Plato's theory of Knowledge

1. PLATO’S
THEORY OF
KNOWLEDGE

2. ● Plato(427—347 BC)livedinAthens.
● Hewasthesonofawell-to-docitizenandhehadnoneedto
workinorder tolivecomfortably; buthebelievedthatitwas
aman'sdutytocontributetothewelfareofhisfellow
citizens.
● HefoundedtheAcademyatAthens,whichwastoprovidea
liberaleducationfor youngmenwhowouldbefutureleaders
inthecitystate.

3. PLATO:KNOWLEDGE
● Platotook themainpurposeof philosophyto be to encourageright
conduct,andthiswastobeachievedby convincingpeople thatthey
shouldbegood,andalsobyshowing themthewaytobegood.
● Hedidnotregardknowledge as separatefrom ethics, for, like
Socrates, heheldthat everyone wantedtobegood andthatanyfailure
invirtue must, fundamentally, be dueto ignorance.
● Thetrulywise wouldunderstand thattheir bestinterest wasserved by
actingvirtuously.
3

4. PLATO:KNOWLEDGE
● 'Virtue'did nothavethesamemeaningforPlatoasit doesfor
us.TheGreekwordarete,which wetranslateasVirtue‘had
differentconnotations.
● Ourconceptofvirtueisbased,toaverylargeextent,onideas
which comefromourChristianheritage:fromtheBible,from
RomanCatholicandfromProtestantinterpretations.
● Theirvariousviewsofvirtuehaveinfluencedus,whetheror
notwebeChristianbelievers.
4

5. PLATO:KNOWLEDGE
● FortheGreeks, aretecouldnotstandonits ownas
'virtue'canforus.
● Forthem, tobevirtuousortobegoodwastobevirtuous
inrespectofsomething ortobegoodatsomething.
● Soonewouldtalkofagoverning arête(goodat
governing),orofamilitary arete(goodatmilitary
affairs).
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6. PLATO:KNOWLEDGE
● Platospeaksoftheareteofdogsandhorses,thatis,theirabilityto
performtheirspecialfunction(ergon)asdogsorhorses.
● Plato(andSocrates)reasonedthattheremustalsobeahuman
arete,shownbyamanwhowasgoodatbeing aman,i.e.at
performingspecificallyhumanfunctions,andthatwashowthe
wordwasconnectedwithvirtueinoursenseoftheword'virtue'.
● Thevirtuousmanwasgoodatconductinghislifeasahumanbeing.
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7. PLATO:KNOWLEDGE
● PlatoandSocratesthoughtthatvirtuedepended on
knowledge.
■ Onehadeither toknowhowtobegoodatbeinga
man,oratleast tohaveatruebeliefastohowto
begood.
● Platowouldonlybestowtheaccolade ofknowledgeon
whatwasindubitablyandnecessarily true.
7

8. PLATO:KNOWLEDGE
● Whatwastruebutmighthavebeenotherwise,
i.e.whatwasacontingentratherthana
necessarytruth,couldonlybe anobject of
opinionand,atbest,itwasheldasatruebelief,
neverasknowledge.
● But,asapracticalguidetoconduct,truebelief
wasasgoodasknowledge. 8

9. PLATO:KNOWLEDGE
● Platoimpliesthatknowledgeis
possible,thoughtruebeliefwillalso
guidetovirtue
9

10. GradesofApprehension:KnowledgeandOpinion
● Platoarguedthatsinceknowledgehadtobeindubitablethe
objectsofknowledgehadtobepermanentandunchanging.
■ For example: '2+ 2=4'istrue, hasalwaysbeen true and
alwayswillbetrue. LikewiseTheanglesofa(Euclidean)
triangle sumto180°'and'All unicornshaveonehorn.‘
■ These propositions areexamples ofnecessary truths, they
cannotbeotherwise; hencesuchtruths canbeobjects of
knowledge.
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11. GradesofApprehension:KnowledgeandOpinion
● Moreovertheknowledgeoftheirtruthisnotarrivedat
byobservationbutbythought.
● Thustheobjectsofknowledge hadtobenecessary
truthsandtheyhadtobeapprehendedbythemind,
notbythesenses.
● Theywere knownbydirectmentalintuitionorby
ratiocination.
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12. GradesofApprehension:KnowledgeandOpinion
● Bycontrasttheobjectswhich weperceivedwithour senses,
weretheyshadows, rainbows,horses,mountainsor people,did
nothavepermanentpropertiesorpermanentexistence.
● Henceanyproposition abouttheirpropertiescouldnot be
indubitablefor,evenif truetheywerenotnecessarilytrue,
theymight havebeenfalse.Wecouldonlyclaimto have
opinionsaboutthemand,atbest,theseopinionswould bebut
truebeliefs.
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13. GradesofApprehension:KnowledgeandOpinion
● Platodistinguishedtwomaingradesofapprehension,
according tothenatureoftheobjectsapprehendedand the
mode ofapprehension.Thesewere:
○ Opinion —theobjectsofopinion wereobjectswhich could
beapprehendedbysenseperception;
○ Knowledge—theobjectsofknowledgewereobjects
accessibleonlytothemind.
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14. GradesofApprehension:KnowledgeandOpinion
● Platoinvitesustoconceiveoftwotypesofthings —
thosethatareperceivedandthosethatcanbe
thoughtabout(butnotperceivedbyanyofthe
senses).
● Hesuggeststhatwecancomparetheclarityof
apprehensionofthesetwotypes ofthingswith
lines:thelongertheline,thegreatertheclarity. 14

15. GradesofApprehension:KnowledgeandOpinion
● ThusifwetakealineAEanddivideitatC,sothatACisless
thanCE,thenthelengthACrepresentstheclarityof
apprehensionofthingsperceivedandthelengthCEthe
clarityofapprehensionofthingsthoughtabout.Thesetwo
linesACandCEcanbeeachdividedagaininthesameratio:
ACisdividedatBsothatABislessthanBC;andCEisdivided
atDsothatCDislessthemDE.SinceAB/BC=CD/DE=AC/CE
thenBC=CD.
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16. 16

17. FORMS
● Wemaynotethattheclarityofapprehensionofobjects
perceived (measuredbyBC)isequaltotheclarity of
apprehensionofmathematical ideas (measuredby
CD).Thusthehighergradeofbelief isasclear asthe
lowergradeofunderstanding.
● Butthehighergradeofunderstanding,understanding
oftheFormsorIdeasismostclear.
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18. FORMS
● TheFormsorIdeasarelikemathematicalentitiesin notbeing
accessibletosenseperception:it isasdifficulttofind a
perfectlyjustact,goodmanorbeautifulstatueinthe
experiencedworldasitistofindaperfectlystraightlineor
pairofparallellines.
● Inadditiontobeauty,justiceandgoodness, Platorecognized
Formsforthehorse,themountain etc.Roughlyspeakingthere
isaForm orIdeacorresponding toeverykindofthingthereis.
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19. FORMS
● Forms orIdeasmust notbetakentobeconceptsor ideas in
thesensethatwe usetheword 'idea'today.Thelatter are
dependentonourmindsandare produced byour mental
activity.
● The Forms are supposedtoexistquite independentlyof us
andourthoughts.ForPlatotheywere thepermanent
objective reality towhich,ifweappliedour mental powers,
ourconceptsmightcorrespond. 19

20. FORMS
● Theterm'Idea‘ismisleading,andeventhe
term'Form'ismisleadingsinceitimplies
thatnon-materialentitieshaveaphysical
shape.
● Abetterword,whichwillbeused
henceforward,is'Universal'.
20

21. TheNatureofUniversals
● ForPlatoUniversalswereimmaterialand
completely independententitieswhichexistedin
animmaterialworld ofUniversals.
● Thisworld,andtheUniversalswhichmadeit,were
theultimateandobjectivereality.Platoissaidto
takearealistviewofthenatureofUniversals.
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22. TheNatureofUniversals
● Platoheldthatwhateverrealitywasascribedto
theworldwhichweareawareofthroughsense
perception,thatistheworld ofentitieswhichwe
see,hear,touchetc.,wasduetothefactthatthe
objectsofsenseperceptionshared,thoughtoa
limitedandimperfectextent, inthenatureofthe
Universals. 22

23. TheNatureofUniversals
● Theparticularswhichweperceived:particularactsof justice,
particularbeautifulthings,existedasjustactsandbeautifulthings
invirtueoftheirparticipationinthe Universalsjusticeandbeauty.
● Likewiseparticularmountainsandhorsesexistedasmountainsand
horsesinvirtueoftheirresemblancetotheUniversalmountainand
horse.
● Thoughitwasnotpossibletohaveknowledgeofanyparticular
whichwasobserved,wecouldaspiretoknowledgeoftheUniversal.
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24. TheNatureofUniversals
● Forexample, wecouldnothaveknowledge ofanyparticularhorse
becauseofitsever-changingattributes, butwecouldaspiretoknowledge
ofthe Universal horse becauseitwould havethepermanentand
unchangingattributes whichareessential to thenatureof all horses.
● Thoughwecouldatbestonlyaspireto truebelief astothenatureofany
particularjustact,wecouldaspiretoknowledge of theUniversal justice
becauseitwould havethepermanentattributes whichconstitute the
essential natureof justice.
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25. TheNatureofUniversals
● Ifwecanfindtheessenceofholiness(notjustan
accidentalattribute)wecanapprehendthe
Universal,andsoacquireknowledge ofholiness.
● ItwillberememberedthattheSocraticdialogue
didnotguideus totheessentialnatureof
holiness.
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26. TheNatureofUniversals
● Apartfromthedifficultyofdiscovering essential
nature,Plato'saccountoftherelationbetween
particularsandUniversals,i.e.thenatureofthe
participationand/orthebasisoftheresemblance,
isvagueandindeedhewasawarethathis
explanationswereunsatisfactory.
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27. TheNatureofUniversals
● SotheUniversalmanstandsforallmenjustasthe Universal
Dog standsforalldogs— theyarecataloguesorlists.There
areofcoursesubsidiarylists,correspondingtosubsidiary
Universals.
● Buttheproblemwhich puzzledAristotle(andPlato)isby-
passed,forwhatdeterminedtheplacingofanyparticularin
anylist?WehavetoknowtheUniversalbeforewecanmake
thelistorcompletethecatalogue.
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28. TheNatureofUniversals
● thePlatonicviewof Universals,theviewthattheyhaveanindependentexistence
andthat,becausetheyarepermanentandunchanging,theyareproperobjectsof
knowledge.
● PlatoknewthathecouldnotdemonstratetheexistenceofUniversalsbyrational
deductiveargumentandthathisaccounthadtobeacceptedonthebasisofan
intuitivebeliefthatultimaterealitywasimmaterialandnotaccessibletosense
perception.ButweshouldnotdismissthePlatonicconceptionof Universalsandof
knowledge.Foranyaccountthatwegiveastothenatureoftheworldmust
ultimatelyrestonintuitivebeliefswhichcannotberationallyjustified.
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29. AllegoryoftheCaveandKnowledge
● Intheallegoryofthecave,Platowaswellawarethatour
primitiveandunreflectinginstinctivebeliefisthattheexternal
worldwhich weknow throughsense perceptionistherealworld.
● Throughmetaphorhehopedtoconvinceothersthatthisbelief
wasmistaken.Letuslookfirstathisaccountoftheconflict
betweentheGodsandtheGiants.TheGiantsholdtheprimitive
instinctivebelief,theGodshaveadifferentbelief,acquiredby
reflection.
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30. AllegoryoftheCaveandKnowledge
● TheGiantsarethosewhobelieve thatsenseperception
gives knowledgeofwhatis,i.e.knowledgeofexistence.
For'theydefine bodyandexistence asthesamething'
and'thataloneexistswhichcanbehandledand
touched'.
● BycontrasttheGodsholdthattrueexistence, true
reality, isinthe'incorporealFormswhichareobjectsof
themind'. 30

31. AllegoryoftheCaveandKnowledge
● Butnowwecometothefamousmetaphorofthecave.
This tells usmuchmorethantheshortaccountofGods
andGiantsforitshowsusnotonlywhyPlatoheldthat
senseperceptioncouldnotbeabasisforknowledgebut
italso showshowwecouldaspiretoknowledge,andit
alsoshowsthatPlatofully appreciatedthatthosewho
aspiretounderstandmayberidiculed.
31

32. AllegoryoftheCaveandKnowledge
● IfwerelyonSENSEPERCEPTION,weremainliketheprisonersin
thecaveandareAWAREONLYOFSHADOWS;weTAKETHESETO
BEREALITY.Butif weuseourUNDERSTANDINGANDASPIRETOTHE
LIGHT(i.e.trytobecomeenlightened)thentheFETTERSOF
SENSEPERCEPTIONMAYBEBROKEN.
● Atfirstweshallfeelpuzzledandafraid,butonce wehave
becomeusedtothelightweshallappreciatethatwehave
knowledgewhich wasnot availableinthecave.
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33. AllegoryoftheCaveandKnowledge
● ifwegobacktothecavewemayfindourselvesridiculed
andperhapsindanger,for,havingbeenenlightened, it
will bedifficult forustoseethingsasweusedtoseeand
inthewaythatthoseinthecavestill seethem.
● Weaspiretoknowledgeandweacquireknowledgeby
usingourUNDERSTANDING, NOTbymeansofperception
withoursenses —sight,hearing,touch,tasteandsmell.
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34. ● ButPlatohastosay,moreexplicitlythanbymetaphor, howitisthatwehaveeventhe
beginningofthenotionofUniversals.
○ Hisexplanationwasthat,bythought,wewereableto
REMEMBERthatworldofUniversalswhich thesoulinhabited
beforeitsearthlylifebegan.
○ ItwasSocrateswhoexpoundedthisviewofthe souland
Platodevelopedhisideas.ForPlato'sdoctrineofUniversals
dependsonacknowledgingthatthesoulisimmortal, or,at
theveryleast,existedbeforeitcametothematerialworld.
THESOUL
34

35. THESOUL
● Platoheldthattheimmaterialsoulwas
independentofandalsosuperiortothe
materialbody.Thisviewofbodyandsoulas
twoindependentanddifferentsubstances
isa formofdualism.
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36. THESOUL
● Platosaidthatthe soulbelongedtothechangelessandexternalworldof
Universals, not tothechanging,impermanentandshadowy world of
sense perception. After death itmightgobacktotheworld of Universals,
though itmightreturn from thencetothismaterialworldagain.But each
timeitreturnedwithinabodyitwasasthoughithad beenoncemore
imprisoned.
● Itlongedforrelease inorderto returnto theworldofUniversals. Yet,
whilstinamaterialbody itbecamepolluted, sometimes very much
polluted, andfor thisreason itwould atleast partiallyforget theworldof
Universals. 36

37. THESOULREMEMBERS
● Senseperceptionmightserveto REMIND itofthat
world,butitcouldonlybegintoapprehend
Universalsbecauseithadonceknownthem
fully.
● 'FornowIseeasinaglassdarkly,butthenface
toface.'
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38. THESOULREMEMBERS
● Butifthesoulhasnotbeentoomuchpolluted
itwillreturntotheworldofUniversals.Here
itwillagainhaveknowledge.
● But,whenitreturnstothematerialworldit
mustdrinkatleastalittleofthewaterof
forgetfulness.
38

39. Recollection
● Whywastheresuchemphasisonrecollectionandwhy wasknowledgepossibleonlyif
therewasrecollection?
○ Platohadto suggestsome basisorgrounds forknowledge and,since
heeschewed sense perception, the sourceofknowledgemustbethe
mind.Itmightthenbeasked whyitwasthat the mind(orsoul) didnot
arriveatknowledge by interpreting thedataofsense.
○ Platodidgrantthattruebelief (whichwasbasedonsense perception)
mightPROMPTthe soul, butitwasPROMPTED TOREMEMBRANCE.
39

40. Recollection
● Hecouldobserve werenever perfect embodiments of Universals. He
alsoasserted thatfromsense perceptionof imperfectentities we
wouldnever beabletoapprehend perfection. Therefore merelyby
perceivingimperfectparticularthings, wecouldnotpossibly
comprehend thecorresponding Universals —thebest thatperception
coulddowas to REMINDusofthe Universals.
○ Forexample, notwolinesareof exactlyequallength, andnotwo
objects areof exactly equalweight etc.andyetwedo havean
understandingofequality —oftheUniversal, Equality.
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41. Recollection
● Sincewecannotpossiblyhavegotthisapprehensionby
directobservationwemusthave remembered it.
● Wemusthavebeenremindedbythenearlybutnot
quiteequalthingswhichweobserveinthematerial
world,oftheabsoluteequalitywhichweknewinthe
worldofUniversals.
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42. Recollection
● There was noobject inthematerial world whichwas completely and
absolutely beautiful,butobservation of objectswhichshowed beauty
insomedegree wouldremindthesoulof Beauty, theUniversal, whichit
hadknownintheimmaterialworld ofUniversals.
● Platowasundecidedonthestatus ofsuchentities asdirtorhair.
Originallyhehadproposed aworld ofUniversals whichexcluded these
butitseems thathefinallyconcludedthatall ourgeneral notions,
whether elevated orsordid, mustbederived fromUniversals inthe
real,immaterialworldofUniversals.
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43. WemaysummarizePlato'sviewofknowledgeasfollows:
1. Knowledgeispermanentandcertain,i.e.itisnot subjectto
correction.
2. Itisnotpossibletoclaimknowledgeonthebasisofsense
perceptionandthereforeitisnotpossibleto claimknowledgeof
anyobjectoreventinthematerial world.Thebestwecan
aspiretoistruebelief(rightopinion).
3. Truebeliefcanguideusandcanprompt thesoultoremember
theworldofUniversals.
43

44. 4. Universalsareeternalandchangelessand
thereforetheycanbeobjects ofknowledge.
5. Universalscannotbeperceivedby thesenses;it
isonlytheintellectwhichmakesusawareof
them.
6. Thuswecanknowonlybyvirtueofourintellect,
andbyitscapacityforrecollection
44

45. Conclusions:
● Thisviewofthenatureofthesoul,animmaterial
intellectualentityfromtheimmaterialworldof
UniversalspermeatesPlato'swriting.
● Thephilosophermustcultivatehissoul;hemust
strivetorecollectandtocomeoutofthecaveinto
thesunlight.
45

46. Conclusions:
● Whenhehasapprehendedreality hemustreturntothe
caveinordertopersuadeotherstosee.Hemaywell be
ridiculed andperhapsmaybepersecuted butitishisduty
tohelp otherstothelight.
● Fromknowledgetherewillbe goodnessandthisisthe
endforwhichthephilosopher,and,intheidealPlatonic
statethephilosopherking,shouldstrive.
46

47. Conclusions:
● Butthere isanotherpersonal aspirationforeach
philosopher.Thestudyofphilosophyeducates thesoul
ofthephilosopherandpreparesitforthetruelifewhich
couldfollowdeath.
● Afterreleasefromtheprisonofthebody,thesoulcould
staypermanentlyintheworldofUniversals andnever
morebepollutedbyamaterialbody.
47

48. Conclusions:
● 'Theloversoflearningunderstand', saidhe,'thatphilosophy
foundtheirsoulsimplyimprisoned inthebody andweldedto
it,andcompelledtosurveythroughthisasifthroughprison
barsthethingsthatare,notbyitselfthrough itself,but
wallowinginallignorance;andshesawthatthedangerof
thisprisoncamethrough desire,sothattheprisonerhimself
wouldbeachiefhelperinhisown imprisonment.
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49. Conclusions:
● Sothesoulofthetruephilosopherbelievesthatit mustnot
opposethisdeliverance,andthereforeabstainsfrom
pleasuresanddesiresandgriefsandfearsasmuch as
possible,countingthatwhenamanfeelsgreatpleasureor
fearorpainordesire,hesuffersnotonlytheevilthatone
mightthink (forexample,beingillorsquanderingmoney
throughhis desires),butthegreatestandworstofallevils,
which hesuffersandnevercounts.
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50. Conclusions:
● ...itisforthesereasons...that
thosewhorightly lovelearning
aredecentandbrave.
50

51. Conclusion:
● Suchwouldbethe reasons ofthephilosopher. His soul would notthink
itrightthatphilosophyshould set herfree, andthatwhilebeingset
free sheherself should surrenderherself backagaininbondageto
pleasureandpains...shethinks shemust calmthese passions; and,
following reasonandkeepingalwaysinit,beholding thetrue andthe
divineandthecertain,andnourishingherself onthis, hissoul believes
thatsheoughttolive thus,aslongasshe doeslive, andwhenshe dies
shewill joinwhatisakinand likeherself, andberidofhumanevils.‘
(Phaedo,Rouse, pp. 560—1)
51

52. ● Wecannowappreciatemorefullyhowknowledge andvirtue
weresointimatelyconnectedin Plato'sphilosophy.Withtrue
knowledge,apprehensionofUniversals,thefutilityandalsothe
snaresoftheworldofsenseperceptionis realizedandthe
virtuoussoulwillavoidthepleasures(andpains)ofthesenses.
Wemayregardthisasaratherarid,perhapspuritanicalviewof
thenatureofvirtueanditisarguablethatthepleatodisregard
thematerialworldcanrathertooeasilybeheldtoencourage
disregardofthematerialwantsofothersaswellasourown
wants.Plato'sviewofvirtueisindeed opentocriticism. 52

53. ● Therehavealsobeencriticisms ofPlato'scontention
thatknowledge comesfromrecollection andthat
onlyUniversalscanbeobjectsofknowledge.
● Therehasbeencriticism ofPlato'sview that
Universals aremorerealthantheparticularswhich
wesense. OneofthecriticswasPlato'spupil
Aristotle.
53

54. ● Todaythere wouldbecriticisms arising fromourview
thattherecanbenoknowledgewithoutamindandno
mindwithoutabrain. Sothatthere canbeknowledge
withoutatleastpartofacorporeal body.How,therefore,
couldanimmaterial entity acquireknowledge, a
knowledge whichcouldbelaterrecollected inamaterial
brain?Even ifthepossibility oftheexistence ofan
immaterial soulis admitted,Plato'saccountof
knowledge byrecollection seems far-fetched tous. 54

55. ● YetitremainstruethatPlatodidbringoutproblems of
knowledge,andtheproblemoftherelationship between
sense perceptionandreasoning,whicharestillwithus
today.
● WemaynotagreewithPlato'sconclusions, butweshould
studythemsympathetically, for,unless wemakeareal
efforttounderstandandtoappreciatehisthoughtswe
areinnopositiontocriticise, stillless toundermine, his
position. 55

56. 56