Plato's theatetus

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Examine and assess Platos arguments in the Theaetetus against the claim the

knowledge is sense-perception, concentrating either on the indirect argument (151-83

or the direct argument (18!-8" #

$n the Theaetetus %ocrates is concerned with the &uestion 'what is knowledge )a*ing

dismissed the possi+ilit that the &uestion could +e answered + example on the grounds

that a genuine answer should designate the man .orms o. knowledge + one

de.inition/ 1, %ocrates is o..ered a more unitar explanation + the oung Theaetetus0

The wa it looks to me at the moment is that knowledge is nothing +ut sense

perception#/ 2ow there is nothing particularl radical in mentioning knowledge and

sensor perception in the same +reath0 as .ar as sources o. knowledge go, the senses seem

to +e one o. the most o+*ious and plausi+le candidates# )owe*er, the manner in which

Theaetetus expresses his position is somewhat no*el# 2ote that Theaetetus does not

suggest that knowledge relies on perception or that knowledge claims must +e *eri.ied +

perception# ather Theaetetus claims that knowledge is 'nothing +ut sense perception#

This is a more radical claim and on the .ace o. it looks something like a claim o. identit 0

knowledge 4 sense perception#

2ow gi*en that identit is a s mmetrical relation it .ollows .rom this de.inition that we

cannot ha*e knowledge which is not perceptual and cannot ha*e perceptions which are

not knowledge, i#e# which are erroneous# 2ow some philosophers ha*e argued that to

interpret Theaetetus as holding this position is incorrect due to the .act that earlier in the

dialogue Theaetetus o..ers examples o. knowledge which are clearl not perceptual in

nature#3 )owe*er, $ +elie*e in light o. what .ollows within the dialogue, i#e# Platos swi.t

mo*e .rom Theaetetus de.inition to the topic o. Protagorean relati*ism, it makes sense to

take the claim that knowledge is 'nothing +ut sense perception to +e a claim that

knowledge and perception are identical# r at least it makes sense to take it that %ocrates

understands Theaetetus claim in this wa #

1 Plato, Theaetetus, 1!8d6-", 7ohn c9owell (trans# , (1:"3, x.ord; x.ord ee, The Secret Doctrine in Platos Theaetetus , ??5, x.ord %cholarship online#

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$n the Theaetetus %ocrates o..ers two arguments against the position that knowledge is

sense perception0 one direct and one indirect# This essa will .ocus on the indirect

argument# %ocrates constructs this argument + .irst relating the thesis o. Theaetetus to

)eracleitus .lux doctrine, *ia Protagorean relati*ism, +e.ore pro*iding an argument

against the )eracleitean position in an attempt to re.ute indirectl the thesis that

knowledge is sense perception# Thus, in terms o. anal sis, we ha*e two &uestions to ask

o. the indirect argument, namel 0 'does Plato success.ull demonstrate the relationship

+etween the doctrines o. Theaetetus, Protagoras and )eracleitus and 'does Plato

succeed in re.uting )eracleitus .lux doctrine

This paper there.ore, will .ocus on these two points# The .irst hal. o. the paper willexplore the relationship +etween Theaetetus position and those o. Protagoras and

)eracleitus, while also considering how our conception o. said relationship ma +e

a..ected + taking re*isionist or unitarian readings o. the dialogue# $ will argue that +oth

the positions o. Protagoras and )eracleitus are necessar .or the de.ence o. Theaetetus

position and there.ore, that this section o. Platos argument is *alid# $n the second hal. o.

the paper $ will consider %ocrates re.utation o. )eracleitus, consider criticisms and

comparisons with @ittgensteins discussion o. pri*ate language, and ultimatel deem the

criticism cogent and the o*erall argument e..ecti*e#

@hen Theaetetus .irst suggests that knowledge is nothing +ut sense perception %ocrates,

rather than attempt to anal se Theaetetus claim in and o. itsel., immediatel makes an

association with Protagoras so called measure doctrine0 Ait looks as though what

ou*e said a+out knowledge is no ordinar theor +ut one that Protagoras, too, used to

stateABecause he sa s, ou remem+er, that a man is the measure o. all things; o. those

which are, that the are, and o. those which are not, that the are not#/ ! %ocrates

elucidates this position + stating that what Protagoras means is that e*er thing is, .or

me, the wa it appears to me, and is .or ou, the wa it appears to ou#/ 5 Thus what is

the case, or what is true, +ecomes relati*e to a gi*en person# This means that in a

! Plato, Theaetetus, 151e:-15 a1-!, 7ohn c9owell (trans# , (1:"3, x.ord; x.ord


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situation where ou and $ +oth ha*e contradictor appearances, leading us to make

contradictor claims such as 'this wind is cold and 'this wind is not cold, no actual

contradiction takes place as our claim is true .or ou and our appearances and m

claim is true .or me and m appearances#

2ow as we ha*e alread indicated, this relati*e approach to truth seems to +e necessar i.

we take %ocrates as understanding the claim 'knowledge is sense perception as a claim

which tries to esta+lish a relation o. identit +etween knowledge and perception# $. all

perception is to +e deemed knowledge then we must make allowance .or the .act that m

perceptions and our perceptions can contradict one another, and the onl wa to achie*e

this is to a+andon the o+Cecti*it o. our knowledge claims and em+race Protagorean

relati*ism# 2ow while a+andoning the o+Cecti*it o. knowledge seems a radical step,that such a mo*e is re&uired in order to de.end the thesis that knowledge is the same as

sense perception is less o+Cectiona+le# $n terms o. cogenc o. reasoning there.ore, it

seems like this .irst mo*e o. Platos is a sound one# Di*en Theaetetus de.inition as a

starting point, and assuming that we do not o+Cect to %ocrates assumption that

appearance and perception are interchangea+le, it is sa.e to conclude that it .ollows that

perception is alwa s o. what is, and .ree .rom .alsehood, as i. its knowledge#/ 6

Platos next step howe*er, is considera+l less predicta+le# Plato claims that there is

another doctrine which has an intimate relationship with Protagoras measure doctrine#

%ocrates sa s The .act is that, as a result o. mo*ement, change, and mixture with one

another, all the things which we sa are which is not the right wa to speak o. them

are coming to +e#/ " $t is claimed + %ocrates that this doctrine o. .lux, which he

attri+utes to )eracleitus and his .ollowers, is also secretl held + Protagoras# 2ow it is

generall understood that this claim is not to +e taken literall , Plato isnt actuall

attri+uting the .lux doctrine to the historical Protagoras# 8 )owe*er, there is clearl a

reason .or the doctrines introduction into the dialogue and this reason is not &uite as

o+*ious as the earlier introduction o. Protagoras measure doctrine#

6 $+id, 15 c5-6#" $+id, 15 d6-15 e1#8 les Burn eat, The Theaetetus of Plato , (1::?, $ndianapolis; )ackett Pu+lishing #

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This particular point is a use.ul one .or highlighting how wide the di*ergence can +e

within Plato scholarship with regard to how certain passages, and as a conse&uence entire

dialogues, are to +e understood# For instance, Gorn.ord accounts .or the introduction o.

)eracleitus + claiming that PlatoHs intention is to accept .rom )eracleitus the doctrine

that all sensi+le o+Cects are perpetuall changingIa .undamental principle o. his own

philosoph #/ : This approach ma seem somewhat unusual gi*en that later in the

dialogue, Plato will attempt to re.ute 'knowledge is sense perception + arguing that on

this )eracleitean picture one cannot secure a re.erent .or knowledge claims# But .or

Gorn.ord, who takes what is re.erred to as a 'unitarian 1? reading o. Platos dialogues, this

is unpro+lematic as Platos o*erall strateg is to show that true knowledge is not o. the

perpetuall changing sensi+le world +ut o. the unchanging world o. the '.orms#

2ow this de+ate, which on the other side in*ol*es more re*isionist readings that take

dialogues such as Theaetetus to a+andon or re*ise doctrines .rom earlier works, is

complex and clearl goes .ar +e ond the scope o. the current essa # Jet, in spite o. this

we must still decide upon a strateg .or making sense o. the introduction o. )eracleitus

.lux doctrine into the Theaetetus# Gan we simpl accept Gorn.ords suggestion $s Plato

simpl introducing +elie.s that he himsel. holds $ +elie*e that in taking the Theaetetus

in and o. itsel., this claim cannot +e Custi.ied# Plato does not gi*e us an indication that

+ehind all o. the critical passages o. the Theaetetus there lies a positi*e epistemological

doctrine and as such, to a*oid undertaking a maCor digression at this point we must seek

to account .or the presence o. the )eracleitean doctrine on the +asis o. what Plato does

sa in the Theaetetus#

K starting point in this regard is to note the somewhat a+rupt manner in which Plato

introduces )eracleitus into the dialogue# %ocrates does not ponder or tease out some

speci.ic &uestion to which )eracleitus doctrine is o..ered as an answer# ather, much

like the earlier introduction o. Protagoras, )eracleitus is dropped in as i. his doctrine is

somehow entailed + , or a conse&uence o. Protagoras measure doctrine# 2ow we ha*e: Francis c9onald Gorn.ord, Platos Theaetetus , (1:5", $ndianapolis; Bo++s- errill Gompan , pp# 36#1? Ghappell, Timoth , LPlato on =nowledge in the Theaetetus L,The Stanford Encyclopedia of Philosophy(Winter 2012 Edition) , Edward 2# Malta (ed# , < > 4Nhttp;OOplato#stan.ord#eduOarchi*esOwin ?1 OentriesOplato-theaetetusO #

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alread ruled out the idea that Plato is simpl taking this opportunit to work in some o.

his own philosoph , so we must take seriousl the idea that the thesis that all the things

which we sa areAare coming to +e,/ 11 is somehow necessar i. we are to make sense o.

Protagorean relati*ism#

ne wa o. making sense o. this mo*e is to consider the metaph sical implications o. the

Protagorean doctrine# $n order to ensure that all perception constitutes knowledge we

ha*e relati*ised truth to each indi*idual, making it impossi+le .or the claims o. two or

more indi*iduals to +e in contradiction with one another# ecall the case o. the wind

which was cold .or me and not cold .or ou0 our claims in this case are not contradictor

+ecause $ am speaking o. how the wind appears to me and ou are speaking o. how the

wind appears to ou# From a logical point o. *iew this case is entirel unpro+lematic asthe claims which initiall look contradictor , actuall turn out to +e a+out di..erent

things0 our respecti*e perceptions#

2ow there are two metaph sical explanations .or how such relati*ism could hold true0

either there is a common o+Cect, e#g# the wind, to which we are +oth uni&uel related and

our Cudgements re.er to this relation# r, there is no common o+Cect at all, there is simpl

the wind .or me and the wind .or ou and +oth are distinct# 1 The most important point

here is that either wa the idea o. a shared world which is 'out there to +e experienced,

spoken o. etc# is o.. the ta+le as e*en i. there is a common o+Cect, our Cudgements do not

re.er to it +ut rather to the wa in which it is related to our sel*es# The same pro+lem

seems to arise when we consider the person who is ha*ing the perception, the percei*er#

Protagoras position, when spelled out in Platos terms, limits our knowledge to

appearances and perceptions making the &uestion o. who is ha*ing these appearances and

perceptions &uite m sterious# There is thus a per.ectl good moti*e .or attempting to

reconstrue the situation, and to remo*e the apparent re.erence to the percei*er and the

percei*ed o+Cect .rom the content o. a Cudgement o. perception#/ 13

11 Plato, Theaetetus, 15 d6-15 e1, 7ohn c9owell (trans# , (1:"3, x.ord; x.ord


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%o to recap0 i. knowledge is perception, then our perceptions must +e in.alli+le# $n order

.or this to hold good, truth must me made relati*e to each person i. contradictions which

arise .rom di..ering perceptions are to +e a*oided# But in order .or truth to +e relati*ised

we must make it impossi+le .or our Cudgements and m Cudgements to +e a+outOre.er to

the same thing0 we must make our Cudgements re.er to the thing as it appears to ou and

m Cudgements re.er to the thing as it appears to me# ur Cudgements there.ore, cannot

+e a+out the world as such +ut must +e a+out our appearances or perceptions# 2ow what

are perceptions @ell the are not o+Cects, the are not sta+le o*er time, the are in .act

.leeting e*ents which are constantl changing# $s this what Plato means when he sa s

the uni*erse is change and nothing else/ 1! 9oes he mean that realit is Cust perception

The theor which Plato spells out seems to +e considera+l more complex than this0 hedescri+es su+Cect and o+Cect as particular t pes o. motion which come together to

produce perceptions, which presuma+l are the re.erents o. all o. our Cudgements# This

means that not onl can no two people talk a+out the same thing, and there.ore disagree,

+ut also that $ cannot disagree with m sel. at two di..erent times as this metaph sics

entails that there is no identit in either su+Cect, o+Cect or propert across time# 2ow we

can see wh this doctrine o. )eracleitus has +een introduced + Plato0 while the measure

doctrine ma make sense when we simpl consider Cudgements that ou and $ ma make,

as soon as we consider what could possi+l +e the su+CectOre.erence o. these Cudgements

we are led to a metaph sics which must a*oid all constanc in order to two or more

Cudgements to +e a+out the same thing and preser*e the in.alli+ilit o. all perceptions#

The .inal step in Platos indirect argument attempts to re.ute this )eracleitean

metaph sics on the grounds that i. it were true, it would +e impossi+le to .ix the re.erence

o. words and thus use our language in an meaning.ul wa # To +egin with, in 181d

%ocrates identi.ies two t pes o. change0 change in spatial location and alteration across

time# )e concludes with Theodorus that in order .or the .lux doctrine to +e *alid

e*er thing must +e perpetuall changing in +oth respects# This makes sense i. we recall

that in order to retain our relati*istic conception o. truth there must +e no sta+le .acts o*er

1! Plato, Theaetetus, 156a5-6, 7ohn c9owell (trans# , (1:"3, x.ord; x.ord


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which ou and $ ma +e in disagreement# Plato uses colour + wa o. an example# )e

asks us to imagine a perception o. whiteness and then raises the point that i. whiteness

(he could ha*e used an sensi+le propert 15 is to +e in a state o. .lux, like e*er thing

must +e on this *iew, then it cannot sta white .or *er long0 so theres .lux o. that *er

thing, whiteness, and change into another colour, in order not to +e con*icted o. sta ing

constant in that respect#/ 16

%ocrates then raises the &uestion that i. e*en simple sensi+le properties are in such

perpetual .lux, how can we e*er re.er to them correctl using language To this

Theodorus replies0 $ndeed how could it +e possi+le with an other thing o. that kind i.

its alwa s slipping awa while one is speaking / 1" The point here seems to +e that i. $

make a Cudgement, + the time $ utter it or think it, its re.erent will ha*e changed and the Cudgement will no longer +e true# ealit it seems, on this )eracleitean *iew is simpl

too slipper to +e trul spoken o., leading Plato to conclude that we might as well sa o.

an thing that it is thus and not thus as each is e&uall true#

2ow it has +een argued that this mo*e + Plato is .allacious# This criticism hinges on the

point that i. e*er thing is perpetuall changing we could still make true Cudgements so

long as the were indexed to the particular time at which the were made 180 we could

think o. these Cudgements as snapshots o. realit , e#g# '$ saw the whiteness at t1#

Knother point which has +een raised is that while m Cudgements ma no longer +e

correct + the time $ express them, the ma still +e more accurate than other

Cudgements0 .or example i. the whiteness turns to pale gre m calling it white is more

accurate than our calling it green# 1: 2ow this second point, $ .eel is mistaken, at least in

the context o. the Theaetetus, as the measure doctrine didnt aim to secure that all o. our

15 @e must use the word propert here tentati*el and .or want o. a more ade&uate term0 i. the )eracleitean

doctrine were true, we would ha*e to adopt a whole new *oca+ular .or talking a+out the world as *irtuallall o. our terminolog (su+Cect, o+Cect, propert etc# presuppose some le*el o. sta+ilit # This point is noted

+ Plato at 15 d#16 Plato, Theaetetus, 15 d3-5, 7ohn c9owell (trans# , (1:"3, x.ord; x.ord 4Nhttp;OOplato#stan.ord#eduOarchi*esOwin ?1 OentriesOplato-theaetetusO #1: atthew Gol*in, )eraclitean Flux and


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knowledge claims would approximate the truth0 it aimed to secure that all o. our

knowledge claims would +e true# Being close to the truth in this instance there.ore, is

insu..icient#

The .irst criticism howe*er, does seem to +e more power.ul# $. we had the capacit to

index all o. our Cudgements to a time, could we accuratel speak o. a world in constant

.lux @ell ma +e we could, i. we assume that we alread ha*e a pre-existing language

with which we can work# But one pro+lem .or this approach is0 i. the world is in such

radical perpetual .lux, how could we esta+lish a language in the .irst place $t is in this

regard that this section o. the Theaetetus is sometimes related to @ittgensteins

discussion on the possi+ilit o. a pri*ate language # ?

@hile @ittgensteins discussion itsel. is characteristicall enigmatic, his general point

seems to +e that i. we were to attempt to produce a pri*ate language .or talking a+out our

inner sensations, which in turn are necessaril pri*ate, then we would lack an o+Cecti*e

means o. esta+lishing how a 'sign or word is used correctl # $n a )eracleitean world,

nothing would +e shared +etween ou and $, so how could we esta+lish a language, i#e# a

shared set o. s m+ols, .or talking a+out it# @ittgenstein +rings out this point when he

notes that i. e*er one had a +ox with something in it; we call it a L+eetleL# 2o one can

look into an one elseHs +ox, and e*er one sa s he knows what a +eetle is onl + looking

at his +eetle#I)ere it would +e &uite possi+le .or e*er one to ha*e something di..erent

in his +ox# ne might e*en imagine such a thing constantl changing#/ 1 2ow this point

might not +e articulated in Cust this wa + Plato, +ut i. sound, which $ +elie*e it is, this

point secures the last stage in Platos length reduction ad a+surdum that is the indirect

argument# @e ha*e thus shown that Platos indirect argument is a sound one0

Theaetetus de.inition needed Protagorean relati*ism to make it *ia+le, which in turn

needed )eracleitean .lux theor , and .lux theor has led us to a situation which would

seem to impl that the esta+lishment o. language simpl couldnt happen# The thesis that

knowledge is sense perception there.ore, has +een re.uted#

? >udwig @ittgenstein, Philosophical #n$esti%ations , D#E# # Knscom+e (trans# , (1:58, x.ord; BasilBlackwell #

1 $+id, pp#1??#

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e.erences

Ghappell, Timoth , LPlato on =nowledge in the Theaetetus L, The Stanford Encyclopedia

of Philosophy (Winter 2012 Edition) , Edward 2# Malta (ed# , < > 4

Nhttp;OOplato#stan.ord#eduOarchi*esOwin ?1 OentriesOplato-theaetetusO #

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9a*id Bostock, Platos Theaetetus , (1:88, x.ord; x.ord ee, The Secret Doctrine in Platos Theaetetus , ??5, x.ord %cholarship

online# Qhttp;OOwww#ox.ordscholarship#comO*iewO1?#1?:3O?1:: 6 5#??1#???1Oacpro.-:"8?1:: 6 :-chapter-5, Kccessed on "O O13#

les Burn eat, The Theaetetus of Plato , (1::?, $ndianapolis; )ackett Pu+lishing #

Plato, Theaetetus, 7ohn c9owell (trans# , (1:"3, x.ord; x.ord

Plato's theatetus

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