the critique of pure reason- 第11部分

recourse　to　intuition；　to　arrive　at　the　sum　total　or　product　by

means　of　the　mere　analysis　of　our　conceptions。　just　as　little　is　any

principle　of　pure　geometry　analytical。　〃A　straight　line　between　two

points　is　the　shortest；〃　is　a　synthetical　proposition。　For　my

conception　of　straight　contains　no　notion　of　quantity；　but　is　merely

qualitative。　The　conception　of　the　shortest　is　therefore　fore　wholly

an　addition；　and　by　no　analysis　can　it　be　extracted　from　our

conception　of　a　straight　line。　Intuition　must　therefore　here　lend

its　aid；　by　means　of　which；　and　thus　only；　our　synthesis　is　possible。

　　Some　few　principles　preposited　by　geometricians　are；　indeed；

really　analytical；　and　depend　on　the　principle　of　contradiction。

They　serve；　however；　like　identical　propositions；　as　links　in　the

chain　of　method；　not　as　principles…　for　example；　a　=　a；　the　whole　is

equal　to　itself；　or　（a＋b）　》　a；　the　whole　is　greater　than　its　part。　And

yet　even　these　principles　themselves；　though　they　derive　their

validity　from　pure　conceptions；　are　only　admitted　in　mathematics

because　they　can　be　presented　in　intuition。　What　causes　us　here

commonly　to　believe　that　the　predicate　of　such　apodeictic　judgements

is　already　contained　in　our　conception；　and　that　the　judgement　is

therefore　analytical；　is　merely　the　equivocal　nature　of　the

expression。　We　must　join　in　thought　a　certain　predicate　to　a　given

conception；　and　this　necessity　cleaves　already　to　the　conception。

But　the　question　is；　not　what　we　must　join　in　thought　to　the　given

conception；　but　what　we　really　think　therein；　though　only　obscurely；

and　then　it　becomes　manifest　that　the　predicate　pertains　to　these

conceptions；　necessarily　indeed；　yet　not　as　thought　in　the

conception　itself；　but　by　virtue　of　an　intuition；　which　must　be

added　to　the　conception。

　　2。　The　science　of　natural　philosophy　（physics）　contains　in　itself

synthetical　judgements　a　priori；　as　principles。　I　shall　adduce　two

propositions。　For　instance；　the　proposition；　〃In　all　changes　of　the

material　world；　the　quantity　of　matter　remains　unchanged〃；　or；　that；

〃In　all　communication　of　motion；　action　and　reaction　must　always　be

equal。〃　In　both　of　these；　not　only　is　the　necessity；　and　therefore

their　origin　a　priori　clear；　but　also　that　they　are　synthetical

propositions。　For　in　the　conception　of　matter；　I　do　not　cogitate　its

permanency；　but　merely　its　presence　in　space；　which　it　fills。　I

therefore　really　go　out　of　and　beyond　the　conception　of　matter；　in

order　to　think　on　to　it　something　a　priori；　which　I　did　not　think　in

it。　The　proposition　is　therefore　not　analytical；　but　synthetical；

and　nevertheless　conceived　a　priori；　and　so　it　is　with　regard　to　the

other　propositions　of　the　pure　part　of　natural　philosophy。

　　3。　As　to　metaphysics；　even　if　we　look　upon　it　merely　as　an　attempted

science；　yet；　from　the　nature　of　human　reason；　an　indispensable　one；

we　find　that　it　must　contain　synthetical　propositions　a　priori。　It

is　not　merely　the　duty　of　metaphysics　to　dissect；　and　thereby

analytically　to　illustrate　the　conceptions　which　we　form　a　priori　of

things；　but　we　seek　to　widen　the　range　of　our　a　priori　knowledge。

For　this　purpose；　we　must　avail　ourselves　of　such　principles　as　add

something　to　the　original　conception…　something　not　identical　with；

nor　contained　in　it；　and　by　means　of　synthetical　judgements　a

priori；　leave　far　behind　us　the　limits　of　experience；　for　example；

in　the　proposition；　〃the　world　must　have　a　beginning；〃　and　such

like。　Thus　metaphysics；　according　to　the　proper　aim　of　the　science；

consists　merely　of　synthetical　propositions　a　priori。



　　VI。　The　Universal　Problem　of　Pure　Reason。



　　It　is　extremely　advantageous　to　be　able　to　bring　a　number　of

investigations　under　the　formula　of　a　single　problem。　For　in　this

manner；　we　not　only　facilitate　our　own　labour；　inasmuch　as　we　define

it　clearly　to　ourselves；　but　also　render　it　more　easy　for　others　to

decide　whether　we　have　done　justice　to　our　undertaking。　The　proper

problem　of　pure　reason；　then；　is　contained　in　the　question：　〃How　are

synthetical　judgements　a　priori　possible？〃

　　That　metaphysical　science　has　hitherto　remained　in　so　vacillating

a　state　of　uncertainty　and　contradiction；　is　only　to　be　attributed

to　the　fact　that　this　great　problem；　and　perhaps　even　the　difference

between　analytical　and　synthetical　judgements；　did　not　sooner

suggest　itself　to　philosophers。　Upon　the　solution　of　this　problem；

or　upon　sufficient　proof　of　the　impossibility　of　synthetical　knowledge

a　priori；　depends　the　existence　or　downfall　of　the　science　of

metaphysics。　Among　philosophers；　David　Hume　came　the　nearest　of　all　to

this　problem；　yet　it　never　acquired　in　his　mind　sufficient

precision；　nor　did　he　regard　the　question　in　its　universality。　On

the　contrary；　he　stopped　short　at　the　synthetical　proposition　of　the

connection　of　an　effect　with　its　cause　（principium　causalitatis）；

insisting　that　such　proposition　a　priori　was　impossible。　According

to　his　conclusions；　then；　all　that　we　term　metaphysical　science　is　a

mere　delusion；　arising　from　the　fancied　insight　of　reason　into　that

which　is　in　truth　borrowed　from　experience；　and　to　which　habit　has

given　the　appearance　of　necessity。　Against　this　assertion；　destructive

to　all　pure　philosophy；　he　would　have　been　guarded；　had　he　had　our

problem　before　his　eyes　in　its　universality。　For　he　would　then　have

perceived　that；　according　to　his　own　argument；　there　likewise　could

not　be　any　pure　mathematical　science；　which　assuredly　cannot　exist

without　synthetical　propositions　a　priori…　an　absurdity　from　which　his

good　understanding　must　have　saved　him。

　　In　the　solution　of　the　above　problem　is　at　the　same　time

comprehended　the　possibility　of　the　use　of　pure　reason　in　the

foundation　and　construction　of　all　sciences　which　contain

theoretical　knowledge　a　priori　of　objects；　that　is　to　say；　the

answer　to　the　following　questions：

　　How　is　pure　mathematical　science　possible？

　　How　is　pure　natural　science　possible？

　　Respecting　these　sciences；　as　they　do　certainly　exist；　it　may　with

propriety　be　asked；　how　they　are　possible？…　for　that　they　must　be

possible　is　shown　by　the　fact　of　their　really　existing。*　But　as　to

metaphysics；　the　miserable　progress　it　has　hitherto　made；　and　the　fact

that　of　no　one　system　yet　brought　forward；　far　as　regards　its　true

aim；　can　it　be　said　that　this　science　really　exists；　leaves　any　one　at

liberty　to　doubt　with　reason　the　very　possibility　of　its　existence。



　　*As　to　the　existence　of　pure　natural　science；　or　physics；　perhaps

many　may　still　express　doubts。　But　we　have　only　to　look　at　the

different　propositions　which　are　commonly　treated　of　at　the

commencement　of　proper　（empirical）　physical　science…　those；　for

example；　relating　to　the　permanence　of　the　same　quantity　of　matter；

the　vis　inertiae；　the　equality　of　action　and　reaction；　etc。…　to　be

soon　convinced　that　they　form　a　science　of　pure　physics　（physica　pura；

or　rationalis）；　which　well　deserves　to　be　separately　exposed　as　a

special　science；　in　its　whole　extent；　whether　that　be　great　or

confined。



　　Yet；　in　a　certain　sense；　this　kind　of　knowledge　must

unquestionably　be　looked　upon　as　given；　in　other　words；　metaphysics

must　be　considered　as　really　existing；　if　not　as　a　science；

nevertheless　as　a　natural　disposition　of　the　human　mind　（metaphysica

naturalis）。　For　human　reason；　without　any　instigations　imputable　to

the　mere　vanity　of　great　knowledge；　unceasingly　progresses；　urged　on

by　its　own　feeling　of　need；　towards　such　questions　as　cannot　be

answered　by　any　empirical　application　of　reason；　or　principles　derived

therefrom；　and　so　there　has　ever　really　existed　in　every　man　some

system　of　metaphysics。　It　will　always　exist；　so　soon　as　reason

awakes　to　the　exercise　of　its　power　of　speculation。　And　now　the

question　arises：　〃How　is　metaphysics；　as　a　natural　disposition；

possible？〃　In　other　words；　how；　from　the　nature　of　universal　human

reason；　do　those　questions　arise　which　pure　reason　proposes　to　itself；

and　which　it　is　impelled　by　its　own　feeling　of　need　to　answer　as

well　as　it　can？

　　But　as　in　all　the　attempts　hitherto　made　to　answer　the　questions

which　reason　is　prompted　by　its　very　nature　to　propose　to　itself；

for　example；　whether　the　world　had　a　beginning；　or　has　existed　from

eternity；　it　has　always　met　with　unavoidable　contradictions；　we　must

not　rest　satisfied　with　the　mere　natural　disposition　of　the　mind　to

metaphysics；　that　is；　with　the　existence　of　the　faculty　of　pure

reason；　whence；　indeed；　some　sort　of　metaphysical　system　always

arises；　but　it　must　be　possible　to　arrive　at　certainty　in　regard　to

the　question　whether　we　know　or　do　not　know　the　things　of　which

metaphysics　treats。　We　must　be　able　to　arrive　at　a　decision　on　the

subjects　of　its　questions；　or　on　the　ability　or　inability　of　reason　to

form　any　judgement　respecting　them；　and　therefore　either　to　extend

with　confidence　the　bounds　of　our　pure　r