C A U S A L I T Y I N S C I E N C E by C o r n e l i u s Kampe B . S c , U n i v e r s i t y of B r i t i s h Columbia, 196k-A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR TH E DEGREE OF M.A. i n the Department of PHILOSOPHY We accept t h i s t h e s i s as conforming to the re q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1966 i i In p resen t i ng t h i s t h e s i s in p a r t i a l f u l f i l m e n t o f the requirements f o r an advanced degree at the U n i v e r s i t y o f B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r re fe rence and s tudy . I f u r t h e r agree tha t p e r -m iss ion f o r e x t e n s i v e copy ing o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head o f my Department o r by h i s r e p r e s e n t a t i v e s . It i s understood that copy ing o r p u b l i -c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l ga in s h a l l not be a l lowed w i thout my w r i t t e n p e r m i s s i o n . , Department o f PHILOSOPHY The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada Date A p r i l 1?, 1966. i ABSTRACT The concept of c a u s a l i t y understood as l a w - l i k e r e g u l a r i t y , pervades science from the a p p l i e d or p r a c t i c a l to the t h e o r e t i c a l s c i e n c e s , from i t s e a r l y days to the present. But, workers l i k e R u s s e l l and Hanson have c o r r e c t l y observed th a t e x p l i c i t mention of causes tends to disappear i n advanced and s t r i c t l y t h e o r e t i c a l sciences l i k e p h ysics and g r a v i t a t i o n a l astronomy. The concept of p r e d i c t i o n or e x p l a n a t i o n i n accordance w i t h general laws, r e p l a c e s the e a r l i e r , c a u s a l concepts. The l i m i t i n g form of t h i s process i s a science where Hempel-Oppenheim e x p l a n a t i o n i s achieved. Here the c o n t r o v e r s i a l symmetry between explanations and p r e d i c t i o n s , as i m p l i e d by Hempel 1s view, does e x i s t even i f i t does not i n a more p r i m i t i v e s c i e n t i f i c work. Only quantum mechanics casts doubts on t h i s t h e s i s , but co n t r a r y to views advanced by Hanson, the symmetry t h e s i s can be extended i n t o t h a t d i s c i p l i n e . i i i ACKNOWLEDGEMENT A f t e r r e c e i v i n g my Bachelor of Science degree, I went to see Pr o f e s s o r Barnett Savery, the head of the department of philosophy. I was very f o r t u n a t e to f i n d a r e a l philosopher whose guidance i n a genuine p h i l o s o p h i c a l s p i r i t gave me encouragement. In h i s department under the guidance of Dr. Ian Hacking, I have completed the work I present here, on the question of c a u s a l i t y i n sc i e n c e . I t was a pleasure f o r me to be introduced by Dr. Hacking i n t o independent p h i l o s o p h i c a l t h i n k i n g . i v TABLE OF CONTENTS I ON CAUSES IN PRACTICAL SCIENCE page 1 I I ' "WHY QUESTIONS" CORRESPOND TO CAUSES AND "HOW QUESTIONS" CORRESPOND TO LAW-LIKE EXPLANATIONS page 10 I I I CAUSES IN C. G. HEMPEL1S EXPLANATIONS page 16 IV - EXPLANATIONS AND PREDICTIONS IN QUANTUM MECHANICS page 20 CONCLUSION ' • page 33 NOTES page 3*+ BIBLIOGRAPHY page 36 .1 . ON CAUSES IN PRACTICAL SCIENCE In g i v i n g the cause f o r a p a r t i c u l a r occurrence both i n everyday a f f a i r s as. w e l l as i n p r a c t i c a l s c i e n c e , we are making a statement which may be put i n the form: 'whenever X then Y 1. The i n i t i a l c o n d i t i o n X has to be a s u f f i c i e n t c o n d i -t i o n f o r the occurrence of Y. One may d i s t i n g u i s h between two i n t e r p r e t a t i o n s ( i ) X determines Y i n the sense of having the power to b r i n g about Y. (John Locke spoke of the idea of cause as the idea of o p e r a t i o n w i t h something operating which we. c a l l a cause. )^~~^ ( i i ) X and Y are r e l a t e d i n the Humean sense of constant c o n j u n c t i o n . . In a Humean account, any t a l k about Y's occurrence i s incomplete f o r we must determine how X and Y r e l a t e ; how prece-dent occurrences r e l a t e w i t h consequent occurrences according to a law. This i s e x a c t l y what a more, advanced science does. On the other, hand causes 'having power' i s a p r e - c r i t i c a l manner of speaking f o r the 'power' i s a p o s t u l a t e d o c c u l t q u a l i t y . An i n q u i r y i n t o understanding the world which i s r e s t r i c t e d to causes^iri incomplete i n that the form or the func-t i o n a l r e l a t i o n s h i p between antecedent and consequent occurrences i s omited. I w i l l now t u r n to an i n v e s t i g a t i o n of causes i n p r a c t i c a l science to i l l u s t r a t e how causes are used and to i l l u m i n a t e t h i s incomplete or fragmentary d e s c r i p t i o n of nature. (2) In 1910, Bertrand R u s s e l l v ' sha r p l y c r i t i c i z e d the n o t i o n of c a u s a l i t y n o t i n g i n p a r t i c u l a r t h a t causes are excluded from advanced s c i e n c e . However, the word 'cause' continues to be used i n s p i t e of i t s omission from t h e o r e t i c a l , science. The medical doctor w i l l say, " D e p r i v a t i o n of "ascorbic a c i d causes..4 2 s c u r v y " ^ according to t h i s usage i t seems that the cause i s the l a c k of some e s s e n t i a l i n g r e d i e n t . The consequent c o n d i t i o n , of good or had h e a l t h i s r e l a t e d to a set of antecedent co n d i -t i o n s i n a r e l a t i o n s h i p of the type l (1) i f A, B and C then G (good h e a l t h ) (2) i f not A, or not B or not C, then not G (poor h e a l t h ) . U s u a l l y i n t a l k i n g about the cause of some ef f e c t , , we t a l k about the presence or occurrence of some event, or p o s s i b l y body which may act as an agent, i n the prod u c t i o n of the e f f e c t ; t h a t i s , we t a l k i n terms of type 1 above. However, i n p r a c t i c a l s c i e n c e , the no t i o n ' o f cause i s not r e s t r i c t e d to ( 1 ) . This seems to imply that the n o t i o n of agency i s not e s s e n t i a l to the concept of cause i n t h i s usage. I f someone s a i d that cause always i n v o l v e s agency, even i n the case of ' l a c k s ' , he might counter my c l a i m by saying t h a t , '"To say tha t l a c k of A causes B i s to say tha t there i s . an agent C tha t causes B but would not cause B i n the presence of A." I t i s c l e a r l y the case that 'cause' i s used i n sentences of the form 'lack of A causes B'. What i s i n que s t i o n i s : i f such an agent can be found, what i s the s t a t u s of the agent? Can we i d e n t i f y t h i s agent and observe i n an experimental s i t u - , a t i o n whether or not the agent operates i n the presence or absence of A? I f not, i s the agent merely a p o s t u l a t i o n having no inde-pendent grounds f o r i t s existence other than s a t i s f y i n g the need to have an agent always a c t i n g as the cause? The problem becomes e a s i e r by c o n s i d e r i n g the example, " D e p r i v a t i o n of a s c o r b i c a c i d causes scurvy". Modern medical knowledge does not r e v e a l the presence of an agent which causes 3 ; scurvy i n cases where a s c o r b i c a c i d i s l a c k i n g . Such an agent would have only p o s t u l a t i o n a l s t a t u s . Let us t r y to b u i l d as strong a case f o r the 'agency theory' as p o s s i b l e . On being t o l d t h a t t h e l a c k of n u t r i t i o u s food causes d i s e a s e s , the advocates of agent as cause would, p o i n t out t h a t ' i n the 'absence of n u t r i t i o u s food there are agents, b a c t e r i a , which cause i l l h e a l t h ' , ( i n f e c t i o u s b a c t e r i a a t t a c k the . weakened organism). B a c t e r i a can be i d e n t i f i e d more s p e c i f i c a l l y on independent grounds as causes of i l l n e s s e s . The presence or absence of p a r t i c u l a r b a c t e r i a i s r e l a t e d to the presence or absence of some p a r t i c u l a r i l l n e s s . In u s i n g language, we c a l l both ' b a c t e r i a ' and 'lack of n u t r i t i o u s food' causes, choosing one i n preference to the other depending on which i s more a c c e s s i b l e to m a n i p u l a t i o n i n a p a r t i c u l a r experimental s i t u a t i o n , or choosing one i n preference to the other depending on which l e v e l microscopic or macroscopic we wish to make our a n a l y s i s . To m a i n t a i n or even to understand the t h e s i s that 'cause must be an agent', i t i s important f o r us to n o t e , i n p a r t i -c u l a r the s t a t u s of an agent as cause. That i s , i l l h e a l t h can be given a number of causes among them, a cause which i s recognized as an agent.. There are no grounds f o r the statement t h a t only agents are causes where the causes of some event are spoken of as l a c k s , agents or s t a t e s . Turning to our previous example, ' b a c t e r i a , cause c a r i e s ' , we may ask, 'how do b a c t e r i a cause c a r i e s ? ' To ask f o r what purpose (why) b a c t e r i a cause c a r i e s i s simply t e l e o l o g i c a l . Such questions are excluded from s c i e n c e . A • complete answer to the 'how' q u e s t i o n w i l l i n v o l v e us i n the metabolism of b a c t e r i a and chemistry of b a c t e r i a l a c t i o n , and the chemistry of the body. No agent here. Then j u s t as 'cause 1 i n the sense of l a c k was found to be incomplete, so a l s o 'cause' as agent i s incomplete i n so f a r as f u r t h e r a n a l y s i s does not r e s t content w i t h bac.teria as agents. In o r d i n a r y d i s c o u r s e , we may ask "Why d i d Mr. X get up and leave the t a b l e before dinner was f i n i s h e d " . Two d i s t i n c t types of answers are o f t e n given. In terms of purpose, Mr. X's a c t i o n could be described as r e s u l t i n g from h i s d e s i r e to hear the news. Then h i s purpose i n l e a v i n g the t a b l e was to t u r n on the r a d i o . A l t e r n a t i v e l y , the same occurrence may be described i n terms of h a b i t and n e u r a l p r e f e r e n t i a l pathways. "Mr. X l e f t the t a b l e because the mantle c l o c k 'struck s i x ' . " The s t r i k i n g of the c l o c k i n i t i a t e d h i s response to go to the r a d i o and ' f l i c k ' on the s w i t c h which he has been doing f o r the past ten years. I n the one case, the a c t i o n r e s u l t e d from the motive to achieve a c e r t a i n end. The other answer i s c a u s a l : a p a r t i c u l a r e x t e r n a l stimulus caused Mr. X. to get up. G i l b e r t Ryle objects to motives being causes saying as f o l l o w s : " to e x p l a i n an a c t i o n as done from a c e r t a i n motive i s not to c o r r e l a t e i t w i t h an o c c u l t cause, but to subsume i t (h) under a p r o p e n s i t y or behaviour t r e n d . " v ' The o c c u l t cause to which Ryle r e f e r s i s the f a c u l t y of v o l i t i o n s which he vehemently r e j e c t s , proposing f o u r types of d i f f i c u l t i e s which v o l i t i o n i s t s have to surmount. He concludes: "Motives are not happenings and are, t h e r e f o r e , not of the r i g h t type to be c a u s e s . " w y The c a u s a l e x p l a n a t i o n (the one which e x p l i c i t l y mentions a cause), i l l u s t r a t e a p r i m i t i v e type of s c i e n t i f i c e x p l a n a t i o n . . 5 The event 'mantel c l o c k s t r i k i n g s i x ' i s r e l a t e d f o r t h i s p a r t i c u l a r man to the response ' f l i c k i n g the r a d i o switch' according to the r e l a t i o n s h i p whenever X then Y. A more complete e x p l a n a t i o n f o r t h i s p a r t i c u l a r occurrence as might he made by a p h y s i o l o g i s t would be i n terms 'of p r e f e r e n t i a l n e u r a l pathways r e l a t i n g stimulus to response without e x p l i c i t mention of cause. States are sa i d to be causes i n sentences of the f o l l o w i n g form: 'What caused him to give up the Church?' d i s i l l u s i o n w i t h the Pope's stand on c o n t r a c e p t i o n ' . To say that a man i s d i s i l l u s i o n e d i s to make a d i s p o s i t i o n a l s t a t e -ment about him i n the Rylean sense. "To possess a d i s p o s i -t i o n a l p r o p e r t y " , according to Ryl e , " i s not to be i n a p a r t i -c u l a r s t a t e , or to undergo a p a r t i c u l a r change; i t i s to be . bound or l i a b l e to be i n a p a r t i c u l a r s t a t e , or to undergo a p a r t i c u l a r change, when a p a r t i c u l a r c o n d i t i o n i s r e a l i z e d " . ^ \ I f A i s d i s i l l u s i o n e d ( d i s p o s i t i o n a l ) , then he i s bound or l i k e l y to do so and so i n such and such circumstances. This i s a l l t h a t i s meant by saying t h a t d i s i l l u s i o n or love are s t a t e s . According to G i l b e r t Ryle's a n a l y s i s , the general f a c t t h a t a person i s disposed to act i n such and such circum-stances does not by i t s e l f account f o r h i s doing a p a r t i c u l a r t h i n g at a p a r t i c u l a r moment, any more than the f a c t t h a t the gl a s s was b r i t t l e accounts f o r i t s f r a c t u r e at 10 p.m. as the impact of the stone at 10 p.m. caused the g l a s s to break. We do, however, use the word'state' i n other contexts than the p r e v i o u s l y considered d i s p o s i t i o n a l manner. In p h y s i c s , we t a l k about energy s t a t e s of atoms. "Bohr suggested t h a t , 6 inasmuch as Planck had already shown tha t the c l a s s i c a l theory d i d not adequately d e s c r i b e the i n t e r a c t i o n between r a d i a t i o n and matter, i t was reasonable to assume that there were c e r t a i n s t a t i o n a r y s t a t e s i n which an atom d i d not r a d i a t e at a l l . Each of these s t a t e s i s c h a r a c t e r i z e d by a d e f i n i t e energy. They are separated by f i n i t e energy. They are separated by f i n i t e energy d i f f e r e n c e s . Emission and a b s o r p t i o n of r a d i a t i o n take place when the atom makes a t r a n s i t i o n from one s t a t e to (7) another". In what sense can the higher energy s t a t e be s a i d to cause the emission of r a d i a t i o n ? By higher energy s t a t e we mean a ' s t a t e ' above the normal s t a t e of lowest energy. To t a l k about atomic s t a t e s i s to_ t a l k i n the hypo-t h e t i c a l language — i f . . . . . t h e n . The s t a t e of an atom cannot be i d e n t i f i e d apart from the a b s o r p t i o n or emission of photons. I f we are t r e a t i n g the emission or a b s o r p t i o n as e f f e c t s , then the cause cannot be i d e n t i f i e d on independent grounds. F u r t h e r -more, although an atom which i s s a i d to be i n a p a r t i c u l a r . e x c i t e d s t a t e ( i . e . the f i r s t e x c i t e d s t a t e above ground s t a t e ) , e v e n t u a l l y decays w i t h the emission of a photon w i t h a unique energy a s s o c i a t e d w i t h that t r a n s i t i o n , the time at which t h i s t r a n s i t i o n occurs i s indeterminate. Only the h a l f l i f e f o r some p a r t i c u l a r . s t a t e i s knowable. C l a s s i c a l l y , i f A i s i n a s t a t e S, then something i s s t i l l r e q u i r e d to i n i t i a t e an a c t i o n ; the s t a t e p r e d i c t s the type of response. I t does not i n i t i a t e the occurrence of the e f f e c t . To say, then, t h a t the s t a t e of an atom i s the cause of the emission of some p a r t i c u l a r photon i s to make two ser i o u s e r r o r s . F i r s t l y , i t i s to introduce an o c c u l t cause. , 7 Secondly, i t i s to say that the cause of some e f f e c t can con-t i n u e to e x i s t f o r some u n s p e c i f i e d time without producing the e f f e c t . I t i s to say something s i m i l a r to 'the cause of the breaking of the g l a s s was i t s b r i t t l e n e s s ' . There i s a f u r t h e r common use of 'cause' as s t a t e . We o f t e n say: 'the warm weather, (a s t a t e ) , caused the snow to m e l t . 1 This i s equi v a l e n t to saying, 'The snow melted because of the warm weather'. We o f t e n a l s o reverse the order and say, 'I know i t i s warm because' the snow i s m e l t i n g ' . The f a c t i s , . to say ' i t i s warm', i s to say the snow i s m e l t i n g , my hands are not f r e e z i n g , e t c . Warm and c o l d , of course, are words whose meaning v a r i e s according to context. In summer, 65 degree's Fahrenheit i s c o l d ; i n w i n t e r , i t i s warm. But as we o r d i n a r i l y use these words, we assume the p e r t i n e n t context. 'On waking one winter day I look out the window and see the snow m e l t i n g . I exclaim, I t ' s warm outside I ' In the r e l e v a n t context, to say ' i t i s warm' i s to. imply t h a t 'the snow i s m e l t i n g ' . The- q u e s t i o n now remains — Do we mean anything more than the above when -we say tha t the warm weather i s causing the snow to melt. The two p o s s i b i l i t i e s are: I. warm weather i s a causal agent i i . warm weather e x p l a i n s the melt i n g of the snow i n the same sense th a t a c i d s i n the mouth e x p l a i n t o o t h decay i n terms of the concepts of physics and chemistry. We can r e j e c t i . o u t r i g h t as a misuse of 'agent 1, i i . c a r r i e s the f o r c e of a law ex p l a n a t i o n . 8 As we have seen from the previous a n a l y s i s , the question 'What caused i t ? ' , i s o f t e n answered hy an e x p l a n a t i o n of 'how i t occurred'. This appears to be the most complete answer i n so f a r as such explanations take i n t o account a l l f e a t u r e s which appear e s s e n t i a l f o r i t s production. Often, these explanations are given i n terms of laws or r u l e s . But, there i s something strange about'saying t h a t r u l e s cause e f f e c t s (events). Rules are made by men. They are spoken or w r i t t e n . They are not i n the world, f o r they have no temporal or s p a t i a l l o c a t i o n . N e v ertheless, asking f o r a cause turns out very o f t e n to be asking f o r an e x p l a n a t i o n . N. R. Hanson goes as f a r as to say t h a t , "The primary reason f o r r e f e r r i n g to the . cause of X i s to e x p l a i n X. There are as many causes of X as explanations of X." ; Let us suppose that there are n p o s s i b l e explanations of a car a c c i d e n t . Further i n v e s t i g a t i o n r e v e a l s to the magis-t r a t e t h a t according to ' r a t i o n a l ' c o n s i d e r a t i o n s , two of them are u n s a t i s f a c t o r y . Now, having a l l the p e r t i n e n t 'facts.'' before him, he advances a new ex p l a n a t i o n f o r the a c c i d e n t . Are we then to say tha t f i r s t there were n causes, then there were n-2 causes, and now there are n-1 causes f o r the accident?. I t i s c l e a r l y the case that 'causes' and E x p l a n a t i o n s ' do not have a one-to-one correspondence. I b e l i e v e t h a t we w i l l a l l r e a d i l y admit t h a t the explanations f o r the occurrence of some event may be many, may d i f f e r from day to day and may be c o r r e c t or not c o r r e c t . However, causes cannot be t r e a t e d i n t h i s way. The causes f o r yesterday's accident are not d i f f e r e n t today from yesterday. N e i t h e r are causes s a i d to be c o r r e c t . 9 or i n c o r r e c t , although, the cause of some event may or may not be c o r r e c t l y i n d e n t i f i e d . • • What does Hanson mean by 'explain'? We o f t e n ask, 'Explain why ?' and 'E x p l a i n how ?' To ' e x p l a i n why1 i n i t s primary sense Is to give purposes, motives and reasons. To ' e x p l a i n how' i s to give d e s c r i p t i o n s , o r i g i n s or to invoke some theory of o p e r a t i o n or some model. Suppose someone were to say that there i s a one-to-one correspondence between the c o r r e c t explanations and the causes f o r some p a r t i c u l a r , occurrence. To r e f u t e t h i s : a s s e r t -a t i o n , i t i s s u f f i c i e n t to p o i n t out tha t 'why' explanations are made in-terms which, as we have seen, are not causes. 10 "WHY QUESTIONS" CORRESPOND TO CAUSES ' AND "HOW QUESTIONS" CORRESPOND TO LAW-, LIKE EXPLANATIONS Even though questions i n science may be formulated i n terms of 'why', yet these questions are never answered by stating:: purposes or t e l e o l o g i c a l reasons. The answers which science gives to 'why' questions are never i n terms of purposes or reasons but i n terms of how X v a r i e s w i t h Y, how the atmosphere s c a t t e r s white l i g h t , how the p l a n t synthesizes sugars, e t c . I b e l i e v e 'why' remains i n use sin c e p r e - s c i e n t i f i c t h i n k i n g was o f t e n t e l e o l o g i c a l and i n v o l v e d agents as causes w i t h power to b r i n g about t h e i r e f f e c t s . So -in former times 'why questions' were a p p r o p r i a t e . The word has remained w i t h us although we no longer use i t i n i t s t e l e o l o g i c a l sense i n science. I t i s important f o r us to be c l e a r about (the c o n t r a s t between) the 'how' and 'why' type questions because the change from 'why' to 'how1 corresponds to a change from a.system of causes conceived as what Locke c a l l s 'powers' to a system of l a w - l i k e statements about the world. Where causes are thought .to have the power to b r i n g about t h e i r e f f e c t s 'why' questions are ap p r o p r i a t e . 'Why d i d P o c c u r ? 1 Answer: X had the power to produce P and X was present i . e . X caused P. On the other hand the question: 1 'How d i d P occur?' i s ' n o t s a t i s f a c t o r i l y answered by saying 'X caused P'. We can ask how d i d X cause P?' or, 'what i s the exact r e l a t i o n s h i p between X and P? 1 What i s being asked f o r i s the law r e l a t i n g to X and P. We can even begin to date the change between the two conceptions. Ernst Schumacher w r i t i n g on G a l i l e o ' s method f o r 11 conducting i n v e s t i g a t i o n s i n n a t u r a l science says a s - f o l l o w s : " G a l i l e o replaced the u n f r u i t f u l s p e c u l a t i o n s of 'why?' by an a n a l y s i s of 'how?' He recommended that the i n v e s t i g a t i o n of nature should no longer continue to i n q u i r e i n t o i t s substance but r a t h e r i n t o i t s f u n c t i o n ; the i n v e s t i g a t i o n s should concern themselves not w i t h the essences but w i t h the a t t r i b u t e s of nature. G a l i l e o c h a r a c t e r i z e d t h i s new method of viewing nature i n the t h i r d l e t t e r on sunspots to the (9) mayor of Augsburg, Markus Welser, dated 1613." I quote i n p a r t from t h i s l e t t e r : "For i n our s p e c u l a t i n g we e i t h e r seek to penetrate the true arid and i n t e r n a l ' e s s e n c e of n a t u r a l substances, or content'Ourselves w i t h a knowledge of some of t h e i r p r o p e r t i e s . The former I h o l d to be as impossible an undertaking w i t h regard to the .' c l o s e s t elemental substances, as w i t h more remote c e l e s t i a l things...' I know no more about the true essence of e a r t h or f i r e than about those of the moon or s u n . . . " ^ ^ . P. H. Nowell-Smith* w r i t i n g on c a u s a l i t y says much the same t h i n g : "The t r a n s i t i o n from explanations i n terms of e f f i c i e n t causes .to explanations i n terms of Law was l a r g e l y the work of G a l i l e o . . . I n the f i r s t place he undermined A r i s t o t e l i a n e xplanations of why things move as they do... This d i s c r e d i t e d the whole e n t e r p r i s e of e x p l a i n i n g phenomena i n terms of f i n a l causes and thereby opened the way f o r other types of explan-a t i o n . Secondly, the s u b s t i t u t i o n of exact d e s c r i p t i o n f o r e x p l a n a t i o n (or, as i t i s sometimes put, -of the question 'How?' f o r the question 'Why?') l e d e v e n t u a l l y to a conception 12 of science i n which a l l e x p l a n a t i o n j u s t i s description-. . A phenomena i s now s a i d to be explained when the r e g u l a r i t y which i t e x e m p l i f i e s i s able to be i n c o r p o r a t e d i n t o a (11) system of laws...." v ' The a n a l y s i s of 'how' and 'why' questions serves as an e x p l i c a t i o n of the Schumacher and Nowell-Smith views which are of paramount importance f o r understanding the r e l a t i o n s h i p between the two world accounts: ( i ) i n terms of causes, and ( i i ) i n terms of d e s c r i p t i o n s as l a w - l i k e accounts of the world. I wish to make t h i s s e p a r a t i o n of 'why?1 and 'how?' which estab-l i s h e s the method of science c l e a r . Let i t be understood, that the f o l l o w i n g d i s c u s s i o n of 'why?' and 'how?1 does not attempt to be a thorough language a n a l y s i s , but i t i s r a t h e r r e s t r i c t e d to c l a r i f y i n g the concepts of purposes and reasons as a s s o c i a t e d w i t h 'why?1 and 'how?' questions i n so f a r as they have bearing on my'thesis. Anatol Rapoport notes the c o n t r a s t i n the tasks of philosophy and t h a t of s c i e n c e . "Science confines i t s e l f to d e s c r i p t i o n s of how t h i n g s happen and does not pursue the more fundamental question of why t h i n g s happen as they do. I t does remain f o r (12) philosophy to i n v e s t i g a t e t h i s more fundamental q u e s t i o n . " . Whereas, science w i l l answer 'why* questions, i t w i l l do so by s t a t i n g t h a t some p a r t i c u l a r occurrence f a l l s under the form of a general law. In answer to. the q u e s t i o n , 'why d i d the apple f a l l ? ' science w i l l , say, 'because a l l bodies are a t t r a c t e d towards each other i n accordance w i t h the u n i v e r s a l law of g r a v i t a t i o n ' . To the question 'what caused the apple to f a l l ? ' the same answer w i l l be given. E s s e n t i a l l y , science answers only one question and'tha 1 3 i s the 'how' quest i o n , namely, 'How do bodies f a l l ? ' They f a l l i n accordance w i t h the u n i v e r s a l law of g r a v i t a t i o n . I wish to d i s t i n g u i s h between two uses of 'why', l a . Why d i d Brutus stab Caesar? b. Why d i d P r e s i d e n t John Kennedy de c l a r e a war on poverty? Here the answer i s given i n terms of the purposes or motives which the subject i s s a i d to have had. a. His purpose was to conserve the Roman Republic from the imagined usurper Caesar. b. His purpose or motive was to b u i l d a strong and j u s t America. The second use of 'why' i s i l l u s t r a t e d by the f o l l o w i n g two sentences: I l a . Why d i d the wine b o t t l e which one of Caesar^'s s o l d i e r s threw i n t o the Tiber at the l e f t bank end up on the < other side of the r i v e r ? b. Why i s the sky blue? • We note, f i r s t of a l l , t h a t the sentences l a . and b. change t h e i r meaning when 'how' i s s u b s t i t u t e d f o r 'why', or 'how d i d i t occur t h a t ' i s s u b s t i t u t e d f o r 'why'. That i s - "How'did Brutus stab Caesar?" or "'How; d i d i t occur that'' Brutus stabbed Caesar?" asks f o r the h i s t o r i c a l r e c r e a t i o n of the p h y s i c a l event, or i t asks f o r the preceding events which l e d to the stabbing. S i m i l a r l y l b . w i t h the s u b s t i t u t i o n of 'how' f o r 'why' now asks f o r an observer's account f o r what went on at that h i s t o r i c a l o ccasion. . ' I w i l l r e f e r to the use of 'why' which does not a l l o w a 'how' s u b s t i t u t i o n as the unique use. There i s a l s o a unique Ik use, i n the same sense, f o r 'how1, as we s h a l l see, where 'how' cannot be replaced by 'why'. Namely, the q u e s t i o n , "How does that mechanism work?", i s answered by e x p l a i n i n g how i t s v a r i o u s p a r t s i n t e r a c t . The qu e s t i o n , "Why does the mechanism work ( l i k e t h a t ) ? " , i s answered not 'how' the mechanism works ( s i n c e the i m p l i c i t ' l i k e t h a t ' a l r e a d y i m p l i e s knowledge of 'how'), but r a t h e r , "What d i d the maker of the machine or mechanism have i n mind f o r i t ? " P o s s i b l y , we can make t h i s even c l e a r e r . ; J Consider the sentence, "How f a r i s the moon?" O p e r a t i o n a l l y , what i s being asked here i s , "How many measuring s t i c k s have to be l a i d out to coyer the d i s t a n c e separating the moon and the earth?", or f o r some more advanced v a r i a n t of t h i s . I t i s c l e a r l y n o n s e n s i c a l to rephrase the que s t i o n to "'Why1 f a r i s the moon?" In I l a . s u b s t i t u t i n g 'how1 or 'how does i t occur t h a t ' f o r 'why' does not change the meaning of that sentence. I n l i b . "Why i s the sky blue?" or "How does i t - occur t h a t the sky i s blue?" are sentences which are not commonly used i n the E n g l i s h language. One i s not e x a c t l y c l e a r what i s being asked. The f o r c e of l i b . appears to be: "In v i r t u e of what process i s the sky blue?" Let us assume that we are asking a s c i e n t i f i c a l l y o r i e n t a t e d person why the sky i s blue. Then we would presumably be t o l d something l i k e : The - l i g h t from the sun, white l i g h t , i s a mixture of the v a r i o u s s p e c t r a l c o l o u r s , but the atmosphere s c a t t e r s the sho r t e r wave l e n g t h (blue) more than the longer wave le n g t h s . Consequently, we observe the sky as blue. Now, i f we consider t h i s answer apart from.the question which we asked, we. see i t as an e x p l a n a t i o n f o r the blueness of the sky. In p a r t i c -u l a r , we see that the e x p l a n a t i o n d e s c r i b e s how white l i g h t 15 o r i g i n a t i n g ' i n the sun i s s c a t t e r e d 'by the earth's atmosphere. We are not t o l d why any of t h i s happens. That i s , . t h e e x p l a n a t i o n i s an answer'to a 'how' q u e s t i o n ; although the q u e s t i o n which asks "How does i t occur t h a t the sky i s blue?" i s not commonly used. The 'why' question i s a remnant of a t e l e o l o g i c a l p r e - s c i e n t i f i c conception of the world. To conclude: The unique, use of 'why' which does not a l l o w an a l t e r n a t i v e 'how' question to do i t s work i s i n terms of • purpose, motives, reasons and p o s s i b l y f i n a l causes, i n v o l v i n g agents. S i m i l a r l y , 'how1 has.a proper use which.does not overlap w i t h the.'why' question. In u s i n g language, we o f t e n ask 'why?' but do not d i s t i n g u i s h t h i s 'why' question from the same question w i t h 'how' s u b s t i t u t e d f o r 'why'. Where 'why' questions are asked i h science the answer i s always i n terms of 'how', whether or not, as the i l l u s t r a t i o n which we have considered shows a d i r e c t 'how' s u b s t i t u t i o n i s i n common acceptable use. 16 CAUSES IN C. G. HEMPEL'S EXPLANATIONS C a r l Hempel and Paul Oppenheim w r i t i n g about explanations d i v i d e the b a s i c p a t t e r n of s c i e n t i f i c e xplanations i n t o two c o n s t i t u e n t statements, explanandum and explanans. . The explanandum de s c r i b e s the" phenomenon to be explained and the explanans accounts f o r the phenomenon. "The explanans f a l l s i n t o two c l a s s e s , one of these contains the sentences C^, Cg.-.C^ which s t a t e antecedent c o n d i t i o n s (l ^ V and a^ , a ^ . i.a.^ which represents general laws." -J/ Four l o g i c a l c o n d i t i o n s of adequacy are y given as f o l l o w s : (1) The explanandum must be l o g i c a l l y deducible from the i n f o r m a t i o n contained i n the explanans. . (2) The explanans must c o n t a i n general laws, and those must a c t u a l l y be r e q u i r e d f o r the d e r i v a t i o n of the explanandum. (3) The explanans must have e m p i r i c a l content i . e . i t must be capable, at l e a s t i n p r i n c i p l e of t e s t by experiment or .• o b s e r v a t i o n . (h) The explanans has to' be h i g h l y confirmed by a l l r e l e v a n t evidence a v a i l a b l e . "An e x p l a n a t i o n i s not f u l l y adequate unless I t s explanans, i f taken account of i n time, could have served as a b a s i s • (Ik) f o r p r e d i c t i n g the phenomena under c o n s i d e r a t i o n . " The" Hempel-Oppenheim view of the r e l a t i o n of explanations to causes are c l e a r l y brought to l i g h t i n ; che f o l l o w i n g q u o t a t i o n : " I f E d e s c r i b e s a p a r t i c u l a r event, then the antecedent circumstances described i n the sentences C^ > Cg.-.C^. may be s a i d j o i n t l y to 'cause 1 t h a t event... Statements such as 17 a|, a 2 . . . a r which_assert general and une x c e p t i o n a l connections . between;specified c h a r a c t e r i s t i c s of events are customarily-c a l l e d c a u s a l or d e t e r m i n i s t i c laws." v J J The c a u s a l i t y , which has been described- i n n a t u r a l s c i e n c e , i s not' o c c u l t or unknowable. This c a u s a l i t y i s founded upon answers to 'how q u e s t i o n s ' , . i n the p r e v i o u s l y considered sense, not'why questions'. ;,How questions'', are answered i . e . . ~ explanations are given i n science by showing t h a t the p a r t i c u l a r occurrence of some event i s p r e d i c t e d or i t s occurrence f o l l o w s i n accordance w i t h general laws from some e a r l i e r ( e a r l i e r i n the d e r i v a t i o n ) s i t u a t i o n . . From the preceding d i s c u s s i o n i t should be c l e a r t h a t i t i s not the aim of t h e o r e t i c a l science to di s c o v e r causes. The causes f o r some p a r t i c u l a r occurrence are the s i t u a t i o n s C p (^...C^ from which by means of the laws a^ , a 2 * * ' a r ^ e c 0 1 1 3 8 1 ! 1 1 8 1 1 0 9 5 o r e f f e c t s can be l o g i c a l l y deduced. In t h i s connection i t i s of i n t e r e s t to note the 19th century p h y s i c i s t K i r c h h o f f ' s views: •."In h i s work on mechanics he de c l a r e s t h a t i t ' s o b j e c t i v e i s not to d i s c o v e r the causes of motion; i t i s to desc r i b e completely and i n the simples t manner the motions which occur in" nature under s p e c i f i c conditions.»^^) As we have seen ;Hempel claims a symmetry between explanations and p r e d i c t i o n s . I wish b r i e f l y to i n q u i r e here, 'what are exp l a n a t i o n s ? ' The f u n c t i o n of e x p l a n a t i o n i s c l e a r l y " (in) as M i c h a e l S c r i v e n says to provide understanding. IJ Yet, understanding i s not always a consequence of an explanation.(we say I j u s t don't understand h i s e x p l a n a t i o n f o r the occurrence of X). Nor i s i t r e q u i r e d that explanations always be given f o r 1 8 understanding to. r e s u l t . I f I was t o l d that a wet a i r f r o n t was moving i n from the sea I would understand why i t i s r a i n i n g . That i s , given c e r t a i n f a c t s p e r t i n e n t to X we can o f t e n under-stand 'the occurrence of X. An e x p l a n a t i o n i s not given. Yet, i n a sense an e x p l a n a t i o n i s made. In order f o r an e x p l a n a t i o n t o be given i t would be r e q u i r e d t h a t a d e r i v a t i o n be made i n accordance w i t h general laws, from some given s i t u a t i o n , t h i s c o n s t i t u t e s the explanans statement. Given the f a c t t h a t moist a i r i s moving i n from the ocean and knowing the law t h a t : Whenever moist a i r moves i n from the ocean i t i s f o r c e d to r i s e over the mountains thus c o o l i n g the a i r and forming p r e c i p i t a t i o n , we can understand why i t i s r a i n i n g i n t h i s p a r t i c u l a r s i t u a t i o n . (We can understand what processes have taken place or are t a k i n g place.) Such understanding r e q u i r e d a knowledge of how r a i n i s brought-about and a knowledge that the r e q u i s i t e c o n d i t i o n s are here and now r e a l i z e d . Do we i n general r e q u i r e that laws should be invoked f o r an e x p l a n a t i o n ' o r i s i t s u f f i c i e n t f o r an e x p l a n a t i o n to be given when a p a r t i c u l a r i s subsumed under an e m p i r i c a l g e n e r a l -i z a t i o n ? Is i t an e x p l a n a t i o n to answer the q u e s t i o n , "Why d i d t h i s pen f a l l down?" by saying t h a t under a set of boundary c o n d i t i o n s a l l m a t e r i a l bodies f a l l ? The g e n e r a l i z a t i o n " a l l bodies f a l l " 'requires us to know that the p a r t i c u l a r object under c o n s i d e r a t i o n does so a l s o i . e . t h a t t h i s pen does so a l s o . I f •the p a r t i c u l a r body under c o n s i d e r a t i o n i s i n c l u d e d then the premise already assumes that which i s to be deduced. 19 The previous c o n s i d e r a t i o n s suggest t h a t an e x p l a n a t i o n i n terms of a p a r t i c u l a r occurrence f a l l i n g under a u n i v e r s a l i s f a u l t y . But, o f t e n , j u s t such explanations are u s e f u l and are i n f a c t accepted as s u f f i c i e n t e x p l a n a t i o n s . The a s s e r t i o n t h a t : "His 1953 Chevrolet 'broke down' when the recorded mileage was i n excess of e i g h t y .thousand m i l e s . " may be considered as being explained by showing t h a t ' a l l known automobiles of t h i s make do i n f a c t 'break down' a f t e r being d r i v e n i n excess of ei g h t y thousand m i l e s . Regarding the A r i s t o t e l i a n s y l l o g i s m J.S. M i l l w r i t e s : "The i n f e r e n c e i s f i n i s h e d when we have asserted that a l l men • are m o r t a l . "^"^ I t appears t h a t M i l l i s c o r r e c t i n saying we p e r p e t u a l l y reason from p a r t i c u l a r s to p a r t i c u l a r s . The p a r t i c u l a r men we know to have died serves as a reason or b a s i s f o r saying that some p a r t i c u l a r l i v i n g man i s m o r t a l . The intermediate general p r o p o s i t i o n may be construed as s e r v i n g or f u n c t i o n i n g as a statement f o r some f i n i t e sampling of i n d i v i d u a l s from which, i n f a c t , the reasoning to some other p a r t i c u l a r i s made. '• A l t e r n a t i v e l y , we can view the premise, " A l l men are m o r t a l " as being asserted w i t h a h i g h degree of p r o b a b i l i t y c o n d i t i o n a l l y upon the sta t e d premises. This l a t t e r i n t e r p r e t -a t i o n i s c o n s i s t e n t w i t h the Hempel t h e s i s i n that, a general p r o p o s i t i o n i s used i n the explanans. 2 0 EXPLANATIONS AND PREDICTIONS•IN QUANTUM MECHANICS In the realm of t h e o r e t i c a l science Hempel's symmetry .between explanations and p r e d i c t i o n s does seem to e x i s t . Only quantum mechanics casts s e r i o u s doubt on t h i s t h e s i s , but c o n t r a r y to views advanced by N. R. Hanson, even quantum mechanics d i s p l a y s t h i s symmetry. > N. R. Hanson i n an a r t i c l e ON THE SYMMETRY BETWEEN EXPLANATIONS AND PREDICTIONS a t t a c k s the Hempel t h e s i s t h a t , "the j u s t i f i c a t i o n of a p r e d i c t i o n of P i s symmetrical w i t h the e x p l a n a t i o n of P." He says "Only i n Newton's PRINCIPIA MATHEMATICA PHILOSOPHIAE NATURALIS does the f i n a l i d e a l which Hempel o u t l i n e s (19) seem f u l l y to -be r e a l i z e d . " v / y Hanson looks to quantum physics to f i n d a counter example or a realm of exception to Hempel's conception of e x p l a n a t i o n i n s c i e n c e . He w r i t e s , "The s i t u a t i o n i s , , however, t o t a l l y d i f f e r e n t i n quantum p h y s i c s . . . given any single-quantum phenomena P ( f o r example, the emission of a ^ - p a r t i c l e from a r a d i o a c t i v e substance or the s c a t t e r i n g of a ^-ray photon by an e l e c t r o n ) , P can be completely explained, ex post f a c t o ; one can understand f u l l y j u s t what happened, i n terms of w e l l e s t a b l i s h e d laws of the composite quantum theory...' These laws give the. meaning of e x p l a i n i n g s i n g l e micro-events... But i t i s , of course,' the most fundamental f e a t u r e of these laws that the p r e d i c t i o n of such a phenomenon P. i s , as a matter of t h e o r e t i c a l p r i n c i p l e , q u i t e i m p o s s i b l e . " Hanson repeats t h i s same c l a i m i n the a r t i c l e THE COPENHAGEN INTERPRETATION OF THE QUANTUM THE0RY ( 2 1 ) again without o f f e r i n g any argument f o r the c l a i m that quantum p h y s i c s ' e x p l a i n s ' 21 i n d i v i d u a l micro-events. To meet Hanson's o b j e c t i o n s we may f o l l o w two route s . We may w i t h E i n s t e i n , D e B roglie, Schrodinger and more r e c e n t l y (22) (1957) w i t h Bohmv ' argue that quantum mechancis i s not complete i . e . t h a t f u r t h e r study w i l l r e v e a l hidden parameters which w i l l a l l o w p r e d i c t i o n s to be made of the behaviour of i n d i v i d u a l fundamental p a r t i c l e s . A l t e r n a t i v e l y we may question whether or not i n f a c t quantum physics does e x p l a i n i n d i v i d u a l phenomena i n a sense i n which i t does not p r e d i c t these phenomena. I wish t o . pursue.the second l i n e of o b j e c t i o n , t h a t i s , to i n q u i r e i n what sense quantum physics e x p l a i n s and to i n q u i r e i f there i s not a corresponding sense of p r e d i c t i o n . N. R. Hanson w r i t e s , c o n t i n u i n g h i s c r i t i c i s m of the hidden parameter view, "There i s no i n t e l l i g i b l e way i n t h i s ' -— system (wave mechanics) of speaking of the p o s i t i o n of a h i g h speed e l e c t r o n and there i s no way i n t h i s system of forming p r e d i c t i o n s of c e r t a i n types of events ( f o r example, neutron emission from unstable carbon)." v J J This view or understanding of quantum mechanics does-not d i f f e r i n essence to Linus'.Pauling 1 conception. P a u l i n g w r i t e s , "Schrodinger' s system of dynamics d i f f ers:'from that of Newton, Lagrange and Hamilton i n i t s aim as w e l l as i t s . method. Instead of attempting to f i n d equations which enable a p r e d i c t i o n to be made of the exact p o s i t i o n s and v e l o c i t i e s of the p a r t i c l e s of a system i n a given s t a t e of motion, he devised a method of c a l c u l a t i n g a f u n c t i o n of the coordinates of the system and the time (and not the momenta' or v e l o c i t i e s ) , w i t h the a i d of which, i n accordance w i t h 2 2 the i n t e r p r e t a t i o n developed by Born, probable values the coordinates and other dynamical quantities can be (.2k) predicted f o r the system." x ' I wish to consider the physical (Born) i n t e r p r e t a t i o n of the Schrodinger wave function"\|r. In the one dimensional case ij/" i s a'function of x and t, i . e . \|/ (x,t) .. For a given value of the time t, l j / * ( x , t ) ( x , t ) , i . e . , the product of and i t s complex conjugate, i s a function defined f o r a l l values of x between - oo and + 0 0 ; that i s , throughout the con-f i g u r a t i o n of space of t h i s one dimensional system. I t i s the Born postulate that: r,The quantity \j/"*(x,t) 1 ^ (x,t)dx i s the p r o b a b i l i t y that the system i n the physical s i t u a t i o n repre-sented by the wave function \|/(x,t) have at the time t the configuration represented by a point i n the region dx of the configuration space.>'^25) "\|r * ( x ? t ) (x,t)dx i s the probabi-l i t y that the p a r t i c l e l i e s i n the region between x and x+dx at the time t . But i n talking about p a r t i c l e s or waves we are tal k i n g about macroscopic concepts. The solution to Schrodinger^ equation f o r a free p a r t i c l e i s of a sinusoidal character. Wave functions as obtained by a so l u t i o n of Schrodinger»s equation "give r i s e to experimental phenomena which are c l o s e l y similar to those associated in'macroscopic f i e l d s with wave functions. Neither view ( p a r t i c l e or wave) i s without l o g i c a l d i f f i c u l t i e s , i n as much as waves and p a r t i c l e s are macroscopic concepts which are d i f f i c u l t to apply to microscopic phenomena."^ ' The reason for adhering to the p a r t i c l e concept i n wave mechanical c a l c u l -ations i s simply to give a good i n t u i t i v e f e e l i n g f o r the mathematical r e s u l t s . 23 The f a c t i s that quantum mechanics, (the mathematical s t r u c t u r e ) does not e x p l a i n i n d i v i d u a l events any more than i t p r e d i c t s i n d i v i d u a l events, not because of some l i m i t a t i o n s i n ' the theory but because t h e . p a r t i c l e s aren't t h e r e . Both p a r t i c l e s .and waves are macroscopic concepts. We can f o r c e Hanson i n t o a dilemma. E i t h e r ( i ) the phenomena of experience-are explained by quantum mechanics or ( i i ) the phenomena of experience are explained i n terms of the concepts of c l a s s i c a l physics .in which meaning i s given s p e c i f i c a l l y to the concept of a p a r t i c l e at a p o i n t i . e . space at a given time i . e . P ( x , y , z , t ) . I f ( i ) i s adopted then i n d i v i d u a l events ( c l i c k s on.a Geiger counter) cannot be explained i n terms of quantum mechanics. I n d i v i d u a l events s a i d to be o c c u r r i n g at P ( x , y , z , t ) are not quantum mechanical concepts. A l t e r n a t i v e l y i f we adopt ( i i ) then meaning i s attached to the concept of a p a r t i c l e at ( x , y , z , t ) . But, c l a s s i c a l mechanics i s not competent to d e a l w i t h microphysics. Attempts at . e x p l a i n i n g black-body r a d i a t i o n and the p h o t o - e l e c t r i c e f f e c t showed the l i m i t a t i o n s of c l a s s i c a l mechanics. The quantum mechanical d e s c r i p t i o n of a p a r t i c u l a r p a r t i c l e according to the Born i n t e r p r e t a t i o n i s j u s t the | " \ | / ~ ^ p r o b a b i l i t y f u n c t i o n solved w i t h some s p e c i f i e d i n i t i a l c o n d i t i o n s . Suppose we are asked to e x p l a i n the. d i f f r a c t i o n of e l e c t r o n s by a c r y s t a l . A d e t e c t o r placed at a c e r t a i n angle i n d i c a t e s t h a t e l e c t r o n s are being r e c e i v e d - what i s the explan-a t i o n f o r t h i s observation? To account f o r the o b s e r v a t i o n we assume that what i s . . c a l l e d beam of e l e c t r o n s v i z . a wave of r E frequency y = r- f a l l s on the c r y s t a l , and we c a l c u l a t e the 2h i n t e n s i t y of" the waves s c a t t e r e d i n the d i r e c t i o n s p e c i f i e d . The r e s u l t of such a c a l c u l a t i o n i n d i c a t e s w i t h i n l i m i t s what the detector i s expected. ; to r e c o r d . ' I t i n d i c a t e s angles of hig h p r o b a b i l i t y and.low p r o b a b i l i t y f o r f i n d i n g e l e c t r o n s . I t i s the case, as Hanson says, that p r e d i c t i o n s of i n d i v i d u a l quantum phenomena.are q u i t e i m p o s s i b l e , but so are a l s o e x p l a n a t i o n s . Hanson .says' t h a t the . symmetry t h e s i s i s v i o l a t e d , since "...a Geiger counter i n t e r c e p t i n g ^ p a r t i c l e s from an unstable i s o t o p i c source, w i l l c l i c k i n a wholly u n p r e d i c t a b l e way. Once a p a r t i c l e has been emitted the counter's c l i c k i s determined c l a s s i c a l l y . But it . r e m a i n s c o n c e p t u a l l y untenable .to p r e d i c t when.a p a r t i c l e w i l l be emitted, and hence when the counter w i l l . n e x t c l i c k . . . I t s macrophysical c l i c k s (27) must be 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 J Hanson's mam e f f o r t . i s d i r e c t e d to denying the hidden parameter'view. My t h e s i s does not r e q u i r e a defence of the hidden parameter view. Whereas i t i s q u i t e c l e a r what quantum mechanics does not p r e d i c t i t i s not c l e a r what quantum mechanics i s s a i d by Hanson to e x p l a i n and what i n f a c t i t does e x p l a i n . On page 31, .' CONCEPT OF THE POSITRON, he says: . "A quantum t h e o r e t i c account of.these phenomena ( s i n g l e ' neutron emission from unstable carbon) does e x p l a i n , to a' considerable extent, what k i n d of p h y s i c a l events they are." From the preceding two quotations i t appears t h a t quantum mechanics i s r e q u i r e d to e x p l a i n ( i ) the u n p r e d i c t a b l e c l i c k s on a Geiger counter ( i i ) the emission of neutrons ( p a r t i c l e s ) from r a d i o a c t i v e m a t e r i a l . 25 To maintain h i s t h e s i s , then, Hanson must c l a i m t h a t b o t h . ( i ) and ( i i ) are explained by quantum mechanics. I t i s c l e a r l y not s u f f i c i e n t to say as Hanson does i n the preceding q u o t a t i o n "explained to a considerable extent" f o r then to main t a i n the symmetry, t h e s i s we would only have to say " p r e d i c t e d to a considerable extent." Hempel suggests only t h a t the symmetry i s between complete explanations and p r e d i c t i o n s . Let us t u r n to Hempel's own answer to Hanson's c r i t i c i s m : " I f the i n f o r m a t i o n that P has occurred were in c l u d e d i n the explanans', the r e s u l t i n g " account would be u n i l l u m i n a t i n g l y c i r c u l a r . . . And i f the explanans contains only statements about antecedent c o n d i t i o n s , plus a s t a t i s t i c a l law of r a d i o a c t i v e decay, then i t can show at best that the occurrence of P was h i g h l y probable; but t h i s a f f o r d s only an i n d u c t i v e - s t a t i s t i c a l e x p l a n a t i o n , which has the same l o g i c a l form as the p r o b a b i l i s t i c i . e . i n d u c t i v e , p r e d i c t i o n of P . " ( 2 8 ) Hanson does not, a p a r e n t l y , want to r e s t r i c t h i m s e l f to a s p e c i f i c statement of what he means by. 1 e x p l a i n ' . The •fo l l o w i n g he does say about e x p l a n a t i o n . A r i s t o t l e ' s cosmology made the cosmos "more i n t e l l i g i b l e to h i s contemporaries and, i n (29) some sense t h i s must count as ' e x p l a n a t i o n ' . " v / J Hanson i s p a r t i c u l a r l y i n t e r e s t e d i n what have counted as explanations i n the past, f o r example, L e i b n i z d i d not t h i n k the PRINCIPIA offered-explanations but served only as a mathematical p r e d i c t i n g device. To ' e x p l a i n ' i n the past, suggests Hanson, has been used as meaning: to r e l a t e to the i n t u i t i v e l y evident.' 'Post d i c t i o n ' does not always s a t i s f y these c o n d i t i o n s . 26 On page .1 i n the i n t r o d u c t i o n to the CONCEPT OF THE POSITRON Hanson w r i t e s , "The 'hole-theory' of the p o s i t i v e e l e c t r o n i s an e x p l a n a t i o n of t h i n g s l i k e p a i r c r e a t i o n and a n n i h i l a t i o n ; none the l e s s , as a matter of p r i n c i p l e , t h i s theory cannot p r e d i c t when any given p a i r w i l l he created." U n f o r t u n a t e l y Hanson does not f u r t h e r e l a b o r a t e , i n h i s w r i t i n g , e x a c t l y how t h i s theory ' e x p l a i n s ' . The few words devoted to the subject present an analogy w i t h a concrete s i t u a t i o n . I t i s not at a l l clear- what c o n s t i t u t e s the e x p l a n a t i o n . Continuous j?, emission spectrum i s s a i d to be explained by p o s t u l a t i n g n e u t r i n o s . Neutrinos are given the p r o p e r t i e s charge = .0, r e s t mass = 0, l i n e a r momentum = P, r e l a t i v i s t i c energy = PC, and angular momentum - ~k \ which are r e q u i r e d to e x p l a i n the continuous j% spectrum. On page-12+ Fermi i s quoted as saying: "The whole s t o r y about fundamental p a r t i c l e s i s th a t they show themselves to have j u s t those p r o p e r t i e s they must • have i n order to e x p l a i n the l a r g e - s c a l e phenomena which r e q u i r e e x p l a n a t i o n . . . The existence of the neutrino has been suggested as an a l t e r n a t i v e to the apparent l a c k of co n s e r v a t i o n of energy i n ^ d i s i n t e g r a t i o n . " ."What i s to be explained here i s the observed continuous ^ > spectrum. This i s done by p o s t u l a t i n g a new p a r t i c l e which c a r r i e s o f f the energy which has •to be accounted f o r i n order to s a t i s f y the co n s e r v a t i o n of charge, mass angular momentum and energy. Given t h i s .microphysical s t r u c t u r e i t seems c l e a r that an e x p l a n a t i o n f o r the observed continuous emission spectrum i s found -in micro p h y s i c s . I b e l i e v e , however, th a t one can p r e d i c t a continuous 27 . ^ spectrum where, we know tha t the energy l o s t i n the atomic d i s i n t e g r a t i o n would be shared between two p a r t i c l e s (the p o s t u l a t e d n e u t r i n o and the e l e c t r o n ) according to some s t a t i s t i c a l law. P o s t u l a t e s are o f t e n made in- science to a i d i n the e x p l a n a t i o n of phenomena i . e . the p o s t u l a t e d n e u t r i n o allowed an e x p l a n a t i o n to.be made of the continuous ^ emission spectrum. Yet, i t i s Important to. note the s t a t u s of p o s t u l a t e d . e n t i t i e s . Let us consider another p o s t u l a t e . I t was observed e a r l y i n the physical'work on heat t h a t 'heat energy' t r a n s f e r could be e a s i l y , understood by p o s t u l a t i n g that heat was a f l u i d ( c a l o r i c ) . Such phenomena as temperature e q u i l i b r i u m of two bodies i n contact could w i t h t h i s p o s t u l a t e be r e a d i l y understood i n terms of the more f a m i l i a r p r o p e r t i e s of f l u i d s . Then to e x p l a i n why two metal bars, one at a higher temperature T-g, the other at a lower temperature T^ ,. reached an e q u i l i b r i u m at some intermediate temperature T^ -, one would say that t h i s was a consequence of the behaviour of f l u i d s (they seek t h e i r own l e v e l ) . We, however, have learned from the t r i a l s of the past what i s to c o n s t i t u t e a f r u i t f u l or s i g n i f i c a n t p o s t u l a t e i n science. I t i s r e q u i r e d that such p o s t u l a t e s f u n c t i o n i n f u t u r e p r e d i c t i o n s , that f u t u r e experimental r e s u l t s can be p r e d i c t e d i n terms of the e a r l i e r p o s t u l a t e s . P o s t u l a t e s must not o n l y f a c i l i t a t e i n the making of explanations but must a l s o f u n c t i o n i n p r e d i c t i o n s . Furthermore we r e q u i r e that coherence should be maintained i n the d i s c i p l i n e . I n t r o d u c t i n g the f l u i d or c a l o r i c theory of heat i s to introduce i n c o n s i s t e n c i e s i n the sense i n which we introduce a f l u i d , c a l o r i c , which i s i n v a r i a n c e w i t h a l l known f l u i d s i n being without weight. (This" 28 i s a se r i o u s i n c o n s i s t e n c y i n so f a r as i t i s no longer under-standable how a wei g h t l e s s f l u i d can seek i t s own l e v e l . ) As I understand Hanson's o b j e c t i o n to the symmetry t h e s i s i t i s simply t h i s : We understand what happens when h i g h energy p a r t i c l e s emitted 'randomly 1 by r a d i o a c t i v e matter i n t e r a c t w i t h the measuring device producing a f l a s h which i s . a m p l i f i e d and recorded. I t i s q u i t e true t h a t the c o l l i s i o n of an e l e c t r o n w i t h an atom which brings the atom to a higher energy l e v e l and : -the eventual emission of a photon i s a quantum phenomena which i n f a c t c o n s t i t u t e s an "e x p l a n a t i o n of what goes on i n the counter." I b e l i e v e that t h i s i s what Hanson means when he says th a t quantum mechanics e x p l a i n s i n d i v i d u a l events. Yet, c l e a r l y , t h i s i s not the problem w i t h which we are g r a p p l i n g . Consider the analogy; one may understand p e r f e c t l y w e l l the mechanism or the process t h a t i s o c c u r r i n g when i t i s r a i n i n g without being i n the l e a s t aware why i t i s r a i n i n g at t h i s p a r t i c u l a r time and p l a c e . This understanding r e q u i r e s p r i o r knowledge of p a r t i c u l a r a i r c u r r e n t s , a i r moistures and temperatures, know-l e d g e which o f t e n enough i s n o t . a v a i l a b l e even to the meteorol-o g i s t . I t i s p o s s i b l e to know and to e x p l a i n what i s happening when i t i s r a i n i n g without being able to e x p l a i n why i t I s r a i n i n g here now. In quantum mechanics i t i s p r e c i s e l y the'here now"which i s not e x p l i c a b l e . Hanson claims t h a t there-are two consequences of accepting quantum mechanics, n e i t h e r of which I have any reason to r e j e c t and n e i t h e r of,which serves as a c r i t i c i s m of the Hempel-Oppenheim t h e s i s . They are ( i ) there i s no i n t e l l i g i b l e way i n t h i s system of speaking. 29 of the exact p o s i t i o n of an e l e c t r o n of p r e c i s e l y known energy. ( i i ) there i s no way i n t h i s system of forming p r e d i c t i o n s of c e r t a i n types of events ( i n d i v i d u a l quantum events). I f there i s no i n t e l l i g i b l e way i n t h i s system of speaking of' the exact p o s i t i o n "how then can i t make sense to say there i s an i n t e l l i g i b l e way to e x p l a i n p r e c i s e l y that which we cannot speak about?" • . . I wish to t u r n to some arguments i n Ern s t C a s s i r e r ' s DETERMINISM AND INDETERMINISM IN MODERN PHYSICS to make my case stronger. The e s s e n t i a l case f o r indeterminism i n C a s s i r e r ' s account centers on the f a c t t h a t knowledge of the i j / " f u n c t i o n at some time t , as t^"(x,t^) allows "v|r ( x , t ^ ) to be p r e d i c t e d f o r some l a t e r time t . The Schrodinger equation can only y i e l d a s i n g l e - v a l u e d , f i n i t e and continuous s o l u t i o n . There i s nothing indeterminant about the wave f u n c t i o n . C a s s i r e r w r i t e s : "When the theory of r a d i o a c t i v e decay d e c l a r e s that f o r every substance there e x i s t s a c e r t a i n p r o b a b i l i t y that an atom chosen at random will•decompose w i t h i n a randomly, chosen i n t e r v a l of time; when i t i s shown th a t there i s a d e f i n i t e e x p o n e n t i a l law governing the decay; when accor-d i n g l y the 'decay s e r i e s ' of v a r i o u s r a d i o a c t i v e f a m i l i e s are e s t a b l i s h e d - then these are a l l extremely p r e c i s e c o n c l u s i o n s , even though they say nothing about the f a t e of the i n d i v i d u a l atom and the p r e c i s e i n s t a n t of i t s d e c o m p o s i t i o n . " ^ ^ 30 The f a c t t h a t i n d i v i d u a l p r e d i c t i o n i s not p o s s i b l e i n quantum mechanics, does not e s t a b l i s h a counter example to the symmetry t h e s i s . P r e d i c t i o n s are p o s s i b l e i n quantum mechanics; f o r example, decay w i l l occur according to a d e f i n i t e exponen-t i a l law. To ask f o r a p r e d i c t i o n of an i n d i v i d u a l neutron v i z . p a r t i c l e i s to ask f o r something which i s not even a quantum mechanical concept. The Born i n t e r p r e t a t i o n speaks about the p r o b a b i l i t y of there being a p a r t i c l e i n a d e f i n i t e volume. The concept of a p a r t i c l e at a p o i n t i n space at some time P ( x , y , z , t ) has no counterpart i n quantum mechanics. C a s s i r e r i s i n agreement w i t h Planck's statement to the e f f e c t t h a t the problem "whether a c e r t a i n q u e s t i o n i s meaningful i n p h y s i c s , can never be a r r i v e d at a p r i o r i but always and s o l e l y from the p o i n t of view of a given theory, the d i f f e r e n c e between the d i f f e r e n t t h e o r i e s c o n s i s t i n g p r e c i s e l y i n the f a c t t h a t according to one theory a c e r t a i n q u a n t i t y i s observable i n p r i n c i p l e , or a c e r t a i n question i s p h y s i c a l l y ni) meaningful w h i l e according to the other i s n o t . " w ' Hanson h i m s e l f has s a i d t h a t p a r t i c u l a r C ^ atoms are i n d i s t i n g u i s h -able ( w i t h i n .a given theory i . e . quantum mechanics). So a l s o are the fundamental p a r t i c l e s . ( I t h i n k Hanson's reasoning i s c o r r e c t on t h i s p o i n t ) . W i t h i n quantum mechanics, i n d i v i d u a l C 1 ! + atoms are i n d i s t i n g u i s h a b l e . This i s granted by Hanson. I t f o l l o w s i n accordance w i t h the P l a n c k - C a s s i r e r view that w i t h respect to the theory, the question which atom emitted the ^ p a r t i c l e i s meaningless. Then, quantum theory does not e x p l a i n t h e . s i t u a t i o n of a p a r t i c u l a r atom e m i t t i n g a p a r t i c u l a r e l e c t r o n . , 31 An o b s e r v a t i o n may be made i n a 'bubble-chamber 1.of a t r a c k ; the t r a c k i s spoken of as having i t s o r i g i n i n the r a d i o a c t i v e m a t e r i a l which i s contained w i t h i n the chamber. A person possessing other i n f o r m a t i o n f a c t u a l and t h e o r e t i c a l i . e . knowledge what the p a r t i c u l a r r a d i o a c t i v e m a t e r i a l i s and presupposing a model .or theory of r a d i o a c t i v e decay may make the statement: - "A ^ - p a r t i c l e was emitted at 12:22, as measured on my watch from the' C'-^ sample." :He might f u r t h e r add that some p a r t i c u l a r C-^ atom underwent a decay r e a c t i o n w i t h the consequent l o s s of an e l e c t r o n . But the preceding statement cannot be t r a n s l a t e d i n t o quantum mechanical terms wh i l e p r e s e r v i n g the macroscopic concept " p a r t i c l e here now." In the quantum mechanical case the best we can do i s a s s e r t ' p a r t i c l e ' i s i n the volume element /XV . Only a value of the "Ap"function i s d e f i n e d . This means (Born i n t e r p r e t a t i o n ) that the explanandum i s a p r o b a b i l i t y i . e . the p r o b a b i l i t y that a We know the p r e d i c t i o n s of p r o b a b i l i t i e s are adequately handled by quantum mechanics. For t h i s reason i t i s c l e a r t h a t Hanson has not constructed a counter example or a realm of exception to the Hempel-Oppenheim conception of e x p l a n a t i o n i n scienc e . e s s e n t i a l f e a t u r e s of the concept of ex p l a n a t i o n . We e x p l a i n the presence of a gas by r e f e r r i n g to the behaviour of very small unobservable e l a s t i c p a r t i c l e s i n c o n t i n u a l motion. We e x p l a i n the formation of a p r e c i p i t a t e i n a t e s t tube by that dv - p r o b a b i l i t y that a p a r t i c l e ' i s i n the volume element A N / . Perhaps the foregoing d i s c u s s i o n has missed some 32 r e f e r r i n g to t h e ' i n t e r a c t i o n s of i o n s . I t i s M. Scriven's c l a i m t h a t : ,J,We are committed to e x p l a i n i n g macro-phenomena i n terms of micro-phenomena and thus must b e l i e v e t h a t the t r u t h s of the macro-level (whether o b s e r v a t i o n a l or statements about t h e o r e t i c a l e n t i t i e s ) can be accounted f o r i n .micro terms."^ He reasons that chemical r e a c t i o n s must be explained i n atomic terms since the l e v e l to which we t u r n f o r an e x p l a n a t i o n of• what we accept' 'as b a s i c data' i s p r e c i s e l y t h i s l e v e l . Suppose we wish to e x p l a i n the emission of a neutron, from some piece of r a d i o a c t i v e m a t e r i a l as recorded on a s c i n t i l l a t i o n counter at some time t . The explanandum i s a • macrophysical observable phenomenon. The explanans invokes the realm of m i c r o p h y s i c s . In order t o . s a t i s f y . t h e Hempel-Oppenheim c r i t e r i a f o r e x p l a n a t i o n , the e x p l a n a t i o n must s a t i s f y f o u r c o n d i t i o n s of adequacy. The f i r s t c o n d i t i o n s t a t e s t h a t the explanandum must be l o g i c a l l y deducihle from the i n f o r m a t i o n contained i n the explanans. The 'here now presence 1 of the neutron cannot be explained by quantum mechanics. On the other hand, i f the explanandum i s s t a t e d as the p r o b a b i l i t y of X then the f i r s t . c o n d i t i o n of adequacy i s s a t i s f i e d . Whereas i t may the the case that we e x p l a i n macro-phenomena i n terms of micro-phenomena i t does not f o l l o w that there i s or can be complete e x p l a n a t i o n s , i n Hempel's sense, f o r a l l macro-phenomena. In f a c t there does not e x i s t an e x p l a n a t i o n , i n terms of quantum mechanics, f o r i n d i v i d u a l events as ' p a r t i c l e here now'. The Hempel-Oppenheim t h e s i s remains i n t a c t . 33 CONCLUSION Although causes are e x p l i c i t l y mentioned i n s c i e n c e , t h e i r use i s r e s t r i c t e d to the p r a c t i c a l s c i e n c e s . They o n l y give a fragmentary account of the r e l a t i o n between occurrences or events i n the world. Science i n general serves to answer 'how questions',-as contrasted w i t h 'why questions'. Our knowledge of the world as given by a t h e o r e t i c a l science i s expressed by what . we c a l l p h y s i c a l laws. These laws are not f u n c t i o n s of the time, although, of course the laws describe the behaviour of phenomena i n time i . e . they a l l o w p r e d i c t i o n s and r e t r o -d i c t i o n s of f u t u r e and past occurrences. Hempel has l a b e l l e d these laws c a u s a l . Quantum mechanics maintains s t r i c t c a u s a l i t y i n the sense that l a t t e r s t a t e s of the f u n c t i o n are d e t e r -minable from i t s e a r l i e r s t a t e s . I t i s not s u r p r i s i n g t h a t accounts d e s c r i b i n g i n d i v i d u a l fundamental p a r t i c l e behaviour are not p o s s i b l e since such e n t i t i e s construed as i n d i v i d u a l mass p o i n t s having exact s p a c i a l coordinates at an i n s t a n t are f i c t i o n s . The i m p l i c a t i o n drawn from" t h i s I s that c a u s a l i t y as understood above, (present s t a t e s a l l o w knowledge of f u t u r e s t a t e s ) , i s preserved. 3>+ NOTES CD John Locke, ESSAY CONCERNING HUMAN UNDERSTANDING, (Dover P u b l i c a t i o n s , New Y o r k ) , Volume 1, Chapter XXVI, page 43^ (2) Bertrand R u s s e l l , MYSTICISM AND LOGIC, (Unwin Books, London, 1963), Chapter IX, page 132 . (3) ' A. Wilson and H. 0 . S c h i l d , APPLIED PHARMACOLOGY, (Ninth E d i t i o n , C h u r c h i l l L t d . , London, 1 9 5 9 ) , page l 8 l (4) . G i l b e r t R y l e , THE CONCEPT OF MIND, (Barnes and Noble, • • New York, 1964 e d i t i o n ) , . Chapter IV, page 110 . (5) ;'• I b i d , page 113 (6) I b i d , Chapter I I , page 43 (7) R. W. Ditchburn, LIGHT,- ( B l a c k i e and Son L t d . , London, 1 9 6 1 ) , Chapter' 17 , S e c t i o n 6, The Rutherford-Bohr Atom, page J?VM-(8) N. R. Hanson, PATTERNS OF DISCOVERY, (Cambridge, Eng., U n i v e r s i t y P r e s s , 1958) , page 5^ (9) Ernst Schumacher, DER-FALL GALILEI, ( /The Case of G a l i l e i / , B e r l i n , 1964, my t r a n s l a t i o n ) , page 31 (10) G a l i l e i G a l i l e o , DISCOVERIES AND OPINIONS OF GALILEO, (Doubleday e d i t i o n , 1957? T r a n s l a t e d by Stilman Drake), pages 123-4-(11) P. H. Nowell-Smith, ENCYCLOPAEDIA BRITANNICA, ( 1 9 6 5 ' e d i t i o n ) , page 106 (12) Anatol Rapoport, OPERATIONAL PHILOSOPHY, (Wiley and Sons, New York, 1 9 6 5 ) , Chapter 5 , page 51 (13) C. G. Hempel and P. Oppenheim, THE LOGIC OF EXPLANATION, (Reprinted from the Philosophy of Science, 19^8, i n F. F e i g l and M. Brodebeck READINGS IN THE PHILOSOPHY OF SCIENCE, New York, Appleton-Century-Crofts, I nc., 1953), page 321 (14) I b i d , page 323 (15) I b i d , page 324 (16) V. F. Lenzen, CAUSALITY IN NATURAL .SCIENCE, (C. Thomas, S p r i n g f i e l d , I l l i n o i s , 1 9 , page 12 (17) M. S c r i v e n , NEW ISSUES IN THE LOGIC OF EXPLANATION, (PHILOSOPHY AND • HISTORY, S. Hook e d i t o r , New York, U n i v e r s i t y P r e s s , 1 9 6 3 ) , page 340 35 . 0 8 ) J . S. M i l l , A SYSTEM OF LOGIC, (Longmans, Green and Co., London, 1900), Book I I , Chapter. I l l 0 9) N. R. Hanson, ON THE SYMMETRY BETWEEN 'EXPLANATIONS AND PREDICTIONS^ (The P h i l o s o p h i c a l Review, 1959, 68), page 351 (20) ' I b i d , page 351 (21) • N. R. Hanson, THE COPENHAGEN INTERPRETATION OF THE • QUANTUM THEORY, (Reprinted in"PHILOSOPHY OF SCIENCE, S. Morgenbesser". and E. N a g e l ) 5 page h-63 (22) D. Bohm, A PROPOSED EXPLANATION OF QUANTUM THEORY ' IN TERMS OF HIDDEN VARIABLES AT A SUB-QUANTUM-MECHANICAL LEVEL (OBSERVATION AND INTERPRETATION, e d i t e d by S. Kdrner, London, 1957)? pages 33-^ +1 (23) N. R. Hanson, ON THE SYMMETRY BETWEEN "EXPLANATIONS AND PREDICTIONS, (The p h i l o s o p h i c a l Review, 1959), • page (2*f) Linus C a r l P a u l i n g , INTRODUCTION TO QUANTUM MECH ANICS, (McGraw-Hill, New York, 1935), page 51 ^ (25) I b i d , pages 6*f-5 (26) I b i d , page 93 (27) N..R. Hanson, THE CONCEPT OF THE POSITRON, (Cambridge, Eng., U n i v e r s i t y P r e s s , 1963), page 55 (28) C. G. Hempel, ASPECTS OF SCIENTIFIC EXPLANATION, (Free Press, 1956), page 0^7 (29) N. R. Hanson, THE CONCEPT OF THE POSITRON, (Cambridge, Eng., U n i v e r s i t y P r e s s , 1963), page 26 (30) Ernst C a s s i r e r , DETERMINISM AND INDETERMINISM IN MODERN PHYSICS, (Oxford U n i v e r s i t y P ^ s s , 1956 e d i t i o n ) , page 118 . . (3D I b i d , page 126 (32) M. S c r i v e n , DEFINITIONS, EXPLANATIONS AND THEORIES, (Volume I I , MINNESOTA STUDIES IN THE PHILOSOPHY OF SCIENCE, 1958, H. F e i g l , M. S c r i v e n and G. Maxwell), pages 99-195 36 BIBLIOGRAPHY Bohm, D 1957 A PROPOSED EXPLANATION OF QUANTUM THEORY IN TERMS •'. OF HIDDEN VARIABLES AT A SUB-QUANTUM-MECHANICAL . LEVEL, p r i n t e d i n Observation and I n t e r p r e t a t i o n , London, Butterworth's S c i e n t i f i c P u b l i c a t i o n s -C a s s i r e r , E. 1956 DETERMINISM AND INDETERMINISM IN MODERN PHYSICS, Oxford U n i v e r s i t y Press ; • . Ditchburn, R. W. 1961 LIGHT, London, B l a c k i e and. 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