8/11/2019 dretske 1971

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Australasian Journa l o f Philosophy

Vol. 49, No. 1; May, 1971

FRED DRErSKE

C O N C L U S I V E R E A S O N S *

Conc lus iv e r ea sons have a mo da l a s we l l a s an ep i s t emic cha rac t e r . In

hav ing conc lu s ive r ea sons t o be l i eve t ha t P i s t he ca se one s ep i s t emic c reden-

t ia l s a re such a s t o e lim ina t e t he poss ib i l i t y o f mi s t ake . Th i s , a t l ea s t , is

h o w I p r o p o s e t o u n d e r s t a n d t h e m f o r t h e r e m a i n d e r o f t h is p a p e r . L e t t i n g

t h e s y m b o l ( ) r e p r e s e n t t he a p p r o p r i a t e m o d a l i t y ( a y e t t o b e c l ar i fi e d se n se

o f possibility , I sha l l say , t hen , t ha t R i s a conc lus ive r ea so n fo r P i f and

only i f , g iven R, ~ ( ) ,-~ P (or , a l te rna t ive ly , ~ ( ) (R . ~ P)) . This inter-

p r e t a t i o n a l lo w s u s t o s a y o f a n y s u b je c t, S , w h o b e l ie v es t h a t P a n d w h o h a s

conc lus ive r ea sons fo r be l i ev ing tha t P , t ha t , g iven the se r ea sons , h e couM

not be wrong abou t P o r , g iven the se r ea sons , i t is false that he might be

mistaken a b o u t P .

S u p p o s e , t h e n , t h a t

( I ) S kno ws th a t P and h e know s th i s on t he ba s i s ( s imply) o f R en ta i l s

(2 ) R w ould no t be t he ca se un l e ss P we re t he ca se . 1

The l a t t e r fo rmula expre sse s a connec t ion be tween R and P which i s s t rong

enough , I submi t , t o pe rmi t us t o say t ha t i f (2 ) i s t rue , t hen R i s a conc lus ive

rea son fo r P . Fo r i f (2 ) i s t rue , we a re en ti t l ed , no t on ly t o deny tha t , g iven R ,

n o t - P is t h e c a s e, b u t a l s o t h a t , g i v e n R , n o t - P might be the ca se . Tha t i s t o

say , (2 ) e l im ina t e s R an d no t -P a s a poss ib l e ( j o in t ) s t a te o f a f f a ir s and , w hen

we a re given R, i t e l im ina t e s no t - P a s a poss ib l e s t a t e o f a f f ai r s . Th i s i s so

because (2 ) en t a i l s t he f a l s i t y o f ,

(3 ) Al though R i s t he ca se P migh t no t be t he ca se .

I f we expre ss (3 ) a s Giv en R , ( ) ,-~ P , t hen (2 ) en t a i l s t ha t i t is f al se t ha t,

g iven R , ( ) ~ P which is equ iva l e n t t o , g iven R , ~ ( ) ~ P ; and th is i s

p rec i se ly t he r equ i red f ea tu re o f conc lus ive r ea sons g iven above . Hence ,

when (2 ) i s t rue , R i s a conc lus ive r ea son fo r P .

W h a t f o l l o w s is a n am p l i f i c a ti o n o f t h e a b o v e s k e t c h - - h e n c e , a n a r g u m e n t

fo r t he v i ew tha t i n t hose ca ses whe re kno wledg e t ha t P r e s t s on ev idence ,

*An early version o f this paper was read to the P hilosophy Department at The Uni-

versity of Illinois, Chicago Circle. Mo re recently it was read at Th e University o f No rth

Carolina s Colloquium in Philosophy with Professor Robert Sleigh commenting.

x I shall be using R and P to replace a variety of related gram matical units. Depen ding

on the sentential context, they sometimes serve as no un phrases, sometimes as full

indicative sentences, sometimes for appropriate transformations of the indicative.

Fred Dre t ske

gr ounds , o r r ea sons , whe n the que s t ion How doe s S know ? c a n se ns ib ly

be asked and answered, the evidence , grounds , or reasons mus t be conc lus ive .

Any th ing sho r t o f c onc lus ive r e a sons , t hough i t m a y p r ov ide one wi th

jus t i fied t rue be l ie fs , f ai l s to g ive the k ind of suppo r t requis i te to knowledge .

I sha l l a lso urge tha t the possess ion of conc lus ive reasons to be l ieve , prope r ly

qualif ied, is a lso a suff icient condition for knowledge.

1 Knowing P on the Bas i s o f R: The Connec t ion Be tween (1) a n d (2).

Suppose S , in order to assure h imse lf tha t h is chi ld s tempe ra ture i s

norm al (no fever ), p laces a the rm ome ter in the chi ld s mou th , ext rac ts i t

a f te r severa l minutes , and observes a reading of 98.6 F . In remarkin g to the

doc tor tha t h is chi ld s tempe ra ture i s normal S is asked ho w he know s.

S responds , na tura l ly enough, by saying, I jus t t ook his tempera tu re .

Le t us assume, then, tha t w e have an ins tant ia t ion of (1):

( la ) S knows tha t h is chi ld s tempe ra ture i s norm al and he know s th is

on the ba si s o f t he ( no r m a l ) r e a d ing on the the r m om e te r ( wh ic h

he has jus t p laced in the chi ld s mo uth , e tc .) .

Can one consis tent ly a f f i rm ( la ) and deny the cor responding ins tant ia t ion of

(2)?

(2a) The therm ome ter wou ld not have rea d 98.6 unless the chi ld s

t e m pe r a tu r e wa s no r m a l .

I f i t i s not a l ready obvious tha t one cannot consis tent ly a f f i rm ( la ) and deny

(2a) , I th ink i t can be made obvious by consider ing the k ind of th ing which

would sh ow (2a) to be false . Fo r example , i f Char les, f amil ia r wi th the

par t icula r the rm om eter in quest ion, should say, Oh, I know th a t the r -

mom eter ; i t i s f ai r ly accura te for tempera t ures be low 98 but i t s t icks a t

98.6 for a lmos t any higher tempera ture , we have been given sol id grounds f or

re jec t ing (2a) . S imul taneously , however , we have been given sol id grounds

for re jec t ing ( la ) . I f it is that kind of the rmom eter , then i f S s only bas is for

th inking his chi ld s tempe ra ture no rmal i s a 98.6 reading on i t , then he does

n o t k n o w tha t h is child s tempera tu re is normal . I t mi ht be no r m a l , o f

course , but i f S know s tha t i t is , he must h ave more to go o n than the reading

on th is (defec t ive) the rmo meter .

Other a t tempts to show (2a) fa lse have the same e f fec t ; they immedia te ly

undermine R ( the reading on the the rmometer ) as an adequa te bas is for

someon e s knowin g tha t the chi ld s tempe ra ture i s normal (P) . Fo r in

re jec ting (2a) we re jec t the th e rmo meter as a re l iable device for d iscover ing

whether a person s tem pera ture i s normal , an d know ledge is not acquired

by re ly ing on what i s unre liable in prec ise ly those respec ts in which we re ly

on it .

We f requent ly purp or t to know things on the bas is of tes t imony. James

has a la rge s tamp col lec t ion and, a f te r g iv ing a de ta i led descr ip t ion of i t ,

invites S to his hom e to see i t . S declines, but he later refers to Jam es stam p

col lec t ion in conversa t ion. I t is easy enoug h to imagine c i rcumstances in

which i t would be na tura l for som eone to ask S how he knew, wha t reasons

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Conc l us i ve R easons

h e h a d f o r t h i n k i n g , t h a t J a m e s h a d s u c h a c o l l ec t i o n. A n d i t i s j u s t a s e a s y

t o i m a g i n e S , i n r e s p o n s e t o s u c h a q u e r y , r e f e r r i n g t o h i s c o n v e r s a t i o n w i t h

J a m e s . L e t u s a s s u m e , t h e n , t h a t

( l b ) S k n o w s t h a t J a m e s h a s a s t a m p c o l l e c t i o n a n d h e k n o w s t h i s o n th e

b a s is o f J a m e s ' d e s c r i p t i o n ( a n d i n v i t a t i o n )

i s t r ue . I a m n o t n o w c o n c e r n e d t o a r g u e t h a t o n e c a n k n o w s o m e t h i n g

o f th i s s o r t in t h i s w a y ; t h e q u e s t i o n i s, r a th e r , w h e t h e r ( 2 b ) m u s t b e t r u e / f

( lb ) i s t rue .

( 2 b ) J a m e s w o u l d n o t h a v e s a i d h e h a d a s t a m p c o l l e c t i o n , d e s c r i b e d

i t i n s uc h de ta i l , a nd i s s ue d a n inv i t a t ion un le s s he ha d a s t a mp

c o l l e c t ion .

I f Ja m e s i s t h e s o r t o f f e l lo w a b o u t w h i c h ( 2 b ) c a n n o t b e t r u l y a ss e r t ed , t h e n

h e is n o t t h e s o r t o f fe l lo w w h o c a n b e t r u s t e d o n s u c h m a t t e r s a s th i s. I f

J a m e s i s th e s o r t o f f el l o w w h o s o m e t i m e s s a y s s u c h t h i n g s a s a j o k e , w h o

w o u l d ( o r m i g h t ) c o n c o c t su c h e l a b o r a t e s t or i e s f o r h i s o w n a m u s e m e n t

( o r w h a t e v er ) , w h o w o u l d ( o r m i g h t ) w h i m s i c a l l y i ss u e a n i n v i t a t i o n o f t hi s

s o r t und e r to t a l ly fa l se p re t e x t s , t he n , de s p i t e the fa c t t ha t he i s (by hypo -

the s i s ) t e l l i ng the t ru th on th i s oc c a s ion , h i s t e s t imony i s ha rd ly the s o r t on

w h i c h o n e c a n re s t a c l a im t o k n o w . I n d e n y i n g ( 2 b ) o n e i s c o n c e d i n g t h a t

J a m e s w o u l d , o r m i g h t , h a v e s a i d w h a t h e d i d w i t h o u t p o s s e s s i n g a s t a m p

c o l l e c t ion , a nd in the l igh t o f th i s c onc e s s ion one c a nn o t g o on to in s i s t t ha t ,

none the le s s , S

k n o w s

he ha s a s t a mp c o l l e c t ion on the ba s i s, s imp ly , o f wha t

J a me s s a id .

I n a r e c e n t ar t ic l e G i l b e r t H a r m a n c o n t r a s t s t w o c a s es ,

t he l o t t e ry case

a n d t he t e s t i mon y case . 2 A l t h o u g h S , s ay , h as o n l y o n e a m o n g t h o u s a n d s o f

t i c ke t s in a lo t t e ry a nd , he nc e , ha s a n e x t re me ly s l e nde r c h a nc e o f w inn ing ,

w e n a t u r a l l y r e j e c t th e i d e a t h a t S c o u l d k n o w t h a t h e w a s g o i n g t o l o s e o n t h e

ba s i s o f a c o r re c t p rob a b i l i t y e s t ima te (we l l ove r 99 .9 ) o f h i s lo s ing . Eve n

i f S c o r r e c t l y p r e d ic t s t h a t h e i s g o i n g t o l o se , w e w o u l d d e n y t h a t h e k n e w h e

wa s g o ing to lo s e i f t he onl y ba s i s he ha d fo r th i s be l i e f wa s the fa c t t h a t h i s

c h a n c e s o f w i n n i n g w e r e s o s l i gh t , s H a r m a n c o m p a r e s t h is c a s e w i t h t h e

s i t u a t io n i n w h i c h w e o f t e n s e e m p r e p a r e d t o s a y t h a t S k n o w s t h a t P w h e n

h e i s t o l d t h a t P i s t h e c as e b y s o m e o t h e r p e r s o n ( t e s t i m o n y c a se ) . A l t h o u g h

p r o b a b i l i t y e s t i m a t e s a r e n o t a l t o g e t h e r a p p r o p r i a t e h e r e , w e d o k n o w t h a t

p e o p l e s o m e t i m e s l ie , so m e t i m e s t h e y a r e h o n e s t l y m i s t ak e n , a n d s o o n .

The re a lwa ys s e e ms to be a c ha nc e tha t wha t a pe r s on t e l l s u s i s no t the c a s e

h o w e v e r s in c e r e o r c r ed i b l e h e m a y a p p e a r , a n d t h e o r d e r o f m a g n i t u d e o f

2 'Knowledge, Inference, and Explanation', in American Philosophical Quarterly July,

1968.

8 Of course S m ay have said ' I kno w I am going to lose' and he may say now, after he has

lost, 'I knew I was going to lose', but these expressions are normally accepted without

epistemological quibbling because the y are taken as little more th an expressions of resig-

nation o r despair. With this use of the verb 'to know ', one can know one is going to

lose and

still

spend a dollar for a ticket and a chance at the prize---a fact about human

beings which is puzzling if they believe they know (in any epistemologically relevant

sense) that they are going to lose.

3

Fred Dretske

t h i s c h a n c e s e e m s t o b e c o m p a r a b l e t o t h e c h a n c e w e m i g h t w i n i n s o m e

a p p r o p r i a t e l o t te r y s i t u a ti o n . W h y , t h e n , a r e w e p r e p a r e d t o s a y t h a t w e

k n o w i n t h e o n e c a s e b u t n o t in th e o t h e r ? H a r m a n h a s s o m e r e v e a l i n g

r e m a r k s t o m a k e a b o u t t h e s e c a s e s, b u t I m e n t i o n t h e m o n l y t o b ri n g o u t

t h e i r r e l e v a n c e t o t h e p r e s e n t d is c u s s i o n . F o r I t h in k t h i s c o n t r a s t s t r e n g t h e n s

t h e v i e w t h a t ( 2 ) i s n o r m a l l y a c c e p t e d a s a n e c e s s a r y c o n s e q u e n c e o f (1 ) ,

t h a t w h e n w e a r e u n w i ll i n g t o e n d o r s e t h e c o r r e s p o n d i n g i n s t a n t i a t i o n o f

( 2 ) w e a r e u n w i l l i n g t o t a l k o f a n y o n e k n o w i n g t h a t P i s th e c a s e o n t h e b a s i s

o f t h e e v id e n c e e x p re s s e d b y R . I n m a n y t e s t i m o n y s i t u a t i o n s w e a r e , I

b e l i e v e , w i l l i n g t o a f f i r m ( 2 ) : th e p e r s o n w o u l d n o t h a v e s a i d i t u n l e s s i t w a s

s o . I n t h e l o t t e r y c a s e, h o w e v e r , t h e c o n n e c t i o n b e t w e e n R a n d P e x p r e s s e d

b y t h i s s u b j u n c t i v e c o n d i t i o n a l f a i ls t o b e r e a li z e d , a n d i t f a il s n o m a t t e r h o w

g r e a t t h e p r o b a b i l i t i e s b e c o m e . A d j u s t i n g t h e w o r d i n g o f (2 ) to s u i t t h e

e x a m p l e i n q u e s t i o n 4 w e h a v e

( 2 c) I f S w e re g o i n g t o w i n t h e l o t t e r y , h is c h a n c e s o f w i n n i n g w o u l d

n o t b e 1 / m ( m b e i n g t h e n u m b e r o f ti c k e t s s o l d) .

W h a t e v e r ( f in i te ) v a l u e w e g i v e t o m , w e k n o w t h i s i s f a ls e s i n c e s o m e o n e

w h o s e c h a n c e s o f w i n n i n g a r e 1 / m will w i n , a n d s i n c e t h e r e i s n o t h i n g s p e c i a l

a b o u t S w h i c h w o u l d r e q u i r e h i m t o h a v e a b e t t e r c h a n c e o f w i n n i n g t h a n

a n y o n e e l s e i n o r d e r t o w i n , w e r e j e c t ( 2 c ) a s f a l s e. H e n c e , w e r e j e c t t h e i d e a

t h a t S c a n k n o w h e i s g o i n g t o l o s e o n t h e b a s i s o f th e f a c t t h a t h i s c h a n c e s o f

l o s i n g a r e ( m - 1 ) / m .

A l v i n G o l d m a n , i n d e v e l o p i n g a c a u s a l a c c o u n t o f k n o w l e d g e , c o n s t r u c t s a

s i t u a t i o n i n w h i c h S i s s a i d to k n o w t h a t a n e a r b y m o u n t a i n ( I w il l c a l l i t M )

e r u p t e d m a n y y e a r s a g o . H e k n o w s t h i s o n t h e b as i s o f t h e p re s e n c e o f

s o l i di f i ed l a v a t h r o u g h o u t t h e c o u n t r y s i d e s u r r o u n d i n g t h e m o u n t a i n . 5

A c c o r d i n g t o G o l d m a n , a n e c e s s a r y c o n d i t i o n f o r S s k n o w i n g t h a t M

e r u p t e d m a n y y e a r s a g o o n t h e b a s i s o f th e p r e s e n t e x i s te n c e a n d d i s t r i b u t i o n

o f t h e la v a i s t h a t t h e r e b e a c a u s a l c o n n e c t i o n b e t w e e n t h e e r u p t i o n o f t h e

m o u n t a i n a n d t h e p r e s e n t e x i st e n c e a n d d i s t r i b u t i o n o f t h e l a v a . I d o n o t

4 The wording o f (2) will sometimes have to b e adjusted to suit the part icular instantiat ion

in question. The chief factors determining this adjustment are the relat ive temporal

locations of R, P and the t ime of utterance and also the causal connections, if any, which

are believed to hold between R and P. The part icu lar wording I have given (2) is most

appropriate when P is some state of affairs antecedent to (or contemporaneous with)

both R and the t ime of utterance. This, of course, is the result of the fact that (2) is

most o ften used when P is som e state o f affairs causally responsible for the present

condit ion R. When P is a future state we might express (2) as: R would not be the case

unless P were going to happen . For exam ple, he would not have registered unless he

were going to vote. I do no t wish to preclude the possibili ty of knowing that something

will

occur on the basis of present evidence by restricting the wording of (2). The

difficulty, of course, is that when P is some future state, the subjunctive relating it to R

generally becomes somewhat questionable. We prefer to say, in our mo re cautious

moods, th at if he were not planningto vote, he w ould not have registered (acknowledging,

thereby, the fact that contingencies may interfere with the execution of his plans).

But in the same cautious mood s we prefer to say, not that we know he is going to vote

(because he registered), but that we kno w he plans or intends to vote.

A Causal Theory of Knowing ,

Journal of Philosophy

Jane 22, 1967, p. 361.

4

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Conclusive Reasons

wish to d ispu te th i s c la im a t the m om en t s ince the v iew I am advanc ing i s even

s t ronger : viz t h a t a n eces s a r y co n d i t io n f o r S t o k n o w t h a t M e r u p t ed o n

this basis is that

(2d) The lava would no t be here , and d is t r ibu ted in th i s man ner , un less

M e r u p t ed

is t rue . (2d) i s a s t ronger c la im than tha t the eru p t ion o f M is causal ly

connected wi th the p resen t ex is tence and d is t r ibu t ion o f the lava . (2d) r e-

qu i res , in add i t ion , th a t M s erup t ion be n ecessary fo r the p resen t s ta te o f

af fa i rs . To i l lus t r a te , cons ider the fo l lowing embe l l i shmen t on G old ma n s

ex am p l e. N o t f a r f r o m M is an o t h e r m o u n t a i n , N . T h e g eo lo g y o f t h e

area i s such tha t a t the po in t in t ime a t which M erup ted someth ing , so to

speak , was boun d to g ive; i f M had no t erup ted , N would have . Fur the r -

more , the locat ion o f N is such tha t i f i t , r a ther th an M, had erup ted , the

presen t d i s t r ibu t ion o f lava would h ave been , in a l l r espects re levan t to S s

tak ing it as a r eason fo r be l iev ing M erup ted , the sam e. In such c i r cum-

s tances Gold ma n s necessary condi t ion i s sa t i sf ied , bu t mine i s no t . (2d) is

f a l se ; it is f a lse tha t the lava wo uld no t be here , a nd d is t r ibu ted in th i s f ash ion ,

un less M had erup ted . Fo r if , con t r ary to hypothes is , M had no t erup ted ,

N would have; leav ing the very same ( r e levan t ) t r aces .

In such c i r cumstances I do no t th ink we cou ld say tha t S knew that M

erup ted on the bas i s o f the p resen t ex is tence and d is t r ibu t ion o f lava . For ,

by hypothes is ,

this

s ta te o f af f a i r s would hav e ob ta ined w hether M erup te d

or no t and , h ence , there i s no th in g ab out th i s s ta te o f af f a i rs which f avo ur s

one hypothes is (M erup ted) over a comp et ing hypothes is (N erup ted) . S

is s t i l l co r r ec t in suppos ing tha t M d id erup t , s t i l l co r r ec t in suppos ing tha t

i t was M s erup t ion which i s causal ly r espons ib le fo r the p resen t ex is tence

an d d i s t r i b u ti o n o f l av a , b u t h e d o es n o t k n o w i t w as M t h a t e r u p t ed - - n o t

u n le s s h e h as s o m e ad d i t i o n a l g r o u n d s w h i ch p r ec lu d e N . I f h e h as s u ch

ad d i t i o na l g r o u n d s , c a ll t h em Q , t h en w e can s ay t h a t h e k n o w s t h a t M

erup ted and he knows th is on the bas i s o f

R and Q

In th i s case , however ,

the cor resp ondin g ins tan t ia t ion o f (2 ) is a l so sa t is f ied : R

and

Q w o u l d n o t

be the case un less M erup ted . As th ings s tand , the mos t tha t S cou ld know,

on the bas i s s imply o f the p resen t ex is tence and d is t r ibu t ion o f lava , i s tha t

either M o r N erup ted

( 2) p e r m i t s u s t o s ay th i s m u ch , an d n o m o r e , ab o u t

w h a t can b e k n o w n o n t h e b as i s o f l av a fl o w.

T h e ca s e b eco m es ev en c lea r e r i f w e ex p l o it an o t h e r o f H a r m an s ex am p l es .6

Har o ld has a t i cket in a lo t tery . The od ds agains t h i s winn ing are 10 ,000 to 1 .

T h e p r i ze , c a l l i t an X , i s s o m e t h i n g t h a t H a r o l d d o es n o t n o w h av e n o r

co u l d h e r ea s o n ab l y ex p ec t t o o b t a i n o n e b y m ean s o t h e r t h an w i n n i n g t h e

l o t te r y . E n t e r a p h i lan t h r o p i c g en t l em an , R o ck a f o r d , w h o d ec i d es t o g i ve

Ha ro ld an X i f ( as seems l ike ly ) he shou ld f a i l to win on e in the lo t tery .

T h i n g s 3 o a s o n e w o u l d ex p ec t ; H a r o l d h o l d s a l o si n g t i ck e t . R o ck a f o r d

k eep s hi s w o r d a n d g i v es H ar o l d a n X . S , f am i l i a r w i t h t h e ab o v e c i r cu m -

s t ances b u t u n aw ar e o f w h e t h e r H a r o l d w o n o r l o s t i n t h e l o t te r y , f in d s

o In Knowledge, Inference, and Explanation , pp. 168-9. I have adapted the example

somewhat.

Fred D re tske

Haro ld with his newly acquired X. S infers that Haro ld received his X from

Roekafo rd. He concludes this because he knows that the only other way

Harold might have acquired an X is by winning the lottery and the odds

g inst that happening are enormous. The following conditions are satis-

fied: (a) Harold received his X from Rockaford; (b) S believes that Harold

received his X from Rockaford; (c) S is warranted in believing this since the

chances of his having received it in any other way are negligible; (d) Rocka-

ford s generous gift of an X to Haro ld is the (causal ?) explanation of Harol d s

present possession of an X; and, finally (e) S correctly reconstructs (to use

Gold man s language) the causal chain o f events which brough t ab out

Harold s possession of an X. Yet, why does it seem clear (at least to myself---

and apparently to Harman) and S does n o t know that Rockaford gave

Haro ld his X. Because

(2e) Harold would not have an X unless Rockaford gave him one

is plainly false.7 If Rock afo rd had not given him an X, it would have been

because Harold already possessed one as a winner in the lottery. Hence,

Harold would possess an X even if Rockaford had not given him one.

It is not true that R would not be the case

unless

P; hence, not true that S

knows t hat P on the basis of R. s

(2), therefore, expresses something stronger than a causal relationship

between R and P. It should be pointed out, however, that it expresses

something which is, in certain important respects, weaker than a universal

association between states or conditions similar to R and states or condit ions

similar to P. When R and P are expressions which stand for particular

conditions or states of affairs, as will often be the case when we know one

thing on the basis of something else, (2) expresses a connection between more

d e t e r m i n a t e

states of affairs than those described by talking about states

similar to R and P. If someone remarks, mid-way throug h a poker hand,

that if his neighbour had not folded (dropped from the game) he (the speaker)

would have been dealt a royal flush, he is obviously not maintaining that

whenever his neighbour remains in the game, he (the speaker) is rewarded

with a royal flush. Rather , he is talking about

this

hand (already holding

four cards to the royal flush), this part icular distribution of cards in the

remainder of the deck, this part icular seating arrangement, and so on.

He is not saying that his neig hbou r s remaining in the game is, quite generally,

sufficient for his receipt of a royal flush. Rather , he is saying that in the

7 There is a way of reading (2e) which makes it sound true--viz if we illicitly smuggle in

the fact that Harold

has lost

the lottery. That is, (2e ) Harold, having lost the lottery,

would not have an X unless Rockaford had given him one , is true. But this version of

(2) makes R, the reason S has for believing Rockaford gave him an X, not only Harold s

possession of an X but also

his having lost th e lottery.

This, by hypothesis, is not part

of S s reason; hence, not properly included in (2e). (2e) must be read in something like

the followingfashion: Harold would not have an X, whatever the outcome of the lottery,

unless Rockaford had given him one. With this reading it is clearly false.

s It is difficult to say whether this is a counter-example to Goldman s analysis. I think it

satisfies all the conditions he catalogues as sufficient for knowledge, but this depends on

how strictly Goldman intends the condition that S must be warranted in inferring that

P is the case from R.

6

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Conclus ive Reasons

part icular c ircumstances which in fa ct prevai led on this occasion,

circumstances

which include such things as car d distribution, arrange ment of players, etc.,

an occurrence of the first sort (neighbour remains in game) will invariably

be followed by one of the second sort (his receipt of a royal flush). One

cannot falsify his claim by showing that he would not have received a royal

flush, despite his neighbour's remaining in the game, if the card distribution

in the deck had been different from what it in fact was. Fo r his claim was a

claim about the inevitable sequence of events with that dis tr ibut ion of cards .

Statements such as (2), then, even when R and P are expressions for par-

ticular states of affairs, express a general uniformity, but this general uni-

formity is not that whenever a state similar to R is the case, then a state

similar to P will also be (or have been) the case. The uni form ity in question

concerns the relationship between states similar to R and P under a f i xed

set of c ircumstances . Whenever (a state such as) R in c ircumstances C then

(a state such as) P where the circumstances C are defined in terms of those

circumstances which actually prevail on the occasion of R and P. But does

C include

all

the circumstances that prevail on the occasion in question or

only some of these? Clearly not all the circumstances since this would

trivialize every subjunctive condi tion al of this sort. Even if we restrict C

to only those circumstances logically independent of R and P we still obtain

a trivialization. For, to use Goldma n's mountai n example (as embellished),

C would still include the fact that N did not erupt (since this is logically

independent o f both R and P), and this is obviously one of the circumstances

not held fixed when we say that the lava would not be here unless M erupted.

For in asserting his subjunctive we mean to be asserting something which

would be

f a l s e

in the situation described (N would have erupted if M had

not) whereas if we hold this circumstance (N did not erupt) fixed, the uni-

formity between the presence of lava and M's eruption would

hold.

I think that our examples, not to mention an extensive literature on the

subject, 9 point the way to a prop er interpretation of C. The circumstances

which are assumed constant, which are tacitly held fixed, in conditionals

such as (2), are those circumstances prevailing on the occasion in question

(the occasion on and between which the particular states R and P obtain)

which are logically and causally independent of the state of affairs expressed

9 I am not proposing a solution to the problem to which Nelson Goodman Fact, Fiction

and Forecast,

Chapter I), Roderick Chisholm ('The Contrary-to-Fact Conditional,

Mind, 55, 1946) and others addressed themselves in trying to specify the 'relevant con-

ditions' associated with counterfactuals. I shall use the notion of 'causality' in my

treatment, a device which both Goodman and Chisholm would regard as question-

begging. I am not, however, attempting to offer an extensionalist analysis of the sub-

junctive conditional; I am merely trying to get clear in what way such conditionals are

stronger than the statement of a causal relationship between R and P and yet (in one

sense) weaker than a statement of the universal association between states similar to

Rand P.

Fred retske

by p.10 Wh en we have a s ta te ment in the sub junct ive which (un l ike (2 ))

i s counter f ac tual ( the an teceden t g ives express ion to a s ta te o f af f a i r s which

does o r d id no t ob ta in ) , then C inc ludes those c ir cumstances p revai l ing on the

occas ion which are log ica lly and causal ly independe nt o f the s ta te o f af f a ir s

(o r lack o f such s ta te) expressed by the antecedent of the condi t ional . In

o u r p o k e r g am e , f o r ex am p l e , w e can s ay t h a t S s s t a t em en t ( I w o u ld h av e

got a royal f lush i f my n eighbou r had s tayed in the game) f i x e s tha t se t o f

c i r cumstances which are log ica l ly and causal ly indepen dent o f h i s ne ighb our s

s tay ing in the gam e ( i .e . the an teceden t s ince the s ta tement i s c ounter f ac tual ) .

Hence , i f there i s ano ther p lay er in the game (whose p resence o r absence

af fects the cards deal t to S) who w ould h ave d ropp ed i f S s ne ighbo ur had

not d ro pped , then th i s per son s r ema in ing in the game i s not held f ixed, not

inc luded in C, be cause i t i s causal ly connected to the s ta te o f af f a ir s expressed

by the an teceden t in S s s ta tement . Therefore , we can show S s s ta teme nt

to be f a l se i f we can show that such a c i r cumstance p revai led , and i t is a long

these l ines tha t one would sure ly argue in a t tempt ing to show S tha t he

was wrong , wrong in say ing tha t he would have r eceived a royal f lush i f h i s

neighbour had s tayed in the game.

On the o ther hand , one cann ot show tha t S s s ta tement i s f a l se by showing

that , were the cards d i f f eren t ly ar r ange d in the r ema inder o f the deck , he

would no t have r eceived h is royal f lush ; fo r the ar r angement o f cards in the

remain der o f the deck (un like the p resence o r absence o f our o ther p layer )

i s (p resumably) indepe ndent o f S s ne ighbou r s de par tu re f rom the game.

Hence , i t i s one o f the condi t ions held f ixed , inc luded in C, b y S s s ta tement ,

and we are no t a l lowed to cons ider a l te r a t ions in i t in assess ing the genera l

impl ica t ion o f S s s ta tement .

Or cons ider our o r ig inal therm ome ter example . Recal l , the s ta tement in

ques t ion was : The th ermo me ter would n o t have r ead 98 .6 un less the ch i ld s

t em p er a t u r e w as n o r m a l . Su p p o s e s o m eo n e r e s p o n ds , O h , i t w o u l d h av e

( o r m i g h t h av e) i f t h e t h e r m o m et e r w as b r o k en . I t is i m p o r t an t t o u n d e r -

s t an d t h a t o n e can g r an t t h e t r u t h o f t h is r e s p o n s e w i t h o u t ab an d o n i n g t h e

or ig inal asser t ion ; fo r the o r ig inal asser t ion had , as i t s genera l impl ica t ion ,

not a s ta te ment express ing a un i fo rm re la t ionsh ip between s ta tes o f af f a ir s

s i m il a r t o t h e ch i l d s t em p er a t u r e ( n o r m a l b o d y t em p er a t u r e ) an d s t at e s o f

af f a i r s s imi lar to the thermometer r ead ing ( a r ead ing of 98.6 , but , r a ther , a

un i fo rmi ty between such s ta tes

under a f ix ed set o f c ircumstances.

A n d , i f

10 This character izat ion of the c ircumstances C has interest ing and, I bel ieve, s ignif icant

repercussions for subjunct ives having the form of (2) in which R expresses some present

(or past) s ta te of affa irs and P expresses some future s ta te of affa irs . Alt hou gh I lack the

space to discuss the point here , I bel ieve an important asymmetry is generated by a shif t

in the re la t ive tempo ral locat ions of R a nd P. I a lso believe, however , tha t th is asym -

metry is fa i thful ly ref lected in the difference between knowing what

will

h a p p e n o n t h e

bas i s o f p re sen t da ta and knowing wha t did happen on the bas i s o f p re sen t da ta . In

other words, I feel that an asymmetry in (2) , ar is ing from a shif t in the re la t ive tem-

poral locat ions of R and P, helps one to understand the difference we al l feel between

knowing , on the one hand , wha t d id happen o r i s happen ing , and , on the o the r hand ,

what wil l happen.

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Conclusive Reasons

I am fight, this f ixed set of circums tances inclu des the actual s tate of the

thermometer

(defec tive or accura te ) ; i t i s one o f those c i rcumstances preva i l ing

on the occas ion in quest ion which is causa l ly and logica l ly indep enden t of

the chi ld s tempera ture . Hence , th is c i rcumstance canno t be a l lowed to

vary as i t i s in the above response by the words i f the the r mom eter was

broken . To de te rmin e the t ru th of the or ig ina l asse r t ion we must sup pose

tha t the the rm ome ter i s accura te (or defec t ive) whatever the actua l condition is.

I f , the re fore, the the rmom eter was no t bro ken o r o therwise defec tive on th a t

occas ion, then the suggest ion tha t i t would (or might) have read the same

despite a feverish child if i t were broken or defective is, a lthough quite true,

i r re levant to the t ru t h o f the s ta tement : I t would n ot have read 98.6 unless

the child s tempe ra ture was n ormal .

One f ina l imp or tan t fea ture of (2). I have said tha t , genera l ly speaking,

the p lace-holders R and P represent express ions des igna t ing

specific

states

of affairs or condit ions. Wh en this is so, (2) stil l has a general implicatio n,

but the genera l impl ica t ion, express ing a uniform re la t ionship be tween

states of affairs similar to R and P, has its scope restricted to s i tua t ions in

which the circums tances C (as specif ied abov e) obtain. Since we are talking

about specif ic states of affairs in most instantiations of (2) , i t becomes

extremely imp or tan t to observe the sor ts of re fe r ring express ions embodie d

within bot h R and P . Fo r example , when I say , Joh n would not have sa id

i t was rain ing unless i t was ra in ing I am ta lk ing abou t

John

a nd a bou t a

particular utterance of his. Someone else might have sa id th is wi thout i t s

be ing t rue ; Jo hn m ay have sa id something else withou t i t s be ing t rue . Non e-

theless,

John

would n o t ha ve sa id

it was raining

unless i t was . An incurable

l ia r abou t most th ings, John has a pa thologica l devot io n to accuracy on

mat te r s concerning the wea ther . In such a case, a l though John is, admit tedly ,

a most unre l iable informant on most mat te r s , we can say tha t he would

not have sa id i t was ra in ing unless i t was so . This i s only to say tha t the

re fe rr ing express ions to be foun d in R and P help to define the scope o f

the impl ied genera l iza t ion. Reca l l, the impl ied genera l iza t ion was about

states of affairs similar to ( the par t icula r s ta tes) R and P . S imila r in wha t

respec t? The sor t of re fe r r ing express ions to be foun d wi thin R and P

he lp us to answer th is ques t ion. In the case of Joh n above , the genera l

impl ica t ion involved, not

a person s say ing something

(under c i rcumstances

C), not John s saying something (under c i rcumstances C) , but Joh n s saying

something about the wea ther (under c i rcumstances C) .

2. The Possibi l i ty of Mistake: The C onnection Between

(2)

and

(3).

Takin g a cue f rom the fac t tha t (2) expresses some form of necessa ry re -

la t ionship be tween R and P , I have ( in my open ing remarks) expressed (2) as :

Gi ven R, -,~ ( ) ,-~ P (or, altern ative ly, , ,~ ( ) ( R . --~ P)). I th ink th e full

justif ication for expressing (2) in this fashion lies in the fact that (2) and (3)

a re contradic tor ies , and s ince (3) may be rendered as :

(3) Given R, () ~ P (or , a lternatively , ( )( R . ,-~ P)

(2) ma y be represented as Giv en R, ,,~ () ,,~ P .

Fred Dre t ske

To see tha t th i s i s so , i t should be not i ced tha t in denying the connec t ion

be t w e e n R a nd P e xp r e s s e d by ( 2 ) w e do no t c om m i t ou r s e l ve s t o a ny t h i ng

as s t rong as :

(4) R would be the case even though not -P were the case .

(4) is the contrary of (2) , not i t s cont rad ic tory , s ince both (2) and (4) m ay

turn o ut fa l se, n Fo r example , suppos e S as se r ts ,

(2g) I would h ave won the lo t t e ry i f I had bo ugh t two t i cke t s (ins tead

of only one) .

W e m a y de ny t he t r u t h o f th i s c on t e n t i on w i t hou t c om m i t t i ng ou r s e lve s t o

t he t r u t h o f

( 4g ) Y ou w ou l d ha v e l o st e ve n i f you ha d boug h t t w o t i c ket s .

Al l tha t i s in tended in denying (2g) is tha t the pu rchase of two t i cke t s i s con -

nec ted wi th winning in the a l l eged manne r , tha t the purcha se of two t i cke t s

w ou l d ha ve a s s u r e d h i m o f w i nn ing . I t s f a il i ng t o be c onne c t e d i n the

ma nne r a l l eged i s , however , qui t e con s i s t ent wi th his winning with two t i cke t s .

W ha t w e c om m i t ou r s e l ve s t o i n de ny i ng ( 2g ) i s :

(3g) You

might

have los t even wi th two t i cke t s .

(3g) asserts what (2g) denies ; viz. tha t even wi th two t i cke t s i t i s still a m a t t e r

of chance , the poss ib i l i ty of los ing i s not e l i m i na t e d by ho l d i ng t w o t i c ke t s

ins tead of one .

A s a m a t t e r o f c om m o n p r a c t ic e , o f c ou rs e , w e o f t e n e m p l oy s om e t h i ng

s imi la r to (4) in denying (2) . Thi s i s und ers tand able e nou gh s ince the t ru th

o f ( 4~ does enta i l the fa ls i ty of (2) . The po in t I am dr iv ing a t, howev er , is tha t

we need not a f f i rm anyth ing as s t rong as (4) in denying (2) ; a l l we a re requi red

to a f f i rm i s tha t R an d no t -P m i gh t bo t h be t he c a s e o r t ha t , e ve n t hough R

is given, P

might not

be the case . Th a t i s to s ay , the prope r expres s ion for

the neg a t ion o f (2) i s (3) ; and i f we und ers tand (3) as a f f i rming Giv en R ,

( ) -~ P (a l t e rna t ive ly ( ) ( R . ,-~ P) ) , then we a re jus t i f i ed in represe nt ing

(2) as Giv en R , N ( ) ~ p (a l t e rna t ive ly , -,~ ( ) (R . ,-~ P) ) . I f som eon e

s a ys, J a m e s w ou l d no t ha ve c om e w i t hou t a n i nv i t a t i on , w e c a n de ny t h i s

w i t hou t s uppos i ng t ha t J a m e s w ou l d ha ve c om e w i t hou t a n i nv i t a t i on .

F o r s uppos e w e kno w t ha t i f J a m e s h a d no t r e c e ive d a n i nv i ta t i on , he w ou l d

have f l ipped a coin to dec ide whe ther to go or not . In such a case , i t i s no t

t r ue t ha t he w ou l d no t ha ve c om e w i t hou t a n i nv i t a t i on , bu t ne i t he r i s i t

t r ue t ha t he w ou l d ha ve c om e w i t hou t a n i nv i t a ti on . T he f a c t i s t ha t

he

might have come ( de pe nd i ng on t he ou t c om e o f t he t o ss ) w i t hou t a n i nv i t a t ion .

B e f o r e p r oc e e d i ng t he r e i s a n i m por t a n t a m b i gu i t y w h i c h m us t be e l i m i n -

a t e d . T he r e is a u s e o f t he w or d m i gh t ( a nd r e la t e d m o da l t e r m s ) w h i c h

gives expres s ion to the speaker s ep i s t emic s t a t e in re la t ion to some s i tua t ion .

I t is a u s e o f the w or d m i gh t w h i c h i s na t u r a l l y f o ll ow e d by a pa r e n t he t i c a l

f o r al l I kno w . F o r e xa m pl e , i n sa y i ng , H e m i gh t w i n t he el e c t ion t he

11 A point which Go odm an acknowledges in a footn ote: Literally a semifactual and the

corresponding counterfactual are not contradictories hut contraries, and both may be

false. Fa ct Fiction and Forecast p. 32, note 2.

10

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Conclusive Reasons

s pe a ke r is m os t na t u r a l l y unde r s t ood a s e xp r es s ing t he f a c t t ha t he doe s no t

knoW whether he wi l l win the e lec t ion or not , tha t he has n o (or the re a re no)

very convinc ing groun ds for supp os ing he wil l lose . Thi s use of the word ca n

proper ly be deployed even when the s t a t e of a f fa i r s in ques t ion

is physically

o r logically i m pos s i b le . S , f o r i n s ta nc e , m a y c onc e de t he p re m i s e s o f ou r

va l id a rgum ent bu t , none the les s , igno rant o f it s va l id i ty , ins is t tha t the con-

c lus ion might ( for a l l he knows) be fa l se even though the premises a re t rue .

C on t r a s t e d w i t h t h is e p i s t em i c u s e o f the m oda l t e r m s i s w ha t w e m i gh t

cal l an objective s e nse o f t he se t e r m s , a s ens e o f the t e r m c ou l d ( f o r e xa m pl e )

in which i f R enta i l s P then , indepen dent of wha t S know s abo ut the logica l

re la t ionship be tween R a nd P , i t is fa l se to s ay tha t R a nd not -P co uld (or

m i gh t ) bo t h be t he c a se . M or e o ve r , i f w e a c c e p t t he r es u lt s o f m o de r n

phys ics, then in th i s objec t ive sense of the t e rm S s s t a t emen t tha t the re a re

objec t s which can t rave l fas t e r than the speed of l ight is fa lse , and i t i s fa lse

even

though for al l he knows

the re a re objec t s which can . In th i s objec tive

sense one i s making a remark about the va r ious poss ib i l i t i e s for the occur -

rence , or jo in t occur rence , of event s or the co-exi s t ence of s t a t es of a f fa i r s ,

and in th i s s ense ignorance of wha t i s the case i s no g uaran tee th a t o ne s

s t a t e m e n t s a bou t w ha t might o r could be the case a re t rue . The poss ib i l it i e s

m us t a c t ual l y be a s one al le ges . W he n S ( know i ng t ha t J a m e s ha d a n i n -

v i t a t ion to come) as se r t s tha t J am es , be ing the so r t of fe llow he i s, might

( e ve n ) ha ve c om e w i t hou t a n i nv i t a t i on , he i s m a k i ng a r e m a r k

about James

a nd w ha t J a m e s is i ncl ine d t o do o r c a pa b l e o f do i ng . H e i s obv i ous l y no t

r e g is t er i ng s om e f a c t a bou t h i s i gno r a nc e o f w he t he r o r no t J a m e s pos s e s se s

an invi t a t ion .

T he m o da l t e r m a ppe a r i ng i n ( 3 ) i s m e a n t t o be unde r s t oo d i n the ob j e c t ive

sense . (3) i s me an t to be a s t a t em ent ab ou t the possib i l it i e s for the jo in t

r e a li z a ti on o f t w o s t at e s o f af f a ir s ( R a nd no t - P ) i nde pe nde n t o f w ha t t he

s pe a ke r ha ppe n s t o k now a bou t t he a c t ua l r e a li z a t ion o f P ( R be i ng gi ve n) .

D r a w i ng f r om ou r d i s c us s i on i n t he p r e c e d i ng s e c t i on , w e c a n s a y t ha t i f

(2) i s t rue , i f R w ould not be the case unles s P were the case , then

in these

circumstances

(specif ied earl ier) P is a s tate o f affairs whic h is necessar y to

the rea l i za t ion o f R . Hence , in these c i rcums tances i t i s fa l se to s ay tha t

R a nd no t - P m i gh t bo t h be t he c as e o r t ha t , g i ven R , no t - P m i gh t be t he c a se ,

and i t i s fa l se whe ther or no t any one apprec ia te s the fac t tha t i t i s fa lse .

W e ha ve he r e a m o r e o r l e s s

particularized

impossibi l i ty; (3) , as wel l as (2) ,

i s t i ed to the c i rcums tances , C , spec i fi ed ea r l ie r . No thin g e l se but (a s t a t e

such as ) P could h ave bro ugh t ab ou t (a s t a t e such as ) R in these circumstances.

O f t e n , o f c ou r s e , ou r s t a t e m e n t s a bou t w ha t c ou l d be t he c a s e , a bou t w ha t i s

poss ib le , a re broad er in s cope . The y do not res t r i c t themse lves to the

par t i cu la r s e t of c i rcums tances preva i l ing on some spec i f ic occas ion . The y

are s t a t ements to the e f fec t tha t , w ha tever the c i rcum s tances on th i s occas io n

happened to be , the re a re (none the les s ) c i rcums tances in which a s t a t e

re levant ly s imi la r to R i s , or migh t eas ily be , brou ght a bo ut wi th out a s t a t e

r e l e va n tl y s i m i la r to P . S m a y a dm i t , f o r e xa m pl e , t ha t t he t he r m om e t e r

w ou l d no t ha ve r e a d 98 . 6 un l es s t he c h il d s t e m pe r a t u r e w a s no r m a l - - he nc e ,

11

F r e d D r e t s k e

concede tha t i t would be fa lse to say tha t in these c i rcumstances (g iven the

therm omet er reading) the chi ld might (none the less) have a fever . Ye t , he

may go on to ins is t tha t one can ge t a no r m a l r e a d ing on a t he r m om e te r

wi th a feverish chi ld . One can do so when one has a defec t ive the rmom eter ,

when the chi ld is sucking an ice cube , and so on. Th a t i s , one can have

R wi thout P in

o the r

circumsta nces. Thes e general ' possibil i t ies are ,

however , qui te consis tent wi th the 'pa r t icula rized imposs ib i l i tie s expressed

by (3) . Mo st genu ine imposs ib i li t ies can be made poss ib le by enla rging the

f rame of re fe rence , by re laxing the condi t ions tac i t ly taken as f ixed in the

or ig ina l s ta tement o f imposs ib il i ty . I can ' t swim the Engl ish Channe l ;

th is despi te the fac t tha t I co u ld / f I had t ra ined s ince a boy, been endow ed

with the requis i te endu rance , e tc .

I f I may sum mar ize the a rgument u p to th is point in prepara t ion fo r the

fol lowing sec tion: (1) enta i ls (2), i f S knows tha t P , and he knows th is on the

basis (simply) of R, then R would not be the case unless P were the case.

Fur thermore , (2) g ives express ion to a c6nnec t ion be tween R and P which

permits us to say tha t when R is g iven, in the k ind o f ci rcumstances which

ac tua l ly preva i led on the o ccas ion in ques t ion , the poss ib i l i ty of not -P is

e l imina ted . The sense of the word 'poss ib le ' tha t i s opera t ive here i s, I

submit , the s a m e sense of th is word tha t i s opera t ing in our s t ronges t s ta te -

ments abou t wha t i s physica l ly poss ib le; the d i f ference be tween the poss ib i l i ty

expressed in (3) and other , apparent ly s t ronger , s ta tements of wha t i s poss ib le

and impossible is simply a shif t in the set of circumsta nces which is take n as

f ixed. The imposs ib i l ity expressed by (3) is an imposs ib i l i ty re la t ive to tho se

circumstances, C, held f ixed in (2) , and i t is this fact which makes (3) the

contradic tory of (2) and, hence , which makes i t s nega t ion a logica l conse-

quence of (1) .

3 . C onc lus i v e Re aso ns

Let us ca l l R a conc lus ive reason for P i f and only i f R would not be th e

case unless P were th e case. 12 This make s log ically conclusiv e reaso ns

(LCR ) a subclass of conc lus ive reasons . Conc lus ive reasons depend,

s imply , on the t ru th of (2) ; logica l ly conc lus ive reasons require tha t the

t ru th of (2) be demonst rable o n pure ly logical and def in i t iona l grounds .

Wh en the condi t iona l i s t rue , but n ot logica l ly t rue , we can speak of the

conc lus ive reasons as be ing e m p i r i c a l l y c onc lu s i v e (ECR) .

Of c ou rse , R m a y be a conc lus ive reason for be l ieving P wi thout anyone

believing P, much less having R as their reason for believing. I shall say,

the re fore , tha t S has conclusive reasons R, for be l ieving P i f and only i f :

(A) R is a conclusive reaso n for P ( i .e . (2) is true) ,

(B) S be l ieves , wi thout doubt , r ese rva t ion , or ques t ion , tha t P i s the

case and he be l ieves th is on the bas is of R ,

12 Recal l footnote 5 concerning the particular w ording of (2); I intend those remarks to

apply to this definition of 'conclusive reasons'.

12

8/11/2019 dretske 1971

7/11

Conc lus ive Reasons

( (2 ) ( i ) S kn ow s t ha t R i s t he case o r

( ii ) R i s s o m e e x p e r i m e n t a l s t a te o f S ( a b o u t w h i c h i t m a y n o t

m a k e s e n se to s u p p o s e t h a t S k n o w s t h a t R i s t h e c a s e ; a t

l e a s t i t n o l o n g e r m a k e s m u c h s e n se t o a s k h o w h e k n o w s ) .

W i t h o n l y m i n o r e m b e l l i s h m e n t s , t o b e m e n t i o n e d i n a m o m e n t , I b e li e v e

t h a t S ' s h a v i n g c o n c l u s i v e r e a s o n s f o r b e l i e v i n g P i s both a n e c e s s a r y a n d a

s u ff ic ie n t c o n d i t i o n f o r hi s k n o w i n g t h a t P i s t h e ca s e . T h e a p p e a r a n c e o f

t h e w o r d ' k n o w ' i n t h is c h a r a c t e r i z a t i o n ( i n ( Ci )) d o e s n o t r e n d e r i t c i r c u l a r

a s a c h a r a c t e r i z a t i o n o f k n o w l e d g e s i n c e it c a n b e e l i m i n a t e d b y a r e c u r s i v e

a p p l i c a t i o n o f t h e t h r e e c o n d i t i o n s u n t i l ( C i i) i s r e a c h e d .

I f S h a s c o n c l u s i v e r e a s o n s f o r b e l i e v i n g P , t h e n i t is f a l s e t o s a y t h a t ,

g i ve n t h e s e g r o u n d s f o r b e li e f, a n d t h e c i r c u m s t a n c e s i n w h i c h t h e s e g r o u n d s

s e r v e d a s t h e b a s i s f o r h i s b e l i e f, S m i g h t b e m i s t a k e n a b o u t P . H a v i n g c o n -

c l u s iv e r e a s o n s , a s I h a v e j u s t d e f i n e d i t , n o t o n l y i m p l i e s t h a t P i s t h e c a s e ,

i t n o t o n l y i m p l i e s t h a t S b e l ie v e s t h a t P i s t h e c a s e , b u t i t a l s o i m p l i e s t h a t ,

i n t h e c i r c u m s t a n c e s i n w h i c h h e c a m e t o b e l i e v e t h a t P , h i s b a s i s f o r b e -

l i e vi n g t h a t P w a s s u f f ic i e n t ly s e c u r e t o 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 h is b e i n g

m i s t a k e n a b o u t P . T h i s g o es a l o n g w a y t o w a r d c a p t u r i n g e v e r y t h i n g t h a t

p h i l o s o p h e r s h a v e tr a d i t i o n a l l y r e q u i r e d o f k n o w l e d g e . I n d e e d , i n c e r t a i n

r e s pe c ts it g o e s b e y o n d i t i n r e q u i r i n g a s t r o n g e r c o n n e c t o n b e t w e e n o n e ' s

r e a s o n s o r g r o u n d s a n d w h a t o n e b e l i ev e s ( o n t h e b a s i s o f th e s e r e a s o n s o r

g r o u n d s ) t h a n h a s n o r m a l l y b e e n d e m a n d e d b y t h o s e w i sh i n g t o p r e s e r v e o u r

o r d i n a r y k n o w l e d g e c l a i m s f r o m s c e p t i c a l c r i t i c i sm , a S i n c e , h o w e v e r , I

h a v e a l r e a d y a r g u e d f o r t h e n e c e s s i t y o f ( A ) , f o r R ' s b e i n g a c o n c l u s i v e

r e a s o n fo r P , I s h a l l c o n c e n t r a t e o n t h e q u e s t i o n o f w h e t h e r o r n o t S ' s h a v i n g

a c o n c l u s i v e r e a s o n f o r b e l i e v i n g P i s s u f f ic i e n t f o r h i s k n o w i n g t h a t P .

13 It is this stronger conn ection which blocks the sort o f counterexample which can be

generated to justified-true-belief analyses of knowledge. Gett ier 's (and Lehrer 's)

examples, for instance, are directed at those analyses which construe knowledge in

terms of a degree of justification which is compatible with being justified in believing

something false (both G ett ier and Leh rer mention this feature at the beginning of their

discussion). The counterexamples are then constructed by allowing S to believe that P

(which is false)

with the appropriate degree o f justification

let t ing P entail Q (which is

true), and let t ing S believe that Q on the basis of i ts logical relat ionship to P. We have,

then, a case where S truly believes that Q with t he appropriate degree o f justification

(this degree of justification is al legedly preserved through the en tailment between P and

Q), but a case where S does not know that Q (since his means of arriving as i t were so

clearly defective). On the present analysis, of course, the required connection between

S's evidence and P is strong enough to preclude P's being false. One cannot have con-

clusive reasons for believing something which is false. Hence, this sort of counter-

example cannot be generated. Part o f the motivation for the present analysis is the

conviction (supported by Gett ier-l ike examples) that knowledge, if i t embod ies an evi-

dential relat ion at al l , must embody a strong enough one to el iminate the possibility

of mistake. See Edmu nd Gett ier 's 'Is Justified True Belief Know ledge? ' Analysis

23.6, June 1963 and Keith Lehrer, 'Knowledge, Truth and Evidence',

Analysis

25.5,

April 1965. I should also mention here that these same sorts of considerations seemed

to mo ve Brian Skyrms tow ard a similar analysis; see especially pp. 385-86 in his 'T he

Explication of X Knows That P ' The Journal of Philosophy June 22, 1967.

2

13

Fred Dretske

Severa l p re l iminary po in ts mus t be ment ioned br ief ly . I t may be thought

that in argu ing fo r the imposs ib i l i ty o f mis take as a necessary condi t ion fo r

knowing tha t P I have been was t ing my t ime. I t ma y be thoug ht tha t i f S

k n o w s t h a t

P, then P cannot be f a l se s ince S s knowing tha t P en ta i l s P ;

hence, S cannot be mis taken in be l iev ing tha t P . In answer to th is ob jec t ion

i t shou ld be po in ted o u t tha t the imposs ib i l i ty o f mis take which I have been

talking ab out is an impossibil i ty which ar ises in vir tue of a special connection

between S s r easons , R, and w hat he conseq uen t ly bel ieves, P. I t is no t the

t r iv ia l imposs ib i l i ty o f be ing wrong about someth ing which (by hypothes is )

you know. Wh en ph i losopher s concern themselves wi th the poss ib i li ty o f

mis take in pu ta t ive cases o f knowledge, they are no t c oncern ed wi th the

poss ib i l i ty o f mis take which i s t r iv ia l ly avo idab le by say ing tha t / fyou do

k n o w t h a t P , t h en y o u can n o t b e m i s tak en ab o u t P . T h ey a r e con ce r n ed ,

r a ther , w i th tha t poss ib i l ity as i t ex is t s in r e la t ion to one s ev idence o r g rounds

for be l iev ing P , an d that is the possibil i ty with which (2) is concerned.

T h e p o i n t m ay b e p u t i n an o t h e r w ay. B o t h

I . R would not be the case unless P were the case

R is the case

an d

II. R ~ P (when it is not t rue tha t R would no t be the case un less P)

cons t i tu te conclus ive g rounds , log ica l ly conclus ive g rounds , fo r be l iev ing P .

Nei ther se t o f premises would be t rue un less P were t rue , a nd th i s f ac t is in

bo th cases demons t r ab le on pure ly log ica l and def in i t ional g rounds . But the

signif icant dif ference between I a nd I I is tha t in I , but not in I I , the second

premise alone tu rns ou t to be a conclusive r eason (ECR) . I f we were search ing

for conclus ive r easons to be l ieve P , then in the second case we would r equ i r e

as our r easons both premises and th i s would r equ i r e tha t we knew that bo th

premises were true (see clause (C) in having conclusive reasons) . In case I ,

however , the second premise a lone i s a conclus ive r eason and , hence , to have

conclus ive r easons i t i s r equ i r ed only tha t we kno w that R is the case. W e

need no t ( as in case II ) know tha t the f i r s t p remise is t rue . A l l tha t i s r e-

qu i r ed in case I fo r R a lone to be a conclus ive r eason is tha t the f i r s t p remise

be t rue ; there i s no th ing th a t r equ i r es S to know that the f i rs t p remise i s t rue

in o rder to have R as h i s conclus ive r eason fo r be l iev ing P . For i f the f i r st

premis e is t rue ( regardless of whe the r S knows i t is t rue or no t) then (3) is

f a l se ; hence , the poss ib i li ty o f S s be ing mis taken abou t P has bee n success -

fu l ly avo ide d- -a nd i t has been success ful ly avo ided whether or not S knows

it has been avoided.

In speak ing o f conclus ive r easons I d o n o t wish to sugges t tha t in hav ing R

as a conclus ive r eason S mus t be in a pos i t ion to give R as his reason. R

ma y s imply be a cer ta in exper ience which S has undergone a nd , hav ing under -

gone th i s exper ience , come to the bel ief tha t P was the case on the bas i s o f

(as a result of) this exper ience. He m ay f ind i t dif ficult , or impossible, to

g ive verbal express ion to R. He ma y have fo rgo t ten R. Or R may cons ist

14

8/11/2019 dretske 1971

8/11

Conclusive Reasons

i n s o m e t h i n g s l o o k i n g a p a r t i c u l a r w a y t o h i m w h i c h h e f i n d s di f fi c u lt t o

d e s cr ib e . S ti ll , i f t h e w a y t h e t h i n g l o o k s t o S i s s u c h t h a t i t w o u l d n o t l o o k

t h a t w a y u n l es s i t h a d t h e p r o p e r t y Q , t h e n i ts l o o k i n g t h a t w a y t o S is a

c o n c l u si v e r e a s o n f o r S s b e l i ev i n g t h a t i t h a s t h e p r o p e r t y Q ; a n d i f S

bel ieves that i t is Q

on this basis,

t h e n h e h a s , i n t h e w a y t h e t h i n g l o o k s t o

h im, a conc lus ive r eason f or be l iev ing i t Q .

A l s o, t h er e a r e a n u m b e r o f t h i n gs w h i c h p e o p l e c o m m o n l y p r o f e ss t o k n o w

( S a c r a m e n t o i s t h e c a p i t a l o f C a l i f o r n i a , t h e e a r t h i s r o u g h l y s p h e r i c a l ) f o r

w hich the r e i s no de f in i te p iece o f ev idence , no s ing le s ta te o f a f f a i rs o r eas i ly

spec if iab le s e t o f such s ta tes , w hich even app r ox ima tes a conc lus ive r eason .

I n s u c h c a se s , a l t h o u g h w e c a n c i te n o s i ng l e p ie c e o f d a t a w h i c h i s c l i n c h i n g

a n d , h e n c e , a r e a t a l o s s f o r c o n c l u s i v e r e a s o n s w h e n a s k e d t o g i v e r e a s o n s

( o r w h e n a s k e d H o w d o y o u k n o w ? ) w e, n o n et h e le s s, o f t e n e n o u g h h a v e

c o n c l u si v e r e a s o n s i n a v a s t s p e c t r u m o f e x p e ri e n c e s w h i c h a r e t o o d i v e rs e

t o a d m i t o f c o n v e n i e n t c i ta t i o n . C o u n t l e s s e x p e r ie n c e s c o n v e r g e , s o t o s p e ak ,

o n t h e t r u t h o f a g iv e n p r o p o s i t i o n , a n d t h i s v a r i e t y o f ex p e r i e n c e m a y b e

s u ch t h a t a l t h o u g h o n e may h a v e h a d a n y one o f t h e se e x p e r i e n c e s w i t h o u t

t h e p r o p o s i t i o n i n q u e s t i o n b e i n g t r u e , o n e would not h a v e h a d a / / o f t h e m

unles s w h a t one con sequ ent ly be l ieves w as t r ue . The f a l l ib i li ty o f sour ce A

a n d t h e f a l li b i li t y o f s o u r ce B d o e s n o t a u t o m a t i c a l l y e n t a i l t h a t w h e n A a n d

B agree ab ou t P s be ing the case , tha t , none the les s , P mig ht s t i l l be f a l se .

F o r i t m a y b e t h a t A a n d B

would not

b o t h h a v e i n d i c a t e d t h a t P w a s t h e c a s e

u n l es s P w a s t h e c a s e a l t h o u g h n e i t h e r A n o r B , t a k e n b y t h e m s el v e s , p r o v i d e

c o n c l u s iv e r e a s o n s f o r P . F o r e x a m p l e , a l t h o u g h a n y s i n g le n e w s p a p e r

a c c o u n t m a y b e i n e r r o r o n a p a r t i c u l a r p o i n t , s e v er a l i n d e p e n d e n t v e r s i o n s

( w ir e s er v ic e s, o f c o u r s e , t e n d t o e l i m i n a te t h i s i n d e p e n d e n c e ) m a y b e e n o u g h

t o s a y t h a t w e k n o w t h a t s o m e t h i n g i s s o

on the basis of the newspaper accounts.

A l l o f t h e m w o u l d n o t h a v e b e e n i n s u c h c l o s e a g r e e m e n t u n l e s s t h e i r a c c o u n t

w as subs tan t ia l ly cor r ec t . 14

F i n a l l y , I d o n o t w i s h t o s u g g e s t b y m y u se o f t h e w o r d r e a s o n t h a t w h e n

S has conc lus ive r easons f or be l iev ing P , S has reasoned h i s w a y t o t h e c o n -

c l u s i o n t h a t P i s t h e c a s e f r o m p r e m i s e s i n v o l v i n g R o r t h a t S h as c o n s c i o u s l y

u s e d R a s a r e a s o n i n a r r i v i n g a t t h e b e l i e f t h a t P . I a m i n c l i n e d t o t h i n k

( b u t I s h a l l n o t n o w a r g u e i t ) t h a t w h e n o n e k n o w s t h a t P , o n w h a t e v e r b a s i s

t h is m i g h t b e , li t tl e o r n o r e a s o n i n g i s i n v o l v e d . I w o u l d p r e f e r t o d e s c r ib e

i t as f o l l o w s : s o m e t i m e s a p e r s o n s c o n v i c t i o n t h a t P i s th e c a s e c a n b e

t r aced to a s ta te o f af f a ir s ( o r c lus te r o f s i tua t ions ) w hich sa t is f ie s the th r ee

c o n d i t i o n s d e f i n i n g t h e p o s s e s si o n o f c o n c l u s i v e r e a s o n s . W h e n i t c a n b e s o

t r a c e d , t h e n h e k n o w s ; w h e n i t c a n n o t b e s o tr a c e d , t h e n w e s a y h e d o e s n o t

14 The fa ct tha t all newspapers som etimes prin t things w hich are false does no t mean that

we canno t kno w th at something is true on the basis of a single newspaper account.

The relevant question to ask (as in the case of a person s testimon y--see section 1) is not

whether

newspapers

sometimes print false stories, no t even whether

this newspaper

some-

times prints false stories, but whether

this newspaperwould

have printed

this story

if it were

not true. The Midville Weekly Gazette s story about dope addiction on the campus

may not correspond with the facts, but would The Times have printed this story about

the President s visit to Moscow if it were not tru e?

15

Fred Dretske

k n o w a l t h o u g h h e m a y b e r i g h t a b o u t P s b e i n g t h e c as e . O f c o u r se , h is

b e l i e f m a y b e traceable t o such a source wi thout our be ing able to t race i t .

I n s u c h a c a s e w e a r e m i s t a k e n i n s a y i n g t h a t h e d o e s n o t k n o w .

T u r n i n g n o w t o t h e q u e s t i o n o f w h e t h e r h a v i n g c o n c l u s iv e r e a s o n s t o

be l i eve , a s de f ined by (A)- (C) , cons t i tu t es a suf fi c ien t condi t ion for k nowledge ,

I s h a ll m e n t i o n a n d b r i ef l y r e s p o n d t o w h a t I c o n s i d e r t o b e t h e m o s t s e r i o u s

objec t ions to th i s proposa l .

There i s , f i r s t , a t endency to conf la t e knowing tha t P wi th knowing tha t one

k n o w s t h a t P . I f th i s is d o n e t h e n c o n d i t i o n s ( A ) -( C ) w i ll im m e d i a t e l y a p p e a r

insuf f i c i en t s ince they do not desc r ibe S as knowing or having any bas i s for

be l i ev ing tha t R , h i s bas i s for be l i ev ing P , cons t i tu t es an ade qua te bas i s , much

less a conc lus ive bas is , for be l i ev ing P . Even i f one does not go th i s fa r the re

i s s t i l l a t endency to s ay tha t i f S knows tha t P , then S mus t a t l eas t believe

t ha t he knows tha t P i s the case . I f one adop t s th is v iew then , once aga in ,

c o n d i t i o n s ( A ) - ( C ) a p p e a r i n a d e q u a t e s in c e t h e y d o n o t d e s c r ib e ( n o r d o t h e y

enta i l) t ha t S be l i eves he knows th a t P i s the case . I see no reason , however ,

t o a c c e p t ei t h e r o f t h e se c l ai m s . W e n a t u r a l l y e x p e c t o f o n e w h o k n o w s t h a t

P tha t he be l i eve tha t h e knows , jus t a s we expec t of som eon e who i s r id ing a

bicyc le tha t he be l i eve he i s r id ing one , b ut in ne i the r case i s the be l i e f a

necessary a c c o m p a n i m e n t . T h e c o n f u s i o n i s p a r t i a l ly f o st e r e d , I b e l ie v e ,

by a fa i lure to d i s t ingui sh be tween wha t i s impl i ed in knowing tha t P , and

w h a t i s i m p l i e d ( in s o m e s e n se ) b y s o m e o n e s saying h e k n o w s t h a t P . C o n -

s ide r , howe ver , cases in which w e f ree ly asc r ibe know ledge to agent s in which

i t s eems qui t e implau s ib le to as s ign the l eve l of conceptu a l soph i s t i ca t ion

r e q u is i te t o t h e i r b e l ie v i n g s o m e t h i n g a b o u t k n o w l e d g e , b e l ie v i n g s o m e t h i n g

ab ou t the i r ep i s temic re l a t ion to the s t a t e of a f fa i rs in ques t ion . A dog may

k n o w t h a t h i s m a s t e r i s i n t h e r o o m , a n d I ( a t le a s t) w a n t t o s a y th a t h e c a n

know th i s in a s t ra ight forward sense wi thout (neces sa r i ly) posses s ing the

c o n c e p t u a l u n d e r s t a n d i n g w h i c h s e e m s t o b e r e q u ir e d t o s a y o f h i m t h a t h e

be l i eves he kn ows th i s , be l i eves tha t he has go od reasons , or be l i eves anything

abo ut h i s ep i s t emic re l a t ion to the fac t tha t h i s mas te r i s in the r oo m. x5

Y e t , i t s e e m s p e r f e c t ly n a t u r a l t o s a y o f a d o g t h a t i t k n o w s ( s o m e t i m e s ) w h e n

h i s m a s t e r i s i n th e r o o m . A n d t h is i s n o t , l e t m e a d d , s i m p l y a m a t t e r o f th e

d o g s b e i n g r ig h t a b o u t s o m e t h i n g . F o r i f w e k n e w t h a t th e d o g t h o u g h t h i s

m a s t e r w a s i n t h e r o o m o n t h e b a s i s , s a y , o f c e r ta i n s o u n d s a n d s m e ll s ( s o u n d s

and smel l s tha t w ere , genera l ly speaking , a re l i ab le sign of h is mas te r ) wh en

these sound s an d sm el l s were to ta l ly unre la t ed to h i s mas te r s presence in the

r o o m on this occasion w e w o u l d n o t s a y t h e d o g k n e w e v e n i f h e h a p p e n e d

t o b e r i g h t a b o u t h i s m a s t e r s b e i n g in t h e r o o m . I m a g i n e a b l in d d o g s

b e i n g t a k e n i n b y a t h i e f in h i s m a s t e r s c l o th i n g w h i l e t h e m a s t e r l ie s u n -

consc ious in the corner . The do g, t aken in as he is by the th ie f , ce r t a in ly

th inks h i s mas te r is in the room , an d he i s r ight (a l though, of course , he is

15 This seems to be the essence of Arth ur Dan to s argument (against Hintikka) th at S

knows that P does not entail S knows that S knows that P in On Knowing that We

Know , Epistemology: New Essays in the Theory of Knowledge Avrum Stroll (ed.),

1967, pp. 49-51.

16

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9/11

Conclusive Reasons

w r o n g a b o u t t h i s m a n s b e i n g h is m a s te r ) . B u t j u s t a s c l e a r l y t h e d o g d o e s n o t

k n o W t h a t h i s m a s t e r i s i n t h e r o o m . W e r e q u i r e c o n c l u s i v e re a s o n s e v e n

i n t h e c a s e o f a n i m a l s . W o u l d t h e d o g h a v e s m e l l e d w h a t h e d i d, a n d h e a r d

w h a t h e d i d , i f h i s m a s t e r w a s n o t i n t h e r o o m ? I f h e

wouM have

o r

might

have t h e n h e d o e s n t k n o w . 16

F u r t h e r m o r e , c o n s i d e r a s c e p t i c w h o t a l k e d h i m s e l f i n t o b e l i e v i n g t h a t h i s

g r o u n d s f o r b e l i e v i n g in a n e x t e r n a l w o r l d w e r e n o t s u f fi c ie n t ly g o o d t o t r u l y

s a y h e knew t h e r e w a s a n e x t e r n a l w o r l d a n d , h e n c e , n o l o n g e r b e l i e v e d ,

p o s i ti v e l y d i s b e l ie v e d , t h a t h e k n e w t h e r e w a s a n e x t e r n a l w o r l d . I t h i n k

t h a t as l o n g as h e c o n t i n u e d t o b e l i e v e ( w i t h o u t d o u b t , r e s e r v a t i o n o r q u e s -

t i on ) t h a t t h e r e w a s a n e x t e r n a l w o r l d , a n d c o n t i n u e d t o b e l i e v e i t o n t h e

s a m e b a s is a s w e d o , h e w o u l d k n o w t h e r e w a s a n e x t e r n a l w o r l d ( a s s u m i n g

h e r e t h a t we k n o w i t ) whatever h e h a p p e n e d t o b e l i ev e a b o u t w h a t h e k n e w . 17

T h e r e m a r k s I h a v e j u s t m a d e a b o u t b e l i e v i n g t h a t o n e k n o w s a p p l y , a

fortiori

t o k n o w i n g t h a t o n e k n o w s . O n e q u a li f ie s f o r k n o w l e d g e w h e n o n e

h a s c o n c l u s i v e r e a s o n s f o r b e l i e v i n g ; o n e n e e d n o t , i n a d d i t i o n , k n o w t h a t

o n e h a s c o n c l u s i v e g r o u n d s . T o k n o w t h a t o n e h a s c o n c l u s i v e r e a s o n s ,

e m p i r i c a ll y c o n c l u s i v e r e a s o n s , m e a n s t h a t o n e k n o w s t h a t ( A ) i s t r u e a n d

t h is , i n t u r n , m e a n s t h a t o n e h a s l o g i c a l l y c o n c l u s i v e r e a s o n s ( s e e c a s e I

a b o v e) . K n o w i n g t h a t o n e k n o w s i s a f o r m o f i n n o c u l a t i o n a g a i n s t s c e p t i c al

c h a l le n g e s to t h e q u a l i t y o f o n e s e m p i r i c a l l y c o n c l u s i v e r e a s o n s ; o n e knows

16 Robert Sleigh has suggested an interesting modification of this cas e--o ne that w ould

appear to cause difficulty. Suppose that the dog is taken in by the th ief but, in addit ion,

circumstances are such that the thief

wouM not

be in the room

unless

the dog s mas te r

was also there. I t m ay be a bit diff icult to imagine circumstances of this sort , but o ther

examples (not involving animals as the knowers) can easily be manufa ctured (Chisholm s

example of a man mistaking a sheep dog for a sheep in a f ield works nicely when the

further condit ion is added that the dog w ould not be there unless there were some sheep

in the f ield). With such a modification it would seem that the dog has conclusive

reasons for believing his master present since i t would not hav e heard and smelled what

i t did unless i ts master was present. But does the dog kno w that i ts master is present ?

I think i t natural to re ad this si tuation in such a way that the d og believes that i ts master

i s in the room because i t mistakenly believes that this man (the thief) is his master . If

read in this way, of course, there is no difficulty since the d og s basis for believing that

his master is present is obviously defective--i t is not true, nor does th e dog know,

that this man is his master . If , however, we read this case in such a way that the do g

simply takes the sounds and smells as a sign of his master s presence (without mis-

identifying anyone) then the dog does have conclusive reasons (he wo uld not h ave

smelled and heard what he did unless his master was presen0 but I should want to say

that in this case he knows that his master is present. I do not think that this is an ex-

cessively strained interpretation. I t seems to me quite similar to si tuations in which we

know that something is so on the basis of some indicator or sign (e.g. an instrument

reading) but are ignorant as to the mechanism in virtue of whichthat indicator o r sign is a

reliable (conclusive) index of what we purport to know.

17 Examples such as this, along with oth er mo re systematic considerations, con vince me

that not only should we not require that S believe he has conclusive reasons in order to

know, but also that we should not re quire that he not believe he does not have con -

clusive reasons. If a person s believing that he knows is compatible with his not know ing,

why shou ldn t a person s believing that he does not k now be compa tible with his

knowing ?

2 .

1 7

Fred Dretske

t ha t R w ould no t be t he ca se un l e ss P we re the case . Lac k ing such innocu-

l a t i on , howeve r , one s t il l know s . One i s s imply l e ss p rep a red t o de fend

(just i fy) the claim t o k n o w l e d g e ; b u t i n a b il i ty t o j us t i f y t h e t r u t h o f w h a t o n e

c l a ims , is se ldom, i f eve r , a r e fu t a t i o n o f t he t ru th o f wha t one c l a ims , and

th i s app l i e s t o knowledge c l a ims a s we l l a s any o the r .

The re i s a c e r t a in t ype o f coun te r -ex ample which exp lo i t s t h i s confus ion ,

and I wou ld l i ke t o men t ion i t a t t h i s po in t t o fu r the r c l a r i fy t he i n t en t o f

cond i t i o ns (A) - (C) . Suppo se S , fo r a pe r fec t l y s i ll y r ea son , o r by shee r

acc iden t , come s t o t he t rue be l i e f t ha t ( a s t a te such a s ) R i s a conc lus ive

rea son fo r be li ev ing tha t ( a s t at e such a s ) P i s o r was t he ca se . Hap pen ing

upon a s t a t e such a s R in t he appropr i a t e c i r cumstances , t hen , he be l i eves t ha t

P i s t h e c a s e o n t h e b as i s o f R . D o e s n ' t h e n o w h a v e

conclusive reasons

f o r

be l i ev ing P ? Bu t i sn ' t i t equa l ly obv io us t ha t he does

not

know tha t P i s t he

case ? Yes and no . Yes , he does hav e conc lus ive rea sons ( a s I have de f ined

th is ) . No , i t i s no t obv io us t ha t he does no t kno w tha t P is t he ca se . I

be l i eve t ha t t h i s ob j ec t i on t r ades on t he ve ry confu s ion we have j us t d i scussed ;

tha t i s , i t m i s t aken ly supp oses t ha t i f S does no t kno w th a t R i s conc lus ive

fo r P (ha s no l eg i t ima te ba s i s fo r be l i ev ing th i s) , t hen S does n o t kno w tha t

P i s t he ca se (ha s no l eg i t ima te ba s i s fo r be l i ev ing thi s ). Or , w ha t I t h ink

amount s t o t he ve ry same th ing , i t f a l l a c ious ly conc ludes t ha t S (g iven h i s

bas i s fo r be l i e f ) m igh t be wrong abou t P f rom the f ac t t ha t S (g iven h i s ba s i s

fo r be li e f ) m igh t be wro ng abo u t R ' s be ing conc lus ive fo r P . Or , t o pu t i t i n

s ti ll ano th e r way , i t i ncor rec t l y suppo ses t h a t i f i t i s, e i t he r whol ly o r i n pa r t ,

a cc iden t a l t ha t S i s r i gh t abou t R ' s be ing conc lus ive fo r P , t hen i t i s a l so ,

e i t he r whol ly o r i n pa r t , a cc iden t a l t ha t he i s r i gh t abou t P ' s be ing t he ca se .

Such inferences are fa l lac ious and, I be l ieve , they are fa l lac ious in the same

w a y a s t h e f o l l o w i n g t w o e x a m p l e s : ( a) C o n c l u d i n g t h a t i t w a s s h e e r l u c k

(chance ) , a me re acc iden t , t ha t dec l a re r m ade h i s b id o f seven spades becau se

i t was shee r l uck ( chance ) , a mere acc iden t , t h a t he was dea l t t h i r t e en spa des ;

( b ) C o n c l u d i n g t h a t t h e w i n d o w w a s b r o k e n a c c i d e n t a l l y b e c a u s e t h e m a n

w h o t h r e w t h e b r i c k t h r o u g h i t c a m e b y t h e b el i ef t h a t b r i c k s b r e a k w i n d o w s

in an acc iden t a l ( s i l l y , un rea sonab le , o r wha t have you) way .

Some t imes t he s t age i s se t fo r a non-acc iden t i n a pure ly acc iden t a l way .

In t he above ca se i t

is

a c c i d en t a l t h a t S k n o w s t h a t P o n t h e b a s is o f R , b u t

t h is d o e s n o t m a k e i t a c c i d en t a l t h a t h e i s r i g h t a b o u t P - - f o r h e b e li ev e s P o n

the ba s i s o f R an d R s im ply wou ld no t be t he case un l ess P we re t he ca se .

Give n R , i t i s no t a t a ll a cc iden t a l t ha t he is r i gh t abou t P . Wh a t is acc iden t a l

i s t ha t he was co r rec t i n be li ev ing t ha t R was a conc lus ive r ea son fo r P , bu t a l l

t h is s h o w s i s t h a t h e d o e s n o t k n o w t h a t R i s c o n c l u si v e f o r P , d o e s n o t k n o w

tha t he know s tha t P . An d wi th t h i s mu ch I am in fu l l ag reement . 18

xs In speaking of 'accidentality in this conn ection I have in mind Peter Unge r's analysis

of knowledge in terms o f its no t being at all accidental th at the perso n is right (see his

'An Analysis of Factual K nowledge'

Journal o f Philosophy

Marc h 21, 1968). Tha t is, I

want to claim that any S satisfying conditions (A)-(C) is a person of whom it is true to

say that it is not at all accidental that he is right about P's being the case, although it

may he accidental that this is no accident (it may be accidental that he

has

conclusive

reasons, that he has reasons in virtue of which it is not at all accidental that he is fight

about P).

18

8/11/2019 dretske 1971

10/11

C onc l us i ve R easons

Scept ica l a rguments have t r ad i t ional ly r e l ied on the f ac t tha t S , in pur -

por t ing to know that P o n the bas is o f R, was consp icuous ly unab le to

jus t ify the qual i ty o f h is r easons , was hopeless ly incapab le o f p rov id ing

sat i s fac to ry docu men ta t ion fo r the t ru th o f (A) . The co nclus ion fa l lac ious ly

drawn f rom th is was tha t S d id no t know that P was t rue ( s imply) on the

basis o f R. Clear ly , however , a l l tha t fo l lows f rom the f ac t tha t S has l i t t le

or no g rounds fo r th ink ing (A) t rue i s tha t he lacks sa t i s f ac to ry g rounds fo r

th ink ing he knows tha t P is t rue . I t does no t fo l low that he does no t know

that P i s t rue . Know ing tha t P i s the case on the basi s o f R invo lves knowing

that R is the case (and be lieving P o n that basis)

w hen A ) i s t rue .

I t is the

t ru th o f (A) , no t the f ac t tha t o ne knows i t t rue , which makes R conclus ive

for P.

There i s ano t her r espect in which t r ad i t ional scep t ica l a rguments ha ve been

on the mark . One way of express ing my argum ent i s to say tha t the f ami l iar

and ( to some) ex t r emely annoy ing chal lenge, Cou ldn t i t be an i l lusion

( fake , imi ta t ion , e tc . ) ? o r I sn t i t poss ib le tha t you are d reaming (hal luc inat -

ing , e tc . ) ? i s , in a cer ta in impor tan t r espect , qu i te p roper and appropr ia te

even w hen t here i s no spec i a l r eason t o t h i nk you are dreami ng , ha l l uc i na t ing ,

con f ron t i ng a f a ke , e t c .

For our knowledge c la ims do en ta i l tha t the ev i -

dence o r g rounds one has fo r be l iev ing

w o u l d n o t

have been avai lab le i f

what one consequen t ly bel ieves ( and c la ims to know) were f a l se ; hence ,

they do en ta i l tha t , g iven one s ev idence o r g roun ds ,

i t i s f a l s e t ha t one

m i g h t b e m i s t a k e n

abou t what one purpor t s to know. (1 ) does en ta i l the

fa ls i ty o f (3 ) ; hence , (1 ) can be sh own to be f a lse no t on ly by show ing tha t

S is

dreaming or ha l luc inat ing