ayer on the causal theory of perception

Mind Association

Ayer on the Causal Theory of PerceptionAuthor(s): Clement DoreSource: Mind, New Series, Vol. 73, No. 290 (Apr., 1964), pp. 287-290Published by: Oxford University Press on behalf of the Mind AssociationStable URL: http://www.jstor.org/stable/2251822 .

Accessed: 24/06/2014 22:28

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp

.JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact [email protected].

.

Oxford University Press and Mind Association are collaborating with JSTOR to digitize, preserve and extendaccess to Mind.

http://www.jstor.org

This content downloaded from 185.44.79.22 on Tue, 24 Jun 2014 22:28:24 PMAll use subject to JSTOR Terms and Conditions

http://www.jstor.org/action/showPublisher?publisherCode=oup

http://www.jstor.org/action/showPublisher?publisherCode=mind

http://www.jstor.org/stable/2251822?origin=JSTOR-pdf

http://www.jstor.org/page/info/about/policies/terms.jsp


AYER ON THE CAUSAL THEORY OF PERCEPTION

IN The Problem of Knowledge Professor Ayer writes that it may well be that " the causal theory is vindicated to the extent that we are permitted to think of our sense-experiences as having the objects envisaged by scientists for their external causes; but it ... fails as a theory of perception ".1 By " a theory of perception " Ayer means a theory of the meaning of our perceptual judgments.2 More specifically, what he appears to have in mind is the theory that for one to say that he is perceiving a certain object is, in part, for him to say that he is having sense-experiences among the causes of which is the object which he says that he is perceiving. And what he appears to be claiming is that scientific accounts of the causation of our sense-experiences do not embody or entail such a theory. In this note I shall not dispute Ayer's contention that the sciences of perception do not embody or entail a theory about what everybody means when he says that he is perceiving a certain object. I shall, however, be concerned to call into question a certain thesis which might be thought to be implied by Ayer's comments on the causal theory-the thesis that no one (or hardly anyone) who accepted the scientific account of perception would also accept that the above- mentioned causal analysis of perceiving an object was accurate for his concept of perception. I shall try to indicate, that is to say, that it is highly implausible that no one who accepted the scientific explanation of our sense-experiences would think it inconsistent of himself to say both that he is perceiving a certain object and that that object is not among the causes of his sense-experiences.

We may start by supposing that by " the objects envisaged by scientists as the external causes of our sense-experiences " Ayer had intended to refer to at least some commonly perceived objects such as the sun. And we may ask whether it is plausible that one who says that the sun causes certain sense-experiences whenever we perceive the sun would be thought to be making a contingently true statement by anyone who accepted what he said. Now anyone who held that the utterance in question made a statement which was only contingently true would logically commit himself to one of the two following propositions: (1) that perceiving the sun as one thing and having sense-experiences caused by the sun is quite another, though the former is the effect of having sense-experiences which in turn are caused by the sun; (2) that perceiving the sun just is having certain sense-experiences which happen to be caused by the sun. But surely not everyone who accepted the utterance, " The sun is a cause of our having certain sense-experiences whenever we perceive the sun " would also accept (1). At least most thinkers who find it convenient to use the sense-experience terminology

1 A. J. Ayer, The Problem of Knowledge (London: Penguin Books, 1956), p. 115.

2 Ibid. p. 116.

287



288 C. DORE:

(including Professor Ayer) understand the term " sense-experience" in such a way that it is a logically necessary condition of anyone's perceiving the sun (or anything else) that he be having certain sense- experiences. Hence, these thinkers would refuse to say that having sense-experiences is in all instances an altogether different thing from perceiving the sun. But this would commit them to the view that it makes no sense to say that the sense-experiences which one has when he perceives the sun are a cause of one's perceiving the sull. For one who says that perceiving the sun is, at least in part, having certain sense-experiences and that these very sense-experiences are a cause of perceiving the sun says, in effect, that perceiving the sun is, at least in part, a cause of itself. Nor is it plausible to suppose that everyone who accepted the utterance in question would accept (2). For if it is really a contingent proposition that to perceive the sun is to have certain sense-experiences and for the sun to be a cause of them, then it is conceivable that to perceive the sun is to have sense- experiences which are caused by the moon or by the Empire State Building or, indeed, by any object which it might please one to pick out. And surely not everybody who accepted the utterance, " The sun is a cause of our having sense-experiences whenever we perceive the sun " wouldwish to commit himself to the position that such a thing is conceivable. Hence, it appears that not everyone who accepted the utterance would take it as making a contingently true statement. And, indeed, it is plausible that at least many people who accepted it would not do so. But now it is highly unlikely that very many thinkers would, when they said that they perceived the sun, mean that they were having certain sense-experiences caused by the sun but would not, when they said that they perceived some other object-say, the moon-mean that they were having certain other sense-experiences caused by that object. It is likely that if a causal analysis of someone's concept of the perception of one object is accurate, then a causal analysis of his concept of the perception of any other object will also be accurate. I think that these considerations make it clear that Ayer is mistaken if he holds that no one, or hardly anyone, who accepted an explanation of our sense-experiences formulated in words used to refer to the objects envisaged by scientists would accept a causal definition of " perceive ". Or, anyway, it is clear that Ayer would be mistaken if he meant to refer to observable objects by the expression " objects envisaged by scientists".

But in fact Ayer evidently does not mean to refer to any observable objects by the use of that expression. For he considers it relevant to his claim that the scientific account of perception does not give rise to a causal definition of perception that " we could give up all of current physical theory ... while at the same time maintaining the truth of statements which affirm the existence of physical objects which we claim to perceive ".3 By " the objects envisaged by science " Ayer presumably means those talked about in what he

3Ibid. p. 116.



AYER ON CAUSAL THEORY OF PERCEPTION 289

calls " physical theory " and since he says that we could give all of this up without abandoning any statements about objects which we claim to perceive, it seems likely that none of the objects mentioned in the explanation of sense-experience which Ayer is envisaging are observable objects. This interpretation is substantiated by the fact that Ayer mentions atoms and electrons as examples of such objects.

Now I know of no scientific explanation of perception which refers only to unobservable objects. (Such an explanation would not refer to nerve cells, for example, since they can be observed with the aid of a microscope.) Nonetheless, I will not dispute that any such scientific explanation of sense-experiences as Ayer appears to envisage has ever, in fact, been given or that, if one has not been given, there is any point in trying to formulate such an explanation. Nor will I dwell on the question of what Ayer would say about scientific accounts of perception which do refer to observable objects. Rather, I wish to make the following two comments about the scientific theory of perception which Ayer seems to have in mind: (A) Ayer will have to say of the objects to which the theory refers that they are either in principle unobservable or that it is physically impossible to observe them or, finally, only that scientists are as yet unable to observe them. If he adopts the first of these three alterna- tives, he commits himself to the view that there are entities of which no one would ever, under any conceivable circumstances, say that they had been observed. And Ayer offers us no support for this thesis, which is surely in need of considerable defence. The second alternative, which is also in need of defence (a scientific defence which Ayer is not, perhaps, equipped to offer us), entails that Ayer's thesis is only contingently true-a weaker claim, I believe, than Ayer intends to make. And, if Ayer adopted the third alternative, he would be obliged to say only that he is reporting that it is in fact the case at present that we could give up all of those parts of physical theory which are relevant to the explanation of sense-experience without admitting that we have not after all perceived any objects which we have ever claimed to perceive. And this, I suspect, is a much weaker claim than Ayer intends to make. (B) I think that it is indubitable that many people are disposed to say of atoms and electrons that they are parts of observable objects. Almost everyone who can remember his course in elementary chemistry will recall having been told by his teacher that, e.g. water is composed of hydro- gen and oxygen atoms and these in turn of electrons, among other particles. But now it would be absurd to say that atoms and electrons cause sense-experiences but that the observable objects which they compose do not. Hence, many people who accepted the statement that atoms and electrons cause sense-experiences would also accept the statement that observable objects do. Even if there is, or will be, a scientific explanation of sense-experience which mentions only unobservables such as atoms and electrons, many people who



290 C. DORE: AYER ON CAUSAL THEORY OF PERCEPTION

accepted it would ipso facto accept that sense-experiences are caused by observable objects. And considerations exactly similar to the ones set out earlier regarding perception of the sun indicate that a substantial number of the above-mentioned people would adopt a causal analysis of their perceptual concepts upon accepting the view that sense-experiences are caused by observable objects.

By maintaining that many people who agreed that atoms and electrons cause sense-experiences would ipso facto agree that observable objects do, I do not mean to imply that Ayer is mistaken in saying that we could consistently deny all of current scientific theory regarding atoms and electrons while refusing to deny any statements about observable objects. That we could do so is due to the fact that it is only contingently true that there are any atoms and electrons and that they combine in such a way as to form observable objects. But that this is so seems to me to be perfectly compatible with the claim that one commits himself to saying that observable objects cause sense-experiences if he holds that there are atoms and electrons, that they cause sense-experiences and that they are parts of observable objects. And I am at a loss to understand why Ayer should have thought otherwise.

Vanderbilt University CLEMENT DORE



ayer on the causal theory of perception

Documents