on the motion of animals-第2章

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not　initiate　movement。　Therefore　the　force　of　the　earth　in　its



immobility　will　have　to　be　as　great　as　the　force　of　the　whole　heavens；



and　of　that　which　moves　the　heavens。　But　if　that　is　impossible；　it



follows　that　the　heavens　cannot　possibly　be　moved　by　any　force　of　this



kind　inside　them。



　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　4







　　There　is　a　further　difficulty　about　the　motions　of　the　parts　of



the　heavens　which；　as　akin　to　what　has　gone　before；　may　be



considered　next。　For　if　one　could　overcome　by　force　of　motion　the



immobility　of　the　earth　he　would　clearly　move　it　away　from　the　centre。



And　it　is　plain　that　the　power　from　which　this　force　would　originate



will　not　be　infinite；　for　the　earth　is　not　infinite　and　therefore



its　weight　is　not。　Now　there　are　more　senses　than　one　of　the　word



'impossible'。　When　we　say　it　is　impossible　to　see　a　sound；　and　when　we



say　it　is　impossible　to　see　the　men　in　the　moon；　we　use　two　senses



of　the　word；　the　former　is　of　necessity；　the　latter；　though　their



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　ne