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CRITICAL REALISM Since the publication of Roy Bhaskar's A Realist Theory 0/ Science in 1 9 7 5 , critical realism has e
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Gilbert Harman The Philosophical Review, Vol. 79, No. 3. (Jul., 1970), pp. 404-419. Stable URL: http://links.jstor.org/
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Metaphysical Anti-? Ruth Garrett Millikan Mind, New Series, Vol. 95, No. 380. (Oct., 1986), pp. 417-431. Stable URL: htt
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Critical Realism This book introduces social scientists to the difference that critical realism can make to theorising
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SELLARS' CRITICAL REALISM In his "personal statement," in Contemporary American Philosophy, Roy Wood Sellars describes the orientation of his version of critical realism: Seeing the organism in its setting, I was led to think of perception as a selective interpretation of external things and t o break away completely from the subjectivistic tradition that ideas are the objects of knowledge. I tried t o work within the knowledge-claim and t o make i t pass from perception t o critical judgment. From the very first, I found i t impossible t o find satisfaction in any form of the new7 realism. Knowledge could not be the actual givenness of the object; the field of consciousness was not a passive collection of things capable of entering and leaving it. No; knowing was a unique activity involving mediations and claims and pointing beyond itself. It was as near to the things known as we could get. Representative realism must be re-analysed and cut loose from Cartesian dualism. I t was in this fashion that my particular brand of critical realism was born.'
This brand of critical realism, as I interpret it, has three parts: (I) a description of perceiving; (11) an account of the role of appearances in perceiving; and (111) a "materialistic" conception of appearance. In the present paper I shall examine this view critically. I believe that most of what Sellars has to say about perceiving and the role of appearances is true and important; but his "materialism" seems to me to be obscure.
The statement that "knowledge could not be the actual givenness of the object," which appears in the above quotation, was intended by Sellars to apply to perception. Because of his use of the expression "actual givenness," the statement may now be somewhat misleading; what he intended was, merely, that the objects we perceive are not identical with the "ideas," or appearances, by means of which me perceive them. The appearances of objects, unlike the objects themselves, are subjective effects of the perceptual process and depend upon the perceiving organism for their existence. I t had been assumed by many philosophers that this "subjective" conception of appearances implies that the perceiving organism perceives only its own ideas and never perceives external objects. The principal task of "Knowledge and its Categories," Sellars' contribution to the Essays in Critical Realism, was to show that this assumption is false. I t is now clear, I think, that Sellars was right. "Realism, Naturalism, and Humanism," Contemporary Avterican Philosophy, Volume Two, edited by G. P. Adams and W. P. Montague, pp. 265-266. Except where otherwise noted, all references are t o works by R. W. Sellars. 33
From the statement (I) He perceives a boat which appears green we may, if we do not object to a somewhat more awkward terminology, infer (2) He perceives a boat which takes on a green appearance for him. But it would be fallacious to infer, either from (I), or from (2), or from both. (3) He perceives a green appearance. Let us refer to the inference of (3) from (I), no matter whether the inference ~ fallacy, which is is via (2), as an instance of the sense-datum f ~ l l a c y .This often committed by psychologists and philosophers, leads readily to confusions. Perhaps the ~vorstof these-illustrated in terms of our example-is the tendency to infer, from (3), the contradictory of (I), via., (4) He does not perceive a boat. I t is quite apparent that (3) does not follow from (2) and that (4) does not follow from (3), or from (2), or from the conjunction of (3) and (2). Where, then, could philosophers and psychologists find the premises by means of which they could establish statements (3) and (4)? More often than not, when they believe themselves to establish such statements, they have reasoned as follows. Preferring the sense-datum terminology of statement (2) to the appearing terminology of (I), they note that the sensing of appearances is an indispensable condition of perceiving physical things; that is to say, they note that people would not perceive physical things unless the things took on appearances for them. They then note that appearances, unlike external physical things, exist only as effects of physiological and psychological processes. And, thirdly, they note that, occasionally at any rate, a perceiver can find out what kind of appearances he is sensing. Appealing to these facts, they then conclude that statements such as (3) and (4) are true. I t was characteristic of the critical realists to emphasize such facts and to charge the new realists with having ignored them. Yet-as Sellars recognized-if we add a description of these facts, in all their relevant detail, to statement (2) above, we find we still lack the premises needed to establish either (3) or (4). The assumption of such premises is not required by anything we need to say in describing perception; this assumption, Sellars has suggested, is "the primary mistake of the modern development of philo~ophy."~ Let us say, more generally, that one commits the sense-datum fallacy if one believes that, merely from statements describing how things appear and statements describing the causal conditions of appearing, one can infer that appearances are perceived or that no physical things are perceived. 2 Sellars does not use the expression "sense-datum fallacy." I have taken the term from H. A. Prichard (Knowledge and Perception, p. 213); Prichard's terminology is quite different from that used above, but his intent, I believe, is the same. "Knowledge and its Categories," Essays in Critical Realism, p. 189.
I t is possible that, if philosophers and psychologists avoided the sensedatum terminology of statement ( 2 ) and confined themselves to the appearing terminology of (I), they would be less likely to commit the fallacy. Nevertheless, the fallacy does not consist merely in the use of the sensedatum terminology; it is not fallacious to infer ( 2 ) from (I). Nor does the fallacy consist merely in making statements containing the same words as (3). Instead of using the word "perceives" in (1) and (2); we might have used another expression, say "has sensible knowledge of"; and instead of saying "The boat takes on a green appearance for him," we might have said, as Sellars sometimes does, "He intuits a green appearance of the boat." In this case the fallacy would consist in inferring "He has sensible knowledge of a green appearance." And if, like Prichard, we use "perceive" to express what Sellars has in mind when he uses "intuit," and if we continue to use "has sensible knowledge of" where we have used "perceive" above, then we may say "He perceives a green appearance" without committing the sense-datum fallacy. It was the sense-datum fallacy which, in Locke's philosophy, led to what Sellars has called "a reduction of perception to a mere awareness of sensory impressions appearance^]."^ Philosophers who describe perceiving as a "representative" process commit the fallacy when, having identified appearances with "ideas," they reason that one can perceive only one's own ideas; and when, having concluded that appearances or ideas are "pictures" of external things, they infer that what people perceive are pictures of things rather than the things themselves. And philosophers commit the fallacy when they assume it would be contradictory to say both (i) that appearances are "ideas" or subjective effects of physiological and psychological processes and (ii) that people perceive external things which exist independently of our perception of them. Another consideration, which may lead philosophers to commit the sensedatum fallacy and identify perceiving with the sensing of appearances, is the fact that it is very difficult to say what perceiving is. If we attempt to describe perceiving without using the word "perceive" in any of its forms, we will find, I think, that we must introduce some new technical term or provide a new interpretation or use for some other familiar term. H. H . Price, for example, introduced the terms "accept" and "present"; he then described perceiving as being, in its simplest form, "an undoubting acceptance of the existence of a material thing which presents itself to the mind bodily and as a whole. " 6 These uses of '[accept" and "present," as Price recognized, are rather special ones; it would be difficult to say what "accept" "A Statement of Critical Realism," Revue Internationale de Philosophie, Premiere annbe, No. 3, p. 484. 6 H. H. Price, Perception, p. 169.
and "present" mean, as Price uses them, without returning to "perceive." This difficulty is sometimes expressed, perhaps misleadingly, by saying, of the term "perception," that "it cannot be defined." Price's formulation may have the advantage, however, of underlying two important points. Perceiving, unlike believing, is an occurrence or event, rather than a tendency or disposition. And, although it is impossible to perceive that something has some property f without also believing that it is f, this occurrence or event is not merely the acquisition of the belief that the thing is f ; for a man may already believe that a thing is f and then perceive that it is. Sellars introduces a technical vocabulary which serves a purpose similar to that served by Price's vocabulary. Sellars borrows the linguistic term "denote" and uses "denotative selection" in place of "acceptance": I t is true that in perceiving we regard ourselves as in some fashion meaning and characterizing independent public things. May not this claim and belief be valid even though we must relinquish its more naive interpretation which identifies the sensory appearance with the thing meant and believed in? In that case we should need to distinguish between the intuition of the sensory appearance, which alone is given, and the denotative selection of a thing-object which is believed in and characterized. Denotative selection would be guided by the intuited sensory appearance but would not itself involve the entrance of the object into consciousness in a literal, intuitive way. By contrast with the sensory appearance the thing-object would be regarded as transcendent, as something to be affirmed and believed in and not given.6
(The expressions, "is intuited," "is given," and "enters into consciousness," which appear in this passage, should be taken, I think, as synonymous.) Sellars' motive for replacing "perceive" by "denote" may be suggested if we consider certain linguistic facts which might be said to "reflect" the process of perception. Sellars points out that "if we verbalized a perceptual experience we would stress a denoted object by means of a demonstrative adjective and then go on to characterize it"; if one wishes to understand perception, one must understand the role of "indicative words."? A perceptual belief-as distinguished from a belief which is notperceptualmay be expressed in statements wherein the object of perception is designated by demonstrative terms alone. A man who perceives a fox, or perceptually takes something to be a fox, can express his perceptual belief in the statement, "That is a fox," in which the word "that" functions purely "A Statement of Critical Realism," p. 474. I n place of "denote," Sellars sometimes uses "refer," "intend," or "affirm." 7 "A Statement of Critical Realism," p. 481; "The New Materialism," A Histor?/ of Philosophical Systems, edited by Vergilius Ferm, p. 419.
demonstratively; but he would be unable thus to use a demonstrative word if the object were not something he p e r c e i ~ e d . ~ If we avoid the word "perceive" and its synonyms and then attempt to describe perceiving in terms of appearing, believing, and the accompanying physiological processes, our description may seem to omit something. Sellars' technical term "denote," like Price's "accept," is evidently intended to designate what would be omitted in such a description. Some philosophers and psychologists have used the word "infer" with a similar intent. They have said that to perceive something is to "make an inference" or '(frame an hypothesis" about the causal conditions of appearing; to perceive a man walking, for example, is to "infer" that, or "frame the hypothesis'' that, one's sensory experience has been stimulated by a man walking. Interpreted literally and strictly, however, the "inferential theory" is obviously false: perceiving no more consists in speculating about the causal conditions of appearance than reading consists in speculating about the causal conditions of ink marks. A perceiver, on opening his eyes in the morning, cannot be said to "infer" that he is surrounded by familiar obobjects, or "frame the hypothesis" that these objects stimulate the appearances he is sensing-at least, not in the sense in which a man, reading his newspaper, may be said to "infer" or '(frame the hypothesis" that the cost of living will rise again. Use of the technical psychological terms "unconscious inference" and "interpretation," in this context, may serve only to obscure the fact that perceiving is not an inference, in the ordinary sense of the word "inferen~e."~ Occasionally Sellars uses a misleading terminology in describing perception. He suggests, at such times, that the "denotation" or '(affirmation" involved in perception can be described by reference to the concept of substitute or mistake. Of the physical objects we perceive, Sellars says that '(we tend to mistake our sensations for these things"; "a patch of color, for instance, is interpreted as the surface of a thing"; "analysis shows that the only literally intuited object is the sensory datum but that, in perceiving as such, it is given a context which makes the percipient regard it as an 8 One may, of course, also use a demonstrative term to designate something previously designated in the same discourse (e.g. '(There was an animal there yesterday and that was a fox") ; presumably such cases constitute exceptions to the above remark. 9 Compare "Knowledge and its Categories," p. 195; "Realism, Naturalism, and Humanism," pp. 266, 269; "A Statement of Critical Realism," pp. 475, 478; and "Current Realism," Philosophy Today, edited by E. L. Schaub, p. 33. I borrow the term "inferential theory" from D. J. B. Hawkins, Criticism of Experience, p. 87. Hawkins' book contains an excellent criticism of such theories.
PHILOSOPHY AND PHENOMENOLOGICSL RESEARCH
appearing thing."1° The expressions "mistake our sensations for," "interpret them as," and "regard them as," which I have italicized, have a rather special use in these passages. A man whose perception is unveridical might mistake a clump of trees for a house; in this case, it could be said that the object of perception is something which is really a clump of trees and that the perceiver mistakes it for a house. Sellars may seem to be saying that, even when a man veridically perceives a house, (i) the object of perception is something which is really an appearance and (ii) the man mistakes it for a house. That (i) is false, however, is indicated by Sellars own remarks, quoted above; "the primary mistake of the modern development of philosophy" is the assumption that appearances are the objects of perception. And if the object of perception is the house, and not the appearance of the house, then (ii) is also false. Hence, Sellars' use of "mistake for,', cannot be taken literally. Sometimes, instead of emphasizing the concept of mistake in this context, he emphasizes that of substitution. "May it not be that these sensible characters which are open to inspection and so readily taken to be literal aspects, surfaces, and inherent qualities of physical things are subjective substitutes for the corresponding parts of the physical world?"ll The word "substitute," it seems to me, is no better than "mistake." Normally if we say that man has substituted A for B, we may mean: that he has removed B and replaced it by A, or that he responds to A as he once respoilded to B, or that, when A is more readily available than B, he uses A, as next best, in the way in which he would like to use B. But Sellars does not mean to say that the perceiver has removed the object and replaced it by the appearance, or that the perceiver responds to the appearance as he once responded to the object. And since Sellars insists that physical things are the objects of perception, he cannot be interpreted as saying that physical things are not available to be perceived. I believe, therefore, that he might well have avoided the "mistake" and "substitute"; his philosophy can be adequately expressed without them.
The biological function of appearing-or of sensing appearances-is evidently that of helping the perceiver acquire true beliefs. In describing this function, Sellars makes use of the scholastic distinction between the "vehi~le,'~ or "content," of perception and the "object" of perception. Appearances are not the object of perception, but they are the vehicle or content of perception; "we look through them a t the object."12 A number "A Statement of Critical Realism," pp. 476, 478, 479; my italics. "Knowledge and its Categories," p. 191; my italics. Compare "Realism, Xaturalism, and Humanism," p. 271. l2 "Realism, Naturalism, and Humanism," p. 270. lo
of the critical realists had said that appearances "reveal" the "essence" of the object of perception. Sellars suggests an interpretation of this manner of speaking. I t is a way of saying that the content is relevant t o the object, that i t contains its structure, position, and changes. The situation is so basic t h a t it can hardly be further reduced. The content of knowledge offers us the fundamental categories, such as time, space, structure, relations, and behavior, in terms of which we think the world.13
There are two respects in which appearances may sometimes be relevant to, or adequate to, the objects of perception. (I) In characterizing appearances, Sellars stresses their dependence upon conditions of observation. By altering these conditions, a man may alter the appearance he senses; when he does this, "the appearance of a thing changes while the thing remains the same."14 By viewing the thing from different places, for instance, he can vary its visual appearances in a way which could be correlated with a series of photographs taken from the different places; hence "the analogy of the camera has point."15 The way in which a thing may thus be made to appear-or the type of appearanceman may thus be caused to sense-is conditioned in part by certain properties of the thing. These properties may be described in conditional statements of this form: "If a thing has . . . physical structure, then, if under . . . conditions, it sensibly stimulates a . . . perceiver, the perceiver will sense a . . . appearance." This type of statement describes the conditions under which a physical thing, functioning as a stimulus, serves as a causal condition of sensing. The language in which physical things are ordinarily described is sometimes ambiguous in that some of its terms (e.g. "red," "bitter," "warm," "sour") are used to perform two quite different functions-viz., that of referring to appearances and that of referring to the properties in virtue of which things are able to stimulate appearances. This ambiguity is, indirectly, an indication of one respect in which some appearances are "adequate" to physical things. The fact that a single word may thus be used to refer both to an appearance and to a property usually indicates that there is a significant correlation between the appearance and the perception of familiar things having the property. Leibniz remarked: we may say that a man feels warm and we may also say "that the heat belongs to the water of a bath, even though the water may seem cold to some; just as honey is called absolutely sweet, and silver white, even though the one appears bitter, the other yellow to some diseased persons; for the assignment of names is made upon the "Knowledge and its Categories," p. 200.
The Principles and Problems of Philosophy, p. 50. See Critical Realism, chapter 1.
1.5 "Realism, Naturalism, and Humanism," p. 268. l3
basis of the most usual conditions."16 The word "white," which is used to designate one of the properties of silver and of other physical things is also used to designate that type of appearance which such things, in virtue of that property, would normally be expected to stimulate. In such cases, there is a high correlation between the type of appearance sensed and the physical property which one perceives the object of perception to have. This, then, makes the appearance a reliable index of the property.17 This kind of adequacy is sometimes described, misleadingly, by saying that the appearance is a reliable sign of the property. The term "sign" is misleading because it suggests that the relation between an appearance and the object of perception is like that between the perception, say, of a cloud and the resultant hypothesis that it will rain. The cloud functions as a sign of rain partly because of the fact that perceptions of clouds have often been followed by perceptions of rain; but it cannot be in this sense that the appearance is a sign of the object, for the appearance is never perceived. (2) There is a second respect in which appearances may be adequate to the objects of perception. Complex appearances or groups of appearances may, on occasion, resemble such objects in significant ways. In the passage from the Essays in Critical Realism, quoted above, Sellars says that an appearance may have "a sort of revelatory identity with the object." Sellars usually stresses this type of adequacy rather than the former. If a man hears music under ordinary conditions, many of the relations holding among the appearances he senses will also hold among the sound waves which stimulate these appearances. If he hears the opening two measures of "The Star-Spangled Banner," there will be a set of appearances and a set of sound-waves, which are correlated in the following way. Each set has five successive members such that the first and the fifth are the same and the second and the fourth are the same. The members of each set l6 G, W. Leibniz, New Essays Concerning H u m a n Understanding, Book 11, Chapter VIII. Thomas Reid used the word "concomitance" in this connection; compare Essays o n the Intellectual Powers, Chapter 5, Section 2. l7 Compare C. I. Lewis, "Professor Chisholm and Empiricism," Journal of Philosophy, Vol. XLV (1948). Lewis notes t h a t , despite the fact that the appearances a man senses depend upon the conditions of observation, the following situation usually obtains in perception: "the given appearance may not be discernibly different from that of some other kind of object, under conditions other than those which actually affect this observation-so t h a t the appearance could 'deceive' us under conditions which, for all we know, may presently obtain-but because the condition which would lead t o this 'deception' is one which is exceptional, there is a high correlation between just this given character of the appearance and the objective property i t leads us to ascribe to the thing observed; in which case it remains the fact that the given appearance is a valid probability-index of the objective property" (Pp. 519-520).
belong to an order such that the second may be said to be three steps from the first and the fourth may be said to be four steps from the second and seven steps from the first. The two sets, in short, are structurally similar: the members of one may be so correlated with the members of the other, that for the relations holding among the first, there are relations, having the same formal properties, holding among the members of the second. Each of the sets are similarly related to the grooves in a phonograph record and to the marks in the printed music. Again: if a man is looking a t a flat object which has a complex shape, he may be able to find a point of view from which he can obtain an appearance having geometrical properties like those of the object. Similarly for the perception of other relations obtaining among physical things: if there are three houses in a field of vision and if the one in the middle is the smallest, then there are conditions under which the perceiver can obtain a complex appearance, or set of appearances, containing three components, or members, which are similarly related. There may be geometrical properties, moreover, which these components, or members, will share with the respective houses and not with each other. If the three components, or members, are similar in color, then they are, to that extent, qualitatively similar to each other; but if we said that they had the same color as the houses, we would be confusing the property use and the appearance use of color words. I t may be, however, that because of the first type of "adequacy" discussed above, the same color words are used to describe both the appearances and the houses. I t is quite possible, moreover, to perceive the three houses, still perceiving that one in the middle is the smallest, without sensing an appearance within which structurally similar relations hold. But under some conditions, the relations among appearances, or among the components of appearances, will be the same as some of those perceived to obtain among the objects of perception. Analogous considerations hold with respect to other sense-fields and with respect to the relations between one sense-field and another.I8 18 I have discussed the epistemological significance of structural similarity in "Pspchophysics and Structural Similarity," Revista Brasileira de FilosoJia, Vol. I (1951), pp. 31-35. The concept of structural similarity provides one plausible interpretation of Locke's doctrine that the ideas of primary qualities (primary qualities being "solidity, extension, figure, motion, or rest, and number") are resemblances of objects and "their patterns do exist in the bodies themselves." (Essay Concerning H u m a n Understanding, Book 11, Chapter 8, Section 13). But Locke's doctrine should be modified to say merely that sonze of the ideas of primary qualities are resemblances of the objects having such qualities. Compare Bertrand Russell, H u m a n Knowledge, Part IV, Chapters 3 and 4, and Part VI, Chapter 6, and Introduction to J!Iathemafical Philosophy, Chapter 6 ; Rudolf Carnap, Logische A u f b a u der W e l t , Sections 11-16. The concept of strurtural similarity seems t o have been central t o Aristotle's doctrine of "common sensibles"; compare De Ani?na, 418, 425, 428. See also Leibniz's N e w Essays i n Hurnnn llnderstanding, Book 11, Chapter 8.
It is important to emphasize that this interpretation of "revelatory identity" (possibly it is also the correct interpretation of "subjective substitute") does not involve the sense-datum fallacy. Philosophers who do commit this fallacy may readily be led, by considering structural similarity, to compare the appearances which a man senses with a map from which he "reads off" the characteristics of external things. The new realists had suggested that, according to the critical realists, appearances may be thought of as "a painter's canvas or a photographic plate on which objects in themselves imperceptible are represented."lg This suggestion is accurate to Sellars' philosophy only if the term "imperceptible" is replaced by "perceptible. " Sellars sometimes says that appearances, when they are adequate, correspond to the objects of perception. This locution is misleading, however, for one might take it to imply that a perceptual belief is true, or veridical, if and only if the appearances which occasion it correspond to the object of perception. But such correspondence is neither a necessary nor a sufficient condition for veridical perception. A man may perceive that the house in the foreground is smaller than the one in the background, even though the converse relation holds between the "corresponding" appearances; or he may perceive two houses, the appearance of the one being smaller than that of the other, and, a t the same time, have the false perceptual belief-or perceive unveridically-that the one house is not smaller than the other. I t may also be tempting to say that, whenever appearances are adequate, in either respect, to the things which are appearing, the things are "appearing the way they really are." But the phrase "appearing the way they really are" in this use, like the term "adequate," means merely that the appearances are related, in one of the two ways discussed, to the things that appear. And the phrase is misleading in this use, for-again-one is readily led to suppose, falsely, that "The thing appears the way it really is" means the same as "The perception of the thing is veridical" and that "The thing does not appear the way it really is" means the same as "The perception of the thing is unveridical or illusory." The terms "veridical" and "unveridical," however, apply not to appearances, or modes of appearing, but to what I have called the perceptual belief. I t is often thought that a critical realism, such as that of Sellars, must face the problem of "justifying our belief in the external world." This peculiar problem, as philosophers seem usually to understand it, may be formulated in the following way: if our premises pertain only to appearances, what justification can we have for saying that these appearances are adequate to physical things or for accepting any conclusion which pertains l*
E. B . Holt, et al., T h e New Realism, p . 4.
to physical things? (A comparable question is: if our premises pertain only t o what occurs a t the present time, what justification can we have for accepting any conclusion which pertains to the past?) The readiest answer, and perhaps the only answer, to an hypothetical question of this sort is a sceptical one: under the conditions envisaged in the antecedent, the beliefs described in the consequent would have n o significant justification. But, the hypothetical question does not constitute a problem for a philosopher unless he assumes that the conditions described in the antecedents actually obtain. A philosopher who had committed the sense-datum fallacy might be misled into making this assumption, but Sellars does not make it. And no one, so far as I know, has ever offered any good reason for making it. If we are concerned to justify a particular belief or judgment-about external objects or about any other subject-matter-the proper approach, Sellars says, is to ask what casts doubt on the truth-claim of a judgment. The doubt must be motivated and specific, otherwise we are merely doubting the ability of the human mind t o know. When I come t o analyse the situation, I find t h a t the human mind begins in perception t o interpret objects and t h a t difficulties merely force a critical reinterpretation of this first interpretation. The basic postulate is the claim t o know or, what amounts t o the same thing a t this level, the revelatory nature of our predicates. This postulate, if challenged, is confirmed by the success of our critical thinking. In other words, thought cures its own difficulties by showing how new distinctions satisfy old conflicts. The manner in which perceptual illusions are shown t o result from our position and from the nature of our sense-organs illustrates what I mean. Critical thinking is the only remedy for specifically motivated doubt. And this success of critical thinking can be indicated under four headings: (1) the consilience of established facts; (2) the logical coherence of ideas; (3) agreement of investigators; and (4) guidance and control over nature. These headings have been so often discussed t h a t there is no need t o go into detail. I t will be noted t h a t I assign a place t o both the logical and the larger pragmatic tests. But I am convinced t h a t the very advance of thought rests on the belief t h a t sense-perception is revelatory of nature and t h a t the proper use of i t enables us t o penetrate into the characteristics of the world. The logic of science gives, I think, the proper use of sense-perception.20
The content of Sellars' "basic postulate" about perception, might be reexpressed, I think, in this way: every perceptual belief is prima facie credible because of the fact that it i s a perceptual belief: If one takes a certain state of affairs to obtain, then this fact is, of itself, some justification for the belief that that state of affairs does obtain. The statement that perceptual beliefs do have this prima facie credibility is compatible with the statement that many such beliefs are false; we need not suppose that the system of statements expressing our beliefs must rest upon "incorrigible" or "ir"Realism, Naturalism, and Humanism," p. 272-273.
revocable" perceptual statements. And the fact that some of our perceptual beliefs are false-that some of our perceptions are unveridical--does not itself provide ground for challenging any particular perceptual belief; such occasion arises for a perceiver only when the particular belief has come into conflict with some one of his other beliefs. The assumption of the prima facie credibility of our perceptual beliefs, as Peirce pointed out, has an internal justification; for the beliefs we do have, including those about perception and the history of human errors, indicate that human beings have a tendency to make correct guesses and that the human mind is, in this respect, "strongly adapted to the comprehension of the world."21 I11
Sellars has formulated his "materialistic" conception of sensible appearances in the following way: Since neural events must have an intrinsic nature, why not accept the fact that this intrinsic nature rises t o a feeling-quale, say, in the thalamus and to discriminated data in the visual center? Conceptualization of this situation and the proper syntax need t o be worked out. The brain-event is not colored, as we say a surface is colored, but includes a color-sensation as a qualitative dimension, isolated in awareness.22
We may assume that appearances are instances of feeling-qwalia. Sellars does not say that appearances are identical with brain-events; he says, rather, that they are identical with qualitative dimensions which are included within brain-events. The questions posed by this version of "materialism," therefore, are the following: (1) what does Sellars mean by his expression "the qualitative dimension of a brain-event"; (2) what is his justification for supposing that brain-events include "qualitative dimensions"; and (3) what is his justification for identifying appearances, or feeling-qualia, with such "dimensions"? (1) In place of the term "qualitative dimension," Sellars sometimes uses other technical philosophical terms, but, so far as I am aware, he does not attempt to explicate these terms in a non-technical vocabulary. There is, he says, a "dimension of being which external knowledge could not reveal to the observer"; not only the brain but "every physical system has what we may metaphorically call a life of its own."23Sometimes he uses the words "inside" and " 'inness' "; "all sensory data are in the brain of the obC. S. Peirce, Collected Papers, 6.417. Compare H. H. Price, Perception, pp. 139 ff. "The New Materialism," p. 426. 23 "Realism, Naturalism, and Humanism," p. 279; "An Analytic Approach to the Mind-Body Problem," Philosophical Review, Vol. XLVII (1938), p. 471. Compare the Philosophy of Physical Realism, pp. 308-310. 21 g2
server."" The cerebellum and its parts are also in the brain but it doesn't seem to be quite in this sense that sensible appearances, according to Sellars, can be said to be in the brain.26The term "metaphysical insides" may thus suggest itself. I suspect that Sellars' answer to our first question would be this: the expression "qualitative dimension" is one which can be defined only by using some technical philosophical term in the defmiens; but the concept it expresses is one to which we are led if we attempt to provide an adequate description of any material thing. This answer would lead us, then, to the second of our questions. (2) What justification is there for supposing that brain-events include "qualitative dimensions" or "lives of their own"? Sellars offers no reasons for this supposition, I believe, beyond saying that it is certain; he says, in the passage quoted above, that neural events must have an intrinsic nature and he says, in the Philosophy of Physical Realism, that "it is certain that being must have its content, what we call by analogy its Erlebnis~e."~~ But if Sellars would answer the first question in the way I have suggested, we do not yet know what a qualitative dimension is and hence we cannot yet know whether things must have such dimensions. Other philosophers have offered dialectical arguments intended to show that things have qualitative dimensions. Sellars' own arguments, we may assume, would be similarly to the best of these. I know of two such arguments, each of which, it seems to me, is inconclusive. (a) The first of these arguments may be formulated as follows: "After the physical scientist has told us all he can know about the attributes or characteristics of a thing, we may still ask: what is the it to which these attributes or characteristics belong?g This it must possess, in addition to its (ordinary) attributes or characteristics, an inner nature of its own. Otherwise it would be a vacuous entity; it would not have the means of possessing any attributes and, moreover, there would be no sufficient reason why it should possess one attribute rather than another." But, if the reasoning of this argument is sound, then one may go on to ask "And, now, what is the Z4 ''An Analytic Approach to the Mind-Body Problem," p. 471; "Realism, Naturalism, and Humanism," p. 277. 26 Compare Leibniz' Monadology, f 17: "Supposing that there were a machine whose structure produced thought, sensation, and perception, we could conceive i t as increased in size with the same proportions until one was able t o enter into its interior, as he would into a mill. Now, on going into it he would find only pieces working upon another, but never would he find anything t o explain Perception. . . ." 26 "The New Materialism," p. 426; Philosophy of Physical Realism, p. 308. I have italicized "must" and "certain." 27 Compare A. E. Taylor, Elements of Metaphysics, p. 128: "Now, what do we understand by the.it to which these numerous attributes are alike ascribed and how does i t possess them?"
it which possesses this inner nature, e t ~ . ? The " ~ ~original question, however, seems to be misconceived; for, surely, to the question "What characteristics or properties do things have in addition to the characteristics or properties which they have?" the answer is "None whatever." Moreover, Sellars' comments on Locke's doctrine of substance-Locke's "mythical notion of support7'-would seem to indicate that Sellars would not make use of this argument .29 (b) Another argument, leading to the concept of inner nature, or qualitative dimension, is this: "(i) Ordinarily, if we say of a physical thing that it has a certain characteristic (e.g. that it weighs a pound), our statement may be translated into one which states that the thing bears a certain relation to some other thing having some other characteristic (e.g. that the first thing would have such-and-such an effect if placed on a standard scale); and if we say of two or more things that they stand in a certain relation (e.g. that one is on the surface of the other), our statement may be translated into one which states that the things stand in another relation to still another thing (e.g. that there is no room for a third thing to be placed between the two things). Hence (ii) it may be said, with respect to the (ordinary) characteristics of any given physical thing, that each such characteristic is constituted by some other characteristic of some other physical thing. (iii) Hence, if there are things having characteristics, then there are things having an inner nature, or a nature an sich, which is not constituted by characteristics of other things. (iv) But there are things having characteristics. Therefore, (v) some things (or, perhaps, all things) have an inner nature, or a nature an sich." Interpreting the term "translate" in premise (i) somewhat liberally, we may assent to (i), I think. The weak points of the argument, it seems to me, are premises (ii) and (iii). There is no way of proving, I believe, that (ii) follows logically from (i) or that (ii) is true. Premise (iii) has its analogue in the Prime Mover argument; whatever may be said about the latter can be applied, I suppose, to the former. (3) Our final question is: what justification is there for identifying sensible appearances with the "qualitative dimensions," or "inner natures," of brain-events? If, in identifying appearances with such "dimensions," Sellars were (i) to commit the sense-datum fallacy, (ii) to ignore the distinction between the property and appearance uses of words; and (iii) to view perceiving as a process of inference, the results would be extraordinarily paradoxical. Thomas Case, a nineteenth century proponent of "physical realism," evidently made all of these mistakes. He suggested that appearances could be identified with "physical parts of the nervous system, Compare F. H. Bradley, Appearance and Reality, Chapter 2. "Verification of Categories: Existence and Substance," Journal of Philosophy, Vol. XL (1943), p. 201. 28 29
tactile, optic, auditory, etc., sensibly affected in various manners." Assuming that people perceive appearances he was then able to infer that they perceive, not external physical things, but the insides of their own bodies. "The hot felt is the tactile nerves heated, the white seen is the optic nerves so colored." And then he argued that, on the basis of what people perceive of their nervous systems, they make inferences and hypotheses about what Case's goes on outside: "from the hot within we infer a fire "physical realism" was easily parodied. Bradley, for example, said that, according to Case, "when I smell a smell, I am aware of the stinking state of my own nervous system."31 But Sellars makes none of the mistakes I have attributed to Case; in consequence, Sellars' "physical realism" is far less paradoxical than that of Case. Sellars' answer to question (3) has some plausibility, I think, if we can accept his answers to (1) and (2), and if, further, there is reason to suppose that, for every type of appearance a man senses there is a type of brainevent which is exemplified when and only when the type of appearance is exemplified. For, if these conditions obtain, then perhaps there is no good reason for refusing to identify sensible appearances with the "inner natures'' of brain-events. RODERICK M. CHISHOLM. Thomas Case, Physical Realism, pp. 33, 24, 25. Quoted in Price's Perception, p. 127. Compare Lovejoy's criticism of Russell (whose view, although formulated paradoxically, is similar to that of Sellars) : Russell's theory "would apparently require us to hold that when (as we say) a surgeon uncovers a tumor in another man's head, he thereby produces a tumor in his own." A. 0.Lovejoy, Revolt Against Dualism, p. 237. 30