the critique of pure reason-第7章

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the　defence　of　the　whole；　to　those　deserving　men；　who　have　made　my

system　their　own。　A　philosophical　system　cannot　come　forward　armed

at　all　points　like　a　mathematical　treatise；　and　hence　it　may　be

quite　possible　to　take　objection　to　particular　passages；　while　the

organic　structure　of　the　system；　considered　as　a　unity；　has　no

danger　to　apprehend。　But　few　possess　the　ability；　and　still　fewer

the　inclination；　to　take　a　comprehensive　view　of　a　new　system。　By

confining　the　view　to　particular　passages；　taking　these　out　of　their

connection　and　comparing　them　with　one　another；　it　is　easy　to　pick　out

apparent　contradictions；　especially　in　a　work　written　with　any　freedom

of　style。　These　contradictions　place　the　work　in　an　unfavourable　light

in　the　eyes　of　those　who　rely　on　the　judgement　of　others；　but　are

easily　reconciled　by　those　who　have　mastered　the　idea　of　the　whole。　If

a　theory　possesses　stability　in　itself；　the　action　and　reaction

which　seemed　at　first　to　threaten　its　existence　serve　only；　in　the

course　of　time；　to　smooth　down　any　superficial　roughness　or

inequality；　and…　if　men　of　insight；　impartiality；　and　truly　popular

gifts；　turn　their　attention　to　it…　to　secure　to　it；　in　a　short　time；

the　requisite　elegance　also。



　　Konigsberg；　April　1787。

INTRODUCTION

　　　　　　　　　　　　　　　　　　　　　INTRODUCTION。



　　I。　Of　the　difference　between　Pure　and　Empirical　Knowledge



　　That　all　our　knowledge　begins　with　experience　there　can　be　no　doubt。

For　how　is　it　possible　that　the　faculty　of　cognition　should　be

awakened　into　exercise　otherwise　than　by　means　of　objects　which　affect

our　senses；　and　partly　of　themselves　produce　representations；　partly

rouse　our　powers　of　understanding　into　activity；　to　compare　to

connect；　or　to　separate　these；　and　so　to　convert　the　raw　material　of

our　sensuous　impressions　into　a　knowledge　of　objects；　which　is

called　experience？　In　respect　of　time；　therefore；　no　knowledge　of　ours

is　antecedent　to　experience；　but　begins　with　it。

　　But；　though　all　our　knowledge　begins　with　experience；　it　by　no　means

follows　that　all　arises　out　of　experience。　For；　on　the　contrary；　it　is

quite　possible　that　our　empirical　knowledge　is　a　compound　of　that

which　we　receive　through　impressions；　and　that　which　the　faculty　of

cognition　supplies　from　itself　（sensuous　impressions　giving　merely　the

occasion）；　an　addition　which　we　cannot　distinguish　from　the　original

element　given　by　sense；　till　long　practice　has　made　us　attentive　to；

and　skilful　in　separating　it。　It　is；　therefore；　a　question　which

requires　close　investigation；　and　not　to　be　answered　at　first　sight；

whether　there　exists　a　knowledge　altogether　independent　of　experience；

and　even　of　all　sensuous　impressions？　Knowledge　of　this　kind　is　called

a　priori；　in　contradistinction　to　empirical　knowledge；　which　has　its

sources　a　posteriori；　that　is；　in　experience。

　　But　the　expression；　〃a　priori；〃　is　not　as　yet　definite　enough

adequately　to　indicate　the　whole　meaning　of　the　question　above

started。　For；　in　speaking　of　knowledge　which　has　its　sources　in

experience；　we　are　wont　to　say；　that　this　or　that　may　be　known　a

priori；　because　we　do　not　derive　this　knowledge　immediately　from

experience；　but　from　a　general　rule；　which；　however；　we　have　itself

borrowed　from　experience。　Thus；　if　a　man　undermined　his　house；　we　say；

〃he　might　know　a　priori　that　it　would　have　fallen；〃　that　is；　he　needed

not　to　have　waited　for　the　experience　that　it　did　actually　fall。　But

still；　a　priori；　he　could　not　know　even　this　much。　For；　that　bodies

are　heavy；　and；　consequently；　that　they　fall　when　their　supports　are

taken　away；　must　have　been　known　to　him　previously；　by　means　of

experience。

　　By　the　term　〃knowledge　a　priori；〃　therefore；　we　shall　in　the

sequel　understand；　not　such　as　is　independent　of　this　or　that　kind

of　experience；　but　such　as　is　absolutely　so　of　all　experience。　Opposed

to　this　is　empirical　knowledge；　or　that　which　is　possible　only　a

posteriori；　that　is；　through　experience。　Knowledge　a　priori　is

either　pure　or　impure。　Pure　knowledge　a　priori　is　that　with　which　no

empirical　element　is　mixed　up。　For　example；　the　proposition；　〃Every

change　has　a　cause；〃　is　a　proposition　a　priori；　but　impure；　because

change　is　a　conception　which　can　only　be　derived　from　experience。



　　II。　The　Human　Intellect；　even　in　an　Unphilosophical　State；

　　　　　　is　in　Possession　of　Certain　Cognitions　〃a　priori〃。



　　The　question　now　is　as　to　a　criterion；　by　which　we　may　securely

distinguish　a　pure　from　an　empirical　cognition。　Experience　no　doubt

teaches　us　that　this　or　that　object　is　constituted　in　such　and　such

a　manner；　but　not　that　it　could　not　possibly　exist　otherwise。　Now；

in　the　first　place；　if　we　have　a　proposition　which　contains　the　idea

of　necessity　in　its　very　conception；　it　is　a　if；　moreover；　it　is　not

derived　from　any　other　proposition；　unless　from　one　equally

involving　the　idea　of　necessity；　it　is　absolutely　priori。　Secondly；　an

empirical　judgement　never　exhibits　strict　and　absolute；　but　only

assumed　and　comparative　universality　（by　induction）；　therefore；　the

most　we　can　say　is…　so　far　as　we　have　hitherto　observed；　there　is　no

exception　to　this　or　that　rule。　If；　on　the　other　hand；　a　judgement

carries　with　it　strict　and　absolute　universality；　that　is；　admits　of

no　possible　exception；　it　is　not　derived　from　experience；　but　is　valid

absolutely　a　priori。

　　Empirical　universality　is；　therefore；　only　an　arbitrary　extension　of

validity；　from　that　which　may　be　predicated　of　a　proposition　valid

in　most　cases；　to　that　which　is　asserted　of　a　proposition　which

holds　good　in　all；　as；　for　example；　in　the　affirmation；　〃All　bodies

are　heavy。〃　When；　on　the　contrary；　strict　universality　characterizes　a

judgement；　it　necessarily　indicates　another　peculiar　source　of

knowledge；　namely；　a　faculty　of　cognition　a　priori。　Necessity　and

strict　universality；　therefore；　are　infallible　tests　for

distinguishing　pure　from　empirical　knowledge；　and　are　inseparably

connected　with　each　other。　But　as　in　the　use　of　these　criteria　the

empirical　limitation　is　sometimes　more　easily　detected　than　the

contingency　of　the　judgement；　or　the　unlimited　universality　which　we

attach　to　a　judgement　is　often　a　more　convincing　proof　than　its

necessity；　it　may　be　advisable　to　use　the　criteria　separately；　each

being　by　itself　infallible。

　　Now；　that　in　the　sphere　of　human　cognition　we　have　judgements

which　are　necessary；　and　in　the　strictest　sense　universal；

consequently　pure　a　priori；　it　will　be　an　easy　matter　to　show。　If　we

desire　an　example　from　the　sciences；　we　need　only　take　any　proposition

in　mathematics。　If　we　cast　our　eyes　upon　the　commonest　operations　of

the　understanding；　the　proposition；　〃Every　change　must　have　a

cause；〃　will　amply　serve　our　purpose。　In　the　latter　case；　indeed；

the　conception　of　a　cause　so　plainly　involves　the　conception　of　a

necessity　of　connection　with　an　effect；　and　of　a　strict　universality

of　the　law；　that　the　very　notion　of　a　cause　would　entirely

disappear；　were　we　to　derive　it；　like　Hume；　from　a　frequent

association　of　what　happens　with　that　which　precedes；　and　the　habit

thence　originating　of　connecting　representations…　the　necessity

inherent　in　the　judgement　being　therefore　merely　subjective。

Besides；　without　seeking　for　such　examples　of　principles　existing　a

priori　in　cognition；　we　might　easily　show　that　such　principles　are　the

indispensable　basis　of　the　possibility　of　experience　itself；　and

consequently　prove　their　existence　a　priori。　For　whence　could　our

experience　itself　acquire　certainty；　if　all　the　rules　on　which　it

depends　were　themselves　empirical；　and　consequently　fortuitous？　No

one；　therefore；　can　admit　the　validity　of　the　use　of　such　rules　as

first　principles。　But；　for　the　present；　we　may　content　ourselves

with　having　established　the　fact；　that　we　do　possess　and　exercise　a

faculty　of　pure　a　priori　cognition；　and；　secondly；　with　having　pointed

out　the　proper　tests　of　such　cognition；　namely；　universality　and

necessity。

　　Not　only　in　judgements；　however；　but　even　in　conceptions；　is　an　a

priori　origin　manifest。　For　example；　if　we　take　away　by　degrees　from

our　conceptions　of　a　body　all　that　can　be　referred　to　mere　sensuous

experience…　colour；　hardness　or　softness；　weight；　even

impenetrability…　the　body　will　then　vanish；　but　the　space　which　it

occupied　still　remains；　and　this　it　is　utterly　impossible　to

annihilate　in　thought。　Again；　if　we　take　away；　in　like　manner；　from

our　empirical　conception　of　any　object；　corporeal　or　incorporeal；

all　properties　which　mere　experience　has　taught　us　to　connect　with　it；

still　we　cannot　think　away　those　through　which　we　cogitate　it　as

substance；　or　adhering　to　substance；　although　our　conception　of

substance　is　more　determined　than　that　of　an　object。　Compelled；

therefore；　by　that　necessity　with　which　the　conception　of　substance

forces　itself　upon　us；　we　must　confess　that　it　has　its　seat　in　our

faculty　of　cognition　a　priori。



　　III。　Philosophy　stands　in　need　of　a　Science　which　shall

　　　　　　　Determine　the　Possibility；　Principles；　and　Extent　of

　　　　　　　Human　Knowledge　〃a　priori〃



　　Of　far　more　importance　than　all　that　has　been　above　said；　is　the

consideration　that　certain　of　our　cognitions　rise　completely　above　the

sphere　of　all　possible　experience；　and　by　means　of　conceptions；　to

which　there　exists　in　the　whole　extent　of　experience　no

corresponding　object；　seem　to　extend　the　range　of　our　judgements

beyond　its　bounds。　And　just　in　this　transcendental　or　supersensible

sphere；　where　experience　affords　us　neither　instruction　nor

guidance；　lie　the　investigations　of　reason；　which；　on　account　of　their

importance；　we　consider　far　preferable　to；　and　as　having　a　far　more

elevated　aim　than；　all　that　the　understanding　can　achieve　within　the

sphere　of　sensuous　phenomena。　So　high　a　value　do　we　set　upon　these

investigations；　that　even　at　the　risk　of　error；　we　persist　in

following　them　out；　and　permit　neither　doubt　nor　disregard　nor

indifference　to　restrain　us　from　the　pursuit。　These　unavoidable

problems　of　mere　pure　reason　are　God；　freedom　（of　will）；　and

immortality。　The　science　which；　with　all　its　preliminaries；　has　for

its　especial　object　the　solution　of　these　problems　is　named

metaphysics…　a　science　which　is　at　the　very　outset　dogmatical；　that

is；　it　confidently　takes　upon　itself　the　execution　of　this　task

without　any　previous　investigation　of　the　ability　or　inability　of

reason　for　such　an　undertaking。

　　Now　the　safe　ground　of　experience　being　thus　abandoned；　it　seems

nevertheless　natural　that　we　should　hesitate　to　erect　a　building

with　the　cognitions　we　possess；　without　knowing　whence　they　come；

and　on　the　strength　of　principles；　the　origin　of　which　is

undiscovered。　Instead　of　thus　trying　to　build　without　a　foundation；　it

is　rather　to　be　expected　that　we　should　long　ago　have　put　the

question；　how　the　understanding　can　arrive　at　thes