what　is　externally　his；　from　any　other　possessor　of　them；　and　he　is
  entitled　to　fetch　them　back　to　his　house；　even　before　the　reasons　that
  may　have　led　them　to　run　away；　and　their　particular　right　in　the
  circumstances；　have　been　juridically　investigated。
  SYSTEMATIC　DIVISION　OF　ALL　THE　RIGHTS　CAPABLE　OF
  BEING　ACQUIRED　BY　CONTRACT。
  31。　Division　of　Contracts　Juridical　Conceptions
  of　Money　and　a　Book。
  It　is　reasonable　to　demand　that　a　metaphysical　science　of　right
  shall　completely　and　definitely　determine　the　members　of　a　logical
  division　of　its　conceptions　a　priori；　and　thus　establish　them　in　a
  genuine　system。　All　empirical　division；　on　the　other　hand；　is　merely
  fragmentary　partition；　and　it　leaves　us　in　uncertainty　as　to　whether
  there　may　not　be　more　members　still　required　to　complete　the　whole
  sphere　of　the　divided　conception。　A　division　that　is　made　according　to
  a　principle　a　priori　may　be　called；　in　contrast　to　all　empirical
  partitions；　a　dogmatic　division。
  Every　contract；　regarded　in　itself　objectively；　consists　of　two
  juridical　acts：　the　promise　and　its　acceptance。　Acquisition　by　the
  latter；　unless　it　be　a　pactum　re　initum　which　requires　delivery；　is
  not　a　part；　but　the　juridically　necessary　consequence　of　the　contract。
  Considered　again　subjectively；　or　as　to　whether　the　acquisition；　which
  ought　to　happen　as　a　necessary　consequence　according　to　reason；　will
  also　follow；　in　fact；　as　a　physical　consequence；　it　is　evident　that
  I　have　no　security　or　guarantee　that　this　will　happen　by　the　mere
  acceptance　of　a　promise。　There　is；　therefore；　something　externally
  required　connected　with　the　mode　of　the　contract；　in　reference　to
  the　certainty　of　acquisition　by　it；　and　this　can　only　be　some
  element　completing　and　determining　the　means　necessary　to　the
  attainment　of　acquisition　as　realizing　the　purpose　of　the　contract。
  And　in　his　connection　and　behoof；　three　persons　are　required　to
  intervene…　the　promiser；　the　acceptor；　and　the　cautioner　or　surety。
  The　importance　of　the　cautioner　is　evident；　but　by　his　intervention
  and　his　special　contract　with　the　promiser；　the　acceptor　gains　nothing
  in　respect　of　the　object　but　the　means　of　compulsion　that　enable　him
  to　obtain　what　is　his　own。
  According　to　these　rational　principles　of　logical　division；　there
  are　properly　only　three　pure　and　simple　modes　of　contract。　There
  are；　however；　innumerable　mixed　and　empirical　modes；　adding
  statutory　and　conventional　forms　to　the　principles　of　mine　and　thine
  that　are　in　accordance　with　rational　laws。　But　they　lie　outside　of　the
  circle　of　the　metaphysical　science　of　right；　whose　rational　modes　of
  contract　can　alone　be　indicated　here。
  All　contracts　are　founded　upon　a　purpose　of　acquisition；　and　are
  either：
  A。　Gratuitous　contracts；　with　unilateral　acquisition；　or
  B。　Onerous　contracts；　with　reciprocal　acquisition；　or
  C。　Cautionary　contracts；　with　no　acquisition；　but　only　guarantee
  of　what　has　been　already　acquired。　These　contracts　may　be　gratuitous
  on　the　one　side；　and　yet；　at　the　same　time；　onerous　on　the　other。
  A。　The　gratuitous　contracts　（pacta　gratuita）　are：
  1。　Depositation　（depositum）；　involving　the　preservation　of　some
  valuable　deposited　in　trust；
  2。　Commodate　（commodatum）　a　loan　of　the　use　of　a　thing；
  3。　Donation　（donatio）；　a　free　gift。
  B。　The　onerous　contracts　are　contracts　either　of　permutation　or　of
  hiring。
  I。　Contracts　of　permutation　or　reciprocal　exchange　（permutatio
  late　sic　dicta）：
  1。　Barter；　or　strictly　real　exchange　（permutatio　stricte　sic
  dicta）。　Goods　exchanged　for　goods。
  2。　Purchase　and　sale　（emptio　venditio）。　Goods　exchanged　for　money。
  3。　Loan　（mutuum）。　Loan　of　a　fungible　under　condition　of　its
  being　returned　in　kind：　corn　for　corn；　or　money　for　money。
  II。　Contracts　of　letting　and　hiring　（locatio　conductio）：
  1。　Letting　of　a　thing　on　hire　to　another　person　who　is　to　make　use
  of　it　（locatio　rei）。　If　the　thing　can　only　be　restored　in　specie；　it
  may　be　the　subject　of　an　onerous　contract　combining　the
  consideration　of　interest　with　it　（pactum　usurarium）。
  2。　Letting　of　work　on　hire　（locatio　operae）。　Consent　to　the　use　of
  my　powers　by　another　for　a　certain　price　（merces）。　The　worker　under
  this　contract　is　a　hired　servant　（mercenarius）。
  3。　Mandate　（mandatum）。　The　contract　of　mandate　is　an　engagement　to
  perform　or　execute　a　certain　business　in　place　and　in　name　of
  another　person。　If　the　action　is　merely　done　in　the　place　of
  another；　but　not；　at　the　same　time；　in　his　name；　it　is　performance
  without　commission　（gestio　negotii）；　but　if　it　is　rightfully　performed
  in　name　of　the　other；　it　constitutes　mandate；　which　as　a　contract　of
  procuration　is　an　onerous　contract　（mandatum　onerosum）。
  C。　The　cautionary　contracts　（cautiones）　are：
  1。　Pledge　（pignus）。　Caution　by　a　moveable　deposited　as　security。
  2。　Suretyship　（fidejussio）。　Caution　for　the　fulfillment　of　the
  promise　of　another。
  3。　Personal　security　（praestatio　obsidis）。
  Guarantee　of　personal　performance。
  This　list　of　all　modes　in　which　the　property　of　one　person　may　be
  transferred　or　conveyed　to　another　includes　conceptions　of　certain
  objects　or　instruments　required　for　such　transference　（translatio）。
  These　appear　to　be　entirely　empirical；　and　it　may　therefore　seem
  questionable　whether　they　are　entitled　to　a　place　in　a　metaphysical
  science　of　right。　For；　in　such　a　science；　the　divisions　must　be　made
  according　to　principles　a　priori；　and　hence　the　matter　of　the
  juridical　relation；　which　may　be　conventional；　ought　to　be　left　out　of
  account；　and　only　its　form　should　be　taken　into　consideration。
  Such　conceptions　may　be　illustrated　by　taking　the　instance　of　money；
  in　contradistinction　from　all　other　exchangeable　things　as　wares　and
  merchandise；　or　by　the　case　of　a　book。　And　considering　these　as
  illustrative　examples　in　this　connection；　it　will　be　shown　that　the
  conception　of　money　as　the　greatest　and　most　useable　of　all　the
  means　of　human　intercommunication　through　things；　in　the　way　of
  purchase　and　sale　in　commerce；　as　well　as　that　of　books　as　the
  greatest　means　of　carrying　on　the　interchange　of　thought；　resolve
  themselves　into　relations　that　are　purely　intellectual　and　rational。
  And　hence　it　will　be　made　evident　that　such　conceptions　do　not
  really　detract　from　the　purity　of　the　given　scheme　of　pure　rational
  contracts；　by　empirical　admixture。
  Illustration　of　Relations　of　Contract　by　the
  Conceptions　of　Money　and　a　Book
  I。　What　is　Money？
  Money　is　a　thing　which　can　only　be　made　use　of；　by　being　alienated
  or　exchanged。　This　is　a　good　nominal　definition；　as　given　by
  Achenwall；　and　it　is　sufficient　to　distinguish　objects　of　the　will
  of　this　kind　from　all　other　objects。　But　it　gives　us　no　information
  regarding　the　rational　possibility　of　such　a　thing　as　money　is。　Yet　we
  see　thus　much　by　the　definition：　（1）　that　the　alienation　in　this
  mode　of　human　intercommunication　and　exchange　is　not　viewed　as　a　gift；
  but　is　intended　as　a　mode　of　reciprocal　acquisition　by　an　onerous
  contract；　and　（2）　that　it　is　regarded　as　a　mere　means　of　carrying　on
  commerce；　universally　adopted　by　the　people；　but　having　no　value　as
  such　of　itself；　in　contrast　to　other　things　as　mercantile　goods　or
  wares　which　have　a　particular　value　in　relation　to　special　wants
  existing　among　the　people。　It　therefore　represents　all　exchangeable
  things。
  A　bushel　of　corn　has　the　greatest　direct　value　as　a　means　of
  satisfying　human　wants。　Cattle　may　be　fed　by　it；　and　these　again　are
  subservient　to　our　nourishment　and　locomotion；　and　they　even　labour　in
  our　stead。　Thus；　by　means　of　corn；　men　are　multiplied　and　supported；
  who　not　only　act　again　in　reproducing　such　natural　products；　but
  also　by　other　artificial　products　they　can　come　to　the　relief　of　all
  our　proper　wants。　Thus　are　men　enabled　to　build　dwellings；　to
  prepare　clothing；　and　to　supply　all　the　ingenious　comforts　and
  enjoyments　which　make　up　the　products　of　industry。　On　the　other
  hand；　the　value　of　money　is　only　indirect。　It　cannot　be　itself
  enjoyed；　nor　be　used　directly　for　enjoyment；　it　is；　however；　a　means
  towards　this；　and　of　all　outward　things　it　is　of　the　highest　utility。
  We　may　found　a　real　definition　of　money　provisionally　upon　these
  considerations。　It　may　thus　be　defined　as　the　universal　means　of
  carrying　on　the　industry　of　men　in　exchanging　intercommunications　with
  each　other。　Hence　national　wealth；　in　so　far　as　it　can　be　acquired
  by　means　of　money；　is　properly　only　the　sum　of　the　industry　or　applied
  labour　with　which　men　pay　each　other；　and　which　is　represented　by
  the　money　in　circulation　among　the　people。
  The　thing　which　is　to　be　called　money　must；　therefore；　have　cost
  as　much　industry　to　produce　it；　or　even　to　put　it　into　the　hands　of
  others；　as　may　be　equivalent