the+critique+of+pure+reason_纯粹理性批判-第3部分

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itself。　Hence；　logic　is　properly　only　a　propaedeutic…　forms；　as　it
were；　the　vestibule　of　the　sciences；　and　while　it　is　necessary　to
enable　us　to　form　a　correct　judgement　with　regard　to　the　various
branches　of　knowledge；　still　the　acquisition　of　real；　substantive
knowledge　is　to　be　sought　only　in　the　sciences　properly　so　called；
that　is；　in　the　objective　sciences。
　　Now　these　sciences；　if　they　can　be　termed　rational　at　all；　must
contain　elements　of　a　priori　cognition；　and　this　cognition　may　stand
in　a　twofold　relation　to　its　object。　Either　it　may　have　to　determine
the　conception　of　the　object…　which　must　be　supplied　extraneously；
or　it　may　have　to　establish　its　reality。　The　former　is　theoretical；
the　latter　practical；　rational　cognition。　In　both；　the　pure　or　a
priori　element　must　be　treated　first；　and　must　be　carefully
distinguished　from　that　which　is　supplied　from　other　sources。　Any
other　method　can　only　lead　to　irremediable　confusion。
　　Mathematics　and　physics　are　the　two　theoretical　sciences　which
have　to　determine　their　objects　a　priori。　The　former　is　purely　a
priori；　the　latter　is　partially　so；　but　is　also　dependent　on　other
sources　of　cognition。
　　In　the　earliest　times　of　which　history　affords　us　any　record；
mathematics　had　already　entered　on　the　sure　course　of　science；　among
that　wonderful　nation；　the　Greeks。　Still　it　is　not　to　be　supposed　that
it　was　as　easy　for　this　science　to　strike　into；　or　rather　to　construct
for　itself；　that　royal　road；　as　it　was　for　logic；　in　which　reason
has　only　to　deal　with　itself。　On　the　contrary；　I　believe　that　it
must　have　remained　long…　chiefly　among　the　Egyptians…　in　the　stage
of　blind　groping　after　its　true　aims　and　destination；　and　that　it
was　revolutionized　by　the　happy　idea　of　one　man；　who　struck　out　and
determined　for　all　time　the　path　which　this　science　must　follow；　and
which　admits　of　an　indefinite　advancement。　The　history　of　this
intellectual　revolution…　much　more　important　in　its　results　than　the
discovery　of　the　passage　round　the　celebrated　Cape　of　Good　Hope…　and
of　its　author；　has　not　been　preserved。　But　Diogenes　Laertius；　in
naming　the　supposed　discoverer　of　some　of　the　simplest　elements　of
geometrical　demonstration…　elements　which；　according　to　the　ordinary
opinion；　do　not　even　require　to　be　proved…　makes　it　apparent　that
the　change　introduced　by　the　first　indication　of　this　new　path；　must
have　seemed　of　the　utmost　importance　to　the　mathematicians　of　that
age；　and　it　has　thus　been　secured　against　the　chance　of　oblivion。　A
new　light　must　have　flashed　on　the　mind　of　the　first　man　（Thales；　or
whatever　may　have　been　his　name）　who　demonstrated　the　properties　of
the　isosceles　triangle。　For　he　found　that　it　was　not　sufficient　to
meditate　on　the　figure；　as　it　lay　before　his　eyes；　or　the　conception
of　it；　as　it　existed　in　his　mind；　and　thus　endeavour　to　get　at　the
knowledge　of　its　properties；　but　that　it　was　necessary　to　produce
these　properties；　as　it　were；　by　a　positive　a　priori　construction；　and
that；　in　order　to　arrive　with　certainty　at　a　priori　cognition；　he　must
not　attribute　to　the　object　any　other　properties　than　those　which
necessarily　followed　from　that　which　he　had　himself；　in　accordance
with　his　conception；　placed　in　the　object。
　　A　much　longer　period　elapsed　before　physics　entered　on　the　highway
of　science。　For　it　is　only　about　a　century　and　a　half　since　the　wise
Bacon　gave　a　new　direction　to　physical　studies；　or　rather…　as　others
were　already　on　the　right　track…　imparted　fresh　vigour　to　the
pursuit　of　this　new　direction。　Here；　too；　as　in　the　case　of
mathematics；　we　find　evidence　of　a　rapid　intellectual　revolution。　In
the　remarks　which　follow　I　shall　confine　myself　to　the　empirical
side　of　natural　science。
　　When　Galilei　experimented　with　balls　of　a　definite　weight　on　the
inclined　plane；　when　Torricelli　caused　the　air　to　sustain　a　weight
which　he　had　calculated　beforehand　to　be　equal　to　that　of　a　definite
column　of　water；　or　when　Stahl；　at　a　later　period；　converted　metals
into　lime；　and　reconverted　lime　into　metal；　by　the　addition　and
subtraction　of　certain　elements；*　a　light　broke　upon　all　natural
philosophers。　They　learned　that　reason　only　perceives　that　which　it
produces　after　its　own　design；　that　it　must　not　be　content　to
follow；　as　it　were；　in　the　leading…strings　of　nature；　but　must　proceed
in　advance　with　principles　of　judgement　according　to　unvarying　laws；
and　pel　nature　to　reply　its　questions。　For　accidental　observations；
made　according　to　no　preconceived　plan；　cannot　be　united　under　a
necessary　law。　But　it　is　this　that　reason　seeks　for　and　requires。　It
is　only　the　principles　of　reason　which　can　give　to　concordant
phenomena　the　validity　of　laws；　and　it　is　only　when　experiment　is
directed　by　these　rational　principles　that　it　can　have　any　real
utility。　Reason　must　approach　nature　with　the　view；　indeed；　of
receiving　information　from　it；　not；　however；　in　the　character　of　a
pupil；　who　listens　to　all　that　his　master　chooses　to　tell　him；　but
in　that　of　a　judge；　who　pels　the　witnesses　to　reply　to　those
questions　which　he　himself　thinks　fit　to　propose。　To　this　single
idea　must　the　revolution　be　ascribed；　by　which；　after　groping　in　the
dark　for　so　many　centuries；　natural　science　was　at　length　conducted
into　the　path　of　certain　progress。

　　*I　do　not　here　follow　with　exactness　the　history　of　the　experimental
method；　of　which；　indeed；　the　first　steps　are　involved　in　some
obscurity。

　　We　e　now　to　metaphysics；　a　purely　speculative　science；　which
occupies　a　pletely　isolated　position　and　is　entirely　independent　of
the　teachings　of　experience。　It　deals　with　mere　conceptions…　not；　like
mathematics；　with　conceptions　applied　to　intuition…　and　in　it；
reason　is　the　pupil　of　itself　alone。　It　is　the　oldest　of　the　sciences；
and　would　still　survive；　even　if　all　the　rest　were　swallowed　up　in　the
abyss　of　an　all…destroying　barbarism。　But　it　has　not　yet　had　the
good　fortune　to　attain　to　the　sure　scientific　method。　This　will　be
apparent；　if　we　apply　the　tests　which　we　proposed　at　the　outset。　We
find　that　reason　perpetually　es　to　a　stand；　when　it　attempts　to
gain　a　priori　the　perception　even　of　those　laws　which　the　most
mon　experience　confirms。　We　find　it　pelled　to　retrace　its
steps　in　innumerable　instances；　and　to　abandon　the　path　on　which　it
had　entered；　because　this　does　not　lead　to　the　desired　result。　We
find；　too；　that　those　who　are　engaged　in　metaphysical　pursuits　are　far
from　being　able　to　agree　among　themselves；　but　that；　on　the
contrary；　this　science　appears　to　furnish　an　arena　specially　adapted
for　the　display　of　skill　or　the　exercise　of　strength　in　mock…contests…
a　field　in　which　no　batant　ever　yet　succeeded　in　gaining　an　inch　of
ground；　in　which；　at　least；　no　victory　was　ever　yet　crowned　with
permanent　possession。
　　This　leads　us　to　inquire　why　it　is　that；　in　metaphysics；　the　sure
path　of　science　has　not　hitherto　been　found。　Shall　we　suppose　that
it　is　impossible　to　discover　it？　Why　then　should　nature　have　visited
our　reason　with　restless　aspirations　after　it；　as　if　it　were　one　of
our　weightiest　concerns？　Nay；　more；　how　little　cause　should　we　have　to
place　confidence　in　our　reason；　if　it　abandons　us　in　a　matter　about
which；　most　of　all；　we　desire　to　know　the　truth…　and　not　only　so；
but　even　allures　us　to　the　pursuit　of　vain　phantoms；　only　to　betray　us
in　the　end？　Or；　if　the　path　has　only　hitherto　been　missed；　what
indications　do　we　possess　to　guide　us　in　a　renewed　investigation；
and　to　enable　us　to　hope　for　greater　success　than　has　fallen　to　the
lot　of　our　predecessors？
　　It　appears　to　me　that　the　examples　of　mathematics　and　natural
philosophy；　which；　as　we　have　seen；　were　brought　into　their　present
condition　by　a　sudden　revolution；　are　sufficiently　remarkable　to　fix
our　attention　on　the　essential　circumstances　of　the　change　which　has
proved　so　advantageous　to　them；　and　to　induce　us　to　make　the
experiment　of　imitating　them；　so　far　as　the　analogy　which；　as　rational
sciences；　they　bear　to　metaphysics　may　permit。　It　has　hitherto　been
assumed　that　our　cognition　must　conform　to　the　objects；　but　all
attempts　to　ascertain　anything　about　these　objects　a　priori；　by
means　of　conceptions；　and　thus　to　extend　the　range　of　our　knowledge；
have　been　rendered　abortive　by　this　assumption。　Let　us　then　make　the
experiment　whether　we　may　not　be　more　successful　in　metaphysics；　if　we
assume　that　the　objects　must　conform　to　our　cognition。　This　appears；
at　all　events；　to　accord　better　with　the　possibility　of　our　gaining
the　end　we　have　in　view；　that　is　to　say；　of　arriving　at　the
cognition　of　objects　a　priori；　of　determining　something　with　respect
to　these　objects；　before　they　are　given　to　us。　We　here　propose　to　do
just　what　Copernicus　did　in　attempting　to　explain　the　celestial
movements。　When　he　found　that　he　could　make　no　progress　by　assuming
that　all　the　heavenly　bodies　revolved　round　the　spectator；　he　reversed
the　process；　and　tried　the　experiment　of　assuming　that　the　spectator
revolved；　while　the　stars　remained　at　rest。　We　may　make　the　same
experiment　with　regard　to　the　intuition　of　objects。　If　the　intuition
must　conform　to　the　nature　of　the　objects；　I　do　not　see　how　we　can
know　anything　of　them　a　priori。　If；　on　the　other　hand；　the　object
conforms　to　the　nature　of　our　faculty　of　intuition；　I　can　then
easily　conceive　the　possibility　of　such　an　a　priori　knowledge。　Now
as　I　cannot　rest　in　the　mere　intuitions；　but…　if　they　are　to　bee
cognitions…　must　refer　them；　as　representations；　to　something；　as
object；　and　must　determine　the　latter　by　means　of　the　former；　here
again　there　are　two　courses　open　to　me。　Either；　first；　I　may　assume
that　the　conceptions；　by　which　I　effect　this　determination；　conform　to
the　object…　and　in　this　case　I　am　reduced　to　the　same　perplexity　as
before；　or　secondly；　I　may　assume　that　the　objects；　or；　which　is　the
same　thing；　that　experience；　in　which　alone　as　given　objects　they
are　cognized；　conform　to　my　conceptions…　and　then　I　am　at　no　loss
how　to　proceed。　For　experience　itself　is　a　mode　of　cognition　which
requires　understanding。　Before　objects；　are　given　to　me；　that　is；　a
priori；　I　must　presuppose　in　myself　laws　of　the　understanding　which
ar