ion。　For　we　should　expect；　since　the　primary　body　shows　one　motion　only；　that　the　body　which　is　nearest　to　it　should　move　with　the　fewest　movements；　say　two；　and　the　one　next　after　that　with　three；　or　some　similar　arrangement。　But　the　opposite　is　the　case。　The　movements　of　the　sun　and　moon　are　fewer　than　those　of　some　of　the　planets。　Yet　these　planets　are　farther　from　the　centre　and　thus　nearer　to　the　primary　body　than　they；　as　observation　has　itself　revealed。　For　we　have　seen　the　moon；　half…full；　pass　beneath　the　planet　Mars；　which　vanished　on　its　shadow　side　and　came　forth　by　the　bright　and　shining　part。　Similar　accounts　of　other　stars　are　given　by　the　Egyptians　and　Babylonians；　whose　observations　have　been　kept　for　very　many　years　past；　and　from　whom　much　of　our　evidence　about　particular　stars　is　derived。　A　second　difficulty　which　may　with　equal　justice　be　raised　is　this。　Why　is　it　that　the　primary　motion　includes　such　a　multitude　of　stars　that　their　whole　array　seems　to　defy　counting；　while　of　the　other　stars　each　one　is　separated　off；　and　in　no　case　do　we　find　two　or　more　attached　to　the　same　motion？　　　On　these　questions；　I　say；　it　is　well　that　we　should　seek　to　increase　our　understanding；　though　we　have　but　little　to　go　upon；　and　are　placed　at　so　great　a　distance　from　the　facts　in　question。　Nevertheless　there　are　certain　principles　on　which　if　we　base　our　consideration　we　shall　not　find　this　difficulty　by　any　means　insoluble。　We　may　object　that　we　have　been　thinking　of　the　stars　as　mere　bodies；　and　as　units　with　a　serial　order　indeed　but　entirely　inanimate；　but　should　rather　conceive　them　as　enjoying　life　and　action。　On　this　view　the　facts　cease　to　appear　surprising。　For　it　is　natural　that　the　best…conditioned　of　all　things　should　have　its　good　without　action；　that　which　is　nearest　to　it　should　achieve　it　by　little　and　simple　action；　and　that　which　is　farther　removed　by　a　complexity　of　actions；　just　as　with　men's　bodies　one　is　in　good　condition　without　exercise　at　all；　another　after　a　short　walk；　while　another　requires　running　and　wrestling　and　hard　training；　and　there　are　yet　others　who　however　hard　they　worked　themselves　could　never　secure　this　good；　but　only　some　substitute　for　it。　To　succeed　often　or　in　many　things　is　difficult。　For　instance；　to　throw　ten　thousand　Coan　throws　with　the　dice　would　be　impossible；　but　to　throw　one　or　two　is　comparatively　easy。　In　action；　again；　when　A　has　to　be　done　to　get　B；　B　to　get　C；　and　C　to　get　D；　one　step　or　two　present　little　difficulty；　but　as　the　series　extends　the　difficulty　grows。　We　must；　then；　think　of　the　action　of　the　lower　stars　as　similar　to　that　of　animals　and　plants。　For　on　our　earth　it　is　man　that　has　the　greatest　variety　of　actions…for　there　are　many　goods　that　man　can　secure；　hence　his　actions　are　various　and　directed　to　ends　beyond　them…while　the　perfectly　conditioned　has　no　need　of　action；　since　it　is　itself　the　end；　and　action　always　requires　two　terms；　end　and　means。　The　lower　animals　have　less　variety　of　action　than　man；　and　plants　perhaps　have　little　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。
  13
  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　th