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∂CSL Mr. See Hiow Tong↓588, Siglap Road↓SINGAPORE 1545∞
Dear Mr. See:

	I didn't say that the S and P problem required a computer,
and I believe some people have solved it without one.  I said it
was convenient to write a program and that I had done so when I
solved it myself.  I didn't keep my own program, and I have no
other.

	The interesting fact about the problem was formulating
it in a rigorous axiom system for knowledge and proving the correctness
of a translation to a problem in arithmetic.  For example, this
begins with proving the correctness of translating Mr. P's "I don't
know the numbers" into "the numbers are not both primes" and Mr. S's
"I knew you didn't know them" into "The sum of the numbers is not
the sum of two primes".  I think the formalism of my "First order
theory of individual concepts and propositions" is inadequate for
the task.  I devised another formalism based on Kripke's accessibility
relation for possible worlds and wrote an axiomatization from
which Ma Xiwen of Peking University proved to the satisfaction
of our computer proof checker the equivalence of S and P to a purely
arithmetic condition on  m  and  n.  Unfortunately, there were
some bugs in the axioms, and we don't yet have a paper in which
they problem is corrected, the proof redone, and the whole thing
written up.

	Enclosed are some reprints that may interest you.  I'm
now working mostly on the topics I discussed in my lecture about
common sense and on the formalization of non-monotonic reasoning.

	Best wishes, and I hope you will do some research in this
field.

.sgn