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

␈↓ ↓H␈↓∧Telephone 415 497-4430␈↓ 
¬March 22, 1977 




␈↓ ↓H␈↓Dr. Stevan Harnad
␈↓ ↓H␈↓␈↓↓The Behavioral and Brain Sciences␈↓
␈↓ ↓H␈↓P.O. Box 777
␈↓ ↓H␈↓Princeton, N.J. 08540

␈↓ ↓H␈↓Dear Dr. Harnad:

␈↓ ↓H␈↓        I␈α∞have␈α∂read␈α∞the␈α∞paper␈α∂␈↓↓Structural␈α∞Theories␈α∞in␈α∂Psychology␈α∞and␈α∞the␈α∂Problem␈α∞of␈α∂Meaning␈↓␈α∞by
␈↓ ↓H␈↓Dennis Pro≠tt.  I found it stimulating but confused.  Here are some detailed comments:

␈↓ ↓H␈↓1. Its criticisms of the inadequacy of de≡ning meaning in terms of the senses are well taken.

␈↓ ↓H␈↓2.␈αI␈αmust␈αadmit␈αthat␈α
I␈αevaluate␈αPro≠tt's␈αideas␈αabout␈α
meaning␈αby␈αcomparing␈αthem␈αwith␈αsome␈α
ideas
␈↓ ↓H␈↓I␈αam␈αdeveloping,␈αand␈αI␈αthink␈αhis␈αare␈αmuddled.␈α Meanings␈α(to␈αme)␈αare␈αfunctions␈αin␈αa␈αhierarchy␈αof
␈↓ ↓H␈↓intensionality␈α∞and␈α∂go␈α∞down␈α∞in␈α∂the␈α∞hierarchy.␈α∞ Near␈α∂the␈α∞top␈α∞of␈α∂the␈α∞hierarchy␈α∞are␈α∂sentences␈α∞and
␈↓ ↓H␈↓terms(in␈α⊃natural␈α⊃languages␈α⊃-␈α⊃noun␈α⊃phrases).␈α⊃ At␈α⊂the␈α⊃bottom␈α⊃are␈α⊃concrete␈α⊃objects␈α⊃like␈α⊃my␈α⊂dog
␈↓ ↓H␈↓Caspian␈α∞and␈α∞the␈α∞number␈α∞4.␈α∞ The␈α∞middle␈α∞includes␈α∞concepts␈α∞like␈α∞that␈α∞of␈α∞␈↓↓McCarthy's␈α∞dog␈↓␈α∂and␈α∞␈↓↓its
␈↓ ↓H␈↓↓number␈α
of␈α
legs␈↓.␈α
 There␈α
are␈α
many␈α
meaning␈α
functions,␈α
and␈α
their␈α
common␈α
feature␈α
is␈α
that␈αentities␈α
with
␈↓ ↓H␈↓certain␈α
meanings␈α
identical␈α
are␈α
intersubstitutable␈α
in␈αcertain␈α
contexts.␈α
 The␈α
theory␈α
of␈α
meaning␈αcan
␈↓ ↓H␈↓be␈αexpressed␈αmathematically␈αwithout␈αany␈αreference␈α
to␈αthoughts,␈αbut␈αa␈αparticular␈αmeaning␈α
function
␈↓ ↓H␈↓may be important in discussing the thoughts of a particular person or people in general.

␈↓ ↓H␈↓3.␈α
I␈α
did␈α
not␈α
≡nd␈α
the␈α
analogy␈α
with␈α
quantum␈α
mechanical␈α
complementarity␈α
helpful.␈α
 Complementarity
␈↓ ↓H␈↓in␈α⊃physics␈α⊃leave␈α⊃physicists␈α⊂and␈α⊃philosophers␈α⊃in␈α⊃an␈α⊂intellectually␈α⊃di≠cult␈α⊃situation,␈α⊃but␈α⊂no-one
␈↓ ↓H␈↓knows␈α∞how␈α∞to␈α∞avoid␈α∞it.␈α∞ The␈α∞uncertainty␈α∞principle␈α∞is␈α∞a␈α∞logical␈α∞consequence␈α∞of␈α∞a␈α∞formulation␈α∞of
␈↓ ↓H␈↓quantum␈α∂mechanics␈α∂that␈α∂correctly␈α∂predicts␈α∂the␈α∂results␈α∂of␈α∂experiments,␈α∂and␈α∂no-one␈α∂has␈α⊂found␈α∂a
␈↓ ↓H␈↓theory␈αwithout␈αcomplementarity␈αthat␈αgives␈αcorrect␈αpredictions.␈α There␈αis␈αno␈αsuch␈αexcuse␈αhere,␈αand
␈↓ ↓H␈↓I think Pro≠tt is pursuing a pro≡tless analogy.

␈↓ ↓H␈↓4.␈αBrentano␈αand␈αperhaps␈αChisholm␈αare␈α
mistaken␈αin␈αsupposing␈αthat␈αintentional␈αconcepts␈αare␈α
useful
␈↓ ↓H␈↓only␈αin␈αdiscussing␈αpsychological␈αphenomena.␈α Terms␈αlike␈α␈↓↓possibly␈↓,␈α␈↓↓necessarily␈↓,␈α␈↓↓caused␈↓,␈αand␈α␈↓↓can␈↓␈αare
␈↓ ↓H␈↓also intentional.

␈↓ ↓H␈↓5.␈αMental␈αconcepts␈αare␈αalso␈αapplicable␈αto␈αmachines,␈αand␈αcan␈αbe␈αstudied␈αmore␈αsimply␈αin␈αrelation␈αto
␈↓ ↓H␈↓machines.

␈↓ ↓H␈↓        I␈αenclose␈α
two␈αpapers␈α-␈α
␈↓αwhich␈αI␈αdon't␈α
want␈αto␈αsubmit␈α
for␈αpublication␈αat␈α
present␈↓␈α-␈αthat␈α
bear
␈↓ ↓H␈↓on meaning and on the mental qualities of machines.
␈↓ ↓H␈↓αDr. Stevan Harnad␈↓ ¬gMarch 22, 1977␈↓ 
nPage 2␈↓ 


␈↓ ↓H␈↓        As␈α⊗to␈α↔whether␈α⊗you␈α↔should␈α⊗publish␈α↔Pro≠tt's␈α⊗paper,␈α⊗I␈α↔don't␈α⊗know␈α↔the␈α⊗state␈α↔of␈α⊗the
␈↓ ↓H␈↓psychological␈α∂literature␈α∂well␈α∞enough␈α∂to␈α∂advise.␈α∂ If␈α∞the␈α∂views␈α∂he␈α∞criticize␈α∂are␈α∂widespread,␈α∂then␈α∞I
␈↓ ↓H␈↓suppose␈α∞it␈α∂should␈α∞be␈α∞published.␈α∂ If␈α∞you␈α∞do␈α∂publish␈α∞it,␈α∞I␈α∂will␈α∞have␈α∞comments␈α∂to␈α∞o≥er␈α∂along␈α∞the
␈↓ ↓H␈↓above lines.  The paper is clearly written - given the unclarity of the ideas.

␈↓ ↓H␈↓        I have no objection to your transmitting these remarks to the author.


␈↓ ↓H␈↓Sincerely,



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