the critique of practical reason-第29章

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　expectation　that　we　may　perhaps　some　day　be　able　to　discern　the　unity　of　the　whole　faculty　of　reason　（theoretical　as　well　as　practical）　and　be　able　to　derive　all　from　one　principle；　which；　is　what　human　reason　inevitably　demands；　as　it　finds　complete　satisfaction　only　in　a　perfectly　systematic　unity　of　its　knowledge。　　　If　now　we　consider　also　the　contents　of　the　knowledge　that　we　can　have　of　a　pure　practical　reason；　and　by　means　of　it；　as　shown　by　the　Analytic；　we　find；　along　with　a　remarkable　analogy　between　it　and　the　theoretical；　no　less　remarkable　differences。　As　regards　the　theoretical；　the　faculty　of　a　pure　rational　cognition　a　priori　could　be　easily　and　evidently　proved　by　examples　from　sciences　（in　which；　as　they　put　their　principles　to　the　test　in　so　many　ways　by　methodical　use；　there　is　not　so　much　reason　as　in　common　knowledge　to　fear　a　secret　mixture　of　empirical　principles　of　cognition）。　But；　that　pure　reason　without　the　admixture　of　any　empirical　principle　is　practical　of　itself；　this　could　only　be　shown　from　the　commonest　practical　use　of　reason；　by　verifying　the　fact；　that　every　man's　natural　reason　acknowledges　the　supreme　practical　principle　as　the　supreme　law　of　his　will…　a　law　completely　a　priori　and　not　depending　on　any　sensible　data。　It　was　necessary　first　to　establish　and　verify　the　purity　of　its　origin；　even　in　the　judgement　of　this　common　reason；　before　science　could　take　it　in　hand　to　make　use　of　it；　as　a　fact；　that　is；　prior　to　all　disputation　about　its　possibility；　and　all　the　consequences　that　may　be　drawn　from　it。　But　this　circumstance　may　be　readily　explained　from　what　has　just　been　said；　because　practical　pure　reason　must　necessarily　begin　with　principles；　which　therefore　must　be　the　first　data；　the　foundation　of　all　science；　and　cannot　be　derived　from　it。　It　was　possible　to　effect　this　verification　of　moral　principles　as　principles　of　a　pure　reason　quite　well；　and　with　sufficient　certainty；　by　a　single　appeal　to　the　judgement　of　common　sense；　for　this　reason；　that　anything　empirical　which　might　slip　into　our　maxims　as　a　determining　principle　of　the　will　can　be　detected　at　once　by　the　feeling　of　pleasure　or　pain　which　necessarily　attaches　to　it　as　exciting　desire；　whereas　pure　practical　reason　positively　refuses　to　admit　this　feeling　into　its　principle　as　a　condition。　The　heterogeneity　of　the　determining　principles　（the　empirical　and　rational）　is　clearly　detected　by　this　resistance　of　a　practically　legislating　reason　against　every　admixture　of　inclination；　and　by　a　peculiar　kind　of　sentiment；　which；　however；　does　not　precede　the　legislation　of　the　practical　reason；　but；　on　the　contrary；　is　produced　by　this　as　a　constraint；　namely；　by　the　feeling　of　a　respect　such　as　no　man　has　for　inclinations　of　whatever　kind　but　for　the　law　only；　and　it　is　detected　in　so　marked　and　prominent　a　manner　that　even　the　most　uninstructed　cannot　fail　to　see　at　once　in　an　example　presented　to　him；　that　empirical　principles　of　volition　may　indeed　urge　him　to　follow　their　attractions；　but　that　he　can　never　be　expected　to　obey　anything　but　the　pure　practical　law　of　reason　alone。　　　The　distinction　between　the　doctrine　of　happiness　and　the　doctrine　of　morality；　in　the　former　of　which　empirical　principles　constitute　the　entire　foundation；　while　in　the　second　they　do　not　form　the　smallest　part　of　it；　is　the　first　and　most　important　office　of　the　Analytic　of　pure　practical　reason；　and　it　must　proceed　in　it　with　as　much　exactness　and；　so　to　speak；　scrupulousness；　as　any　geometer　in　his　work。　The　philosopher；　however；　has　greater　difficulties　to　contend　with　here　（as　always　in　rational　cognition　by　means　of　concepts　merely　without　construction）；　because　he　cannot　take　any　intuition　as　a　foundation　（for　a　pure　noumenon）。　He　has；　however；　this　advantage　that；　like　the　chemist；　he　can　at　any　time　make　an　experiment　with　every　man's　practical　reason　for　the　purpose　of　distinguishing　the　moral　（pure）　principle　of　determination　from　the　empirical；　namely；　by　adding　the　moral　law　（as　a　determining　principle）　to　the　empirically　affected　will　（e。g。；　that　of　the　man　who　would　be　ready　to　lie　because　he　can　gain　something　thereby）。　It　is　as　if　the　analyst　added　alkali　to　a　solution　of　lime　in　hydrochloric　acid；　the　acid　at　once　forsakes　the　lime；　combines　with　the　alkali；　and　the　lime　is　precipitated。　just　in　the　same　way；　if　to　a　man　who　is　otherwise　honest　（or　who　for　this　occasion　places　himself　only　in　thought　in　the　position　of　an　honest　man）；　we　present　the　moral　law　by　which　he　recognises　the　worthlessness　of　the　liar；　his　practical　reason　（in　forming　a　judgement　of　what　ought　to　be　done）　at　once　forsakes　the　advantage；　combines　with　that　which　maintains　in　him　respect　for　his　own　person　（truthfulness）；　and　the　advantage　after　it　has　been　separated　and　washed　from　every　particle　of　reason　（which　is　altogether　on　the　side　of　duty）　is　easily　weighed　by　everyone；　so　that　it　can　enter　into　combination　with　reason　in　other　cases；　only　not　where　it　could　be　opposed　to　the　moral　law；　which　reason　never　forsakes；　but　most　closely　unites　itself　with。　　　But　it　does　not　follow　that　this　distinction　between　the　principle　of　happiness　and　that　of　morality　is　an　opposition　between　them；　and　pure　practical　reason　does　not　require　that　we　should　renounce　all　claim　to　happiness；　but　only　that　the　moment　duty　is　in　question　we　should　take　no　account　of　happiness。　It　may　even　in　certain　respects　be　a　duty　to　provide　for　happiness；　partly；　because　（including　skill；　wealth；　riches）　it　contains　means　for　the　fulfilment　of　our　duty；　partly；　because　the　absence　of　it　（e。g。；　poverty）　implies　temptations　to　transgress　our　duty。　But　it　can　never　be　an　immediate　duty　to　promote　our　happiness；　still　less　can　it　be　the　principle　of　all　duty。　Now；　as　all　determining　principles　of　the　will；　except　the　law　of　pure　practical　reason　alone　（the　moral　law）；　are　all　empirical　and；　therefore；　as　such；　belong　to　the　principle　of　happiness；　they　must　all　be　kept　apart　from　the　supreme　principle　of　morality　and　never　be　incorporated　with　it　as　a　condition；　since　this　would　be　to　destroy　all　moral　worth　just　as　much　as　any　empirical　admixture　with　geometrical　principles　would　destroy　the　certainty　of　mathematical　evidence；　which　in　Plato's　opinion　is　the　most　excellent　thing　in　mathematics；　even　surpassing　their　utility。　　　Instead；　however；　of　the　deduction　of　the　supreme　principle　of　pure　practical　reason；　that　is；　the　explanation　of　the　possibility　of　such　a　knowledge　a　priori；　the　utmost　we　were　able　to　do　was　to　show　that　if　we　saw　the　possibility　of　the　freedom　of　an　efficient　cause；　we　should　also　see　not　merely　the　possibility；　but　even　the　necessity；　of　the　moral　law　as　the　supreme　practical　law　of　rational　beings；　to　whom　we　attribute　freedom　of　causality　of　their　will；　because　both　concepts　are　so　inseparably　united　that　we　might　define　practical　freedom　as　independence　of　the　will　on　anything　but　the　moral　law。　But　we　cannot　perceive　the　possibility　of　the　freedom　of　an　efficient　cause；　especially　in　the　world　of　sense；　we　are　fortunate　if　only　we　can　be　sufficiently　assured　that　there　is　no　proof　of　its　impossibility；　and　are　now；　by　the　moral　law　which　postulates