on the heavens-第13部分

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e　action　and　of　one　kind　only。　For　either　they　have　but　one　attainable　good　（as　indeed　man　has）；　or；　if　several；　each　contributes　directly　to　their　ultimate　good。　One　thing　then　has　and　enjoys　the　ultimate　good；　other　things　attain　to　it；　one　immediately　by　few　steps；　another　by　many；　while　yet　another　does　not　even　attempt　to　secure　it　but　is　satisfied　to　reach　a　point　not　far　removed　from　that　consummation。　Thus；　taking　health　as　the　end；　there　will　be　one　thing　that　always　possesses　health；　others　that　attain　it；　one　by　reducing　flesh；　another　by　running　and　thus　reducing　flesh；　another　by　taking　steps　to　enable　himself　to　run；　thus　further　increasing　the　number　of　movements；　while　another　cannot　attain　health　itself；　but　only　running　or　reduction　of　flesh；　so　that　one　or　other　of　these　is　for　such　a　being　the　end。　For　while　it　is　clearly　best　for　any　being　to　attain　the　real　end；　yet；　if　that　cannot　be；　the　nearer　it　is　to　the　best　the　better　will　be　its　state。　It　is　for　this　reason　that　the　earth　moves　not　at　all　and　the　bodies　near　to　it　with　few　movements。　For　they　do　not　attain　the　final　end；　but　only　come　as　near　to　it　as　their　share　in　the　divine　principle　permits。　But　the　first　heaven　finds　it　immediately　with　a　single　movement；　and　the　bodies　intermediate　between　the　first　and　last　heavens　attain　it　indeed；　but　at　the　cost　of　a　multiplicity　of　movement。　　　As　to　the　difficulty　that　into　the　one　primary　motion　is　crowded　a　vast　multitude　of　stars；　while　of　the　other　stars　each　has　been　separately　given　special　movements　of　its　own；　there　is　in　the　first　place　this　reason　for　regarding　the　arrangement　as　a　natural　one。　In　thinking　of　the　life　and　moving　principle　of　the　several　heavens　one　must　regard　the　first　as　far　superior　to　the　others。　Such　a　superiority　would　be　reasonable。　For　this　single　first　motion　has　to　move　many　of　the　divine　bodies；　while　the　numerous　other　motions　move　only　one　each；　since　each　single　planet　moves　with　a　variety　of　motions。　Thus；　then；　nature　makes　matters　equal　and　establishes　a　certain　order；　giving　to　the　single　motion　many　bodies　and　to　the　single　body　many　motions。　And　there　is　a　second　reason　why　the　other　motions　have　each　only　one　body；　in　that　each　of　them　except　the　last；　i。e。　that　which　contains　the　one　star；　is　really　moving　many　bodies。　For　this　last　sphere　moves　with　many　others；　to　which　it　is　fixed；　each　sphere　being　actually　a　body；　so　that　its　movement　will　be　a　joint　product。　Each　sphere；　in　fact；　has　its　particular　natural　motion；　to　which　the　general　movement　is；　as　it　were；　added。　But　the　force　of　any　limited　body　is　only　adequate　to　moving　a　limited　body。　　　The　characteristics　of　the　stars　which　move　with　a　circular　motion；　in　respect　of　substance　and　shape；　movement　and　order；　have　now　been　sufficiently　explained。

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　　It　remains　to　speak　of　the　earth；　of　its　position；　of　the　question　whether　it　is　at　rest　or　in　motion；　and　of　its　shape。　　　I。　As　to　its　position　there　is　some　difference　of　opinion。　Most　people…all；　in　fact；　who　regard　the　whole　heaven　as　finite…say　it　lies　at　the　centre。　But　the　Italian　philosophers　known　as　Pythagoreans　take　the　contrary　view。　At　the　centre；　they　say；　is　fire；　and　the　earth　is　one　of　the　stars；　creating　night　and　day　by　its　circular　motion　about　the　centre。　They　further　construct　another　earth　in　opposition　to　ours　to　which　they　give　the　name　counterearth。　In　all　this　they　are　not　seeking　for　theories　and　causes　to　account　for　observed　facts；　but　rather　forcing　their　observations　and　trying　to　accommodate　them　to　certain　theories　and　opinions　of　their　own。　But　there　are　many　others　who　would　agree　that　it　is　wrong　to　give　the　earth　the　central　position；　looking　for　confirmation　rather　to　theory　than　to　the　facts　of　observation。　Their　view　is　that　the　most　precious　place　befits　the　most　precious　thing：　but　fire；　they　say；　is　more　precious　than　earth；　and　the　limit　than　the　intermediate；　and　the　circumference　and　the　centre　are　limits。　Reasoning　on　this　basis　they　take　the　view　that　it　is　not　earth　that　lies　at　the　centre　of　the　sphere；　but　rather　fire。　The　Pythagoreans　have　a　further　reason。　They　hold　that　the　most　important　part　of　the　world；　which　is　the　centre；　should　be　most　strictly　guarded；　and　name　it；　or　rather　the　fire　which　occupies　that　place；　the　'Guardhouse　of　Zeus'；　as　if　the　word　'centre'　were　quite　unequivocal；　and　the　centre　of　the　mathematical　figure　were　always　the　same　with　that　of　the　thing　or　the　natural　centre。　But　it　is　better　to　conceive　of　the　case　of　the　whole　heaven　as　analogous　to　that　of　animals；　in　which　the　centre　of　the　animal　and　that　of　the　body　are　different。　For　this　reason　they　have　no　need　to　be　so　disturbed　about　the　world；　or　to　call　in　a　guard　for　its　centre：　rather　let　them　look　for　the　centre　in　the　other　sense　and　tell　us　what　it　is　like　and　where　nature　has　set　it。　That　centre　will　be　something　primary　and　precious；　but　to　the　mere　position　we　should　give　the　last　place　rather　than　the　first。　For　the　middle　is　what　is　defined；　and　what　defines　it　is　the　limit；　and　that　which　contains　or　limits　is　more　precious　than　that　which　is　limited；　see　ing　that　the　latter　is　the　matter　and　the　former　the　essence　of　the　system。　　　II。　As　to　the　position　of　the　earth；　then；　this　is　the　view　which　some　advance；　and　the　views　advanced　concerning　its　rest　or　motion　are　similar。　For　here　too　there　is　no　general　agreement。　All　who　deny　that　the　earth　lies　at　the　centre　think　that　it　revolves　about　the　centre；　and　not　the　earth　only　but；　as　we　said　before；　the　counter…earth　as　well。　Some　of　them　even　consider　it　possible　that　there　are　several　bodies　so　moving；　which　are　invisible　to　us　owing　to　the　interposition　of　the　earth。　This；　they　say；　accounts　for　the　fact　that　eclipses　of　the　moon　are　more　frequent　than　eclipses　of　the　sun：　for　in　addition　to　the　earth　each　of　these　moving　bodies　can　obstruct　it。　Indeed；　as　in　any　case　the　surface　of　the　earth　is　not　actually　a　centre　but　distant　from　it　a　full　hemisphere；　there　is　no　more　difficulty；　they　think；　in　accounting　for　the　observed　facts　on　their　view　that　we　do　not　dwell　at　the　centre；　than　on　the　common　view　that　the　earth　is　in　the　middle。　Even　as　it　is；　there　is　nothing　in　the　observations　to　suggest　that　we　are　removed　from　the　centre　by　half　the　diameter　of　the　earth。　Others；　again；　say　that　the　earth；　which　lies　at　the　centre；　is　'rolled'；　and　thus　in　motion；　about　the　axis　of　the　whole　heaven；　So　it　stands　written　in　the　Timaeus。　　　III。　There　are　similar　disputes　about　the　shape　of　the　earth。　Some　think　it　is　spherical；　others　that　it　is　flat　and　drum…shaped。　For　evidence　they　bring　the　fact　that；　as　the　sun　rises　and　sets；　the　part　concealed　by　the　earth　shows　a　straight　and　not　a　curved　edge；　whereas　if　the　earth　were　spherical　the　line　of　section　would　have　to　be　circular。　In　this　they　leave　out　of　account　the　great　distance　of　the　sun　from　the　earth　and　the　great　size　of　the　circumference；　which；　seen　from　a　distance　on　these　apparently　small　circles　appears　straight。　Such　an　appearance　ought　not　to　make　them　doubt　the　circular　shape　of　the　earth。　But　they　have　another　argument。　They　say　that　because　it　is　at　rest；　the　earth　must　necessarily　have　this　shape。　For　there　are　many　different　ways　in　which　the　movement　or　rest　of　the　earth　has　been　conceived。　　　The　difficulty　must　have　occurred　to　every　one。　It　would　indeed　be　a　complacent　mind　that　felt　no　surprise　that；　while　a　little　bit　of　earth；　let　loose　in　mid…air　moves　and　will　not　stay　still；　and　more　there　is　of　it　the　faster　it　moves；　the　whole　earth；　free　in　midair；　should　show　no　movement　at　all。　Yet　here　is　this　great　weight　of　earth；　and　it　is　at　rest。　And　again；　from　beneath　one　of　these　moving　fragments　of　earth；　before　it　falls；　take　away　the　earth；　and　it　will　continue　its　downward　movement　with　nothing　to　stop　it。　The　difficulty　then；　has　naturally　passed　into　a　common　place　of　philosophy；　and　one　may　well　wonder　that　the　solutions　offered　are　not　seen　to　involve　greater　absurdities　than　the　problem　itself。　　　By　these　considerations　some　have　been　led　to　assert　that　the　earth　below　us　is　infinite；　saying；　with　Xenophanes　of　Colophon；　that　it　has　'pushed　its　roots　to　infinity'；…in　order　to　save　the　trouble　of　seeking　for　the　cause。　Hence　the　sharp　rebuke　of　Empedocles；　in　the　words　'if　the　deeps　of　the　earth　are　endless　and　endless　the　ample　ether…such　is　the　vain　tale　told　by　many　a　tongue；　poured　from　the　mouths　of　those　who　have　seen　but　little　of　the　whole。　Others　say　the　earth　rests　upon　water。　This；　indeed；　is　the　oldest　theory　that　has　been　preserved；　and　is　attributed　to　Thales　of　Miletus。　It　was　supposed　to　stay　still　because　it　floated　like　wood　and　other　similar　substances；　which　are　so　constituted　as　to　rest　upon　but　not　upon　air。　As　if　the　same　account　had　not　to　be　given　of　the　water　which　carries　the　earth　as　of　the　earth　itself！　It　is　not　the　nature　of　water；　any　more　than　of　earth；　to　stay　in　mid…air：　it　must　have　something　to　rest　upon。　Again；　as　air　is　lighter　than　water；　so　is　water　than　earth：　how　then　can　they　think　that　the　naturally　lighter　substance　lies　below　the　heavier？　Again；　if　the　earth　as　a　whole　is　capable　of　floating　upon　water；　that　must　obviously　be　the　case　with　any　part　of　it。　But　observation　shows　that　this　is　not　the　case。　Any　piece　of　earth　goes　to　the　bottom；　the　quicker　the　larger　it　is。　These　thinkers　seem　to　push　their　inquiries　some　way　into　the　problem；　but　not　so　far　as　they　might。　It　is　what　we　are　all　inclined　to　do；　to　direct　our　inquiry　not　by　the　matter　itself；　but　by　the　views　of　our　opponents：　and　even　when　interrogating　oneself　one　pushes　the　inquiry　only　to　the　point　at　which　one　can　no　longer　offer　any　opposition。　Hence　a　good　inquirer　will　be　one　who　is　ready　in　bringing　forward　the　objections　proper　to　the　genus；　and　that　he　will　be　when　he　has　gained　an　understanding　of　all　the　differences。　　　Anaximenes　and　Anaxagoras　and　Democritus　give　the　flatness　of　the　earth　as　the　cause　of　its　staying　still。　Thus；　they　say；　it　does　not　cut；　but　covers　like　a　lid；　the　air　beneath　it。　This　seems　to　be　the　way　of　flat…shaped　bodies：　for　even　the　wind　can　scarcely　move　them　because　of　their　power　of　resistanc