the critique of practical reason- 第13部分

cal；　that　is；　proceeded　from　one　property　to　another；　by　virtue　of　identity　and；　consequently；　according　to　the　principle　of　contradiction。　This；　however；　is　not　the　case；　since；　on　the　contrary；　they　are　synthetical；　and　although　geometry；　for　example；　has　not　to　do　with　the　existence　of　things；　but　only　with　their　a　priori　properties　in　a　possible　intuition；　yet　it　proceeds　just　as　in　the　case　of　the　causal　notion；　from　one　property　（A）　to　another　wholly　distinct　（B）；　as　necessarily　connected　with　the　former。　Nevertheless；　mathematical　science；　so　highly　vaunted　for　its　apodeictic　certainty；　must　at　last　fall　under　this　empiricism　for　the　same　reason　for　which　Hume　put　custom　in　the　place　of　objective　necessity　in　the　notion　of　cause　and；　in　spite　of　all　its　pride；　must　consent　to　lower　its　bold　pretension　of　claiming　assent　a　priori　and　depend　for　assent　to　the　universality　of　its　propositions　on　the　kindness　of　observers；　who；　when　called　as　witnesses；　would　surely　not　hesitate　to　admit　that　what　the　geometer　propounds　as　a　theorem　they　have　always　perceived　to　be　the　fact；　and；　consequently；　although　it　be　not　necessarily　true；　yet　they　would　permit　us　to　expect　it　to　be　true　in　the　future。　In　this　manner　Hume's　empiricism　leads　inevitably　to　scepticism；　even　with　regard　to　mathematics；　and　consequently　in　every　scientific　theoretical　use　of　reason　（for　this　belongs　either　to　philosophy　or　mathematics）。　Whether　with　such　a　terrible　overthrow　of　the　chief　branches　of　knowledge；　common　reason　will　escape　better；　and　will　not　rather　become　irrecoverably　involved　in　this　destruction　of　all　knowledge；　so　that　from　the　same　principles　a　universal　scepticism　should　follow　（affecting；　indeed；　only　the　learned）；　this　I　will　leave　everyone　to　judge　for　himself。　　　As　regards　my　own　labours　in　the　critical　examination　of　pure　reason；　which　were　occasioned　by　Hume's　sceptical　teaching；　but　went　much　further　and　embraced　the　whole　field　of　pure　theoretical　reason　in　its　synthetic　use　and；　consequently；　the　field　of　what　is　called　metaphysics　in　general；　I　proceeded　in　the　following　manner　with　respect　to　the　doubts　raised　by　the　Scottish　philosopher　touching　the　notion　of　causality。　If　Hume　took　the　objects　of　experience　for　things　in　themselves　（as　is　almost　always　done）；　he　was　quite　right　in　declaring　the　notion　of　cause　to　be　a　deception　and　false　illusion；　for　as　to　things　in　themselves；　and　their　attributes　as　such；　it　is　impossible　to　see　why　because　A　is　given；　B；　which　is　different；　must　necessarily　be　also　given；　and　therefore　he　could　by　no　means　admit　such　an　a　priori　knowledge　of　things　in　themselves。　Still　less　could　this　acute　writer　allow　an　empirical　origin　of　this　concept；　since　this　is　directly　contradictory　to　the　necessity　of　connection　which　constitutes　the　essence　of　the　notion　of　causality；　hence　the　notion　was　proscribed；　and　in　its　place　was　put　custom　in　the　observation　of　the　course　of　perceptions。　　　It　resulted；　however；　from　my　inquiries；　that　the　objects　with　which　we　have　to　do　in　experience　are　by　no　means　things　in　themselves；　but　merely　phenomena；　and　that　although　in　the　case　of　things　in　themselves　it　is　impossible　to　see　how；　if　A　is　supposed；　it　should　be　contradictory　that　B；　which　is　quite　different　from　A；　should　not　also　be　supposed　（i。e。；　to　see　the　necessity　of　the　connection　between　A　as　cause　and　B　as　effect）；　yet　it　can　very　well　be　conceived　that；　as　phenomena；　they　may　be　necessarily　connected　in　one　experience　in　a　certain　way　（e。g。；　with　regard　to　time…relations）；　so　that　they　could　not　be　separated　without　contradicting　that　connection；　by　means　of　which　this　experience　is　possible　in　which　they　are　objects　and　in　which　alone　they　are　cognisable　by　us。　And　so　it　was　found　to　be　in　fact；　so　that　I　was　able　not　only　to　prove　the　objective　reality　of　the　concept　of　cause　in　regard　to　objects　of　experience；　but　also　to　deduce　it　as　an　a　priori　concept　by　reason　of　the　necessity　of　the　connection　it　implied；　that　is；　to　show　the　possibility　of　its　origin　from　pure　understanding　without　any　empirical　sources；　and　thus；　after　removing　the　source　of　empiricism；　I　was　able　also　to　overthrow　the　inevitable　consequence　of　this；　namely；　scepticism；　first　with　regard　to　physical　science；　and　then　with　regard　to　mathematics　（in　which　empiricism　has　just　the　same　grounds）；　both　being　sciences　which　have　reference　to　objects　of　possible　experience；　herewith　overthrowing　the　thorough　doubt　of　whatever　theoretic　reason　professes　to　discern。　　　But　how　is　it　with　the　application　of　this　category　of　causality　（and　all　the　others；　for　without　them　there　can　be　no　knowledge　of　anything　existing）　to　things　which　are　not　objects　of　possible　experience；　but　lie　beyond　its　bounds？　For　I　was　able　to　deduce　the　objective　reality　of　these　concepts　only　with　regard　to　objects　of　possible　experience。　But　even　this　very　fact；　that　I　have　saved　them；　only　in　case　I　have　proved　that　objects　may　by　means　of　them　be　thought；　though　not　determined　a　priori；　this　it　is　that　gives　them　a　place　in　the　pure　understanding；　by　which　they　are　referred　to　objects　in　general　（sensible　or　not　sensible）。　If　anything　is　still　wanting；　it　is　that　which　is　the　condition　of　the　application　of　these　categories；　and　especially　that　of　causality；　to　objects；　namely；　intuition；　for　where　this　is　not　given；　the　application　with　a　view　to　theoretic　knowledge　of　the　object；　as　a　noumenon；　is　impossible　and；　therefore；　if　anyone　ventures　on　it；　is　（as　in　the　Critique　of　Pure　Reason）　absolutely　forbidden。　Still；　the　objective　reality　of　the　concept　（of　causality）　remains；　and　it　can　be　used　even　of　noumena；　but　without　our　being　able　in　the　least　to　define　the　concept　theoretically　so　as　to　produce　knowledge。　For　that　this　concept；　even　in　reference　to　an　object；　contains　nothing　impossible；　was　shown　by　this；　that；　even　while　applied　to　objects　of　sense；　its　seat　was　certainly　fixed　in　the　pure　understanding；　and　although；　when　referred　to　things　in　themselves　（which　cannot　be　objects　of　experience）；　it　is　not　capable　of　being　determined　so　as　to　represent　a　definite　object　for　the　purpose　of　theoretic　knowledge；　yet　for　any　other　purpose　（for　instance；　a　practical）　it　might　be　capable　of　being　determined　so　as　to　have　such　application。　This　could　not　be　the　case　if；　as　Hume　maintained；　this　concept　of　causality　contained　something　absolutely　impossible　to　be　thought。　　　In　order　now　to　discover　this　condition　of　the　application　of　the　said　concept　to　noumena；　we　need　only　recall　why　we　are　not　content　with　its　application　to　objects　of　experience；　but　desire　also　to　apply　it　to　things　in　themselves。　It　will　appear；　then；　that　it　is　not　a　theoretic　but　a　practical　purpose　that　makes　this　a　necessity。　In　speculation；　even　if　we　were　successful　in　it；　we　should　not　really　gain　anything　in　the　knowledge　of　nature；　or　generally　with　regard　to　such　objects　as　are　given；　but　we　should　make　a　wide　step　from　the　sensibly　conditioned　（in　which　we　have　already　enough　to　do　to　maintain　ourselves；　and　to　follow　carefully　the　chain　of　causes）　to　the　supersensible；　in　order　to　complete　our　knowledge　of　principles　and　to　fix　its　limits；　whereas　there　always　remains　an　infinite　chasm　unfilled　between　those　limits　and　what　we　know；　and　we　should　have　hearkened　to　a　vain　curiosity　rather　than　a　solid…desire　of　knowledge。　　　But；　besides　the　relation　in　which　the　understanding　stands　to　objects　（in　theoretical　knowledge）；　it　has　also　a　relation　to　the　faculty　of　desire；　which　is　therefore　called　the　will；　and　the　pure　will；　inasmuch　as　pure　understanding　（in　this　case　called　reason）　is　practical　through　the　mere　conception　of　a　law。　The　objective　reality　of　a　pure　will；　or；　what　is　the　same　thing；　of　a　pure　practical　reason；　is　given　in　the　moral　law　a　priori；　as　it　were；　by　a　fact；　for　so　we　may　name　a　determination　of　the　will　which　is　inevitable；　although　it　does　not　rest　on　empirical　principles。　Now；　in　the　notion　of　a　will　the　notion　of　causality　is　already　contained；　and　hence　the　notion　of　a　pure　will　contains　that　of　a　causality　accompanied　with　freedom；　that　is；　one　which　is　not　determinable　by　physical　laws；　and　consequently　is　not　capable　of　any　empirical　intuition　in　proof　of　its　reality；　but；　nevertheless；　completely　justifies　its　objective　reality　a　priori　in　the　pure　practical　law；　not；　indeed　（as　is　easily　seen）　for　the　purposes　of　the　theoretical；　but　of　the　practical　use　of　reason。　Now　the　notion　of　a　being　that　has　free　will　is　the　notion　of　a　causa　noumenon；　and　that　this　notion　involves　no　contradiction；　we　are　already　assured　by　the　fact…　that　inasmuch　as　the　concept　of　cause　has　arisen　wholly　from　pure　understanding；　and　has　its　objective　reality　assured　by　the　deduction；　as　it　is　moreover　in　its　origin　independent　of　any　sensible　conditions；　it　is；　therefore；　not　restricted　to　phenomena　（unless　we　wanted　to　make　a　definite　theoretic　use　of　it）；　but　can　be　applied　equally　to　things　that　are　objects　of　the　pure　understanding。　But；　since　this　application　cannot　rest　on　any　intuition　（for　intuition　can　only　be　sensible）；　therefore；　causa　noumenon；　as　regards　the　theoretic　use　of　reason；　although　a　possible　and　thinkable；　is　yet　an　empty　notion。　Now；　I　do　n