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UBC Theses and Dissertations

Machines cannot think Gell, Robert George 1966

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MACHINES  CANNOT ' THINK by  R o b e r t George G e l l B.Sc,  U n i v e r s i t y o f B r i t i s h Columbia, 1 962  A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF M.A. <' i n t h e Department of PHILOSOPHY  We a c c e p t t h i s t h e s i s as conforming t o t h e required standard  THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1966  In presenting  this thesis i n partial fulfilment  of the r e q u i r e m e n t s f o r an advanced degree a t the U n i v e r s i t y of B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t freely  a v a i l a b l e f o r r e f e r e n c e and s t u d y . I f u r t h e r  agree t h a t p e r m i s s i o n f o r e x t e n s i v e for  c o p y i n g of t h i s  thesis  s c h o l a r l y purposes may be g r a n t e d by the Head o f my  Department or by h i s r e p r e s e n t a t i v e s .  I t i s understood  t h a t c o p y i n g o r p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n .  Department of P h i l o s o p h y The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada D a t e , 29 A p r i l 1966  i ABSTRACT T h i s paper i s a c r i t i c a l essay on t h e q u e s t i o n "Can machines t h i n k ? " , w i t h p a r t i c u l a r a t t e n t i o n p a i d t o t h e a r t i c l e s a p p e a r i n g i n an a n t h o l o g y Minds and Machines, A. R. Anderson editor.  The g e n e r a l  c o n c l u s i o n o f t h i s paper i s t h a t those  arguments which have been advanced t o show t h a t machines can t h i n k , are i n c o n c l u s i v e . I b e g i n by examining r a t h e r c l o s e l y a paper by H i l a r y Putnam c a l l e d "Minds and Machines" i n which he argues t h a t t h e t r a d i t i o n a l mind-body problem can a r i s e w i t h a complex machine.-  cybernetic  My argument a g a i n s t Putnam's i s t h a t e i t h e r t h e r e a r e  no problems w i t h computers which a r e analogous t o t h e ones r a i s e d by m e n t a l s t a t e s , or where t h e r e a r e problems w i t h these problems do n o t have a t bottom t h e same d i f f i c u l t i e s  machines, that  human e x p e r i e n c e s r a i s e s . I then continue  by' showing t h a t a c y b e r n e t i c machine i s  an i n s t a n t i a t i o n o f a f o r m a l  system. T h i s l e a d s t o a d i s c u s s i o n  o f . t h e r e l a t i o n s h i p between f o r m a l i t y and p r e d i c t a b i l i t y i n which I t r y t o show t h a t some t y p e s of machine a r e i n p r i n c i p l e p r e d i c t a b l e . I n t h e n e x t s e c t i o n I attempt t o prove t h a t any d i s c u s s i o n o f outward s i g n s o f i m i t a t i v e b e h a v i o r presupposes t h a t some l i n g u i s t i c theory,  such as a type r e d u c t i o n , has been s u b s t a n t i a t e d .  The  f o r c e o f t h i s argument i s t h a t such a t h e o r y has n o t i n f a c t been substantiated.  I o f f e r some g e n e r a l  of c o n c e p t - p r o p e r t y r e l a t i o n s .  theory  about t h e c o m p l e x i t y  ii F i n a l l y I g i v e a d e m o n s t r a t i o n t h a t no t e s t or s e t of t e s t s can be found t h a t w i l l be l o g i c a l l y s u f f i c i e n t f o r the a s c r i p t i o n of the concept '"capable of t h o u g h t . "  If this i s  s u c c e s s f u l , t h e n I have shown t h a t no t e s t can be f o u n d , which when a machine i s b u i l t t o pass i t , i s l o g i c a l l y adequate f o r s a y i n g t h a t t h a t .machine can t h i n k .  T h i s argument, i s o f f e r e d as .  f u r t h e r c r i t i c i s m of the I m i t a t i o n Game w h i c h A. M. posed as an adequate t e s t f o r t h i n k i n g s u b j e c t s . specific  Turing  pro-  B e s i d e s the  c o n c l u s i o n t h a t i n s u f f i c i e n t evidence,has been o f f e r e d  t o say t h a t machines can t h i n k , t h i s paper o f f e r s a more c o n c l u s i o n t h a t most standard difficulty.  general  problems have a t bottom a l i n g u i s t i c  However, t h i s g e n e r a l  c o n c l u s i o n i s a broad  speculative  one  to w h i c h the work i n t h i s paper, i s o n l y a s m a l l e x e m p l i f i c a t i o n  and  as such r e f l e c t s m a i n l y the f u r t h e r a m b i t i o n s of the  author.  iv ACKN OWLEDGEMSNT I w i s h t o thank my two t y p i s t s , Sue Reeves and A p r i l T o u p i n , and a l s o Steye Porche who p r o o f - r e a d t h e m a n u s c r i p t and o f f e r e d some v a l u a b l e s u g g e s t i o n s .  U n f o r t u n a t e l y I cannot  acknowledge t h e h e l p o r encouragement o f any o f t h e members o f the department i n t h e p r e p a r a t i o n o f t h i s work. I should l i k e t o d e d i c a t e t h i s t h e s i s t o L o i s , whose e  encouragement, though seldom acknowldged, was everpre.sent.  V  TABLE OF CONTENTS Section  Page  I. I n t r o d u c t i o n  1  I I . The Analogy Between Men and Machines  h  I I I . F o r m a l i t y and P r e d i c t a b i l i t y  19  IV. What i s B e h a v i o r ?  27  V. A T e s t f o r T h i n k i n g  39  VI. Conclusion  ...50  Footnotes Bibliography  -5*+ •  "...56  1  SECTION I INTRODUCTION This is a paper on the question "Can machines think?" and i t s g e n e r a l c o n c l u s i o n i s n e g a t i v e .  It is d i f f i c u l t  to  give an exact characterization of the problems that philosophers are i n t e r e s t e d i n when they discuss this question. However i t would be f a i r l y safe to say t h a t the p r o b l e m s are t h o s e posed by the recent advances i n d i g i t a l and analogue computers.  These  machines have been b u i l t to perform a great v a r i e t y of human t a s k s a n d t h e q u e s t i o n n a t u r a l l y a r i s e s a s t o w h e t h e r o r n o t we must say o f some ' s u p e r ' c o m p u t e r t h a t i t t h i n k s . I n t h i s r e s p e c t , of course, i t is of i n t e r e s t to c o n s i d e r the d e f i n i t i o n of a m e c h a n i c a l computer to see i f t h e r e are any l i m i t a t i o n s serious enough to j u s t i f y us i n withholding the designation, ' c a p a b l e o f t h o u g h t . B e f o r e we c a n d e c i d e w h e t h e r o r n o t a 1  machine t h i n k s , a g r e a t number of secondary problems must be tackled and these problems are of wide general p h i l o s o p h i c interest. Furthermore the philosophic importance of recent developments i n mathematics and p h y s i c s must also be assessed. So p o t e n t i a l l y t h e p r o b l e m " C a n m a c h i n e s t h i n k ? " c o u l d l e a d u s into very general philosophic speculation. However, an a r t i c l e b y A . M . T u r i n g " i n 1950 s p a r k e d a w h o l e s e r i e s o f p a p e r s i n t h e p h i l o s o p h i c j o u r n a l s , some o f w h i c h were c o l l e c t e d b y A . R. 3  p  Anderson, i n an anthology c a l l e d Minds and Machines.  This  paper is a c r i t i c i s m of the main arguments presented by those who f e e l t h a t machine's c a n t h i n k w i t h p a r t i c u l a r a t t e n t i o n  given  to those a r t i c l e s i n Minds and Machines. There are several conclusions arrived at i n this paper.  2  The argument i n the second s e c t i o n attempts t o show t h a t t h e r e . i s no s e r i o u s analogy between men and machines.  That i s t o say,  no s e r i o u s analogy i n the sense t h a t those problems which are r a i s e d because of the uniqueness of human e x p e r i e n c e , are n o t r a i s e d w i t h v e r y c o m p l i c a t e d computers.  . I n "the t h i r d s e c t i o n I  show t h a t a T u r i n g machine i s f o r m a l , and as such i s , i n the i m p o r t a n t sense, p r e d i c t a b l e .  The f o u r t h s e c t i o n i s an a t t a c k upon  the p o s s i b i l i t y of b u i l d i n g a computer  t o i m i t a t e human b e h a v i o u r .  The argument i s , t h a t u n t i l c e r t a i n t h i n g s are shown about our b e h a v i o u r a l c o n c e p t s , t h e n the problem of i m i t a t i o n cannot a r i s e . Of c o u r s e the f o r c e of t h i s argument i s t h a t t h e s e t h i n g s have not been shown. F i n a l l y i n the f i f t h s e c t i o n I t r y t o show t h a t no t e s t can ever be c o n s t r u c t e d which w i l l l o g i c a l l y be  adequate  f o r the a p p l i c a t i o n of the c o n c e p t , 'capable of t h i n k i n g ' .  This  argument i s meant t o u n d e r c u t the l o n g debate which has gone on c r i t i c i z i n g T u r i n g ' s " I m i t a t i o n Game",  which was proposed as a  test for thinking. Most of the arguments  of t h i s paper a r e an e x e m p l i f i -  c a t i o n of a g e n e r a l p h i l o s o p h i c approach.  T h i s approach i s one  i n which a t t e n t i o n i s f o c u s e d on the concepts t h a t we u s e .  By  d o i n g t h i s a t t e n t i o n i s drawn t o the c o m p l e x i t y of t h e s e c o n c e p t s , particularly i n their logical'structure.  I t i s argued t h a t too  l i t t l e a t t e n t i o n i s g i v e n t o the c o m p l e x i t y of language, p a r t i c u l a r l y w i t h r e s p e c t t o our. b e h a v i o u r a l c o n c e p t s .  At t i m e s  i t i s a r g u e d - t h a t u n t i l aome problems about the n a t u r e of concepts .are answered,  t h e n no d e c i s i o n  about the p o s s i b i l i t y  • o f c o n s t r u c t i n g r o b o t s can be made.  3  So i n a sense, I t h i n k t h a t  the g e n e r a l n a t u r e o f t h e t h e s i s o f t h i s paper can be s a i d t o be linguistic.  There i s a l s o a l a r g e r t h e s i s behind t h i s paper, b u t  upon w h i c h none o f t h e arguments depend.  This i s the idea that  most q u e s t i o n s o f p h i l o s o p h i c importance  can be p u t i n t h e form  of a problem about t h e l o g i c o f c o n c e p t s .  I f t h i s i s s o , and a  s y s t e m a t i c way can be found f o r d i s c o v e r i n g t h e l o g i c o f c o n c e p t s , t h e n t h e main problems o f p h i l o s o p h y can be s o l v e d w i t h i n a s c i e n c e o f language.  T h i s paper does n o t attempt  to establish  t h i s t h e s i s b u t r a t h e r i s meant t o be i n some s m a l l way an e x e m p l i f i c a t i o n of i t .  Thus t h e arguments o f t h i s paper t r y t o  show t h a t t h e problems connected  w i t h t h i n k i n g machines can a l l  b e . g i v e n a l i n g u i s t i c i n t e r p r e t a t i o n ; a l t h o u g h no attempt i s made t o g i v e a method f o r d i s c o v e r i n g t h e l o g i c o f c o n c e p t s . I s h o u l d m e n t i o n , f i n a l l y , t h a t t h i s ' p a p e r does n o t reiterate  i n any d e t a i l , t h e arguments which have a l r e a d y been  made i n t h e many papers on t h i s s u b j e c t .  I n f a c t i t i s assumed  t h a t t h e r e a d e r i s f a m i l i a r w i t h most o f t h e arguments and i n particular  t h a t t h e r e a d e r i s v e r y f a m i l i a r w i t h some s p e c i f i c  articles.  I n some p l a c e s t h i s paper i s an e x t e n s i o n o f some  v e r y thorough work by o t h e r p h i l o s o p h e r s .  But i n g e n e r a l t h e  c r i t i c i s m s o f t h i s paper a r e v e r y broad and a r e i n t e n d e d t o u n d e r c u t many o f t h e s t a n d a r d i d e a s connected "Can machines t h i n k ? "  w i t h t h e problem  SECTION I I THE ANALOGY BETWEEN MEN AND MACHINES H i l a r y Putnam i n h i s paper "Minds and M a c h i n e s " t r i e s to draw an a n a l o g y between t h e v a r i o u s c y b e r n e t i c machine ( c a l l e d a T u r i n g ding  s t a t e s o f a human b e i n g .  s t a t e s o f a complex  machine) an d t h e c o r r e s p o n -  He m a i n t a i n s t h a t a machine- "a?.s  has  l o g i c a l and s t r u c t u r a l s t a t e s , j u s t as a human has m e n t a l  and  p h y s i c a l s t a t e s , and a l s o t h a t those arguments which support  the i d e n t i t y o r n o n i d e n t i t y o f m e n t a l and p h y s i c a l s t a t e s  also  show t h a t t h e same t h i n g about l o g i c a l and p h y s i c a l s t a t e s .  As  we a l l know, a machine i s capable o f a complete m e c h a n i s t i c (causal) explanation parts.  and has no h i d d e n o r o t h e r w i s e m y s t e r i o u s  T h u s ' i f Putnam can s u s t a i n h i s a n a l o g y between men and  machines, he t h i n k s t h a t t h i s w i l l go some way (he does n o t t h i n k i t would be c o n c l u s i v e ) thesis.  I t i s my c o n t e n t i o n  i n substantiating a mechanistic i n t h i s s e c t i o n t h a t Putnam f a i l s  to f i n d t h e a n a l o g y t h a t he i s l o o k i n g f o r . Putnam's t h e s i s r e s t s on two main c l a i m s .  He t r i e s t o  show t h a t t h e p r o p o s i t i o n " I am i n s t a t e A i f and o n l y i f f l i p f l o p 3 6 i s on" i s , from t h e machine's p o i n t o f v i e w , s y n t h e t i c , or what i s t a k e n t o be t h e same t h i n g , a t l e a s t e m p i r i c a l l y v e r i f i a b l e . ' T h i s w i l l make i t analogous t o t h e p r o p o s i t i o n " I am i n p a i n i f and o n l y i f C - f i b r e s a r e s t i m u l a t e d "  and w i l l  depend upon t h e r e b e i n g d i f f e r e n t methods o f v e r i f i c a t i o n o f s t a t e A and f l i p f l o p 3 6 b e i n g on.  H i s other c l a i m i s that the  l o g i c a l - s t r u c t u r a l d i s t i n c t i o n i s analogous t o t h e mind-body one i n that there  can be a l o g i c a l d e s c r i p t i o n o f t h e machine's  computations j u s t as t h e r e  i s a m e n t a l d e s c r i p t i o n o f human  5 activity.  I hope t o show t h a t even from the p o i n t of v i e w of  the machine, the above p r o p o s i t i o n i s not s y n t h e t i c , and a l s o t h a t the l o g i c a l - s t r u c t u r a l d i s t i n c t i o n i s n o t analogous t o the mind-body d i s t i n c t i o n . Putnam c o n s i d e r s  a T u r i n g machine 'T' w h i c h can be i n  a number of s t a t e s , one of which i s named A.  As he says, '"a  T u r i n g machine i s a d e v i c e w i t h a f i n i t e number of i n t e r n a l c o n f i g u r a t i o n s , each of which i n v o l v e s the machine's one of a f i n i t e number of s t a t e s , . . . "  being i n  I presume t h a t any  p a r t i c u l a r s t a t e of T i s d e f i n e d as a unique c o m b i n a t i o n of c e r t a i n c i r c u i t s being  a c t i v a t e d , c e r t a i n c i r c u i t .breakers  open, and c e r t a i n vacuum tubes o p e r a t i n g  and f u r t h e r t h a t  c i r c u i t s are dead, o t h e r c i r c u i t b r e a k e r s are c l o s e d and vacuum tubes are not o p e r a t i n g .  being other  other  I t may be the case however t h a t  the c o n d i t i o n of some components of the machine are i r r e v e l a n t i n the d e t e r m i n a t i o n  of some s t a t e , (say) s t a t e A.  F o r the ,  d i s c u s s i o n i n t h i s s e c t i o n , l e t usi d e f i n e s t a t e A as t h a t s t a t e of a T u r i n g machine i n which f l i p floip 36 i s on and a l l the o t h e r c i r c u i t s are i r r e v e l a n t .  T h i s l a s t c l a u s e , "and a l l the  o t h e r c i r c u i t s are i r r e l e v a n t " can be expanded  into a f i n i t e  list.  components of  Instead  of s p e c i f y i n g whether the o t h e r  the machine should  be c l o s e d or n o n - o p e r a t i o n a l ,  we can say  i f some c i r c u i t w h i c h i s i r r e l e v a n t t h a t i t can be e i t h e r open or c l o s e d , e i t h e r o p e r a t i o n a l or n o n - o p e r a t i o n a l .  In this  we can expand the d e f i n i t i o n of s t a t e A i n t o a f i n i t e l i s t ,  way such  as, f l i p f l o p 36 i s . on, f l i p f l a p 1 i s e i t h e r on or o f f , f l i p flo\p 2 i s e i t h e r on or o f f , e t c .  As I s a i d , t h i s d e s c r i p t i o n i s  f i n i t e because t h e r e a r e a. f i n i t e number of components i n any  6  machine.  We can now g e n e r a l i z e our d e s c r i p t i o n o f what a s t a t e  i s hy s a y i n g t h a t any s t a t e o f a T u r i n g machine i s e q u i v a l e n t to a l i s t o f t h e v a r i o u s components o f t h e machine s t a t i n g e i t h e r t h a t they a r e on, o f f , o r e i t h e r on o r o f f ; a c t i v e , i n a c t i v e or e i t h e r ; a c t i v e or i n a c t i v e ; e t c .  Thus any p a r t i c u l a r  s t a t e c o u l d he p i c t o r i a l l y r e p r e s e n t e d by a p l a n o f t h e machine showing t h e c o n d i t i o n s o f t h e v a r i o u s c i r c u i t s , c i r c u i t b r e a k e r s , t u b e s , magnetic, f i e l d s , r e l a y s , e t c . ^ We c o u l d b u i l d i n t o T a sub-machine  (sub-T) which  c o u l d check t h e c o n d i t i o n o f t h e v a r i o u s components o f T and w h i c h would p r i n t - o u t (say) onto t h e i n p u t tape o f T, t h e r e s u l t s t h a t i t obtained'.  I f we w i s h t o check f o r t h e v a r i o u s  t h a t T i s i n , i t w i l l s i m p l i f y our j o b c o n s i d e r a b l y  states  i f we  determine what a r e t h e s u f f i c i e n t f e a t u r e s o f each p a r t i c u l a r s t a t e w h i c h d i f f e r e n t i a t e i t from a l l t h e o t h e r s t a t e s o f T. Then we c o u l d speak of t h e s u f f i c i e n t c o n d i t i o n s f o r any p a r t i c ular state.  There w i l l be many o f t h e c h n f i g u r a t i o n s o f s t a t e  B which a r e d i f f e r e n t from C o r D but n o t from E o r F.  But  t h a t c o n f i g u r a t i o n s ; - o f t h e v a r i o u s components o f T w h i c h i s s u f f i c i e n t t o d i f f e r e n t i a t e some s t a t e from a l l t h e o t h e r s w i l l be c a l l e d t h e s u f f i c i e n t c o n d i t i o n s o f t h a t s t a t e . Now t h a t we have t h i s machine, we can ask i t t o v e r i f y the statement  m  I am i n s t a t e A when and o n l y when f l i p flo.p 3 6  i s on."" To g i v e a p l a u s i b l e s i t u a t i o n f o r t h i s t o a r i s e , imagine t h a t we have j u s t b u i l t T and t h e o r e t i c a l l y t h e p o s i t i o n of f l i p f l o p 3 6 s h o u l d be t h e s u f f i c i e n t c o n d i t i o n f o r s t a t e A. We ask the. machine t o check ( o r as Putnam c o n s i d e r s , t h e machine i t s e l f considers  c h e c k i n g ) t h e above statement.  The method  . would be t h e o r e t i c a l l y s i m p l e .  The machine e n t e r s s t a t e A  sub-T r e p o r t s the c o n d i t i o n of. f l i p f l o p .36.  and  The machine then  e n t e r s every o t h e r s t a t e (which i s a f i n i t e number) and the r e p o r t s of sub-T on f l i p f l o p 36  compares  to the f i r s t . r e p o r t .  If  the subsequent r e p o r t s are a l l d i f f e r e n t t h a n the f i r s t one, proposition i s true.  7  the  There i s however a v a s t p r a c t i c a l problem  of g e t t i n g the machine to go t h r o u g h every o t h e r s t a t e , and making sure t h a t none are m i s s e d .  However, t h i s a s i d e ,  the  statement seems open to an e m p i r i c a l s o l u t i o n , making i t synthetic. •  7  Putnam wants to say' t h a t i f some b r i g h t p e r s o n r a i s e d the q u e s t i o n of the i d e n t i t y of s t a t e A and f l i p . f l o p 36  being  on, the same o b j e c t i o n s c o u l d be r a i s e d a g a i n s t i d e n t i t y i n the machine case as are r a i s e d i n the case of the i d e n t i t y of i n p a i n and C - f i b r e s being i s argued t h a t s i n c e  stimulated.  I n the m i n d - b o i y . c a s e i t  t h e r e are d i f f e r e n t ways of knowing about the  s t a t e s t o be i d e n t i f i e d , the two  s t a t e s c o u l d not be  identical.  These same c o n s i d e r a t i o n s h o l d i n the machine case. The t h a t T d e t e r m i n e s the s t a t e of f l i p f l o p 36, of sub-T, and  the way  being  i s from the  way reports  t h a t i t determines w h a t . s t a t e i t i s i n ,  i s from the o r i g i n a l i n p u t order t o e n t e r the s t a t e . are two d i f f e r e n t ways of knowing about the two  So  states.  s t a t e A i s not i d e n t i c a l w i t h . f l i p f l o p 36 being on".  At  there Thus this'  p o i n t Putnam l e a v e s the reader w i t h the c h o i c e of s a y i n g e i t h e r t h e r e is-a  'mind-body' (or l o g i c a l - p h y s i c a l s t a t e ) problem w i t h machines  or e l s e the  •  human mind-body problem i s m e r e l y l i n g u i s t i c .  B e f o r e we t a k e  Putnam's c h o i c e , l e t us go back and see whether o r n o t t h e considerations  are a c t u a l l y p a r a l l e l .  I gave an example e a r l i e r . i n which t h e statement '''I am i n s t a t e A i f and o n l y i f f l i p f l o p 36 i s c l o s e d " was s y n t h e t i c . But t h e example I gave t o i l l u s t r a t e t h a t , was t h e case o f checking  t h e o p e r a t i o n o f some machine which had j u s t been  constructed.  . I t i s a normal a s s u m p t i o n i n t h e d i s c u s s i o n o f  machines t h a t we a r e o n l y c o n s i d e r i n g i.e.,  ' t h e o r e t i c a l machines; 1  those t h a t never have m e c h a n i c a l f a i l u r e s .  I assume t h a t 8 9  Putnam i s t a l k i n g about t h e same machines t h a t T u r i n g ,  Church,  and Davis" "^ were, and these were t h e o r e t i c a l machines.  If Ti s  1  a t h e o r e t i c a l machine t h e n , t h e case I gave t o i l l u s t r a t e t h e s y n t h e t i c n a t u r e o f t h e statement c o u l d n o t a r i s e .  By d e a l i n g  w i t h t h e o r e t i c a l machines we e l i m i n a t e t h e p o s s i b i l i t y . o f malfunction  i n t h e machine, so t h e problem o f s e e i n g whether o r  not t h e machine f u n c t i o n s as d e s i g n e d cannot a r i s e . But perhaps t h e r e i s a f u r t h e r sense i n which t h e statement i s s y n t h e t i c .  I s n ' t i t an e m p i r i c a l q u e s t i o n as t o  whether o r n o t t h e p o s i t i o n o f f l i p f l o p 36 i s t h e s u f f i c i e n t c o n d i t i o n o f s t a t e A, i . e . i s t h e p o s i t i o n o f f l i p flo.p 36 t h e f e a t u r e o f t h e i n t e r n a l c o n d i t i o n o f t h e machine which makes t h e s t a t e A d i f f e r e n t from a l l other  states?  But t h i s q u e s t i o n i s  not t h e o r i g i n a l q u e s t i o n but r a t h e r t h e one as t o whether " I am i n s t a t e A i f f l i p flo.p 36 i s c l o s e d . "  T h i s i s o f course  r a t h e r o b v i o u s because t h e n e c e s s a r y and s u f f i c i e n t  conditions  are a complete d e s c r i p t i o n o f t h e c i r c u i t s , c i r c u i t  breakers,  and  tubes b e i n g  on,off or e i t h e r , i n the proper c o n f i g u r a t i o n  9 for  s t a t e A.  That these c o n f i g u r a t i o n s  not an e m p i r i c a l or s y n t h e t i c q u e s t i o n  are the p r o p e r ones i s but r a t h e r a q u e s t i o n  naming or d e f i n i n g j u s t w h i c h c o n f i g u r a t i o n would be s t a t e S i n c e t h statement " I am 36  i s c l o s e d " i s ane  i n s t a t e A i f and  up;  A.  only i f f l i p f l o p  about the n e c e s s a r y and  of s t a t e A, i t i s a m a t t e r o n l y of the way  of  sufficient  conditions  the machine was  set  i . e . , a m a t t e r of the i n i t i a l s t i p u l a t i o n . That t h e d d e f i n i t i o n - o f s t a t e A i s a m a t t e r of  s t i p u l a t i o n though, does not p r e v e n t the q u e s t i o n d e f i n i t i o n of s t a t e A b e i n g asked.  The  or some programmer u n f a m i l i a r w i t h T may the p r o p o s a l  " I am  i n s t a t e A i f and  initial  about  machine may consider,  the  consider, the t r u t h  o n l y i f - f l i p f l o p 36  of  is  on".  T h i s w i l l be a d i f f i c u l t , but not i n s o l u b l e problem, but  this  a l o n e w i l l not  initial  show the p r o p o s i t i o n to be s y n e t h i c .  assumptions - of any  The  system, or the o r g i n a l c o n s t r u c t i o n a l  correspondences of any machine, may  be d i f f i c u l t to determine  but t h i s does not p r e v e n t them from b e i n g s t i p u l a t i o n s (or axioms or d e f i n i t i o n s ) . which one may  Thus the f a c t t h a t t h e r e  i s q u i t e a problem,  f a i l t o s o l v e , i n a s c e r t a i n i n g the  s t i p u l a t i o n s of the v a r i o u s  initial  s t a t e s of the machine., does not  show t h a t these c o r r e l a t i o n s (namings, s t i p u l a t i o n s ) are  not  analytic. The s t a t e A and  main argument however i s , t h a t the ways of d e t e r m i n i n g the p o s i t i o n of f l i p f l o p 36  i t . seems an e n t i r e l y c o n t i n g e n t t h i n g s are i d e n t i c a l . b e ' i n s t a t e A and was  not on."  "For  are d i f f e r e n t , and  m a t t e r whether or not the  thus two  i n s t a n c e , " Putnam s a y s , "the machine might  i t s sense organs might r e p o r t t h a t f l i p f l o p  I n which case the machine would have to d e c i d e  36  10  whether t o say t h e p r o p o s i t i o n was f a l s e o r t o a t t r i b u t e t h e discrepancy  to observational error.  T h i s problem which Putnam  poses f o r t h e machine c o u l d never a r i s e w i t h a T u r i n g machine because we a r e assuming t h a t t h e machine f u n c t i o n s c o r r e c t l y • for  as l o n g as we want i t t o .  So t h e r e i s no p o s s i b i l i t y o f an  o b s e r v a t i o n a l e r r o r i n a T u r i n g machine, and i f t h e r e was an ' ' o b s e r v a t i o n ' o f f l i p f l o p 36 b e i n g o f f when t h e machine was i n s t a t e A, t h e n t h e o n l y c o n c l u s i o n i s t h a t t h e g i v e n statement i s false.  B u t i f t h e exact problem which Putnam r a i s e s c a n n o t 1  a r i s e , s t i l l we have t h e f a c t t h a t t h e r e a r e two independent ways o f v e r i f y i n g each, p a r t o f t h e p r o p o s i t i o n . , r.->\<; ~ ; c S ' ^ : : T h e  -..  way t h e machine d e t e r m i n e s t h e p o s i t i o n o f  f l i p f l a p 36 i s from t h e . i n p u t r e p o r t o f sub-T.  But how does T  determine w h i c h s t a t e i t i s i n ? The machine d e t e r m i n e s t h i s from t h e i n i t i a l i n p u t o r d e r which was g i v e n i t ( o r even which i t gave i t s e l f . )  .At no time does t h e machine d i r e c t l y observe  t h a t i t i s i n s t a t e A as Putnam c l a i m s .  The machine i n f e r s  from t h e e v i d e n c e o f t h e i n p u t o r d e r t o t h e a c t u a l i n t e r n a l configuration.  A l s o t h e machine i n f e r s from t h e e v i d e n c e o f '  the i n p u t r e s u l t s of sub-T t o t h e a c t u a l i n t e r n a l c o n f i g u r a t i o n . Thu's i n ^ d e t e r m i n i n g whether i t i s i n s t a t e A o r whether breaker  circuit  36 i s on, t h e machine makes an" i n f e r e n c e f r o m evidence  which i s p r e s e n t e d  to i t .  Although  the evidence i s d i f f e r e n t ,  the method o f v e r i f i c a t i o n i s the- same i n b o t h F u r t h e r m o r e , sincerwe  cases.  are dealing with t h e o r e t i c a l  machines, we assume t h a t no m e c h a n i c a l f a i l u r e s occur and t h a t t h e r e have been no m i s t a k e s  i n programming.  So, f o r a T u r i n g  machine i t i s n o t p o s s i b l e t h a t T be g i v e n an o r d e r and f a i l t o  11  execute i t o r t h a t sub-T r e p o r t i n c o r r e c t l y . Thus both the i n p u t o r d e r and t h e r e p o r t o f sub-T become d e f i n i t i o n a l for  s t a t e A.  Therefore,  criterion  i f the p r o p o s i t i o n " I am i n s t a t e A"  means t h a t t h e machine has been g i v e n the o r d e r t o e n t e r  state  A, e i t h e r by i t s e l f o r some programmer, and s i n c e f l i p flo.p 36 being  on i s a n e c e s s a r y c o n d i t i o n f o r s t a t e A, t h e n the-  p r o p o s i t i o n " I am i n s t a t e A i f and o n l y i f f l i p flo.p 36 i s on"  i s a n a l y t i c f o r a T u r i n g machine.  On b o t h a c c o u n t s t h e n  the case of the machine i s d i f f e r e n t f r o m the human case.  The  p r o p o s i t i o n '"I am i n s t a t e A i f and o n l y i f f l i p flo.p 36 i s on'" i s a n a l y t i c whereas the analogous p r o p o s i t i o n " I am i n p a i n i f and  o n l y i f my C - f l b r e s a r e s t i m u l a t e d " i s s y n t h e t i c .  The ways  i n w h i c h the machine v e r i f i e s b o t h the s t a t e i t i s i n and the c o n d i t i o n o f f l i p flo.p 3.6 a r e t h e same-.  Whereas., i n the human  case t h e r e i s an i n - p r i n c i p l e d i f f e r e n c e between the ways o f v e r i f y i n g t h a t one i s i n p a i n and t h a t one's C - f i b r e s a r e stimulated.  So Putnam has n o t b u i l t an analogous case w i t h  T u r i n g machines. Putnam t h e n t u r n s t o showing t h a t the q u e s t i o n o f whether a machine 'knows' what s t a t e i t i s i n , i s a degenerate 12  question.  I f he can show t h a t i t i s degenerate .in a way  that  the s i m i l a r q u e s t i o n about human knowledge o f m e n t a l s t a t e s i s , t h i s w i l l add more e v i d e n c e t o t h e analogy between l o g i c a l s t a t e s o f a machine and m e n t a l s t a t e s o f a human. compares the two q u e s t i o n s  So he  "Does the machine ' a s c e r t a i n ' t h a t  i t i s i n s t a t e A?" and "Does Jones 'know' t h a t he i s i n p a i n " i n order  t o show t h a t q u e s t i o n s  about the meithod o f a t t a i n i n g  knowledge o f i n t e r n a l machine s t a t e s .  He hopes t o show t h a t  12 .they are b o t h d e g e n e r a t e , but I s h a l l argue t h a t the  questions  about machine methods are e i t h e r not degenerate or i f they  are,  not f o r the same reasons t h a t q u e s t i o n s of method are f o r m e n t a l states. There i s one  obvious sense i n which i t can e a s i l y be  s a i d t h a t the machine computed s t a t e A, and  t h a t i s the  case  where the machine goes t h r o u g h a s e r i e s of c a l c u l a t i o n s which t e r m i n a t e s i n s t a t e A.  But  I t a k e i t t h a t Putnam i s i n t e r e s t e d  i n the case of whether or not a machine can be t h a t i t i s i n s t a t e A from s t a t e A a l o n e . the q u e s t i o n though, we must add  one  s a i d to compute  Before  more f e a t u r e  considering to our' machine  T, by supposing that' whenever the machine i s i n one s t a t e (say s t a t e A ) , i t p r i n t s out the words " I am T h i s can be done i n two  ways:  e i t h e r every time we  particular i n state give  A".  the  machine an i n s t r u c t i o n to e n t e r s t a t e A, we n e x t g i v e i t the i n s t r u c t i o n t o p r i n t out  " I am  the machine so c o n s t r u c t e d i t a l s o p r i n t s out  " I am  i n s t a t e A",  or e l s e we  t h a t every time i t e n t e r s s t a t e A i n s t a t e A".  The  q u e s t i o n may  a r i s e "Does the machine ' a s c e r t a i n ' t h a t i t i s i n s t a t e A c c o r d i n g t o Putnam, ' a s c e r t a i n ' i s synonymous w i t h or  'work out';  now A?"  'compute'  so the q u e s t i o n can be r e p h r a s e d as "Does the  machine ' a s c e r t a i n 13 A?"  can have  1  (or compute or work out.) t h a t i t i s . i n a s t a t e  I f we have a machine i n w h i c h a f u r t h e r i n s t r u c t i o n i s  g i v e n i t to p r i n t out  " I am  the above q u e s t i o n i s y e s , about how  i t ascertains  programming r e q u i r e d .  i n ' s t a t e A",  t h e n the answer t o  and. the answer t o the f u r t h e r query  or w o r k s • i t  out  i s g i v e n by showing  the  I n t h i s p a r t i c u l a r case i t i s a m a t t e r  of the i n s e r t i o n of a s u b - r o u t i n e ( g r a n t e d i t i s a s h o r t one  of  13 one  i n s t r u c t i o n ) a f t e r the i n s t r u c t i o n to enter  i f we -have t h i s type o f machine, t h e q u e s t i o n But  s t a t e A.  So  i s n o t degenerate.  i f we have a machine t h a t has b u i l t i n t o i t a  programme such t h a t every time i t e n t e r s  s t a t e A i t p r i n t s out  " I am i n s t a t e A", t h e n t h e p r i n t i n g out becomes p a r t o f t h e d e s c r i p t i o n , and thus a d e f i n i t i o n a l c o n d i t i o n o f .the machine b e i n g i n state": A. ated.)  (Mechanical e r r o r s are t h e o r e t i c a l l y e l i m i n -  I f t h i s i s t h e case t h e n i t l o s e s i t s analogy w i t h t h e  human s i t u a t i o n o f someone ' e v i n c i n g ' " I am i n p a i n " , f o r t h e v e r b a l statement i s not^'part  of. the d e s c r i p t i o n o f p a i n and n o t  a d e f i n i t i o n a l c o n d i t i o n of being i n pain.  The q u e s t i o n  about  the machine a s c e r t a i n i n g o r computing t h a t i t i s i n s t a t e A becomes degenerate because t h e f a c t t h a t t h e machine p r i n t e d out " I am i n s t a t e A" i s a d e f i n i t i o n a l c r i t e r i o n o f t h e machine's b e i n g i n s t a t e A. has,  Putnam says t h a t t h e d i f f i c u l t y of degeneracy  i n both cases t h e same cause:  "namely, t h e d i f f i c u l t y i s  o c c a s i o n e d by t h e f a c t t h a t t h e v e r b a l r e p o r t and But  ( I am i n s t a t e A  I am i n p a i n ) i s s u e d d i r e c t l y from t h e s t a t e i t r e p o r t s . . . t h e p r i n t out " I am i n s t a t e A" i s n o t a r e p o r t , b u t a p a r t  of what i s s t i p u l a t e d as b e i n g i n s t a t e A; r e p o r t s can be m i s t a k e n , but n o t d e f i n i t i o n a l c r i t e r i o n .  The q u e s t i o n  about t h e  machine computing " I am i n s t a t e A" from s t a t e A i s a d e s c r i p t i o n because p a r t o f what i s s e t up i n t h i s machine a s s t a t e A i s a d e s c r i p t i o n o f t h e p r i n t - o u t mechanism p r i n t i n g " I am i n s t a t e A", and n o t as Putnam t h i n k s because '"I am i n s t a t e A" i s s u e s d i r e c t l y from t h e machine's b e i n g i n s t a t e A.  However t h e  statement '"I am i n p a i n " , i f i t i s d e g e n e r a t e , i s not; so f o r t h e s e reasons.  I n t h e human c a s e , a p e r s o n s a y i n g t h a t t h e y a r e i n  p a i n i s not. a n e c e s s a r y c o n d i t i o n e i t h e r f o r them knowing t h e m s e l v e s ' t h a t t h e y a r e i n p a i n nor f o r someone e l s e knowing that they are i n pain.  The r e l a t i o n between the statement " I  am i n p a i n " and the p a i n i s q u i t e c o n t i n g e n t ,  and i t i s t h i s  f a c t which g i v e s r i s e , i n the human s i t u a t i o n , to. t h e  question  of knowing about the p a i n i n o r d e r t o 'evince ' " I am i n pain'" . 1  1  T h i s analogous s i t u a t i o n does n o t a r i s e i n a T u r i n g machine. the q u e s t i o n  of how a machine computes or works out what  So  state  i t i s i n , i s n o t u s u a l l y d e g e n e r a t e , but when the q u e s t i o n i s , i t i s n o t degenerate f o r the reasons t h a t q u e s t i o n s o f knowing pain  ( i f those q u e s t i o n s a r e a c t u a l l y degenerate) .are. To c o n t i n u e h i s analogy between machines and humans, Putnam  shows t h a t t h e r e a r e two t y p e s of machine s t a t e s , l o g i c a l  states  and s t r u c t u r a l s t a t e s , and t h a t these a r e analogous t o t t h e m e n t a l and p h y s i c a l s t a t e s o f human b e i n g s .  As I mentioned e a r l i e r ,  any t h e o r e t i c a l T u r i n g machine i s capable o f b e i n g i n a f i n i t e number of, s t a t e s , A, B, C,  and i f the v a r i o u s  of t h i s machine a r e a l r e a d y  i n memory, t h e n the machine w i l l  change from one s t a t e t o a n o t h e r a c c o r d i n g But  programmes  as Putnam says "a g i v e n  t o i t s programming.  'Turing machine' i s an a b s t r a c t  machine w h i c h may be p h y s i c a l l y r e a l i z e d i n an almost i n f i n i t e number o f d i f f e r e n t ways,"  y  and, f o r ' any p a r t i c u l a r manufactured  machine t h e p h y s i c a l c o n d i t i o n o f i t mayvyary from one to a n o t h e r .  condition  Thus any a c t u a l machine may be i n a number of  p h y s i c a l or s t r u c t u r a l s t a t e s and y e t may ' s ' t i l l be i n the same l o g i c a l state.  So f o r any p a r t i c u l a r machine i t can be thought  of or d e s c r i b e d  as a f i n i t e number o f l o g i c a l s t a t e s o r as a  number o f s t r u c t u r a l s t a t e s , and the f u n c t i o n i n g of the. machine  15 can be-expressed e i t h e r e n t i r e l y i n terms o f l o g i c a l s t a t e s , o r again, e n t i r e l y i n s t r u c t u r a l states.  This i s , according to  Putnam,' analogous t o t h e human s i t u a t i o n i n which t h e f u n c t i o n i n g of t h e human can be e x p l a i n e d i n terms o f m e n t a l (e.gFreudian  occurrences  e x p l a n a t i o n ) o r i n terms o f p h y s i o l o g i c a l changes  (e.g., complete b e h a v i o u r a l d e s c r i p t i o n ) . In  o r d e r t o a s s e s s t h i s analogy,  l e t us b a c k t r a c t t o t h e  d i s t i n c t i o n between l o g i c a i a a n d s t r u c t u r a l s t a t e s and c o n s i d e r b r i e f l y a g a i n j u s t what a r e l o g i c a l s t a t e s .  When we s e t up a  T u r i n g machine, we s a i d t h a t i t c o u l d e n t e r a f i n i t e number o f s t a t e s , A, B, C, ... e t c '  These s t a t e s r e f e r r e d t o something  more o r l e s s e x p l i c i t ; namely t h e i n t e r n a l c o n f i g u r a t i o n o f some h y p o t h e t i c a l machine.  These s t a t e s o f t h e machine, A, B, C, ...  must be e x p l i c i t , a t l e a s t t o t h e e x t e n t t h a t we can see t h a t we can b u i l d some machine t h a t w i l l enter, these s t a t e s .  Thus  i f t h e p a r t i c u l a r s t a t e we a r e t a l k i n g about i s one i n w h i c h t h e machine p l a c e s t h e i n p u t d a t a i n t o memory space ^683, we must be a b l e t o show t h a t a machine can be b u i l t which w i l l this functionand  fulfil  c o n s e q u e n t l y be a b l e t o e n t e r t h i s s t a t e .  This  c o u l d be done by l a y i n g out on t h e d r a f t i n g board t h e p o s s i b l e c o n f i g u r a t i o n s o f c i r c u i t s , r e l a y s , and vacuum tubes such t h a t any machine w h i c h was b u i l t from these p l a n s would be a b l e t o enter t h i s p a r t i c u l a r s t a t e .  T h i s requirement  that the states  of a T u r i n g machine r e f e r a t l e a s t t o one p o s s i b l e c o n f i g u r a t i o n of a machine, i s a b s o l u t e l y e s s e n t i a l . the e n t i r e q u e s t i o n . fulfil  Otherwise we would beg  I f we s i m p l y s a i d t h a t t h e machine c o u l d  such-and-such f u n c t i o n and we d i d n o t s p e c i f y how t h i s  c o u l d be accomplished  m e c h a n i c a l l y , t h e n we would s i m p l y be  16 s a y i n g t h a t machines can do whatever humans can and  I presume  t h a t i t i s j u s t t h i s q u e s t i o n of whether machines can do t h i n g humans can do that-we are t r y i n g to answer. beg  every-  So u n l e s s  the q u e s t i o n , we must be a b l e to s p e c i f y at l e a s t  we  one  m e c h a n i c a l c o n f i g u r a t i o n of a p o s s i b l e T u r i n g machine f o r every s t a t e t h a t we  a t t r i b u t e to machine T.  When we  say t h a t  the  i n t e r n a l c o n f i g u r a t i o n of s t a t e A must be s p e c i f i e d , we do mean t h a t i t must be e x p l i c i t l y l a i d out i n e v e r y minute For example, i f i n s p e c i f y i n g s t a t e A we  not detail.  say t h a t t h e r e must be  a circuit  j o i n i n g the scanner to the memory i n p u t compartment,  we do not  s p e c i f y the l e n g t h of the c i r c u i t , nor the  chemical  c o m p o s i t i o n of the w i r e , nor even f o r t h a t m a t t e r t h a t i t must be a w i r e w h i c h c a r r i e s the i m p u l s e from one  to'the other.  f a c t t h e r e i s no l i m i t t o the v a r i o u s ways t h a t such a c o u l d be  set up.  (The  p u r p o s e , or g o a l ) , and  circuit  c i r c u i t i s s p e c i f i e d by the f u n c t i o n , (or thus t h e r e are an u n l i m i t e d number of  a c t u a l m e c h a n i c a l ways of f u l f i l l i n g We  In  c o u l d a l s o have a messenger boy  the p a r t i c u l a r purpose.  c a r r y the message, but  would not be a mech a n i c a l s o l u t i o n .  this  But we must show t h a t  t h e r e i s a t l e a s t one m e c h a n i c a l s o l u t i o n . ) On the o t h e r hand, f o r any  a c t u a l machine t h e r e w i l l be  a  complete p h y s i c a l d e s c r i p t i o n of the v a r i o u s c i r c u i t s , r e l a y s , t u b e s , e t c . , s p e c i f y i n g the a c t u a l p h y s i c a l make-up of machine.  But  the  these s p e c i f i c a t i o n s must i n c l u d e at l e a s t those  s p e c i f i c a t i o n s w h i c h were l a i d down f o r the t h e o r e t i c a l s t a t e . That i s , those c o n d i t i o n s which we  s p e c i f i e d f o r the T machine  t o be i n s t a t e A must be i n c l u d e d i n (or d e d u c t i b l e from) the p h y s i c a l s p e c i f i c a t i o n s of t h i s - a c t u a l machine-, a l t h o u g h these  17 p h y s i c a l s p e c i f i c a t i o n s w i l l a l s o , d e s c r i b e many p r o p e r t i e s which were n o t i n c l u d e d i n t h e t h e o r e t i c a l c o n s i d e r a t i o n s  o f s t a t e A.  Our i n i t i a l s p e c i f i c a t i o n o f t h e p r o p e r t i e s o f s t a t e A was a b s t r a c t i n t h e sense t h a t i t l e f t open t o t h e e n g i n e e r b u i l d i n g the machine many o t h e r p r o p e r t i e s t o be s p e c i f i e d b e f o r e t h e machine c o u l d be b u i l t .  But t h e computer's p h y s i c a l o r s t r u c t u r a l  d e s c r i p t i o n o f s t a t e A w i l l d i f f e r from t h e t h e o r e t i c a l o r l o g i c a l d e s c r i p t i o n o f s t a t e A o n l y i n t h a t i t d e s c r i b e s more p r o p e r t i e s f o r t h e machine. d e s c r i p t i o n as d e s i g n a t i n g  Thus i f we t h i n k o f t h e s t r u c t u r a l a s e t o f p r o p e r t i e s and c o n d i t i o n s o f  T, t h e l o g i c a l d e s c r i p t i o n w i l l be a s u b - s e t o f t h e s e . Now- i t i s u s u a l l y thought t h a t t h e d i f f e r e n c e between m e n t a l s t a t e s and p h y s i c a l s t a t e s i s one o f a more s e r i o u s n a t u r a  than  j u s t t h a t m e n t a l s t a t e s have t h e same b u t fewer p r o p e r t i e s t h a n physical states. determining  I t i s g e n e r a l l y thought t h a t t h e t e s t f o r  p h y s i c a l p r o p e r t i e s are not a p p l i c a b l e to the  p r o p e r t i e s of mental s t a t e s .  Most o f t h e - . p h i l o s o p h i c a l s p e c u l -  a t i o n o f t h e l a s t few y e a r s has been an attempt t o f i n d some i d e n t i t y p r i n c i p l e between t h e p r o p e r t i e s o f our m e n t a l s t a t e s and those, p r o p e r t i e s which a r e o b j e c t i v e l y a t t r i b u t e d t o o t h e r p e o p l e . .Putnam doesn't even need an i d e n t i t y p r i n c i p l e because t h e r e i s o n l y one t y p e o f p r o p e r t y .  He has f a i l e d t o f i n d two  t y p e s o f t h i n g s between which we need t o f i n d some b r i d g e o r connection.  From a complete p h y s i c a l d e s c r i p t i o n o f a machine  we can deduce t h e t h e o r e t i c a l d e s c r i p t i o n , but u n t i l some i d e n t i t y p r i n c i p l e i s a f f o r d e d by Putnam o r someone e l s e , we cannot deduce t h e m e n t a l d e s c r i p t i o n o f a p e r s o n from h i s physical condition.  T h i s i d e n t i t y p r i n c i p l e w h i c h would  bridge  18 the g u l f between m e n t a l and p h y s i c a l s t a t e s may y e t he found by p h i l o s o p h e r s , , n e v e r t h e l e s s , , what i s c e r t a i n l y t r u e i s t h a t some p r i n c i p l e i s needed.  I n t h e case o f a T u r i n g machine t h e r e i s  no p r i n c i p l e needed because Putnam has f a i l e d t o show t h a t t h e r e i s a type d i f f e r e n c e between t h e p r o p e r t i e s o f l o g i c a l and physical states.  Therefore  t h e d i f f e r e n c e between a l o g i c a l  and p h y s i c a l d e s c r i p t i o n o f a'machine i s n o t analogous t o t h e d i f f e r e n c e between a m e n t a l and p h y s i c a l d e s c r i p t i o n o f some person's p a i n ( s a y ) .  Thus I conclude t h a t t h e l o g i c a l - s t r u c t u r a l  d i s t i n c t i o n w i t h machines i s n o t analogous t o t h e m e n t a l - p h y s i c a l d i s t i n c t i o n i n t h e human s i t u a t i o n . The  c o n c l u s i o n o f t h i s s e c t i o n i s n o t t h a t t h e r e a r e no  problems t o be answered or d i s t i n c t i o n s t o be made w i t h complex T u r i n g machines.  The c o n c l u s i o n i s r a t h e r t h a t t h e problems  . r a i s e d o r t h e q u e s t i o n s asked by a T u r i n g machine a b o u t . i t s e l f are not.problems f o r t h e same r e a s o n s t h a t s i m i l a r about humans a r e .  questions  The machine may ask i t s e l f q u e s t i o n s o f t h e  same form as humans may,' b u t t h e d i f f i c u l t y i s n o t t h e same d i f f i c u l t y t h a t a human has.  S i m i l a r l y , many d i s t i n c t i o n s  can be drawn i n d e a l i n g w i t h complex machines, b u t these a l s o , I conclude,  a r e n o t t h e same d i s t i n c t i o n s which  have n o t e d i n t h e human case.  philosophers  Thus t h e problems which a complex  T u r i n g machine might f a c e a r e n o t t h e same as those t h a t humans t r y t o answer, and i n t h i s sense t h e a n a l o g y between men and machines f a i l s .  ."  -  19  '  SECTION I I I FORMALITY AND  PREDICTABILITY'  •In t h i s s e c t i o n , I w i s h to show t h a t a T u r i n g machine i s a c o n c r e t e i n s t a n t i a t i o n of a f o r m a l ' system, and as such, i s predictable.  My d e m o n s t r a t i o n  t h a t T u r i n g machines are f o r m a l i s  not unique but I f e e l t h a t i t i s i m p o r t a n t t h a t i t should be shown rather e x p l i c i t l y .  Many p h i l o s o p h e r s have argued t h a t i f a T u r i n g  machine i s f o r m a l then G o d e l s Incompleteness 1  Theorem can h e l p us 16  to  some i n t e r e s t i n g c o n c l u s i o n s about machines.  'Some, siich as Lucas  have argued t h a t the Theorem r e f u t e s mechanism; o t h e r s , such 17 and T u r i n g 18' have• argued t h 'a t the Theorem has no Putnam.' on the i n t e r e s t i n g p h i l o s o p h i c q u e s t i o n s .  as  bearing  I s h a l l argue, on the  o t h e r hand, o n l y t h a t T u r i n g machines are f o r m a l and t h a t i n the i m p o r t a n t sense t h a t p h i l o s o p h e r s have concerned  themselves  with,-  these machines are ' p r e d i c t a b l e ' . • B e f o r e e n t e r i n g the problem of showing any l i m i t a t i o n s of a T u r i n g machine, we must demonstrate r a t h e r ' c l e a r l y t h a t any machine can be r e p r e s e n t e d a's a f o r m a l system.  My  demonstration  of t h i s i s e s s e n t i a l l y the one used by M a r t i n D a v i s i n the 19 c h a p t e r of h i s book, C o m p u t a b i l i t y and U n s o l v a b i l i t y . i n the f i r s t  Turing  first  As I e x p l a i n e d  s e c t i o n , a machine can be i n . any one of a number of  c o n f i g u r a t i o n s , q^', qg, q-^,. . .' up to s o m e - f i n i t e l i m i t .  A tape,  d i v i d e d i n t o d i s c r e e t u n i t s , i s f e d i n t o the machine and i n each u n i t t h e r e appears a l e t t e r of a language c o m p r i s i n g a number of symbols, S Q , S ^ , Sg,... up to some f i n i t e number. tape i s f i n i t e , but can be as l o n g as i s needed.  Furthermore the One  of the  essential  f u n c t i o n s of a T u r i n g machine i s t h a t i t i s a b l e , upon the r e c e i p t of a symbol, to change from one  s t a t e (say) q^ to another  s t a t e q^.  Not o n l y can a T u r i n g machine change s t a t e s but i t can a l s o  20  change the symbol on the scanned u n i t or i t can move the tape a l o n g so t h a t the n e x t u n i t i s scanned.  T h i s p o s s i b i l i t y of changing  can be r e p r e s e n t e d by a q u a d r u p l e , such a s , q ^ S p ^ .  The machine  t h a t t h i s i s a quadruple of,' w i l l , i f i t i s i n s t a t e q ,and i s 1  scanning symbol S^, Tsymbol S  2  change t o s t a t e q , and e r a s e S 2  i n the scanned tape u n i t . More g e n e r a l l y ,  1  and put the a quadruple  stands f o r a machine b u i l t t o c a r r y out any i n s t r u c t i o n of the f o l l o w i n g form: when i n s t a t e q and the symbol S„ i s on the tape u n i t b e i n g scanned t h e n change t o s t a t e q  (x^, y or y ^ x) and  e i t h e r change the symbol on the scanned tape u n i t t o S scan the u n i t t o the r i g h t or l e f t . following  or e l s e  I f a machine i s c a p a b l e of  out an i n s t r u c t i o n of t h a t form,- t h e n i t can be  r e p r e s e n t e d by a q u a d r u p l e .  I t i s important to n o t i c e  that  after  the machine has c a r r i e d out t h i s i n s t r u c t i o n , i t i s i n the o r i g i n a l p o s i t i o n a g a i n i n t h a t i t i s i n some s t a t e w i t h a  scanned  u n i t i n f r o n t of i t . Thus the machine i s r e a d y ' t o . c a r r y out another i n s t r u c t i o n of the same form.  However, i f . t h e r e i s no  i n s t r u c t i o n b u i l t i n t o the machine, t h e n when i t reaches t h a t and symbol, the machine w i l l s t o p .  such state  Thus any machine which goes  t h r o u g h a p r o c e s s or s e r i e s of changes from one p o s i t i o n t o another can be r e p r e s e n t e d by a s e r i e s of q u a d r u p l e s . s t a t e s and symbols •be f i n i t e .  is finite,  S i n c e the number of  the number of q u a d r u p l e s w i l l  also  T h e r e f o r e a l l the p o s s i b l e movements of the machine can  be d e s c r i b e d by a s e r i e s of q u a d r u p l e s , so t h a t t h i s s e r i e s a c t u a l l y d e f i n e s the machine"s p o s s i b i l i t i e s . Any p a r t i c u l a r T u r i n g machine can be r e p r e s e n t e d , t h e n , by a s e r i e s of q u a d r u p l e s .  But as I s a i d , when the machine has  f i n i s h e d one change i t i s i n a p o s i t i o n to c a r r y out a n o t h e r . T h i s c o n t i n u o u s change of the machine i s r e p r e s e n t e d by a s e r i e s  21  of d e d u c t i o n s .  I f we  t a k e the -tape t o he g i v e n f o r  any  p a r t i c u l a r machine, t h e n by knowing which u n i t the machine w i l l scan f i r s t and we  the s t a t e t h a t the machine i s i n when i t b e g i n s ,  can deduce, u s i n g  various answer.  the l i s t of q u a d r u p l e s of t h a t machine', the  s t e p s t h a t the machine w i l l go t h r o u g h to a r r i v e a t So c o n s i d e r i n g  the q*s  the o r i g i n a l tape as i n i t i a l  and  S's  as p r i m i t i v e words,  an a x i o m a t i c  system which w i t h  the a d d i t i o n of a few more s t i p u l a t i o n s can be made q u i t e t h i s system r e p r e s e n t s ,  that a Turing  and  axioms, and. the q u a d r u p l e s as r u l e s  of i n f e r e n c e , we have c o n s t r u c t e d  And  the  formal.  i n s y m b o l i c terms the v a r i o u s ' c h a n g e s  machine would go t h r o u g h i n any  a c t u a l problem.  I s h a l l i n what f o l l o w s , s t a t e t h i s f a c t r a t h e r b r i e f l y by  saying 21  t h a t a machine i s a c o n c r e t e i n s t a n t i a t i o n of a f o r m a l F i n a l l y , any  theorems w h i c h a p p l y to f o r m a l  systems, w i l l a l s o a p p l y t o T u r i n g I f we  consider  system, t h e n i t seems t h a t I f we know the  s t a t e of the computer and we know i t s complete l i s t  q u a d r u p l e s t h e n we see  i t s tape.  machine i s f o r m a l  of  can p r e d i c t what the machine w i l l do once However, does i t f o l l o w from the f a c t t h a t a t h a t i t i s p r e d i c t a b l e , and f u r t h e r , i f the  machine i s not p r e d i c t a b l e does t h i s show t h a t i t i s not Now  formal  machines.  whatever the machine does i s p r e d i c t a b l e .  we  systems, as  a computer.as a d i s c r e t e s t a t e machine  whose m o t i o n f o l l o w s some f o r m a l  initial  system.  formal?  t h e r e are s e v e r a l reasons t o suggest t h a t a computer i s not  predictable.  One  r e a s o n may  ledge of "the machine.  b e ' t h a t we  For example, we  doiib-t have enough knowcarP'ctt p r e d i c t ( i n g e n e r a l )  when a c o m p l i c a t e d p i e c e of machinery w i l l break down because we  don't know enough about the manufacture or s t r u c t u r a l  22  c o m p o s i t i o n of the v a r i o u s p a r t s .  But we a t t r i b u t e the  inability  to p r e d i c t s i m p l y t o our l a c k of knowledge which we f e e l t h a t we c o u l d g e t , g i v a h enough time and l a b o r a t o r y space.  That i s , we  h o l d t h a t f o r these reasons machines are not ' i n p r i n c i p l e ' unpredictable.  However, t h e r e are o t h e r reasons f o r the unpred-  i c t a b i l i t y of computers which stem from our i n a b i l i t y to get knowledge.  But t h i s i n a b i l i t y i s not a p r a c t i c a l m a t t e r but a  t h e o r e t i c a l one.  I ' t a k e i t - t h a t the' i m p l i c a t i o n of Heizenberg'-s  U n c e r t a i n t y p r i n c i p l e i s t h a t measurements below f i x e d amounts are of  not p o s s i b l e , f o r the more a c c u r a t e l y we measure the p o s i t i o n a p a r t i c l e the more i n a c c u r a t e w i l l be our measurement of i t s  momentum. of  So much so t h a t i f we ever d i d measure the p o s i t i o n  a p a r t i c l e c o m p l e t e l y a c c u r a t e l y t h e n we would  have made an i n f i n i t e e r r o r i n : i t s momentum.  necessarily  Thus, c o n s i d e r i n g  measurements of the utmost a c c u r a c y , we must, i n p r i n c i p l e , have a f i n i t e magnitude  of e r r o r , and we are u n a b l e t o p r e d i c t greater  a n y t h i n g i n t o an a c c u r a c y ^ t h a n the a c c u r a c y of the accumulated errors.  However as I s a i d , we a r e d e a l i n g w i t h measurements of  g r e a t a c c u r a c y and o f course we w i l l be measuring structures.  sub-atomic  F o r i f we want t o make a measurement of something  to the g r e a t e s t a c c u r a c y we w i l l have t o c o n s i d e r the o b j e c t as a c o l l e c t i o n of sub-atomic p a r t i c l e s .  But i f we c o n s i d e r the  o b j e c t or machine as a m a c r o s c o p i c u n i t , t h e n u s i h g - m a c r o s c o p i c measuring d e v i c e s , we can, w i t h i n e x p e r i m e n t a l e r r o r , measure, t e s t , and..predict the movements of the mechanism.  So i f we  spent  a g r e a t d e a l of time t e s t i n g the v a r i o u s p a r t s of some machines, the  above r e a s o n s would not be s u f f i c i e n t t o show t h a t any  machine i s i n p r i n c i p l e u n p r e d i c t a b l e i n m a c r o s c o p i c u n i t s . I t i s g e n e r a l l y contended, however, t h a t computers  23  iz  w h i c h c o n t a i n randoming d e v i c e s ' a r e i n p r i n c i p l e u n p r e d i c t a b l e . I want .to examine two  types of r a n d o m i z e r s ,  (a) a counter  number of radium atoms to have d i s i n t e g r a t e d i n the p r e v i o u s and  (b).the decimal  e x p a n s i o n of TT .  of  the  half-minute  I take the  counter  as an example o'f a d e v i c e which we can n e v e r , r e g a r d l e s s of  how  much-knowledge we had,- p r e d i c t , i . e . the number w h i c h the counter has o n - i t a t any moment- i s i n p r i n c i p l e u n p r e d i c t a b l e . The  r e a s o n f o r our i n a b i l i t y to p r e d i c t may  be due  to- the  v a r i a t i o n s which a f f e c t the d i s i n t e g r a t i o n of radium atoms b e i n g of such a s m a l l magnitude t h a t the U n c e r t a i n t y P r i n c i p l e our i n v e s t i g a t i o n . ( T h i s would o n l y show t h a t we i n v e s t i g a t e t h e laws governing may  be' some.)  But  limits  cannot  d i s i n t e g r a t i o n although  there  g r a n t i n g t h a t t h e r e are i n the w o r l d  counters  w h i c h are u n p r e d i c t a b l e i n the s t r o n g sense t h a t no i n c r e a s e i n knowledge w i l l ever a v a i l i n p r e d i c t i n g them, what can we about computers which c o n t a i n these  say  devices?  Presumably, a computer w i t h a random d e v i c e w i l l work as f o l l o w s , the machine i s g i v e n the i n s t r u c t i o n to l o o k a t the tape u n i t t o t t h e r i g h t and  t h e r e i s no symbol on t h a t u n i t .  The  symbol i s not w r i t t e n on the u n i t u n t i l the tape i s i n the scanner and  t h e n the symbol which i s w r i t t e n on the u n i t i s  determined by the random d e v i c e . p r e d i c t how because we  I n t h i s way  the machine would operate  no one  after this  could  instruction  c o u l d n o t , i n p r i n c i p l e , know what symbol would be  the tape u n t i l the machine a c t u a l l y d i d scan the u n i t .  on  However  t h i s example i s j u s t another case of adding more i n f o r m a t i o n t o the machine during, i t s c a l c u l a t i o n s . We  can c e r t a i n l y b u i l d  machines t h a t w i l l do some c a l c u l a t i o n s and t h e n come to a h a l t u n t i l more i n f o r m a t i o n i s g i v e n t o i t .  T h i s would be the case  2k  where the machine works out the i n i t i a l  tape i n p u t , and when i t  stops we a l t e r the t a p e , w h i c h i s j u s t the same as g i v i n g i t a new  tape.  Then the machine w i l l work a g a i n t h i s problem.  can make t h i s more s o p h i s t i c a t e d by h a v i n g  the machine  We  itself  add more i n f o r m a t i o n to the tape at c e r t a i n stages of i t s calculations.  And  the case of h a v i n g  a randomizing device  in  the machine i s an example of adding more i n f o r m a t i o n , but i n f o r m a t i o n can not be When we  the  predicted.  o r i g i n a l l y thought of the problem of p r e d i c t i n g  a computer, we were t h i n k i n g of a machine which was c a l c u l a t i o n s t o do.  g i v e n some  I n terms of the machines f o r m a l system, the  case of p r e d i c t a b i l i t y arose where we had  a finite list  q u a d r u p l e s and a g i v e n s e r i e s of tape e x p r e s s i o n s .  of  Then i t was  asked whether or not the machine-' s • movements c o u l d be  predicted.  T h i s i s a l l q u i t e analogous t o the human s i t u a t i o n where we  give  someone a. problem and t h e n t r y to f i g u r e out what t h e i r b e h a v i o u r w i l l be.  But the o r i g i n a l problem was  p r e d i c t how  not one  a,•machine would r e a c t when g i v e n more i n f o r m a t i o n  l a t e r i n the p r o b l e m , i n f o r m a t i o n which we No  of t r y i n g to  one would t h i n k t h a t you had  i c t a b l e i f you proved t h a t we  c o u l d not get  ourselves.  shown a machine to be unpred-  cannot f i g u r e out i n advance  the machine would r e a c t when unknown i n f o r m a t i o n was  fed into i t .  When we ask whether or not machines are p r e d i c t a b l e we whether or n o t , g i v e n a machine and  how  are  asking  the i n f o r m a t i o n f e d i n t o  i t , ' w e can p r e d i c t the subsequent movements of the machine.' The  r a n d o m i z i n g d e v i c e f e e d s i n f o r m a t i o n i n t o the machine  from w i t h i n the machine. the case a t a l l .  The  But I do not t h i n k t h a t t h i s changes  tape t h a t the machine scans i s changed  25 and t h a t c r e a t e s a new a x i o m a t i c b e g i n n i n g f o r the machine.  The  f a c t t h a t the source of the i n f o r m a t i o n i s some d e v i c e w i t h i n the p h y s i c a l bounds of the machine does not make the case, d i f f e r e n t t h a n the one. where more i n f o r m a t i o n i s f e d i n from outside.  I t may  be t h o u g h t , however, t h a t I am p r e j u d i c i n g the  case by making the r a n d o m i z i n g d e v i c e p e r i p h e r a l t o the a c t u a l machine, and t h a t a c t u a l l y the d e v i c e can be b u i l t i n t o the ' e s s e n t i a l ' workings of the machine.  I m y s e l f cannot see  how  t h i s r a n d o m i z i n g e f f e c t c o u l d be e x p r e s s e d i n terms of q u a d r u p l e s and tape e x p r e s s i o n s except i n a w a y . s i m i l a r t o the one above.  suggested  I f we b u i l d the d e v i c e i n t o the e s s e n t i a l workings of the  machine, t h e n we would not have a computer but r a t h e r j u s t a super-randomizer.  The purpose of a randomizer i s t o s u p p l y  random numbers when the machine r e q u i r e s t h a t type of i n f o r m a t i o n , viz.  randjom numbers.  T h e r e f o r e , a computer w i t h a randomizer  i s s t i l l q u i t e p r e d i c t a b l e as f a r as i t s movements are d u r i n g a problem.  concerned  I t i s not p r e d i c a b l e , however, i f d u r i n g the  problem more unknown i n f o r m a t i o n i s f e d i n t o the machine, but t h e n no one ever thought, t h a t a machine was p r e d i c t a b l e under those c o n d i t i o n s . If  .7the  type of randomizer i s one t h a t s e l e c t s numbers  s u c c e s s i v e l y from the d e c i m a l e x p a n s i o n of TT i s completely p r e d i c t a b l e .  ?  t h e n the computer  I f we b u i l d the machine so t h a t  each  time i t r e c e i v e s an i n s t r u c t i o n t o ' s e a r c h , i t s e l e c t s the 1  n e x t number s u c c e s s i v e l y i n the e x p a n s i o n , t h e n the numbers which the computer s e l e c t s w i l l be random.  However i f we know  how many p a s t searches the machine has done, and we know where i n the e x p a n s i o n the computer s t a r t e d , t h e n we can c a l c u l a t e the n e x t number and we w i l l know which a l t e r n a t i v e the machine w i l l  26  follow.  Thus t h e r e are machines w i t h r a n d o m i z e r s which are  together completely predictable.  We  can c o n c l u d e , t h e r e f o r e , from  the d i s c u s s i o n of the two t y p e s of r a n d o m i z e r s , t h a t computers  with  these d e v i c e s i n them are s t i l l p r e d i c t a b l e i n the s t r o n g sense. Furthermore the f o r m a l i t y of the machine i s not u p s e t , because  we  can e a s i l y a l l o w f o r a change i n the i n p u t t a p e , which we s a i d  was  comparable t o the axioms of a f o r m a l system.  A l t e r i n g the axioms  of a system does not d e s t r o y the f o r m a l i t y of the system, i t j u s t makes a new  system t h a t has d i f f e r e n t  \  theorems.  27 SECTION IV WHAT IS BEHAVIOUR? I n h i s a r t i c l e "The M e c h a n i c a l Concept of .Mind",  22  M i c h a e l S c r i v e n p r e s e n t s the f o l l o w i n g argument: the outward s i g n s ( i n c l u d i n g speech) are not i n f a l l i b l e i n d i c a t i o n s of c o n s c i o u s n e s s . I t i s t h e r e f o r e q u i t e c e r t a i n t h a t they arepV n o t , ... the same t h i n g as consciousness.^ :  T h i s argument i s meant t o show t h a t c o n s c i o u s n e s s be reduced  t o outward s i g n s or o b s e r v a b l e b e h a v i o u r .  cannot  Scriven  seems t o have i n mind a d i s t i n c t i o n between the b e h a v i o u r a l and the n o n - b e h a v i o u r a l a s p e c t s of man.  When he t a l k s about two  d i s t i n c t t h i n g s , outward s i g n s and c o n s c i o u s n e s s , S c r i v e n seems to be d i s t i n g u i s h i n g between outward o b s e r v a b l e b e h a v i o u r something  e l s e which i s i n n e r and u n o b s e r v a b l e .  and  I n order to  a s s e s s t h i s argument which I have quoted or any o t h e r s l i k e i t , we.must make c l e a r e r t h i s d i s t i n c t i o n between outward s i g n s and consciousness.  I n p a r t i c u l a r - , i t might be asked  j u s t what are  the outward s i g n s ? . What are the b e h a v i o u r a l a s p e c t s of man? More g e n e r a l l y , t h i s i s j u s t the qu-stion "What i s b e h a v i o u r ? " When p h i l o s o p h e r s t a l k about the p o s s i b i l i t y of t h e r e b e i n g m e c h a n i c a l r o b o t s around,  i t seems t h a t they are a l s o u s i n g  the i d e a of a r o b o t to mark the d i s t i n c t i o n between the b e h a v i o u r a l a s p e c t s o f human e x p e r i e n c e and the n o n - b e h a v i o u r a l a s p e c t s .  1  The  r o b o t i s c o n s i d e r e d t o be a b l e t o behave e x a c t l y l i k e a p e r s o n , even, w i t h some w r i t e r s , t o the p o i n t of b e i n g b a h a v i o u r a l l y i n d i s t i n g u i s h a b l e from o t h e r p e o p l e ; . s o man  t h a t whatever e l s e a  has b e s i d e s b e h a v i o u r , t h a t ' s what makes him d i f f e r e n t  a robot.  No one ever c o n s i d e r s a c t u a l l y b u i l d i n g a r o b o t  from and  p h i l o s o p h e r s are not i n t e r e s t e d i n some supposed f u t u r e problem of d i s t i n g u i s h i n g a c t u a l people from t h e i r m e c h a n i c a l r o b o t slaves!  When we  a conceptual  conceive  d e v i c e to mark the d i s t i n c t i o n between those  which h a v e . j u s t b e h a v i o u r besides.  of m e c h a n i c a l r o b o t s , we are j u s t u s i n g things  and those which have something e l s e  A g a i n , however, b e f o r e we  can c o n s i d e r u s i n g  this  c o n c e p t u a l d e v i c e of m e c h a n i c a l r o b o t s , i t i s i m p o r t a n t d e t e r m i n e j u s t e x a c t l y what i s to be c o n s i d e r e d I t i s g e n e r a l l y thought t h a t i f we to i m i t a t e any human b e h a v i o u r ,  as  to  behaviour.  could b u i l d a robot  t h a t we would not be a b l e to  d i f f e r e n t i a t e the r o b o t from o t h e r people as- f a r as i t s b e h a v i o u r was  concerned.  However, even i f we  g r a n t t h a t a machine c o u l d  be b u i l t t o i m i t a t e any human b e h a v i o u r , t h a t i t was  t h i s would not .mean  i n d i s t i n g u i s h a b l e from a human.  The  f a c t that  can b u i l d a r o b o t t o i m i t a t e any p i e c e of human b e h a v i o u r not prove t h a t we human.  We  Y.  I f we  t h e n we  does .  can b u i l d a r o b o t to behave the same as a  do not u s u a l l y equate ' a c t i n g l i k e '  ' i m i t a t i n g ' them.  we  someone e l s e and  Take the case where X i s s a i d to be  c o u l d show t h a t X was unaware of what Y was  c o u l d not say t h a t X was  i m i t a t i n g Y.  imitating doing,  Furthermore if we  are c o r r e c t , i n s a y i n g t h a t X i s i m i t a t i n g Y, t h e n we  could  c o r r e c t l y a t t r i b u t e some i n t e n t i o n t o X; namely, the i n t e n t i o n to i m i t a t e Y.  Whereas when we  say t h a t so-and-so i s a c t i n g l i k e  another p e r s o n we are i m p l y i n g o n l y c o i n c i d e n c e . ' a c t i n g l i k e ' and e n t a l behaviour and  typical.  Confusing  ' i m i t a t i n g ' i s tantamount to r e d u c i n g c o i n c i d -  to c o n v e n t i o n a l b e h a v i o u r ,  l i k e confusing  similar  There i s c e r t a i n l y a d i f f e r e n c e between on the  hand, two people h a v i n g  s i m i l a r enough c h a r a c t e r i s t i c s to be  one  •29 i n d i s t i n g u i s h a b l e and, on t h e o t h e r hand, people h a v i n g c h a r a c t e r i s t i c s t h e same b u t n o t h a v i n g i s a case o f h a v i n g being  some o t h e r s .  certain  Imitating  some c h a r a c t e r i s t i c s t h e same as whoever i s  i m i t a t e d but not having  some f u r t h e r c h a r a c t e r i s t i c s .  A c t i n g l i k e o r b e i n g a l i k e i s a m a t t e r o f doing  s i m i l a r sorts of  t h i n g s , t h i n g s w h i c h a r e comparable enough t o be c a l l e d t h e same. So i f we a l l o w t h a t i m i t a t i o n o f any p i e c e o f b e h a v i o u r i s p o s s i b l e we can n o t move i m m e d i a t e l y t o t h e c o n c l u s i o n t h a t r o b o t s and humans a r e i n d i s t i n g u i s h a b l e . Thus i f we a l l o w t h a t robots  can be b u i l t t h a t i m i t a t e human b e h a v i o u r ,  i t by no '  means f o l l o w s t h a t they a r e i n d i s t i n g u i s h a b l e , even b e h a v i o u r a l l y , from humans. T h i s c l a i m , t h a t i f we a l l o w t h a t i m i t a t i o n i s p o s s i b l e does n o t prove t h a t men and r o b o t s a r e i n d i s t i n g u i s h a b l e , i s q u i t e compatible  w i t h t h e e v i d e n t f a c t t h a t d u r i n g a performance  an a c t o r may be i n d i s t i n g u i s h a b l e from (say) someone .who i s r e a l l y mad.  F o r t o say t h a t an a c t o r i s i n d i s t i n g u i s h a b l e  d u r i n g a performance i s t o admit ( t a c i t l y ) t h a t t h e r e i s a d e f i n i t e l i m i t t o t h e s i m i l a r i t i e s between a c t o r s and madmen. But t o admit t h a t t h e r e a r e l i m i t s i s t o acknowledge t h a t a c t o r s and madmen a r e r e a d i l y d i s t i n g u i s h a b l e i n a l a r g e r c o n t e x t . However, t h e r e may be cases o f i m i t a t i o n which a r e done so w e l l t h a t one may doubt whether t h e r e a r e any c h a r a c t e r i s t i c s which the i m i t a t o r has f a i l e d t o d u p l i c a t e ; a s o r t o f p e r f e c t i m i t a t i o n . But I f i n d t h i s case g e n e r a l l y i n c o n c e i v a b l e , s i n c e i m i t a t i n g presupposes a ( p a r t i c u l a r ) second-order i n t e n t i o n a l i t y on t h e p a r t o f t h e a c t o r which t h e p e r s o n i m i t a t e d doesiiapfc have.  Unless  one h e l d t h a t i n t e n t i o n a l i t y was e n t i r e l y non-behavioural.,  i.e.,  30 had  no b e h a v i o u r a l m a n i f e s t a t i o n s , t h e n I cannot c o n c e i v e o f a  case o f p e r f e c t  imitation.  However i t i s c e r t a i n l y t h e case  that  i f we a l l o w t h a t r o b o t s can be b u i l t t o i m i t a t e any p i e c e o f human b e h a v i o u r , we c a n n o t conclude from t h i s t h a t t h e y would be i n d i s t i n g u i s h a b l e ,  even as f a r as t h e i r b e h a v i o u r i t s e l f i s  concerned, f r o m humans. However, l e t me t r y t o make c l e a r e r t h e d i s t i n c t i o n t h a t I drew above between t h e problems o f s i m i l a r i t y and tion.  exemplifica-  I n problems o f s i m i l a r i t y we a r e t r y i n g , f o r example, to  1  determine whether some p a r t i c u l a r p i e c e o f b e h a v i o u r can be c a l l e d a smile.  We a r e .troubled  because we do^not have any c l e a r  t e s t f o r d e t e r m i n i n g what c o n s t i t u t e s doubt about how s u c c e s s f u l  smiling.  Or, we may be i n  one must be i n some proposed t e s t i n  o r d e r t o be s a i d t o have s m i l e d .  T h i s i s t h e problem o f t r y i n g  to f i n d adequate t e s t s f o r t h e a p p l i c a t i o n o f some c h a r a c t e r i s t i c s to g i v e n s i t u a t i o n s . successful  By an adequate t e s t , I mean one t h a t i s  o r p o s i t i v e when we say t h a t t h e s i t u a t i o n has t h e  c h a r a c t e r i s t i c , and u n s u c e s s f u l o r n e g a t i v e when t h e s i t u a t i o n . doesiGoi have t h e c h a r a c t e r i s t i c a t t r i b u t e d t o i t . T h i s means t h a t t h e statement of t h e success of an adequate t e s t i s l o g i c a l l y n e c e s s a r y and s u f f i c i e n t f o r t h e s t a t e m e n t . o f the d e s c r i p t i o n of the c h a r a c t e r i s t i c to the given s i t u a t i o n .  Thus  when we r a i s e q u e s t i o n s about- adequacy, :what i s i n doubt i s t h e r e l a t i o n s h i p between t h e c h a r a c t e r i s t i c s a t t r i b u t e d t o some s i t u a t i o n and t h e t e s t s done on t h e - s i t u a t i o n . However, i n t h e o t h e r problem o f f i n d i n g t y p i c a l examples, we may be i n doubt as t o "whether two s u b j e c t s have t h e same c h a r a c t e r i s t i c s because t h e t e s t we have w i l l n o t a p p l y t o one  of them.  Or, i f -we can see t h a t they both have some c h a r a c t e r -  i s t i c i n common, we may t r y t o f i n d some o t h e r w h i c h one has and t h e o t h e r haszipt* thinking  characteristics  T h i s problem may a r i s e ,  now o f r o b o t s , i n which someone says they have produced  an example of-'something  c l a i m i n g t h a t t h e i r product h a g a a l l the  c h a r a c t e r i s t i c s of the other t h i n g s .  T h i s i s t h e problem o f  d e t e r m i n i n g t h e c h a r a c t e r i s t i c s o f any g i v e n s i t u a t i o n which one may s e l e c t t o examine.  Thus t h e r e a r e two d i s t i n c t problems:  t h a t o f d e t e r m i n i n g the. adequacy of t e s t s and t h a t o f d d e t e r m i n i n g the v a r i o u s c h a r a c t e r i s t i c s o f g i v e n s u b j e c t s . I do n o t t h i n k t h a t these, two problems a r e u n r e l a t e d ; i n f a c t I s h a l l argue t h a t one presupposes t h a t t h e o t h e r has been answered.  I t can r e a d i l y be seen, I t h i n k , t h a t i n o r d e r t o  answer t h e q u e s t i o n o f whether o r n o t some proposed s u b j e c t i s to be a d m i t t e d t o another  c l a s s o f o b j e c t s as a t y p i c a l example,  we must have some way o f d e t e r m i n i n g t h e c h a r a c t e r i s t i c s o f t h e members o f t h e group and a l s o o f t h e proposed s u b j e c t .  If.the  proposed example'has a l l t h e c h a r a c t e r i s t i c s o f t h e members o f the group ( t h a t a r e r e l e v a n t t o them b e i n g a g r o u p ) , t h e n t h e example becomes a member.  But t h i s problem c o u l d n o t be t a c k l e d  u n t i l we have some adequate way o f d e c i d i n g when two s u b j e c t s have t h e same c h a r a c t e r i s t i c s .  And t h i s q u e s t i o n o f adequacy  i s none o t h e r t h a n t h e f i r s t problem we n o t e d , t h a t o f d e t e r m i n i n g successful tests f o r characteristics. thought  Furthermore,  u n l e s s we  t h a t t h e problem o f d e t e r m i n i n g success was a t l e a s t  capable o f s o l u t i o n , t h e n t h e second problem c o u l d n o t p r o p e r l y arise.  I f we c o u l d n o t i n p r i n c i p l e f i n d a t e s t f o r some  c h a r a c t e r i s t i c , t h e n we c o u l d . n e v e r for that c h a r a c t e r i s t i c .  t e s t some proposed example  The p r o p o s a l t o t e s t some example f o r  32 a p r o p e r t y assumes t h a t t h e r e i s an adequate t e s t f o r t h a t p r o p e r t y . T h e r e f o r e t o ask t h e second q u e s t i o n presupposes t h a t the f i r s t one o f adequacy can be s o l v e d .  F u r t h e r m o r e t h e second  q u e s t i o n o f t e s t i n g examples c o u l d n o t even a r i s e u n l e s s i t was at l e a s t i n p r i n c i p l e p o s s i b l e t o f i n d a t e s t .  F o r i f we know  a p r i o r i t h a t no. t e s t c o u l d i n p r i n c i p l e be found, then t h e q u e s t i o n s about t e s t i n g s u b j e c t s f o r c h a r a c t e r i s t i c s c o u l d n o t arise. building  T h e r e f o r e b e f o r e we can answer any q u e s t i o n s about examples w i t h some c h a r a c t e r i s t i c s , -the p r i o r q u e s t i o n  of t h e p o s s i b i l i t y o f f i n d i n g adequate t e s t s must be answered. When we t a l k about r o b o t s and t h e i r d i f f e r e n c e s from p e o p l e , we a r e wondering whether.there  a r e some c h a r a c t e r i s t i c s  w h i c h people have t h a t r o b o t s do n o t .  T h i s i s c l e a r l y t h e second  problem; t h e one o f d e t e r m i n i n g t h e e x i s t e n c e o f c h a r a c t e r i s t i c s in various subjects.  S i m i l a r l y any d i s c u s s i o n o f t h e d i f f e r e n c e  of t h e s u b j e c t s w h i c h i l l u s t r a t e outward s i g n s , and o t h e r s w h i c h may have more c h a r a c t e r i s t i c s , i s a g a i n a q u e s t i o n o f t e s t i n g some s u b j e c t s t o see i f they have t h e c h a r a c t e r i s t i c s which o t h e r g i v e n examples have.  Thus t o t a l k about r o b o t s and  p e o p l e , o r outward s i g n s o f b e h a v i o u r  and c o n s c i o u s n e s s ,  presup-  poses t h a t t h e f i r s t q u e s t i o n i s capable of an a f f i r m a t i v e answer.  That i s , i t i s assumed t h a t we can f i n d adequate t e s t s  of b e h a v i o u r .  I n f a c t I don't t h i n k i t would.be going t o o f a r  to say t h a t t h e use o f t h e c o n c e p t u a l d e v i c e , r o b o t , presupposes t h a t b e h a v i o u r , o r examples o f b e h a v i o u r , can be a d e q u a t e l y t e s t e d f o r . . Thus t o a s s e s s t h e opening  argument which was used  by S c r i v e n , we must examine t h e p o s s i b i l i t y o f e s t a b l i s h i n g adequate t e s t s f o r b e h a v i o u r . .  ' 33 So f a r I have s t a t e d the problem o f adequacy characteristics  and t e s t s , and now I would l i k e t o r e s t a t e i t i n  a more g e n e r a l form i n order of t h i s problem. i s t i c we;are,  I n terms o f  t o show t h e fundamental  character  When we say t h a t some s i t u a t i o n has a c h a r a c t e r -  s p e a k i n g more g e n e r a l l y , u s i n g i n a m e a n i n g f u l way,  some concept t o t a l k about the s i t u a t i o n . the c h a r a c t e r i s t i c  The a t t r i b u t i o n o f  ' s m i l e ' can be thought o f as t h e m e a n i n g f u l  use o f t h e concept ' s m i l e ' . . A l t h o u g h I by no means i n t e n d t o equate use and meaning, I do t a k e use t o be c o n c l u s i v e t h a t the. concept has. a meaning.  On t h e o t h e r hand, however,  when we t a l k o f t e s t s we a r e , more a c c u r a t e l y , t a l k i n g the r e s u l t s o f t e s t s which i n d i c a t e situation.  evidence  about  the v a r i o u s p r o p e r t i e s o f a  The statement o f t h e r e s u l t o f some s u c c e s s f u l  test  i s a statement s a y i n g t h a t a g i v e n s i t u a t i o n has been t e s t e d and found' t o have a c e r t a i n p r o p e r t y . be c o n s i d e r e d property.  So t h e r e s u l t s o f a t e s t can  as the statement t h a t a g i v e n s i t u a t i o n has a  The q u e s t i o n o f adequacy  can now be c o n s i d e r e d  g e n e r a l l y as a problem about the r e l a t i o n s h i p  more  between t h e  m e a n i n g f u l useoof a concept i n some s i t u a t i o n and t h e r e s u l t s of v a r i o u s t e s t s on t h a t s i t u a t i o n .  I s h a l l abbreviate  the s t a t e -  ment o f t h i s problem i n what f o l l o w s t o j u s t t h e problem o f t h e relationship  between c o n c e p t s and p r o p e r t i e s , but i t must be r e -  membered t h a t I am t a l k i n g about t h e m e a n i n g f u l use o f a concept i n some p a r t i c u l a r  s i t u a t i o n and t h e t e s t s which can be done on 2k  that s i t u a t i o n .  I have used T a y l o r ' s  i n i t i a l l y about t h e adequacy  question  terminology  i n talking  i n terms o f t e s t s , b u t t h i s  second f o r m u l a t i o n o f t h e problem i n terms o f c o n c e p t s i n the one 26  t h a t Hare uses i n h i s c h a p t e r on "Meaning  and C r i t e r i o n ' .  '3H I want t o l o o k a t t h e p o s s i b l e r e l a t i o n s h i p s between t h e p r o p e r t i e s o f g i v e n s i t u a t i o n s and the. concepts used t o t a l k about these s i t u a t i o n s . to d e s c r i b e ! )  (Note: t a l k about does n o t mean, e x c l u s i v e l y ,  There a r e t h e o r e t i c a l l y q u i t e a number o f r e l a t i o n -  s h i p s and I tend t o group them under two main headings and  (b) n o n - l o g i c a l .  (a) l o g i c a l  The l o g i c a l r e l a t i o n s h i p s a r e v e r y numerous:  ( i ) a p r o p e r t y (p) i s n e c e s s a r y and s u f f i c i e n t f o r tiie- concept ( c ) ( i i ) p i s nece'ssary f o r c, . ( i i i ) p i s s u f f i c i e n t f o r c, (iv)drame group o f p r o p e r t i e s ( p ) a r e s u f f i c i e n t and n e c e s s a r y f o r e , ( v ) p • n  n  i s n e c e s s a r y f o r c, ( v i ) • p group o f p r o p e r t i e s (p (viii) p The  n - k  i s s u f f i c i e n t f o r c, ( v i i ) some o f a  ). a r e n e c e s s a r y and s u f f i c i e n t f o r c,  i s n e c e s s a r y f o r c, ( i x ) p ~ n  k ;  i s s u f f i c i e n t f o r c.  g e n e r a l form o f t h o s e r e l a t i o n s h i p s which a r e n e c e s s a r y and  s u f f i c i e n t i s p *-*c where' k<h and' n^l,k^.o.  Similar  generalforms  can be f o u n d - f o r t h e n e c e s s a r y and f o r t h e s u f f i c i e n t ships.  relation-  I t i s t h e r e f o r e e v i d e n t t h a t t h e r e a r e , i n p r i n c i p l e , no  l i m i t s t o t h e number o f l o g i c a l r e l a t i o n s h i p s between p r o p e r t i e s and c o n c e p t s .  And f i n a l l y those, p r o p e r t i e s which s a t i s f y o r  b e l o n g t o one. o f these r e l a t i o n s h i p s , I s h a l l c a l l a c r i t e r i o n f o r t h a t concept. . Some p r o p e r t i e s however a r e o n l y n o r m a l l y adquate f o r t h e a s c r i p t i o n o f some concept.  That i s t o say t h a t when a s i t u a t i o n  c o n t a i n s a p r o p e r t y , o r s e r i e s o f p r o p e r t i e s , t h e concept i s n o r m a l l y a p p l i c a b l e . T h e r ^ a r e e x c e p t i o n a l c a s e s , o f c o u r s e , but g e n e r a l l y we a r e j u s t i f i e d i n u s i n g t h e concept when these p r o p e r t i e s e x i s t i n some s i t u a t i o n .  The r e l a t i o n s h i p s between t h e p r o p e r t i e s  and t h e concept i s n o t a l o g i c a l one becuase we a r e o n l y n o r m a l l y j u s t i f i e d i n u s i n g t h e concept when t h e g i v e n s i t u a t i o n  exhibits  •3-5 these p r o p e r t i e s . good i n d u c t i v e may  be  (say)  T h i s case may  a r i s e when the p r o p e r t i e s  e v i d e n c e f o r the u s e . o f the concept.  ase  Some  properties  o n l y s u f f i c i e n t i n normal c i r c u m s t a n c e s , f o r  a p p l i c a t i o n of the concept. between the concept and  T h i s means t h a t the  the  relationships  the p r o p e r t y i s such t h a t we  are  not  n o r m a l l y j u s t i f i e d i n u s i n g a concept because of the r e s u l t s of a test.  However because i t i s a . s u f f i c i e n t r e l a t i o n s h i p , we  can  to  generally of the  conclude from the r e s u l t s of a t e s t t h e  applicability  A  concept.  Furthermore, other p r o p e r t i e s  may  be  (say)  e s s a r y , i n normal s i t u a t i o n s , f o r the a p p l i c a t i o n of the i n w h i c h case we would be  j u s t i f i e d i n c o n c l u d i n g from  nec-  concept; the  a p p l i c a b i l i t y of the concept to the r e s u l t s of some t e s t . So we  can have p r o p e r t i e s  which a r e , w i t h i n some normal  range of s i t u a t i o n s e i t h e r necessary, or s u f f i c i e n t or b o t h , f o r . the a p p l i c a t i o n of some concept. s h i p s are not  However the r e l a t i o n -  l o g i c a l ' i n the f o r m a l sense because we  s p e c i f y the range of normal s i t u a t i o n s , nor t h a t w i l l be normal i n the f u t u r e .  But  be n e c e s s a r y or s u f f i c i e n t or b o t h .  properties  which are r e l a t e d to c o n c e p t s , I c a l l indicators.  many r e l a t i o n s h i p s between i n d i c a t o r s and w i t h c r i t e r i o n , but  and  the  These  (following  concepts as t h e r e  the normal r e l a t i o n s h i p s are not  properties,  ranges  There are thus  T h e r e f o r e i t seems t h a t t h e r e are an u n l i m i t e d between concepts and  not  i n normal s i t u a t i o n s  could  2 7  can  s p e c i f y the  properties  m o d i f i e d v e r s i o n of S c r i v e n )  possibly  a as are  logical.  number of  relations  even a l t h o u g h t h e r e are. two  main d i v i s i o n s i n the t y p e s of r e l a t i o n s , even w i t h i n these t y p e s t h e r e i s an u n l i m i t e d The  number of p o s s i b l e  q u e s t i o n now  relations.  a r i s e s q u i t e n a t u r a l l y as to what t y p e s  of concepts our b e h a v i o r a l  ones a r e ?  By b e h a v i o r a l  concepts, I  36 mean those concepts which we use when t a l k i n g about how people behave; such a s , s m i l e , s m i r k , g r i n , and grimace, t o mention o n l y a few from t h e . v a r i o u s f a c i a l e x p r e s s i o n s t h a t people adopt.  It  seems t o me t h a t many o f t h e concepts a r e o f a normal t y p e ; t h a t i s , t h a t t h e r e a r e n o r m a l l y j u s t i f i a b l e i n d i c a t i o n s when people are s m i l i n g , b u t no c r i t e r i o n f o r s m i l e s .  Granting that at l e a s t  at p r e s e n t some o f our b e h a v i o r a l concepts a r e o f a normal  type,  i t may be thought t h a t they c o u l d a l l be changed t o a l o g i c a l t y p e . That i s changed i n t y p e ; but t h e meanings remain the. same. I n t h i s r e g a r d i t i s i n t e r e s t i n g t o c o n s i d e r , as an example o f type r e d u c t i o n a paper  "Can Humans ' F e e l ' ? " by Mr. S. C o v a l  i n which  •he argues t h a t our b e h a v i o r a l concepts may become l o g i c a l as we l e a r n more about t h e human organism.  He argues  types  (roughly)  t h a t we w i l l d e v e l o p b e h a v i o r c o n c e p t s , l i k e " t i r e d " which  will  be i d e n t i f i e d by t h e cause o f t h e c o n d i t i o n o f t h e human. • Thus i f we c o u l d determine t h e e x a c t t e s t s f o r t h e causes o f a p i e c e of  b e h a v i o r we would have t h e c r i t e r i o n f o r t h e use o f t h a t concept.  Now t h i s suggests two a l t e r n a t i v e s , (a) t h a t our p r e s e n t  normal  b e h a v i o r a l concepts c o u l d a l l be made l o g i c a l types by f i n d i n g the t e s t s which a r e c r i t e r i o n .  But here no p r o o f i s o f f e r e d t o  show t h a t t h i s i s p o s s i b l e i n p r i n c i p l e , and I see no r e a s o n t o t h i n k t h a t a l l - n o r m a l ' type concepts c o u l d possibly be made l o g i c a l types.  Or (b) t h a t i f we do d e v e l o p a s e t o f l o g i c a l type b e h a v i o r  concepts,, we w i l l have two s e t s which a r e i r r e d u c i b l e , and I do not know what s o r t o f s t a n d a r d we s h o u l d use t o compare- them, as they a r e d i f f e r e n t t y p e s .  Of course these remarks o f mine about  Mr. C o v a l ' s i d e a s a r e by no means meant as a r e f u t a t i o n , b u t on the o t h e r hand I do n o t see why, when we a r e c o n s i d e r i n g t h e r e l a t i o n s  3 7  between t e s t s and c o n c e p t s , we s h o u l d t a c k l e t h e q u e s t i o n w i t h o n l y one r e l a t i o n i n mind, t h a t o f l o g i c a l l y adequate.  However  more i m p o r t a n t l y , i t i s e v i d e n t from an e x a m i n a t i o n o f C o v a l ' s paper, j u s t where a t h e o r y i s needed i n o r d e r t o succeed i n a. reduction.  The r e d u c t i o n i s t must o f f e r e i t h e r some p r i n c i p l e o f  comparison between concepts;^ which a r e d i f f e r e n t i n type o r e l s e prove a p r i o r i t h a t a l l concepts we p r e s e n t l y use c o u l d be made l o g i c a l i n type w i t h o u t change i n meaning.  I n t h e absence o f e i t h e r  of these p r o o f s , we can n o t conclude that, a l l o f our b e h a v i o r a l concepts which we now employ a r e r e d u c i b l e t o a l o g i c a l t y p e . T h e r e f o r e we can assume i n the' absence o f a r e d u c t i v e t h e o r y , t h a t our p r e s e n t b e h a v i o r a l concepts do n o t have c r i t e r i o n . .Where does a l l t h i s l e a v e Mr. S c r i v e n w i t h h i s m e c h a n i c a l r o b o t s i m i t a t i n g human b e h a v i o r ?  Since a robot i s a mechanical  d e v i c e i t can be t a l k e d about e n t i r e l y i n terms o f a l o g i c a l t y p e . Nowhere i s any p r o o f o f f e r e d e i t h e r by S c r i v e n o r anyone e l s e who t a l k s about r o b o t s t h a t OUT b e h a v i o r a l cnocepts a r e a l l o f a l o g i c a l type.  U n t i l t h e y prove t h a t t h e concepts we u s e t o t a l k about  how humans behave c a n be reduced t o l o g i c a l type terms, t h e n , I argue, t h e q u e s t i o n o f m e c h a n i c a l i m i t a t i o n cannot even a r i s e . E v e r y concept t h a t a p p l i e s t o a a machine i s o f a l o g i c a l t y p e ; p r o b a b l y even o f t h e narrower e s s a r y and s u f f i c i e n t .  c l a s s o f l o g i c a l types c a l l e d  Thus i f some performance  nec-  o r movement ( o r  a c t i o n ) i s t o be accomplished by a m e c h a n i c a l d e v i c e , then t h e e  performance  must be d e s c r i b a b l e i n l o g i c a l c o n c e p t s .  At present  we r e c o g n i z e , t a l k about, and d e s c r i b e human b e h a v i o r u s i n g normal type c o n c e p t s .  But t h e problem o f m e c h a n i c a l i m i t a t i o n can o n l y  a r i s e when human b e h a v i o r i s d e s c r i b e d i n l o g i c a l type terms.  Until  '3:8 i t i s shown t h a t a l l human b e h a v i o r i s d e s c r i b a b l e i n these type of terms, t h e n the problem o f i m i t a t i o n Furthermore  does n o t and cannot  arise.  the opening argument about the i n f a l l i b i l i t y of o u t -  ward s i g n s of c o n s c i o u s n e s s does n o t show t h a t c o n s c i o u s n e s s i s something o t h e r t h a n b e h a v i o r , i t o n l y shows t h a t our concepts about c o n s c i o u s n e s s a r e n o t of a l o g i c a l t y p e , but r a t h e r a r e of a normal type I Now i t becomes e v i d e n t t h a t t h e robot-man d i s t i n c t i o n i s not meant t o mark something o u t e r v s . something  i n n e r , or separate  outward v i s i b l e s i g n s from inward p r i v a t e f e e l i n g s :  but r a t h e r i s  meant t o mark the d i s t i n c t i o n between a d e s c r i p t i o n o f human a c t i v i t i e s i n l o g i c a l type and n o n - l o g i c a l type terms.  Or perhaps  the robot-man d i s t i n c t i o n - can be thought o f as d i s t i n g u i s h i n g  those  b e h a v i o r a l concepts which a r e l o g i c a l from those which a r e n o t . Here, o f course the n o n - l o g i c a l type of concepts a r e those t h a t we use t o t a l k about c o n s c i o u s n e s s .  The q u e s t i o n "What i s B e h a v i o r ? "  has become t h e q u e s t i o n fWhat t y p e s o f concepts do we use f o r b b e h a v i o r ? " and.now perhaps t h e f l y can get out of t h e f l y b o t t l e .  '39 SECTION V A TEST FOU THINKING 29 • At t h e c o n c l u s i o n o f h i s paper "The I m i t a t i o n Game", K e i t h Gunderson tempers some o f h i s p r e v i o u s c r i t i c i s m s w i t h t h e remarks: N e v e r t h l e s s . . . t h e g e n e r a l q u e s t i o n would r e m a i n unanswered: what range o f examples would s a t i s f y t h e i m p l i c i t c r i t e r i o n we use i n our o r d i n a r y c h a r a c t e r i z a t i o n o f s u b j e c t s as "those capable o f t h o u g h t " ? A c o r o l l a r y : I f we a r e t o keep t h e q u e s t i o n "Can machines t h i n k ? " i n t e r e s t i n g , we cannot w i t h h o l d a p o s i t i v e answer s i m p l y on t h e grounds t h a t i t ( a machine) does n o t d u p l i c a t e human a c t i v i t y i n every r e s p e c t . The q u e s t i o n "Can a machine t h i n k i f i t can do e v e r y t h i n g a human being can do?" i s n o t an i n t e r e s t i n g question....30 However I do n o t t h i n k t h a t t h e s e remarks j u s t i f y Mr. Gunderson in qualifying h i s earlier criticisms.  I s h a l l argue t h a t t h e concept  "capable o f t h o u g h t " has no l o g i c a l l y s u f f i c i e n t c r i t e r i o n . t h i s i s so t h e n he need n o t worry about our i m p l i c i t  If  (logical)  c r i t e r i o n f o r t h e concept. . Mr.'Gunderson does n o t f i n d t h e q u e s t i o n about machines t h i n k i n g , i n t e r e s t i n g , i f we g r a n t t h a t machines can do e v e r y t h i n g humans do.  But I should t h i n k t h a t even i f a machine c o u l d do  e v e r y t h i n g , we would s t i l l have s c e p t i c a l grounds f o r w i t h h o l d i n g our m e n t a l c o n c e p t s .  Machines a r e d i f f e r e n t from.humans and d i f f -  e r e n t i n ' a way t h a t o t h e r humans do n o t d i f f e r f r o m each o t h e r . S i n c e a machine i s ;.by d e f i n i t i o n d i f f e r e n t t h a n a human, even i f ' a machine c o u l d do e v e r y t h i n g a human does, t h e q u e s t i o n o f r e l e v a n c e of t h e d i f f e r e n c e s w i l l always a r i s e and I see no r e a s o n t o r u l e i t out a p r i o r i as u n i n t e r e s t i n g .  When we b u i l d a machine t o do •„?  e v e r y t h i n g t h a t humans c a n , we use d i f f e r e n t m a t e r i a l s t o b u i l d with.  Even when we b u i l d a m e c h a n i c a l " b r a i n " we use d i f f e r e n t  >+0 •materials t h a n those t h e b r a i n i s made o f .  And because a machine  i s d i f f e r e n t from a human i n ways t h a t o t h e r humans a r e n o t , t h e s c e p t i c c a n always doubt t h e v a l i d i t y o f t h e a p p l i c a t i o n o f m e n t a l concepts t o machines.  Whether o r n o t t h e s c e p t i c i s j u s t i f i e d i s  another i n t e r e s t i n g q u e s t i o n , b u t one t h a t can always a r i s e w i t h machines d e s p i t e t h e f a c t t h a t they do e v e r y t h i n g . Gunderson's  c o r o l l a r y t h a t we cannot w i t h h o l d a p o s i t i v e  answer s i m p l y on t h e grounds' t h a t machines do n o t d u p l i c a t e human a c t i v i t y i n e v e r y r e s p e c t , seems t o me t o f a i l t o n o t i c e t h i s ever p r e s e n t s c e p t i c a l ground.  I f we c o u l d f i n d one a c t i v i t y which no  machine could- do and' t h i s was a mental a c t i v i t y , t h e n t o g e t h e r w i t h t h e i m p l i c i t s c e p t i c i s m , t h e r e would .be good grounds f o r w i t h h o l d i n g a p o s i t i v e answer.  .This i s t h e r e a s o n t h a t some  p h i l o s o p h e r s have been so impressed w i t h G o d e l s theorem.  Godel  showed t h a t g i v e n any p a r t i c u l a r T u r i n g machine, he c o u l d  always  1  f i n d a theorem which a human c o u l d prove was t r u e b u t t h e machine could not.  Thus t h e r e was a t l e a s t one mental a c t i v i t y , ' i . e . ,  proving the Godelian c o u l d n o t do.  statement o f t h a t machine, which-the machine  When you c o u p l e t h i s f a c t w i t h t h e g e n e r a l d i f f e r e n c e s  between machines  and humans ( o r even b r a i n s ) , t h e n t h e r e a r e good  reasons f o r w i t h h o l d i n g m e n t a l concepts ( e s p e c i a l l y t h i n k i n g ) from machines. Gunderson f e l t however t h a t t h e r e was a g e n e r a l  unanswered  question;, namely, what range o f examples would s a t i s f y t h e i m p l i c i t c r i t e r i a we use i n our o r d i n a r y c h a r a c t e r i z a t i o n o f s u b j e c t s as"those c a p a b l e o f t h o u g h t ? "  I t i s e v i d e n t that, we use tone concept  "capable o f t h o u g h t " w i t h some s u b j e c t s i n some s i t u a t i o n s and not i n others..  Most p e o p l e u n d e r s t a n d t h e concept and we can use  i t , g e n e r a l l y , unambiguously.  That i s t o s a y , t h e concept has a  meaning w h i c h most p e o p l e comprehend.  Now  g r a n t i n g t h a t a concept  has meaning , and f u r t h e r t h a t the meaning can be t a u g h t to o t h e r s I s h o u l d say, f o l l o w i n g W i t t g e n s t e i n t h a t t h e r e must be i n s t a n c e s of the use of the word.  paradigm  There must be some s i t u a t i o n s  i n w h i c h the concept i s lised c o r r e c t l y and we know, g e n e r a l l y , w h i c h s i t u a t i o n s they a r e .  The concept has been t a u g h t t o us and  i s t a u g h t by i t s use i n paradigm s i t u a t i o n s .  However, g r a n t i n g  . a l l t h i s , i t does n o t f o l l o w t h a t t h e r e a r e c r i t e r i a , i m p l i c i t or e x p l i c i t , f o r the use of t h i s concept.  either  More p r o o f  must be o f f e r e d t h a n t h e - f a c t t h a t the concept i s l e a r n e d i n o r d e r ten prove t h a t m e a n i n g f u l concepts have l o g i c a l l y r e l a t e d  criteria.  Y e t the attempt t o f i n d a t e s t assumes j u s t t h i s p o i n t , namely, t h a t t h e r e i s some t e s t which s a t i s f i e s the c r i t e r i a of the concept " c a p a b l e of t h o u g h t . "  There i s however, no p r o o f o f f e r e d t o show  t h a t the concept has c r i t e r i a .  Some people who work w i t h  computers  contend t h a t t h e y can program a computer t o do any t a s k which p e r s o n could do.  They may  be q u i t e j u s t i f i e d i n th&s c l a i m .  t h e n argue t h a t i f . we show them what the s u b j e c t s do when we  any They say  t h a t t h e y a r e c a p a b l e o f t h o u g h t , t h e n they w i l l b u i l d a computer to do t h a t job also.-  Howgv-er t h i s l i n e of r e a s o n i n g presuppdsse©  t h a t t h e r e are a d e f i n i t e number o f s p e c i f i c t a s k s w h i c h , when completed, the l a b e l "capable of t h o u g h t " cannot i n l o g i c a l consistency, be w i t h h e l d .  But.we cannot a l l o w p e o p l e t o argue  because we are t e s t i n g a machine, type.  that  the concept must be of a s p e c i f i c  Rather i t can o n l y be h e l d t h a t i f we are ever going t o  be a b l e t o f i n d a t e s t f o r the a p p l i c a t i o n of the concept, t h e n the concept must have c r i t e r i a .  However i f the concept does n o t  have c r i t e r i a t h e n we cannot f i n d a l o g i c a l l y s u f f i c i e n t t e s t f o r  its application. S c r i v e n t h i n k s t h a t i f we r e f u s e to a p p l y our m e n t a l v o c a b u l a r y , each time they b u i l d a computer t o do. more human achievements, t h e n we w i l l be making a m i s t a k e .  He  says:  •'The l o g i c a l t r a p i s t h i s : no one p e r f o r m a t o r y achievement w i l l be enough'to .persuade us to a p p l y the human achievement v o c a b u l a r y , but i f we r e f u s e to use t h i s v o c a b u l a r y i n each case s e p a r a t e l y , on t h i s ground, we w i l l , perhaps w r o n g l y , have committed o u r s e l v e s to a v o i d i n g i t even when a l l the achievements are s i m u l t a n e o u s l y a t t a i n e d . •.'31 • S c r i v e n seems to t h i n k t h a t t h e r e ' a r e a l l of them) of achievements which one human-achievement v o c a b u l a r y .  a d e f i n i t e number, (namely, does to q u a l i f y f o r the  I f the number i s not d e f i n i t e (and  t h i s does not mean the number i n f i n i t e ) t h e n t h e r e i s no  logical  •3?  trap.  But where i s the p r o o f t h a t a l l of our human-achievement  concepts are of a type t h a t have a d e f i n i t e number of S c r i v e n does not o f f e r one, be g i v e n .  criteria?  and ,1 i n t e n d to show t h a t none  can  I s h a l l aggue t h a t the concept "capable of t h o u g h t "  i s an e v a l u a t i v e ooncept which does not have any  logically  s u f f i c i e n t s e t of c h a r a c t e r i s t i c s so t h a t no t e s t f o r  character-  i s t i c s of p e o p l e . w i l l . e v e r be found t h a t i s l o g i c a l l y  sufficient.  In order  to prove t h i s , however, I must f i r s t b e g i n by  some of the c o n c l u s i o n s  reviewing  t h a t have been reached i n the; a n a l y s i s  of e v a l u a t i v e language. •5-5  I n the f i f t h c h a p t e r of The reformulates  Language of M o r a l s - ^  Moore's c r i t i c i s m of n a t u r a l i s m i n e t h i c s .  Hare In doing  so Hare shows t h a t any attempt to reduce our e v a l u a t i v e terms to the statement of a d e f i n i t e s e t of d e s c r i p t i v e c h a r a c t e r i s t i c s must be i n p r i n c i p l e m i s t a k e n .  He  states:  l e t us g e n e r a l i z e . I f P i s a good p i c t u r e i s h e l d t o mean t h e same as 'P i s a p i c t u r e • and i s C (where C . i s a group o f c h a r a c t e r i s t i c s ) , t h e n i t w i l l become i m p o s s i b l e t o to commend p i c t u r e s f o r beingC: i t w i l l be p o s s i b l e o n l y t o say t h a t they a r e C. It- i s important to r e a l i z e that t h i s d i f f i c u l t y ., ' ' has n o t h i n g t o do w i t h the. p a r t i c u l a r example I have chosen. ' I t i s .not because we have chosen t h e wrong d e f i n i n g c h a r a c t e r i s t i c s ; • i t i s because whatever--defining characteri s t i c s we choose,- t h i s ' o b j e c t i o n a r i s e s , t h a t we can no l o n g e r commend an o b j e c t f o r posse p o s s e s s i n g those c h a r a c t e r i s t i c s . 3 ^ (my p a r e n t h e s i s added) 1  As I s a i d , I a c c e p t e n t i r e l y Hare's p r o o f t h a t i f we a r e t o e v a l u a t e or commend v a r i o u s  s u b j e c t s :for d o i n g o r being  something,.then  we must have e v a l u a t i v e concept's which a r e n o t j u s t  equivalent  to an a s s e r t i o n o f a d e f i n i t e s e t o f c h a r a c t e r i s t i c s o r p r o p e r t i e s . I t i s a f a c t . t h a t we do v a l u e and commend, and as l o n g as we , continue  t o , we must have v a l u e  of any prcoif a p r i o r i  concepts.  Thus i n t h e absence'  t h a t a t some time humans w i l l stop  forever  t o e v a l u a t e , i t can be assumed t h a t we must have e v a l u a t i v e  concepts.  Thus we must have concepts w h i c h a r e n o t e q u i v a l e n t , t o t h e a s s e r t i o n of a s e t o f c h a r a c t e r i s t i c s . The  q u e s t i o n now a r i s e s as t o whether o r n o t when we say  " X c a n t h i n k " , we a r e making an e v a l u a t i v e judgement. V I I I o f h i s paper Gunderson  --'-'''•-"''  In section .  says:  A f i n a l p o i n t : t h e stance i s o f t e n t a k e n t h a t t h i n k i n g i s t h e crowning c a p a c i t y o r a c h i e v e mpnt.^of:..the human r a c e , and t h a t i f one d e n i e s 'that"machines can t h i n k , one i n e f f e e t . a s s i g n s them t o some lower l e v e l o f achievement t h a n t h a t a t t a i n e d by human b e i n g . But one might w e l l contend t h a t machines can't .think f o r t h e y do much b e t t e r t h a n t h a t . 3 5 :;  (my  italics)  I f we o f t e n say t h a t t h i n k i n g i s t h e crowning c a p a c i t y , o r t h e f a c u l t y which makes us b e t t e r , t h a n t o say o f someone t h a t they I  t h i n k i s not o n l y t o say t h a t they have some c a p a c i t y but t h e y are commendable'(or more v a l u a b l e ) we  And  because, they have i t .  c a l l some c a p a c i t y the crowning""one we..are i n - e f f e c t  t h a t .whoever has  If  saying  t h i s c a p a c i t y i s commendable because of i t . ,  .V..\\v  to o f f e r a r e a s o n f o r commendation i s s i m p l y to commend someone  f o r the r e a s o n o f f e r e d .  However I t cannot be d e n i e d t h a t "X  the crowning c a p a c i t y , v i z . a b i l i t y to t h i n k " and are d i f f e r e n t u t t e r a n c e s .  "X can  has  think"  '  I t i s a g e n e r a l l y a c c e p t e d f a c t t h a t people can and  that  think,  i f someone s t a t e s a f a c t w h i c h everyone knows, t h e n i t i s '  g e n e r a l l y assumed t h a t he has  some o t h e r purpose i n mind.  For  example when I t e l l my w i f e , t h a t she a l r e a d y knows, that- the house i s d i r t y , I am not  j u s t s t a t i n g a f a c t but r a t h e r I am  condemning'this c o n d i t i o n of the house and she c l e a n i t .  thus recommending t h a t  So i f someone s t a t e s t h a t people (or some person)  can t h i n k and we  a l l g e n e r a l l y assume t h i s , t h e n we  t h e y have some o t h e r purpose' i n mind i n u t t e r i n g the Now  (say)  when we remember t h a t we  often consider  take i t that sentence.  the a b i l i t y to t h i n k  as a r e a s o n f o r commending p e o p l e , i t i s not d i f f i c u l t t o see on some o c c a s i o n s  that  a t l e a s t , the purpose i n s a y i n g t h a t someone  can t h i n k i s to commend them.  For i f i t i s assumed t h a t L o i s  can t h i n k as i t g e n e r a l l y i s and we  o f t e n recommend  people because  they can t h i n k , t h e n to say t h a t L o i s can t h i n k i s to commend her because she can t h i n k . has  j u s t t h i s use  And  I t h i n k ' t h a t the sentence "X can  of commendation on some o c c a s i o n s  think"  I want to  emphasize t h a t a l l I w i s h to e s t a b l i s h i s t h a t on some o c c a s i o n s . the sentence has  t h i s use, w h i l e not' denying t h a t on o t h e r  the sentence has  other uses.  But p a r t of the meaning of the  occasions concept,  i f we judge i t s meaning by i t s u s e , i s e v a l u a t i v e and as such w i l l have the c h a r a c t e r i s t i c s which Hare noted about e v a l u a t i v e  s.fe&tements.  I f we a c c e p t the v a l i d i t y of Hare's a n a l y s i s of our o r d i n a r y use of e v a l u a t i v e c o n c e p t s , t h e n we must conclude t h a t the concept "capable.e of fcnought" i s not e q u i v a l e n t t o the statement of a s e t o f c h a r a c t e r i s t i c s about humans. The q u e s t i o n now a r i s e s as t o whether or n o t t h e r e i s a s e t of c h a r a c t e r i s t i c s w h i c h are l o g i c a l l y s u f f i c i e n t f o r the a s c r i p t i o n of the concept " c a p a b l e of t h o u g h t ? "  S i n c e Hare  has shown t h a t t h e r e i s no s e t which i s e q u i v a l e n t , t h e n perhaps • t h e r e is ..some s e t of p r o p e r t i e s wh$ch are s u f f i c i e n t f o r ascription!"!.. I n t h i s case we would t h e n s e t up a s e r i e s of t e s t s f o r the p r o p e r t i e s and we would have a l o g i c a l l y s u f f i c i e n t group of t e s t s w h i c h , when a machine passed them, would f o r c e us ( l o g i c a l l y ) t o • say t h a t the machine was aapable of thought.  Gunderson seems t o  t h i n k t h a t t h e r e ls_ a s e t when he asks f o r the range of examples which would s a t i s f y the i m p l i c i t c r i t e r i a ' : ; of the concept.  But  t h e r e i s no n e c e s s i t y t h a t m e a n i n g f u l concepts have l o g i c a l l y s u f f i c i e n t criteria.}..  I argued i n s e c t i o n IY t h a t t h e r e -,>was an !  i n d e f i n i t e number of r e l a t i o n s between concepts and some of which were l o g i c a l and o t h e r s n o t .  properties,  Granted t h a t these  r e l a t i o n s are c o n v e n t i o n a l ones, ' t h i s does not show t h a t they must be l o g i c a l .  The c o n v e n t i o n c o u l d be t h a t some s e t of  c h a r a c t e r i s t i c s i s n o r m a l l y s u f f i c i e n t f o r the a p p l i c a t i o n of the concept,- but t h a t we a l l o w e x c e p t i o n a l c i r c u m s t a n c e s t o j u s t i f y the w i t h h o l d i n g of the concept.As t h e s e c i r c u m s t a n c e s can be n e i t h e r s p e c i f i e d nor f o r s e e n , i t i s e v i d e n t , as I argued i n s e c t i o n I V , t h a t the r e l a t i o n s h i p would n o t be a  s t r i c t o r l o g i c a l one. What i s t h e r e l a t i o n s h i p , t h e n , between an e v a l u a t i v e concept and t h e c h a r a c t e r i s t i c s o f s i t u a t i o n s ? i f we e v a l u a t e  Hare argues t h a t  something, t h e n we must be p r e p a r e d t o e v a l u a t e  something r e l e v a n t l y s i m i l a r , the" same way, o r e l s e o f f e r a j u s t i f i c a t i o n f o r n o t d o i n g so. And he says t h a t t h e "must" i s a l o g i c a l one i n t h e sense t h a t i f one r e f u s e d  to similarly..'  evaluate  w i t h o u t o f f e r i n g a j u s t i f i c a t i o n , t h e n one would have committed a contradiction. convention,  Thus t o f a i l t o o f f e r reasons i s t o v i o l a t e t h e  and t h i s , Hare a r g u e s , i s tea "involve ©.heseltf din a  logical contradiction, conventional  b u t t h i s i s f a r from showing t h a t t h e  r e l a t i o n i s a l o g i c a l one.  I t shows o n l y t h a t i f  one v i o l a t e s o r r e f u s e s t o p a r t i c i p a t e i n t h i s language c o n v e n t i o n ( a f t e r e n t e r i n g i t by u s i n g an e v a l u a t i v e concept) t h e n one commits a l o g i c a l f a l l a c y , but t h e c o n v e n t i o n i t s e l f c o u l d j u s t as e a s i l y be a normal one as a l o g i c a l one. as p a r t o f i t s c o n v e n t i o n , and  I f one u s e s  a concept w h i c h ,  r e q u i r e s a j u s t i f i c a t i o n , i n some cases  one s u b s e q u e n t l y r e f u s e s t o acknowledge t h e demand f o r a . j u s t -  i f i c a t i o n , t h e n one c o n t r a d i c t s o n e s e l f , even i f t h e c o n v e n t i o n i s o n l y one o f a normal r e l a t i o n between t h e concept and t h e c h a r a c t e r i s t i c s of the s i t u a t i o n . But. Hare's a n a l y s i s o f t h e a c t u a l c o n v e n t i o n a l  relation  between e v a l u a t i v e concepts and t h e v a r i o u s p r o p e r t i e s o f s i t u a t i o n s , was t h a t i f an e v a l u a t i v e concept i s used t o (say) commend a s i t u a t i o n t h e n one must a l s o commend another s i t u a t i o n o r e l s e j u s t i f y why one i s w i t h h o l d i n g  t h e commendation.  That t h e  s i t u a t i o n s a r e b o t h g i v e n and n u m e r i c a l l y d i s t i n c t i s p r o o f enough t h a t t h e r e a r e d i f f e r e n c e s between them, b u t t h e c o n v e n t i o n demands- a j u s t i f i c a t i o n f o r t h e r e l e v a n c e  of the d i f f e r e n c e s i n  •withholding  evaluation.  Furthermore t h e same c h a r a c t e r i s t i c may  "be r e l e v a n t i n one s i t u a t i o n f o r an e v a l u a t i o n and n o t i n another s i t u a t i o n f o r t h e same e v a l u a t i o n .  But a c o n v e n t i o n i n which some  d e f i n i t e s e t o f c h a r a c t e r i s t i c s a r e (say) s u f f i c i e n t f o r t h e a s c r i p t i o n o f some concept except i n e x c e p t i o n a l c i r c u m s t a n c e , i . e . , . those c i r c u m s t a n c e s i n which j u s t i f i c a t i o n can he found, i s the type of. c o n v e n t i o n I c a l l e d normal i n s e c t i o n l V . for  The c o n v e n t i o n  e v a l u a t i v e terms i s t h a t t h e terms must he r e a p p l i e d o r j u s t i —  f i c a t i o n offered f o r not reapplying  them, which means t h a t n o r m a l l y  t h e y w i l l be used i n t h e same s i t u a t i o n s b u t we a l l o w e x c e p t i o n a l l y j u s t i f i e d s i t u a t i o n s t o be. exemp't.  T h e r e f o r e I conclude on t h e  b a s i s ' o f Hare's a n a l y s i s and t f e . e d i s t i n c t i o n s I drew i n s e c t i o n IV t h a t e v a l u a t i v e terms a r e o f a normal t y p e .  Furthermore  since  the concept "capable o f t h o u g h t " i s an e v a l u a t i v e one, i t has t h i s n o n - l o g i c a l r e l a t i o n t o t h e c h a r a c t e r i s t i c s of s i t u a t i o n s ; so t h a t no s e t o f t e s t s f o r t h e c h a r a c t e r i s t i c s o f some proposed  subject  c o u l d be l o g i c a l l y s u f f i c i e n t f o r t h e a s c r i p t i o n o f t h e concept. Thus no t e s t o r s e t o f t e s t s , c o u l d  , i n p r i n c i p l e , be found which  would be l o g i c a l l y s u f f i c i e n t t o a l l o w us t o say '"Machines can think." I t may be argued t h a t i f we e l i m i n a t e t h e e v a l u a t i v e c o n t e n t from, the concept o f t h i n k i n g t h e n we s h a l l be a b l e to. f i n d a t e s t . I n t h e case where we f i n d a computer which s u c c e s s f u l l y passes t h i s t e s t , we w i l l t h e n be a b l e t o say t h a t i t t h i n k s , remembering t h a t t h i s use o f t h i n k i s n o n - e v a l u a t i v e . t o t h i s type o f c r i t i c i s m .  There a r e two r e p l i e s  I f i t i s thought t h a t t h e • a p p l i c a t i o n  of t h i s new concept t o m e c h a n i c a l d e v i c e s i s a s t e p f o r w a r d i n the problem o f a p p l y i n g m e n t a l concepts t o machines, t h e n i t i s  a mistake.  By c u t t i n g o u t t h e troublesome p a r t o f t h e concept,  one does.not t h e r e b y make g a i n s b u t r a t h e r ore o n l y saves up t h e trouble u n t i l l a t e r . is  I n t h i s r e p e c t t h e n , t o change t h e concept  o n l y t o by-pass t h e t r o u b l e u n t i l l a t e r w h i l e t h i n k i n g t h a t  one i s making g a i n s .  The second r e p l y i s -that i n c o n s i d e r i n g  problems connected w i t h t h e concept o f t h i n k i n g , t h e o n l y way t o l o c a t e t h e problem i s by c o n s i d e r i n g our p r e s e n t concept and i t s o r d i n a r y usage.  When the problem "Can machines t h i n k ? " was o r i g -  i n a l l y proposed, i t was assumed t h a t p e o p l e were wondering  whether  or n o t t h e y c o u l d say o f machines, what they say o f l o t s o f o t h e r t h i n g s ; namely t h a t t h e y c a n t h i n k .  I f t h e concept o f t h i n k i n g  was not the one o r d i n a r i l y used and meaning what we  ordinarily  mean, t h e n what o t h e r p o s s i b l e meaning c o u l d i t have had?  How  s h o u l d we have been a b l e t o f i n d any meaning f o r t h e q u e s t i o n , i f t h e words were n o t used as we u s e them i n E n g l i s h ?  Ifi n •  the  s o l u t i o n t o t h e problem, we change the meaning o f t h e q u e s t i o n ,  how  can i t be argued t h a t t h e o r i g i n a l q u e s t i o n has been  Those people who change t h e concept have n o t answered  answered.  the question  "Can machines t h i n k ? " b u t r a t h e r some o t h e r problem t h a t they have i n v e n t e d . , Gunderson seems t o have thought t h a t h i s i n i t i a l ' c r i t i c i s m s of t h e I m i t a t i o n Game c o u l d be c o u n t e r e d i f t h e i m p l i c i t of t h e concept "capaMe o f t h o u g h t " c o u l d be found. in  cri.ti i c  s m ?  criterion  He had'argued  t h a t t h e I m i t a t i o n Game was o n l y one example, and  a m u l t i t u d e o f examples were needed t o a p p l y t h e concept. But he t h o u g h t . t h a t a s e t o f t e s t s c o u l d be found w h i c h , when s a t i s f a c t o r i l y completed, would be l o g i c a l l y adequate f o r a s c r i p t i o n of t h e c o n c e p t .  However I have argued a g a i n s t t h i s , t h a t t h e r e  i s rio s e t o f t e s t s w h i c h a r e l o g i c a l l y s u f f i c i e n t .  Gunderson s 1  e r r o r seems t o have been t h a t he m i s t o o k t h e type o f concept t h a t "capable o f t h o u g h t " i s . He thought i t was a l o g i c a l type c o n c e p t , whereas I have argued t h a t i t i s anormal o r n o n - l o g i c a l t y p e .  By  type I mean type o f r e l a t i o n s h i p between t h e concept and t h e p r o p e r t i e s of s i t u a t i o n s . philosophers  By m i s t a k i n g  t h e type o f @0J3cept, some  have assumed t h a t i t had a l o g i c a l l y s u f f i c i e n t t e s t  and s e t about f i n d i n g t h e t e s t ( o r t e s t s ) .  However when we under-  stand what type o f concept "aapable o f thought'" i s , I have argued, then"we c a n see t h a t t h e s e a r c h f o r a t e s t i s i n ' p r i n c i p l e  futile.  50 •  SECTION VI CONCLUSION  I n c o n c l u s i o n , I should  l i k e to r e s t a t e some of  the  conclusions  t e n t a t i v e l y a r r i v e d at i n the p r e c e e d i n g s e c t i o n s  the paper.  I have argued i n s e c t i o n I I I t h a t t h e r e i s good '  evidence that mechanical robots sense.  are p r e d i c t a b l e i n the  important  F u r t h e r m o r e , i n s e c t i o n IV, I argued t h a t even  the i d e a of a r o b o t as j u s t a c o n c e p t u a l t h a t c e r t a i n l i n g u i s t i c problems had have not been s o l v e d . t h a t we  device,  of  using  presupposed  been s o l v e d which indeed  I n the p r o c e e d i n g ^ % i ' 6 n , I t r i e d t o show  c o u l d never i n p r i n c i p l e f i n d a t e s t which was  s u f f i c i e n t f o r the u t t e r a n c e ' " M a c h i n e X can t h i n k . " I t h i n k t h a t .these c o n c l u s i o n s  logically  Together  add up to a r a t h e r s e r i o u s  critique  of the g e n e r a l arguments advanced to show t h a t machines can  think.  However I t h i n k t h a t t h e r e are more f a r - r e a c h i n g i m p l i c a t i o n s t o be drawn f r o m the work i n t h i s paper. I n order  t o p o i n t these i m p l i c a t i o n s , l e t us r e v i e w the  sources of e r r o r s t h a t I suggested o t h e r p h i l o s o p h e r s In arguing  had made.  a g a i n s t the p o s s i b i l i t y of i m i t a t i o n , I showed t h a t •  philosophers  had made an e r r o r by f a i l i n g t o no,tice a l i n g u i s t i c  q u e s t i o n which the whole d i s c u s s i o n of i m i t a t i o n presupposed. I then.went on to i l l u s t r a t e t h e c o m p l e x i t y c o u l d e x i s t between a concept and were used.  of r e l a t i o n s t h a t  the s i t u a t i o n s i n which t h e y  F i n a l l y , I suggested t h a t those p h i l o s o p h e r s  who  were  concerned w i t h f i n d i n g a t e s t f o r t h i n k i n g had m i s t a k e n the type of concept t h a t "capable of thought" i s .  I have, i n f a c t ,  been c o n t i n u a l l y t r y i n g to show t h a t the source of e r r o r s have  a l l been  of a l i n g u i s t i c  nature.  Thus one  of the more g e n e r a l  conclusions  of t h i s paper i s t h a t f a r  more a t t e n t i o n must be g i v e n t o language and problems t h a t can a r i s e .  the v a r i o u s l i n g u i s t i c  "What i s needed i s a s y s t e m a t i c  method f o r  t a c k l i n g these problems of language once they have been shown to b e h i n d many of the more t r a d i t i o n a l problems.  But  even though  be  we  s t i l l l a c k a methodology, t h e r e i s a g r e a t need t o f o c u s more a t t e n t i o n upon our language,, i t s c o n v e n t i o n s , There i s however another way t h i s paper.  Much of my work has  form of the s t a n d a r d machines t h i n k ? " .  and  concept  types.  of l o o k i n g a t the r e s u l t s of  been i n an e f f o r t t o change the  problems a s s o c i a t e d w i t h the q u e s t i o n  "Can  For example, I t r i e d to show t h a t the problem of  t r y i n g t o f i n d a t e s t f o r t h i n k i n g i s j u s t the problem of d e t e r i n i.ng t y p e s of c o n c e p t s .  I n another s e c t i o n , I showed t h a t the problem  of c o n s t r u c t i n g a r o b o t to. I m i t a t e humans was  a t bottom, the problem  of type r e d u c t i o n , , i . e . , the problem of changing a concept of type to another w i t h o u t change of meaning.  one  I n making t h e s e changes,  I have t r i e d t o show t h a t the problems which have b o t h e r e d philosophers  i n t h i s a r e a are e s s e n t i a l l y  l i n g u i s t i c i n nature;  t h a t i s , a l l the problems can.be r e s t a t e d as l i n g u i s t i c ones. When I say t h a t I have r e s t a t e d a t r a d i t i o n a l or problem, I do not mean t h a t I have g i v e n a synonymous of the problem.  I mean e i t h e r t h a t the .standard  standard  rephrasing  problem can  be  shown t o have a r i s e n because of a l a c k of c a r e f u l l i n g u i s t i c • a n a l y s i s , or t h a t the t r a d i t i o n a l problem presupposes t h a t some l i n g u i s t i c t h e o r i e s be s u b s t a n t i a t e d .  Or even t h a t i t can .be shown t h a t  standard  problems have as t h e i r main d i f f i c u l t y a c o n f u s i o n  types'of  concepts.  I f a t r a d i t i o n a l problem i s r e l a t e d to a  in  the  • l i n g u i s t i c one  i n one  of these ways, t h e n we  a problem i n l i n g u i s t i c s .  .52 can change i t i n t o  As I s a i d , I have t r i e d to do  t h i s - r e s t a t i n g of the problems i n the a r e a of minds and The  just machines.  c o n c l u s i o n t h a t I w i s h to suggest i s t h a t i f the problems i n  t h i s - a r e a can be r e s t a t e d , t h e n t h a t i s some e v i d e n c e t h a t problems may  a l s o be r e s t a t a b l e i n t h i s way.  g r a n t t h a t t h i s paper i s not v e r y  other  I must, however,  s u b s t a n t i a l evidence to suggest  the p o s s i b l e scope of t h i s r e s t a t i n g programme.  I t i s my  belief  t h a t most t r a d i t i o n a l p h i l o s o h p i c problems can be r e s t a t e d l i n g u i s t i c ones.  Thus another more g e n e r a l  c o n c l u s i o n , of  as this  paper i s to s u g g e s t . t h e p o s s i b i l i t y of a g e n e r a l r e s t a t e m e n t of t r a d i t i o n a l p h i l o s o p h i c problems. B e s i d e s the more g e n e r a l  c o n c l u s i o n s , t h e r e are the  specific  ones i n c r i t i c i s m of the arguments,for s a y i n g t h a t machines  can  think.  the  I have argued t h a t t h e r e i s good evidence to doubt  p o s s i b i l i t y o f a i . i m i t a t i n g r o b o t and  even i f t h i s e v i d e n c e were m i s s i n g ,  the whole argument u s i n g i m i t a t i n g r o b o t s presupposes a l i n g u i s t i c d i f f i c u l t y which has not been answered. and r o b o t s , I argued, was  empty, and  The  analogy between  I t r i e d to show t h a t  l o g i c a l l y adequate t e s t of. t h i n k i n g can be f o u n d ; so these examples of machines p l a y i n g games were not but r a t h e r o n l y p e r s u a s i v e  men  no  that  conclusive  e v i d e n c e . As Gunderson s a i d :  I n the end, the steam d r i l l o u t l a s t e d John Henry as a d i g g e r of r a i l w a y t u n n e l s , but t h a t d i d not prove the machine had m u s c l e s ; i t proved t h a t muscles were not needed f o r digging railway tunnels. There have been many i n t e r e s t i n g p o i n t s -made i n the arguments f o r . t h i n k i n g machines, and making most p h i l o s o p h e r s  these p o i n t s have had  the e f f e c t of  expand t h e i r concept of what a  . • 53" machine i s . However, a s i d e f r o m t h i s m e r i t o f the arguments f o r the a f f i r m a t i v e , I have argued t h a t we a r e s t i l l s a y i n g t h a t machines cannot t h i n k .  justified i n  •  5+ !  FOOTNOTES 1 A.M.Turing,"Computing M a c h i n e r y and I n t e l l i g e n c e " , v o l . L I X , No.236 -(1950) .  Mind,  2 A.R.Anderson, ed, Minds and M a c h i n e s , Englewood C l i f f s , New J e r s e y , P r e n t i c e - H a l l , I n c , 196 f. L  3 Ibid'. , pp.h-5k Ibid.,  ppv72-97-  5 ibid.,  p.75  6 the flop flop  Another way o f p u t t i n g t h e p r e c e e d i n g remarks ' o n l y i f c o n d i t i o n i n T i s i n s t a t e A i f and 36 i s on", can be cashed i n t o a f i n i t e l i s t ; 1 i s e i t h e r on o r o f f , f l i p f l o p 2 i s e i t h e r 11  i s t o say t h a t only i f f l i p such a s , f l i p on o r o f f , e t c .  7 A.R.Anderson, op. c i t . , pp.73-7 +1  8 A.M.Turing, l o c . c i t . 9 A.Church, I n t r o d u c t i o n t o M a t h e m a t i c a l L o g i c , P r i n c e t o n , P r i n c e t o n U n i v e r s i t y P r e s s , 1956. 10 M.Davis, C o m p u t a b i l i t y and U n s o l v a b i l i t y , M c G r a w - H i l l Book Company, I n c , 1 9 5 8 . 11  New Y o r k ,  A.R.Anderson, op. c i t . , p.7*+-  12 I b i d . , • p.81 . 13 I b i d . , P- 771^f I b i d . , P- 81 . 15 I b i d . , P- 8 2 . 16 I b i d . , P- ^ 3 . 17 I b i d . , P- 7718 I b i d . , P- 15. 19 M.Davis, op. c i t . , Chapter 1. 20 A.R.Anderson, op. c i t . , pp. K3-59. L  21  I b i d . , pp  22 I b i d .  pp.31-^2.  23 I b i d . ,  p.3^  2h C . T a y l o r , The E x p l a n a t i o n o f Behavior„ London, R o u t l e d g e  555 and Kegan P a u l ,  \96h, pp.82-87.  25 R.M.-Hare, The Language o f M o r a l s , P r e s s , 1961, pp.9^-110-  Oxford, a t the Clarendon  26 I b i d . , pp.9^-'9527 M . S c r i v e n , "The L o g i c o f C r i t e r i o n " , The J o u r n a l o f P h i l o s o p h y , v o l . L V I , No.22, p.857. 28 S.C.Coval, "Can Humans ' F e e l ' ? " ,  unpublished.  29 A.R.Anderson, op. c i t . 30 I b i d . , p.70. 31 S.Hook, ed., Dimensions o f Mind,- New York,. New York U n i v e r s i t y P r e s s , 1960, p.124-. 32 I s u s p e c t t h a t S c r i v e n a l s o sees t h i s . Compare h i s a r t i c l e i n The J o u r n a l o f P h i l o s o p h y , op. c i t . , p.868. I u s e h i s argument o n l y as an example o f t h e i m p l i e d l o g i c a l t r a p argument with testing. 33 R.M.Hare, op. c i t . , pp.79-933h I b i d . , p.85. 35 A.R.Anderson, o p . c i t . , p.71•  36 Loc. c i t .  56 BIBLIOGRAPHY Books Anderson,A.R., ed. Minds and Machines. Englewood C l i f f s , New J e r s e y , P r e n t i c e - H a l l , I n c . , 1 96+. (Contemporary P e r s p e c t i v e s i n P h i l o s o p h y S e r i e s , .eds. J o e l F e i n b e r g and W.C. Salmon, l  vol.1).  C h a p p e l l , V . C . , ed. The P h i l o s o p h y o f Mind. Englewood New J e r s e y , P r e n t i c e - H a l l , I n c . , 1962.  Cliffs,  D a v i s , M. C o m p u t a b i l i t y and U n s o l v a b i l i t y . New Y o r k , McGrawH i l l Book Company, Inc.,,1958. Hare,R.M. The Language o f M o r a l s . O x f o r d , at' the . P r e s s , 1961.  Clarendon'"  T a y l o r , C . The E x p l a n a t i o n o f B e h a v i o r . London, Routledge and Kegan P a u l , 196^. ( I n t e r n a t i o n a l L i b r a r y o f P h i l o s o p h y and S c i e n t i f i c Method, ed.A.J.Ayer). . W i t t g e n s t e i n , L . P h i l o s o p h i c a l I n v e s t i g a t i o n s . Trans.G.E.M. Anscombe. O x f o r d , B a s i l B l a c k w e l l , 1963*  Articles I • TT  c  o  A l b r i t t o n , R . "On W i t t g e n s t e i n s USe o f the Term ' " C r i t e r i o n * ". The J o u r n a l o f P h i l o s o p h y , v o l . L V I , No.22, pp.8>+5-856. Scriven,M.  "The.L6gic o f C r i t e r i o n " . The J o u r n a l o f P h i l o s o p h y ,  v o l . L V I , No.22, pp.857-865.  Wisdom,J.O. '"A New Model f o r the• Mind-Body R e l a t i o n s h i p " . The B r i t i s h J o u r n a l f o r the P h i l o s o p h y o f S c i e n c e , v o l . 2  No.8  (1951-52) pp.295-301.  Wisdom,J.O. "The. H y p o t h e s i s o f C y b e r n e t i c s " . The B r i t i s h J o u r n a l fo'r the P h i l o s o p h y o f S c i e n c e , v o l . 2 No. 5 (1951-52), pp. 1-2.M.  1  

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