a history of science-1-第32节

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the　multitudes；　at　whose　hands　he　suffered　death；　legally　administered　after　a　public　trial。　The　facts　at　command　as　to　certain　customs　of　the　Greeks　at　this　period　make　it　possible　to　raise　a　question　as　to　whether　the　alleged　〃corruption　of　youth；〃　with　which　Socrates　was　charged；　may　not　have　had　a　different　implication　from　what　posterity　has　preferred　to　ascribe　to　it。　But　this　thought；　almost　shocking　to　the　modern　mind　and　seeming　altogether　sacrilegious　to　most　students　of　Greek　philosophy；　need　not　here　detain　us；　neither　have　we　much　concern　in　the　present　connection　with　any　part　of　the　teaching　of　the　martyred　philosopher。　For　the　historian　of　metaphysics；　Socrates　marks　an　epoch；　but　for　the　historian　of　science　he　is　a　much　less　consequential　figure。　Similarly　regarding　Plato；　the　aristocratic　Athenian　who　sat　at　the　feet　of　Socrates；　and　through　whose　writings　the　teachings　of　the　master　found　widest　currency。　Some　students　of　philosophy　find　in　Plato　〃the　greatest　thinker　and　writer　of　all　time。〃＇1＇　The　student　of　science　must　recognize　in　him　a　thinker　whose　point　of　view　was　essentially　non…scientific；　one　who　tended　always　to　reason　from　the　general　to　the　particular　rather　than　from　the　particular　to　the　general。　Plato's　writings　covered　almost　the　entire　field　of　thought；　and　his　ideas　were　presented　with　such　literary　charm　that　successive　generations　of　readers　turned　to　them　with　unflagging　interest；　and　gave　them　wide　currency　through　copies　that　finally　preserved　them　to　our　own　time。　Thus　we　are　not　obliged　in　his　case；　as　we　are　in　the　case　of　every　other　Greek　philosopher；　to　estimate　his　teachings　largely　from　hearsay　evidence。　Plato　himself　speaks　to　us　directly。　It　is　true；　the　literary　form　which　he　always　adopted；　namely；　the　dialogue；　does　not　give　quite　the　same　certainty　as　to　when　he　is　expressing　his　own　opinions　that　a　more　direct　narrative　would　have　given；　yet；　in　the　main；　there　is　little　doubt　as　to　the　tenor　of　his　own　opinionsexcept；　indeed；　such　doubt　as　always　attaches　to　the　philosophical　reasoning　of　the　abstract　thinker。　What　is　chiefly　significant　from　our　present　standpoint　is　that　the　great　ethical　teacher　had　no　significant　message　to　give　the　world　regarding　the　physical　sciences。　He　apparently　had　no　sharply　defined　opinions　as　to　the　mechanism　of　the　universe；　no　clear　conception　as　to　the　origin　or　development　of　organic　beings；　no　tangible　ideas　as　to　the　problems　of　physics；　no　favorite　dreams　as　to　the　nature　of　matter。　Virtually　his　back　was　turned　on　this　entire　field　of　thought。　He　was　under　the　sway　of　those　innate　ideas　which；　as　we　have　urged；　were　among　the　earliest　inductions　of　science。　But　he　never　for　a　moment　suspected　such　an　origin　for　these　ideas。　He　supposed　his　conceptions　of　being；　his　standards　of　ethics；　to　lie　back　of　all　experience；　for　him　they　were　the　most　fundamental　and　most　dependable　of　facts。　He　criticised　Anaxagoras　for　having　tended　to　deduce　general　laws　from　observation。　As　we　moderns　see　it；　such　criticism　is　the　highest　possible　praise。　It　is　a　criticism　that　marks　the　distinction　between　the　scientist　who　is　also　a　philosopher　and　the　philosopher　who　has　but　a　vague　notion　of　physical　science。　Plato　seemed；　indeed；　to　realize　the　value　of　scientific　investigation；　he　referred　to　the　astronomical　studies　of　the　Egyptians　and　Chaldeans；　and　spoke　hopefully　of　the　results　that　might　accrue　were　such　studies　to　be　taken　up　by　that　Greek　mind　which；　as　he　justly　conceived；　had　the　power　to　vitalize　and　enrich　all　that　it　touched。　But　he　told　here　of　what　he　would　have　others　do；　not　of　what　he　himself　thought　of　doing。　His　voice　was　prophetic；　but　it　stimulated　no　worker　of　his　own　time。　Plato　himself　had　travelled　widely。　It　is　a　familiar　legend　that　he　lived　for　years　in　Egypt；　endeavoring　there　to　penetrate　the　mysteries　of　Egyptian　science。　It　is　said　even　that　the　rudiments　of　geometry　which　he　acquired　there　influenced　all　his　later　teachings。　But　be　that　as　it　may；　the　historian　of　science　must　recognize　in　the　founder　of　the　Academy　a　moral　teacher　and　metaphysical　dreamer　and　sociologist；　but　not；　in　the　modern　acceptance　of　the　term；　a　scientist。　Those　wider　phases　of　biological　science　which　find　their　expression　in　metaphysics；　in　ethics；　in　political　economy；　lie　without　our　present　scope；　and　for　the　development　of　those　subjects　with　which　we　are　more　directly　concerned；　Plato；　like　his　master；　has　a　negative　significance。

ARISTOTLE　（384…322　B。C。）　When　we　pass　to　that　third　great　Athenian　teacher；　Aristotle；　the　case　is　far　different。　Here　was　a　man　whose　name　was　to　be　received　as　almost　a　synonym　for　Greek　science　for　more　than　a　thousand　years　after　his　death。　All　through　the　Middle　Ages　his　writings　were　to　be　accepted　as　virtually　the　last　word　regarding　the　problems　of　nature。　We　shall　see　that　his　followers　actually　preferred　his　mandate　to　the　testimony　of　their　own　senses。　We　shall　see；　further；　that　modern　science　progressed　somewhat　in　proportion　as　it　overthrew　the　Aristotelian　dogmas。　But　the　traditions　of　seventeen　or　eighteen　centuries　are　not　easily　set　aside；　and　it　is　perhaps　not　too　much　to　say　that　the　name　of　Aristotle　stands；　even　in　our　own　time；　as　vaguely　representative　in　the　popular　mind　of　all　that　was　highest　and　best　in　the　science　of　antiquity。　Yet；　perhaps；　it　would　not　be　going　too　far　to　assert　that　something　like　a　reversal　of　this　judgment　would　be　nearer　the　truth。　Aristotle　did；　indeed；　bring　together　a　great　mass　of　facts　regarding　animals　in　his　work　on　natural　history；　which；　being　preserved；　has　been　deemed　to　entitle　its　author　to　be　called　the　〃father　of　zoology。〃　But　there　is　no　reason　to　suppose　that　any　considerable　portion　of　this　work　contained　matter　that　was　novel；　or　recorded　observations　that　were　original　with　Aristotle；　and　the　classifications　there　outlined　are　at　best　but　a　vague　foreshadowing　of　the　elaboration　of　the　science。　Such　as　it　is；　however；　the　natural　history　stands　to　the　credit　of　the　Stagirite。　He　must　be　credited；　too；　with　a　clear　enunciation　of　one　most　important　scientific　doctrinenamely；　the　doctrine　of　the　spherical　figure　of　the　earth。　We　have　already　seen　that　this　theory　originated　with　the　Pythagorean　philosophers　out　in　Italy。　We　have　seen；　too；　that　the　doctrine　had　not　made　its　way　in　Attica　in　the　time　of　Anaxagoras。　But　in　the　intervening　century　it　had　gained　wide　currency；　else　so　essentially　conservative　a　thinker　as　Aristotle　would　scarcely　have　accepted　it。　He　did　accept　it；　however；　and　gave　the　doctrine　clearest　and　most　precise　expression。　Here　are　his　words：＇2＇

〃As　to　the　figure　of　the　earth　it　must　necessarily　be　spherical。。。。　If　it　were　not　so；　the　eclipses　of　the　moon　would　not　have　such　sections　as　they　have。　For　in　the　configurations　in　the　course　of　a　month　the　deficient　part　takes　all　different　shapes；　it　is　straight；　and　concave；　and　convex；　but　in　eclipses　it　always　has　the　line　of　divisions　convex；　wherefore；　since　the　moon　is　eclipsed　in　consequence　of　the　interposition　of　the　earth；　the　periphery　of　the　earth　must　be　the　cause　of　this　by　having　a　spherical　form。　And　again；　from　the　appearance　of　the　stars　it　is　clear；　not　only　that　the　earth　is　round；　but　that　its　size　is　not　very　large；　for　when　we　make　a　small　removal　to　the　south　or　the　north；　the　circle　of　the　horizon　becomes　palpably　different；　so　that　the　stars　overhead　undergo　a　great　change；　and　are　not　the　same　to　those　that　travel　in　the　north　and　to　the　south。　For　some　stars　are　seen　in　Egypt　or　at　Cyprus；　but　are　not　seen　in　the　countries　to　the　north　of　these；　and　the　stars　that　in　the　north　are　visible　while　they　make　a　complete　circuit；　there　undergo　a　setting。　So　that　from　this　it　is　manifest；　not　only　that　the　form　of　the　earth　is　round；　but　also　that　it　is　a　part　of　a　not　very　large　sphere；　for　otherwise　the　difference　would　not　be　so　obvious　to　persons　making　so　small　a　change　of　place。　Wherefore　we　may　judge　that　those　persons　who　connect　the　region　in　the　neighborhood　of　the　pillars　of　Hercules　with　that　towards　India；　and　who　assert　that　in　this　way　the　sea　is　one；　do　not　assert　things　very　improbable。　They　confirm　this　conjecture　moreover　by　the　elephants；　which　are　said　to　be　of　the　same　species　towards　each　extreme；　as　if　this　circumstance　was　a　consequence　of　the　conjunction　of　the　extremes。　The　mathematicians　who　try　to　calculate　the　measure　of　the　circumference；　make　it　amount　to　four　hundred　thousand　stadia；　whence　we　collect　that　the　earth　is　not　only　spherical；　but　is　not　large　compared　with　the　magnitude　of　the　other　stars。〃　But　in　giving　full　meed　of　praise　to　Aristotle　for　the　promulgation　of　this　doctrine　of　the　sphericity　of　the　earth；　it　must　unfortunately　be　added　that　the　conservative　philosopher　paused　without　taking　one　other　important　step。　He　could　not　accept；　but；　on　the　contrary；　he　expressly　repudiated；　the　doctrine　of　the　earth's　motion。　We　have　seen　that　this　idea　also　was　a　part　of　the　Pythagorean　doctrine；　and　we　shall　have　occasion　to　dwell　more　at　length　on　this　point　in　a　succeeding　chapter。　It　has　even　been　contended　by　some　critics　that　it　was　the　adverse　conviction　of　the　Peripatetic　philosopher　which；　more　than　an