nature　is　to　be　seen；　cannot　as　a　fact　be　seen　by　us。　Now　we　suppose
  that　the　heavens　are　of　necessity　impossible　to　destroy　and　to
  dissolve；　whereas　the　result　of　the　present　argument　would　be　to　do
  away　with　this　necessity。　For　it　is　natural　and　possible　for　a
  motion　to　exist　greater　than　the　force　by　dint　of　which　the　earth　is
  at　rest；　or　than　that　by　dint　of　which　Fire　and　Aether　are　moved。　If
  then　there　are　superior　motions；　these　will　be　dissolved　in　succession
  by　one　another：　and　if　there　actually　are　not；　but　might　possibly　be
  （for　the　earth　cannot　be　infinite　because　no　body　can　possibly　be
  infinite）；　there　is　a　possibility　of　the　heavens　being　dissolved。
  For　what　is　to　prevent　this　coming　to　pass；　unless　it　be　impossible？
  And　it　is　not　impossible　unless　the　opposite　is　necessary。　This
  difficulty；　however；　we　will　discuss　elsewhere。
  To　resume；　must　there　be　something　immovable　and　at　rest　outside
  of　what　is　moved；　and　no　part　of　it；　or　not？　And　must　this　necessarily
  be　so　also　in　the　case　of　the　universe？　Perhaps　it　would　be　thought
  strange　were　the　origin　of　movement　inside。　And　to　those　who　so
  conceive　it　the　word　of　Homer　would　appear　to　have　been　well　spoken：
  'Nay；　ye　would　not　pull　Zeus；　highest　of　all　from　heaven　to　the
  plain；　no　not　even　if　ye　toiled　right　hard；　come；　all　ye　gods　and
  goddesses！　Set　hands　to　the　chain'；　for　that　which　is　entirely
  immovable　cannot　possibly　be　moved　by　anything。　And　herein　lies　the
  solution　of　the　difficulty　stated　some　time　back；　the　possibility　or
  impossibility　of　dissolving　the　system　of　the　heavens；　in　that　it
  depends　from　an　original　which　is　immovable。
  Now　in　the　animal　world　there　must　be　not　only　an　immovable　without；
  but　also　within　those　things　which　move　in　place；　and　initiate　their
  own　movement。　For　one　part　of　an　animal　must　be　moved；　and　another
  be　at　rest；　and　against　this　the　part　which　is　moved　will　support
  itself　and　be　moved；　for　example；　if　it　move　one　of　its　parts；　for　one
  part；　as　it　were；　supports　itself　against　another　part　at　rest。
  But　about　things　without　life　which　are　moved　one　might　ask　the
  question　whether　all　contain　in　themselves　both　that　which　is　at
  rest　and　that　which　initiates　movement；　and　whether　they　also；　for
  instance　fire；　earth；　or　any　other　inanimate　thing；　must　support
  themselves　against　something　outside　which　is　at　rest。　Or　is　this
  impossible　and　must　it　not　be　looked　for　rather　in　those　primary
  causes　by　which　they　are　set　in　motion？　For　all　things　without　life
  are　moved　by　something　other；　and　the　origin　of　all　things　so　moved
  are　things　which　move　themselves。　And　out　of　these　we　have　spoken
  about　animals　（for　they　must　all　have　in　themselves　that　which　is　at
  rest；　and　without　them　that　against　which　they　are　supported）；　but
  whether　there　is　some　higher　and　prime　mover　is　not　clear；　and　an
  origin　of　that　kind　involves　a　different　discussion。　Animals　at　any
  rate　which　move　themselves　are　all　moved　supporting　themselves　on　what
  is　outside　them；　even　when　they　inspire　and　expire；　for　there　is　no
  essential　difference　between　casting　a　great　and　a　small　weight；　and
  this　is　what　men　do　when　they　spit　and　cough　and　when　they　breathe
  in　and　breathe　out。
  5
  But　is　it　only　in　that　which　moves　itself　in　place　that　there　must
  be　a　point　at　rest；　or　does　this　hold　also　of　that　which　causes　its
  own　qualitative　changes；　and　its　own　growth？　Now　the　question　of
  original　generation　and　decay　is　different；　for　if　there　is；　as　we
  hold；　a　primary　movement；　this　would　be　the　cause　of　generation　and
  decay；　and　probably　of　all　the　secondary　movements　too。　And　as　in
  the　universe；　so　in　the　animal　world　this　is　the　primary　movement；
  when　the　creature　attains　maturity；　and　therefore　it　is　the　cause　of
  growth；　when　the　creature　becomes　the　cause　of　its　own　growth；　and　the
  cause　too　of　alteration。　But　if　this　is　not　the　primary　movement
  then　the　point　at　rest　is　not　necessary。　However；　the　earliest
  growth　and　alteration　in　the　living　creature　arise　through　another　and
  by　other　channels；　nor　can　anything　possibly　be　the　cause　of　its　own
  generation　and　decay；　for　the　mover　must　exist　before　the　moved；　the
  begetter　before　the　begotten；　and　nothing　is　prior　to　itself。
  6
  Now　whether　the　soul　is　moved　or　not；　and　how　it　is　moved　if　it　be
  moved；　has　been　stated　before　in　our　treatise　concerning　it。　And　since
  all　inorganic　things　are　moved　by　some　other　thing…　and　the　manner
  of　the　movement　of　the　first　and　eternally　moved；　and　how　the　first
  mover　moves　it；　has　been　determined　before　in　our　Metaphysics；　it
  remains　to　inquire　how　the　soul　moves　the　body；　and　what　is　the　origin
  of　movement　in　a　living　creature。　For；　if　we　except　the　movement　of
  the　universe；　things　with　life　are　the　causes　of　the　movement　of　all
  else；　that　is　of　all　that　are　not　moved　by　one　another　by　mutual
  impact。　And　so　all　their　motions　have　a　term　or　limit；　inasmuch　as　the
  movements　of　things　with　life　have　such。　For　all　living　things　both
  move　and　are　moved　with　some　object；　so　that　this　is　the　term　of　all
  their　movement；　the　end；　that　is；　in　view。　Now　we　see　that　the
  living　creature　is　moved　by　intellect；　imagination；　purpose；　wish；　and
  appetite。　And　all　these　are　reducible　to　mind　and　desire。　For　both
  imagination　and　sensation　are　on　common　ground　with　mind；　since　all
  three　are　faculties　of　judgement　though　differing　according　to
  distinctions　stated　elsewhere。　Will；　however；　impulse；　and　appetite；
  are　all　three　forms　of　desire；　while　purpose　belongs　both　to　intellect
  and　to　desire。　Therefore　the　object　of　desire　or　of　intellect　first
  initiates　movement；　not；　that　is；　every　object　of　intellect；　only
  the　end　in　the　domain　of　conduct。　Accordingly　among　goods　that　which
  moves　is　a　practical　end；　not　the　good　in　its　whole　extent。　For　it
  initiates　movement　only　so　far　as　something　else　is　for　its　sake；　or
  so　far　as　it　is　the　object　of　that　which　is　for　the　sake　of
  something　else。　And　we　must　suppose　that　a　seeming　good　may　take　the
  room　of　actual　good；　and　so　may　the　pleasant；　which　is　itself　a
  seeming　good。　From　these　considerations　it　is　clear　that　in　one　regard
  that　which　is　eternally　moved　by　the　eternal　mover　is　moved　in　the
  same　way　as　every　living　creature；　in　another　regard　differently；
  and　so　while　it　is　moved　eternally；　the　movement　of　living　creatures
  has　a　term。　Now　the　eternal　beautiful；　and　the　truly　and　primarily
  good　（which　is　not　at　one　time　good；　at　another　time　not　good）；　is　too
  divine　and　precious　to　be　relative　to　anything　else。　The　prime　mover
  then　moves；　itself　being　unmoved；　whereas　desire　and　its　faculty　are
  moved　and　so　move。　But　it　is　not　necessary　for　the　last　in　the　chain
  of　things　moved　to　move　something　else；　wherefore　it　is　plainly
  reasonable　that　motion　in　place　should　be　the　last　of　what　happens
  in　the　region　of　things　happening；　since　the　living　creature　is
  moved　and　goes　forward　by　reason　of　desire　or　purpose；　when　some
  alteration　has　been　set　going　on　the　occasion　of　sensation　or
  imagination。
  7
  But　how　is　it　that　thought　（viz。　sense；　imagination；　and　thought
  proper）　is　sometimes　followed　by　action；　sometimes　not；　sometimes　by
  movement；　sometimes　not？　What　happens　seems　parallel　to　the　case　of
  thinking　and　inferring　about　the　immovable　objects　of　science。　There
  the　end　is　the　truth　seen　（for；　when　one　conceives　the　two
  premisses；　one　at　once　conceives　and　comprehends　the　conclusion）；
  but　here　the　two　premisses　result　in　a　conclusion　which　is　an
  action…　for　example；　one　conceives　that　every　man　ought　to　walk；　one
  is　a　man　oneself：　straightway　one　walks；　or　that；　in　this　case；　no　man
  should　walk；　one　is　a　man：　straightway　one　remains　at　rest。　And　one　so
  acts　in　the　two　cases　provided　that　there　is　nothing　in　the　one　case
  to　compel　or　in　the　other　to　prevent。　Again；　I　ought　to　create　a　good；
  a　house　is　good：　straightway　I　make　a　house。　I　need　a　covering；　a　coat
  is　a　covering：　I　need　a　coat。　What　I　need　I　ought　to　make；　I　need　a
  coat：　I　make　a　coat。　And　the　conclusion　I　must　make　a　coat　is　an
  action。　And　the　action　goes　back　to　the　beginning　or　first　step。　If
  there　is　to　be　a　coat；　one　must　first　have　B；　and　if　B　then　A；　so
  one　gets　A　to　begin　with。　Now　that　the　action　is　the　conclusion　is
  clear。　But　the　premisses　of　action　are　of　two　kinds；　of　the　good　and
  of　the　possible。
  And　as　in　some　cases　of　speculative　inquiry　we　suppress　one
  premise　so　here　the　mind　does　not　stop　to　consider　at　all　an　obvious
  minor　premise；　for　example　if　walking　is　good　for　man；　one　does　not
  dwell　upon　the　minor　'I　am　a　man'。　A