1. Toastmasters Speech Two
John Heraghty
I think, therefore I am
'I thinktherefore Iam' - so goesthe famousphilosophical quotationfromthe renowned17th
centurymathematicianandphilosopherRene Descartes.Iwasalwaysfascinated bythe expression,
and italwayspiquedmyinterest,butIneverfollowedthroughonmyteenage interestsin
philosophy,whichincludednottakingupaCAO offerafterthe LeavingCert,thussendingme downa
differentpathcompletely.
But inrecenttimes,Ihave reacquaintedmyself withthe fieldof philosophy,if onlyina'dabbling'
sort of way.
So,I wouldlike togive a verybroad,general backgroundonthe writingsof Descartes,whichledhim
to the famousphrase.
He setout in1641 to explore whatitisto be human,to try and figure outwhatexactlyconstitutes
the mind,andto figure outif we can be certainthat everythingwe see aroundusisexactlyasit
appearsto be.
It was thisexaminationof howeverythingappearstobe thatmade up the majorityof hishuge
undertaking'Meditationsonfirstphilosophy',inwhichhe castdoubt overthe nature of reality,is
there an external worldindependentfromhisownmind,andhow couldhe be sure that anything
exists,includinghimself!!
Chief amongthese doubtingmechanisms,were hisnow famous'arguments'fromthe first
meditations.The three argumentswere:
- The argumentof error,or the appearance/realitygap
- The argumentof dreaming
and
- The evil demonargument

2. So,the argumentof error.
Whenwe observe anobject,or have an experience of the outsideworldbywayof our senses,itis
oftenthe case that the mental picture createdinour mindsisnota true depictionof how the object
actuallyis.For example,if youlookata pencil in a glassof water,the pencil appearstobe bentor
crooked.Andyoucan imagine thisorany otheroptical illusionlikeit.
Anotherexample,if youeatyourfavourite foodata time whenyouare flu-ridden,itcantaste
decidedlyunpleasant.Ineachof these cases,youknow thatthere isa reasonforthe mismatch
betweenthe objectasitisinthe real world,andthe mental picture thatis createdinyourmind.
But howcan you knowforsure thatyour sensesare representingthe true nature of anyobjectas it
exists,if there are somanyopportunitiesforyoursensestobe wrong?
The argumentof dreaming.
As youcan guess,thisargumentwassimplythatwhenwe are asleep,anddreaming,we oftenthink
that we are havinga 'live'experience,andit'snotuntil youare awake that you reflectonthe dream,
and realise howludicrousandsurreal itwas.But Descartesargued,how dowe know for sure that
we are not ina constant state of dreaming?He alsogivesthe example of hallucinating,andother
such statesthat the mindcan be in.
The evil demonargument.
One of the otherprominentdoubtingarguments,wasone thatIfoundextremelyquirky,and
somewhateerie - the evil demonargument.Descarteswasputtingforththe ideathatthere isa
maliciousthirdpartycontrollingourminds,presentingadistortedpicture of the external world,and
deceivingusasto the true nature of reality.
His nextvolume of work,the 2ndmeditations,wouldreveal the thoughtprocessthatledtothe
famousquotation.Descartesarguedthatbecause Iam havinga 'mental experience',ora thoughtas
a resultof some interactionwith the outside world,Icannotknow forsure that the experience
representsatrue depictionof the externalworld,butIcan be sure that I am at least'having'this
mental experience,orthinking!
Andin orderto 'have a thought' or to 'think',I mustbe something,andnot'nothing',Imust at least
exist.Thus,Ithink,therefore Iam!
So Descarteswassayingthat he cannot prove thathissensesaren'tdeceivinghim, orthathe isnot
dreaming,orthat he isn't beingdeceivedbyanevil demon.Buthe canbe sure thathe at leastexists!
Evenif it's justas a thinkingentity!!

3. So,to sum up,Rene Descartes'famousquotation - where diditcome from, how didhe arrive at that
statement?Hisargumentsputforthinthe 1st meditationsgave doubtasto the existence of the
external world,andhimself.Butinhissecondmeditations,he gave usthe ideaof himneedingto
exist,inordertohave thoughts,evenif theyare mismatchedfromthe externalworld,orif all wrong.
The questionasto there beinganactual external world,isdiscussedinDescartesThirdvolume of
the work onthe subject,the Thirdmeditations....Butthatmyfriends,isforanotherday.
Thank you.