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C00002 00002	%philos[f89,jmc]		A Philosophy of Science and Common Sense
C00007 00003	\smallskip\centerline{Copyright \copyright\ 1989\ by John McCarthy}
C00008 00004	approximate theories
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%philos[f89,jmc]		A Philosophy of Science and Common Sense
\input memo.tex[let,jmc]
\title{An Epistemology of Common Sense}


	Let us begin with science, because the basic facts of
science are better understood than the basic facts of philosophy.
We also understand the limitations of our current knowledge of
science better than we understand the limitations of our
philsophical knowledge.

	According to science, a human being consists of about
$10\uparrow 28$ atoms and has a very complex structure.  We
also have a complex evolutionary history.  Our universe began
with the big bang about 15 billion years ago.  Our earth began
about 4.5 billion years ago and primitive life began about
3 billion years ago, multi-cellular life began about
600 million years ago, mammals became dominant 65 million years ago,
humanoids arrived 3 million years ago, modern man 30,000 years ago,
history 6,000 years ago, speculative history 2,500 years ago,
modern science 500 years ago, mathematical logic 100 years
ago and formalized nonmonotonic reasoning 10 years ago.

	We are interested in {\it epistemology}, the study
of knowledge and how it is obtained and justified.  We are
also interested in {\it metaphysics}, what can be said
about the physical world apart from the specific sciences.
What does all the above science tell us about that?

	1. What we can observe about the world is very
far removed from the basic structure of the world.
Apparently intelligence requires structures built in
a multi-level structure above atoms, and the atoms
themselves are complex entities.

	2. While what we can observe has a very complex
physical basis, there are enough approximate regularities
at the size level we can observe so we can have approximate
common sense knowledge of the world that works well enough
so that we can mostly survive till we wear out.

	3. By the methods of science we can find out more and
more of the structure of the world and its history.
However, the most basic phenomena are less well understood,
and there is no reason to suppose that science will get to
the very bottom of it in the near future.
Our study of epistemology must reconcile itself to this
fact; it must be able to deal with approximate knowledge
for the indefinite future.

	4. There is no reason to suppose that regarding
the world as a construct from sense data is likely to
work as a philosophical strategy.  $10\uparrow 28$ is
too big a number.  What we can learn about the world
is a contingent matter.  I agree with G\:odel's position
that what we can learn about even the facts of
mathematics is not guaranteed.
\smallskip\centerline{Copyright \copyright\ 1989\ by John McCarthy}
\smallskip\noindent{This draft of PHILOS[F89,JMC]\ TEXed on \jmcdate\ at \theTime}
%File originated on 29-Oct-89
\vfill\eject\end
approximate theories
The ai point of view
epistemology should work just as well for robots if it's
any good