the+critique+of+pure+reason_纯粹理性批判-第8部分

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is　not　that　of　being　refuted；　but　of　being　misunderstood。　For　my　own
part；　I　must　henceforward　abstain　from　controversy；　although　I　shall
carefully　attend　to　all　suggestions；　whether　from　friends　or
adversaries；　which　may　be　of　use　in　the　future　elaboration　of　the
system　of　this　propaedeutic。　As；　during　these　labours；　I　have　advanced
pretty　far　in　years　this　month　I　reach　my　sixty…fourth　year…　it　will
be　necessary　for　me　to　economize　time；　if　I　am　to　carry　out　my　plan　of
elaborating　the　metaphysics　of　nature　as　well　as　of　morals；　in
confirmation　of　the　correctness　of　the　principles　established　in
this　Critique　of　Pure　Reason；　both　speculative　and　practical；　and　I
must；　therefore；　leave　the　task　of　clearing　up　the　obscurities　of
the　present　work…　inevitable；　perhaps；　at　the　outset…　as　well　as；
the　defence　of　the　whole；　to　those　deserving　men；　who　have　made　my
system　their　own。　A　philosophical　system　cannot　e　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　prehensive　view　of　a　new　system。　By
confining　the　view　to　particular　passages；　taking　these　out　of　their
connection　and　paring　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　pare　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　pound　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　parative　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　monest　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；　i