these　to　be　the　same　as　those　that　govern　their　appearances。
  The　subjective　impossibility　of　explaining　the　freedom　of　the　will
  is　identical　with　the　impossibility　of　discovering　and　explaining　an
  interest*　which　man　can　take　in　the　moral　law。　Nevertheless　he　does
  actually　take　an　interest　in　it；　the　basis　of　which　in　us　we　call
  the　moral　feeling；　which　some　have　falsely　assigned　as　the　standard　of
  our　moral　judgement；　whereas　it　must　rather　be　viewed　as　the
  subjective　effect　that　the　law　exercises　on　the　will；　the　objective
  principle　of　which　is　furnished　by　reason　alone。
  *Interest　is　that　by　which　reason　becomes　practical；　i。e。；　a　cause
  determining　the　will。　Hence　we　say　of　rational　beings　only　that　they
  take　an　interest　in　a　thing；　irrational　beings　only　feel　sensual
  appetites。　Reason　takes　a　direct　interest　in　action　then　only　when　the
  universal　validity　of　its　maxims　is　alone　sufficient　to　determine
  the　will。　Such　an　interest　alone　is　pure。　But　if　it　can　determine
  the　will　only　by　means　of　another　object　of　desire　or　on　the
  suggestion　of　a　particular　feeling　of　the　subject；　then　reason　takes
  only　an　indirect　interest　in　the　action；　and；　as　reason　by　itself
  without　experience　cannot　discover　either　objects　of　the　will　or　a
  special　feeling　actuating　it；　this　latter　interest　would　only　be
  empirical　and　not　a　pure　rational　interest。　The　logical　interest　of
  reason　（namely；　to　extend　its　insight）　is　never　direct；　but
  presupposes　purposes　for　which　reason　is　employed。
  In　order　indeed　that　a　rational　being　who　is　also　affected　through
  the　senses　should　will　what　reason　alone　directs　such　beings　that　they
  ought　to　will；　it　is　no　doubt　requisite　that　reason　should　have　a
  power　to　infuse　a　feeling　of　pleasure　or　satisfaction　in　the
  fulfilment　of　duty；　that　is　to　say；　that　it　should　have　a　causality　by
  which　it　determines　the　sensibility　according　to　its　own　principles。
  But　it　is　quite　impossible　to　discern；　i。e。；　to　make　it　intelligible　a
  priori；　how　a　mere　thought；　which　itself　contains　nothing　sensible；
  can　itself　produce　a　sensation　of　pleasure　or　pain；　for　this　is　a
  particular　kind　of　causality　of　which　as　of　every　other　causality　we
  can　determine　nothing　whatever　a　priori；　we　must　only　consult
  experience　about　it。　But　as　this　cannot　supply　us　with　any　relation　of
  cause　and　effect　except　between　two　objects　of　experience；　whereas
  in　this　case；　although　indeed　the　effect　produced　lies　within
  experience；　yet　the　cause　is　supposed　to　be　pure　reason　acting　through
  mere　ideas　which　offer　no　object　to　experience；　it　follows　that　for　us
  men　it　is　quite　impossible　to　explain　how　and　why　the　universality
  of　the　maxim　as　a　law；　that　is；　morality；　interests。　This　only　is
  certain；　that　it　is　not　because　it　interests　us　that　it　has　validity
  for　us　（for　that　would　be　heteronomy　and　dependence　of　practical
  reason　on　sensibility；　namely；　on　a　feeling　as　its　principle；　in　which
  case　it　could　never　give　moral　laws）；　but　that　it　interests　us　because
  it　is　valid　for　us　as　men；　inasmuch　as　it　had　its　source　in　our　will
  as　intelligences；　in　other　words；　in　our　proper　self；　and　what　belongs
  to　mere　appearance　is　necessarily　subordinated　by　reason　to　the　nature
  of　the　thing　in　itself。
  The　question　then；　〃How　a　categorical　imperative　is　possible；〃　can
  be　answered　to　this　extent；　that　we　can　assign　the　only　hypothesis
  on　which　it　is　possible；　namely；　the　idea　of　freedom；　and　we　can
  also　discern　the　necessity　of　this　hypothesis；　and　this　is
  sufficient　for　the　practical　exercise　of　reason；　that　is；　for　the
  conviction　of　the　validity　of　this　imperative；　and　hence　of　the
  moral　law；　but　how　this　hypothesis　itself　is　possible　can　never　be
  discerned　by　any　human　reason。　On　the　hypothesis；　however；　that　the
  will　of　an　intelligence　is　free；　its　autonomy；　as　the　essential　formal
  condition　of　its　determination；　is　a　necessary　consequence。
  Moreover；　this　freedom　of　will　is　not　merely　quite　possible　as　a
  hypothesis　（not　involving　any　contradiction　to　the　principle　of
  physical　necessity　in　the　connexion　of　the　phenomena　of　the　sensible
  world）　as　speculative　philosophy　can　show：　but　further；　a　rational
  being　who　is　conscious　of　causality　through　reason；　that　is　to　say；　of
  a　will　（distinct　from　desires）；　must　of　necessity　make　it　practically；
  that　is；　in　idea；　the　condition　of　all　his　voluntary　actions。　But　to
  explain　how　pure　reason　can　be　of　itself　practical　without　the　aid
  of　any　spring　of　action　that　could　be　derived　from　any　other　source；
  i。e。；　how　the　mere　principle　of　the　universal　validity　of　all　its
  maxims　as　laws　（which　would　certainly　be　the　form　of　a　pure
  practical　reason）　can　of　itself　supply　a　spring；　without　any　matter
  （object）　of　the　will　in　which　one　could　antecedently　take　any
  interest；　and　how　it　can　produce　an　interest　which　would　be　called
  purely　moral；　or　in　other　words；　how　pure　reason　can　be　practical…
  to　explain　this　is　beyond　the　power　of　human　reason；　and　all　the
  labour　and　pains　of　seeking　an　explanation　of　it　are　lost　an
  It　is　just　the　same　as　if　I　sought　to　find　out　how　freedom　itself　is
  possible　as　the　causality　of　a　will。　For　then　I　quit　the　ground　of
  philosophical　explanation；　and　I　have　no　other　to　go　upon。　I　might
  indeed　revel　in　the　world　of　intelligences　which　still　remains　to
  me；　but　although　I　have　an　idea　of　it　which　is　well　founded；　yet　I
  have　not　the　least　knowledge　of　it；　nor　an　I　ever　attain　to　such
  knowledge　with　all　the　efforts　of　my　natural　faculty　of　reason。　It
  signifies　only　a　something　that　remains　over　when　I　have　eliminated
  everything　belonging　to　the　world　of　sense　from　the　actuating
  principles　of　my　will；　serving　merely　to　keep　in　bounds　the
  principle　of　motives　taken　from　the　field　of　sensibility；　fixing　its
  limits　and　showing　that　it　does　not　contain　all　in　all　within
  itself；　but　that　there　is　more　beyond　it；　but　this　something　more　I
  know　no　further。　Of　pure　reason　which　frames　this　ideal；　there　remains
  after　the　abstraction　of　all　matter；　i。e。；　knowledge　of　objects；
  nothing　but　the　form；　namely；　the　practical　law　of　the　universality　of
  the　maxims；　and　in　conformity　with　this　conception　of　reason　in
  reference　to　a　pure　world　of　understanding　as　a　possible　efficient
  cause；　that　is　a　cause　determining　the　will。　There　must　here　be　a
  total　absence　of　springs；　unless　this　idea　of　an　intelligible　world　is
  itself　the　spring；　or　that　in　which　reason　primarily　takes　an
  interest；　but　to　make　this　intelligible　is　precisely　the　problem
  that　we　cannot　solve。
  Here　now　is　the　extreme　limit　of　all　moral　inquiry；　and　it　is　of
  great　importance　to　determine　it　even　on　this　account；　in　order　that
  reason　may　not　on　the　one　band；　to　the　prejudice　of　morals；　seek　about
  in　the　world　of　sense　for　the　supreme　motive　and　an　interest
  comprehensible　but　empirical；　and　on　the　other　hand；　that　it　may　not
  impotently　flap　its　wings　without　being　able　to　move　in　the　（for　it）
  empty　space　of　transcendent　concepts　which　we　call　the　intelligible
  world；　and　so　lose　itself　amidst　chimeras。　For　the　rest；　the　idea　of　a
  pure　world　of　understanding　as　a　system　of　all　intelligences；　and　to
  which　we　ourselves　as　rational　beings　belong　（although　we　are　likewise
  on　the　other　side　members　of　the　sensible　world）；　this　remains
  always　a　useful　and　legitimate　idea　for　the　purposes　of　rational
  belief；　although　all　knowledge　stops　at　its　threshold；　useful；　namely；
  to　produce　in　us　a　lively　interest　in　the　moral　law　by　means　of　the
  noble　ideal　of　a　universal　kingdom　of　ends　in　themselves　（rational
  beings）；　to　which　we　can　belong　as　members　then　only　when　we　carefully
  conduct　ourselves　according　to　the　maxims　of　freedom　as　if　they　were
  laws　of　nature。
  Concluding　Remark
  The　speculative　employment　of　reason　with　respect　to　nature　leads　to
  the　absolute　necessity　of　some　supreme　cause　of　the　world：　the
  practical　employment　of　reason　with　a　view　to　freedom　leads　also　to
  absolute　necessity；　but　only　of　the　laws　of　the　actions　of　a
  rational　being　as　such。　Now　it　is　an　essential　principle　of　reason；
  however　employed；　to　push　its　knowledge　to　a　consciousness　of　its
  necessity　（without　which　it　would　not　be　rational　knowledge）。　It　is；
  however；　an　equally　essential　restriction　of　the　same　reason　that　it
  can　neither　discern　the　necessity　of　what　is　or　what　happens；　nor　of
  what　ought　to　happen；　unless　a　condition　is　supposed　on　which　it　is　or
  happens　or　ought　to　happen。　In　this　way；　however；　by　the　constant
  inquiry　for　the　condition；　the　satisfaction　of　reason　is　only
  further　and　further　postponed。　Hence　it　unceasingly　seeks　the
  unconditionally　necessary　and　finds　itself　forced　to　assume　it；
  although　without　any　means　of　making　it　comprehensible　to　itself；
  happy　enough　if　only　it　can　discover　a　conception　which　agrees　with
  this　assumption。　It　is　therefore　no　fault　in　our　deduction　of　the
  supreme　principle　of　morality；　but　an　objection　that　should