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ElementsinthePhilosophyofImmanuelKant
editedby
DesmondHogan
PrincetonUniversity
HowardWilliams
UniversityofCardiff
AllenWood
IndianaUniversity
KANT ON THE
RATIONALITY OF
MORALITY
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Informationonthistitle:www.cambridge.org/9781108438810
DOI:10.1017/9781108529761
©PaulGuyer2019
Thispublicationisincopyright.Subjecttostatutoryexception
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noreproductionofanypartmaytakeplacewithoutthewritten
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Firstpublished2019
AcataloguerecordforthispublicationisavailablefromtheBritishLibrary.
ISBN978-1-108-43881-0Paperback
ISSN2514-3824(print)
ISSN2397-9461(online)
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Kant on the Rationality of Morality
ElementsinthePhilosophyofImmanuelKant
DOI:10.1017/9781108529761
Firstpublishedonline:July2019
PaulGuyer
BrownUniversity,RhodeIsland
Authorforcorrespondence:[email protected]
Abstract:Kantclaimsthatthefundamentalprincipleofmoralityis
givenbypurereasonitself.ManyhaveinterpretedKanttoderivethis
principlefromaconceptionofpurepracticalreason(asopposedto
merelyprudentialreasoningaboutthemosteffectivemeansto
empiricallygivenends).ButKantmaintainedthatthereisonlyone
facultyofreason,althoughwithboththeoreticalandpractical
applications.ThisElementshowshowKantattemptedtoderivethe
fundamentalprincipleandgoalofmoralityfromthegeneralprinciples
ofreasonassuch.Toachievethis,ittakesreasonasKanthimself
conceivedofit,namely,asdefinedaboveallbythetwofundamental
principlesofnoncontradictionandsufficientreason,withathird
principleofsystematicityattachedtothesecondofthese.Itsmain
argumentisthatKantattemptedtoderivethefundamentalprincipleof
moralityinitsseveralformulationsbyapplyingtheprincipleof
noncontradictiontothefactthathumanbeingsareagentswiththeir
ownwills,andthecompleteobjectofmorality,thehighestgood,from
theprincipleofsufficientreason.Further,Kantsupposedboththatthe
sse applicationofthefundamentalprincipleofmoralitymustbe
rP y systematic,thusyieldingasystemofduties,andalsothatmoralityitself
tisre mustbepartofacompletesystemofboththeoreticalandpractical
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in cognition,ormorepreciselypartoftheidealofsuchacompletesystem
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e ofcognition.Kantalsoheldthatpurereasonispractical,inthesenseof
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ma considerhistheoreticaljustificationofthisclaimanditsempirical
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yb consequences.
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d Keywords:Kant,duty,freedom,fundamentalprincipleofmorality,highest
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hsilbu good,humansiutyffi,pcireinnctirpelaesoofnn,osynsctoenmtraatdiciicttyi,otnh,epurancctoicnadlirtieoanseodn,principleof
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Contents
1 Introduction 1
2 Reasons,Reasoning,andReasonasSuch 4
3 FromNoncontradictiontoUniversalizability 12
4 ThePrincipleofSufficientReasonandtheIdeaofthe
HighestGood 34
5 RationalityandtheSystemofDuties 43
6 ReasonasMotivation 51
7 KantianConstructivism 61
8 Conclusion 65
sse Bibliography 67
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ThePhilosophyofImmanuelKant 1
1Introduction
Immanuel Kant claims that the fundamental principle of morality is given by
purereasonitself.HisGroundworkoftheMetaphysicsoftheMorals,published
in1785,startswiththestatementthat“alaw,ifitistoholdmorally,thatis,as
a ground of an obligation ... must not be sought in the nature of the human
beingor in thecircumstances ofthe world in whichhe is placed, but a priori
simply in concepts of pure reason” (G 4: 389). He later grounds its central
argumentthatthemorallawdoesapplytoushumanbeingsontheclaimthatwe
dohavereason:“ahumanbeingreallyfindsinhimselfacapacitybywhichhe
distinguisheshimselffromallotherthings,evenfromhimselfinsofarasheis
affected by objects, and that is reason” (G 4: 452). The Critique of Practical
Reason, published in 1788 in order to defend the Groundwork, states that its
“firstquestion”willbewhether“purereasonofitselfalonesufficestodetermine
thewillorwhetheritcanbeadetermininggroundofthewillonlyasempirically
conditioned,”anddecisivelyoptsforthefirstofthesealternatives:“reasoncan
atleastsufficetodeterminethewillandalwayshasobjectiverealityinsofaras
volition alone is at issue” (CPrR 5: 15). By this Kant means, first, that pure
reason by itself suffices to furnish the fundamental principle of morality by
which the human will ought to be determined – in Kant’s model of human
action,intheagent’sselectionofparticularmaxims,suggestedbyexperience,
uponwhichtoactinparticularcircumstances–and,second,thatpurereason,by
itself,cansufficetomotivatehumanbeingstoactastheyoughttoact.1
1 Kant’sdivisionofthecognitivepowersor“faculties”ofhumanbeingsevolvedoverhiscareer,
sse andhisuseofhisownterminologywasoftenflexible.Hismostfundamentaldistinctionwas
rP betweensensibilityandintellect,withtheformerbeingourreceptivitytorepresentationsfrom
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tisrev erexpterernseanltoabtijoencsts.Oorurinmteornstalimstmateesdiaantedrtehperelasettnetratoiuornsaboifliptyarttoicourlagranoibzjeecotusratrheocuaglhletdabinotuutitsiuocnhs
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U (Anschauungen),andourgeneralrepresentationsofobjectsbymeansofmarksthatparticular
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gd objectsmaysharearecalledconcepts.FromtheCritiqueofPureReason(firstedition1781)
irb onward, Kant generally divides intellect into understanding and reason: understanding is the
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aC ability to form concepts and apply them either to particular objects or to other concepts in
yb judgments,althoughintheCritiqueofthePowerofJudgment(1790)Kantelevatesjudgment
en toaseparatefaculty;reasonis,inthefirstinstance,theabilitytoconcatenatejudgments,for
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o example,ininferences.Sensibility,understanding,judgment,andreasonallhavecharacteristic
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eh formsthatarenotderivedfromexperiencebutareappliedtoexperiencethroughempirically
silb givenintuitions:thepureformsofspaceandtimeinthecaseofsensibility,thepurecategoriesof
uP theunderstanding,andthepureideasofreason,namelyfirsttheformsofinferenceandthenthe
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67 unconditionedideasofthesoul,theworld-whole,andGod.Wecanhaveaprioriknowledgeof
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25 thestructureofthepureformsofsensibilityandunderstanding,andtheseformsarealsotheforms
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01 ofempiricalknowledge.Ifreasonisappliedtoourrepresentationsofhowthingsareintheformof
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87 intuitions,concepts,andjudgments,itistheoreticalreason;ifitisappliedtoourrepresentations
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/7 ofhowourownactionscouldbringaboutwhatoughttobe,itispracticalreason.Theattemptto
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01 knowwhatisthroughthetheoreticaluseofreasonalonewouldbespeculativereason,andin
.01 Kant’sviewisafailure,becausetheunconditionedideasofreasonbytheirverynatureoutstrip
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2 KantontheRationalityofMorality
Sometimes Kant seems to go even further than these claims, already bold
enough,toassertthatthehumanwillandpurereasonareidentical,aswhenhe
says that “the will is nothing other than practical reason” (G 4: 412). This
remark has led many to ask how Kant could possibly explain voluntary but
immoralbehaviorifheidentifiesreasonasthesourceofboththemorallawand
allwilledaction:Howcouldawillthataspurereasongivesitselfthemorallaw
then act on any ground other than that?2 But Kant clarifies this statement so
quicklythatnooneshouldbemisledbyit,forwhenhemakesitheisexplaining
whyprinciplesofreason,validforallrationalbeings,presentthemselvestous
human beings as imperatives:3 “If reason infallibly determines the will,” he
continues, then “the will is a capacity to choose only that which reason
independently of inclination cognizes as practically necessary, that is, as
good,” but “if the will is not in itself completely in conformity with reason
(asisactuallythecasewithhumanbeings),”thenthewillisnotidenticalwith
practical reason and what pure reason requires of us can appear to us as
aconstraintor“necessitation”(Nötigung)(G4:412).Humanbeingscanhave
inclinations – empirically given desires – toward actions contrary to what
morality requires, so what morality requires can come across to us as
a constraint. Likewise, the passage quoted from the Critique of Practical
Reason implies only that pure reason is capable of determining how the
human will should act, hardly that it determines how the human will or
human being always does act. To be sure, even this more limited claim was
aboldoneforKanttomakewhenDavidHumehadarguedthatmoralprinciples
must be grounded in sentiment rather than reason precisely because “morals”
sse must“haveaninfluenceontheactionsandaffections”and“reasonalone...can
rP y neverhaveanysuchinfluence.”4LaterwewillconsidersomeaspectsofKant’s
tisre theorythatpurereasoniscapableofmovingcreatureslikeuseventhoughwe
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aC doesnotpurporttotellushowtheactualworldisbuthowitoughttobe,itisinKant’sview
yb asuccess.Finally,thehumanabilitytodetermineactioniscalled“will”(Wille),butKantwill
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n ultimatelydividethatintotwoparts:theabilitytofurnishprinciplesofaction(Wille)andthe
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o abilitytochoosewhichprinciplestoactupon(thepowerofchoiceorWillkür).PureWilleis
deh identical to pure practical reason and provides the moral law. For Kant’s distinctions, see
silb especially CPR A19-20/B33-4, A298-302/B355-9, and A320/B376-7, as well as CPrR 5: 37
uP and15–16.
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67 2 ThisquestionwasraisedinKant’sowntimebyJohannAugustHeinrichUlrich(1746–1813)in
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25 Ulrich1788,andahundredyearslaterbyHenrySidgwickinSidwick1888.Forcontemporary
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187 3 ThevalidityofthemorallawforallrationalbeingsdoesnotcommitKanttotheactualexistence
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01 intendedtoguaranteethatthemorallawisnotgroundedonmerelycontingentaspectsofhuman
.01 nature.
/gro 4 Hume1739–40,Book3,Part1,Section1,paragraph6.
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ThePhilosophyofImmanuelKant 3
haveallsortsofdesirestoactotherwisethanasmoralitydemands.Butourfirst
questionissimply,howdidKantthinkthatpurereasonofitselfcanprovidethe
fundamentalprincipleofmorality?Or,morefully,howdidhethinkthatreason
can determine the fundamental principle and the proper “object” of morality,
that is, the goal of morality? How can reason alone determine even what we
oughttotrytodoandaccomplishinthenameofmorality?Whatisreason,in
Kant’sview,thatitcandothat?
Kant does talk about “practical reason.” Obviously: The title of his second
critiqueistheCritiqueofPracticalReason,anditsaimis“toshowthatthereis
purepracticalreason,andforthispurposeitcriticizesreason’sentirepractical
faculty”(CPrR5:3).BypracticalreasonKantmeansreasoninsofarasitbears
on volition and action, thus on our choice of principles for action and our
motivation by those principles, and his argument that there is such a thing as
purepracticalreasonisintendedtoshowthattheapplicationofreasontoaction
is not limited to providing merely technical advice5 on what means to use to
achieveendsthataresetforusbydesire,asHumehadassertedinhisTreatise.6
Kant’s position is that reason can give us moral principles and set our moral
goalsonitsown,aswellasmotivateustoactinaccordancewiththese.ButKant
alsoinsiststhat“therecan,intheend,beonlyoneandthesamereason,which
maybedistinguishedmerelyinitsapplication”(G4:391).Thatis,Kantdoes
notsupposethatpracticalreasonisafacultydistinctfromtheoreticalreason,or
that practical reason has a special form or special forms for reasoning about
actionthatcanbeunderstoodapartfromourformsforreasoningingeneral.For
Kant,theprinciplesthatdeterminehowweshouldactarefundamentaltoreason
sse assuch.
rP y Tobesure,therearedifferencesbetweentheapplicationofreasontomatters
tisre of fact and to matters of action. For one, in the theoretical use of reason we
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deh theoretical,thelatterpracticalcognitionofreason”(CPRBix-x).Foranother,
silbu andthisistheconclusionofKant’sentirephilosophy,therearethingsthereality
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.01 imperatives(G4:416–17).
/gro 6 SeeHume1739–40,Book3,Part1,Section1,paragraph12.
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4 KantontheRationalityofMorality
Thetheoreticaluseofreasonisrestrictedbythelimitsofsensibility,thatis,by
whatwecanactuallyperceive,andwecannotperceiveGodorourownfreedom
or immortality; yet, Kant holds, we are nevertheless entitled to affirm the
existence of these things on the basis of the practical use of reason. This
is because he thinks that it “would be absolutely impossible” for us to act
in accordance with the fundamental principle of morality if we could not
“presuppose” the existence of freedom, God, and our own immortality as
necessaryconditionsforthepossibilityofmoralsuccess,andthesethingsare
inanycasenotdisprovenbythetheoreticaluseofreason(CPRBxxviii);or,if
“practical reason has of itself original a priori principles with which certain
theoreticalpositionsareinseparablyconnected...thenitisclearthat,evenif
from the first perspective [reason’s] capacity does not extend to establishing
certainpropositionsaffirmatively,althoughtheydonotcontradictit,assoonas
thesesamepropositionsbelonginseparablytothepracticalinterestofpure
reason it must accept them.” In this sense the practical use of reason has
“primacy”overitstheoreticaluse,“assumingthatthisunionisnotcontingent
anddiscretionarybutbasedapriorionreasonitselfandthereforenecessary”
(CPrR5:121).Sothereiscertainlysomethingdistinctiveaboutpracticalreason
for Kant, namely, that once the fundamental principle of morality and its
necessarygoalhavebeendetermined,weareentitledtoholdbeliefsaboutthe
conditions for the successful realization of morally mandated action that we
would not be entitled to hold on theoretical grounds alone. To that extent it
makessensetotalkofpracticalreasonasadistinctiveformofreasoninKant’s
theory.
sse But Kant claims this special entitlement for practical reason to affirm the
rP y conditionsofthepossibilityofrealizingthegoalsthatmoralitysetsforusonly
tisre afterhehasderivedthefundamentalprincipleofmoralityfromreasonassuch,
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iln howwemayandmustact.Ourfirstquestion,then,ishowdoesKantthinkthat
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