Philosophical Naturalism Author(s): Michael Friedman Source: Proceedings and Addresses of the American Philosophical Association, Vol. 71, No. 2 (Nov., 1997), pp. 5+7-21 Published by: American Philosophical Association Stable URL: http://www.jstor.org/stable/3130938 . Accessed: 03/04/2011 12:50

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http://www.jstor.org PRESIDENTIALADDRESSES

OF

THE AMERICANPHILOSOPHICAL ASSOCIATION

1996-97

Michael Friedman Philosophical Naturalism

Stanley Cavell Something Out of the Ordinary

Henry E. Allison We Can Act Only Under the Idea of Freedom PHILOSOPHICALNATURALISM MichaelFriedman, Indiana University PresidentialAddress delivered before the Ninety-FifthAnnual Central Division Meetingof TheAmerican Philosophical Association in Pittsburgh, PA, on April 25, 1996.

I want to discuss a tendency of thought which has been extremely widespread withinAnglo-American philosophy during the lasttwenty years or so-but which now,if I am not mistaken,has reachedthe end of its usefullife. Thistendency of thought,which I willcall "philosophicalnaturalism," is characterized by two mainideas. Thefirst is the rejectionof anyspecial status for types of knowledge traditionallythought to be a priori-knowledgein logic and mathematics,for example-in that all knowledgewhatsoever is now conceived as having fundamentallythe same statusas thatfound in the empiricalnatural sciences. Thus MichaelDevitt, in a recentbook devoted to whathe calls a "naturalistic" programin semantics and philosophy of language,defines naturalism as theview that"there is only one way of knowing,the empiricalway that is the basis of science,"so that"from a naturalisticperspective, we shoulddeny that there is any a prioriknowledge."1 Lying behind this view, as Devittmakes abundantly clear, is an holisticpicture of the relationshipbetween knowledge and experience now associated with the names of Duhemand Quine. The totalityof human knowledgeis picturedas a vast web of interconnectedbeliefs on which experienceor sensory input impinges only along the periphery.When faced with a "recalcitrantexperience" standing in conflictwith our overall system of beliefs we thenhave a choiceof where to makerevisions. These can be maderelatively close to the peripheryof the system (in whichcase we make a change in a relativelylow-level part of naturalscience), but they can also-when the conflict is particularlyacute, for example-affect the mostabstract and general parts of science, includingeven thetruths of logicand mathematics, lying at the centerof oursystem of beliefs. To be sure, such high-levelbeliefs at the center of our systemare relatively entrenched, in that we arerelatively reluctant to revisethem or to give them up. Nevertheless,and this is the crucialpoint, no belief whatsoeveris forever"immune to revision."2 The second main idea of what I am calling philosophical naturalism is the view that philosophy, as a discipline, is also best understood as simply one more part-perhaps a peculiarly abstract and general part-of empirical natural science. Thus David Papineau, in a recent book entitled Philosophical Naturalism, characterizes such naturalism as the view that we should "set philosophy within science," so that philosophical investigation as such "is best conducted within the framework of our empirical knowledge of the world."3And Quine's program of "epistemology naturalized," whereby "epistemology, or something like it, simply falls into place as a chapter of psychology and hence of natural science,"4 provides the best known example of how to realize this general idea. Moreover, there is a close connection, as Quine himself explains, between this idea of setting philosophy within natural science, on the one hand, and the rejection of a priori knowledge on the basis of epistemological holism, on the other. Ifall human knowledge is basicallyof the same type, and no knowledge,

- PROCEEDINGS AND ADDRESSES OF THE APA, 71:2 - 7 - PRESIDENTIALADDRESS OF THE CENTRAL DIVISION- in particular, is forever immune to revision, then there is no higher or firmer type of knowledge than that found in empirical natural science itself. There is no Archimedean point from which philosophy could hope to justify natural science from some better grounded and more certain perspective. The traditionaldream of providing a philosophical justification for scientific knowledge must therefore be given up, and thus there is no longer any reason for attributinga special status and role to philosophy. A version of this last argument is the centerpiece of Quine's "Epistemology Naturalized." On the basis of the failure of Carnap's program for logically reconstructing science out of sensory experiences in Der logische Aufbau der Welt, Quine rejects the entire Carnapian enterprise of logical analysis or rational reconstruction as such:

But why all this creative reconstruction, all this make-believe? The stimulation of his sensory receptors is all the evidence anyone has had to go on, ultimately, in arriving at his picture of the world. Why not just see how this construction really proceeds? Why not settle for psychology? Such a surrender of the epistemological burden to psychology is a move that was disallowed in earlier times as circular reasoning. If the epistemologist's goal is validation of the grounds of empirical science, he defeats his purpose by using psychology or other empirical science in the validation. However, such scruples against circularity have little point once we have stopped dreaming of deducing science from observations.5

Given the failure of the Aufbau's program for logically translating all concepts of empirical science into purely sensory terms, Quine continues: "[l]twould seem more sensible to settle for psychology. Better to discover how science is in fact developed and learned than to fabricate a fictitious structure to a similar effect.6 In the context of Carnap's actual motivations for his own program of logical reconstruction, however, this particular Quinean stratagem is extraordinarily misleading. For, in the first place, neither in the Aufbau nor in his later works did Carnap set himself the goal of grounding, justifying, or "validating"science from some supposedly higher and more certain philosophical vantage point. Indeed, Carnap himself was always perfectly happy to depend on the best results of current empirical research (he explicitly depends on the results of Gestalt psychology in the Aufbau, for example), so that the foundationally motivated strictures against circularityQuine rejects here were never part of Carnap's own motivations. And, in the second place, even after Carnap himself rejects the Aufbau's program of logically reconstructing science from a purely sensory basis, he nevertheless continues to emphasize, in even stronger and more insistent terms, that philosophy as he conceives it is an a priorior formal discipline whose specialprovince is logicalanalysis rather than empirical investigation.7 Even if the particularlogical reconstruction of science envisionedin the Aufbaucannot in fact be carriedout, we can stilldevote ourselvesto articulatingthe logical

8 - PROCEEDINGS AND ADDRESSES OF THE APA, 71:2 - - PRESIDENTIALADDRESS OF THE CENTRAL DIVISION- structure or logical framework within which empirical natural science proceeds. Inthis way, what Carnap is now calling Wissenschaftslogik is itself a purely logical or analytic discipline, wherein the correspondingly analytic formal scaffolding of synthetic or empirical natural science is to be clearly and precisely delineated. That the particular delineation attempted in the Aufbau cannot, for technical reasons, be carried out in no way undermines the general possibility of Wissenschaftslogikas such. What does seriously challenge Carnap's characterization of philosophy as Wissenschaftslogik is Quine's attack on the first of the notorious "two dogmas of empiricism"-the doctrine, that is, that there is a clear and sharp distinction between formal, logical, or analytic truth, on the one side, and factual, empirical, or synthetic truth, on the other. The second "dogma of empiricism" is of course the doctrine of what Quine calls "radical reductionism"-the doctrine that each individual statement of natural science has its own particular range of confirmational sensory experiences via an Aufbau-style logical translation. This doctrineis ofcourse threatened by Duhemian epistemological holism, but it is not, pace Quine,identical to the analytic/syntheticdistinction.8 Indeed, in the period when Carnapputs the mostweight on the analytic/syntheticdistinction and the accompanyingidea of philosophyas Wissenschaftslogik,Carnap himself explicitlyadopts epistemological holism (which he associateswith the namesof Duhemand Poincar6).Accordingly, Carnap himself explicitly maintains that any statementof science-even the statementsof logicand mathematics-canbe revisedin responseto problematicempirical evidence, and thus Carnap himself explicitlymaintains that no statementof science is foreverimmune to revision.9 Itis justthat for Carnap, in contrast to Quine,there remains, nonetheless, a sharp distinctionbetween revisionsof languageor linguisticframework, in which analyticstatements depending solely on the meaningsof the relevantterms are revised,and factualrevisions within a given languageor framework,in which syntheticstatements expressing contentful assertions about the empiricalworld are revised. NowQuine's attack on the notionof analytictruth-on the notionof truthin virtueof meaning-does (despiteits confusionwith his attackon the doctrineof radicalreductionism) pose a seriouschallenge to Carnap'sformulation of the distinctionbetween revisions of linguisticframework, on theone side, andfactual revisionsof empiricalstatements formulated within a givenframework, on the other.10Quine's attack on the notionof analytictruth thus challengesboth Carnap'sexplanation of the speciala prioristatus of logicand mathematics(as truthsflowing simply from the adoptionof a given linguisticframework) and Carnap'sexplanation of the special, non-empiricalstatus of philosophy(as a branchof appliedlogic, as Wissenschaftslogik).So itis thisattack-not the idea of epistemologicalholism and the doctrinethat no statementof science is immuneto revision-that providesthe strongestsupport for contemporary philosophicalnaturalism. Indeed, as we havejust seen, epistemologicalholism andthe rejectionof allabsolute unrevisability is perfectly compatible, in Carnap's own hands, with both a sharp distinctionbetween a prioriand empirical

- PROCEEDINGSAND ADDRESSES OF THEAPA, 71:2 - 9 - PRESIDENTIALADDRESS OF THE CENTRAL DIVISION- knowledge in general and a sharp distinction between philosophy and empirical natural science in particular. Quine's attack on the notion of truth in virtue of meaning culminates, as is well known, in his doctrine of the indeterminacy of translation, wherein the very notion of determinatemeaning, as ittraditionally functions in philosophy,is rejectedas scientificallyillegitimate. From this point of view,all that remains of thetraditional notionof analytictruth is the franklyersatz notionof a "stimulus-analytic" sentence-which receives communitywide assent no matterwhat the given sensorystimulation. And, from this point of view,it follows that 'There have been blackdogs' is justas stimulus-analyticas '2+2=4'.According to the doctrineof the indeterminacyof translation,then, all that is leftof the traditionalnotion of a prioritruth is the notionof relative(community wide) entrenchment.11 Itis inthis sense thatQuine's attack on the notionof truthin virtueof meaningculminates in philosophicalnaturalism. Butwhat is translationunderdetermined by? Invirtue of what (more precisely, in virtueof the lackof what)is the traditionalnotion of meaningscientifically illegitimate?In response to a sharpchallenge on exactlythis pointfrom Noam Chomsky,Quine explains that translation,and thus the traditionalnotion of meaning,is underdeterminedby the totalityof truthsof naturalscience:

Thus,adopt for now my fullyrealistic attitude toward electrons and muons and curvedspace-time, thus fallingin with the currenttheory of the world... Consider,from this realisticpoint of view, the totalityof truthsof nature,known and unknown, observableand unobservable,past and future. The pointabout indeterminacyof translationis thatit withstands all this truth, the whole truth about nature.12

Quine's attack on the notion of truth in virtue of meaning, his correlative rejection of the Carnapian distinction between a prioritruth and empirical truth, and his consequent articulation of philosophical naturalism, thus rests, in the end, on a starkly physicalistic conception of modern natural science as the standard and measureof alltruth as such. Andit is justthis conception, taken in a looserand more general sense, which then undergirds our current philosophical climate in which philosophical naturalism appears to be all but intuitivelyself-evident. From the point of view of modern natural science there can appear to be no room, as itwere, foreither a special status forlogic and mathematicsor a special status for philosophy. The only kindof truthit now appears possible to envision is just that of empirical natural science itself, and any other putative type of truth now appears to be shrouded in mystery.13

Let us consider this philosophical gloss on the preeminent status of modern natural science more closely. And let us begin by considering those truths of modern natural science given paradigmatic status by Quine-truths about

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"electronsand muons and curved space-time." How, in particular, did the notion of curvedspace-time, which, as is well known,is centralto Einstein'sgeneral theoryof relativity,actually arise and develop? Thegeneral relativistic conception of curvedspace-time is the productof two fundamentaldevelopments in late nineteenth century mathematics: Felix Klein's group-theoreticalincorporation of the classical non-Euclideangeometries of constantcurvature (including the Euclideancase of constantzero curvature) into the moregeneral framework of projectivegeometry, and BernhardRiemann's even morerevolutionary articulation of a generaltheory of manifoldsof arbitrary dimensionand curvature-including the hithertouncontemplated case of spaces of variablecurvature. It was the firstset of developmentsthat led Hermann Minkowskito interpretEinstein's 1905 special theory of relativityas describinga four-dimensionalgeometry-in Minkowski'slanguage, an "absoluteworld"-in whichthe Lorentztransformations linking inertial reference frames in Einstein's theoryare conceivedas constitutinga Kleiniangroup of a geometryof zero curvatureclosely analogous to Euclideangeometry. In this way, Einstein's radical thesis of the relativityof simultaneity,which rejects Newtonian absolute time existingindependently of space and motion,is interpretedas the assertionof a fundamentallynew type of physicalreality: "Henceforth space by itself,and time by itself,are doomedto fade awayinto mere shadows, and only a kindof union of the two will preservean independentreality."14 Yet such a Minkowskian four-dimensionalframework, as Einsteinsoon cameto realize,is inadequatefor a theoryof gravitation. The relativistic theory of gravitation Einstein finally brought to completionin 1916 adds Riemann'sideas on arbitrarymanifolds of variable curvatureto the initialframework of whatwe now call Minkowskispace-time. Gravitationis interpreted as a perturbationof the underlyingMinkowski geometry by the distributionof matterand energywithin space-time so that,in particular, the trajectoryof a bodyin a gravitationalfield is nowconceived as a maximally straightcurve or geodesic-in Minkowski'slanguage, a maximallystraight "world-line"-ina four-dimensionalgeometry of variablecurvature. It is in this way thatthe notionof curvedspace-time first entered modern physics. And,as is well known,this notionbecame generally accepted within modernphysics on the basis of a smallnumber of experimentaltests-the most famousof whichwas the confirmationof Einstein'spredictions for the deflection of lightin a gravitationalfield by observationsmade during a totaleclipse of the sun by the BritishSolar Expeditions led byArthur Eddington in 1919. Itis inthis way that the generaltheory of relativity,including the fundamentalnotion of curvedspace-time, first faced, in Quine's words, the "tribunal of experience."But the crucialquestion, from our point of view, concerns the status of the mathematicalmachinery of general relativityin such experimentaltests. Eddington'sresults on the deflectionof lightcertainly confirm, or were takento confirm,Einstein's particular field equations governing the relationshipbetween mass-energydensity and space-timecurvature. (More precisely, they confirm the so-called Schwarzschildgeometry in the neighborhoodof the sun, whichis one particularsolution to Einstein'sequations.) Butdo they also confirmthe Kleiniantheory of transformationgroups and the Riemanniantheory of

- PROCEEDINGSAND ADDRESSES OF THEAPA, 71:2 -- 11 - PRESIDENTIALADDRESS OF THECENTRAL DIVISION - n-dimensional manifoldsconstituting the mathematicalbackground to general relativity? Even if we are willingto speak in terms of differingdegrees of "entrenchment"here, does itreally make sense to envisiona processof empirical testingin which even thismathematical background somehow equally faces the "tribunalof experience"? I submitthat this way of lookingat the matterdoes not make sense-and not simplybecause no sane physicistor mathematicianwould describe the situation in this way. The fundamentalproblem is thatgeneral relativity is not happily viewedas somethinglike a largeconjunction, such that one conjunctis givenby Einstein'sfield equations, another conjunct is given by the Kleiniantheory of transformationgroups, and a thirdconjunct is givenby the Riemanniantheory of manifolds-wherewe then view Eddington'sexperimental results, say, as potentiallyspreading empirical confirmation over the entire conjunction.15 Rather, the mathematicalbackground of Einstein'stheory functions as a necessary presuppositionof thattheory, as a meansof representationor a language,as it were, withoutwhich the theorycould not even be formulatedor envisioned as a possibilityin the firstplace. To see this, let us firstconsider the situationin the seventeenth and eighteenth centuries, during the heyday of the Newtoniantheory of gravitation. In this context, the modern concept of space-time simply does not exist. Space is represented by a three-dimensionalgeometry (Euclidean geometry is of course the only possibility),time is an entirelyseparate independentvariable used to parametrizethree-dimensional spatial trajectories, and gravitationis represented by a three-dimensional force acting immediately across arbitrary three-dimensional spatial distances. In this context, the general theory of relativitycould not even be formulated,let alone be subject to empiricaltest. It is not that Newton'stheory is adopted in preferenceto Einstein'son the basis of the then availableevidence; the lattertheory simply does not yet belong among the conceivable alternatives. Conversely,let us now considerthe situationfrom the point of view of the space-time physics of the twentiethcentury. In this context, we see that we can now formulateall the theories of interest to us here-Newtonian physics, special relativity,general relativity-withinthe same four-dimensionallanguage. Newtonianphysics, too, can now be representedas a space-time theory, postulating a different structure for space-time-one containing counterparts of absolute time and absolute space-from that postulated by either special relativityor general relativity. Indeed, as the mathematician Elie Cartan showed in the 1920s, we can even formulate Newtoniangravitation theory using variably curved space-time, just as in general relativity.From this pointof view it is thencrystal clear that the mathematical machinerywithin which the conceptof curvedspace-time is formulatedis partof the meansof representationor languageof generalrelativity and not partof its empiricalcontent. For all the theories in question here-which differwidely, of course, in empirical content-are now formulated within the very same mathematicallanguage. Kant understood a prioriknowledge as supplying the presuppositions or conditionsof possibilityof empiricalknowledge-as thatwhich makes it possible

12 - PROCEEDINGSAND ADDRESSES OF THEAPA, 71:2 - - PRESIDENTIALADDRESS OF THECENTRAL DIVISION - to formulateand justify objective empirical claims about sensibly given nature in thefirst place. AndKant modelled his particular theory of these a prioriconditions of the possibilityof objectiveexperience on the Newtonianmathematical physics of hisday-on Newtonianspace, Newtoniantime, and the Newtonianconception of matter,force, and interactionencapsulated in the laws of motion and exemplifiedin universalgravitation. At one place, Kanteven comparesthis a prioriframework to a language-as thatwhich makes it possiblefor us "tospell outappearances, in order to be ableto readthem as experience."16We learned in the late nineteenthand early twentieth centuries, however, that the particular a prioriframework envisioned by Kantis notthe onlypossible such framework. And we learnedthis, of course, on the basis of preciselythe sequence of revolutionarydevelopments in both mathematics and mathematical physics briefly sketchedabove. We therebylearned, without a doubt,that such conditionsof possibilityor necessarypresuppositions of empiricalnatural science shouldnot be viewedas rigidlyfixed for all time, as foreverimmune to revision.It does not follow, however, that such mathematicalframeworks no longer have the characteristic"constitutive" function Kant first articulated-the function of making the rigorousformulation and confirmation of properlyempirical theories in natural science firstpossible. On the contrary,as we havejust seen, thisis emphatically stillthe case in the generaltheory of relativity,where it is simplynot possible eitherto formulateor empiricallyto test Einstein'sfield equations without the revolutionarynew mathematical framework due ultimatelyto Riemannand Klein. Nowsuch a generalizationand relativizationof the Kantiana priori,whereby it loses its rigidlyfixed character but retains its essential"constitutive" function with respect to empiricalknowledge, was in fact commoncoin withinlate nineteenthand earlytwentieth century scientific philosophy-most importantly, forour purposes, among the philosophersnow known as logicalpositivists. Thus Reichenbach,for example, distinguishedtwo meanings of the Kantiana priori-necessary and unrevisable,fixed for all time, on the one hand, "constitutiveof the conceptof the objectof [scientific]knowledge," on the other.17 He argued,in thiscontext, that the greatlesson of the theoryof relativityis that the formermeaning must be droppedwhile the lattermust be retained.Relativity theory, that is, involves a priori constitutiveprinciples as necessary presuppositionsjust as much as does Newtonianphysics; it is just that mathematicalphysics has changedits constitutive principles in the transition from the lattertheory to the formerone. Andit was Carnapwho broughtthis new, relativizedand dynamical conception of the a priorito itsmost precise expression via his formallycharacterized distinction, briefly noted above, between revision of languageor linguisticframework, on the one side, and revisionof empirical statementsformulated within a givenlinguistic framework, on the other. As we also observedabove, Quineanconsiderations about revisability and epistemologicalholism do not,by themselves,touch this new conceptionof the a prioriin the slightest. Indeed, revolutionary scientific changes, wherein the very backgroundframework or language within which empirical scientific theories are formulateditself undergoes radical transformation, provide this conception with its primarymotivation and its strongestcorroboration. In the case of the radical

- PROCEEDINGSAND ADDRESSES OF THEAPA, 71:2 - 13 - PRESIDENTIALADDRESS OF THECENTRAL DIVISION - conceptualtransformation culminating in the theory of relativity,for example, we see thatboth mathematics and mathematical physics have undergone profound revolutionarychanges. Nevertheless,although these two sequences of developments-mathematicaland physical-indeed come together in a striking anddramatic fashion in the physicaltheory of generalrelativity, they still remain separateand distinctsequences evolvingaccording to theirown characteristic dynamics.The mathematical developments are driven largely by considerations ofconceptual generalization and unification internal to mathematics,togetherwith fruitfulnew results obtainablewithin mathematics by purelymathematical methods-methods which of course involve no appeal whatsoever to experimentalor observational testing-whereas the developments in physics, by contrast,are self-consciouslydriven by preciseexperimental results. And in all thisthe mathematicaldevelopments constitute the necessarypresupposition or conditionof possibilityof the physicaldevelopments, in that the formulationand preciseexperimental confirmation of the latterwould not even be possiblein the firstplace withoutthe former. It is no wonder,then, thatwe find in Thomas Kuhn'stheory of the natureand character of scientificrevolutions-in the central Kuhniandistinction between change of paradigm,on the one side, and normal science,on the other-an informalcounterpart of Carnap'sformalized distinction between change of language or linguisticframework and rule-governed operationscarried out within such a framework.18Although Carnap's particular formalizationhas notin fact survived, the historicaland philosophical relevance of thisdistinction for properly understanding the natureand evolution of modern naturalscience has in no way been therebydiminished. We can deepen and generalizeour appreciationof the characteristically constitutiverole of mathematicswithin modern natural science, finally,by glancingback briefly at the scientificrevolution of the sixteenthand seventeenth centurieswhich initiated it. Forit was at thispoint, in the work of suchthinkers as Kepler, Galileo, Descartes, Huygens, and Leibniz, that the very idea of a thoroughgoingmathematical description of sensible nature first gained wide currency. It was at this point,that is, that the previouslydominant Aristotelian ideal of a largelyqualitative and teleologicaldescription of our experience of the naturalworld was overturnedin favorof the new ideal-constitutive of all modern physics-of a mathematicallyexact descriptionbased on geometry and laws of motion. This radicalconceptual revolutionprofoundly transformed our idea of whatit means for scientific statements to face thetribunal of experience-forthis idea was now interpretedas requiringthe deduction of precise mathematical resultswhich could then be subjectto correspondinglyexact proceduresof testing and measurement. And, as I hope to have made amplyclear, in this meaning it simplymakes no sense at allto assertthat the mathematicalbackground itself also faces the tribunalexperience.19 Blindness to this simpleyet fundamental point-and thus blindnessto the characteristicstatus and functionof whatwe mightcall the constitutivea priori20-onthe basis of a philosophicalconception thatprides itself on takingmodern natural science as the paradigmof knowledge ingeneral, is perhapsthe most peculiar, and, I am tempted to say, mostperverse, legacy of contemporaryphilosophical naturalism.

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We have seen that the idea of a special a priorirole for the mathematical disciplinesin our naturalscientific knowledge is alive and well in post-Newtonian mathematicalphysics and post-Kantian scientific philosophy. This idea has nothing to do with a jejune obsession with epistemic certainty, unshakable foundations,or absolute unrevisability. On the contrary, itis motivatedthroughout by an appreciationof the manifoldpossibilities for development,growth, and radicaltransformation in both pure mathematicsand mathematicalnatural science-and by an appreciation,above all, of the strikingand unexpected ways inwhich these twotypes of developments can influenceand even mergewith one anotherin the course of revolutionaryconceptual changes such as those exemplifiedin the theoryof relativity.It remainsimportant, nonetheless, to recognizethat mathematicalconceptual revolutions and physicalconceptual revolutionsare notthe same-and, in particular,that, in precisely such cases as the theoryof relativity,mathematics, however revolutionary incontent, continues to functionas a meansof representationor condition of possibilityfor the physical principleswhich are therebysubject to exactempirical tests. We havealso seen thatall of these ideas are givenprecise logical expression in the philosophyof formallanguages or linguisticframeworks developed by Carnap,a philosophy which,as we notedat the very beginning,is in no way motivatedby traditional concernsfor certainty, justification, or philosophical"validation." And, whereas Carnap'srepeated attempts to fashionan explicitlogical characterization or explicationof the distinctionbetween a prioriand empiricaltruth have indeed fallenprey to Quine'spenetrating attack on the analytic/syntheticdistinction, it does notfollow that we shouldsimply close oureyes to the historicalrealities of scientificpractice on behalfof a blandlyundifferentiated philosophical holism. Ifpost-Kantian scientific philosophy no longeraims at supplyinga foundation or "validation"of scientific practice, however, then what role remains left for it? Are we not faced, once again,with the idea that philosophy,as a discipline, shouldsimply be absorbedinto empirical natural science-that it should,for example,become that branchof the empiricalstudy of actualhuman beings where, in Quine'swords, "[w]e are afteran understandingof science as an institutionor processin the world, and we do notintend that understanding to be any betterthan the science whichis its object?"21Here, I believe,we can again derivean importantclue fromthe Carnapiandistinction between change of linguisticframework and rule-governedoperations within a given such framework-thedistinction, in other words, between what Carnap calls external and internalquestions. For Carnapheld that it is the characteristicfate of philosophyto be entangledwith external questions-with questions, in particular, aboutwhich linguistic framework should be adoptedfor the totallanguage of science. Such questions,Carnap further held, can in no way be settled by theoreticalconsiderations, by either rules of evidence and confirmation characteristicof factualor empiricalscience or rules of deductionand proof characteristicof formalor mathematicalscience. Externalquestions considered in philosophy are therefore purely practicalquestions, and, as such, they are

- PROCEEDINGSAND ADDRESSES OF THEAPA, 71:2 - 15 - PRESIDENTIALADDRESS OF THE CENTRAL DIVISION- answered, not by theoretical assertions, but by practical proposals to adopt one or another form of language. I would put the guiding thought behind this Carnapian characterization of the peculiar role of philosophy as follows. In empirical natural science, as we have seen, we proceed against a background of concepts and principles-typically, mathematical concepts and principles-which constitute the framework or language of our inquiry. In particular, these concepts and principles make the rigorous formulation and testing of particularempirical hypotheses first possible, and, in this sense, they help to define what success or failure within this inquiry amount to. As such, the background framework in question contributes to the norms and standards of the discipline-norms and standards which, in the normal course of affairs, are generally taken for granted by the practitioners of the discipline. (In Kuhnian language, then, we are here concerned with elements of a paradigm definitive of a particular part or episode of normal science.) In pure mathematics, too, we typically operate against the background of generally agreed upon definitional stipulations and methods of proof-which, in a Carnapian-style rational reconstruction, would appear as primitivevocabulary, primitiveaxioms, and primitiverules of inference. And, in both cases, it is precisely the presence of such a generally agreed upon and taken for granted background that makes possible an inquirywe can honorificallycharacterize as "scientific"-that is, as progressive, as problem solving, and as capable of wide if not universal consensus. It may also happen, however, that we have occasion to step back and reflect upon such a taken for granted background of disciplinary norms and standards. We may have occasion, that is, to call such norms and standards into question and to ask ourselves why precisely these concepts and principles should govern ourinquiry. Indeed, during periods of deep revolutionarychange it is justsuch questionsthat come to the foreground.Older constitutive principles (in Kuhnian terms,older paradigms) are challenged,new constitutive principles (in Kuhnian terms,new paradigms) are suggested. As Carnapwould put it, we arenow faced withan externalquestion concerning the replacement of one linguisticframework by another. How, then, can we decide such a question? We cannot, by definition,appeal any longerto a generallyagreed upon and taken for granted constitutivebackground, for it is justsuch a backgroundthat has nowbeen called intoquestion. We are thus no longerdealing with purely scientific questions in the above sense-that is, we are no longeroperating wholly within what Kuhn calls normal science-and it is precisely here that characteristically philosophical considerations come into play. Let us illustrate these ideas with a couple of examples. Consider first the revolutionary conceptual changes of the sixteenth and seventeenth centuries which initiated modern natural science as we know it. These events certainly involveda numberof instancesof strikingempirical success in providingexact mathematicalrepresentations of naturein the modernstyle-notably, Kepler's new planetaryastronomy (building, to be sure,on a longmathematical tradition) andGalileo's mathematical description of projectilemotion (which was, inits own right,almost entirely new). Nevertheless,the ambitionsof this new intellectual

16 - PROCEEDINGS AND ADDRESSES OF THE APA, 71:2 - -PRESIDENTIAL ADDRESS OF THE CENTRAL DIVISION- movementfar exceeded its grasp. Forone here aimedat nothingless thana precise mathematicaldescription of all of the phenomenaof nature,to be achievedby an atomisticor corpuscular theory of matterthat reduced all natural changes to the motionsand mutualimpacts of the constituentparticles. And nothingeven approximatingsuch an atomisticreduction was actuallyachieved untilthe late nineteenthand earlytwentieth centuries-when, we mightadd, it was achievedusing entirely new and hithertoentirely unforeseen mathematical andphysical concepts. So itwas notsimply empirical and mathematical success inthe modernstyle that motivated and sustained this intellectual movement. On the contrary,during its first fifty years especially, the intellectualmovement which initiatedmodern natural science supporteditself, above all, on the new system of natural philosophy fashioned by Descartes-a philosophy which not only sketched a complete program for a new, geometrical physics, but which also undertook the task of radically revising and reorganizing the wider system of philosophical concepts and principles bequeathed to western thought by Scholasticism (involving such concepts as substance, force, space, time, matter, mind, creation, divinity). Virtuallyall of the important thinkers of the period-for example, Huygens, Leibniz, and even Newton-began their intellectual careers as disciples of this new philosophical system. And, if they were later radically to reviseor even to rejectit, it still cast a longand indelible shadow across their own intellectualcontributions-to such an extent,in fact, that these contributionsare almostimpossible to conceiveexcept against this Cartesian background. For a second example,consider once again the relativisticrevolution in physicswrought by Einstein.It is wellknown that purely empirical considerations playeda decidedlysecondary role here. Notonly did Einstein entirely ignore the celebratedexperiment of Michelsonand Morleyin his 1905 paperon special relativity,but there was on the scene a fullydeveloped competitor theory-the Lorentz-Fitzgerald"aether" theory-which was empirically equivalent to Einstein's theory. Einsteinhimself cites a varietyof philosophicalinfluences on his thinking-including,especially, the "critical" and "skeptical" philosophies of Hume and Mach.22With the benefitof hindsight,however, we can say that the philosophicalideas of the great French mathematicianand mathematical physicistHenri Poincare (who was of coursedeeply involved with the problems in electrodynamicsaddressed by special relativityand who Einsteinwas intensivelyreading at the time)were of perhapseven moreimportance.23 For Poincar6had arrived, on the basisof hisown fundamental mathematical work on non-Euclideangeometry, at the idea that geometryis neither(pace Kant)a synthetica prioriproduct of pureintuition nor (pace Gauss and Helmholtz)a straightforwardempirical description of what we can experiencein nature. Establishingone or anothersystem of geometry,according to Poincare,rather requiresa freechoice, a conventionof ourown in orderto bridgethe irreducible gulfbetween our crudeand approximatesensory experience and our precise mathematicaldescriptions of nature.There is no doubtthat Einstein found this idea to be tremendouslyliberating, and it appears that itwas this idea, above all, thatstimulated him to viewthe conceptof simultaneity,not as a simpledatum of immediateintuition or experience, but ratheras something to be fixed

- PROCEEDINGS AND ADDRESSES OF THE APA, 71:2 - 17 -PRESIDENTIALADDRESS OF THECENTRAL DIVISION - axiomatically by definition as part of the framework of a new proposed kinematics.24Although Einstein was later,through his workon the generaltheory, to movedecisively beyond Poincare's conventionalist philosophy of geometry,it is, once again,almost impossible to conceiveEinstein's initial liberating move withoutthis philosophicalbackground. Philosophy does not function,in such cases of fundamentalconceptual transformation, as a firmeror morecertain sourceof knowledgewhich we can thenuse to justifyor "validate"the scientific changes in question. Nordoes it proceedin splendidisolation, independent of the scientificdevelopments themselves. Descarteswas motivatedin his new system of naturalphilosophy by earlier scientificdiscoveries-notably, by Copernicanastronomy and by his own discoveryof whatwe now call analytic geometry. Poincare,as we just observed,was motivatedby his own purely mathematicalwork in non-Euclideangeometry and was himselfdeeply involved withthe newlyemerging foundations of electrodynamics.Philosophy rather functionshere at one levelremoved, as itwere, from conceptual transformations within the sciences. It operates in an environmentwhere a new constitutive framework(a newscientific paradigm) is notyet in place,and itsuggests ideas, concepts,principles, and programs-typically of a less precisebut more general characterthan the scientificconstitutive frameworks themselves-which can motivateand support the pursuitof one such constitutiveframework rather than another.In this sense, ifscientific conceptual revolutions take place at one level removedfrom what Kuhn calls normal science, philosophy operates rather at two levels removed. Carnapcharacterizes the answerswe mightreasonably attempt to give to philosophicalquestions as bothconventional and purely pragmatic. He thereby emphasizesthe elementof free decision-thatwe are here not boundby fixed and antecedentlyagreed upon rules-as well as the fundamentallypractical characterof such questions-that, as a consequence,we are governedby standardsof utilityand expediencyrather than truth. To this I wouldadd the provisothat standards of utilityand expediency are themselvesoften at issue in such cases-that the realproblem is oftento decidewhat we willnow count as fruitfulor successful. Ourproblem is rationallyto negotiatenew standardsor idealsof fruitfulnessand success, andnot simply to estimatethe probabilitiesof achievingalready clear and agreed upon goals on the basis of acceptedempirical results. I would also add a fundamentally historical dimension to our understandingof philosophicaltheorizing. In formulating new philosophicalideals we typically react to, and operate against the background of, previous philosophical ideals-as Descartes operated against the background of Scholastic naturalphilosophy or Poincare operated against the backgroundof bothKantianism and empiricism.Philosophy thus not onlyfunctions at a different level than the scientific disciplines, but also within its own characteristic intellectualcontext. Lyingat the basis of contemporaryphilosophical naturalism is the Quinean pictureof the totalityof humanknowledge with which we began. Ourknowledge is picturedas a vast web of beliefs, which responds as a total system to the impactof sense experience along the periphery,and withinwhich, accordingly,

18 - PROCEEDINGSAND ADDRESSES OF THEAPA, 71:2 - - PRESIDENTIALADDRESS OF THECENTRAL DIVISION - the only relevantdistinctions we can make involvedegrees of centralityand thus of entrenchment. Let me suggest, as an alternative,the pictureof a dynamical system of beliefs, concepts, and principlesthat can be analyzed, for present purposes, intothree maincomponents: an evolvingsystem of empiricalnatural scientificconcepts and principles,an evolvingsystem of mathematicalconcepts and principleswhich frame those of empiricalnatural science and make their rigorousformulation and precise experimentaltesting possible, and an evolving system of philosophicalconcepts and principleswhich serve, especially in periods of conceptual revolution,as a source of suggestions and guidance in choosing one scientific frameworkrather than another. All of these systems are in continualdynamical evolution, and it is indeedthe case that no concept or principleis forever immuneto revision. Yet we can nonetheless clearly distinguishthe radicallydifferent functions, levels, and roles of the differing componentsystems. In particular,although the threecomponent systems are certainlyin perpetual interaction, they nonetheless evolve according to theirown characteristicdynamics. Onlyin the case of the empiricalnatural scientific system, for example, do precise experimentaltests functionas relevant dynamicalfactors-only here do our beliefs,in this sense, squarelyface the tribunalof experience.Both in mathematics and in philosophy, by contrast, freely creative responses to precedingintellectual developments are the primary enginesof change. Inall this, however, what is moststriking and inspiring are the periods of profoundconceptual transformation where each of the three componentscontributes its owncharacteristic involvement in those revolutions of thoughtthat figure among the very highest achievements of our intellectual life. Notes

1. M. Devitt,Coming to Our Senses: A NaturalisticProgram for Semantic Localism,Cambridge, 1996, pp.2, 49. 2. See W.V. Quine,"Two Dogmas of Empiricism,"inhis Froma LogicalPoint of View,Cambridge, Mass., 1953, ?6. 3. D. Papineau,Philosophical Naturalism, Oxford, 1993, p. 5. 4. Quine,"Epistemology Naturalized," in his OntologicalRelativity and Other Essays, NewYork, 1969, p. 82. 5. Quine, op. cit., p. 75-76. 6. Quine,op. cit., p. 78. 7. Inthe mostexplicit polemic against psychologism Carnap everwrote, "Von der Erkenntnistheoriezur Wissenschaftslogik," inActes du Congrdsinternational du philosophiescientifique, Paris, 1936, Carnapdepicts scientific philosophy as goingthrough three main stages of development:the firstis the transitionfrom speculativephilosophy or metaphysicsto epistemology,the second is the rejectionof the synthetica prioriand the transition to an empiricistepistemology, the thirdand final stage is thetransition from epistemology to the logicof science [Wissenschaftslogik].The mainproblem here is to realizethat epistemology as practicedso far-includingin Carnap's own earlier work-is an "unclearmixture of psychologicaland logicalconstituents" (p. 36).

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8. I thus cannotfollow Quine in his assertion,"Two Dogmas," p. 41, that"[t]he twodogmas are, at root,identical." 9. R. Carnap,The LogicalSyntax of Language,trans. A. Smeaton,London, 1937, ?82. 10. CompareCarnap, "Empiricism, Semantics, and Ontology,"in his Meaning and Necessity,Chicago, 1956, footnote 5 on p. 215. 11. See Quine,Word and Object,Cambridge, Mass., 1960, ?14. 12. Quine,"Reply to Chomsky,"in Wordsand Objection: Essays on the Workof W. V. Quine,ed. D. Davidsonand J. Hintikka,Dordrecht, 1969, p. 303. 13. A good example of this more general physicalistictendency is Paul Benacerrafsinfluential "Mathematical Truth," Journal of Philosophy70 (1973): 661-679, whichraises problems for the notionof mathematicaltruth on the basis of a causaltheory of knowledge:see especiallypp. 671-72, whichmotivate this causaltheory of knowledgeby reference to twentieth century space-time physics. 14. H.Minkowski, "Space and Time," Address delivered at the 80thAssembly of GermanNatural Scientists and Physicians,1908, trans.W. Perrettand G. B. Jeffreyin H.A. Lorentz,et. al., ThePrinciple of Relativity,London, 1923, p. 75. 15. Sucha "conjunctive"view of empiricalconfirmation and testing-where logic and mathematicsare treatedsimply as furtherconjuncts-is explicitin Quine, Philosophyof Logic,Englewood Cliffs, 1970, pp. 5-7. 16. I. Kant,Prolegomena to Any FutureMetaphysics, ?30. 17. Reichenbachdeveloped this analysis in his firstbook, Relativitatstheorieund Erkenntnis Apriori, published in 1920. For an English version see H. Reichenbach, The Theory of Relativityand A Priori Knowledge, trans. M. Reichenbach, Berkeley, 1965. For further discussion see my "Geometry, Convention,and the RelativizedA Priori:Reichenbach, Schlick, and Carnap,"in Logic,Language, and the Structureof ScientificTheories, ed. W. Salmon and G. Wolters, Pittsburgh,1994. 18. It is well knownthat Carnap,for his part,was quite enthusiasticabout The Structureof ScientificRevolutions. And, towards the end of his career, Kuhnwas fond of characterizinghis viewpointas "Kantianismwith movablecategories." 19. A fullertreatment of thispoint would need to distinguishpure mathematics, wherewe developtheories of various mathematical structures (e.g., differentiable manifolds),from applied mathematics,where we assert that some such mathematicalstructure provides a modelor representationfor a givenphysical domain(e.g., that space-time events can be modelledor representedby a relativisticdifferentiable manifold). The claim in the text is clear and incontrovertible,I believe, for pure mathematics, but the appliedcase obviously raises numerousadditional questions. (I am indebtedto ElisabethLloyd and StephenLeeds for prompting me to makethis distinction explicit.) 20. Forthis terminology, deployed in a moregeneral philosophical setting, see G. De Pierris,"The ConstitutiveA Priori,"Canadian Journal of Philosophy, SupplementaryVolume 18 (1993):179-214. 21. Quine,"Epistemology Naturalized," p. 84. 22. See A. Einstein,"Autobiographical Notes," in AlbertEinstein: Philosopher- Scientist, ed. P. Schilpp,New York,1959, p. 53.

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23. For Poincare's influenceon Einsteinsee A. Miller,Albert Einstein's Special Theoryof Relativity,Reading, 1981, especially Chapter2, "Einstein'sPhilosophic Viewpointin 1905." 24. The passage fromEinstein cited in note 22 above states that the key insight was to recognize the "arbitrariness"of "theaxiom of the absolute characterof time, viz, of simultaneity"-language which certainly sounds far more like Poincar6than either Hume or Mach.

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