so。　It　is；　however；　absolutely　impossible　to　give　any　further　proof　of
  the　categorical　imperative　implied；　just　as　it　is　impossible　for　the
  geometrician　to　prove　by　rational　syllogisms　that　in　order　to
  construct　a　triangle　I　must　take　three　lines…　so　far　an　analytical
  proposition…　of　which　three　lines　any　two　together　must　be　greater
  than　the　third…　a　synthetical　proposition；　and　like　the　former　a
  priori。　It　is　a　postulate　of　the　pure　reason　that　we　ought　to　abstract
  from　all　the　sensible　conditions　of　space　and　time　in　reference　to　the
  conception　of　right；　and　the　theory　of　the　possibility　of　such
  abstraction　from　these　conditions；　without　taking　away　the　reality
  of　the　possession；　just　constitutes　the　transcendental　deduction　of
  the　conception　of　acquisition　by　contract。　It　is　quite　akin　to　what
  was　presented　under　the　last　title；　as　the　theory　of　acquisition　by
  occupation　of　the　external　object。
  20。　What　is　Acquired　by　Contract。
  But　what　is　that；　designated　as　external；　which　I　acquire　by
  contract？　As　it　is　only　the　causality　of　the　active　will　of　another；
  in　respect　of　the　performance　of　something　promised　to　me；　I　do　not
  immediately　acquire　thereby　an　external　thing；　but　an　act　of　the
  will　in　question；　whereby　a　thing　is　brought　under　my　power　so　that
  I　make　it　mine。　By　the　contract；　therefore；　I　acquire　the　promise　of
  another；　as　distinguished　from　the　thing　promised；　and　yet　something
  is　thereby　added　to　my　having　and　possession。　I　have　become　the　richer
  in　possession　（locupletior）　by　the　acquisition　of　an　active　obligation
  that　I　can　bring　to　bear　upon　the　freedom　and　capability　of　another。
  This　my　right；　however；　is　only　a　personal　right；　valid　only　to　the
  effect　of　acting　upon　a　particular　physical　person　and　specially
  upon　the　causality　of　his　will；　so　that　he　shall　perform　something　for
  me。　It　is　not　a　real　right　upon　that　moral　person；　which　is　identified
  with　the　idea　of　the　united　will　of　all　viewed　a　priori；　and　through
  which　alone　I　can　acquire　a　right　valid　against　every　possessor　of　the
  thing。　For；　it　is　in　this　that　all　right　in　a　thing　consists。
  The　transfer　or　transmission　of　what　is　mine　to　another　by　contract；
  takes　place　according　to　the　law　of　continuity　（lex　continui）。
  Possession　of　the　object　is　not　interrupted　for　a　moment　during　this
  act；　for；　otherwise；　I　would　acquire　an　object　in　this　state　as　a
  thing　that　had　no　possessor；　and　it　would　thus　be　acquired　originally；
  which　is　contrary　to　the　idea　of　a　contract。　This　continuity；　however；
  implies　that　it　is　not　the　particular　will　of　either　the　promiser　or
  the　acceptor；　but　their　united　will　in　common；　that　transfers　what
  is　mine　to　another。　And　hence　it　is　not　accomplished　in　such　a
  manner　that　the　promiser　first　relinquishes　（derelinquit）　his
  possession　for　the　benefit　of　another；　or　renounces　his　right
  （renunciat）；　and　thereupon　the　other　at　the　same　time　enters　upon
  it；　or　conversely。　The　transfer　（translatio）　is　therefore　an　act　in
  which　the　object　belongs　for　a　moment　at　the　same　time　to　both；　just
  as　in　the　parabolic　path　of　a　projectile　the　object　on　reaching　its
  highest　point　may　be　regarded　for　a　moment　as　at　the　same　time　both
  rising　and　falling；　and　as　thus　passing　in　fact　from　the　ascending
  to　the　falling　motion。
  21。　Acceptance　and　Delivery。
  A　thing　is　not　acquired　in　a　case　of　contract　by　the　acceptance
  （acceptatio）　of　the　promise；　but　only　by　the　delivery　（traditio）　of
  the　object　promised。　For　all　promise　is　relative　to　performance；　and
  if　what　was　promised　is　a　thing；　the　performance　cannot　be　executed
  otherwise　than　by　an　act　whereby　the　acceptor　is　put　by　the　promiser
  into　possession　of　the　thing；　and　this　is　delivery。　Before　the
  delivery　and　the　reception　of　the　thing；　the　performance　of　the　act
  required　has　not　yet　taken　place；　the　thing　has　not　yet　passed　from
  the　one　person　to　the　other　and；　consequently；　has　not　been　acquired
  by　that　other。　Hence　the　right　arising　from　a　contract　is　only　a
  personal　right；　and　it　only　becomes　a　real　right　by　delivery。
  A　contract　upon　which　delivery　immediately　follows　（pactum　re
  initum）　excludes　any　interval　of　time　between　its　conclusion　and　its
  execution；　and　as　such　it　requires　no　further　particular　act　in　the
  future　by　which　one　person　may　transfer　to　another　what　is　his。　But　if
  there　is　a　time…　definite　or　indefinite…　agreed　upon　between　them
  for　the　delivery；　the　question　then　arises　whether　the　thing　has
  already　before　that　time　become　the　acceptor's　by　the　contract；　so
  that　his　right　is　a　right　in　the　thing；　or　whether　a　further　special
  contract　regarding　the　delivery　alone　must　be　entered　upon；　so　that
  the　right　that　is　acquired　by　mere　acceptance　is　only　a　personal
  right；　and　thus　it　does　not　become　a　right　in　the　thing　until
  delivery？　That　the　relation　must　be　determined　according　to　the　latter
  alternative　will　be　clear　from　what　follows。
  Suppose　I　conclude　a　contract　about　a　thing　that　I　wish　to
  acquire…　such　as　a　horse…　and　that　I　take　it　immediately　into　my
  stable；　or　otherwise　into　my　possession；　then　it　is　mine　（vi　pacti
  re　initi）；　and　my　right　is　a　right　in　the　thing。　But　if　I　leave　it
  in　the　hands　of　the　seller　without　arranging　with　him　specially　in
  whose　physical　possession　or　holding　（detentio）　this　thing　shall　be
  before　my　taking　possession　of　it　（apprehensio）；　and　consequently；
  before　the　actual　change　of　possession；　the　horse　is　not　yet　mine；　and
  the　right　which　I　acquire　is　only　a　right　against　a　particular　person…
  namely；　the　seller　of　the　horse…　to　be　put　into　possession　of　the
  object　（poscendi　traditionem）　as　the　subjective　condition　of　any　use
  of　it　at　my　will。　My　right　is　thus　only　a　personal　right　to　demand
  from　the　seller　the　performance　of　his　promise　（praestatio）　to　put
  me　into　possession　of　the　thing。　Now；　if　the　contract　does　not　contain
  the　condition　of　delivery　at　the　same　time…　as　a　pactum　re　initum…　and
  consequently　an　interval　of　time　intervenes　between　the　conclusion
  of　the　contract　and　the　taking　possession　of　the　object　of
  acquisition；　I　cannot　obtain　possession　of　it　during　this　interval
  otherwise　than　by　exercising　the　particular　juridical　activity
  called　a　possessory　act　（actum　possessorium）；　which　constitutes　a
  special　contract。　This　act　consists　in　my　saying；　〃I　will　send　to
  fetch　the　horse；〃　to　which　the　seller　has　to　agree。　For　it　is　not
  self…evident　or　universally　reasonable　that　any　one　will　take　a
  thing　destined　for　the　use　of　another　into　his　charge　at　his　own　risk。
  On　the　contrary；　a　special　contract　is　necessary　for　this　arrangement；
  according　to　which　the　alienator　of　a　thing　continues　to　be　its
  owner　during　a　certain　definite　time；　and　must　bear　the　risk　of
  whatever　may　happen　to　it；　while　the　acquirer　can　only　be　regarded
  by　the　seller　as　the　owner　when　he　has　delayed　to　enter　into
  possession　beyond　the　date　at　which　he　agreed　to　take　delivery。
  Prior　to　the　possessory　act；　therefore；　all　that　is　acquired　by　the
  contract　is　only　a　personal　right；　and　the　acceptor　can　acquire　an
  external　thing　only　by　delivery。
  SECTION　III。　Principles　of　Personal　Right　that　is　Real
  in　Kind。　（Jus　Realiter　Personale）。
  22。　Nature　of　Personal　Right　of　a　Real　Kind。
  Personal　right　of　a　real　kind　is　the　right　to　the　possession　of　an
  external　object　as　a　thing；　and　to　the　use　of　it　as　a　person。　The　mine
  and　thine　embraced　under　this　right　relate　specially　to　the　family　and
  household；　and　the　relations　involved　are　those　of　free　beings　in
  reciprocal　real　interaction　with　each　other。　Through　their　relations
  and　influence　as　persons　upon　one　another；　in　accordance　with　the
  principle　of　external　freedom　as　the　cause　of　it；　they　form　a
  society　composed　as　a　whole　of　members　standing　in　community　with　each
  other　as　persons；　and　this　constitutes　the　household。　The　mode　in
  which　this　social　status　is　acquired　by　individuals；　and　the　functions
  which　prevail　within　it；　proceed　neither　by　arbitrary　individual
  action　（facto）；　nor　by　mere　contract　（pacto）；　but　by　law　（lege）。　And
  this　law　as　being　not　only　a　right；　but　also　as　constituting
  possession　in　reference　to　a　person；　is　a　right　rising　above　all
  mere　real　and　personal　right。　It　must；　in　fact；　form　the　right　of
  humanity　in　our　own　person；　and；　as　such；　it　has　as　its　consequence
  a　natural　permissive　law；　by　the　favour　of　which　such　acquisition
  becomes　possible　to　us。
  23。　What　is　acquired　in　the　household。
  The　acquisition　that　is　founded　upon　this　law　is；　as　regards　its
  objects；　threefold。　The　man　acquires　a　wife；　the　husband　and　wife
  acquire　children；　constituting　a　family；　and　the　family　acquire
  domestics。　All　these　objects；　while　acquirable；　are　inalienable；　and
  the　right　of　possession　in　these　objects　is　the　most　strictly　personal
  of　all　rights。
  The　Rights　of　the　Family　as　a　Domestic　Soc