Carnap, Kuhn, and the Philosophy ofScientific Methodology

John Earman /

1 Introduction

For the past two decades logical positivism has served as a whippingboy. By emphasizing the shortcomings of this failed philosophical,program, the virtues of the new postpositiyist pTi|osop_hy__of_scienccarc made to seem more lustrous. It is, of course, not surprising tofind such polemical devices employed, since they are common to therhetoric of revolutions, whether political, scientific, or philosophical.Or so the standard assessment would go. What I find askew in thisassessment is the notion that a philosophical revolution as opposedto an evolution has taken place. For although I am no apologist forlogical positivism, it does sccoiJo jme that many of the themes£fjJT£so-called postpositivist philosophy of jscicncc arc extensions of ideasfound in the writings oLCarnap and other leading logical positivistsand logical emplficlstC^But my purpose here is not to contribute toa revisionist history of philosophy. Rather, I aim to pay homage toboth Carnap and Kuhn by noting some striking similarities and alsosome striking differences. These similarities and differences are use-ful in helping to focus some of the still unresolved issues about thenature of scientific methodology.

2 Logical Positivism, Logical Empiricism,, and Kuhn'sStructure of Scientific Revolutions

The members of the Vienna Circle often took votes on the issuesthey debated. While I have no documentary evidence to offer of an

John Earman

aclual vole, I am morally certain of what the rcsull would have beenfor ihc question, Verification is a relation between what and what?In "x is verified by y,"j&fs presumably a sentence. And it is temptingto lake^jHo be a fact, stale of affairs, or something in ihe world lhalmakes AC iruc and can be directly ascertained. But an attempt tocompare language and ihe world would have slruck ihe Circle mem-bers as of a piece with the metaphysics thai ihe verifiabilily principleof meaning was supposed lo banish. Their alternative was lo lake ylo be another sentence, for then the relationjjctwecn x and y is an .unproblcmalic logical _ rcjation._Th.Í5 move, however, seems lo leave jus in ihc same metaphysical thickel since verificalion would seem to /require thai y is a true sentence, and is not a true sentence one that /corresponds to the facls?

The escape lhat some of ihe circle members soughl was a resort toa coherence theory of truth. Eventually, however, Carnap abandoned

resort, presumably because of a combinalion of the drawbacksof the coherence account of truth and the allracliveness of 'theory of truth. Bui whal I wish to emphasize here are ihe qualifi-calions that Carnap put on any talk about comparing stalemenls wilhfacls. In "Truth and Confirmation" (1949) he emphasized lhat hepreferred lo speak of confronling slatements wilh facts:

There has been a good deal of dispute as to whether in ihc procedurescientific testing slatements must be compared with facts or as lo whether suchcomparisons be unnecessary, if nol impossible. If "comparison of slalerncnlwilh fact" means ihc procedure which we called ihc firsl opcralio^rylhcn itmusí be adinillcd lhal ihis procedure is nol only possible, bul even indis-pensable for scientific testing. Yel il musí be remarked lhal ihc formulation"comparison of statement and fact" is nol unobjeclionable. First, ihe conccpl"comparison" is not quilc appropriate here. Two objecls can be comparedin regard lo a properly which m i r r j j a rn r lnrj ~ r them in variaWe ihcrefore prefer lo speak of "cwnfronlalihH" ralhcr ihan^compansolConfrontation is understood to consX^jrjJiMnng out as tofact is such as is described in the statement, or, lo express it differently, aslo whether the statement is true to fact. (1949, 125)

Carnap then continued with a passage that might have served as anadvertisement for Kuhn's Structure of Scientific Revolutions.

Furthermore, ihc formulalion in icrms of "comparison," in speaking of"facls" or "realities" easily Icmpts one inlo the absolutislic view according lo

JJCarnap, Kulin, and the Philosophy of Scientific Methodology

which we arc said to search for an absolulc reality whose nature is assumedas fixed independently of the language chosen for its description. The answerto a question concerning reality however depends not only upon that "reality"or upon the facts, but also upon the structure (and the set concepts) of thelanguage used for the description. In translating one language into anotherthe factual content of an empirical statement cannot always be preservedunchanged. Such changes arc inevitable if the structures of the two languagesdiffer .inessential points. (1949, 125-126)

Here we have two of the key theses oTthe^gostpositivisl" philosophy iof science:, the noncxistcnce of neutral facts and incommensurabillyin the foriTiof''ftiftn^Trof™iriKrrtTanshrtabHfly. NotcTttMrt-tucsc theseswere propounded in the mid 1930s/for although I have, for the sakeof convenience, quoted from the 1949 version of Carnap's paper, therelevant passage is also in "Wahrhcil und Bewahrung" (1936)./* |

Given these Kuhnian themes—or should we rather say Carnapianthemes?—one might predict that Carnap would have found Structurephilosophically congenial. That this was indeed the case has beendocumented by Rcisch (1991). Structure was published as part of theInternational Encyclopedia of Unified Science, of which Carnap wasan associate editor. After reading the completed manuscript for Struc-ture, Carnap wrote to Kuhn in April of 1962. The text of the letteris reproduced in Reisch 1991. I will quote from notes written inCarnap's archaic shorthand. Carnap begins with a piece of Darwinianevolution and then adds, concerning Kuhn's thesis,

In analogy to this one has to understand the development of scientific the-ories: not directed to an ideal [true] theory, the one true theory of the world,but evolution as a step to a belter form, by selection of one oul of severalcompeting forms. The selection is made on ihc basis of preference in ihccommunity of scientists. Many factors, sociological, cu l tura l , . . . , are involved.Nol:vwe are approaching irulh, but: we arc improving an instrument

Another important though largely tacit theme of Structure, a holisticview of meaning, can also be seen as emerging from the writings ofthe logical empiricists in the 1950s. Hcmpel, for example, took toheart Quine's attack on the analytic/synthetic distinction, which maybe taken to embody the thesis that there is a sharp distinction to bedrawn between two functions of language: one to specify meaning,the other to make empirical assertions. Applying the moral to sci-entific theories, one arrives at the conclusion that there is no princi-

,„*>

12John Earmaii

pled way to distinguish those postulates of the theory that mayproperly be dubbed meaning postulates. It is then but a seeminglyshort and tempting step to the further conclusion that all the pos-tulates of the theory function to specify the meaning of the constit-uent terms and thus that any significant change in the theory impliesa change in meaning.

This route to semantic holism cannot be traced to any of Carnap'swritings. Indeed, in his response to HempePs contribution to theSchilpp volume (1963), Carnap attempted to use the notion of theRamsey sentence of the theory to identify the postulates of the theorythat "merely represent meaning relations" (1963a, 965). And in hislast book, Philosophical Foundations of Physics (1966), Carnap maiivtained that "a sharp analytic-synthetic distinction is of supreme im- 'portance for the philosophy of science" (1966, 257).§ There is,however, another Carnapian route to semantic holism, but that routemust be traced all the way back to Carnap's attempt in the Aufbau(1928) to explain how scientific objectivity can emerge from a recon-struction that starts from a phcnomcnalistic basis. An exploration ofthis matter would take me too far afield; I will simply refer the readerto Michael Friedman's (1987) illuminating discussion. 7 Q

^'JV /*•3 Carnap's Relativism

losophy and Logical Syntax" (1935) proclainicd the relativity ol allphilosophical theses to language. This relativity was supposed to holdthe key to solving, or rather dissolving, traditional philosophical dis-putes. Suppose, for example, one philosopher asserts, "Numbers are -primitive entities," while another proclaims, "Numbers are classes ofclasses." "They may," Carnap writes, "philosophize without end aboutthe question of what numbers really are, but in this way they willnever come to an agreement" (1935, 450). If, however, they are acuteenough to recognize Carnap's relativity principle, they will quicklyrealize that one is asserting, "In Language LI (Peano), numericalexpressions are elementary expressions," while the other is maintain-ing, "In Language L? (Russell) numerical expressions are class ex-pressions of the second order." "Now these assertions are compatible j

c

Carnap, Kulin, and the Philosophy of Scientific Methodology

with each other and both arc true; the controversy has ceased toexist" (1935, 451). This model for resolving philosophical disputes in •the philosophy of mathematics was supposed by Carnap to be cxtend-iblc quite broadly to philosophical disputes, such as phenomenalismversus materialism and the question of whether space-time pointshave an existence independent of physical events.

Some, like Donald Davidson (1973), have found an air of paradoxin the fact that saying in one breath (as Carnap thought he could)that 5 is true in L\, LS, Las, • • . but false in L?, ¿4, ... seems topresuppose a neutral metaframe within which all the language framescan be treated.6 Others, like Michael Friedman (1992), have arguedthat Carnap's relativism is undercut by Godel's incompleteness theo-rems, which show that no such neutral metaframe is available. Myobjections are more local and tactical.

My first complaint is that Carnap assumes what needs to be proved.According to Carnap's "principle of tolerance," we are free to choosewhatever language system we like. The decision is largely a pragmaticaffair, turning on such matters as efficiency and fruitfulness for the

-purposes at hand. But to apply the slogan of "free to choose" todissolve, say, the phenomenalism versus materialism debate assumesthat a phenomenalistic language has been produced that shows howphysical object talk can be reduced to talk about sensa data or, asCarnap preferred, momentary total experiences ("Elementarerlcb-nissc"). This, of course, is exactly what Carnap tried to do in theAv/lau. But by his own admission, the attempt has to counted as afailure if, as he originally assumed, the reduction has to proceed viaexplicit definitions and explicit Iranslalions. Similarly, to apply the"free to choose" slogan to dissolve disputes about the ontplogicalstatus of space-time points assumes that it can be shown how space-time points can be constructed out of events, such as coincidences ofparticles. Advocates of relational theories of space and time repeat-edly claim that this can be done and even that it has been done. Butnone of the claims stands up to scrutiny.7 I am emphatically notclaiming that materialism is correct or that space-time points con-strued as irreducible entities are essential to physics. Rather, I amclaiming that the dissolution of the traditional disputes on thesematters is not as easy as Carnap made it seem.

MJohn Earman

Another complaint arises from the breathtaking scope of the in-tended application of Carnap's dissolving strategy. Among the "philo-sophical" disputes that Carnap proposed to treat in this way weresuch matters as whether time is finite or infinite and whether theworld is deterministic. There is obviously a very slippery slope here.If the question about the finilude of time is a philosophical questionin the relevant sense, then why not the question of whether the worldbegan from a big-bang singularity? And if this latter question is aphilosophical question in the relevant sense, then why not other deepquestions in cosmology? But more important, one does not have togo down the slope to recognize the implausibihty of Carnap's pro-cedure. Even if one agrees to talk about truth in L rather than truthperiod, there is no plausibility to the idea that whether time is finiteand whether determinism holds are matters to be settled in L byadopting linguistic rules for L rather than by consulting the facts.Carnap, not surprisingly, acknowledged the point. Speaking of thedeterminism issue, he said,

The objection may pcriiaps be raised at this point that the form of physicallaws depends upon experimental results of physical investigation, and thatit is not determined by a merely theoretical syntactical consideration.' Thisassertion is quite right, but we must bear in mind the fact that the empiricalresults at which physicists arrive by way of their laboratory experiments byno means dictate their choice between the deterministic and the statistical' formof laws. The form in which a law is to be slated has to be decided by an actof volition. This decision, it is true, depends upon the empirical results, butnot logically, only practically. The results of the experiments show merelyill.il one mode of formulation would be more suitable than another. (1935,455)

These sentiments resonate with those Carnap expressed three de-cades later in commenting on Kuhn's Structure. But here the senti-ments arc not to the point. The issue is not whether, for Duhemianor other reasons, the results of experiments, say the recent Einstein,Rosen, Podolsky, and Bell type of experiments, fail to dictate theacceptance of indeterministic laws. Rather the issue is whether deter-minism is a scientific claim to be argued over the way one arguesover other deep scientific claims, none of which ever gets definitivelysettled by the dictates of experimental evidence; or whether deter-minism is a claim that can be made true by linguistic fiat in L\, Lr,,

Carnap, Kuhn, and the Philosophy of Scientific Methodology

¿35, . . . and false by linguistic fiat in L2, LT, ¿37 ..... and then wejust pays our money and takes our choice of language. Again I refuseto give a global answer to this query and favor instead a tacticalresponse. All indications are that the debate over the implications fordeterijiinism of the Bell inequalities and the Aspect experimentsbelongs to the former rather than to the latter. Indeed, indicationsare that in any language system adequate for the formulation oftheories that save the experimentally verifiable quantum statistics, thelaws must be indeterministic.9

I suspect that Carnap's relativism began by his being impressed bythe achievements of Frege, Russell, and others in the philosophy ofmathematics and was furthered by a misplaced zeal for extending hismodel for resolving philosophical disputes in this area to a broadarea of philosophical and scientific questions. Of course, whateverthe origins of Carnap's relativism, it or something like it could per-haps be promoted on the basis of his doctrine that language-neutralfacts do not exist. I find it difficult to assess this matter, since I donot find in Carnap's writing a helpful explanation of thisIn the following section I will comment on the related doctrine ofFeycrabcnd, Hanson, and Kuhn that observation is theory laden.

In closing this section, I note that Carnap displayed a consistencyon the matter at hand — not the consistency that is the hobgoblin oflittle minds but the magnificent consistency of a grand visionary. Inhis contribution to the Schilpp volume for Carnap, Herbert Fcigl(1963) sketched a mind-body identity theory that he was later toelaborate in his famous essay "The 'Mental' and the Thysi-caF"(1958).'° Clearly, the politically correct thing for Carnap was toendorse Fcigl's approach. Instead, he wrote, "it seems preferable tome to formulate the question [of mind-body identity] in the meta-language, not as a factual question about the world, but as a questionconcerning the choice of language. Although we prefer a differentlanguage, we must admit that a dualistic language can be constructedand used without coming into conflict with cither the laws of logic orwith empirically known facts" (1963b, 885-886).

4 Kuhn's Relativism

Kuhn resists being labeled a relativist. I use the label here to refer tothree doctrines of Structure: the theory ladenncss of observation, the

]GJohn Earnian

¡ncomnicnsurability of theories, and (lie denial that there is a llicory-indcpcndcnl notion of truth.

Part of what was meant by the theory ladcnncss of observation isembodied in the thesis that what we see depends upon what webelieve, a thesis open to challenge (see Fodor 1984). I am concernedrather with the related thesis of the nonexistence of a neutral obser-vation language in which different theories can be compared. Myresponse is once again tactical. That is, without trying to adjudicatethe general merits of the thesis, I claim that things aren't so bad foractual historical examples. Even for cases of major scientific revolu-tions, we cari find, without having to go too far downward towardsomething like foundations for knowledge, an observation base thatis neutral enough for purposes at hand. A nice example is provided byAllan Franklin (1986, 110-113), who shows how to construct anexperiment that is theory-neutral enough between Newtonian andspecial-relativistic mechanics to unambiguously decide between thepredictions of these theories for elastic collisions. The two theoriesagree on the procedure for measuring the angle between the velocityvectors of the scattered particles, and the two theories predict differ- ~ent angles. A ̂ b

More generally, I claim that in the physical sciences there is inprinciple always available a neutral observation base in spatial coin-cidences, such as dots on photographic plates, pointer positions ondials, and the like. If intcrsubjective agreement on such matters werenot routine, then physical science as we know it would not be possible.1 reject, of course, the posilivistic attempt to reduce p'hysics to suchcoincidences. And I readily acknowledge that such coincidences bythemselves are mute witnesses in the tribunal for judging theories.But what is required to make these mute witnesses articulate is not aGcstalt experience but a constellation of techniques, hypotheses, andtheories: techniques of data analysis, hypotheses about the operationof measuring instruments, and auxiliary theories that support boot-strap calculations of values for the relevant theoretical parametersthat test the competing theories. But I again assert that to the extentthat this process cannot be explicitly articulated but relies on somesui generis form of perception, the practice is not science. This is notto say, however, that the vulgar image of science as a blindly impartialenterprise is correct, for the articulation uncovers assumptions to

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17Carnap, Kulin, and the Philosophy of Scientific Methodology

which different scientists may assign vcfy different, degrees of con-fidence. But this sense in which different scientists can (mislcadingly)be said to "see" different things when looking at the same phenom-enon is one with which a probabilistic or Bayesian epistemology—thekind of epistemology which the later Carnap came to advocate—mustcope on a routine basis, even in cases far away from the boundariesof scientific revolutions. How these differences are resolved is partof the Bayesian analogue of Kuhn's problem of community decisionon theory choice. Kuhn's problem will be encountered in the follow-ing section, and the Bayesian analogue will be discussed in sections8 and 9.

The matter of incommensurability is much more difficult to discussfor two reasons. First, it is tied to difficult issues about meaning andreference that I cannot broach here. Second, issues about incom-mensurability present amorphous and shifting targets. In Structure,for example, incommensurability was a label for the entire constel-lation of factors that lead proponents of different paradigms to talkpast one another. In recent years Kuhn has come around to a moreCarnapian or linguistic formulation in which incommensurability isequated with untranslatability. More specifically, the focus has shiftedfrom paradigms to theories, and two theories are said to be incom-mensurable just in case "there is no common language into whichboth can be fully translated" (Kuhn 1989, 10). I have no doubts aboutKuhn's claims that theories on different sides of a scientific revolutionoften use different "lexicons," that differences in lexicons can makefor a kind of untranslatability, and that in turn this explains whyscientists reading out-of-date texts often encounter passages that"make no sense" (1989, 9). But I deny that there is incommensura-bility/untranslatability that makes for insuperable difficulties for con-firmation or theory choice (a phrase I don't like for reasons to begiven below) in the standardly cited cases of scientific revolutionssuch as the transition from Newtonian to special-relativistic mechanicsand the subsequent transition to general relativity. Newtonian, spe-cial-relativistic, gcncral-relativistic, and many other theories can allbe formulated in a common language, the language of differentialgeometry on a four-dimensional manifold, and the crucial differencesin the theories lie in the differences in the geometric object fields

J8John Earman

postulated and the manner in which these fields relate to such thingsas particle orbits. This language is anachronistic and so may not bethe best device to use when trying to decide various historical dis-putes." But it does seem to me to be an appropriate vehicle forframing and answering the sorts of questions of most concern toworking physicists and philosophers of science. For example, on thebasis of the available evidence, what is it reasonable to believe aboutthe structure of space and time and the nature of gravitation? Thisis not to say that the common language makes for an easy answer. Itis indeed a difficult business, but it is a business that involves thesame sorts of difficulties already present when testing theories thatlie on the same side of a scientific revolution. Finally, so that therecan be no misunderstanding, let me repeat: I am not claiming (hatwhat I call a common language provides what Kuhn wants. It docsnot show, for example, that the Newtonian and the Einstcinian canbe brought into agreement about what is and is not a "meaningful"question about simultaneity. But what I do claim is that these residualelements of incommensurability do not undermine standard accountsof theory testing and confirmation.12

My response to worries about the applicability of the notion oftruth to whole theories is similarly local and tactical. In the Postscriptto the second edition of Structure, Kuhn writes, "There is, I think, notheory-independent way to reconstruct phrases like 'really there'; thenotion of a match between the ontology of a theory and its 'real'counterpart in nature now seems to me illusive in principle" (1970,206). I need not demur if "theory" is understood in 'a very broadsense to mean something like a conceptual framework so minimalthat without it "the world" would be undifferenliated Kantian ooze.But I do demur if "theory" is taken in the ordinary sense, i.e., asNewton's theory or special-relativity theory or general-relativity the-ory.13 For scientists are currently working in a frame in which theycan say, correctly I think, that the match between the ontology of thetheory and its real counterpart in nature is better for the specialtheory of relativity and even better for the general theory. Of course,to get to this position required two major coneptual revolutions. Howsuch revolutions affect theory choice, or as I would prefer to say,theory testing and confirmation, remains to be discussed.

]9Carnap, Kuhn, and the Philosophy of Scientific Methodology

5 Kuhn's Account of Scientific Revolutions

Carnap, as we have seen, found Kuhn's Structure congenial. But many •philosophers of the younger generation, including those who pridedthemselves on having gone beyond the crudities of logical positivism,professed shock and dismay at Kuhn's account of the displacementof an old paradigm by a new one. For those readers who do not havea copy of Structure to hand, here are some of the purple passages:

Like the choice between competing political institutions, that between com-peting paradigms proves to be a choice between incompatible modes ofcommunity life. . .. When paradigms enter, as they must, into a debate aboutparadigm choice, their role is necessarily circular. Each group uses' its ownparadigm to argue in that paradigm's defense. (P. 94)

As in political revolutions, so in paradigm choice—there is no standardhigher than the assent of the relevant community. To discover how scientificrevolutions arc effected, we shall therefore have to examine not only theimpact of nature and logic, but also the techniques of persuasive argumen-tation within the cjuilc special groups that constitute the community of sci-entists. (P. 94)

The proponents of competing paradigms practice their trades in differentworlds. . . . Practicing in different worlds, the two groups of scientists secdifferent things when they look from the same point in the same direction.(P. 150)

In these matters neither proof nor error is at issue. The transfer of allegiancefrom paradigm to paradigm is a conversion experience that cannot be forced.(P. 151)

Before they can hope to communicate fully, one group or the other mustexperience the conversion that we have been calling a paradigm shift. Justbecause it is a shift between incommensurables, the transition between com-peting paradigms cannot be made a step at a time, forced by logic andneutral experience. Like a gcslalt switch, it must occur all at once (thoughnot necessarily at an instant) or not at all. (P. 150)

Many readers saw in these passages an open invitation to aralio-nality if not outright irrationality. Thus Imre Lakatos took Kuhn tobe saying that theory choice is a matter of "mob psychology" (1970,178), while Dudley Shapcre read Kuhn as saying that the decision toadopt a new paradigm "cannot be based on good reasons" (1966, 67).

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John Earman

Kulin in turn was equally shocked by such criticisms. In the Postscriptto the second edition of Structure (1970), he professed surprise thatreaders could have imposed such unintended interpretations on theabove quoted passages. I will leave aside the unfruitful question ofwhether or not Kuhn ought to have anticipated such interpretationsand will concentrate instead on what, upon reflection, he intendedto say.

Kuhn's own explanation in the Postscript begins with the common-place that "debate over theory-choice cannot be cast in a form thatresembles logical or mathematical choice" (1970, 195). But he hastensto add that this commonplace does not imply that "there are no goodreasons for being persuaded or that these reasons are not ultimatelydecisive for the group" (1970, 195). The reasons listed in the Post-script are accuracy, simplicity, and fruitfulness. The later paper "Ob-jectivity, Value Judgments, and Theory Choice" (1977) added twofurther reasons: consistency and scope. And as Kuhn himself notes,the final list does not differ (with one notable exception to be dis-cussed later) from similar lists drawn from standard philosophy-of-scicnce texts (see also Kuhn 1983).

These soothing sentiments serve to deflate charges of arationalityand irrationality, but at the same time they also serve to raise thequestion of how Kuhn's views are to be distinguished from the or-thodoxy that Structure was supposed to upset. The answer given inthe Postscript contains two themes, which are elaborated in "Objec-tivity." First, the items on the above list are said to "function as values"that can "be differently applied, individually and collectively by menwho concur in honoring them" (1970, 199). Thus, "there is no neutralalgorithm for theory choice, no systematic decision procedure which,properly applied, must lead each individual in the group to the samedecision." Second, it (supposedly) follows that "it is the communityof specialists rather than the individual members that makes theeffective decision" (1970, 200).

I think that Kuhn is correct in locating objectivity in the communityof specialists, at least in the uncontroversial sense that intersubjectiveagreement among the relevant experts is a necessary condition forobjectivity. But how the community of experts reaches a decisionwhen the individual members differ on the application of sharedvalues is a mystery that to my mind is not adequately resolved by

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Carnap, Kuhn, and ihc Philosophy of Scicnlific Mclhodology

Structure or by subsequent writings. My strategy will be to explorethese and related issues from the perspective of Carnap'scpistcmology.

6 Carnap and Kuhn: Incommensurability?

The passage Reisch (1991) quotes from Carnap's letter to Kuhn andthe passage from Carnap's shorthand notes I quoted in section 2would seem to indicate that Carnap and Kuhn were in substantialagreement as regards paradigm choice. This is surely the case when"paradigm" is interpreted to mean something like a linguistic frame-work. At this level Carnap would agree, indeed, would insist, on theneed to choose, and he would hold that the choice is'a pragmatic onewhose dynamics may well involve the sorts of factors emphasized inKuhn's account. But when the focus shifts to theories, as it does in •Kuhn's later writings, the disagreement begins. In the first place,Kuhn's list of criteria for theory choice is conspicuous for its omissionof any reference to the degrees of confirmation or probabilities ofthe theories. This is not an oversight, of course, but derives bothfrom explicit doctrines, such as the nonexistence of a theory-neutralobservation language, and the largely tacit but pervasive anti-induc-tivism of Structure. Needless to say, this shunning of confirmationtheory is most un-Carnapian. But even more anomalous from Car-nap's perspective is Kuhn's emphasis on theory choice or acceptance,for in Carnap's version of epistemology, theories arc not chosen oraccepted but only probabiIified.M

Carnap's writings in the 1940s and 1950s portray him as espousinga "logical" conception of probability. But by the late 1950s and early1960s, he clearly favored a view that can be termed tempered per-sonalism: probability is rational degree of belief.15 I will have moreto say on this matter in section 8, but in the meantime I will presentCarnap as a tempered Bayesian personalist.

A shotgun marriage of Kuhn and Carnap could be arranged bytaking Carnap to supply the probabilities, Kuhn to supply the valuesor utilities, and then applying the rule of maximizing the expectedutility to render a decision on theory choice.16 But like most shotgunmarriages, this one would be a mistake. For Carnap it would be amistake because it would involve the pretense that the accepted the-

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John Carman

ory is certain even though one's degree of belief in the theory maybe less than one, perhaps substantially so. For Kuhn it would also bea mistake, since the efficacy of his values does not depend on thetruth of the theories, so estimates of the probable truth of the theoriesis irrelevant to Kuhnian theory choice.

Part of the wrangle here derives from the unfortunate phrase"theory choice." Scientists do choose theories, but on behalf of Car-nap, I would claim that they choose them only in the innocuous sensethat they choose to devote their time and energy to them: to articu-lating them, to improving them, to drawing out their consequences,to confronting them with the results of observation and experiment.Choice in this sense allows for a reconciliation of Bayes and Kuhn,since this choice is informed by both Baycsian and Kuhnian factors:probability and the values of accuracy, consistency, scope, simplicity,and fruitfulncss.

Alas, this reconciliation is rather shallow. Once we are clear thatthe sort of choice involved in "theory choice" is a practical one, thereis nothing sacred about the list of items on Kuhn's list of values.Other values, such as getting an NSF grant or winning the NobelPrize, can and do enter. Further, the kind of choice in question allowsa scientist to be bigamous, since he can choose to work on two ormore theories at once, and it allows him to be fickle, since he canoscillate back and forth. The kind of choice Structure envisioned wasmuch more permanent; indeed, the impression given there is thatnormal science is not possible without tying Catholic bonds to atheory, bonds that can only be broken by leaving the Church, i.e., bycreating a revolution.

Is there no way to bridge the gap between Carnap and Kuhn onthis issue? To see how baffling the Bayesian finds the notion of theoryacceptance, consider the case of Einstein's general theory of relativity(GTR), arguably the leading theory of gravitation and thus the topcandidate for acceptance. Marie, a research worker in the field fa-miliar with all of the relevant experimental findings, does some in-trospection and finds that her degree of belief in GTR is p.

Case 1: p is 1, or so near 1 as makes no odds. Here there is a naturalsense in which the Bayesian can say that Marie accepts GTR. Suchcases, however, arc so rare as to constitute anomalies. Of course, one

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Carnap, Kuhn, and llic Philosophy of Scientific Mclhodology

can cite any number of cases from the history of science wherescientists seem to be saying for their pet theories that they set p = 1.Here I would urge the need to distinguish carefully between scientistsas advocates of theories versus scientists as judges of theories. Thelatter role concerns us here, and in that role scientists know, or shouldknow, that only in very exceptional cases does the evidence rationallysupport a full belief in a theory. Let us move on to case 2.

Case 2: p is, say, .75. Subsequently Marie decides to "accept" GTR onthe basis of her probability assignments and the values she attachesto GTR and its competitors. What could this mean?

Subcase 2a. When she accepts GTR, Marie changes her degree ofbelief from .75 to 1. This is nothing short of folly, since she hasalready made a considered judgment about evidential support andno new relevant evidence occasioning a rejudgment has come in.

Suitcase 2b. When she accepts GTR, Marie docs not change her de-gree of belief from .75 to 1, but she acts as z/all doubt were sweptaway in that she devotes every waking hour to showing that variouspuzzling astronomical observations can be explained by the theory,she assigns her graduate students research projects that presupposethe correctness of the theory, she writes a textbook on gravitationalresearch that is devoted almost exclusively to GTR, etc. But at thispoint we have come full circle back to a sense of theory acceptancethat is really a misnomer, for what is involved is a practical decisionabout the allocation of personal and institutional resources and nota decision about the cpistcmic status of the theory.

This rather pedantic diatribe on theory acceptance would be bestforgotten were it not for its implications for our picture of normalscience. As we have seen, theory "choice" or "acceptance" can refercither to adopting an epislemic attitude or to making a practicalchoice. In the former case there is no natural Bayesian explicationof theory acceptance save in the case where the probability of thetheory is one. Since scientists as judges of theories are almost neverin a position to justify such an acceptance, the Bayesian prediction isthat rarely is a theory accepted in the epistemic sense. Similarly, whentheory choice is a matter of deciding what theory to devote one's limeand energy to, the Bayesian prediction is that in typical situations

John l'.arnian

where members of the community assign different utilities to suchdevotions, they will make different choices. Thus from either thecpistcmic or practical-decision perspective, the Bayesian prediction isdiversity. This prediction is, I think, borne out by actual scientificpractice. In section 9 below I will argue that insofar as normal scienceimplies a shared paradigm, the paradigm need not and in fact oftenis not so specific as to include a particular ("accepted") theory. I willalso hazard a proposal for a minimal sense of "shared paradigm" thatyields a less strait-jacketed image of normal science and that alsodiminishes without obliterating the difference between normal andrevolutionary science.

By way of closing this section and introducing the next, I willconsider a final way of reconciling Kuhn and Carnap on theorychoice. Radically new theories, so the story goes, carry with themdifferent linguistic/conceptual frameworks. Thus, even seriously loentertain the new theory involves the decision to adopt, if only ten-tatively, the new framework, and this decision is for Carnap a prag-matic one that involves the sorts of factors emphasized in Kuhn'saccount of paradigm replacement. In response I would repeat whatI have already said in section 4: major scientific revolutions such asthe transition from Newtonian to special-relativistic physics- andthence lo general relativity needn't be seen as forcing a choice be-tween incommensurable linguistic/conceptual systems, since it is oftenpossible lo fit ihc possibilities into a larger scheme thai makes llictheories commensurable lo the extenl lhal confirmalion questionscan be posed in terms of an observation base lhal is ncuiral enoughfor assessing ihe relalive confirmation of the theories. However, iherccognilion of ihe larger possibility set can produce a drastic changein probability values, a change best described in Kuhnian terms.

7 Revolutions and Belief Shifts

A mild form of scientific revolution occurs with ihe inlroduclion ofa new llieory lhal articulates possibilities thai lie wilhin ihe bound-aries of ihe space of iheories to be taken seriously but that, becauseof the failure of actual scientists to be logically omniscienl, had pre-viously been unrecognized as explicil possibilities. The more radicalform of revolulion occurs when ihe space of possibilities itself needs

25Carnap, Kuhn, and ihc Philosophy of Scicnlific Methodology

to be significantly altered to encompass the new theory. In practicethe distinction between the two forms of revolution may be blurred,perhaps even hopelessly so, but I will begin discussion by pretendingthat we can perform a separation of cases.

Even the mild form of revolution may induce a non-Bayesian shiftin belief functions. By non-Bayesian I mean that no form of condi-tionalizalion, whether strict or Jeffrey or some natural extension ofthese, will suffice to explain the change. For conditionalizing (in anyrecognizable sense of the term) on the information that just now aheretofore unarliculated theory T has been introduced is literallynonsensical, because such a conditionalization presupposes that priorto this time there was a well-defined probability for this informationand thus for T, which is exactly what the failure of logical omnisciencerules out.

We can try to acknowledge the failure of logical omniscience bymeans of Abner Shimony's (1970) device of a catch-all hypothesis Hf,which asserts in effect that something, we know not what, beyondthe previously formulated theories T\, Tz, . . . , TT is true. Nowsuppose that a new theory T is introduced and that as a result theold degrce-of-bclief function Pr is changed to Pr'. The most conser-vative way the shift from Pr to Pr' could take place is by the processI will call shaving off, namely, Pr(T,) =.Pr'(Ti) for i = 1, 2, . . . , q andPr'(T) = r > 0 and Pr'(//e) = Pr(//c) - r. That is, under shaving off,Hf serves as a well for initial probabilities for as yet unborn theories,and the actual introduction of new theories results only in drawingupon this well without disturbing the probabilities of previously for-mulated theories. Unfortunately, such conservatism eventually leadsto the assignment of ever smaller initial probabilities to successivewaves of new theories until a point is reached where the new theoryhas such a low initial probability as to stand not much of a fightingchance.

Certainly shaving off is a factually inadequate description of whathappens in many scientific revolutions, especially of the more radicaltype. Think of what happened following the introduction of Ein-stein's special theory of relativity (STR) in 1905. Between 1905 and1915 little new empirical evidence in favor of STR was recorded, andyet the probability of competing theories, such as those of Lorentzand Abraham, set in classical space and time, fell in the estimates of

26John Earman

most of the members of the European physics community, and theprobability subtracted from these electron theories was transferredto Einstein's STR. The probabilities of auxiliary hypotheses may alsobe affected, as illustrated by the introduction of the general theoryof relativity (GTR). When Einstein showed that GTR accounted forthe exact amount of the anomalous advance of Mercury's perihelion,the hypothesis of an amount of zodiacal matter sufficient to affectMercury's perihelion dropped dramatically in the estimates of mostof the physics community (see Earman and Glymour 1991).

In using the term "non-Bayesian" to describe such noncondition-alization belief changes, whether of the conservative shaving-off typeor some more radical form, I do not mean to imply that the changesare not informed by Bayesian considerations. Indeed, the problemof the transition from Pr to Pr' can be thought of as no more andno less than the familiar Bayesian problem of assigning initial prob-abilities, only now with a new initial situation involving a new set ofpossibilities and a new information basis. But the problem we arcnow facing is quite unlike those allegedly solved by classical principlesof indifference or modern variants thereof, such as E. T. Jayncs'smaximum-entropy principle, where it is assumed we know nothingor very little about the possibilities in question. In typical cases thescientific community will possess a vast store of relevant experimentaland theoretical information. Using that information to inform theredistribution of probabilities over the competing theories on theoccasion of the introduction of the new theory or theories is a processthat, in the strict sense of the term, is\o?Slipnal: it cannot'be accom-plished by some neat formal rules or, To use Kuhn's term,_bvanalgorithm. On the otherjjand, the process is far from beirígjrrationaí>>since it is informecf by reasons. But the reasons, as Kuhn Tias~crrf-phasized, come in the form ofpersuasions rather than proof. InBayesian terms, the reasons are marshaled in the guise of ptausiblTilyarguments. The deployment of plausibility arguments is an art formfor which there currently exists no taxonomy. And considering thelimitless variety of such arguments, it is unlikely that anything morethan a superficial taxonomy can be developed. Einstein, the consum-mate master of this art form, appealed to analogies), symmetry con-siderations, thought experiments, heuristic principles such as theprinciple of equivalence, etc. All of these considerations, I am sug-

27 t " •Carnap, Kuhn, and the Philosophy of Scientific Methodology

gcsting on behalf of the Baycsians, were deployed to nudge assign-ments of initial probabilities in favor of the theories Einstein wasintroducing in the early decades of this century. Einstein's success inthis regard is no less important than experimental evidence in ex-plaining the reception of his theories.

To summarize, Kuhn's purple passages do not seem overblownwhen applied to revolutions in the strong sense distinguished above.The persuasions that lead to the adoption of the new shape for thepossibility space cannot amount to proofs. Certainly for the Bayesianthey cannot consist of inductive proofs, since the very assignment ofdegrees of belief presupposes the adoption of such a space. After arevolution has taken place, the new and old theories can often befitted into a common frame that belies any vicious form of incom-mensurability (as I tried to illustrate in section 4 for Newtonian andrelativistic theories). But this retrospective view tends to disguise theshake-up in our system of beliefs occasioned by the adoption of thenew shape for the possibility space. Baycsianism brings the shake-upto light, albeit in a way that undercuts the standard form of thedoctrine.

I have no way of knowing whether Carnap would have approvedof my Bayesian reading of Kuhn. But I do claim that it is a readingthat fits naturally with Carnap's mature views on probability andinduction.

8 Objectivity and the Problem of Consensus

I have endorsed a Bayesianized version of Kuhn's claim that in sci-entific revolutions persuasion rather than proof is the order of theday: revolutions involve the introduction of new possibilities; thisintroduction causes the redistribution of probabilities; the redistri-bution is guided by plausibility arguments; and such arguments be-long to the art of persuasion.

This endorsement is confined to the first stage of the revolution,when the initial probabilities are established for the expanded pos-sibility set. The Bayesian folklore would have it that after this firststage, something more akin to proof than persuasion operates. Theidea is that an evidence-driven consensus emerges as a result of theBayesian learning model: degrees of belief change by conditional!-

28John Earman

/.¡ilion on ilic accumulating evidence of observation and experiment,and the long-run result is to force a merger of posterior opinion forthose Baycsian agents who initially assign zeros to the same hy-potheses. This folklore can draw on some mathematically impressivemerger-of-opinion theorems. But these theorems are of dubious ap-plicability not only to the sorts of cases discussed in Structure but alsoto examples from normal, as opposed to revolutionary, science. Forone thing, the mathematical results are in the form of long-run orlimit results that give no information about how long the long runis."

If honest theorem proving won't suffice to explain the merger ofopinion that, for the Bayesian epistemologist, constitutes the heart ofscientific objectivity, then perhaps we can define our way to a solution.That is, why not define "scientific community" in terms of de factoconvergence of opinion over a relevant range of hypotheses? Theanswer is the same as that given by Kuhn in the Postscript to thethreatened circularity of taking a paradigm to be what members ofthe community share while also taking a scientific community toconsist of those scientists who share the paradigm. Just as scientificcommunities "can and should be isolated without prior recourse toparadigms" (Kuhn 1970, 176), so they can and should be isolatedwithout recourse to convergencc-of-opinion behavior. The Europeanphysics community in the opening decades of this century can beidentified by well-established historical and sociological techniques.One wants to know how and why, for example, this community soidentified reached a consensus about Einstein's STR. Nevertheless,there does seem to be at least this much truth to the definitionalmove: repeated failures to achieve merger of opinion on key hy-potheses will most likely lead.to a split in or a disintegration of thecommunity.

This is the appropriate place to ask whether Carnap's views onprobability are of any help. In a letter dated July 30, 1963, Carnapwrote to Bruno De Finctti, the arch Baycsian personalisl, that hebelieved that the constraints of rationality extend beyond the require-ment of coherence, which entails that degrees of belief must conformto the standard axioms of probability.18 According to Carnap therequirements of rationality do not suffice to single out a uniqueprobability function, but they do significantly constrain the choice of

2!)Carnap, Kuliii, and the Philosophy of Scientific Methodology

a probability funclion. If this were corrccl, ihc liaycsian version ofllie problem of scicnlific objectivity would be made correspondinglyeasier. However, I do not think that Carnap managed to stake out adefensible position, as can be brought out by the question of howone recognizes which probability functions are "rational." Carnap'sanswer was to appeal to what he variously called "inductive intuilion"and "induclivc common sense." The trouble, of course, is that oneperson's inductive common sense is another's inductive non-sense.So the appeal to intuition reveals very diffcrenl opinions as lowhelhcr it is rational to learn from experience at all and, if so, atwhat rate.

At this juncture il will be helpful to review a mechanism proposedby Lehrei and Wagner in Rational Consensus in Science and Society(1981) for achieving a group consensus. Their mechanism requiresthat the members of ihc community change ihcir degrees of beliefin accordance wilh a wcighled-aggrcgalion rule. Suppose that at theinitial moment, person i has a degree of belief /;, in the theory inquestion. Each person i is assumed to assign a weight w¡/ ̂ 0 to everyperson _;', which can be taken as an index of i's opinion as to thereliability of/s opinions. According to Lchrcr and Wagner's rule, ithen "improves" her inilial opinion />? by changing it to pi = X,w,y/>".If there arc still differences of opinion, the aggregation process isrepeated with the /;,' to obtain further "improved" probabilities /;?,etc., unti l eventually the probabilities for all members fall into line.

Lchrcr and Wagner offer a consistency argument for their aggre-gation rule: "If a person refuses to aggregate, though he does assigna positive weight to other members, he is acting as though he assigneda weight of one to himself and a weight of zero to every other memberof the group. If, in fact, he assigns positive weight to other membersof the group, ihen he should nol behave as if he assigned zero weightlo them" (1981, 22). This argument has the flavor of "When arc yougoing to slop beating your wife." I do assign a, positive weight to theopinions of others, but as a liaycsian I do this not by means ofweighted aggregation but by conditionalization: I conditionalizc oninformation about the opinions of my peers, and I notice that theresult is a shift in my degrees of belief toward the degrees of beliefof those I respect. When I was a young student, these shifts brought

. my opinions closely in line with those belonging to people I regarded

30John lüirmun

as the experts, but as a mature member of the community, I findthat such shifts, while still nonnegligiblc, do not conform my opinionslo those of others, at least not on matters where I now regard myselfas an expert. And I resist any further attempt to bend my carefullyconsidered opinions.

There are two reasons, independent of Bayesianism, to be unhappywith Lehrer and Wagner's proposal and ones like it. The first is thatit is descriptively false, as shown by the very example they use tomotivate their proposal. In the 1970s Robert Dicke claimed thatoptical measurements of the solar disk revealed an oblateness largeenough to account for 3" to 5" of arc in Mercury's centenary peri-helion advance and thus to throw into doubt Einstein's explanationof the advance. When other astrophysicists disagreed with Dicke'sconclusions the differences were not smoothed over by producing aconsensual probability by means of a weighted aggregation process.The disagreement remains unresolved to this day. The weight ofopinion docs seem lo be going against Dicke's inlcrprctation, but thispartial agreement is in fact due not to aggregation but to the acqui-sition of additional evidence.

Of course, Lchrcr and Wagner are perfectly aware of these facts,and the descriptive inadequacies of their proposal do not concernthem, since they take themselves to be offering a normative proposal.But even in ihcsc terms the proposal should be faulted. It is funda-mental lo science thai opinions be evidence-driven. Differences ofopinion need not constilutc an embarrassment that needs lo bequashed, for ihesc differences can serve as a spur lo further iheo-relical and experimental research, and the new information pro-duced may drive a genuine scientific consensus. The alternative, anatlcmpl lo manufaclure a consensus by a weighted-aggregation pro-cedure, smacks of the "mob psychology" of which Kuhn wascriticized.

This last point generalizes. Bayesianism and other approaches toscienlific inference as well suggest that unless there is some evidence-driven process that operates on the level of individual scientists toproduce a group consensus, ihe consensus will amounl lo somethingthat, if not mob psychology, is nevertheless a social artifact not de-serving either of the labels "rational" or "scienlific." Thus, conlrary

Carnap, Kulin, and the Philosophy of Scientific Methodology

to Kuhn's idea, the group cannot decide—it cannot rationally decideto agree if the individuals disagree. I do not see how this conclusioncan be escaped unless some yet to be articulated collcctivisl method-ology is shown lo be viable.

9 A Partial Resolution to the Problem of Consensus

Part of the answer to the Bayesian version of the problem of consen-sus is that quite often it does not exist and does not need to exist fornormal scientific research to take place. Structure warned of the dan-ger of taking textbook science as our image of how real scienceactually operates, and in particular, it showed how textbook sciencetends lo make scientific revolutions invisible by painting an overlyrosy picture of a smoothly accumulating stockpile of scientific knowl-edge. But I think that Structure failed to emphasize how textbookscience also disguises the diversity of opinions and approaches thatflourish in nonrcvolutionary science.

If I had the space, 1 would offer as a case study the developmentof relativistic gravitational research over the last seventy-five-years.19

Textbooks in this area have tended to be books on Einstein's GTR,thus fostering the illusion that GTR has achieved the status of para-digm hegemony. In addition, early textbooks not only downplayedthe existence of rival theories but disguised serious difficulties withtwo of the principal experimental tests of GTR, the red shift and thebending of light. Normal scientific research in this field continued inthe face of both a challenge lo the third experimental leg of GTRderiving from Dicke's solar-oblateness measurements and also an evergrowing number of rival theories of gravitation. This and similarexamples suggest that normal science is possible when the communityof experts share a paradigm in the weak sense of agreement on theexplanatory domain of the field, on the circumscription of the spaceof possible theories to be considered as serious candidates for cov-ering the explanatory domain, on exemplars of explanatory success,and on key auxiliary hypotheses. (I am tempted to say that this is theminimal sense of paradigm needed to underwrite normal science,but historians of science probably have counterexamples waiting inthe wings.)

John Kai man

One could argue that not having a paradigm in the stricter senseof a shared theory of gravitation has lowered the puzzle-solvingefficiency of normal science. One can recall Thornc and Will's (1971)lament thai, faced with a zoo of alternative theories of gravitation,astrophysicists where hamstrung in their model-building activity.While I think that this is a fair observation, I also think that there ismore to progress in normal science than puzzle solving. In particular,I would emphasize the conceptual advances derived from the explo-ration of the space of possible theories, a point that brings me to thesecond part of my partial answer to the problem of consensus.

Again, if I had the space, I would argue that insofar as a consensusis established, it is often due to a process akin to the much malignedidea of eliminativc induction. This process is often accompanied bya proliferation of theories, not as an exercise in Feyerabendian an-archy or Dadaism, but as a means of probing the possibilities and asa preliminary to developing a classification scheme that makes sys-tematic elimination a tractable exercise.20 The elimination is not ofthe simplcmindcd Sherlock Holmes variety, for it involves Bayesianelements, especially in the assessment of the auxiliary assumptionsneeded to bring about a confrontation of theory and experiment.Thus the Baycsianizcd version of the problem of consensus remains.And at the present time I do not see any resolution that does not fallback on something like the definitional solution, which I casuallydismissed in the preceding section. Such a fallback undermines sci-entific objectivity in a way that would not have pleased Carnap and,I presume, docs not please Kuhn cither. ,

10 Conclusion

I was a distant student of Carnap and a close student of Kuhn. Butthe two seemed to me so different in style and concerns that I placedthem in different parts of the philosophical firmament. Only nowhave I begun to appreciate how misguided my placement was andhow much philosophy of science can be enriched by considering howthe ideas of these two giants interact. I have presented one way tostage the interaction. There are surely better ones. I urge more ablehands to take up the task.21

33Carnap, Kulin, and the Philosophy of Scientific Methodology

Notes

Sections 6-9 of this paper arc based on chapter 8 of Earman 1992. I am grateful toRichard Jeffrey and Wcs Salmon for helpful comments on an earlier draft.

1. I will not atlcmpl<to'thaia(Jlcti*c^UÍ8sjdifferences between logical positivism and 'logical empiricism. Interms of adhcrcnls¡Slhc former includes the members of the jVienna Circle, while the latlcT-HwlwtlcsTTic members of the Berlin Society for Empirical \Philosophy. '

2. Or so it was thought until Ayer and others tried to spell out the conditions forvcrifiabilily. For a review of the problems encountered, see Hcmpcl 1950, 1951, 1965.

3. That is, confrontation of a statement with observation.

4. "Analog[iich] isl die Entiuicklung der wiisenschaftliclien Theoricn ill verslchen: nicht alsgcrichlcl auf ( ] die idéale, wahrc [?] Thcoric, die tint wahrc Thcoric ubcr dieWell [ ], sondcrn Enlwicklung al Schritt zu cincr bcsscrcn 1'orm, durch Auswnhlcincr aus incineren kompclicrcndcn die Auswahl gcschichl durch Bcvorzugung indcr community dcr Wisscnschafllcr, wobci allcrhand soziologi, kullurcllc usw. Fakto-re n milspiclcn. Nichl: »Wirkommcn dcr Wahrhcit nahcr,« sondcrn »Wir vcrbcsscrncin Instrument.» Archive for Scientific Philosophy, University of Pittsburgh, documentno. KG 082-03-01:1 r/1. Quoted by permission of the University of Pittsburgh; all rightsreserved. 1 am grateful to Pirmin Slccklcr-Wiclhofcr for providing the Englishtranslation.

5. Keep in mind that I'hilmo/ihical l'~ounrlatinns of Physics was compiled by MartinGardner. i'-> • ' ' , < • ' • • • ' • ' . • • • ' • ' , . ' • •"•'•••• . '..,',.,,-..' . . '

6. Davidson writes, "The dominant metaphor of conceptual relativism, that ofdirfcrcnlpoints of view, seems to betray an underlying paradox. Different points of view makesense, but only if there is a common coordinate system on which to plot them; yet theexistence of a common system belies the claim of a dramatic incomparabilily".(197<l,6).

7. See Kantian I OH!) for an evaluation of these claims.

8. In ibis period Carnap was under the illusion that the logic of science could bediscussed purely in terms of logical syntax, but the point 1 am making here holds withrespect to synlax and scmanlics. Carnap's 1930s strategy for dissolving philosophicalproblems appears in slightly new garb in his distinction between "internal" and "ex-ternal questions" (sec Carnap 1950).

9. Sec Earman 1986 for some caveats.

10. Fcigl's paper for the Schilpp volume was written in 1954. But due to delays, thevolume did not appear until 1963.

11. While the use-of this language may not be appropriate for understanding all thehistorical disputes, it docs help to illuminate the long running disputes over absoluteversus relational conceptions of space and lime (sec Earman 1989).

12. Here is a place where a resort to Carnapian subscripting may be healthy. I Use \"incoinmcnsurabilityi" to indicate Kulin's sense of incommensurability that derives

34John Karman

from changes in the lexicon, and 1 use "¡ncommcnsurability2" to stand for the kind ofincommensurability that makes theory choice impossible or difficult by means ofrelatively neutral observations. My claims arc that incommensurability) docs not implyincommensurability; and that as .1 matter of actual historical fact incommensurability:is not so bad in typical cases of scientific revolutions.

13. Since 1 have never been able to understand what is at issue here, I don't knowwhether I should demur.

H. Sec Carnap 1962, I963c, and 1968. Carnap was not a dogmatist on this matter.In his final published pronouncement on this matter he wrote, "When I say that theend result of inductive reasoning is not the acceptance of a hypothesis, but rather theassignment of a probability to the hypothesis, this is not meant as a description ofwhat is actually done, but rather as a proposal for a rational reconstruction. Therefore,although in the present controversy I agree essentially with Professor Bar-Hillcl [whoargues against rules of acceptance) against Professor Kyburg [who argues for rules ofacceptance], 1 am quite doubtful about one view in which they seem to agree, that wehave to choose between two irreconcilable positions. I do not think, as Kyburg docs,that our using or not using rules of acceptance (or detachment) makes a vast differencein our philosophy of science. Nor would I, like Bar-Hillcl, totally condemn such rules"(1968, 146), For the sake of a sharp contrast with Kuhn, I am presenting a Carnapwho would condemn rules of acceptance. Contrary to Carnap, I think that one'sattitude on this matter docs make a significant difference for one's image of science.

15. I have borrowed the phrase "tempered pcrsonalism" from Shimony (1970).

10. There is a bit of awkwardness here, since in Carnap's systems of inductive logicthe probability of theories for infinite domains will be flatly zero. Carnap was thusforced to talk about "instance confirmation" of theories. I will pass over this difficulty,since it is one that is peculiar to Carnap's language-based systems and docs not apply •to Uaycsianism in general.

17. For a detailed discussion of these matters, sec chapter 6 of Earman 1992.

18. Archive for Scientific Philosophy, University of Pittsburgh, document no. 084-16-01.

19. Sec chapter 7 of I'.arman 1992 for details.

20. Again, sec Earman 1992 for a discussion of how this exercise works for rclalivisticgravitational theory.

21. The able hands of Wesley Salmon have taken up the work (sec Salmon 1990).

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