science, certainty, and descartes - g. hatfield

7/29/2019 Science, Certainty, And Descartes - G. Hatfield

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Science, Certainty, and DescartesAuthor(s): Gary Hatfield

Source: PSA: Proceedings of the Biennial Meeting of the Philosophy of Science Association,Vol. 1988, Volume Two: Symposia and Invited Papers (1988), pp. 249-262Published by: The University of Chicago Press on behalf of the Philosophy of Science AssociationStable URL: http://www.jstor.org/stable/192888 .

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Science, Certainty, and Descartes

GaryHatfield

Universityof PennsylvaniaIt is difficult to determine heplaceof experience n Descartes'philosophyandsci-ence. His a priori, rationalistmetaphysicswouldseem, on the face of it, difficultto recon-

cile with theexplicit appealhe makesto sensoryevidence in both his scientificpracticeandmethodologicalremarks.Althoughearlierdescriptionsof Descartes as a pure a prior-ist in natural cience (e.g., Koyre 1978,pp. 89-94) haverightlybeenrejected, t would bea mistaketo embracetheotherextreme,as does Clarke 1982), with his boldrevisionistthesis thatDescarteswas, in actuality,anempiricist.Andyet thepossibilityof combiningthe rationalistandempiricistelementsin Descartes'thoughthas also seemedproblematic,for it has been assumed thatDescartesrequired hatexperientiallybasedknowledgemeetthe standard f absolutecertaintyset by the themethodof doubt n the First Meditation(Garber1978). This difficultynotwithstanding, ny adequate reatment f Descartes'maturephilosophymust accommodateboth his rationalistmetaphysicsand his acknowl-edgmentthat sense experienceplays an essentialrole in naturalphilosophy,as thework ofscholars suchas Buchdahl(1969, chap.3) andWilliams(1978, chap.9) has shown.Attempts o develop a satisfactoryunderstandingf the role of experience n Descartes'philosophyhave been hinderedby two myths.The first of these is theassumption ust men-tioned:thatDescartesappliedthe standard f hyperbolicdoubtfrom theFirst Meditation othe sensoryevidenceusedin naturalphilosophy.Letus call this themythof absolutesensecertainty. t has beenpervasive,andhas led to a deepmisunderstandingf Descartes' con-ceptionof the role of experience n theacquisitionof knowledge,because it has encour-agedtheassimilationof Descartes'positionto thedoctrinesof twentieth-centuryense-dataphilosophers forone of manyinstancesof thistendency,see Rorty1978,chap. 1, sec. 2).The secondmyth,whichmaybe called themythof method,consistsin thebelief thatDescartessubscribed o a singlemethod,announcedn theDiscourse on Methodbutonlyfully articulatedn theposthumouslypublishedRules or theDirectionof theMind,towhich he creditedhis achievements n bothmetaphysicsand naturalphilosophy(Beck1952, chap. 16, 18).These two mythsreinforceone another.Forif it is assumedthatDescartescontinuouslysubscribed o a singlemethod,and thatthis methodrequired hatallknowledgemeet the standard f hyperboliccertainty, henit will seem that he must haveexpectedabsolutecertainty romthe sensoryevidenceused to support onclusionsin natu-ral science.Recently,Garber 1987) has rejectedtheclaim that a unifiedmethod extends fromtheRules to the Meditations,only to replaceit with the claim that a continuousmethodologi-

PSA 1988, Volume2, pp. 249-262Copyright? 1989 by thePhilosophyof Science Association

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250cal doctrineextendsfromthe Rules to theDiscourse andthe scientificpracticeof theOpticsandMeteorology.He supportshis belief that the Rules describethe methodDescartes used in his scientificprogramof the 1630s by providinga carefulanalysisofDescartes' accountof theprimaryandsecondarybows of the rainbow.Accordingto thisanalysis,Descartes couldreasonablyclaim thathis explanationof the rainbowconstituteda successful applicationof his method;only laterdid he realize thatin other cases hisdemandfor absolutecertaintycould not be squaredwith his appealsto sense experience.This realizationcausedhim, in PartFour of thePrinciplesof Philosophy,to admit thefailureof his scientific program Garber1978).1

In the following discussion,I will arguethatearlyin his matureperiodDescartesrec-ognized the need to acceptless than absolutecertainty n the investigationsof theparticu-larsciences, and thatthisrecognitionwas a secondaryconsequenceof his discovery,in1629-30, of general metaphysical oundations or his physics. This discoveryledDescartes to develop what was for him a radicallynew conceptionof natureand of thesciences thatdescribe it. Before 1629, he spokeof varioussciences of nature;his exam-ples came fromthe traditionalAristotelian"mixed"mathematical ciences, fromArchimediansciences such as fluid statics,and from Gilbert'sworkon the magnet.After1629, he thoughtof physics as a single, generalscience of nature,which could provideframeworkprinciplesforparticular ciences such as optics andmeteorology.At the mostgenerallevel, his new physics sharedsome featuresof the traditionalmathematical ci-ences, in thatit posited generallaws orrulesof action,as expressedin Descartes' laws ofmotion.But, perhaps o his surprise, he mode of explanation hat Descartes now foundappropriateo wide rangesof particular henomenawas mechanistic,rather hanmathe-matical-where "mechanistic" ndicatesexplanations ramedby analogywith theexpla-nationof machinesthrough he interactionof theirparts,rather hanexplanationscast inthe form of derivations roma formalmechanics.AlthoughDescartes at firsthopedthathis physics would allow the detailsof suchexplanations o be deduced a priori, he sooncame to realize thatsucha deduction would not be forthcoming.Consequently,his con-ceptionof themethodappropriateo workin theparticular ciences changed.He came torecognize the legitimacyandimportanceof conjecturalhypotheses n particularareasofphysics, andto acknowledgethat,in deciding amongcompeting hypotheses,absolute cer-taintycould not to be expected.

The interpretation f the developmentof Descartes'conceptionsof science andcer-tainty ust sketchedcannotbe fully supportedn the spaceallotted here.Inpreviouswork,I have arguedthatDescartesrecognizedthata diminished standard f certaintywasappropriateo thoseportionsof his physics which could notbe derived a priori from hismetaphysics(see also Clarke1982), and that as a consequencehe abandoned he tradi-tionalconceptionthat scientificknowledgeconsists in necessarydemonstrations(Hatfield 1985). Recently,I have urgedthat n 1629-30 Descartesradicallyreconceivedtherelationsamong physics, mathematics,andmetaphysics(Hatfieldforthcoming;seealso 1986, pp. 65-69). In the presentpaper,I hopeto establisha connection between thebeginningof Descartes' matureproject n naturalphilosophyandhis acceptanceof a low-ered standard f certainty. will contend that after 1629 Descartesabandoned he ideathat a single method was suitablefor metaphysicsand the whole of physics. His attentionto method became divided.In metaphysics,he developedthe "methodof doubt"with itsstandard f absolutecertainty; n physics,reflection on his actualpractice n formulatingmechanistichypothesesresulted n a lowered standard f certainty or such hypotheses.1. Methodin Descartes

As do severalof themythsaboutDescartes,the mythaboutmethod has a basis in hisown words. Indeed,one might say thatDescartes himself initiated themyth,as earlyorearlierthan his debate with Chandoux n 1628 (Descartes1964-74, hereafterAT,vol. I, p.213), and thatin the anonymousDiscourse on theMethodof 1637 he publiclyaffirmed



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251the rumor hat he possessed a specialmethod.Moreover, t can be granted hat theRulesprovidedthe basis for Descartes' sketchof his method in PartTwo of theDiscourse, sothat the formerwork (abandonedn 1628) providesaninterpretivekey for the latter.Thestorythat Descartesonce claimedto have discovereda specialmethod, indeed, the secretmethodof the ancients, is, then,far froma myth.The ascriptionof a special methodtoDescartes achieves mythicproportions,however,when it is madethe primarybasis forunderstandingheMeditations andPrinciples (Beck 1952, 1965;Gueroult1984-5, chap.1), and when it is readlaterally nto the entireMeteorologyor into Part Six of theDiscourse itself (Garber1978).The problem s only compoundedwhen the epistemologi-cal projectof the Discourse and Meditations s read back into the Rules (Schuster1980,1986), therebycreatingan illusion of programmatic ontinuitywhich implicitly supportsthe thesis of methodologicalcontinuity.2

CertainresemblancesamongtheRules, theDiscourse, the Meditations(1641), andthePrinciples (1644) have lentprimafacie plausibilityto the thesis of methodologicalconti-nuity.In all four works Descartesportraysphilosophicalknowledgeas adeductivesys-tem in which all claims to knowledgearisethroughsmall,certainstepsfrom self-evidentbeginnings.Following Schuster(1986, p. 41), we may call this picturethe latticeworkconceptionof knowledge.Descartes remainedfaithfulto thispictureas a demandon firstprinciples.The requirementsplacedon theprinciplesof philosophyin theprefaceto thePrinciples, that"theymust be so clear and so evidentthat the humanmind cannot doubttheir truthwhen it attentivelyconcentrateson them,"and thatthey be such that"theknowledgeof otherthingsmustdependon them"(ATIX, 2; translations,here andbelow,are from Descartes 1984-5), might equallywell have come fromRule Four,or from theend of PartTwo of theDiscourse, or from theDedicatoryLetter to the Meditations.Andthe wordingof Rule Two, that"we shouldattendonly to those objectsof which ourminds seem capableof havingcertainand indubitable ognition,"would have fit seam-lessly into the later works.

Despite theconstancyof Descartes' ideal of philosophicalknowledgefrom the Rulesthrough hePrinciples,his conceptionof therelationbetweencertaintyand deductivestructuren naturalphilosophy changeddramaticallyduring he 1630s. The changewasnot the productof isolated reflections on methodper se; as we shall see in sections2-4, itresulted from a shiftin the typeof explanationhe found himselfproviding or a varietyofnaturalphenomena.But thechangewas reflected n Descartes'discussions of method,forit altered he role he assignedto method n descriptionsof his philosophicalachievements.Whereas n the Rules andin PartTwo of theDiscourse, he claimed to havediscovered aspecialmethod,in PartSix of theDiscourse (ATVI, 63-64), in theMeditations,andin thePrincipleshe made a quitedifferentclaim.There he boastedof havingdiscovered the trueprinciplesof philosophy,principleswhichextend to everything n the createdworld.He nolongercharacterizedhis achievementas thediscoveryof a specialmethod thatappliestoall cognition;rather,he claimed to have achievedfundamental ognitionsthatapplyto allexisting things,andthereby o haveansweredcertainsubstantivequestionsaboutthe natu-ralworldonce and for all. Prominentamongtheprinciplesso establishedwere theequa-tionof matterwithextension andthe three aws of motion.Froma methodologicalperspective, he important onsequenceof thischangewas itseffect on the latticeworkpicture.In theperiodof theRules,Descartesconceivedtypicalexplanationsas involvingappealto mathematicalaws, or to mathematically-expressedrules of action;optics was theparadigm ase (RuleEight).Inexplanations nvolvingsuchrulesor laws (e.g., of reflection andrefraction),once the law had beendetermined,tsapplication equired implythatempiricallydeterminedvalues of variables e.g., theangleof incidence)be pluggedin. Although n PartSix of theDiscourse andthereafter,

Descartesclaimed,in languagesuperficially imilarto thatusedin theRules, to "deduce"his physics fromfirstprinciples,suchdeductionsno longerresembleda mathematicalderivation.Beginningin theearly 1630s, theexplanationsn Descartes'writingson natural



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252philosophy nvolved theconjecturalpositingof microstructures;heprimary xplanatoryworkwas performednotby laws, butby thepositingof configuralmechanisms, ike somany gearsin a clock, or like so manyvalves in a hydraulicmachine.While suchexplana-tionsmay presuppose he lawfulness of material nteractions,heyare not couchedin termsof lawfulrelations.InDescartes' new vision of a unifiedphysicsof the entireuniverse,micro-mechanisticxplanations ame to the fore.The fundamentalmetaphysicalprincipleof this new physicswas theequationof matterwithextension,which,in Descartes'con-ception, impliedthe denial of thevoid, and so thephysicsof a plenum.Thisconception edto a pictureof the universeas a tissue of fluidvorticesirregularly tuddedwithlargechunksof congealedmatter planets),on which varioushydraulicmachineswere located,alongwith variousgroupingsof particleshaving sufficientlysimilarmicrostructureso pro-duceregulareffects and thus to be denominated s varietiesand subvarietiesof elementalkinds.In section2 we shall see thatalthoughDescarteshadhopedto be able to "deduce"the detailsof thisphysicsfromgeneralprinciples n a strictly a priori manner,he came torealize thata strictdeductionwas notpossible.Yet he continued o use the term"deduce"for the relationbetween the firstprinciplesof his physicsandparticularmechanisticexpla-nations,and to do so even in close proximity o thepassagesacknowledging hat a strictdeductionwas notpossible (Discourse,PartSix, ATVI, 64-65). In suchcontexts,his useof the term"deduce"s best understoodhrough heetymologicalsense of the term:hismicro-mechanical xplanationswere "leadout"fromhis metaphysicalprinciples, n thesense thatthoseprinciplesprovideda descriptionof thefundamentaloncepts,or thebuildingblocks,out of which anexplanationwas to be be conjecturally onstructed.

The methodof the Rulesdidnotdisappear ll at once.As mentioned bove,Descartessummarizedt in PartTwoof the Discourse.Thissummary, owever, houldnot be acceptedwithoutquestionas adescription f his actualorpreferredmethod nnatural hilosophyat thetimethe Discoursewascomposed. ndeed, herearegoodgroundsorreading hemethodolog-icalremarksn PartTwo as anautobiographicalccountof Descartes' hinkingduring he timewhen the Ruleswerecomposed.As a characterizationf a methodassociatedwithpractice, heearlymethoddescribes he achievements f Descartes' arlywork nmathematics ndoptics.Inparticular,is accountof reflectionandrefractionntherainbow s of interestpreciselybecause t illustrateshe earliermethod theworkdatesfrom1629;ATI, 23). By themid1630sDescarteshadabandonedurthermathematical ork(ATII,268),andhe hadexpandedhisconceptionof physics n such a waythat hemethodological iscussionsdeveloped ncon-junctionwith hiswork nopticsnolongerdescribedhisprimarymethodological roblems. t istrue hat hephysicsof Descartes'new Worldwrittenrom1629-1633)wasnotwithoutmath-ematically xpressed aws,in the formof laws ofmotion.Further, escartes ontended hat hesubtleaetherof lightwas fineenough oactunhinderedyothermatter, ndthus o exhibitmathematically recisebehavior.Butexplanation y appeal oprecise aws of actionhadbecometheexception,not the rule.As Descartes'dismissalof Galileo's aw of fallmadeclear(seeKoyre1978,pp.92-94),inpracticehepictureof nature escribednThe World oulddis-courage he search or mathematicalaws. Descartesbegan o realizeby themid 1630s thathisearliermethodological onceptionsno longerapplied o hismechanisticxplanations.

AlthoughDescartes'new visionof naturewas firstexpressed n TheWorld,beforebeginning hatwork he haddevelopeda generalmetaphysicalustification or its funda-mentaldoctrines.Theattempt o use metaphysical rgumentationojustify substantiveclaims aboutnature-an attemptmadepublic n the MeditationsandthePrinciples-markeda radicaldeparturerom thephilosophicalprogramof the Rules.Let us see how.2. From Methodto Principles

It is interesting o note thatalthoughhe claimedin the Rules thathis method wouldreveal"everytruth or the knowledgeof which humanreason is adequate" ATX, 395),Descartes did not claim that humanreasonwas adequate orevery truth see ATX, 396).He left open thepossibility that naturecontainspowersor agencies which lie beyond



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253humancomprehension.The fact that he should leave open this possibility-a possibilityhe would laterforeclose-may be understoodby consideringthe aim of the Rules.Thatwork took as its object of investigationthe conditionsfor applicationof the "knowingpower,"rather han the naturesof the thingsto be known.It grantedprimacyto methodover metaphysics.The methodologicalambitionandmetaphysical imidityof theRulesare most evident in the analysisof perfectandimperfectproblems n Rules Twelve andfollowing. Rule Twelve also explicitly disavows the search for a metaphysical guaranteethat the method of theRules will yield insightinto the essence of corporealthings.

The distinctionbetween"perfectlyunderstood"roblemsandthose"imperfectly nder-stood"occurs nearthe end of RuleTwelve.Perfectlyunderstood roblemsare thoseforwhich all of thefollowingare known: 1) the criteria or a solution, 2) thepremises(or"data")or a solution,and(3) the meansby which it is to be provedthatpremisesandsolu-tion "areso mutuallydependent hatthe one cannotalter n any respectwithout herebeingacorresponding lterationn the other" ATX, 429). Imperfectproblemsare definedby con-trastwithperfectones;presumably, heyareproblems or whichone or more of thesecondi-tions have not been met. We learn urther hatperfectproblemspertainonly to thepurestofsimplenatures,and are foundprimarilyn arithmetic ndgeometry. mperfectproblemsper-tainto compoundnatures;heexamplesgiven, includingmagnetismandacoustics,suggestthatsuchproblemsariseprimarilyn naturalphilosophyorphysics(ATX, 431).

Unfortunately, he thirdpartof theRules, which was to have been aboutimperfectproblems,was never written.However,theexisting Rules containindications of whatDescartes hadintended to argue n the unfinishedportion.In Rule Thirteenhe purports oshow how imperfect problemscan be transformed ntoperfectones. In particular,he saysthat the problemof discerningthe natureof themagnetcan be madeperfectby limitingthe given elementsof the problemto "theexperimentswhich Gilbertclaims to have per-formed,be they true or false" (ATX, 431). In the subsequentRule, he furtherobservesabout this problemthat"if the magnetcontainssome kind of entitythe like of which ourintellect has neverbeforeperceived,it is pointlessto hope that we shallever get to knowit simply by reasoning; n orderto do that,we should need to be endowed with some newsense, or with a divine mind. But if we perceivevery distinctlythatcombinationof famil-iarentities or natureswhich producesthe sameeffects which appear n the magnet,thenwe shall creditourselves with havingachieved whatever t is possible for the humanmindto attain n this matter" ATX, 439). These two commentsspeak,in reverseorder, o thefirst two conditions on perfectproblems.Theremark romRuleFourteen ndicateshowto proceedif theproblemof themagnetis imperfectbecause surecriteria or a solutionarelacking, given thatthemagnet may containsomethingunfamiliar o the humanmind;by requiringproposedsolutions to appeal only to knownentities,we can achieve"what-ever it is possible for the humanmind to attain"by way of knowledgeof the magnet.Interestingly, t is not claimed thatby restrictingsolutions to knownentities, we can beassuredof achievingtruthabout the magnet(as opposedto truthaboutthe solutionto theproblem,as restricted).Similarly,the remarks romRuleThirteensuggest thatif theproblemis imperfectbecause we areunsurewhetherall of the datahave been observed,we mayrestrictthe datafor theproblemto thatgiven in a particular ource.Theseremarks n theproblemof themagnetreveal thatDescarteswas quitewillingtotradescopeforpowerin theRules;he was willingto limit thescopeof theknowledgeattained,n order o be assured hatwhathe didattainpossessedcertainty. f we look aheadto thecorrespondencerom 1637and1638,andto theend of thePrinciples, t wouldseemthatthe"imperfection"f theproblemof themagnetshould n partbe ascribed o the diffi-cultyin inferringa truecausefromknowneffects,especiallysince Descartesdemandedofperfectproblems hatdataandsolutionbe tiedas necessaryand sufficientconditions.But the

Rules show no concernwiththisdifficulty; itherDescartesbelievedtherewas no problemin inferring ruecausesfromeffects when he wrote thatwork,orhe was satisfiedmerely"tosave thephenomena."Moreover, he factthathe was willing to turn mperfectproblems nto



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254perfectones by limiting nvestigationo theproffered"data,"whether heybe trueorfalse,reveals a limitation o thescopeof theclaimthat n followingtheRules,the humanmindwill attaina knowledgeof everythingt can know.For now it can be seen thatamongthethingsknownwill be certainconditionalruths, uchas:if these are all the relevantdataforthemagnet, hen the natureof magnetisms such and such.Under hiscondition heproblembecomes"perfect," ut at theexpenseof assurancehata solutionwill yield the truthaboutthe natureof themagnet.

The problemof limited datamay seem a merely practicalone, to be overcomebymakingthe requisiteobservations.Whether t is merely practicaldepends uponwhatmaybe expectedfrom sensoryobservation.TheRules do not suggest thatsensorydata isinherentlydefective; indeed,some sensoryexperienceis includedwithinthedomain ofintuitiveknowledge (ATX, 383, 423), and so is grantedcertaintyequivalentto thatofmathematics.But suchcertaintypertainsonly to experientialknowledgeof thingsthat are"entirelysimple and absolute" ATX, 394). The"simpleand absolute" ncludesthemathematicaldimensionsof things(size, shape,number;ATX, 419, 439), wherethethingshavingsuch dimensions are as variedas stars, sounds,weight, andspeed (ATX,378, 447-448). But, in anycase, no reason is given forexpectingthatall naturalphenom-ena will presentdatasufficientlyclearto renderperfecttheproblemof assigninga causefor thephenomena.Where such data s wanting,Descartes'message is clear: the truthabout the cause of thephenomena ies beyondthe scope of humanknowledge.

It may seem, however,thatthere s no need to despairabouteither thepossibilityofknowingwhatis required or a solution,or thepossibilityof discovering sufficientlycleardata. For it may seem that elsewherein the Rules Descartes has providedreasonto hopethat thereis nothingmoreto be met within nature hancompoundsof commonandfamiliarsimple natures;and if it could be known that each observedthingis a compoundof perfectlyknowablenatures, hat wouldprovidereason to hope that all phenomenacould be renderedclear andintelligible.Suchhopes would seem to receive encourage-mentin Rule Twelve, in which Descartes asserts that thesimplenatures ound in bodiesinclude"size, extension,motion,etc." (ATX, 419). This pronouncementwould appear obe thefamiliarCartesiandoctrine that theessence of matter s extension. On the assump-tion that it is, the Rules makea quitepowerfulclaim;for if it is granted hat bodies pos-sess geometricalpropertiesonly, it follows that the solutionsto all imperfectproblemsregardingcompoundbodies can be restricted o suchproperties.Any given datacould betruthfullyexplainedthroughsome combinationof perfectly intelligible simplenatures.It is at thispointthatthemetaphysical imidityof the Rules comes intoplay.Nowhere nthatworkdoes Descartesclaim thatthe essenceof matter s extension.Althoughhe recom-mends thatwe treatcolors, sounds,etc. as if theycouldbe equatedwithgeometrical igures,and contends hat f we do so, we will be ableclearlyto understandheireffects uponthesenseorgans,he doesn'tclaim,andso doesn'targue, hatthequalitiesof bodies areactuallyconstitutedby purely geometricalproperties ATX, 412-414). Indeed, urtheron in RuleTwelvehe explicitlyeschews suchontologicalconclusions,explaining hathe is concernedwiththings"onlyas theyareperceivedby theintellect,"and not with "howtheyexist inreality" ATX, 418; see also ATX, 399). The"simplenatures" iscerned n the Rules areepistemicallysimple;there s no guaranteehatthey correspondo somethingonticallysim-ple. Indeed, t is notclear thatDescarteswas committed o the centralmetaphysical enetsof his maturephysicswhen he wrote theRules.InRuleFourteen, orinstance,he treatsweightas somethingreal,that s, as something"havinga real basisin bodies"(ATX, 448).Althoughthisdescription ontradictshis laterdenial thatweightis a realproperty f bodies,it accordswithhis treatment f weightin a documentsurviving rom theearly partof theperiodduringwhichthe Rules werecomposed,thephysico-mathematical ritingsunder-

taken n connectionwith Beeckman ATX, 69-74). Because thedenialthatweightis arealproperty f bodies is a paradigmaticnstanceof Descartes'doctrine hatthe essenceof mat-ter is extension,it wouldseem thatthe latterdoctrinepostdates he Rules.



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255The Rules describe therequisitesforknowledge,withoutimplyingthat the worldisentirelyknowable.PerhapsDescartes believed priorto 1629 thatthe world containsnoth-ing unknowable,buthad no argument or his belief, or none that he was willing todivulge. Orperhapshe hadno such belief.Be that as it may, in the springof 1630 Descartes announced hat he haddiscoveredthe foundationsof physics duringtheprevious year (ATI, 144). I have contendedelse-where that this discovery included the fundamentalargumentsof the Meditations(Hatfield,forthcoming).I will not rehearse hatstoryhere. But it is worthnotingthatbythe early 1630s, Descartes was prepared o stateexplicitly thedoctrinethat was missingfrom the Rules-that matter s to be equatedwith extension. But he would state it only asa hypothesis.Thus, in TheWorld,he assigned only thepropertiesof size, shape,andmotionto the matterof his new, hypothetical, maginaryworld (chap.6). At the outsetofthe Fifth Partof the Discourse he alluded to this hypothesis,and he presented t againinthe First Discourse of the Meteorology.As Descartes remarked n TheWorld,accordingto this hypothesismattercontains"nothing hatyou do not know so perfectlythatyou

could not even pretendto be ignorantof it"(ATXI, 35). Incorrespondencedatingfrom1638 (February22, to Vatier)he claimed he could provethis hypothesisin his meta-physics (ATI, 563), and he attempted o do so in theMeditationsandPrinciples.It has beenmaintained, n reasonablegrounds, hattheargumentspresented n theMeditationsandredescribedn thePrinciples-both thoseattemptingo provethattheessence of matter s extension,as well as others-are generic nstancesof theregressivemethoddescribed n the Rules(Beck 1952,chap.18; 1965,chap.13). Indeed,Descarteshimselfcharacterized he methodof theMeditationsn thismanner thoughwithout,ofcourse,explicitreference o theRules;ATVII, 3; compareATVII, 156 andX, 376). Thereis, then,some methodologicalcontinuitybetween the laterworks andthe Rules. Toacknowledge hiscontinuity s not,however,to equatethemethodof theMeditationswiththatof theearlierperiod.There aresignificantdifferencesbetween the two. Thehyperbolicdoubtof theMeditationswas new;it was notexplicitin Discourse,and it was opposedtotheteachingof the Rules (according o whichtheintuitivelyevidentshould be acceptedstraightaway;RuleThree).Correspondingly,hecertainty hatwas methodologicallyrequiredprior o theMeditationswas nothyperbolical,butordinary ertainty;t follows thatthecertaintyaccorded o sense experienceprior o theMeditationsalso was ordinary er-tainty.And so even though t is truethata descendantof theearlymethodappears n theMeditations,and thattheMeditationsprovide hefoundations orthephysics,it shouldnotbe assumedthattheearlymethodtherefore xtends to thephysicsso grounded. nfact, it isin connectionwith thenew physicsthatthegreatestmethodologicaldiscontinuityoccurs.

3. Deductive Structureand a priori PhysicsIn orderfor the thesis of methodologicalcontinuityto be true,it must be the case thatDescartes understood he explanationsof naturalphenomena n his maturephysics to bestrictdeductionsfrom basic principles-deductions thatmeet the standardsof the lattice-workmodel in theRules, a model in which each link in a chainof reasoningis connectedto the succeeding one as its necessaryandsufficientcondition.In the presentsection Ishall arguethat as Descartesbeganto constructhis World,he actuallydid envision thepossibilityof a thoroughly a priori science, one which would allow a suitablytight apriori deductionof the structure f variouskinds of earthlybody.Two lettersto Mersenne n 1632, whichreportprogresson TheWorld,revealDescartes' vision of a completely a priori science. In the first,written n April,Descartesdescribed an additionto his originalproject:In the treatisewhich I now have in hand,after the generaldescriptionof the stars,the heavensandtheearth,I did notoriginallyintend to give anaccountof particu-



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256larbodies on the earth butonly to treatof their variousqualities.In fact, I am nowdiscussing in addition some of theirsubstantial orms,andtryingto show the wayto discover themall in time by a combinationof experimentandreasoning.This iswhat has occupiedme these last days;forI have been makingvariousexperimentsto discoverthe essential differences betweenoils, ardentspirits,common andstrongwaters,salts etc. (Descartes1970, p. 22)

In fact, the additionhere describedhas come down to us not as partof TheWorld,butaspartof theMeteorology.In anyevent, the brief allusion to experimentand reasonin thisletteris not by itself methodologicallydistinctive. One monthlater,however,Descarteswrote that he hopedto discover a means of knowingthe forms andessences of earthlybodies in an a priori manner:For the last two or threemonthsI have beenrapt n theheavens.I have discoveredtheir natureand the natureof the starswe see thereandmanyotherthingswhich afew years ago I would not even have dared o hope;and havenow become so rashas to seek thecauseof thepositionof each fixed star.Foralthough heyseem veryirregularly istributedn variousplacesin theheavens,I do not doubt thatthere s anaturalorderamongthem which is regularand determinate.Thediscoveryof thisorder s thekey and foundationof thehighestand mostperfectscience of materialthingswhich men can ever attain.Forif we possessedit we coulddiscover a prioriall the different orms and essences of terrestrial odies,whereaswithout t we haveto contentourselveswithguessingthem a posteriorifrom theireffects. (10 May;1970,pp. 23-24)

In this puzzling passageDescartes held out the hopeof an a priori physics, one thatwould enablehim to discovereven the microstructures f the varioustypes of terrestrialbodies. What could he have hadin mind?Considerthe accountof thedevelopmentof the universegiven in TheWorldandlaterin thePrinciples;in each work,the world as we see it now arisesfroma hypotheticalbeginningin a chaos of matter n motion.A completely a priori science, as Descartesenvisionedit, would begin with a generaldescriptionof this chaos and would show howourpresentworldcould arise. Withoutrelyingon anyobservationsof thepresentworld,this science would succeed in "deducing" he featuresof thatworld,includingthe partic-ular "forms"and "essences"of its minerals.Perhaps hepassage just quoted expressedDescartes' belief that an understanding f theprinciplesof star ocation could provideinsightinto vorticalformation,andthat this insightwould be sufficient to allow a com-pletely a priori deductionof theparticular pecies of matterwhich, by hypothesis,werechurnedout by the vortexandwhich thencongealedto formthe earth(a deductionof thesort found in a more limited form in the Principles).While such speculationshave themakingsof an interesting able, sadly,as Descarteswent on to admit n the letter ust quoted,therewas little hopethat theprinciplesof starplacementcould be discovered.This pessimistic presentiment eems to have beenborneout, for in thePrinciples he confidedthatthe vortices exhibit an "inexplicablevariety"(1983, PartIII,art.68). In that work he provideswhat is presumablyan a priori accountof the formationof the mattersurroundingheearth;he explainsthe chief qualitiesofsuchmatter,which were vorticalmotion,weight, light, andheat(IV, 15-31). But as theaccount descends to the explanationof moreparticularqualitiesof matter, t becomes lessclear whether t should to be construedas a priori ora posteriori. (See, forexample, theaccountof the formationof air andwater;IV,32-48.) Descartes refersbackto the"partic-ularhypotheses" ntroduced n theFirst Discourse of the Meteorology(to be distin-

guishedfrom the moregeneral hypothesisof thecorpuscular onstitutionof matter) norderto supporthis conclusionsregarding he microstructures f variousminerals,includingthose structures hatexplainthe difference betweenwaterand salt water(IV,



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25748). In attempting o explainthe propertiesof variousmineralsandmetals, he is forcedtoappealto experience(IV, 16), to rely on the hypothesesof theMeteorology,or to curtailhis presentation or want of experiments(IV, 63). Thus,he fails to advancebeyondtheposition he had envisioned in April, 1632;he can do no betterthanto guess causes fromeffects, a posteriori. His initial suspicionthatit would be necessaryto employ the methodof hypothesisin describinghis new world,a suspicionthatarose not long after he turnedhis attention o the explanationof terrestrialparticularities,was provensound.4. A posteriori Physics, Experience,andCertainty

As numerous ommentators ave observed(Buchdahl1969,chap.3; Clarke1982;Garber1978;Laudan1966),Descarteshimselfexplained hat t was theexplanatory ertilityof his own firstprincipleswhich drovehimto the methodof hypothesis.Theproperties fsalts, oils, ardent pirits,commonandstrongwaters,and so forthcouldbe explained nmany ways;Descartes'problemwas to see whichamongthepotentialexplanationsweretrue.Onoccasion,he characterized achof thevarietyof potentialexplanationsas a "deduc-tion"from his firstprinciples e.g., ATVI, 65). As alreadynoted,the notion of a deductionexpressed n such remarkswas notverystrict; t was less strict hanthatfound in theRules,andbore little resemblance o formaldeduction see also Buchdahl1969;Clarke1982).Descartes'claim to haveprovidedmultiple"deductions"f thephenomena romhisprinci-ples maybe read as the claim thatstartingromsize, shape,andmotion,togetherwiththelaws of motion and theassumption f aninitialchaos,a varietyof micro-mechanisms, nyone of whichwould be adequate o explaintheknownphenomena, anreasonablybe imag-ined to arise. Given thisimaginedvariety, heproblembecomes thatof discovering estsbaseduponsenseexperience hatcould serve to determinewhich of themicro-mechanismsis actual.Althoughhypotheticalpositstested n this mannermightin some cases be estab-lishedwith a highdegreeof confidence, n the lettersof 1637-38 andin the finalremarks othePrinciplesDescartesrefrained romgranting hemcertainty omparablemerelyto themathematical ariety-let alonehyperbolic ertainty Hatfield1985).My claim thatDescartes refusedto grantmathematicalormetaphysicalcertaintytothe postulationof micro-mechanismsmust be distinguished romthe claim that hebelieved all sense-basedknowledgeof theexternalworldlacks certainty.Contemporaryappreciationsof the Cartesian piritnotwithstanding,Descarteswas willing to grantordi-narycertainty-again, as opposedto the hyperbolicalvariety-to claims aboutmaterialobjects thatgo beyondthe "immediatelygiven"in sensory experience.This willingnessis foreshadowed n theFirstMeditation.Descartes offers an initialscepticalchallengetothe senses based on theiroccasionaldeceptiveness,only to rebut this challengeby sug-gesting that undergood conditions the senses areperfectlyreliable.The dreamargumentand the hypothesisof anevil deceiveraresuccessively strongerskepticalresponsestothis rebuttal; t seems fairto assume,therefore, hatonce these groundsfor doubthavebeen removed, the senses may be treatedas reliablesources of knowledgeof thingswhich areclose at hand,which can be touched as well as seen, etc. And indeed, the sens-es arevindicated n the Sixth Meditation(ATVII, 80; see Hatfield 1986), in which it issuggested thateven factualdetailsaboutthematerialworld, such as the size of the sun,can be knownby means of the senses (in conjunction,of course, withreasoning),as canthe propertiesof objects which arerelevantto the preservationof one's bodily well-being(ATVII, 80-1). Further,n PartsOne andFour of thePrinciples (I, 69-70; IV,200),Descartesaffirmsthatsize, shape,andmotioncan be "clearlyperceived" n bodies bymeans of the senses (in conjunctionwith the understanding).

Descarteswas prepared o allow that,when sufficientcare is taken,sensoryobserva-tion can yield certainty.But the possibilityof suchcertaintydoes little to solve theprob-lem of how to achieve certainknowledgeaboutthosemicro-mechanisms hatmust,asremarked n 1632, be "guessed"fromtheireffects, a posteriori. The taskof attainingcer-taintyabouthypotheticalposits could be completedonly by meansof extensive experi-



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258mentation, f at all;Descartes was aware of the underdeterminationf micro-mechanicalhypothesesby sensoryevidence. Of course,he thoughthe had a head start owardsolvingthe problemof underdeterminationn framinghis conjecturalhypotheses,for he believedthathe hadestablished,once and for all, whatthe theoreticalvocabularyof any physicalhypothesismustbe: theoreticalposits must be couchedin the languageof size, shape,andmotion. But the fact that he claimed to be metaphysicallycertainthat his generalapproach o physics was correctdoes not alterthefact that he granted, rom near theinceptionof his fully mechanisticconceptionof naturalphenomena, hat he was not enti-tled to claim such certaintyabout theparticularmechanismshe posited.

The use of mechanistichypothesesbecame centralto Descartes' naturalphilosophyintheearly thirties.Its absencefromtheprimary xamplesof methodin the Rules helps toexplainhow Descartescould thereenvision the attainment f certaintywithrespecttoparticularproblemsin physics.Let us putto one side the certainty hatarisesfrom thetransformation f imperfectproblems nto perfectones, for suchcertainty s purchasedatthepriceof forfeiting knowledgethat the solutionsof theproblemsaretrue. There remainotherexamples fromtheRules, or from theperiodof its composition,which offer thepossibilityof certainty or natural cientific conclusionsthatrely on experience.Thedeterminationof the anaclasticas envisionedin RuleEightis a case in point.To it may beaddedtheexplanationof the angle atwhich the rainbow s seen. As DescartesobservedinRule Eight, in the Optics(Second Discourse),andin theMeteorology (EighthDiscourse),experiencemustplay a role in each case.

Despitethisfact,Descartesclaimedin such cases to have achievedthe sortof "deduc-tive"certainty equiredby theRules.Thenotionof "deduction"n these cases is regressive(Buchdahl1969,chap.3, sec. 2d;Garber1987);it requiresworkingback to theexplanatorybasisfrom which thegiven problemcan be progressivelyderived.Descartescould claimthatcertainty s achievable n the instancescited becausethe relevantexperientiallybasedclaimsprovideevidencenot forpostulatingmicro-mechanisms, utfordetermininga math-ematical aw governingobservablerelationsamongphenomena.Andalthough he law pre-sumablycannotsimplybe "readoff' fromexperience,experiential lements can and mustplayanintrinsicrole in theprocessof deduction.Experiencecanplaya role, becauseDescartesallows thatsensoryexperiencecancountas an instanceof "intuition"f theobjectsof theexperiencearepureandsimplenatures ATX, 383, 394), as the dimensionsof thingslistedin Rule Fourteenpresumably re(ATX, 447-8). The angular elationsbetweenthepathsof a light raybeforeand afterrefractionmightalso count as an instanceof an intuiteddimension(withinthe limits of accuratemeasurement;ee the table of mea-surementsn theEighthDiscourseof theMeteorology). n this lastexample,experiencemustplaya role in boththeregressiveandprogressivephasesof the"deduction,"or therefractive ndices of variousmedia such as waterand air canonly be determined hroughexperience,as Descarteshimselfmadeclear(ATVI, 102, 337). (Thispointaboutrefractiveindicesdoes not contradictDescartes'claim to havederived hesine law of refractionon apriori grounds,on which see Smith1987.)

If it is correct hatthe Rulespermitsensecertainty nly in thecase of thesensory ntu-itionof medium-sizedobjects, t becomesapparenthatonce Descartesaccordedprimacy ohis vision of a universeof littlemachines, his routeto certaintywould becomeless centralto his philosophyof science. Oncethischange n emphasishadoccurred,most cases of rea-soningin Cartesian hysicsceased to be like the case of determininghepositionof therain-bow;typicalproblemsno longer nvolvedthe useof directmeasuremento determinea lawor relation.Because themajorityof explanationsnvolvedanappeal o micro-mechanisms,themode of inferencedependedon analogical easoning rom theknownto theunknown,from observablemechanisms o positedmicrostructuresGalison1984).Admittedly,n hisdiscussionof thepositionof therainbow,Descartesdidreason rom thebig to thelittle,inas-muchas he usedglass globes to modelraindrops.Butin thiscase, the"analogy"nvolvedmerely shrinkinghe scaleof a model whichexhibiteda "macro" ersionof thephenomenon



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259in question.By contrast,wheninferringhiddenmechanisms,one is freeto posit anyof agreatvarietyof mechanismsas a meansof explaininga phenomenon;hemethodologicalconstraints njoyedwheninvestigatingheoperationof a singlemathematicalaw in largerand smallerspheresareno longerpresent.Thepossible positedmechanismsarevirtuallyendless,under he limitation hatanymechanismpositedbe trulymechanical, hat s, thatsuchmechanismsbe ascribedonly theproperties f size, shape,and motion(ATI, 420;PrinciplesIV, 200, 201). Given thesecircumstances,ven if a particular ositedmechanismsaves all of thephenomena,one mayassert hat t is the truemechanismwithmerely"moral" ertainty;hatdegreeof certaintymaysuffice for the rational ixationof belief,butit falls shortof the notoriousabsolutecertainty f Cartesianmetaphysics.5. Science, Hypothesis,and Descartes

Descartesrecognizedthe need to proceed by the method of hypothesisfrom near theinceptionof the mechanisticprogramdescribed n theWorld, heMeteorology,andthePrinciples.As Laudan 1966) and Buchdahl 1969) have observed,he adopteda "hypo-thetical-deductive"mode of supportinghis claims aboutparticularmechanisms.Thedescriptionof Descartes' strategyas "hypothetical-deductive"annot be left unqualified,for Descartes did not leave the domain of allowablehypothesesunrestrictedseeBuchdahl,pp. 144-7);it was restrictedby metaphysicallydeterminedprinciples, ncludingtheequationof matterwithextension,and the laws of motion.Assumingthisqualification,it maybe recognizedas a pointin the historyof methodologythatDescartesexplicitlydescribed the limitationson certainty hatresult from a hypotheticalmode of reasoning.

Despite thepresenceof themethodof hypothesis n Descartes' maturescience, it wouldbe misleadingto portrayCartesian cience as directlycontinuouswithpost-Newtonian ci-ence. Indeed,themethodof hypothesiswhichDescartesapplied o mechanismscontrastsboth with the methodhe usedin explaining herainbow'sposition-and so with themethodof theRules-and with thetypeof scientificexplanation nspiredby Newton'sPrincipiaandOptics.From a methodologicalpointof view, the centralexamplesof Newtonianexpla-nation,such as the derivationof ellipticalorbitsfromtheinverse-squareaw, seemcloser toexplanationscontained n the Rules thanto those foundin Descartes'maturework.Thedifferencen spiritbetween hematureDescartes'primarymodel of scientificexplana-tionandthatof Newtonmaybebroughtntoreliefbybrieflyconsidering naspectofDescartes'mature cientificprogramhathas been cited as a common eature f Cartesian ndNewtonian cience: he"mathematization"r"geometrization"f nature. ntheattemptounderstand escartes'claimthathis science was"geometrical"r"mathematical,"wo inter-pretationsmightnaturallyome tomind.The claimmightbetaken o refereither o theallegeddeductive tructure f his science,or to its use of mathematicalaws,such as the sine law ofrefraction r the laws of impact.However,whenDescarteswrote n thePrinciples hat he"onlyprinciples" f hisphysicsarethoseof "geometry ndpuremathematics"II, 64), he hadyeta thirdpoint n mind:hewas simplyexpressing hedoctrine hat he essence of matter s"pure xtension."Forthisdoctrineamounts o the view thatmatters whollydescribablentermsof thegeometrical roperties f size, shape,position,andmotion.Inasmuch s sizeorvolumemaybemeasured,hesepropertiesmaybedescribedas"quantitative";uttheascrip-tion of suchpropertieso matterdoes notleadnecessarilyo a "quantitative"pproachonature f thesortthatwe are ikelyto associatewithNewton,orwithGalileo'sdiscoveryofthe law of fall. Itdoes notlead nevitably o a notionof nature s governedbyquantitativelaws,orto thenotion hatscientificreasonings principallyoncernedwithmathematicalderivation.As we haveseen,in Descartes'maturenatural hilosophy he ultimate mphasiswas on mechanisms,notlaws;"mathematization"mountedo "mechanization"see alsoHatfield,n press).Of course,a mechanisticaccountof nature uch as Descartes' s unthinkable nless it issupposed hatmattern motionmoves withlawfulregularity, ndDescartesdidinvokethe



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260required egularityn his three awsof motionandseven rulesof impact.These laws arecastin quantitativeerms-as relationsbetween he fundamentalmagnitudes, quantity f matter"andspeed.But thepossibilityof suchquantitativeawsis not establishedby thedoctrineofextension,even if thisdoctrines taken o include he ideathatmotion s a geometrical kine-matic)property nd hence s a "mathematical"roperty; kinematicpurelydescriptive)treatment f motiondoes not entailthat hepatterns f motion n theworldaredescribablebysimple aws. As is well known,Descarteswent outside he notionof matterasextensionandintroducedGod as a "dynamic"lement o fix these laws-the lawsareunderstood s a mani-festationof God'simmutability,pecifically,of his conservation f the samequantity fmotion n thematerialworldas atthe creation see Hatfield1979 forfurther iscussion).

The introductionof universal aws of motiongoverningthe interactionof all particlesin the universewas, indeed,a stepof some significancein the marchof the worldspirittowardNewtonian science: it provideda prominentexampleof theconceptionof natureas a single, law-governedsystem,to replacetheconceptionof a universe bifurcated ntotwo regions governed by differentprinciples;methodologically, t encouragedreplace-mentof theconceptionof physics as a series of particular ciences of naturewith the pic-tureof one basic science of physics, possessing various branches.But these validpointsof comparisonbetween Descartes'programandthedevelopmentof post-Newtoniansci-ence should not lead us to be misled by otherseeminglyvalidcomparisons.In particular,we should not be led to believe thatthe laws of motionplayedthe sameexplanatoryrolein each instance.A mistake on thispointwould explain why the role of hypothesisinDescartes' maturescience was atone timeroutinelyoverlooked. To aninterpretermbuedwith a post-Newtonianconceptionof science, the characterandthe extentof the role thatDescartes accordedto hypothesisin his physics would seem insignificant n comparisonto the thingsDescartesclaimed could be knownindependentlyof experience, throughmetaphysics.Inparticular,Descartes' claim to know his laws of motion a priori wouldseem of especial importance; or to a readerwith post-Newtoniansensibilities,it wouldseem that once the laws governingmotion(includingthe law of gravitation,which has nocounterpartn Cartesianphysics) had beenestablished,theexplanatorybasisof physicswas largely complete.For if Newton's laws could be known a priori, it would seem ofsmall consequencethat,say, themasses of individualbodies could not be. But inDescartes' mechanisticaccountof naturalphenomena, he chief explanatorywork is per-formedby the configurationof theparticles n varioustypes of body.There are no casesin which the laws governingmotionserve to explainan important lass of phenomena,such as the planetaryorbits; moreover,given his explanatoryambition,thepostulationofmicro-mechanisms-which mightseem to a Newtonian ike so manyspeculationsabout"initialconditions,"which shouldbe avoidedif the conditions cannot be determinedthroughmeasurement-becomes the centralactivityof Cartesian cience. Thepostulationof suchconfigurationsproceeds by a methodof hypothesis,baseduponanalogy.HenceDescartes' mathematical onceptionof matter, ar frompermittinghim to adopta geo-metricalstyle of proofin naturalphilosophy,and far fromleadinghim to retain a mathe-matical or metaphysicalstandard f certainty, ed him to acknowledgethatabsolute cer-tainty may be beyondreachthroughoutmuch of the science of nature,because that sci-ence mustproceed conjecturally,by means of hypothesis.

Notes1Garber ontinuesto hold the view that therewas a fundamentalandpersistent en-sion between Descartes' demandforcertaintyand his appealto experiencein science,and thatthe methodologicalpointsmadeat the end of thePrinciples constitutedan

admissionof defeat for his program,as is evident from his "DescartesandExperiment nthe Discourse andEssays,"presentedat San Jose StateUniversity duringApril, 1988 (p.10 of the distributeddraft).



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2612Schuster(1986) chastises othersfor seekingto find methodologicalcontinuity nDescartes' work;yet he is guilty himselfof adoptingtheposition that a single "problemof justification"-the problemof justifying the applicabilityof mathematics omatter-may be foundin boththe Rules and the Meditations,being met in the firstby the"optics-psychology-physiologynexus"(1980, pp. 59-73), the failureof which led to themetaphysicalargumentsof the second (1980, pp. 75-79).

ReferencesBeck, J. (1952). TheMethodof Descartes. Oxford:ClarendonPress._ _ _ _ . (1965). The Metaphysics of Descartes. Oxford: Clarendon Press.Buchdahl,G. (1969). Metaphysicsand thePhilosophy of Science. TheClassical Origins:

Descartes to Kant.Cambridge:MITPress.Clarke,D. (1982). Descartes' Philosophy of Science. Manchester:ManchesterUniversityPress.Descartes,R. (1964-74). Ouevresde Descartes. Editedby C. Adamand P.Tannery.Newedition. Paris:Vrin._ _ _ _ __ _. (1965). Discourse on Method,Optics,Geometry,andMeteorology.Translatedby P.Olscamp.Indianapolis:Bobbs-Merrill.__ _ _ __ _. (1970). PhilosophicalLetters.Translatedby AnthonyKenny.Oxford:ClarendonPress.__ ____ _._ 1983). Principles of Philosophy.Translatedby V.Miller and R. Miller.Dordrecht:Reidel.__ __- __ _. (1984-5). Philosophical Writings. Translated by J. Cottingham, R.Stoothoff,andD. Murdoch.Cambridge:CambridgeUniversityPress.Galison,P. (1984). "Descartes'sComparisons."sis 75: 311- 326.Garber,D. (1978). "Science andCertainty n Descartes."InDescartes: CriticalandInterpretiveEssays. Editedby M. Hooker.Baltimore:JohnsHopkins UniversityPress, pp. 114-151._ _ _ _ __. (1987). "Descarteset la Methode en 1637." InLe Discours et sa Methode.Editedby N. Grimaldiand J. Marion.Paris:PressesUniversitairesde France,pp. 65-87.Gueroult,M. (1984-5). Descartes' PhilosophyInterpretedAccordingto the OrderofReasons. Translatedby R. Ariew. 2 vols. Minneapolis:Universityof MinnesotaPress.Hatfield,G. (1979). "Force(God) in Descartes' Physics."Studies in HistoryandPhilosophyof Science. 10: 113-140.__ __ _ ?_. 1985). "FirstPhilosophyandNaturalPhilosophyin Descartes." InPhilosophy,Its HistoryandHistoriography.Editedby A. J. Holland.Dordrecht:Reidel, pp. 149-164.



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262_ _ _ _ __. (1986). "The Senses andthe Fleshless Eye: TheMeditationsas CognitiveExercises."InArticles on Descartes' Meditations.Editedby Amelie Rorty.Berkeley:Universityof CaliforniaPress,pp. 45-79._ _ _ _ _ _ (in press). "Metaphysicsand the New Science."InReappraisalsof theScientificRevolution.Editedby D. LindbergandR. Westman.Cambridge:CambridgeUniversityPress._______. (forthcoming)."Reason,Nature,andGod in Descartes."Science in Context.Koyre,A. (1978). Galileo Studies. Translatedby J. Mepham.New Jersey:HumanitiesPress.Laudan,L. (1966)."TheClockMetaphor ndProbabilism." nnalsof Science.22: 73-104.Schuster,J. (1980). "Descartes,MathesisUniversalis, 1619-28."InDescartes:

Philosophy,MathematicsandPhysics. Editedby S. Gaukroger.New Jersey:Barnes andNoble, pp. 41-96.__ __ __ . (1986). "CartesianMethod as MythicSpeech:A DiachronicandStructuralAnalysis."In The Politics andRhetoricof ScientificMethod.Editedby J.SchusterandR. Yeo. Dordrecht:Reidel, pp. 33-95.Smith,A. (1987). "Descartes'sTheoryof LightandRefraction:A Discourse on Method."Transactionsof theAmericanPhilosophicalSociety.Vol. 77, Part 3.Williams,B. (1978). Descartes: TheProject of PureInquiry.New York:Penguin.

science, certainty, and descartes - g. hatfield

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