the critique of pure reason- 第117部分

farther；　and　thus　I　know　the　limits…　merely　visual…　of　my　actual

knowledge　of　the　earth；　although　I　am　ignorant　of　the　limits　of　the

earth　itself。　But　if　I　have　got　so　far　as　to　know　that　the　earth　is

a　sphere；　and　that　its　surface　is　spherical；　I　can　cognize　a　priori

and　determine　upon　principles；　from　my　knowledge　of　a　small　part　of

this　surface…　say　to　the　extent　of　a　degree…　the　diameter　and

circumference　of　the　earth；　and　although　I　am　ignorant　of　the

objects　which　this　surface　contains；　I　have　a　perfect　knowledge　of　its

limits　and　extent。

　　The　sum　of　all　the　possible　objects　of　our　cognition　seems　to　us

to　be　a　level　surface；　with　an　apparent　horizon…　that　which　forms

the　limit　of　its　extent；　and　which　has　been　termed　by　us　the　idea　of

unconditioned　totality。　To　reach　this　limit　by　empirical　means　is

impossible；　and　all　attempts　to　determine　it　a　priori　according　to　a

principle；　are　alike　in　vain。　But　all　the　questions　raised　by　pure

reason　relate　to　that　which　lies　beyond　this　horizon；　or；　at　least；　in

its　boundary　line。

　　The　celebrated　David　Hume　was　one　of　those　geographers　of　human

reason　who　believe　that　they　have　given　a　sufficient　answer　to　all

such　questions　by　declaring　them　to　lie　beyond　the　horizon　of　our

knowledge…　a　horizon　which；　however；　Hume　was　unable　to　determine。　His

attention　especially　was　directed　to　the　principle　of　causality；　and

he　remarked　with　perfect　justice　that　the　truth　of　this　principle；　and

even　the　objective　validity　of　the　conception　of　a　cause；　was　not

commonly　based　upon　clear　insight；　that　is；　upon　a　priori　cognition。

Hence　he　concluded　that　this　law　does　not　derive　its　authority　from

its　universality　and　necessity；　but　merely　from　its　general

applicability　in　the　course　of　experience；　and　a　kind　of　subjective

necessity　thence　arising；　which　he　termed　habit。　From　the　inability　of

reason　to　establish　this　principle　as　a　necessary　law　for　the

acquisition　of　all　experience；　he　inferred　the　nullity　of　all　the

attempts　of　reason　to　pass　the　region　of　the　empirical。

　　This　procedure　of　subjecting　the　facta　of　reason　to　examination；

and；　if　necessary；　to　disapproval；　may　be　termed　the　censura　of

reason。　This　censura　must　inevitably　lead　us　to　doubts　regarding　all

transcendent　employment　of　principles。　But　this　is　only　the　second

step　in　our　inquiry。　The　first　step　in　regard　to　the　subjects　of

pure　reason；　and　which　marks　the　infancy　of　that　faculty；　is　that　of

dogmatism。　The　second；　which　we　have　just　mentioned；　is　that　of

scepticism；　and　it　gives　evidence　that　our　judgement　has　been　improved

by　experience。　But　a　third　step　is　necessary…　indicative　of　the

maturity　and　manhood　of　the　judgement；　which　now　lays　a　firm

foundation　upon　universal　and　necessary　principles。　This　is　the　period

of　criticism；　in　which　we　do　not　examine　the　facta　of　reason；　but

reason　itself；　in　the　whole　extent　of　its　powers；　and　in　regard　to　its

capability　of　a　priori　cognition；　and　thus　we　determine　not　merely　the

empirical　and　ever…shifting　bounds　of　our　knowledge；　but　its　necessary

and　eternal　limits。　We　demonstrate　from　indubitable　principles；　not

merely　our　ignorance　in　respect　to　this　or　that　subject；　but　in　regard

to　all　possible　questions　of　a　certain　class。　Thus　scepticism　is　a

resting　place　for　reason；　in　which　it　may　reflect　on　its　dogmatical

wanderings　and　gain　some　knowledge　of　the　region　in　which　it　happens

to　be；　that　it　may　pursue　its　way　with　greater　certainty；　but　it

cannot　be　its　permanent　dwelling…place。　It　must　take　up　its　abode　only

in　the　region　of　complete　certitude；　whether　this　relates　to　the

cognition　of　objects　themselves；　or　to　the　limits　which　bound　all

our　cognition。

　　Reason　is　not　to　be　considered　as　an　indefinitely　extended　plane；　of

the　bounds　of　which　we　have　only　a　general　knowledge；　it　ought

rather　to　be　compared　to　a　sphere；　the　radius　of　which　may　be　found

from　the　curvature　of　its　surface…　that　is；　the　nature　of　a　priori

synthetical　propositions…　and；　consequently；　its　circumference　and

extent。　Beyond　the　sphere　of　experience　there　are　no　objects　which

it　can　cognize；　nay；　even　questions　regarding　such　supposititious

objects　relate　only　to　the　subjective　principles　of　a　complete

determination　of　the　relations　which　exist　between　the

understanding…conceptions　which　lie　within　this　sphere。

　　We　are　actually　in　possession　of　a　priori　synthetical　cognitions；　as

is　proved　by　the　existence　of　the　principles　of　the　understanding；

which　anticipate　experience。　If　any　one　cannot　comprehend　the

possibility　of　these　principles；　he　may　have　some　reason　to　doubt

whether　they　are　really　a　priori；　but　he　cannot　on　this　account

declare　them　to　be　impossible；　and　affirm　the　nullity　of　the　steps

which　reason　may　have　taken　under　their　guidance。　He　can　only　say：

If　we　perceived　their　origin　and　their　authenticity；　we　should　be　able

to　determine　the　extent　and　limits　of　reason；　but；　till　we　can　do

this；　all　propositions　regarding　the　latter　are　mere　random

assertions。　In　this　view；　the　doubt　respecting　all　dogmatical

philosophy；　which　proceeds　without　the　guidance　of　criticism；　is

well　grounded；　but　we　cannot　therefore　deny　to　reason　the　ability　to

construct　a　sound　philosophy；　when　the　way　has　been　prepared　by　a

thorough　critical　investigation。　All　the　conceptions　produced；　and　all

the　questions　raised；　by　pure　reason；　do　not　lie　in　the　sphere　of

experience；　but　in　that　of　reason　itself；　and　hence　they　must　be

solved；　and　shown　to　be　either　valid　or　inadmissible；　by　that　faculty。

We　have　no　right　to　decline　the　solution　of　such　problems；　on　the

ground　that　the　solution　can　be　discovered　only　from　the　nature　of

things；　and　under　pretence　of　the　limitation　of　human　faculties；　for

reason　is　the　sole　creator　of　all　these　ideas；　and　is　therefore

bound　either　to　establish　their　validity　or　to　expose　their　illusory

nature。

　　The　polemic　of　scepticism　is　properly　directed　against　the

dogmatist；　who　erects　a　system　of　philosophy　without　having　examined

the　fundamental　objective　principles　on　which　it　is　based；　for　the

purpose　of　evidencing　the　futility　of　his　designs；　and　thus　bringing

him　to　a　knowledge　of　his　own　powers。　But；　in　itself；　scepticism

does　not　give　us　any　certain　information　in　regard　to　the　bounds　of

our　knowledge。　All　unsuccessful　dogmatical　attempts　of　reason　are

facia；　which　it　is　always　useful　to　submit　to　the　censure　of　the

sceptic。　But　this　cannot　help　us　to　any　decision　regarding　the

expectations　which　reason　cherishes　of　better　success　in　future

endeavours；　the　investigations　of　scepticism　cannot；　therefore；　settle

the　dispute　regarding　the　rights　and　powers　of　human　reason。

　　Hume　is　perhaps　the　ablest　and　most　ingenious　of　all　sceptical

philosophers；　and　his　writings　have；　undoubtedly；　exerted　the　most

powerful　influence　in　awakening　reason　to　a　thorough　investigation

into　its　own　powers。　It　will；　therefore；　well　repay　our　labours　to

consider　for　a　little　the　course　of　reasoning　which　he　followed　and

the　errors　into　which　he　strayed；　although　setting　out　on　the　path

of　truth　and　certitude。

　　Hume　was　probably　aware；　although　he　never　clearly　developed　the

notion；　that　we　proceed　in　judgements　of　a　certain　class　beyond　our

conception　if　the　object。　I　have　termed　this　kind　of　judgement

synthetical。　As　regard　the　manner　in　which　I　pass　beyond　my　conception

by　the　aid　of　experience；　no　doubts　can　be　entertained。　Experience

is　itself　a　synthesis　of　perceptions；　and　it　employs　perceptions　to

increment　the　conception；　which　I　obtain　by　means　of　another

perception。　But　we　feel　persuaded　that　we　are　able　to　proceed　beyond　a

conception；　and　to　extend　our　cognition　a　priori。　We　attempt　this　in

two　ways…　either；　through　the　pure　understanding；　in　relation　to

that　which　may　become　an　object　of　experience；　or；　through　pure

reason；　in　relation　to　such　properties　of　things；　or　of　the

existence　of　things；　as　can　never　be　presented　in　any　experience。　This

sceptical　philosopher　did　not　distinguish　these　two　kinds　of

judgements；　as　he　ought　to　have　done；　but　regarded　this　augmentation

of　conceptions；　and；　if　we　may　so　express　ourselves；　the　spontaneous

generation　of　understanding　and　reason；　independently　of　the

impregnation　of　experience；　as　altogether　impossible。　The　so…called

a　priori　principles　of　these　faculties　he　consequently　held　to　be

invalid　and　imaginary；　and　regarded　them　as　nothing　but　subjective

habits　of　thought　originating　in　experience；　and　therefore　purely

empirical　and　contingent　rules；　to　which　we　attribute　a　spurious

necessity　and　universality。　In　support　of　this　strange　assertion；　he

referred　us　to　the　generally　acknowledged　principle　of　the　relation

between　cause　and　effect。　No　faculty　of　the　mind　can　conduct　us　from

the　conception　of　a　thing　to　the　existence　of　something　else；　and

hence　he　believed　he　could　infer　that；　without　experience；　we

possess　no　source　from　which　we　can　augment　a　conception；　and　no

ground　sufficient　to　justify　us　in　framing　a　judgement　that　is　to

extend　our　cognition　a　priori。　That　the　light　of　the　sun；　which　shines

upon　a　piece　of　wax；　at　the　same　time　melts　it；　while　it　hardens　clay；

no　power　of　the　understanding　could　infer　from　the　conceptions　which

we　previously　possessed　of　these　substances；　much　less　is　there　any

a　priori　law　that　could　conduct　us　to　such　a　conclusion；　which

experience　alone　can　certify。　On　the　other　hand；　we　have　seen　in　our

discussion　of　transcendental　logic；　that；　although　we　can　never

proceed　immediately　beyond　the　content　of　the　conception　which　is

given　us；　we　can　always　cognize　completely　a　priori…　in　relation；

however；　to　a　third　term；　namely；　possible　experience…　the　law　of

its　connection　with　other　things。　For　example；　if　I　observe　that　a

piece　of　wax　melts；　I　can　cognize　a　priori　that　there　must　have　been

something　（the　sun's　heat）　preceding；　which　this　law；　although；

without　the　ai