Unification, Evaluation and Development of Theories

Unification,EvaluationandDevelopmentofTheories

AvrilStyrmanUnificationinPhysicsandPhilosophyMay11th2019Helsinki

Contents

1.  Structureoftheories2.  Evaluationanddevelopmentoftheories3.  Theoverallstateofcontemporaryphysics

StructureofTheories

StructureofTheories•  Perceptionyieldsverifiedcommitments(beliefs)inthe

existencee.g.particlesandplanets,andtheirmovement


existencee.g.particlesandplanets,andtheirmovement•  Metaphysicalcommitmentsfunctionasthebasisofexplaining

verifiedcommitments,butarethemselvesunverified




:whatexistsaccordingtoatheory




Everythingpositedbyhypothesisismetaphysical:hypothesesofuniversallaws,unobservables,brutefacts,primitives,axioms,unexplainedexplainers,hypotheticalentitiesandprinciples

:whatexistsaccordingtoatheory

StructureofTheories1.  Observations2.  Regularities3.  Laws

StructureofTheories

EvaluationofTheories

EvaluationofTheories•  Evaluationofcompetingtheoriesisaboutassessingthe

fitnessoftheirpredictionsandexplanationsaboutthesamephenomena,empiricaldata,perceptions,orverifiedcommitments

EvaluationofTheories•  Oftwotheoriesthatpredictandexplainthesame

phenomena,themostvirtuousisthebest



•  Whatarethevirtuesandhowcantheybemeasured?



•  Whatarethevirtuesandhowcantheybemeasured?

–  Evidential:accuracyanddepth–  Unifyingpower:evidentiality/simplicity–  Diachronic:developmentofunifyingpowerovertime

Evidentiality•  Canbemeasuredbycomparingatheorytoempirical

evidence


evidence

•  Accuracyofpredictionsandcausaldepthofexplanations


evidence

•  AccuracyofpredictionsandcausaldepthofexplanationsWhileinthecaseofanexplanation,thefinaleventisknowntohavehappened,anditsdeterminingconditionshavetobesought,thesituationisreversedinthecaseofprediction:here,theinitialconditionsaregiven,andtheir“effect”—whichinthetypicalcase,hasnotyettakenplace—istobedetermined.CarlHempel.AspectsofScientificExplanation,p.234.NewYork:FreePress,1965.


evidence

•  Accuracyofpredictionsandcausaldepthofexplanations

Accuracyofpredictions

Accuracyofpredictions•  Accuracyofpredictionsistheanchoroftheoryevaluation

–  Easytomeasure

–  Mosturgentlyneeded:wheneverthereisadireneed,itismoreimportanttoknowhownaturebehavesthanwhy

–  Othervirtuesaresubjugatedtoaccuracyofpredictions

CausalDepthofExplanations1.  Accuracyorthelevelofdetailinwhichanexplanation

characterizesphenomena2.  Variabilityofcircumstanceswhereanexplanationremains

valid3.  Finaltest:prolificityofaccuratepredictions

HeatherE.Douglas.76(4):444–463,2009.Reintroducingpredictiontoexplanation.PhilosophyofScience.

Evidentialityisnotenough•  Theproblemofunderdetermination:wecannotselect

betweentwoequallyevidentialtheoriesbasedontheirevidentialityonly;therefore,wemustevaluateothervirtuestoo

UnifyingPower•  Unifyingpower,theprincipleofEconomy,parsimony,

Ockham’srazor:ofequallyevidentialtheories,thesimplestisthebest

evidentiality/simplicity

E/M

•  Ametaphysicallysimplertheorycommitstoasmallernumberorquantityofhypotheticallaws,entities,principles,primitives,brutefacts,axioms,unexplainedexplainers

•  Asyntacticallyormathematicallysimplertheoryhasasimplerformulation

UnifyingPower


E/M

ThomasAquinas(1225-1274):“Ifathingcanbedoneadequatelybymeansofone,itissuperfluoustodoitbymeansofseveral.”BasicWritingsofSt.ThomasAquinas,vol.2.,p.129.EditedbyA.C.Pegis.NewYork:RandomHouse,1945.

WilliamofOckham(1287-1347):“Itisvaintodowithmorewhatcanbedonewithfewer.”AsquotedinBertrandRussell,TheHistoryofWesternPhilosophy,p.472.NewYork:SimonandSchuster,1945.

IsaacNewton(1642-1727):“Wearetoadmitnomorecausesofnaturalthingsthansuchasarebothtrueandsufficient.”Principia,3rdedition,bk.3

UnifyingPower


E/M

EinoKaila(1935):“Thesmaller…thenumberofitslogicallyindependentbasicstatements...incomparison…tothenumberofdifferentkindsoffactsthatcanbederivedfromit…thegreateristherelativesimplicityofthetheory.”EinoKaila.HumanKnowledge:AClassicStatementofLogicalEmpiricism.TranslatedbyAnssiKorhonen.EditedbyJuhaManninen,IlkkaNiiniluotoandGeorgeA.Reisch,pp.78-9.Chicago,Illinois:OpenCourt,2014.

UnifyingPower


E/M

PhilipKitcher’s(1981)unificationmodel:scientificexplainingisaboutunifyingdisparatephenomenaoradiversesetoffactsunderasmallnumberofbasicprinciplesorpatterns.Explanatoryunification.PhilosophyofScience,48:507–531,1981.ExplanatoryUnificationandtheCausalStructureoftheWorld.InPhilipKitcherandWesleySalmon(eds.)ScientificExplanation,pp.410-505.Minneapolis:UniversityofMinnesotaPress,1989.

UnifyingPower


E/M

DevelopmentofTheories

DevelopmentofTheoriesDevelopmentofunifyingpower


E/M


Unificatoryvs.disunificatorydevelopment


E/M


Unificatoryvs.disunificatorydevelopmentPositivevs.negativedevelopment

Successvs.regress


E/M


timegoesforward;theamountofdatatobeexplainedgrows


E

timegoesforward;theamountofdatatobeexplainedgrows;evidentialitygrows


E

M



E=M



EM



EM


E/M


E=M


E/M


E

M

E/M



E=E/M

M


UnificatoryDevelopment

E=E/M

M


-Newtonianmechanics-Mendeleyev’speriodictableofelements

DisunificatoryDevelopment

DisunificatoryDevelopment•  Parametrisation:whenatheoryfailstogivecorrect

predictionsofnewdata,itcanbesavedfromfalsificationbyaccommodatingthedatabyauxiliaryparameters



•  Whendataisaccommodatedbytheaidofadditionalmetaphysics,therealityissotospeakbecomplementedbyhypotheticalentitiesinordertosavethetheoryfromfalsification



“no conclusive disproof of a theory can ever be produced; for it is always possible to say that the experimental results are not reliable, or that the discrepancies which are asserted to exist between the experimental results and the theory are only apparent and that they will disappear with the advance of our understanding.” Karl Popper. Conjectures and Refutations: The Growth of Scientific Knowledge, p. 50. London: Butler & Tanner Limited, 1963. 4th edition.


EM


E/M


E=M


E/M


E=M


E/M

-Standardcosmology(FLRW)

Darkenergyisadded


FromNewtontothePresent

FromNewtontothePresent1700-> 1900->

unificatorydevelopment disunificatorydevelopment

E=E/M

M

E=M

E/M

FromNewtontothePresent•  Newtonianmechanicswasmodifiedandcomplementedby

thetheoryofrelativityandquantummechanics–  SR1905,GR1915,GR-basedcosmology1917onward:

parametrisation/problems–  QM1920’sonward:noconsensualontological

interpretation•  Standardmodelofparticlephysics1960’sonward:

parametrisation/problems


normalsciencesufficesnormalscienceisnotenough

E=E/M

M

E=M

E/M

1700-> 1900->


1700->

normalsciencesufficesnormalscienceisnotenough

E=E/M

M

E=M

E/M

“Failure of existing rules is the prelude to a search for new ones.” Thomas Kuhn. The Structure of Scientific Revolutions, p. 68. Chicago: University of Chicago Press, 2nd edition, 1970.

TheChallenge1.  Toinventbettertheories

TheChallenge1.  Toinventbettertheories

2.  Dogmatism:

–  Standardphysicsishighlyparametrisedanddisunified–  Normalscienceisnotenough;newtheoriesareneeded–  Thescientificcommunityeffectivelyrepelsnewtheories,

becausetheycontradictthestandardtheories–  Standardtheoriesaretaughttostudentswithout

criticism,andthetraditiongoeson

TheChallenge'Normal'science,inKuhn'ssense,exists.Itistheactivityofthenon-revolutionary,ormoreprecisely,thenot-too-criticalprofessional:ofthesciencestudentwhoacceptstherulingdogmaoftheday…inmyviewthe'normal'scientist,asKuhndescribeshim,isapersononeoughttobesorryfor...Hehasbeentaughtinadogmaticspirit:heisavictimofindoctrination…IcanonlysaythatIseeaverygreatdangerinitandinthepossibilityofitsbecomingnormal...adangertoscienceand,indeed,toourcivilization.Karl Popper, Normal Science and its Dangers, in I. Lakatos and A. Musgrave (eds.), Criticism and the Growth of Knowledge (1970), pp. 52-3. Cambridge University Press

Summary•  Weneednewtheoriesthataremoreunifiedthanthe

standardtheories•  Wemustobjectivelyevaluatenewsuggestionsagainst

standardtheories•  Toreachtheoptimalprogressrateofscience,wemust

acceptbettertheories,evenwhentheyaredifferentfromstandardtheories

Thankyouforyourattention

Unification, Evaluation and Development of Theories

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