomena of
human behavior.  This is because we almost never have precise
enough information to decide interesting non-mathematical
questions (a fortiori non-scientific questions) by logical deductive
reasoning alone.  Our general common sense knowledge carries
with it the fact there are possible exceptions to the principles
we use.  Moreover, we don't know precisely what these exceptions
may be, and therefore we don't have the information to exclude
them.

	Instead we choose the simplest or most likely or standard
"model" of the facts we choose to take into account.  This means
that what conclusions we draw depends on what facts we take into
account.  Unfortunately, we humans have a limited capacity to
keep a large number of facts in mind simultaneously.  Therefore,
we are selective in what we take into account.  This selection
is often determined by biases of one kind or another.  If we
are on one side of an issue or if we are arguing with people
we regard as opponents, we try to select a collection of facts whose
standard model agrees with our bias.  In many issues, anyone's
desired conclusion can be made to follow quite naturally from
a biased selection of relevant facts.