a history of science-1-第21章

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out　from　among　the　traditions　of　antiquity；　aided　by　such　fragments；　of　the　writing　of　the　philosophers　as　have　come　down　to　us；　the　particular　ideas　that　characterized　each　thinker；　and　to　weave　these　ideas　into　systems。　But　such　efforts；　notwithstanding　the　mental　energy　that　has　been　expended　upon　them；　were；　of　necessity；　futile；　since；　in　the　first　place；　the　ancient　philosophers　themselves　did　not　specialize　and　systematize　their　ideas　according　to　modern　notions；　and；　in　the　second　place；　the　records　of　their　individual　teachings　have　been　too　scantily　preserved　to　serve　for　the　purpose　of　classification。　It　is　freely　admitted　that　fable　has　woven　an　impenetrable　mesh　of　contradictions　about　the　personalities　of　these　ancient　thinkers；　and　it　would　be　folly　to　hope　that　this　same　artificer　had　been　less　busy　with　their　beliefs　and　theories。　When　one　reads　that　Pythagoras　advocated　an　exclusively　vegetable　diet；　yet　that　he　was　the　first　to　train　athletes　on　meat　diet；　that　he　sacrificed　only　inanimate　things；　yet　that　he　offered　up　a　hundred　oxen　in　honor　of　his　great　discovery　regarding　the　sides　of　a　triangle；　and　such　like　inconsistencies　in　the　same　biography；　one　gains　a　realizing　sense　of　the　extent　to　which　diverse　traditions　enter　into　the　story　as　it　has　come　down　to　us。　And　yet　we　must　reflect　that　most　men　change　their　opinions　in　the　course　of　a　long　lifetime；　and　that　the　antagonistic　reports　may　both　be　true。　True　or　false；　these　fables　have　an　abiding　interest；　since　they　prove　the　unique　and　extraordinary　character　of　the　personality　about　which　they　are　woven。　The　alleged　witticisms　of　a　Whistler；　in　our　own　day；　were　doubtless；　for　the　most　part；　quite　unknown　to　Whistler　himself；　yet　they　never　would　have　been　ascribed　to　him　were　they　not　akin　to　witticisms　that　he　did　originatewere　they　not；　in　short；　typical　expressions　of　his　personality。　And　so　of　the　heroes　of　the　past。　〃It　is　no　ordinary　man；〃　said　George　Henry　Lewes；　speaking　of　Pythagoras；　〃whom　fable　exalts　into　the　poetic　region。　Whenever　you　find　romantic　or　miraculous　deeds　attributed；　be　certain　that　the　hero　was　great　enough　to　maintain　the　weight　of　the　crown　of　this　fabulous　glory。〃＇1＇　We　may　not　doubt；　then；　that　Pythagoras；　Parmenides；　and　Empedocles；　with　whose　names　fable　was　so　busy　throughout　antiquity；　were　men　of　extraordinary　personality。　We　are　here　chiefly　concerned；　however；　neither　with　the　personality　of　the　man　nor　yet　with　the　precise　doctrines　which　each　one　of　them　taught。　A　knowledge　of　the　latter　would　be　interesting　were　it　attainable；　but　in　the　confused　state　of　the　reports　that　have　come　down　to　us　we　cannot　hope　to　be　able　to　ascribe　each　idea　with　precision　to　its　proper　source。　At　best　we　can　merely　outline；　even　here　not　too　precisely；　the　scientific　doctrines　which　the　Italic　philosophers　as　a　whole　seem　to　have　advocated。　First　and　foremost；　there　is　the　doctrine　that　the　earth　is　a　sphere。　Pythagoras　is　said　to　have　been　the　first　advocate　of　this　theory；　but；　unfortunately；　it　is　reported　also　that　Parmenides　was　its　author。　This　rivalship　for　the　discovery　of　an　important　truth　we　shall　see　repeated　over　and　over　in　more　recent　times。　Could　we　know　the　whole　truth；　it　would　perhaps　appear　that　the　idea　of　the　sphericity　of　the　earth　was　originated　long　before　the　time　of　the　Greek　philosophers。　But　it　must　be　admitted　that　there　is　no　record　of　any　sort　to　give　tangible　support　to　such　an　assumption。　So　far　as　we　can　ascertain；　no　Egyptian　or　Babylonian　astronomer　ever　grasped　the　wonderful　conception　that　the　earth　is　round。　That　the　Italic　Greeks　should　have　conceived　that　idea　was　perhaps　not　so　much　because　they　were　astronomers　as　because　they　were　practical　geographers　and　geometers。　Pythagoras；　as　we　have　noted；　was　born　at　Samos；　and；　therefore；　made　a　relatively　long　sea　voyage　in　passing　to　Italy。　Now；　as　every　one　knows；　the　most　simple　and　tangible　demonstration　of　the　convexity　of　the　earth's　surface　is　furnished　by　observation　of　an　approaching　ship　at　sea。　On　a　clear　day　a　keen　eye　may　discern　the　mast　and　sails　rising　gradually　above　the　horizon；　to　be　followed　in　due　course　by　the　hull。　Similarly；　on　approaching　the　shore；　high　objects　become　visible　before　those　that　lie　nearer　the　water。　It　is　at　least　a　plausible　supposition　that　Pythagoras　may　have　made　such　observations　as　these　during　the　voyage　in　question；　and　that　therein　may　lie　the　germ　of　that　wonderful　conception　of　the　world　as　a　sphere。　To　what　extent　further　proof；　based　on　the　fact　that　the　earth's　shadow　when　the　moon　is　eclipsed　is　always　convex；　may　have　been　known　to　Pythagoras　we　cannot　say。　There　is　no　proof　that　any　of　the　Italic　philosophers　made　extensive　records　of　astronomical　observations　as　did　the　Egyptians　and　Babylonians；　but　we　must　constantly　recall　that　the　writings　of　classical　antiquity　have　been　almost　altogether　destroyed。　The　absence　of　astronomical　records　is；　therefore；　no　proof　that　such　records　never　existed。　Pythagoras；　it　should　be　said；　is　reported　to　have　travelled　in　Egypt；　and　he　must　there　have　gained　an　inkling　of　astronomical　methods。　Indeed；　he　speaks　of　himself　specifically；　in　a　letter　quoted　by　Diogenes；　as　one　who　is　accustomed　to　study　astronomy。　Yet　a　later　sentence　of　the　letter；　which　asserts　that　the　philosopher　is　not　always　occupied　about　speculations　of　his　own　fancy；　suggesting；　as　it　does；　the　dreamer　rather　than　the　observer；　gives　us　probably　a　truer　glimpse　into　the　philosopher's　mind。　There　is；　indeed；　reason　to　suppose　that　the　doctrine　of　the　sphericity　of　the　earth　appealed　to　Pythagoras　chiefly　because　it　accorded　with　his　conception　that　the　sphere　is　the　most　perfect　solid；　just　as　the　circle　is　the　most　perfect　plane　surface。　Be　that　as　it　may；　the　fact　remains　that　we　have　here；　as　far　as　we　can　trace　its　origin；　the　first　expression　of　the　scientific　theory　that　the　earth　is　round。　Had　the　Italic　philosophers　accomplished　nothing　more　than　this；　their　accomplishment　would　none　the　less　mark　an　epoch　in　the　progress　of　thought。　That　Pythagoras　was　an　observer　of　the　heavens　is　further　evidenced　by　the　statement　made　by　Diogenes；　on　the　authority　of　Parmenides；　that　Pythagoras　was　the　first　person　who　discovered　or　asserted　the　identity　of　Hesperus　and　Luciferthat　is　to　say；　of　the　morning　and　the　evening　star。　This　was　really　a　remarkable　discovery；　and　one　that　was　no　doubt　instrumental　later　on　in　determining　that　theory　of　the　mechanics　of　the　heavens　which　we　shall　see　elaborated　presently。　To　have　made　such　a　discovery　argues　again　for　the　practicality　of　the　mind　of　Pythagoras。　His；　indeed；　would　seem　to　have　been　a　mind　in　which　practical　common…sense　was　strangely　blended　with　the　capacity　for　wide　and　imaginative　generalization。　As　further　evidence　of　his　practicality；　it　is　asserted　that　he　was　the　first　person　who　introduced　measures　and　weights　among　the　Greeks；　this　assertion　being　made　on　the　authority　of　Aristoxenus。　It　will　be　observed　that　he　is　said　to　have　introduced；　not　to　have　invented；　weights　and　measures；　a　statement　which　suggests　a　knowledge　on　the　part　of　the　Greeks　that　weights　and　measures　were　previously　employed　in　Egypt　and　Babylonia。　The　mind　that　could　conceive　the　world　as　a　sphere　and　that　interested　itself　in　weights　and　measures　was；　obviously；　a　mind　of　the　visualizing　type。　It　is　characteristic　of　this　type　of　mind　to　be　interested　in　the　tangibilities　of　geometry；　hence　it　is　not　surprising　to　be　told　that　Pythagoras　〃carried　that　science　to　perfection。〃　The　most　famous　discovery　of　Pythagoras　in　this　field　was　that　the　square　of　the　hypotenuse　of　a　right…angled　triangle　is　equal　to　the　squares　of　the　other　sides　of　the　triangle。　We　have　already　noted　the　fable　that　his　enthusiasm　over　this　discovery　led　him　to　sacrifice　a　hecatomb。　Doubtless　the　story　is　apocryphal；　but　doubtless；　also；　it　expresses　the　truth　as　to　the　fervid　joy　with　which　the　philosopher　must　have　contemplated　the　results　of　his　creative　imagination。　No　line　alleged　to　have　been　written　by　Pythagoras　has　come　down　to　us。　We　are　told　that　he　refrained　from　publishing　his　doctrines；　except　by　word　of　mouth。　〃The　Lucanians　and　the　Peucetians；　and　the　Messapians　and　the　Romans；〃　we　are　assured；　〃flocked　around　him；　coming　with　eagerness　to　hear　his　discourses；　no　fewer　than　six　hundred　came　to　him　every　night；　and　if　any　one　of　them　had　ever　been　permitted　to　see　the　master；　they　wrote　of　it　to　their　friends　as　if　they　had　gained　some　great　advantage。〃　Nevertheless；　we　are　assured　that　until　the　time　of　Philolaus　no　doctrines　of　Pythagoras　were　ever　published；　to　which　statement　it　is　added　that　〃when　the　three　celebrated　books　were　published；　Plato　wrote　to　have　them　purchased　for　him　for　a　hundred　minas。〃＇2＇　But　if　such　books　existed；　they　are　lost　to　the　modern　world；　and　we　are　obliged　to　accept　the　assertions　of　relatively　late　writers　as　to　the　theories　of　the　great　Crotonian。　Perhaps　we　cannot　do　better　than　quote　at　length　from　an　important　summary　of　the　remaining　doctrines　of　Pythagoras；　which　Diogenes　himself　quoted　from　the　work　of　a　predecessor。＇3＇　Despite　its　somewhat　inchoate　character；　this　summary　is　a　most　remarkable　one；　as　a　brief　analysis　o