Physics and Ontology Gustav Bergmann Philosophy of Science, Vol. 28, No. 1. (Jan., 1961), pp. 1-14. Stable URL: http://links.jstor.org/sici?sici=0031-8248%28196101%2928%3A1%3C1%3APAO%3E2.0.CO%3B2-B Philosophy of Science is currently published by The University of Chicago Press.
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osophy of Science January, 1961
NO. I
PHYSICS AND ONTOLOGY* GUSTAV BERGMANN State University of Iowa T h e recent philosophy of physics is confronted with the new ontology, as it emerges after philosophy proper has fully articulated thc linguistic turn. T h e classical ontologists asserted or denied, controversially, that certain entities "existed." Rather than adding to these controversies, the new ontology uncovers their dialectics. The ontologically problematic entitics of physics are of two kinds, represented by forces and particles, respectively. T h e dialectics has been dominated by eight patterns. Two of these, independence and r,enlisin, belong to philosophy proper. T h e latter is here considered in order to relieve the philosophy of physics of a burden only philosophy proper can bear. That leaves six patterns: concreteizess (including the orbit feature), acquaintance, simplicity, significance, process, and model. T h e paper sketches how- each of these (nay be used and probably has been used, either explicitly or implicitly, in the recent controversies.
There is philosophy propev, also called first philosophy or metaphysics, and there are the several philosophies of something or other. A "philosophy of," if it is to remain just that, must not cut itself off from philosophy proper. Deliberate confrontations from time to time should help to avoid such fatal severancc. The heart of philosophy proper is ontology. For a while this insight was lost. Now it is being recovered. Thus it may help to confront some recent ontological thought with the recent philosophy of physics. This is what I propose t o do. But I cannot of course on this occasion offer more than the barest sketch or outline, just as 1 shall have to leave unsupported much of even the little I can say.l As to method, philosophy during the first half of the century has taken the
* Received September, 1960. Rcad, with some omissions, as part of a symposium at the 1960 International Congress for Logic, hlethodology and Philosophy of Science held at Stanford University. For supporting arguments, see Philosophy of Science (The Univcrsity of Wisconsin Press, 1957) and two volumes of cssays, Tlze Metaphysics of Logical Positivism (Longmans, Gr.:en and Company, 1954) and Nlcaning aizd Existence (The University of Wisconsin Press, 1959). Specially relevant, among older essays not included in the two collections, are the two pieces on the philosophy of physics in FI. Fcigl and M. Brodbeck (eds.), Readings in the Philosophy of Science (.4ppleton-Century-Crofts, 1953). Among recent essays, see "Ineffability, Ontology, and AIethod," Tlze Philosophical Review, 69, 1960, pp. 18-40 and "Dell'htto," Rivista d i Filosoj5n, 51, 1960, pp. 3-51. ("Acts," the original of the Italian piece, is now being published in The Iridi(m Journal of Philosophy, August and December, 1960.)
linguistic turn. Words are used either philosophically or commonsensically. Philosophical uses are literally unintelligible. T h e task is to explicate them by talking commonsensically about them. This is the fundamental idea of the turn. By now it has fully emerged. How, then, does it affect the emerging concern with ontology as the main content? Ontology ask what exists. This use of 'exist' is philosophical. An ontologist who has executed the linguistic turn will therefore not propose still another division of all entities imo existents and nonexistents. Rather, he will attempt to discern and state commonsensically the several and often conflicting intellectual motives which control the philosophical use of 'exist'. I just spoke of motix-es; I could instead have spoken of criteria. Both ~vords,though, motive and criterion, may seem to impute critical awareness where its absence often has been crucial. So I shall avoid both, speaking of patte~nsinstead. Of such patterns there are quite a few. Some I shall ignore or merely mention; to some others I shall attend. First, though, for the connection with physics. (When used commonsensically, 'exist' can always be replaced by 'there is (are)'. In this essay Y shall therefore noL use it at all except in order to mention the philosophical use. Other philosophicai uses I must mention I shall mark by double quotes when they first appear and whenever it seems necessary to avoid confusion. 'Ei~tity' has also been used philosophically. I use it here merely as an abbreviation, to avoid such commonsensical but tedious phrases as 'what an expression expresses or refers to'.) Are forces and particles "real" or are they merely (methodological) "fictions" ? At the time of Mach the par.ticles were atoms. Nowadays they are the many entities of subatomic physics; and one may wish to include the psis. Within the philosophy of physics this change from, say, Mach to the present gave rise to a nekt group of special problems. One cannot tackle them successfuliy unless he understands what has not changed at all. 'Real' and '5ction' in this question are used philosophically and exactly as a moment ago I used 'existcnt' and 'nonexistent'. That shows the conncction between ontology and the philosophy of physics. The question I borrowed from the tradition thus opens the ontological P ~ o b l e m a ~ of i k ~physics. Forces and particles have also been called "theoretical" entities. This adjective, too, is compromised by a philosophical past. So I shall avoid it, speaking instead of the problematic entities of physics. T h e problematic entities are very many. T h e patterns controlling the phi!osophical use of 'exist' are quite a few. Thus it may well be that the latter lead to a classification of the former, depending on which pattern or group of patterns is needed to clarify the status of the entity. Very roughly, there are t ~ v osuch classes. That is why I gave two illustrations, forces and particles. I shall first attend to the class represented by forces; then, after a digression about phenomenalism and realism, to that represented by particles. What exists exists "independently." This is the independence pattern. T h e 2 D;e PvoBI~mntzk,In problema~ica,lo p~obl&nzatiqzte are handy nouns French. I often wssh we had their equivalent xn English.
17
German, Itaissn, and
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use of 'independent' is philosophical. According to one explication, only facts can be indegendent; according to another, only things may be. T h e alternative marks the deepest dividing line in the ontological tradition. That is why 3: mention it. But it has not affected the recent philosophy of physics. With but few exceptions, such as Whitehead's eventism, its practitioners are all implicit thing ontologists. That is why I shall say no more about this pattern. What exists is what is "in" space and time. This is the formula of the cnnmeteness pattern. As the crucial word is used, physical objects are in physical space and time; sensa, in phenomenal space and time. T h e pattern does therefore not commit one to either materialism or phenomenalism. On the other hand, properties and relations exemplified by either physical okijects or sensa are not literally in space and time; either physical, in the case of the former; or phenomenal, in the case of the latter. That spots the place of the complex we can ~ concreteness pattern in the nominalism ~ o m p l e x .This again ignore. One subpattern or component of the pattern, though, has been very important recently. Physical objects move in orbits. As some put it, that is indeed part of the notion of a physical object. Call this the orbit subpattern. Literally, the modern particles have no orbits. Everyone is familiar with the disturbance this feature has created. We cannot know anything to exist unless we are "acquainted" either with it or with a part of it or, ~vhollpor in part, with a thing of its sort. This is the formula of the acqzlaintance pattern. Its flavor is epistemological. I n one sense, ontology and epistemology can indeed not be disentangled; in another, dialectically, they can. This I here take for granted.4 The phrase to be explicated is, of course, 'being acquainted'. We are acquainted with what we perceive, or, synonymously, with perceptual things, i.e., with perceptual objects, such as stones and chairs, and with some of the characters they exemplify, such as colors, shapes, and distance, That is one explication. Upon another explication, we are acquainted only with what we are directly aware of; direct awareness being of phenomenal entities, i.e., such things as sensa and the characters they exemplify on the one hand and, on the other, mental acts such as perceiving, remembering, thinking, and, of course, direct awareness itself. The dialectics of this alternative, perception versus direct awareness, has dominated much of the tradition. Made fully explicit, it can be confined to philosophy proper. Implicitly, from Mach to Einstein, it has profoundly affected the Probtenzatik of the particle. Retain, then, for future reference, that in this context I called stones and chairs perceptual rather than physical objects. Some entities are "simples"; all others "consist" of simples; the former exist; the latter don't. This is the simplicity patter%. What is a simple ? What does it mean for a thing to consist of others ? T h e formula, we see, contains Concerning the place of the independence pattern in the nominalism complex, see Edwin 13. Allaire, "Existence, Independence, and Universals," The P/zilosophical Review, 69, 1960, pp. 485496. T o r argumcnt, see my special review of Strawson's "Individuals," The Jozirnal of Plzilosof~hy, 57, 1960, pp. 601-622.
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GUSTAV BERGlVIANN
two philo~cphicaluses. Each has produced a huge body of dialectics. I call them two bodies rather than one because up to a point one can examine each separately. T o understand that, consider that one may disagree as to whether the "simples" are phenomenal, or perceptual, or even more fundamentally, whether they are facts or things, and yet agree on what it means for one entity to "consist" of others. I n our subject the dialectics of consisting looms large, that of simplicity doesn't. So I shall ignore the latter, except for a digression that will permit me to complete the ontological schema as well as to relieve the dryness of the catalogue by at least a fragment of argument. (One may accept the fundamental idea o i the linguistic turn concerning the proper method without accepting another, concerning the proper technique. I accept both. '6he proper technique, expedient for all purposes, indispensable for some, is to talk comn~onsensicallyabout a schema called the ideal language (IL). T h e HI, I propose is built around a syntactical dichotomy called logicaldescriptive. I n the I L there are logical features, signs, and truths. 'l'he shapes expressing the type distinctions are among the logical features; the connectives and the quantifiers, among the logical signs. T h e explication of "analytic" rests on the logical truths.) T h e philosophical uses of 'simple' are all misguided; attempts at explicatirg them show that none has a retrievable and important common-sense core. This is what the holists believe. If they are right, then H should not have listed the simplicity pattern. Since holism is now again fashionable, I shall in four steps sketch a partial defense of that pattern, exhibiting the role it plays in a crucial dichotomy which even some modern holists wish to preserve. 1. Philosophers have long tried to distinguish the world's "form" from its
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sently, after having said what needs to be said here about "definition." 4. Putting 2 and 3 together makes the lesson obvious. T h e logical entities do not exist. That is the gist of 2. There are no logical simples. That is the gist of 3. The idea of "simplicity" is indeed a crucial ingredient of that of "existence." That is the lesson. I t concludes the d i g r e ~ s i o n . ~ An ectity "consists" of others if and only if the expression (of IL) referring to it can be defined in terms of expressions referring to those others. Structurally as well as historically, this is the dominant explication. T o understand why and how it serves one must understand the nature of definitions. Call the two sides of a definition its left and its right, with the definiendum appearing on the left. Call the entity to which the definiendum refers the defined entity; those of which it consists, the defining entities. This will save breath and do no harm. Notice next that one always defines a character, never an ~ b j e c t Let . ~ the left be 'x is a bay'; the right, 'x is a horse and x is tawny'. What we have defined is not an object but a character exemplified by all and only those objects which are horses as well as tawny. Now for the main point. T h e left side is no more nor less than an abbreviation for the right. Thus, the notion of definition is essentially metalinguistic. The insight is fundamental. One ~ l o u l dthink that it is also obvious. Yet when one reads what is being written one wonders. I t has at any rate three facets. First. Defined terms are eliminable. Second. T h e left and the right have by virtue of a notational convention the same referent. Third. One must not be misled by the circumstance that after a definition has been introduced, one may use the sentence which for the moment I call 'left if and only if right' as if it were a logical truth and not merely the reflection of a notational convention. T h e distinction is of the essence. For a notational convention does not express anything. A logical truth expresses part of the world's form. This is my cue for picking up a loose thread. Remember the objection 3 b above and consider the sentence 'not-p if and only if neither p nor p'. I t expresses a logical truth. Thus it is not merely the reflection of a notational convention. Technically, in mathematical logic, it may be treated as if it were a definition. I n the philosophy of logic and mathematics the distinction looms large. But we need not and must not pursue it on this occasion. T h e philosophy of physics is concerned with what exists rather than with what merely subsists. I n Newtonian mechanics force may be defined in terms of mass and acceWittgenstein, in the Tractatus and earlier, was greatly impressed by this piece of dialectics. Unfortunately, he also insisted that form was literally nothing and strained toward the view rejected in 3a. These two errors were among those that propelled him toward the views he propounded in the Investigations. See also two essays by Edwin B. Allaire in Analysis: "Tractatus 6.3751," 19, 1959, pp. 100-105, and "Types and Formation Rules: A Note on Tractatus 3.334," 21, 1960, pp. 14-16. Philosophers will also notice that in order to avoid the dialectics of particularity and individuality, I have avoided both 'particular' and 'individual', used the rather ambiguous and noncomrnital 'object' instead.
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leration. 'Mass' and 'force' may in turn be defined and therefore eliminated from the original definition. Continuing this descent, one may arrive at a right side mentioning only perceptual things (objects and characters). I n the light of these facts, do forces exist ? Some took the negative; some, the affirmative. We do not join the controversy, merely try to unravel the dialectic. I t depends on four patterns, simplicity, acquaintance, concreteness, and a fourth which I shall presently introduce. Those swayed by the simplicity pattern will of course take the negative. T h e role of the acquaintance pattern is not so unambiguous. Interpret it so that we are acquainted with what we perceive.' Everyone agrees that we perceive the defining entities. Do we perceive forces, densities, friction coefficients, and so on ? T h e answer is No. If one stops there, the pattern provides an argument for the negative. But there is a counterargument which amounts to an amendment of the pattern. Borrowing the explication of 'consist' from the simplicity pattern, this counterargument reminds us that the left and the right sides have literally the same referent. Then it points out that we admittedly perceive all the defining entities. I t concludes that, even though we do not perceive the defined entity, we are in the relevant sense acquainted with it. (Whether or not one moves on to broaden the use of 'perceive' so that we do perceive forces is merely a matter of words. T h e broad use, to be sure, would be rather technical. But that does not make it philosophical.) T o understand how the concreteness pattern comes in, remember first the definition of 'bay'. T h e entities exemplifying the defined character, bay, and those exemplifying the two defining characters, horse and tawny, are of the same kind, objects in space and time. This is a source of resistance against the simplicity pattern, particularly if one forgets, as one well might under the influence of nominalism which has been rampant for so long, that what this pattern denies is not that there are bays but, rather, that the character they exemplify exists. (Whether or not the two defining characters of the illustration are simple obviously does not affect the point.) I n the case of our problematic entities, the converse of these ideas becomes operative. These entities are either rather complex relational characters, exemplified not by a single object but jointly by several. Or, even more suspect to the implicit nominalist, they are characters of characters. Thus the concreteness pattern becomes plausible as an argument for the negative. A dejined entity exists if and only if it is significant; an entity being significant if and only if the expression referring to it occurs in statements of lawfulness which we have reason to believe are true. This is the significance pattern. By it, forces exist. That is again obvious. Something else, that should be obvious, nowadays isn't to some. Notice that I underlined 'defined' and 'referring'. A defined entity exists, and so on. Not just: an entity exists, and so on. If there is a definition, we know what the expression refers to. If there isn't, we do not know what we are talking about. Significance presupposes Just as the dialectics o f sirnplicitp and consisting can be separated, so for the point at hand it does not matter where xire actually peg the level o f acquaintance.
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reference. T h e holists deny that. That is why I do not know what they take us to be talking about, either in physics or elsewhere. That is my cue for the next point. Let 'x is soluble (in water)' stand for the left; 'If x is put into water, then x dissolves', for the right. Upon this definition of the disposition term, Carnap's famous match which has never been put into water is soluble. I n English, shifting to the subjunctive mode, 'if it were . . . then it would . . .', takes care of the awkwardness. Make the left If3(%)';the right jC,(x) 3f,(x)'. Now the shift requires the introduction of a new primitives sign, say 'C', making the right If,(x) Cf,(x)'. One sees now that the awkwardness is closely related to another. If one makes the closure of the conditional on the right, '(x)V;(x) 3f,(x)]', the paradigm of a law statement, then the difference between "lav~s" and "accidental generalities" is lost. Remember Chisholm's park bench in Boston Commons on which only Irishmen ever sat even though, had I sat on it, I would not be or have become an Irishman. These are the facts. What is the problem? T h e awkwardness arises only if one insists on transcription into I L . Such transcription is the proper technique of ontological inquiry. That suggests that the problem is ontological. There are three alternative ways of handling it. Before turning to them, let me in the law case show a further connection. Let 'N' be the primitive name of a descriptive (i.e., nonlogical) relation of the second type such that N(fl, f,)if and only iff, andf, are causally connected. This makes 'N(f,,f,) .- (x)lf,(x) 3f,(x)]' a synthetic truth or falsehood, depending on whether the generality is a law or accidental. N is in substance an Aristotelian nature. If the objects in question exemplify only two characters, then it literally is one. That supports the ontological diagnosis. T h e jirst alternative is to introduce 'C' as a primitive sign. Syntactically, 'C' is a quasirelation, i.e., a sign combining either sentences or sentences and terms into sentences. So is ' M , the primitive sign for the logical nexus of meaning, in one of the several meanings of 'meaning', which connects the mental characters I call propositions with the states of affairs, expressed by sentences, which they mean. Three comments will illuminate the situation that produces. I. T h e entity C is either logical or descriptive. If it is claimed to be descriptive, many will demur on the ground that they are not acquainted with it. 2. C must in fact be logical on structural grounds which lie much deeper than the acquaintance pattern. T o see that, consider a (binary) descriptive relation, r. I t is exemplified if and only if some sentence ' r ( a , b)' is true, which presupposes that the two objects called 'a' and 'by exist. T h e one and only thing one could plausibly mean by a descriptive quasirelation C being exemplified is, analogously, that some sentence 'p,Cp,' is true; 'p,' and 'p,' being two sentences referring to states of affairs. And it is part of the idea of a "descriptive" universal that it must malie sense to say of it that it is "exemIf 'C' itself is not primitive, its definiens will contain a primitive constituent n-hich is a quasirelation. Then the arguments apply to this constituent. The same goes for 'N' below.
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GUSTAV BERGMANN
plified." Now assume 'If a were f,, then a would be f2' to be true in a case where n is in fact neither. Transcribed, the sentence is of the form 'p,Cp,'. Hence, if 'C' is to ex?ress the causal nexus, this latter sentence would be true even though its two senterltial constituents are both false. T h e quasirelation would thus be "exemplified" by two nonobtaining states of affairs. This clashes with the very idea of a descriptive entity, or, what amounts to the same, with the idea of an existent. T o see that it does not so clash with the idea of a subsistent, one merely has to consider 'p, v p,'. I t makes no sense to speak of a logical entity, such as the quasirelation of conjunction, as being exemplified. Hence, there is no absurdity whatsoever in counting 'p, vp,' as true ill case either 'p,' or 'pi' is false.9 3. In case IL contains quasirelational primitives other than connectives and 'lM',the two interdependent dichotomies "logical-descriptive" and "analytic-synthetic" cannot be adequately explicated. At least, no such explication has as yet been proposed. Nor can I conceive even the vaguest idea of one. 'Fhe second alternative is to accept "implicit definitions."1° T h e simplest paradigm is yl(x) 3 [f2(x) f3(x)lY,the bilateral reduction sentence, B, by means of which Garnap has proposed to "introduce" the predicate jC,'. I n this context 'introduce' is anything but clear. Three comments will remove the blur. I. What is being introduced is not just If3' but also B. 2. B is not a logical truth (analytic). Thus it could not possibly in the language reflect a definition or notational stipulation about it. 3. Whether or not B is analytic, introducing it does not make 'f,' eliminable. I agree with those who conclude that upon this alternative one would therefore not know what one is talking about when using If3'. Reference is being sacrificed to significance in the manner of the holists. Oiie reason the alternative seems nevertheless attractive to some is that it reflects the way we try out a new concept. But then, to use Reichenbach's pretty phrase, the context of discovery is one thing, the context of justification is another. T o mistake the former for the latter is one of the hallmarks of holism. That confirms the diagnosis. T h e t h i ~ dalternative is to accept the awkwardness that the disposition terms cannot i~?, closed form and with anything approaching idiomatic accuracy be transcribed into IL. Such acceptance is made easy by considering what it amounts to in the law case. Upon this alternative, a law statement cannot as such in IL be distinguished from an accidental generality. Rather, the difference lies in the context, that is, first, in the success as a premise of the state-
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s As for 'v', so for ' M ' . Let 'p,' be the propositional character which means p,. M is a logical entity. Hence, there is no absurdity in "p,' AJp,' being true even though 'p,' be false. If one is a thing ontologist (i.e., no "fact" exists, irrespective of whether it be "true" or "false"), that solves the problem of false beliefs. This too shows, as does the argument in the text, that there is a stylistic discrepancy, to say the least, between the very idea of a thing ontology and that of primitive quasirelations. l o Frege as early as 1903 rejected the idea of implicit definitions as inherently and irremediably confused. T/?e Philosophicrcl Review (69, 1960, pp. 3-17) recently has earned our gratitude by printing an English translation of this impressive piece.
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ment we call a lati7 in those nontrivial cases where the match has bcen put into water, and, second, in its deductive connections with other such statements. A little reflection will show that this explication of the dieerence is but an upto-date formula~ionof I-luine's basic insight concerning causes, natures, and dispositiocs. That much for the kind of problematic entity represented by forces; I turn to that represeqted by particles. T h e particle exists. This is one alternative. I t doesn't exist, is merely a "construction" or "fiction." This the other. Commonsensically, we think of the particle as a kird of physical object. At least, we think or thought so of the particles of classical physics. That merely brushes aside what does not matter right now. I t also helps to explain why and how the realism-phenomenalisir issue, which belongs to philosophy proper, has so profoundly affected the status of the particle. Physical objectsll exist. That is the realist thesis. They don't exist. That is the phenomenalist contentiopl. Thus one may easily be led to argue that only a realist can consistently assert what a consistei~tphenomenalist must deny, namely, that the particle exists. T o appreciate the impact of the argument, remember Einstein. He made no secret of his intense dislike for "positivism." T h e positivism he knew was among other things a kind of phenotnenalism. Reading him, one discovers soon that the real object of his dislike ~irasjust that phenornemlalism. On the other hand, he was profoundly committed to the particle, even the classical particle.12 So he may plausibly have been s~vayedby the argument. Again, reading him shows that he was. So we better face the philosophical dialectic. I begin by introducing two commonsensical distinctions and a new pattern. What I perceive when I see a chair or a stone I call a perceptual object, not a physical object. My seeing the perceptual chair has causes. Science tells me what they are. One of them-there is no need to elaborate the familiar-I call the physical chair. Colors, sounds, and smells are all perceptual things. But they have not for several hundred years been thought of as physical things. That makes the point rather forcefully. So I shall not belabor it. Perceptz/al things versus physical things: that is the first distinction. T h e second is between perceptual and phenomenal things. Sensa, toothaches, awarenesses, and so on, are phenomenal objects; the characters they exemplify, phenomenal characters. That is how, commonsensically, I use 'phenomenal'. Others use 'mental' instead. T h e perceptual chair I see obviously is not a phenomenal thing. Perceptual things exist. This is the new pattern. I t states fairly what the realist wants to maintain. So I call it the realism pattern. Say instead "There are l1 More precisely, physicai things, i.e., either objects or characters (i.e., either properties or relations). T h e point must by now be obvious. So I follow here and elsewhere stylistic convenience. l 2 The story of the shadow this commitment cast on his later life is well known. See also my review of tile Einstein volume in T h e Library of Living Philosoplirrs. (The Plzilosophical Review, 60, 1951, pp. 268-74).
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perceptual things" and you have uttered a truism. T h e realist wants to say more. That shows that his use of 'exist' is philosophical. (That is why I speak of a pattern.) Presently I shall so explicate it that the pattern becomes true and commonsensical, though no longer truistic. But let us first look at the phenomenalist. T h e phenomenalist starts from the acquaintance pattern, explicates it so that to be acquainted with something is to be directly aware of it. Since the only things we are directly aware of are phenomenal things, he concludes that perceptual things do not exist. That is so absurd (however you may explicate 'exist') that we cannot but immediately ask two questions. What is the minimum the phenomenalist must claim to deserve a hearing ? What is the intellectual motive for his desperate gambit ? Starting from a class of definientia consisting only of sensa and some of their characters, which are all phenomenal things, one can define serviceable expressions for all perceptual things. This is the minimal claim. I t has been and still is controversial. How tenable it is depends on how one interprets 'serviceable'. With a reasonable interpretation it is tenable as well as strategically important. This, though, is only half of the story. T h e other half is that to grant the claim is the quickest way to dispose of phenomenalism. Remember what has been said about definitions. The left and the right have the same referent. Thus, a consistent phenomenalist must hold that a perceptual object is, literally, a congeries, however complex, of phenomenal things. That is his fatal weakness. T h e classical dialectic of perception revolves around two pivots. I perceive the tower to be round, the stick to be bent. Through further perceptions I come to know that the one is square, the other straight. There is perceptual error. This is one pivot. Veridical perceptions are not intrinsically distinct from others. T h e criteria are all contextu-al. This is the other pivot. T h e one and only way to master the dialectic is to grant in this context the phenomenalist's claim. That accounts for his intellectual motive. I t is also his formidable strength. Weakness and strength together have produced an agonizing stalemate. T h e way out leads through phenomenology. There are two kinds of phenomenal things; one I call pl&izavy; the other, in a narrower sense of the term, rizental. Sensa and their characters are among primary things. Mental things are either awarenesses, which are objects, or their characters. I am not directly aware of the ~erceptualobject. That is obvious. Nor am I in perceiving something directly aware of that mythical phenomenal object called a "percept." That, too, is obvious, although it has been temporarily obscured by what the classical realists in exasperation called the way of ideas. What happens when I am seeing the chair is, rather, that I am directly aware of an act, i.e., of an awareness and the two simple characters it exemplifies. One of the two is perceiving. (Others of this kind are remembering, thinking, doubting, and so on.) T h e best English name for the second character the awareness exemplifies is ' t h e proposition (that) this is a chair'. So I call it a propositional character.
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Both these characters are nonrelational.lJ 'I'hat gives the phenomenalist his due. T h e realist may take comfort from four other features. 1. Like pitches, hues, and all other simple phenomenal characters, the quality called perceiving is unmistakable and completely determinate. 2. T h e propositional character is simple. 3. T h e referential aspect of perception resides in the meaning nexus. This nexus is a logical quasirelation (Ad).I t connects a phenomenal entity (viz., the propositional character) with a perceptual one (viz., the fact which the propositional character means). T h e sentence expressing it, e.g., 'The proposition this is a chair ineans this a chair', is analytic. 4. Primary facts, e.g., a (phenomenal) spot's being green, are sensed, not perceived. T h e awareness in the case exemplifies sensing and the appropriate proposition. I n such cases, both terms ol the meaning nexus are phenomenal objects, one primary, one mental. Now remember the formula of the realism pattern: Perceptual things exist. 1 explicate this philosophical use of 'exist' so that it asserts those four features and nothing else. That makes the formula commonsensical, true, and anything but truistic. If some feel that it also makes me a realist, I shall not argue with them about the label, if only because I feel that none of the classical labels is worth arguing about. What is the import of all this for the status of the particle ? T h e classical particle is a kind of physical object. So I reword the question. What is the import of this phenomenologically chastened realism for the status of physical objects ? T h e gist of the answer is that it frees the philosophy of physics from the wrong kind of metaphysical pressure. If that is true, it is also important. So I must unpack it. T h e distinction between perceptual and physical objects is beginning to pay off. So I shall venture another. According to the phenomenalist, a perceptual thing is literally a congeries of phenomenal ones. That is often expressed, very aptly I think, by saying that upon this view all nonphenomenal things are constructions. A construction, in this sense, replaces an entity which does not exist by one which does (or by a congeries of such). That sounds and is paradoxical, since one can of course not replace what is not there. T h e paradox sets off the distinction I am about to make. Without paradox science replaces perceptual things, which do exist, by certain others, namely, physical things, which latter in the very nature of the case we cannot know to exist in exactly the same sense of 'knowing' in which we do know that perceptual things exist. I express this as follows. Neither perceptual nor physical things are constructions. Rather, the latter are reco~zstructionsof the former. T h e l 3 This part of my analysis has a certain similarity with the Aristotelian-Thomistic solution. T h e second feature preserves what is sound in the Kantian notion of the transcendental unity of apperception. T h e third feature is the heart of the matter. T h e fourth provides, as it were, a phenomenal model of perception. That makes it structurally, if perhaps not genetically, the deepest root of the idea of an external world. The deepest root of the classical phenomenalists' failure is that they either ignored or misconstrued the mental things or even denied that they exist. Concerning perceptual error, see fn. 9; for ample detail about all this, "Dell'Atto," 1.c.
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motive for reconstruction is of course scientific explanation; its oilly proper warranty, explanatory success. T h e new distinction is thus between construction and reconstruction. ?'he former is ontologically problematic, the latter is not. That is its point. I t takes the wrong kind of pressure off the philosophy of physics. Once this pressure is off, one can deal properly with those features of the particle which are peculiar to it and do need dialectical clarification. T o this, my last task, I now turn. First, though, for two comments. Several hundred years ago the perceptual object was so reconstructed that among other things it lost its colors. I t is well to realize that the resulting physical object is as unintuitive as a classical atom or a modern light quant. The difference, if any, is at most a matter of degree. This is the first comment. Some may feel that what 1 say is obsolete since nowadays we actually "see" individual particles. The answer is that what we see (perceive) is not the particle but, say, a flicker on a screen. Or we hear a counter tick. Those who are not sensitive to the difference that makes sirnply lack the kind of sensitivityt hat makes philosophers. So I shall not arguewith them, merely assure them that I arn as convinced as they are that there are particles. That is the second comment. Once more, does the particle exist ? Once more, I do not take sides, merely exhibit the dialectic. In the case of the classical particle, the a%rmative argument rests on two patterns. One ure already lrnow, the other 1 shall presently introduce. T h e classical particle is in time and space and has orbits. Except for its size, it is in these [undamzntal respects like a macro-object of classical physics (briefly: like a macro-object). Hence, by the concreteness pattern and its crucial orbit subpattern, the classical particle exists. ?'he basic entities of the cornprehensive process schema exist. This is the process pattern. I could have called it the "deterministic" or the "mechanistic" pattern. But the multiple ambiguity, including philosopliical uses, of these two words is ilotorious. So I avoid them. A schema (in physics) is connprehensive if and only if it explains all (physical) facts. The claim of cornprehensiveiless is of course always a matter of principle only, an expectation, or, if you do not object to the phrase, a frame ~f reference. T h e flavor of 'schema' conveys some of this idea. T h e notion of process is an abstraction from Newtonian point mechanics. Froin a complete state description in conjunction with the process lau (which is part of the schema) such descriptions of all earlier and later states can be deduced. Basic, finally, are those entities which in an axiomatization of tlie schema correspond to its undefined nonlogical terms.14 Consider now the physics of, say, 1900. For macro-objec~sthe limitation in some cases to statistical prediction was accepted. Atomistics, howl %T h e strength of the process pattern sliows itself in the classical dialectic of the mind-body nexus. I have never really understood the alleged distinction between epiphenomenalism and parallelism. All I can inalie out is this. T h e bodily series, as it is called in these discussions, is part of a cornprehensive process. T h e mental series neither is itself such a process nor can it plausibly be thought of as part of one. T h e epiphenomenalist, ztnde-r the impact of the process patterri, expresses this difference by calling mind "merely" an epiphenomenon. T h e parallelist shrinks from such verbal impeity.
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ever, served as a comprehensive process schema. The affirmative side, those arguing for the existence of the classical particle, could therefore appeal to the process schema. T h e record shows that either implicitly or explicitly they did. But, of course, not all went smoothly for long. It never does. So far, at least, every schema has had its crisis. T h e one ]I allude to is the crisis of ehermodynamics. I t marked, as we now understand, the transition to modern physics. Let us first look at the negative side in the dialectic of the classical particle. T h e entities of the model do not exist. This is the formula of the model pattern. I t underlies much that has been said on the negative side. T o understand it, one must understand this use of 'model'. T o understand this use, one must attend to a characteristic feature of all particles, classical as well as modern. I n describing the feature I shall without further explanation speak of two languages and of translations from one into the other. No harm will be done and much breath will be saved. T h e particles (micro-objects) must of course be "tied" to the (physical) macro-objects. (The latter are in turn "tied" to the perceptual objects. This, after what has been said, we may take for granted.) T h e macrolanguage rnentions only macro-objects; the microlangugae, only micro-objects. T h e characteristic feature is that while every sentence of the macrolanguage is in principle translatable into the microlangugae, translations in the opposite direction are not available for all sentences but only for some. This state of affairs is very neatly described by saying that one may first develop the anicrolanguage as an uninterpreted calculus, then establish the required tie by "coordinating" some of its expressions to expressions of the macrolanguage. Hence the phrase: coordinating definitions.15 Another phrase often used is: partial interpretation (of a calculus or model). That explains the relevant use of 'model'. T h e idea is this. As the vicissitudes of explanation require, one language which as such we do not understand, namely, that of the model, may be either attached to or detached from another permanent one, which we do understand, namely, that of the macro-objects. I t is not hard to see how this idea may lead one to deny that the entities of the model exist. Hence the impact of the pattern. Yet, in classical physics it is easily challenged. Natural and convenient as it is, the model way is not the only one of describing the situation. A classical particle is merely a macro-object reduced in size or scale. Such scale reduction is a purely arithmetical notion. Thus it is available to us as a part of the world's subsistent form. Hence particles (i.e., the predicate 'particle'; remember the bay horse!) can be defined as a kind of physical object.16 Once the notion has thus become available, one can in the l5 AS far as I know, the phrase is Reichenbach's. It will do no harm as long as one realizes that these "coordinations" are not really definitions. For a very thorough analysis of the several ways 'model' has been used by scientists and philosophers of science, see M. Brodbeck, "Models Meaning, and Theories," in L. Gross (ed.), Synzposium on Sociological Theory (Row, Peterson and Company, 1959), pp. 373-406. l6 For a more detailed statement of this point, see "The Logic of Psychological Concepts," P/zilosophy of Sciezce, 18, 1951, pp. 93-110. The reconstruction may in this case not unreasonably be called an existe~ztialhypothesis. I mention the phrase because it is being used by old-style realists, such as Feigl. The way they use it, it is ontologically problematic; the way I just
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familiar fashion reconstruct the macro-object as a swarm or flock of microobjects. I n classical physics this alternative balances the arguments based on the model pattern. T h e modern particle, however, is not just a macro-object reduced in size. That of course affects the balance. Among the novel features of the modern particle two stand out. For one, it has in principle no orbit. That greatly weakens, if it does not altogether destroy, the usefulness of the concreteness pattern for those who want to argue that the particle exists. For another, the limitation to statistical prediction has, as it were, penetrated into the world of the particle. I n classical physics the limitation applied only to some macrosituations. I n modern physics a11 predictions about position and speed of the individual particle are in principle statistical. Tbat deprives the arguments which draw upon the process pattern of their ground. But there is a twist here. T h e way the statistical predictions are achieved is most naturally and conveniently described in the model way. By means of very intricate translation rules a further calculus or model is attached to the properly modified atomic model. T h e advantage of this description is that it resolves all so-called paradoxes. T h e twist is that the second model, which is of course quantum mechanics, is again a process schema for which comprehensiveness may reasonably be claimed. Tlius, by the process pattern, its basic entities would be what really exists. On the other hand, these entities have no longer even the remotest similarity with physical objects. That was and still is the source of much intellectual d i ~ c o m f o r t I. t~ almost seems that it takes a philosopher to appre~ ciate that the difference in intuitiveness, or lack of such, between these entities and the colorless macro-objects of Descartes and Newton is at most a difference in degree. I am ready to conclude. Do the probiematic entities of physics exist? Starting from this classical question, 1 refused to take sides, exhibited instead eight major patterns that control its dialectic. Two of these, independence and realism, belong to philosophy proper. P7et the latter is needed to relieve the philosophy of physics of a burden only philosophy proper can bear. So is the distinction between perceptual and physical objects, together with the related one between construction and reconstruction. That leaves six patterns: concreteness (including orbits), acquaintance, simplicity, significance, process, and model. I have tried to sketch how each of these six may be used and I believe has been used, either explicitly or implicitly, in the controversy. A sketch cannot of course carry conviction in detail. I shall be very content if I have contributed to convincing you of something else, which is not at all a matter of detail, namely, that a philosopher of physics, unless he wants to become just another Grundlagenforscher, must not cut himself off from philosophy proper. used it, it is not. The diRerence is roughly that between construction and reconstruction. l7 For ample detail, see "The Logic of Quanta," which is reprinted in the Feigl-Brodbeck anthology. Also, in The Philosophicnl Reaieu, 69, 1960, pp. 267-270, the review of the recent symposium volume, Observation and Interpretation.