CHAPTER - III

THE ARGUMENT FROM ILLUSION

Statement of the Argument

The argument on which philosophers who have re jec ted

the naive real ist account of perception have mainly relied has

come to be known as the argument from il lusion. About this

argument Ayer writes :

“The starting point o f this argument is that

objects appear d ifferently to different observers,

on differently to the same observer under

different conditions, and further, that the way in

which they appear is causal ly dependent upon

extraneous factors such as the p resence of light,

the posit ion of the observer , or the state of his

nervous system. These premises themselves are

not l ikely to be questioned. The d iff icu l ty is to

see how they can lead to the des ired r e su l t” . 1

A yer ’s account on this argument is based on H.H.

Price’s discussion in chapter 2 of his book Perception

(London, 1932). Ayer took up the issue for the first t ime in a

1 A.J. Ayer, The Problem of Knowledge, p. 87.

lengthy paper in The Foundat ion o f Empir ical Know ledge

(London, 1940). 1'he same issue came up later in both J_he

Problem o f Knowledge and The Centra l Q ues t ions o f

P h i lo sophy . The argument begins by po in t ing to the ex is tence

of i l lus ions of var ious kinds, from sticks that look bent in

water to double vision, thus indica t ing that we sometimes see

things wrongly. It is then asser ted tha t there is no

Phenomenological d i f fe rence between cases o f i l lusion and

cases o f ver idical percept ion . This menas that there is no

difference between the two from the poin t of view o f

exper ience itself. The ques t ion that comes up is : How can

we be certain in the case o f any given percep tua l exper ience

that it is ver idical ? Now, i f we cannot be certain , there is

room for doubt whether any percep tua l exper ience is

veridical. In some vers ions o f the a rgument it is also said

that in the il lusory percep t ion what we perceive cannot be a

feature o f a physical or materia l object . Hence, if there is no

phenomenal difference between the i l lu so ry and ver idical

perception, there are no grounds for saying that in the case

of ver idical perception what we perceive is a feature of a

material object.

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Veridical and Non - Veridical Perception

In the e s s a y on “ The A rg u m e n t f rom I l l u s i o n ” in The

F o u n d a t io n s o f E m p i r ic a l K n o w le d g e , A y e r s ta r t s the

d i scu s s io n w i th a luc id e x p o s i t i o n o f the a r g u m e n t and then

an e v a lu a t io n o f the a rg u m e n t is g iven . The e x p o s i t i o n is

made th rough with the he lp o f i l l u s t r a t i o n s an d e x p la n a t io n s .

A yer says : -

“T h is a rgum ent , as it is o r d in a r i ly s ta ted , is based

on the fac t that the m a te r ia l th ings may p re se n t

d i f f e re n t a p p ea ra n c e s to d i f f e r e n t o b s e rv e r s , or to

the same ob se rv e r in d i f f e r e n t c o n d i t io n s , and tha t

the c h a r a c te r o f th e se a p p e a r a n c e s is to some

ex ten t cau sa l ly d e t e r m in e d by the s ta te o f the

c o n d i t io n s and the o b se rv e r . For in s t a n c e i f it

r em a rk e d tha t a co in w h ich looks c i r c u l a r f rom

one p o in t o f v iew m ay look e l l i p t i c a l f rom

a n o th e r ; o r tha t a s t i ck w h ich n o r m a l ly ap p e a r s

s t r a ig h t looks ben t w h e n it is seen in w a te r ; or

tha t to p eo p le w ho take d rugs such as m esca l ,

th ings a p p ea r to c h a n g e th e i r c o lo u r s ............. The

same th in g s o c c u r re d in the d o m a in s o f the o th e r

senses , in c lu d in g th e s e n se o f touch . It m a y be

39

p o in te d out , fo r e x a m p le , tha t the t a s te tha t a

th ing a p p e a r s to have m ay vary w i th the co n d i t io n

o f the p a la te ; or th a t a l iq u id wil l seem to have a

d i f f e r e n t t e m p e r a tu r e a c c o r d in g as the h a n d tha t is

f e e l in g it is i t s e l f ho t or co ld ; o r t h a t a coin

s eem s la rg e r w hen it is p la c e d on th e to n g u e than

w hen it is held in the p a lm o f the h a n d ; or, to

take a case co m p le te h a l lu c in a t io n , th a t p eop le

who hav e had l im bs a m p u ta t e d m ay s t i l l con t in u e

to feel pa in in th e m ” . 2 ,

Here , the f irs t p o in t is th a t th e re is no in t r i n s i c

d i f fe ren ce in k in d b e tw e en th o se o f our p e r c e p t io n th a t are

ver id ica l in t h e i r p r e s e n ta t i o n o f m a te r ia l th in g s and th o se

tha t are d e lu s iv e . This p o in t w as a l r ead y r a i s e d by H.H. P r ice

in his book P e rc ep t io n ( p. 31) w hen we look at a s t r a ig h t

stick, w hich is r e f r a c ted in w a te r and so a p p e a r s c rooked , our

e x p e r ien ce is q u a l i t a t iv e ly the same as i f we were lo o k in g at

a s tick tha t r e a l ly was c ro o k ed . W h en p eo p le w hose legs have

been a m p u ta te d c o n t in u e to fee l p re ssu re upon them, t h e i r

exper ience is q u a l i t a t i v e ly the same as i f p ressu re r e a l l y

were be ing exer ted upon t h e i r legs. But it is argued th a t if.

A.J. Ayer. The Foundations of Empirical Knowledge, p. 3.

40

when ou r p e r c ep t io n w e re de lus ive , we were a lw a y s

p e rc e iv in g so m e th in g o f a d i f f e r e n t k in d f rom w h a t we

p e rce iv ed w h en they w ere v e r id ic a l , we sh o u ld e x p e c t ou r

ex p e r ien ce to be q u a l i t a t iv e ly d i f f e r e n t in the two cases . We

should e x p e c t to be ab le to te l l f rom the i n t r in s i c c h a r a c t e r

o f a p e r c e p t io n w h e th e r it w as a p e r c e p t io n o f s e n s e - d a tu m or

o f a m a te r ia l th ing. But, th i s is no t p o s s ib le , as the e x a m p le s

tha t we have g iven have show n.

S econd ly , the fac t t h a t th e re is the d i s t i n c t io n b e tw e e n

the be l ie f s th a t a c co m p an y v e r id ic a l and d e lu s iv e p e r c e p t i o n

does not j u s t i f y the v iew th a t these are p e r c e p t i o n s o f

g ene r ica l ly d i f f e re n t o b jec t s . It s o m e t im es h a p p e n s t h a t a

de lus ive ex p e r ien ce is no t o n ly q u a l i t a t i v e ly

in d i s t in g u ish ab le from one th a t is v e r id ic a l b u t is a l so i t s e l f

be l ieved to be v e r id ica l , as in the e x a m p le o f the m i rag e .

C onve rse ly th e re are c a s e s in w h ic h e x p e r i e n c e s th a t are

ac tua l ly v e r id ic a l are b e l i e v e d to be d e lu s iv e , as when we see

someth ing so s t range or u n e x p e c t e d th a t we say to o u r s e lv e s

tha t we m u s t be d ream ing . T h e f ac t is tha t f rom the c h a r a c t e r

o f a p e rc e p t io n c o n s id e re d by i t se l f , ap a r t f rom its r e l a t io n

41

from to further sense-experience, it is not possible to tell

whether it is veridical or non-veridical.3

Thirdly, the fact which is supposed to show that even

in the case o f veridical perceptions we are not directly aware

of material things is that veridical and delusive perceptions

may form a continuous series, both with respect to their

qualities and with respect to the conditions in which they are

obtained ( this is a point mentioned by Price ). Thus, i f we

gradually approach an object from a distance we may begin

by having a series of perceptions which are delusive in the

sense that the object appears to be smaller than it real ly is.

Let us assume that this series terminates in a veridical

perception. Then the difference in quality between these

perception and its immediate predecessor will be of the same

order as the difference between any two delusive perceptions

that are next to one another in the series. Now the question

arises Does not the fact that veridical and delusive

perceptions shade into one another in the way that is

indicated by the above example show that the objects that are

perceived in either case are generically the same ? From this

it would follow, if it was acknowledged that the delusive

3 Ibid, p. 7.

42

p e rc e p t io n s w ere p e r c e p t io n s o f sense - da ta , tha t w h a t we

d i re c t ly e x p e r i e n c e d was a lw a y s a sense d a tu m and n e v e r a

m a te r ia l th ing .

A n o th e r a rg u m en t th a t has to be c o n s id e r e d in th i s

con tex t is b a s e d upon the f a c t th a t a l l o u r p e r c e p t io n s ,

w he the r v e r id ic a l or d e lu s iv e , a re to som e e x te n t c a u s a l l y

d ep en d en t b o th upon e x te rn a l c o n d i t io n s , such as the

ch a rac te r o f l ight, and Upon our p h y s io lo g ic a l and

p sy ch o lo g ica l s ta tes . In the case o f p e r c e p t i o n s tha t we take

to be d e lus ive th is is a f ac t tha t we h a b i tu a l ly r e c o g n iz e . We

say, for ex am p le , tha t the s t ick looks c r o o k e d b e c a u s e i t is

seen in w a te r ; tha t the w h i te w a l l s a p p e a r g reen to us

because we are w ea r ing g reen sp ec ta c le s ; t h a t the w a te r f e e l s

cool because the hand is ho t ; th a t the m u r d e r e r sees the g h o s t

o f his v ic t im b e ca u se o f h i s bad c o n s c i e n c e or b e ca u s e he has

been tak in g drugs . In the case o f p e r c e p t i o n s th a t we tak e to

be ve r id ic a l we are ap t n o t to n o t i c e such c a u s a l

d ependenc ies , s ince as a ru le i t is on ly the o c c u r r e n c e o f the

u n ex p ec ted or the a b n o rm a l t h a t in d u c e s us to look fo r a

cause. But in th is m a t te r a l so th e re is no e s se n t i a l d i f f e r e n c e

b e tw een v e r id ic a l and d e lu s iv e p e rc e p t io n s .

43

A f te r e s ta b l i s h in g all th e se po in ts , the a rg u m en t f rom

i l lu s io n p r o c e e d s as f o l lo w s ;

“ It is h e ld to be c h a r a c t e r i s t i c o f m a te r ia l th in g s

th a t th e i r ex i s ten ce and th e i r e s se n t i a l p r o p e r t i e s

are i n d e p e n d e n t o f any p a r t i c u la r o b se rv e r . For

they are su p p o sed to c o n t in u e the sam e , w h e th e r

they are obse rved by one p e r so n or an o th e r , or no t

ob se rv e d at all. B u t th is , it is a rg u ed , has been

shown no t to be t rue o f the o b je c t s we

im m ed ia te ly e x p e r ie n c e . And so the c o n c lu s io n is

r e a ch e d tha t w ha t we im m e d ia te ly e x p e r i e n c e is in

no case a m a te r ia l th ing . A c c o rd in g to th is w ay s

o f r ea so n in g , i f some p e rc e p t io n s are r ig h t ly he ld

to be ve r id ica l , and o th e r s de lu s iv e , it is b ecause

o f the d i f f e ren t r e l a t io n s in w h ich th e i r o b je c t s

s tand to m a te r ia l th in g s , and it is a p h i lo s o p h ic a l

p ro b le m to d i sc o v e r w h a t th ese r e l a t i o n s are. We

may be a l lo w ed to have in d i r e c t k n o w le d g e o f the

p ro p e r t i e s o f m a te r ia l th in g s . But th i s k n o w led g e ,

it is held , must be o b t a in e d th ro u g h the m ed ium

o f sense - data, s in ce th ey are the o n ly o b jec t s o f

44

w hich , in sense - p e r c e p t io n , we are im m e d ia te ly

99 4aware .

Thus, the a rg u m en t f rom i l lu s io n lead s to the log ica l

r eq u i re m e n t fo r the i n t ro d u c t io n to sense - data. As A yer

says, “ The main p ro p o s i t io n which the a rg u m e n t f rom

il lus ion , as I have in te rp r e te d it, was s u p p o s e d to e s t a b l i s h

was that w h a t we see, or o th e rw ise d i r e c t ly e x p e r ie n c e , are

never m a te r ia l th ings , bu t on ly s e n se -d a ta ’V

Misuse of the Argument

Ayer, however , w arns us aga ins t the m isu se s o f the

a rgum ent f rom i l lusion. He m a in ta in s , fo r ex a m p le , t h a t it

will be im p ro p e r to say th a t the w or ld o f s e n s ib le p h e n o m e n a

is s e l f - co n t rad ic to ry , b e c a u s e no a rg u m en t can p o s s ib ly p ro v e

it, for the r e a so n tha t the n o t io n o f s e l f - c o n t r a d i c t i o n is no t

app l icab le to the p h en o m en a th e m se lv e s . It does not m ake

sense so say o f d i f fe ren t p h e n o m e n a tha t th e y c o n t r a d ic t each

o ther .W e shou ld , ra ther , kn o w th a t p h e n o m e n a s im ply occur .

C on t rad ic t io n , w hich is a te rm o f lo g ica l a p p ra i s a l can be

leg i t im a te ly a p p l ie d to th o se p r o p o s i t i o n s w h ic h are u sed to

descr ibe the p h en o m en a . H e n c e , we have to say tha t w h a t the

a rgum ent f rom i l lus ion is s u p p o se d to p ro v e is tha t i t is

4 Ibid. pp. 10 - 11.5 Ibi4 p. 26.

45

im p o ss ib le to d esc r ib e w h a te v e r p h e n o m e n a o ccu r w i th o u t

sooner or l a te r f a l l in g in to s e l f - c o n t r a d i c t i o n . But so fa r f rom

prov ing th is , the a r g u m e n t d o e s no t sh o w even th a t any

c o n t ra d ic t io n is invo lved in the p ro p o s i t i o n s th a t we a c tu a l l y

use to d e s c r ib e p h en o m en a . It is, h o w ev e r , t rue to say th a t

some o f ou r p e rce p t io n s are v e r id ic a l and o th e r s a re n o n -

ver id ica l . But in say ing th i s th e r e is no c o n t r a d i c t io n . T h e re

would be a c o n t r a d ic t io n o n ly i f the sam e a p p e a r a n c e s w ere

he ld to be bo th ve r id ica l and d e lu s iv e in the sam e sense .

The re is an o th e r m i s u n d e r s t a n d in g w h ic h sh o u ld be

avoided . This is with re g a rd to the s ay in g tha t “ W e can

n ever be ce r ta in tha t any o f the p r o p o s i t i o n s in w h ic h we

express our p e rc e p tu a l j u d g m e n t s are t ru e In th i s

c o nnec t ion , we shou ld keep in m ind th a t the n o t io n o f

ce r ta in ty does no t app ly to p ro p o s i t i o n s o f th is k ind . The

not ion o f c e r t a in ty a p p l ie s to the ap r io r i p r o p o s i t i o n o f log ic

and m a th e m a t ic s , and the fac t t h a t i t d o e s n o t app ly to th em

is an e s se n t ia l mark o f d i s t i n c t io n b e t w e e n them and

em pir ica l p ro p o s i t io n s . A y e r says t h a t once th i s is

recognised , the mot ive fo r s c e p t ic i s m has gone . The m is ta k e

o f the scep t ic is no t t h a t he m a in ta in s any f a l s e h o o d , or

doubts some s e l f e v id e n t t ru th , but t h a t he in s i s t s on

app ly ing to one c lass o f p r o p o s i t i o n s a c r i t e r io n th a t is

46

a p p ro p r ia te on ly to an o th e r . The p o in t to be n o ted is the f a c t

tha t the r e l a t io n s h ip o f p r o p o s i t i o n s d e s c r ib in g the c o n te n t s

o f our s e n s e - e x p e r ie n c e s to p r o p o s i t i o n s im p ly in g the

ex i s ten ce o f m a te r ia l t h in g s is no t th a t p r e m is e s to

c o n c lu s io n in a d ed u c t iv e a rgum en t .

Evaluation o f the Argument from Illusion

An im p o r ta n t v i e w p o in t w h ich we g a th e r from A y e r ’s

account o f the a rgum en t f rom i l lu s ion is t h a t the d i f f e r e n t

theor ie s o f pe rcep t io n a r e ' t h e o r i e s fo r the a d o p t io n o f

a l t e rn a t iv e l anguages ( i .e . , m a te r ia l o b j e c t l an g u ag e and

s ense -da ta language , fo r in s tan ce ) . A y e r tak es in to

c o n s id e ra t io n the use o f the a g ree m e n t f rom i l lu s io n to r e fu t e

the p e rce p tu a l theory o f N a iv e R ea l ism . In th is r e s p e c t he

refers to P r i c e ’s view. A c c o rd in g to Pr ice , w hat is to be

u n d e rs to o d by Naive R ea l i sm is the t h e s i s tha t v isua l and

tac tua l s e n se -d a ta are p a r t s o f the s u r f a c e s o f m a te r ia l th ings .

Th is is to say tha t it is a lw a y s the m a te r ia l th in g w h ich we

see or touch . P r ice says th a t the a rg u m e n t from i l lu s io n

aims at r e fu t in g th is th e s i s . H ow fa r the a r g u m e n t is

success fu l depends upon the w ay the th e s i s is in t e rp re te d . I f

one a ssum es th a t the n a iv e r e a l i s t is u s in g the w o rd s “ s e e ”

and “t o u c h ” in such a w a y th a t to say o f an o b jec t th a t i t is

47

seen o r t o u c h e d does no t en ta i l s ay ing th a t i t ex i t s or th a t i f

r ea l ly has the p r o p e r t i e s tha t i f a p p e a r s to have , then it is

c lea r th a t the a rg u m en t f ro m i l lu s io n c a n n o t be used to r e fu t e

the na ive rea l i s t . If, on the o th e r hand, he is u s in g th i s w o r d s

in a w ay th a t does c a r ry th ese i m p l i c a t i o n s , t h en the

a rgum ent does re fu te h im, so long as he a d h e r e s in o th e r

r e sp ec t s to ou r o rd in a ry u sag e o f w ords . B u t i f he is p r e p a r e d

to m odify th is usage and i n t r o d u c e su i t a b le c o n v e n t io n s w i th

regard to the v a r ia b i l i ty o f m a te r ia l th ings , th e n it is p o s s ib l e

for him c o n s i s t e n t ly to m a in ta in his p o s i t io n w i th o u t r u n n in g

co u n te r to the em p i r ica l f a c t s . 6 A y e r c o n c lu d e s the

d iscuss ion s ta t in g tha t i t is d e s i r a b le to u se a t e c h n ic a l

t e rm in o lo g y o f some k ind in p h i l o s o p h i s i n g a b o u t p e r c e p t io n ,

and that o f those tha t a re a v a i l a b le the t e r m in o lo g y o f the

sense -da tum th eo ry a p p e a r s to be the best.

The Causal Theory of Perception

A fte r d e ta i l e d s tu d y o f the a r g u m e n t f rom i l lu s io n ,

Ayer d w e l t on “ The C a u s a l T h e o ry o f P e r c e p t io n ” . In th i s

r e spec t , he f o l lo w e d H .H . P r ice , a l t h o u g h in some p o in t s he

d iv e r ted f rom Price . P r ic e d i s t i n g u i s h e d two form s o f the

a rgum en t f rom i l lu s ion - the p h e n o m e n o lo g ic a l and C a u s a l

6 Ibid pp. 46 - 7.

48

a r g u m e n t s . A c c o rd in g to h im, it is th e f i r s t th a t is the

a rg u m en t f rom i l lu s ion p ro p e r , and he th in k s th a t th i s at l ea s t

shows w h a t he ca l ls n a iv e r e a l i sm to be fa l se . P r ice w r i te s :

“ It is c o m m o n ly h e ld th a t the A r g u m e n t f rom

I l lu s io n ( as it is c a l le d ) is s u f f i c i e n t to r e fu te

N a iv e R ea l ism . A nd th is s eem s s u b s t a n t i a l l y t rue .

Bu t w h a t exac t ly th e a rg u m e n t p r o v e s is no t very

c lear . The fac t s e em s to be tha t th e re are r e a l ly

two d i s t in c t a rg u m e n ts : fo r w an t o f b e t t e r n am es

we w il l ca ll them r e s p e c t i v e l y the

P h e n o m e n o lo g ica l A r g u m e n t and C au sa l

A rg u m en t . C o n t ra ry to co m m o n o p in io n , the f i r s t

is by fa r m ore im p o r ta n t . It seeks to s h o w d i r e c t ly

tha t th e re are v isua l and t a c tu a l s e n s e - d a t a w h ic h

c a n n o t be iden t ica l wi th p a r t s o f the su r f a c e o f

m a te r ia l ob jec ts . The s e c o n d s eek s to show th a t

v isua l and tac tu a l s e n s e - d a t a o n ly e x i s t w i th

c e r ta in p ro c e sse s , o th e r th an s e n s in g bu t

c o n te m p o r a ry w i th it , a re go ing on in the n e rv o u s

sys tem and p e rh a p s in the m ind o f the b e in g w h o

s e n se s them. And it is i n f e r r e d f ro m th i s tha t th ey

c a n n o t be id en t ic a l w i th p a r t s o f the s u r f a c e s o f

49

ob je c t s ; for such an o b jec t ( and th e r e fo re the

su rface o f it ) ex h y p o th e s i s c o n t in u e s to ex is t at

t im es w hen we are no t sens ing , and it is no w

c o n te n d e d tha t at th o se t im es the s e n se -d a ta do

no t e x i s t ” .7

We have a l r ea d y d i s c u s s e d A y e r ’s t r e a tm e n t o f th is

a rgument . We have s ta ted th a t the p r o b le m l ie s in a t t e m p t in g

to answ er the ques t ion : H ow can we be c e r t a in in the case o f

any g iven pe rcep tu a l e x p e r i e n c e tha t it is v e r id ic a l ? N o w , i f

we can n o t be cer ta in , ther'e is room fo r d o u b t w h e th e r any

pe rce p tu a l e x p e r ien ce is v e r id ic a l . In some v e r s io n s o f the

a rgum ent it is a lso said th a t in the i l lu so ry p e r c e p t io n w h a t

we pe rce ive canno t be a f e a tu re o f a p h y s ic a l or m a te r i a l

ob ject , and hence , i f the re is no p h e n o m e n o lo g ic a l d i f f e r e n c e

be tw een the i l lu so ry and v e r id ic a l p e r c e p t io n , the re a re no

grounds fo r s ay ing tha t in the case o f a ve r t ic a l p e r c e p t io n

what we p e rce iv e is a fu tu re o f a m a te r ia l ob jec t . It is th i s

last po in t tha t is the m a in t a rg e t o f J .L. A u s t i n ’s a t t ack w h e n

he speaks o f the a rg u m e n t t r a d in g on a c o n fu s io n b e tw e e n

i l lu s ions and d e f u s io n .8

H.H. Price, Perception, p. 27.8 J.L. Austin, Sense and Sensibilia, Ch. III.A delusion implies a false belief on the part o f the person who has it and the suggestion that there is nothing actually there corresponding to it. In the case of an illusion, there is normally

50

In c h a p te r 5 o f h is book Sense and S e n s ib i l i a , A u s t in

no ted a n u m b e r o f d e f i c i e n c i e s in the ab o v e a rgum en t . It is

the c h i e f m e r i t o f A u s t i n ’s b o o k to p o in t ou t tha t a p p e a ra n c e ,

h a l lu c in a t io n , i l lu s ion , d e lu s io n , non - v e r id ic a l p e r c e p t io n ,

are no t e q u iv a le n t and th a t i t is on ly i f we do no t d i s t in g u i s h

them th a t ce r ta in a rg u m e n ts f rom “ i l l u s i o n ” - w i l l seem

p laus ib le .

A y e r on C a u s a l T h e o r y

R eg a rd in g the C asu a l t h e o ry o f P e r c e p t io n Ayer w r i te s :

“The na tura l he ir to na ive rea l i sm is the casua l

th e o ry o f pe rcep t io n . It is to th is t h e o ry th a t

p eop le m os t c o m m o n ly tu rn w hen th e y have been

c o n v in ce d tha t the re are g ro u n d s fo r h o ld in g th a t

p h y s ica l ob jec ts are no t d i r e c t ly p e r c e iv e d

......................... Its s ta r t in g po in t is th a t sc ience

p roves tha t the o b je c t s w h ich we shou ld

o rd in a r i ly say tha t we p e rc e iv e d , the o b jec t s

w h ich c o n s t i tu te the c o lo u re d , n o i sy , r e d o le n t

w or ld o f com m on sense are very m u c h our own

c rea t ion . From th i s i t m ay be in fe r re d e i th e r tha t

these are not p h y s ic a l o b je c t s at all, or else , m ore

something there, and while the person concern sees that something in a sense wrongly, he need have no false beliefs about it.

com m onlv . that t h e \ are phys ica l o b je c t s in

d isgu ise On this view, though we pe rce iv e

phys ica l objec ts , we do not pe rce ive them in the i r

na tura l s ta tes They never appear in pub l ic u n ­

made up We cannot rem ove this m a k e -u p . s ince

our very p resence is r e sp o n s ib le for i ts be ing

there , but we can th e o r i t i c a l lv d i sco u n t it. We can

allow for the in f lu e n c e o f the m ed ium o f

ob se rv a t io n , and o f the ch a ra c te r and s i tu a t io n o f

the o b se rv e r And we can then work out w hat the

ob jec t must i t s e l f be like in o rder to have , in such

cond i t ions , the e f fe c t s on us that it does . It them

turns out to be ju s t w ha t s c ie n c e te l l s us tha t it is.

The fam ous d i s t in c t io n which Locke drew

between pr imary and s e co n d a ry q u a l i t i e s is no t a

d is t in c t io n between those p e rce iv ed q u a l i t i e s that

are una f fec ted by the co n d i t io n s o f o b s e rv a t io n

and those that are a f fec ted . S ince all are a f fec ted ,

there is no such d i s t in c t io n , as B e rk e le y rea l ized .

The p r im ary q u a l i t i e s o f the ob jec t , those that

l i t e ra l ly c h a ra c te r iz e it are on th is v iew , “j u s t

those p ro p e r t i e s with w hich sc ience c r e d i t s i t . ”g

Ayer. The Problem of Know ledge, pp 113- 4

52

The C ausa l th eo ry has a lw ays d e r iv e d m ost o f i ts

suppor t f rom the fac ts o f p h y s ic s and p h y s io lo g y . Don L ocke

h as d i s t in g u i s h e d b e tw e e n two d i f f e r e n t v e r s io n s o f th is

a rgum ent , w h ich he c a l le d - 'T h e casual a r g u m e n t ’ and ‘The

a rgum en t f rom p h y s i c s ’ . 10 So far as the f i r s t is c o n c e rn e d , it

has been show n tha t w h en we p e rce iv e th in g s c o m p l ic a te d

chains o f causa l ly c o n n e c te d ev en ts are in v o lv ed . S ee in g an

externa l o b je c t invo lves l ight w aves o f v a r io u s f r e q u e n c ie s

being r e f l e c te d by the o b je c t and im p in g in g on the re t in a ,

changes o ccu r r in g in the rods and cones o f the re t in a , an

e lec t r ica l im pulse being p a s se d a long the o p t ic nerve to the

optic cen tre o f the brain, and the c o n s e q u e n t s t im u la t io n o f

those cen t res . The see ing is a causa l c o n s e q u e n c e o f these

going-on as som eth ing p ro d u c e d in the mind by the

s t im u la t ion o f the o p t ic s c e n t r e s o f the b ra in . And th is , in

turn, is taken to show tha t w h a t we p e r c e iv e is not, as we

might think, the ob jec t i t se l f , bu t r a th e r an e f fec t o f various

p rocesses invo lv ing the ob jec t . It is no t a lw a y s held that this

e ffec t is a p ic tu re r e s e m b l in g or rep ro d u c in g the ex te rna l

object , in d eed the po in t o f the a rgum en t from physics is tha t

it does not.

10 Don Locke. Perception and Our Knowledge of the External World Ch VII

53

Objections to the Causal Theory

The s tan d a rd o b je c t io n ag a in s t th i s a rg u m e n t is th a t it

is s e l f - re fu t in g , in tha t i t m ak es the ve ry f a c t s on w h ic h the

a rgum en t and the t h e o ry are based u n k n o w a b le . F o r the

co n c lu s io n , th a t we a lw a y s p e rce iv e p e r c e p t s and n e v e r

pe rce ive phys ica l ob jec t s , m ean s tha t we can h av e no

k n o w ledge o f those v a r io u s cau sa l p r o c e s s e s to w h ic h the

a rgum ent re fe r s . In f a c t we canno t ev en know o f the

ex is tence o f ex te rna l ob jec t s . As B erk e le y says , "‘In shor t , i f

there were ex te rna l b o d ie s ' it is im p o ss ib le tha t we sh o u ld

ever com e to know it ; and i f the re w ere n o t we m igh t have

the very same reasons to th ink tha t th e re w ere tha t we have

no w ” 11 . The Causa l t h e o r i s t can avo id th i s d i f f i c u l ty o n ly by

t rea t ing ex te rna l o b je c t s as th e o r e t i c a l e n t i t i e s w h o s e

ex is tence is to be in fe r re d f rom w h a t we p e rce iv e . O ur

o rd ina ry ta lk about ex te rn a l o b je c t s has to be r e g a rd e d as an

e x p lan a to ry h y p o th e s i s in v o k ed to e x p la in h o w and w h y we

pe rce ive the p e r ce p ts we do. This m a k e s the a rg u m e n t s

c i rcu la r , in th a t we e s ta b l i s h the s c ie n t i f i c f a c t s by r e f e r e n c e

to our p e r c e p t s , and th en e s t a b l i s h tha t we p e rc e iv e p e r c e p t s

by re fe re n c e to the s c ie n t i f i c fac ts .

11 G. Berkeley. The Pinciples of Human Knowledge, I. sec. 20.

54

However , Hirst m a in ta ins that the Causal a rgum ent is

not ju s t c i rcu la r but s e l f con trad ic tory , because it begins by

citing facts that are involved in perce iv ing external ob jec ts

and ends by denying tha t we perce ive externa l ob jec ts at

all 12 But Don Locke th inks that th is ob jec t ion can be

avo ided .13 He says that the causal a rgum ent does not need to

assume that we perce ive external objec ts . We might

dis t inguish ‘d i r e c t ’ from ‘i n d i r e c t ’ pe rcep t ion , saying tha t to

perceive something ‘i n d i r e c t ly ’ is to pe rce ive not that th ing

but the sound it makes, i . e . ' I hear the w ate r only in so far as

I perceive its effect. It should be m en t ioned that the causal

theory is the theory that we never perce ive ex terna l o b jec ts

directly but only indirec tly , i.e. we perce ive them only in the

sense tha t we perceive the ir ef fects , the percep ts they

produce in our minds. But inspi te of the a t tem pts to de fend

it, the Causal theory seems to res t on the m is in te rp re ta t io n o f

facts, a m is in te rp re ta t ion due to a fa i lu re to d is t ingu ish

between percep t ion and w hat is perce ived .

The argument from Physics , m en t ioned already, re l ie s

on the a l leged fact that sc ience has shown, tha t the ex terna l

world is not at all as we pe rce ive it to be, and there fore that

* R.J. Hirst. The Problems of Perception, p. 172. 1' Don Locke, ibid, p. 114.

55

w hat we p e rc e iv e can n o t be p a r t s o f the e x te rn a l w or ld . Th is

a rgum en t is i n c o m p a t ib le w i th any R e p r e s e n ta t i v e T h e o ry , as

i ts whole p o in t is to show tha t w h a t r e a l ly ex i s t s is n o t a t all

l ike w h a t we pe rce ive . The a rg u m e n t is t h a t I p e r c e iv e a

so lid , c o lo u re d , s ta t io n a ry tab le bu t w h a t is r e a l ly th e re is a

d i sc o n t in u o u s m ass o f r a p id ly m o v in g n o n - c o l o u r e d i tem s , so

what I p e rc e iv e canno t be w h a t is r e a l ly th e re . S im i la r ly 1

perce ive a so u n d but w h a t is r e a l ly the re is a c e r ta in m o t io n

in the air. As Russe l l has pu t it . “N a iv e R ea l i sm le a d s to

phys ics , and phys ics , i f t rue , show s th a t N a iv e R ea l i sm is

false. T h e re fo re , Naive R ea l i sm , i f t rue , is f a l se ; t h e r e fo r e it

is f a l s e ” . 14 Th is a rg u m en t can be tu rn e d a g a in s t p h y s ic s : i f

naive R ea l i sm is fa lse th e n P h y s ic s is d e r iv e d f rom fa lse

a ssum pt ion . A d m i t ted ly th is d o es not sh o w th a t p h y s ic s is

fa lse , but i t does seem to d e s t ro y all r e a so n fo r r e g a rd in g it

as true. This in i t s e l f is s u f f i c i e n t to s u g g e s t tha t s o m e th in g

is w rong w i th the a r g u m en t f rom p h y s ic s . W h e n the p h y s i c i s t

says tha t the ta b le c o m p r i s e s o f a tom s, he c o n f u s e s the t a b le

w ith the a to m s o f w hich it is s a id to be c o n s t r u c t e d . To p o in t

out tha t the tab le c o n s i s t s o f im p e rc e p t ib l e e le m e n ts w h ic h

do move a ro u n d and w h ic h are s e p a ra te d by gaps is n o t to

deny any o f th is . I f by c a l l i n g the tab le so l id we m ean tha t

14 B. Russell, Inquiry into Meaning and Truth, p. 15.

56

no m at te r how c lose ly and by w h a te v e r m e a n s we ex a m in e it

we will n e v e r d i sco v e r any p a r t s s ep a ra te d by gaps , then

ph y s ic s has show n tha t the tab le is not so l id . But it is r a th e r

ex ag g e ra te d to sugges t t h a t th i s is w hat is m e a n t by c a l l i n g

the tab le so lid . All tha t we m ean is tha t so fa r as o rd in a ry

pe rcep t io n and o b se rv a t io n goes no gaps w il l be found , and

phys ics has no t shown th a t to be fa lse . The in v e s t ig a t io n o f

the p h y s ic i s t s have not c h a n g e d the na tu re or c o n s t ru c t io n o f

the world . P hys ics has n o t show n tha t ou r w ay s o f t a lk in g

about o b jec ts is false , bu t it has show n m o re c l e a r ly the

p rec ise w ay in which it is t r u e . 15

The C ausa l theory has n o t r e c e iv e d m u ch s u p p o r t f rom

p h i lo so p h e r s w ith an e m p i r i c i s t tu rn o f m ind . A v e r s io n o f

the theo ry , how ever , has been d e fe n d e d by H.P. G r ice in a

S y m p o s iu m .16 G r i c e ’s f o rm u la t io n o f the th eo ry is as

fo llows: (1) It is true t h a t X p e rc e iv e s M if, and o n ly if,

some p re sen t - tense sense - d a tu m s ta t e m e n t is t rue o f X

which re p o r t s a sta te o f a f f a i r s fo r w h ic h M, in a w ay to be

in d ica ted by exam ple , is c a u s a l ly r e s p o n s ib le , and (2) a c la im

15 Don Locke, Ibid, p. 120.16 Proceedings of the Aristotelian Society. Supp. Vol. 35(1961); Reprinted in G.J.Wamock (ed.) The philosophy of Perception.

An interesting article entiltled “The Causal Theory of Perception” written by John Hyman of Oxford has been published in The Philosophical Quarterly, volume 42. No. 168. 1992. An attempt has been made to plug the loop holes of the theory.

57

on the p a r t o f X to p e rc e iv e M, i f it n e e d s to be j u s t i f i e d at

all , is j u s t i f i e d by s h o w in g tha t the e x i s t e n c e o f M is

r eq u i red i f the c i r c u m s ta n c e s r e p o r t e d by c e r t a in t rue s e n se -

da tum s ta t e m e n ts , some o f w h ich may be a b o u t p e r s o n s o th e r

than X, are to be ca u sa l ly a c c o u n te d for. G r ic e says,

“F or an ob jec t to be p e r c e iv e d by X, it is s u f f i c i e n t tha t

it should be cau sa l ly i n v o lv e d in the g e n e r a t io n o f some

sense - im p re s s io n by X in the k ind o f w ay in w h ic h fo r

example , w h e n I look at my h a n d in g o o d l igh t , my h an d is

causa l ly r e sp o n s ib le for i t s ' l o o k i n g to me as i f the re w e re a

hand be fo re me, or in w h ich ...... (and so on) , w h a te v e r th a t

kind o f w ay may b e . ,,!/

Grice goes on to say tha t w h a t tha t w ay m ay be is a m a t t e r

for sp ec ia l is t s . But w hen I look at my h a n d in good l ig h t my

hand may no t be cau sa l ly r e s p o n s ib le fo r it l o o k in g to me as

i f there were a hand b e fo re me ; my e y e s ig h t may be bad , I

may be day - d ream in g and no t n o t ice the h an d , and n o n e o f

th is is a m a t t e r for the s p e c ia l i s t . A l t e r n a t iv e ly , my h an d m ay

be r e sp o n s ib le fo r it l o o k in g to me as i f t h e r e were a h a n d in

f ront o f me, but th is m ig h t s ti l l be a h a l lu c in a t io n , in c e r t a in

very spec ia l c i r c u m s ta n c e s w h e re the p r e s e n c e o f an o b je c t

before m y eyes br ings on the h a l lu c in a t io n . In o rd e r f o r my

1 Ibid, p. 105

58

hand to be c o n s id e re d c a u s a l ly r e sp o n s ib le fo r it l o o k in g to

me as i f th e re were a h a n d in f ro n t o f me and for th is to be a

case o f g en u in e p e rc e p t io n , a n u m b er o f n eg a t iv e c o n d i t i o n s

have to be fu l f i l l e d : the l igh t m us t not be bad, no r my v is io n

; I m ust no t be absen t m in d e d ; I m u s t n o t be h a v in g a

h a l lu c in a t io n , and so on. In o th e r w o rd s , the h an d w i l l be

r e sp o n s ib le fo r my p e r c e p t io n o f it o n ly u nder n o rm a l

cond i t ions . W i th o u t all th i s it is no t t rue t h a t “ for an o b je c t

to be p e rc e iv e d by X it is s u f f i c i e n t tha t i t sh o u ld be c a u s a l ly

involved in the gene ra t ion o f some sense - im p re s s io n by X ” .

though it is c lea r ly n e c e s sa ry tha t this s h o u ld be so. I f th i s

c r i t ic ism is va l id G r i c e ’s th e o ry n eeds m o d i f i c a t i o n ; bu t i ts

m o d i f ica t io n wil l rob it o f any c la im fo r b rea k in g new

g ro u n d .18 H ence , G r i c e ’s th e o ry has n o t m u ch to o f fe r by

way o f s o lu t io n o f the p ro b le m o f pe rcep t ion .*

A y er ’s View point

In b o th The P ro b le m o f k n o w le d g e an d the C e n t ra l

Q ues t ions o f P h i lo so p h y . A y er has o b je c te d to the v a l id i ty o f

18 D.W. Hamlvn. Theory of Knowledge, pp. 172-3.‘ In his book Perceiving (Ithaca. New York, 1957). R.M. Chisholm has specified the causal processes involved in sensory experiences, through the analysis of the actual processes involved in perception. This kind of approach appears irrelevant to our purpose.

59

the Causa l theo ry o f p e rc ep t io n . He has t aken in to

c o n s id e ra t io n the two s t r a n d s o f the a rg u m e n t - (1) th a t

s c ience c o r r e c t s the co m m o n sense p i c tu re o f the p h y s ic a l

w or ld , and (2) tha t the co m m o n sense p i c tu re is in an y case

un l ike ly to be accu ra te b e c a u s e o f i ts C a u s a l p r o v e n a n c e . In

d ea l ing w i th them he fo l lo w s s im i la r l ine o f r e a s o n in g w h ic h

we have ad v a n c e d by w ay o f c r i t i c i s m o f the Causa l theo ry .

Ayer , how ever , c o n c lu d e s tha t “ In i ts p u re ly s c ie n t i f i c

aspect the re need be no c o n f l i c t b e tw een C ausa l t h e o ry and

naive rea l ism . It is p o s s ib le to m a in ta in b o th tha t such th in g s

as cha i r s t ab le s are d i r e c t ly p e rc e iv ed and tha t our s e n se -

e x p e r ien ces are cau sa l ly d e p e n d e n t u p o n p h y s ic a l p r o c e s s e s

which are no t d i rec t ly p e r c e p t ib l e . Th is is, i n d ee d , a p o s i t i o n

w hich is very w ide ly h e ld and it is p e r f e c t l y c o n s i s t e n t ” . 19

There are two more p o in t s to be n o ted in A y e r ’s d i s c u s s io n .

One is tha t the causal th e o ry “ d ep en d s u p o n the a c c e p ta n c e

o f s c ien t i f ic theory : the c o n c lu s io n th a t th in g s are m os t

p ro b ab ly no t w ha t th e y s e e m ” .20 The o th e r is th a t “ O ur

c r i te r ia o f r e a l i ty have in the f i r s t in s t a n c e to be f r a m e d in

te rms o f the w ay th ings a p p e a r to us. We have n o th in g e lse to

go by. O n ly w h en we hav e c o n s t r u c t e d at l e a s t an e l e m e n ta ry

19 A.J. Ayer, The Problem of Knowledge, p. 116.20 A.J. Ayer. The Central Questions of Philosophy, p. 83.

p ic tu re o f the phys ica l w or ld , can we t h e o r i s e abou t it in a

way tha t m ay make such an a rg u m en t a c c e p ta b le . I f we do

accep t it, we w ou ld to use W i t t g e n s t e i n ’s sm i le , be t h ro w in g

away the l a d d e r up which we have c l i m b e d ” .21 Th is is in the

same sp ir i t as the s ta tem e n t f rom the P ro b lem o f P h i lo s o p h y

quo ted above.

60

-1 Ibid p. 88.