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␈↓ ↓H␈↓␈↓βS␈↓∧ Artificial Intelligence Laboratory, STANFORD UNIVERSITY, Stanford, California 94305

␈↓ ↓H␈↓∧Telephone 415 497-4430␈↓ 	ISeptember 22, 1978 




␈↓ ↓H␈↓Professor Drew McDermott
␈↓ ↓H␈↓Department of Computer Science
␈↓ ↓H␈↓Yale University
␈↓ ↓H␈↓New Haven, Connecticut

␈↓ ↓H␈↓Dear Drew:

␈↓ ↓H␈↓        I␈α
just␈α∞got␈α
your␈α
paper␈α∞␈↓↓Non-Monotonic␈α
Logic␈α
I␈↓.␈α∞ As␈α
you␈α
note,␈α∞there␈α
is␈α∞considerable␈α
common
␈↓ ↓H␈↓ground␈α
between␈α
it␈α∞and␈α
my␈α
work␈α∞on␈α
circumscription.␈α
 However,␈α∞the␈α
two␈α
are␈α∞not␈α
the␈α
same,␈α∞and␈α
I
␈↓ ↓H␈↓don't␈α
fully␈α
understand␈α
their␈αrelations␈α
yet.␈α
 I␈α
think␈αmy␈α
minimization␈α
of␈α
the␈αset␈α
of␈α
elements␈α
of␈αthe
␈↓ ↓H␈↓domain gives di≥erent results from your system.

␈↓ ↓H␈↓        I␈α
hope␈α
to␈α
have␈α
more␈α
to␈α
say␈α
about␈α
this␈α
later,␈α
but␈α
for␈α
now,␈α
I␈α
enclose␈α
a␈α
copy␈α
of␈α
a␈αpaper␈α
treating
␈↓ ↓H␈↓circumscription␈α∞at␈α∞greater␈α∂length␈α∞than␈α∞in␈α∞my␈α∂IJCAI␈α∞paper.␈α∞ Mainly␈α∞it␈α∂is␈α∞older,␈α∞but␈α∞it␈α∂has␈α∞been
␈↓ ↓H␈↓somewhat edited to re∨ect my more recent views.


␈↓ ↓H␈↓Best regards,



␈↓ ↓H␈↓John McCarthy
␈↓ ↓H␈↓Director
␈↓ ↓H␈↓Professor of Computer Science

␈↓ ↓H␈↓cc: Jon Doyle, M.I.T.