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

␈↓ ↓H␈↓∧Telephone 415 497-4430␈↓ 	␈October 2, 1979 




␈↓ ↓H␈↓Dr. Ashok Chandra
␈↓ ↓H␈↓IBM
␈↓ ↓H␈↓Thomas J. Watson Research Center
␈↓ ↓H␈↓P.O. Box 218
␈↓ ↓H␈↓Yorktown Heights, N.Y. 10598

␈↓ ↓H␈↓Dear Ashok:

␈↓ ↓H␈↓        I delayed writing you, because I expected momentarily to ≡nish the circumscription paper.

␈↓ ↓H␈↓        As␈αyou␈αwill␈αsee,␈α
I␈αhave␈αadopted␈αyour␈αsuggestion␈α
for␈αmodifying␈αcircumscription␈αin␈α
a␈αclearer
␈↓ ↓H␈↓but␈αlogically␈αequivalent␈αform␈αsuggested␈αby␈αPat␈αHayes.␈α The␈α␈↓↓R(a)␈α∨␈αR(b)␈↓␈αexample␈αnow␈αworks,␈αand
␈↓ ↓H␈↓best␈α⊂of␈α⊂all,␈α⊃we␈α⊂can␈α⊂again␈α⊂prove␈α⊃Davis's␈α⊂theorem␈α⊂relating␈α⊂the␈α⊃syntactic␈α⊂and␈α⊂semantic␈α⊃forms␈α⊂of
␈↓ ↓H␈↓circumscription.

␈↓ ↓H␈↓        Enclosed␈αis␈α
a␈αcheck␈αfor␈α
$94.00␈αwith␈αthe␈α
payee␈αblank.␈α
 It␈αis␈αto␈α
pay␈αfor␈αmy␈α
∨ight␈αto␈αBoston␈α
for
␈↓ ↓H␈↓which␈α
I␈αhave␈α
≡nally␈αgotten␈α
partly␈αreimbursed.␈α
 It␈αshould␈α
be␈αmade␈α
out␈αto␈α
IBM␈αor␈α
the␈αtravel␈α
agency
␈↓ ↓H␈↓according to whether IBM paid it.

␈↓ ↓H␈↓        I␈α
received␈α
a␈α
letter␈α
from␈α
Sharyn␈α
Hawkins␈α
with␈α
one␈α
more␈α
paycheck.␈α
 According␈α
to␈α
the␈αtotal␈α
on
␈↓ ↓H␈↓it,␈α∞which␈α∞agrees␈α∞with␈α∞my␈α∞somewhat␈α∞dim␈α∞recollection,␈α∞IBM␈α∞has␈α∞now␈α∞paid␈α∞me␈α∞for␈α∞≡ve␈α∞of␈α∂the␈α∞six
␈↓ ↓H␈↓weeks that I worked.

␈↓ ↓H␈↓        Carolyn and I both enjoyed our six weeks at IBM and all the interesting people we met.


␈↓ ↓H␈↓Best regards,



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