第4章

Thelatestoftheimportantpre-SocraticphilosophersoftheItalicschoolwasEmpedocles，whowasbornabout494B。C。andlivedtotheageofsixty。ThesedatesmakeEmpedoclesstrictlycontemporarywithAnaxagoras，afactwhichweshalldowelltobearinmindwhenwecometoconsiderthelatter’sphilosophyinthesucceedingchapter。LikePythagoras，Empedoclesisanimposingfigure。Indeed，thereismuchofsimilaritybetweenthepersonalities，asbetweenthedoctrines，ofthetwomen。

Empedocles，likePythagoras，wasaphysician；likehimalsohewasthefounderofacult。Asstatesman，prophet，physicist，physician，reformer，andpoetheshowedaversatilitythat，coupledwithprofundity，marksthehighestgenius。Inpointofversatilityweshallperhapshardlyfindhisequalatalaterday——unless，indeed，anexceptionbemadeofEratosthenes。ThemythsthathavegrownaboutthenameofEmpedoclesshowthathewasaremarkablepersonality。Heissaidtohavebeenanawe-inspiringfigure，clothinghimselfinOrientalsplendorandmovingamongmankindasasuperiorbeing。Traditionhasitthathethrewhimselfintothecraterofavolcanothathisotherwiseunexplaineddisappearancemightleadhisdisciplestobelievethathehadbeenmiraculouslytranslated；buttraditiongoesontosaythatoneofthebrazenslippersofthephilosopherwasthrownupbythevolcano，thusrevealinghissubterfuge。AnothertraditionoffarmorecredibleaspectassertsthatEmpedoclesretreatedfromItaly，returningtothehomeofhisfathersinPeloponnesustodiethereobscurely。Itseemsoddthatthefactsregardingthedeathofsogreataman，atsocomparativelylateaperiod，shouldbeobscure；butthis，perhaps，isinkeepingwiththepersonalityofthemanhimself。Hisdiscipleswouldhesitatetoascribeamerelynaturaldeathtosoinspiredaprophet。

Empedoclesappearstohavebeenatonceanobserverandadreamer。Heiscreditedwithnotingthatthepressureofairwillsustaintheweightofwaterinaninvertedtube；withdivining，withoutthepossibilityofproof，thatlighthasactualmotioninspace；andwithassertingthatcentrifugalmotionmustkeeptheheavensfromfalling。Heiscreditedwithagreatsanitaryfeatinthedrainingofamarsh，andhisknowledgeofmedicinewasheldtobesupernatural。Fortunately，somefragmentsofthewritingsofEmpedocleshavecomedowntous，enablingustojudgeatfirsthandastopartofhisdoctrines；whilestillmoreisknownthroughthereferencesmadetohimbyPlato，Aristotle，andothercommentators。Empedocleswasapoetwhoseversesstoodthetestofcriticism。InthisregardheisinalikepositionwithParmenides；butinneithercasearethepreservedfragmentssufficienttoenableusfullytoestimatetheirauthor’sscientificattainments。Philosophicalwritingsareobscureenoughatthebest，andtheyperforcebecomedoublysowhenexpressedinverse。YettherearecertainpassagesofEmpedoclesthatareunequivocalandfullofinterest。PerhapsthemostimportantconceptionwhichtheworksofEmpedoclesrevealtousisthedenialofanthropomorphismasappliedtodeity。Wehaveseenhowearlytheanthropomorphicconceptionwasdevelopedandhowcloselyitwasallalongclungto；toshakethemindfreefromitthenwasaremarkablefeat，inaccomplishingwhichEmpedoclestookalongstepinthedirectionofrationalism。Hisconceptionisparalleledbythatofanotherphysician，Alcmaeon，ofProton，whocontendedthatman’sideasofthegodsamountedtomeresuppositionsattheverymost。Arationalisticorscepticaltendencyhasbeentheaccompanimentofmedicaltraininginallages。

ThewordsinwhichEmpedoclesexpresseshisconceptionofdeityhavebeenpreservedandarewellworthquoting:"Itisnotimpossible，"hesays，"todrawnear(togod)evenwiththeeyesortotakeholdofhimwithourhands，whichintruthisthebesthighwayofpersuasioninthemindofman；forhehasnohumanheadfittedtoabody，nordotwoshootsbranchoutfromthetrunk，norhashefeet，norswiftlegs，norhairyparts，butheissacredandineffablemindalone，dartingthroughthewholeworldwithswiftthoughts。"[8]

HowfarEmpedoclescarriedhisdenialofanthropomorphismisillustratedbyareferenceofAristotle，whoasserts"thatEmpedoclesregardsgodasmostlackinginthepowerofperception；forhealonedoesnotknowoneoftheelements，Strife(hence)，ofperishablethings。"ItisdifficulttoavoidthefeelingthatEmpedocleshereapproachesthemodernphilosophicalconceptionthatGod，howeverpostulatedasimmutable，mustalsobepostulatedasunconscious，sinceintelligence，asweknowit，isdependentuponthetransmutationsofmatter。Buttourgethisthoughtwouldbetoyieldtothatphilosophizingtendencywhichhasbeenthebaneofinterpretationasappliedtotheancientthinkers。

ConsideringforamomentthemoretangibleaccomplishmentsofEmpedocles，wefinditallegedthatoneofhis"miracles"

consistedofthepreservationofadeadbodywithoutputrefactionforsomeweeksafterdeath。Wemayassumefromthisthathehadgainedinsomewayaknowledgeofembalming。Ashewasnotoriouslyfondofexperiment，andasthebodyinquestion(assumingforthemomenttheauthenticityofthelegend)musthavebeenpreservedwithoutdisfigurement，itisconceivableeventhathehadhitupontheideaofinjectingthearteries。This，ofcourse，ispureconjecture；yetitfindsacertainwarrant，bothinthefactthatthewordsofPythagorasleadustobelievethatthearterieswereknownandstudied，andinthefactthatEmpedocles’ownwordsrevealhimalsoasastudentofthevascularsystem。ThusPlutarchcitesEmpedoclesasbelieving"thattherulingpartisnotintheheadorinthebreast，butintheblood；whereforeinwhateverpartofthebodythemoreofthisisspreadinthatpartmenexcel。"[13]AndEmpedocles’ownwords，aspreservedbyStobaeus，assert"(theheart)liesinseasofbloodwhichdartinoppositedirections，andtheremostofallintelligencecentresformen；forbloodabouttheheartisintelligenceinthecaseofman。"Allthisimpliesareallyremarkableappreciationofthedependenceofvitalactivitiesupontheblood。

Thiscorrectphysiologicalconception，however，wasbynomeansthemostremarkableoftheideastowhichEmpedoeleswasledbyhisanatomicalstudies。Hisgreatestaccomplishmentwastohaveconceivedandclearlyexpressedanideawhichthemodernevolutionistconnoteswhenhespeaksofhomologousparts——anideawhichfoundafamousmodernexpositorinGoethe，asweshallseewhenwecometodealwitheighteenth-centuryscience。Empedoclesexpressestheideainthesewords:"Hair，andleaves，andthickfeathersofbirds，arethesamethinginorigin，andreptilescalestooonstronglimbs。Butonhedgehogssharp-pointedhairbristlesontheirbacks。"[14]Thattheideaoftransmutationofparts，aswellasofmerehomology，wasinmindisevidencedbyaveryremarkablesentenceinwhichAristotleasserts，"Empedoclessaysthatfingernailsrisefromsinewfromhardening。"Noristhisquiteall，forsurelywefindthegermoftheLamarckianconceptionofevolutionthroughthetransmissionofacquiredcharactersintheassertionthat"manycharacteristicsappearinanimalsbecauseithappenedtobethusintheirbirth，asthattheyhavesuchaspinebecausetheyhappentobedescendedfromonethatbentitselfbackward。"[15]Aristotle，inquotingthisremark，asserts，withthedogmatismwhichcharacterizesthephilosophicalcommentatorsofeveryage，that"Empedoclesiswrong，"inmakingthisassertion；butLamarck，wholivedtwenty-threehundredyearsafterEmpedocles，isfamousinthehistoryofthedoctrineofevolutionforelaboratingthisveryidea。

Itisfairtoadd，however，thatthedreamingsofEmpedoclesregardingtheoriginoflivingorganismsledhimtosomeconceptionsthatweremuchlessluminous。Onoccasion，EmpedoclesthepoetgotthebetterofEmpedoclesthescientist，andwearepresentedwithaconceptionofcreationasgrotesqueasthatwhichdelightedthereadersofParadiseLostatalaterday。

Empedoclesassuresusthat"manyheadsgrowupwithoutnecks，andarmswerewanderingabout，necksbereftofshoulders，andeyesroamedaboutalonewithnoforeheads。"[16]Thischaoticcondition，sothepoetdreamed，ledtotheunionofmanyincongruousparts，producing"creatureswithdoublefaces，offspringofoxenwithhumanfaces，andchildrenofmenwithoxenheads。"Butoutofthischaoscame，finally，weareledtoinfer，aharmoniousaggregationofparts，producingultimatelytheperfectedorganismsthatwesee。UnfortunatelythepreservedportionsofthewritingsofEmpedoclesdonotenlightenusastotheprecisewayinwhichfinalevolutionwassupposedtobeeffected；althoughtheideaofendlessexperimentationuntilnaturalselectionresultedinsurvivalofthefittestseemsnotfarafieldfromcertainofthepoeticalassertions。Thus:"Asdivinitywasmingledyetmorewithdivinity，thesethings(thevariousmembers)keptcomingtogetherinwhateverwayeachmightchance。"Again:"Atonetimeallthelimbswhichformthebodyunitedintoonebylovegrewvigorouslyintheprimeoflife；butyetatanothertime，separatedbyevilStrife，theywandereachindifferentdirectionsalongthebreakersoftheseaoflife。

Justsoisitwithplants，andwithfishesdwellinginwateryhalls，andbeastswhoselairisinthemountains，andbirdsborneonwings。"[17]

Allthisispoetryratherthanscience，yetsuchimaginingscouldcomeonlytoonewhowasgropingtowardswhatwemodernsshouldtermanevolutionaryconceptionoftheoriginsoforganiclife；

andhowevergrotesquesomeoftheseexpressionsmayappear，itmustbeadmittedthatthemorphologicalideasofEmpedocles，asabovequoted，givetheSicilianphilosopherasecureplaceamongtheanticipatorsofthemodernevolutionist。

VII。GREEKSCIENCEINTHEEARLYATTICPERIOD

WehavetravelledratherfarinourstudyofGreekscience，andyetwehavenotuntilnowcometoGreeceitself。Andevennow，themenwhosenameswearetoconsiderwere，forthemostpart，borninout-lyingportionsoftheempire；theydifferedfromtheotherswehaveconsideredonlyinthefactthattheyweredrawnpresentlytothecapital。Thechangeisduetoamostinterestingsequenceofhistoricalevents。InthedaywhenThalesandhisimmediatesuccessorstaughtinMiletus，whenthegreatmenoftheItalicschoolwereintheirprime，therewasnosingleundisputedCentreofGreekinfluence。TheGreekswereadisorganizedcompanyofpettynations，weldedtogetherchieflybyunityofspeech；butnow，earlyinthefifthcenturyB。C。，occurredthatfamousattackupontheWesternworldbythePersiansunderDariusandhissonandsuccessorXerxes。AfewmonthsofbattlingdeterminedthefateoftheWesternworld。TheOrientalswerehurledback；thegloriousmemoriesofMarathon，Salamis，andPlataeastimulatedthepatriotismandenthusiasmofallchildrenoftheGreekrace。

TheGreeks，forthefirsttime，occupiedthecentreofthehistoricalstage；forthebriefintervalofabouthalfacenturythedifferentGrecianprincipalitieslivedtogetherinrelativeharmony。Onecitywasrecognizedasthemetropolisofthelooselyboundempire；onecitybecamethehomeofcultureandtheMeccatowardswhichalleyesturned；thatcity，ofcourse，wasAthens。

ForabrieftimeallroadsledtoAthens，as，atalaterdate，theyallledtoRome。ThewaterwayswhichaloneboundthewidelyscatteredpartsofHellasintoaunitedwholeledoutfromAthensandbacktoAthens，asthespokesofawheeltoitshub。Athenswasthecommercialcentre，and，largelyforthatreason，itbecamethecentreofcultureandintellectualinfluencealso。Thewisemenfromthecoloniesvisitedthemetropolis，andthewiseAthenianswentouttothecolonies。Whoeveraspiredtobecomealeaderinpolitics，inart，inliterature，orinphilosophy，madehiswaytothecapital，andso，withalmostbewilderingsuddenness，thereblossomedthecivilizationoftheageofPericles；thecivilizationwhichproducedaeschylus，Sophocles，Euripides，Herodotus，andThucydides；thecivilizationwhichmadepossiblethebuildingoftheParthenon。

ANAXAGORAS

SometimeduringtheearlypartofthisgoldenagetherecametoAthensamiddle-agedmanfromClazomenae，who，fromourpresentstand-point，wasamoreinterestingpersonalitythanperhapsanyotherinthegreatgalaxyofremarkablemenassembledthere。Thenameofthisnew-comerwasAnaxagoras。Itwassaidinafter-time，weknownotwithwhatdegreeoftruth，thathehadbeenapupilofAnaximenes。Ifso，hewasapupilwhodepartedfarfromtheteachingsofhismaster。WhatweknowforcertainisthatAnaxagoraswasatrulyoriginalthinker，andthathebecameaclosefriend——inasensetheteacher——ofPericlesandofEuripides。JusthowlongheremainedatAthensisnotcertain；

butthetimecamewhenhehadmadehimselfinsomewayobjectionabletotheAthenianpopulacethroughhisteachings。

Filledwiththespiritoftheinvestigator，hecouldnotacceptthecurrentconceptionsastothegods。Hewasasceptic，aninnovator。Suchmenareneverwelcome；theyarethechieffactorsintheprogressofthought，buttheymustlookalwaystoposterityforrecognitionoftheirworth；fromtheircontemporariestheyreceive，notthanks，butpersecution。

Sometimesthispersecutiontakesoneform，sometimesanother；tothecreditoftheGreeksbeitsaid，thatwiththemitusuallyledtonothingmoreseverethanbanishment。InthecaseofAnaxagoras，itisallegedthatthesentencepronouncedwasdeath；

butthat，thankstotheinfluenceofPericles，thissentencewascommutedtobanishment。Inanyevent，theagedphilosopherwassentawayfromthecityofhisadoption。HeretiredtoLampsacus。

"ItisnotIthathavelosttheAthenians，"hesaid；"itistheAtheniansthathavelostme。"

TheexactpositionwhichAnaxagorashadamonghiscontemporaries，andhisexactplaceinthedevelopmentofphilosophy，havealwaysbeensomewhatindispute。Itisnotknown，ofacertainty，thatheevenheldanopenschoolatAthens。Ritterthinksitdoubtfulthathedid。Itwashisfatetobemisunderstood，orunderestimated，byAristotle；thatinitselfwouldhavesufficedgreatlytodimhisfame——might，indeed，haveledtohisalmostentireneglecthadhenotbeenatrulyremarkablethinker。Withmostofthequestionsthathaveexercisedthecommentatorswehavebutscantconcern。FollowingAristotle，mosthistoriansofphilosophyhavebeenmetaphysicians；theyhaveconcernedthemselvesfarlesswithwhattheancientthinkersreallyknewthanwithwhattheythought。Achanceusingofaverbalquibble，anesotericphrase，theexpressionofavaguemysticism——thesewouldsufficetocallforthreamsofexposition。Ithasbeenthefavoritepastimeofhistorianstoweavetheirownanachronistictheoriesuponthescantywoofofthehalf-rememberedthoughtsoftheancientphilosophers。Tomakesuchclothoftheimaginationasthisisanalluringpastime，butonethatmustnotdivertushere。Ourpointofviewreversesthatofthephilosophers。Wearechieflyconcerned，notwithsomevaguesayingofAnaxagoras，butwithwhathereallyknewregardingthephenomenaofnature；withwhatheobserved，andwiththecomprehensibledeductionsthathederivedfromhisobservations。Inattemptingtoanswertheseinquiries，weareobliged，inpart，totakeourevidenceatsecond-hand；but，fortunately，somefragmentsofwritingsofAnaxagorashavecomedowntous。Wearetoldthathewroteonlyasinglebook。Itwassaideven(byDiogenes)thathewasthefirstmanthateverwroteaworkinprose。Thelatterstatementwouldnotbeartoocloseanexamination，yetitistruethatnoextensiveprosecompositionsofanearlierdaythanthishavebeenpreserved，thoughnumerousothersareknownbytheirfragments。Herodotus，"thefatherofprose，"wasaslightlyyoungercontemporaryoftheClazomenaeanphilosopher；notunlikelythetwomenmayhavemetatAthens。

NotwithstandingthelossofthegreaterpartofthewritingsofAnaxagoras，however，atolerablypreciseaccountofhisscientificdoctrinesisaccessible。DiogenesLaertiusexpressessomeoftheminveryclearandpreciseterms。Wehavealreadypointedouttheuncertaintythatattachestosuchevidenceasthis，butitisasvalidforAnaxagorasasforanother。Ifwerejectsuchevidence，weshalloftenhavealmostnothingleft；inacceptingitwemayatleastfeelcertainthatweareviewingthethinkerashiscontemporariesandimmediatesuccessorsviewedhim。FollowingDiogenes，then，weshallfindsomeremarkablescientificopinionsascribedtoAnaxagoras。"Heasserted，"wearetold，"thatthesunwasamassofburningiron，greaterthanPeloponnesus，andthatthemooncontainedhousesandalsohillsandravines。"Incorroborationofthis，Platorepresentshimashavingconjecturedtherightexplanationofthemoon’slight，andofthesolarandlunareclipses。Hehadotherastronomicaltheoriesthatweremorefanciful；thus"hesaidthatthestarsoriginallymovedaboutinirregularconfusion，sothatatfirstthepole-star，whichiscontinuallyvisible，alwaysappearedinthezenith，butthatafterwardsitacquiredacertaindeclination，andthattheMilkyWaywasareflectionofthelightofthesunwhenthestarsdidnotappear。Thecometsheconsideredtobeaconcourseofplanetsemittingrays，andtheshooting-starshethoughtweresparks，asitwere，leapingfromthefirmament。"

Muchofthisisfarenoughfromthetruth，aswenowknowit，yetallofitshowsanearnestendeavortoexplaintheobservedphenomenaoftheheavensonrationalprinciples。Tohavepredicatedthesunasagreatmoltenmassofironwasindeedawonderfulanticipationoftheresultsofthemodernspectroscope。

NorcanitbesaidthatthishypothesisofAnaxagoraswasapurelyvisionaryguess。Itwasinallprobabilityascientificdeductionfromtheobservedcharacterofmeteoricstones。

ReferencehasalreadybeenmadetotheallegedpredictionofthefallofthefamousmeteorataegespotomibyAnaxagoras。Theassertionthatheactuallypredictedthisfallinanypropersenseofthewordwouldbeobviouslyabsurd。Yetthefactthathisnameisassociatedwithitsuggeststhathehadstudiedsimilarmeteorites，orelsethathestudiedthisparticularone，sinceitisnotquiteclearwhetheritwasbeforeorafterthisfallthathemadethefamousassertionthatspaceisfulloffallingstones。WeshouldstretchtheprobabilitieswerewetoassertthatAnaxagorasknewthatshooting-starsandmeteorswerethesame，yetthereisaninterestingsuggestivenessinhislikeningtheshooting-starstosparksleapingfromthefirmament，takeninconnectionwithhisobservationonmeteorites。Bethisasitmay，thefactthatsomethingwhichfallsfromheavenasablazinglightturnsouttobeaniron-likemassmayverywellhavesuggestedtothemostrationalofthinkersthatthegreatblazinglightcalledthesunhasthesamecomposition。Thisideagrasped，itwasanotunnaturalextensiontoconceivetheotherheavenlybodiesashavingthesamecomposition。

Thisledtoatrulystartlingthought。Sincetheheavenlybodiesareofthesamecompositionastheearth，andsincetheyareobservedtobewhirlingabouttheearthinspace，maywenotsupposethattheywereonceapartoftheearthitself，andthattheyhavebeenthrownoffbytheforceofawhirlingmotion？SuchwastheconclusionwhichAnaxagorasreached；suchhisexplanationoftheoriginoftheheavenlybodies。Itwasamarvellousguess。

Deductfromitallthatrecentsciencehasshowntobeuntrue；

bearinmindthatthestarsaresuns，comparedwithwhichtheearthisamerespeckofdust；recallthatthesunisparent，notdaughter，oftheearth，anddespiteallthesedeductions，thecosmogonicguessofAnaxagorasremains，asitseemstous，oneofthemostmarvellousfeatsofhumanintelligence。Itwasthefirstexplanationofthecosmicbodiesthatcouldbecalled，inanysense，ananticipationofwhatthescienceofourowndayacceptsasatrueexplanationofcosmicorigins。Moreover，letusurgeagainthatthiswasnomereaccidentalflightoftheimagination；

itwasascientificinductionbasedontheonlydataavailable；

perhapsitisnottoomuchtosaythatitwastheonlyscientificinductionwhichthesedatawouldfairlysustain。OfcourseitisnotforamomenttobeinferredthatAnaxagorasunderstood，inthemodernsense，thecharacterofthatwhirlingforcewhichwecallcentrifugal。Abouttwothousandyearswereyettoelapsebeforethatforcewasexplainedaselementaryinertia；andeventhatexplanation，letusnotforget，merelysufficedtopushbackthebarriersofmysterybyoneotherstage；foreveninourdayinertiaisastatementoffactratherthananexplanation。

ButhoweverlittleAnaxagorascouldexplainthecentrifugalforceonmechanicalprinciples，thepracticalpowersofthatforceweresufficientlyopentohisobservation。Themereexperimentofthrowingastonefromaslingwould，toanobservingmind，befullofsuggestiveness。Itwouldbeobviousthatbywhirlingtheslingabout，thestonewhichitheldwouldbesustainedinitscirclingpathaboutthehandinseemingdefianceoftheearth’spull，andafterthestonehadleftthesling，itcouldflyawayfromtheearthtoadistancewhichthemostcasualobservationwouldprovetobeproportionatetothespeedofitsflight。

Extremelyrapidmotion，then，mightprojectbodiesfromtheearth’ssurfaceoffintospace；asufficientlyrapidwhirlwouldkeepthemthere。Anaxagorasconceivedthatthiswaspreciselywhathadoccurred。Hisimaginationevencarriedhimastepfarther——toaconceptionofaslackeningofspeed，throughwhichtheheavenlybodieswouldlosetheircentrifugalforce，and，respondingtotheperpetualpullofgravitation，wouldfallbacktotheearth，justasthegreatstoneataegespotomihadbeenobservedtodo。

Herewewouldseemtohaveaclearconceptionoftheideaofuniversalgravitation，andAnaxagorasstandsbeforeusastheanticipatorofNewton。Wereitnotforonescientificmaxim，wemightexalttheoldGreekabovethegreatestofmodernnaturalphilosophers；butthatmaximbidsuspause。Itisphrasedthus，"Hediscoverswhoproves。"Anaxagorascouldnotprove；hisargumentwasatbestsuggestive，notdemonstrative。Hedidnotevenknowthelawswhichgovernfallingbodies；muchlesscouldheapplysuchlaws，evenhadheknownthem，tosiderealbodiesatwhosesizeanddistancehecouldonlyguessinthevaguestterms。

Stillhiscosmogonicspeculationremainsasperhapsthemostremarkableoneofantiquity。HowwidelyhisspeculationfoundcurrencyamonghisimmediatesuccessorsisinstancedinapassagefromPlato，whereSocratesisrepresentedasscornfullyansweringacalumniatorintheseterms:"HeassertsthatIsaythesunisastoneandthemoonanearth。DoyouthinkofaccusingAnaxagoras，Miletas，andhaveyousolowanopinionofthesemen，andthinkthemsounskilledinlaws，asnottoknowthatthebooksofAnaxagorastheClazomenaeanarefullofthesedoctrines。Andforsooththeyoungmenarelearningthesemattersfrommewhichsometimestheycanbuyfromtheorchestraforadrachma，atthemost，andlaughatSocratesifhepretendstheyarehis-particularlyseeingtheyaresostrange。"

TheelementoferrorcontainedinthesecosmogonicspeculationsofAnaxagorashasledcriticstodothemsomethinglessthanjustice。ButthereisoneotherastronomicalspeculationforwhichtheClazomenaeanphilosopherhasreceivedfullcredit。Itisgenerallyadmittedthatitwashewhofirstfoundouttheexplanationofthephasesofthemoon；aknowledgethatthatbodyshinesonlybyreflectedlight，andthatitsvisibleforms，waxingandwaningmonthbymonthfromcrescenttodiskandfromdisktocrescent，merelyrepresentourshiftingviewofitssun-illuminedface。Itisdifficulttoputourselvesintheplaceoftheancientobserverandrealizehowlittletheappearancessuggesttheactualfact。Thatabodyofthesamestructureastheearthshouldshinewiththeradianceofthemoonmerelybecausesunlightisreflectedfromit，isinitselfasuppositionseeminglycontradictedbyordinaryexperience。Itrequiredthemindofaphilosopher，sustained，perhaps，bysomeexperimentalobservations，toconceivetheideathatwhatseemssoobviouslybrightmaybeinrealitydark。Thegermoftheconceptionofwhatthephilosopherspeaksofasthenoumena，oractualities，backofphenomenaorappearances，hadperhapsthiscrudebeginning。

Anaxagorascouldsurelypointtothemooninsupportofhisseemingparadoxthatsnow，beingreallycomposedofwater，whichisdark，isinrealityblackandnotwhite——acontentiontowhichweshallrefermoreatlengthinamoment。

Butthereisyetanotherstrikingthoughtconnectedwiththisnewexplanationofthephasesofthemoon。Theexplanationimpliesnotmerelythereflectionoflightbyadarkbody，butbyadarkbodyofaparticularform。Grantedthatreflectionsareinquestion，nobodybutasphericalonecouldgiveanappearancewhichthemoonpresents。Themoon，then，isnotmerelyamassofearth，itisasphericalmassofearth。HeretherewerenoflawsinthereasoningofAnaxagoras。Byscientificinductionhepassedfromobservationtoexplanation。Anewandmostimportantelementwasaddedtothescienceofastronomy。

Lookingbackfromthelatter-daystand-point，itwouldseemasifthemindofthephilosophermusthavetakenoneotherstep:themindthathadconceivedsun，moon，stars，andearthtobeofonesubstancemightnaturally，weshouldthink，havereachedouttothefurtherinductionthat，sincethemoonisasphere，theothercosmicbodies，includingtheearth，mustbespheresalso。Butgeneralizerashewas，Anaxagoraswastoorigidlyscientificathinkertomakethisassumption。Thedataathiscommanddidnot，asheanalyzedthem，seemtopointtothisconclusion。WehaveseenthatPythagorasprobably，andParmenidessurely，outthereinItalyhadconceivedtheideaoftheearth’srotundity，butthePythagoreandoctrineswerenotrapidlytakenupinthemother-

country，andParmenides，itmustberecalled，wasastrictcontemporaryofAnaxagorashimself。Itisnoreproach，therefore，totheClazomenaeanphilosopherthatheshouldhaveheldtotheoldideathattheearthisflat，oratmostaconvexdisk——thelatterbeingtheBabylonianconceptionwhichprobablydominatedthatMilesianschooltowhichAnaxagorasharkedback。

Anaxagorasmayneverhaveseenaneclipseofthemoon，andevenifhehadhemighthavereflectedthat，fromcertaindirections，adiskmaythrowpreciselythesameshadowasasphere。Moreover，inreferencetotheshadowcastbytheearth，therewas，soAnaxagorasbelieved，anobservationopentohimnightlywhich，wemaywellsuppose，wasnotwithoutinfluenceinsuggestingtohismindtheprobableshapeoftheearth。TheMilkyWay，whichdoubtlesshadpuzzledastronomersfromthebeginningsofhistoryandwhichwastocontinuetopuzzlethemformanycenturiesafterthedayofAnaxagoras，wasexplainedbytheClazomenaeanphilosopheronatheoryobviouslysuggestedbythetheoryofthemoon’sphases。Sincetheearth-likemoonshinesbyreflectedlightatnight，andsincethestarsseemobviouslybrighterondarknights，AnaxagoraswasbutfollowingupaperfectlylogicalinductionwhenhepropoundedthetheorythatthestarsintheMilkyWayseemmorenumerousandbrighterthanthoseofanyotherpartoftheheavens，merelybecausetheMilkyWaymarkstheshadowoftheearth。Ofcoursetheinferencewaswrong，sofarastheshadowoftheearthisconcerned；yetitcontainedaparttruth，theforceofwhichwasneverfullyrecognizeduntilthetimeofGalileo。ThisconsistsintheassertionthatthebrightnessoftheMilkyWayismerelyduetotheglowofmanystars。Theshadow-theoryofAnaxagoraswouldnaturallyceasetohavevaliditysosoonasthesphericityoftheearthwasproved，andwithit，seemingly，fellforthetimethecompaniontheorythattheMilkyWayismadeupofamultitudeofstars。

Ithasbeensaidbyamoderncritic[1]thattheshadow-theorywaschildishinthatitfailedtonotethattheMilkyWaydoesnotfollowthecourseoftheecliptic。Butthiscriticismonlyholdsgoodsolongaswereflectonthetruecharacteroftheearthasasymmetricalbodypoisedinspace。ItisquitepossibletoconceiveabodyoccupyingthepositionoftheearthwithreferencetothesunwhichwouldcastashadowhavingsuchatenuousformastheMilkyWaypresents。Suchabodyobviouslywouldnotbeaglobe，butalong-drawn-out，attenuatedfigure。

Thereis，tobesure，nodirectevidencepreservedtoshowthatAnaxagorasconceivedtheworldtopresentsuchafigureasthis，butwhatweknowofthatphilosopher’sclose-reasoning，logicalmindgivessomewarranttotheassumption——gratuitousthoughinasenseitbe——thattheauthorofthetheoryofthemoon’sphaseshadnotfailedtoaskhimselfwhatmustbetheformofthatterrestrialbodywhichcouldcastthetenuousshadowoftheMilkyWay。Moreover，wemustrecallthatthehabitableearth，asknowntotheGreeksofthatday，wasarelativelynarrowbandofterritory，stretchingfartotheeastandtothewest。

AnaxagorasasMeteorologistThemanwhohadstudiedthemeteoriteofaegospotami，andbeenputbyitonthetrackofsuchremarkableinductions，was，naturally，notoblivioustotheotherphenomenaoftheatmosphere。Indeed，suchamindasthatofAnaxagoraswassuretoinvestigateallmannerofnaturalphenomena，andalmostequallysuretothrownewlightonanysubjectthatitinvestigated。

HenceitisnotsurprisingtofindAnaxagorascreditedwithexplainingthewindsasduetotherarefactionsoftheatmosphereproducedbythesun。ThisexplanationgivesAnaxagorasfullrighttobecalled"thefatherofmeteorology，"atitlewhich，itmaybe，noonehasthoughtofapplyingtohim，chieflybecausethescienceofmeteorologydidnotmakeitsrealbeginningsuntilsometwenty-fourhundredyearsafterthedeathofitsfirstgreatvotary。Notcontentwithexplainingthewinds，thisprototypeofFranklinturnedhisattentioneventothetipperatmosphere。

"Thunder，"heisreputedtohavesaid，"wasproducedbythecollisionoftheclouds，andlightningbytherubbingtogetheroftheclouds。"WedarenotgosofarastosuggestthatthisimpliesanassociationinthemindofAnaxagorasbetweenthefrictionofthecloudsandtheobservedelectricaleffectsgeneratedbythefrictionofsuchasubstanceasamber。TomakesuchasuggestiondoubtlesswouldbetofallvictimtotheoldfamiliarpropensitytoreadintoHomerthingsthatHomerneverknew。YetthesignificantfactremainsthatAnaxagorasascribedtothunderandtolightningtheirtruepositionasstrictlynaturalphenomena。Forhimitwasnogodthatmenacedhumanitywiththunderingvoiceandtheflashofhisdivinefiresfromtheclouds。LittlewonderthatthethinkerwhosesciencecarriedhimtosuchscepticismasthisshouldhavefeltthewrathofthesuperstitiousAthenians。

BiologicalSpeculationsPassingfromthephenomenaoftheairtothoseoftheearthitself，welearnthatAnaxagorasexplainedanearthquakeasbeingproducedbythereturningofairintotheearth。Wecannotbesureastotheexactmeaninghere，thoughtheideathatgasesareimprisonedinthesubstanceoftheearthseemsnotfarafield。

ButafarmoreremarkableinsightthanthiswouldimplywasshownbyAnaxagoraswhenheassertedthatacertainamountofairiscontainedinwater，andthatfishesbreathethisair。ThepassageofAristotleinwhichthisopinionisascribedtoAnaxagorasisofsufficientinteresttobequotedatlength:

"Democritus，ofAbdera，"saysAristotle，"andsomeothers，thathavespokenconcerningrespiration，havedeterminednothingconcerningotheranimals，butseemtohavesupposedthatallanimalsrespire。ButAnaxagorasandDiogenes(Apolloniates)，whosaythatallanimalsrespire，havealsoendeavoredtoexplainhowfishes，andallthoseanimalsthathaveahard，roughshell，suchasoysters，mussels，etc。，respire。AndAnaxagoras，indeed，saysthatfishes，whentheyemitwaterthroughtheirgills，attractairfromthemouthtothevacuumintheviscerafromthewaterwhichsurroundsthemouth；asifairwasinherentinthewater。"[2]

Itshouldberecalledthatofthethreephilosophersthusmentionedascontendingthatallanimalsrespire，Anaxagoraswastheelder；he，therefore，waspresumablytheoriginatoroftheidea。Itwillbeobserved，too，thatAnaxagorasaloneisheldresponsiblefortheideathatfishesrespireairthroughtheirgills，"attracting"itfromthewater。Thiscertainlywasoneoftheshrewdestphysiologicalguessesofanyage，ifitberegardedasamereguess。Withgreaterjusticewemightrefertoitasaprofounddeductionfromtheprincipleoftheuniformityofnature。

Inmakingsuchadeduction，AnaxagoraswasfarinadvanceofhistimeasillustratedbythefactthatAristotlemakesthecitationwehavejustquotedmerelytoaddthat"suchthingsareimpossible，"andtorefutethese"impossible"ideasbymeansofmetaphysicalreasoningsthatseemeddemonstrativenotmerelytohimself，buttomanygenerationsofhisfollowers。

WearetoldthatAnaxagorasallegedthatallanimalswereoriginallygeneratedoutofmoisture，heat，andearthparticles。

Justwhatopinionheheldconcerningman’sdevelopmentwearenotinformed。Yetthereisoneofhisphraseswhichsuggests——without，perhaps，quiteproving——thathewasanevolutionist。Thisphraseasserts，withinsightthatisfairlystartling，thatmanisthemostintelligentofanimalsbecausehehashands。Themanwhocouldmakethatassertionmust，itwouldseem，havehadinmindtheideaofthedevelopmentofintelligencethroughtheuseofhands——anideathefullforceofwhichwasnotevidenttosubsequentgenerationsofthinkersuntilthetimeofDarwin。

PhysicalSpeculationsAnaxagorasiscitedbyAristotleasbelievingthat"plantsareanimalsandfeelpleasureandpain，inferringthisbecausetheyshedtheirleavesandletthemgrowagain。"Theideaisfanciful，yetitsuggestsagainatrulyphilosophicalconceptionoftheunityofnature。Themanwhocouldconceivethatideawasbutlittlehamperedbytraditionalconceptions。Hewasexercisingararecombinationoftherigidlyscientificspiritwiththepoeticalimagination。Hewhopossessesthesegiftsissurenottostopinhisquestioningsofnatureuntilhehasfoundsomethinkableexplanationofthecharacterofmatteritself。

Anaxagorasfoundsuchanexplanation，and，asgoodluckwouldhaveit，thatexplanationhasbeenpreserved。Letusexaminehisreasoninginsomedetail。WehavealreadyreferredtotheclaimallegedtohavebeenmadebyAnaxagorasthatsnowisnotreallywhite，butblack。Thephilosopherexplainedhisparadox，wearetold，byassertingthatsnowisreallywater，andthatwaterisdark，whenviewedunderproperconditions——asatthebottomofawell。ThatideacontainsthegermoftheClazomenaeanphilosopher’sconceptionofthenatureofmatter。Indeed，itisnotunlikelythatthistheoryofmattergrewoutofhisobservationofthechangingformsofwater。Heseemsclearlytohavegraspedtheideathatsnowontheonehand，andvaporontheother，areofthesameintimatesubstanceasthewaterfromwhichtheyarederivedandintowhichtheymaybeagaintransformed。

Thefactthatsteamandsnowcanbechangedbackintowater，andbysimplemanipulationcannotbechangedintoanyothersubstance，finds，aswenowbelieve，itstrueexplanationinthefactthatthemolecularstructure，aswephraseit——thatistosay，theultimateparticleofwhichwateriscomposed，isnotchanged，andthisispreciselytheexplanationwhichAnaxagorasgaveofthesamephenomena。Forhimtheunitparticleofwaterconstitutedanelementarybody，uncreated，unchangeable，indestructible。Thisparticle，inassociationwithlikeparticles，constitutesthesubstancewhichwecallwater。Thesameparticleinassociationwithparticlesunlikeitself，mightproducetotallydifferentsubstances——as，forexample，whenwateristakenupbytherootsofaplantandbecomes，seemingly，apartofthesubstanceoftheplant。Butwhateverthechangedassociation，soAnaxagorasreasoned，theultimateparticleofwaterremainsaparticleofwaterstill。Andwhatwastrueofwaterwastruealso，soheconceived，ofeveryothersubstance。

Gold，silver，iron，earth，andthevariousvegetablesandanimaltissues——inshort，eachandeveryoneofallthedifferentsubstanceswithwhichexperiencemakesusfamiliar，ismadeupofunitparticleswhichmaintaintheirintegrityinwhatevercombinationtheymaybeassociated。Thisimplies，obviously，amultitudeofprimordialparticles，eachonehavinganindividualityofitsown；eachone，liketheparticleofwateralreadycited，uncreated，unchangeable，andindestructible。

Fortunately，wehavethephilosopher’sownwordstoguideusastohisspeculationshere。Thefragmentsofhiswritingsthathavecomedowntous(chieflythroughthequotationsofSimplicius)

dealalmostexclusivelywiththeseultimateconceptionsofhisimagination。Inascribingtohim，then，thisconceptionofdiverse，uncreated，primordialelements，whichcanneverbechanged，butcanonlybemixedtogethertoformsubstancesofthematerialworld，wearenotreadingbackpost-DaltonianknowledgeintothesystemofAnaxagoras。Herearehiswords:"TheGreeksdonotrightlyusetheterms’comingintobeing’and’perishing。’

Fornothingcomesintobeing，nor，yet，doesanythingperish；butthereismixtureandseparationofthingsthatare。Sotheywoulddorightincalling’comingintobeing’’mixture’and’perishing’

’separation。’Forhowcouldhaircomefromwhatisnothair？Orfleshfromwhatisnotflesh？"

Elsewherehetellsusthat(atonestageoftheworld’sdevelopment)"thedense，themoist，thecold，thedark，collectedtherewherenowisearth；therare，thewarm，thedry，thebright，departedtowardsthefurtherpartoftheaether。Theearthiscondensedoutofthesethingsthatareseparated，forwaterisseparatedfromtheclouds，andearthfromthewater；andfromtheearthstonesarecondensedbythecold，andtheseareseparatedfartherfromthewater。"Hereagaintheinfluenceofheatandcoldindeterminingphysicalqualitiesiskeptpre-eminentlyinmind。Thedense，themoist，thecold，thedarkarecontrastedwiththerare，thewarm，thedry，andbright；andtheformationofstonesisspokenofasaspecificcondensationduetotheinfluenceofcold。Here，then，wehavenearlyalltheelementsoftheDaltoniantheoryofatomsontheonehand，andthenebularhypothesisofLaplaceontheother。Butthisisnotquiteall。Inadditiontosuchdiverseelementaryparticlesasthoseofgold，water，andtherest，Anaxagorasconceivedaspeciesofparticlesdifferingfromalltheothers，notmerelyastheydifferfromoneanother，butconstitutingaclassbythemselves；particlesinfinitelysmallerthantheothers；

particlesthataredescribedasinfinite，self-powerful，mixedwithnothing，butexistingalone。Thatistosay(interpretingthetheoryintheonlywaythatseemsplausible)，thesemostminuteparticlesdonotmixwiththeotherprimordialparticlestoformmaterialsubstancesinthesamewayinwhichthesemixedwithoneanother。But，ontheotherhand，these"infinite，self-powerful，andunmixed"particlescommingleeverywhereandineverysubstancewhateverwiththemixedparticlesthatgotomakeupthesubstances。

Thereisadistinctionhere，itwillbeobserved，whichatoncesuggeststhemoderndistinctionbetweenphysicalprocessesandchemicalprocesses，or，puttingitotherwise，betweenmolecularprocessesandatomicprocesses；butthereadermustbeguardedagainstsupposingthatAnaxagorashadanysuchthoughtasthisinmind。HisultimatemixableparticlescanbecomparedonlywiththeDaltonianatom，notwiththemoleculeofthemodernphysicist，andhis"infinite，self-powerful，andunmixable"

particlesarenotcomparablewithanythingbuttheetherofthemodernphysicist，withwhichhypotheticalsubstancetheyhavemanypointsofresemblance。Butthe"infinite，self-powerful，andunmixed"particlesconstitutingthusanether-likeplenumwhichpermeatesallmaterialstructures，havealso，inthemindofAnaxagoras，afunctionwhichcarriesthemperhapsastagebeyondtheprovinceofthemodernether。Forthese"infinite，selfpowerful，andunmixed"particlesareimbuedwith，and，indeed，themselvesconstitute，whatAnaxagorastermsnous，awordwhichthemoderntranslatorhasusuallyparaphrasedas"mind。"

NeitherthatwordnoranyotheravailableoneprobablyconveysanaccurateideaofwhatAnaxagorasmeanttoimplybythewordnous。

Forhimthewordmeantnotmerely"mind"inthesenseofreceptiveandcomprehendingintelligence，butdirectiveandcreativeintelligenceaswell。AgainletAnaxagorasspeakforhimself:"Otherthingsincludeaportionofeverything，butnousisinfinite，andself-powerful，andmixedwithnothing，butitexistsalone，itselfbyitself。Forifitwerenotbyitself，butweremixedwithanythingelse，itwouldincludepartsofallthings，ifitweremixedwithanything；foraportionofeverythingexistsineverything，ashasbeensaidbymebefore，andthingsmingledwithitwouldpreventitfromhavingpoweroveranythinginthesamewaythatitdoesnowthatitisalonebyitself。Foritisthemostrarefiedofallthingsandthepurest，andithasallknowledgeinregardtoeverythingandthegreatestpower；overallthathaslife，bothgreaterandless，nousrules。Andnousruledtherotationofthewhole，sothatitsetitinrotationinthebeginning。Firstitbegantherotationfromasmallbeginning，thenmoreandmorewasincludedinthemotion，andyetmorewillbeincluded。Boththemixedandtheseparatedanddistinct，allthingsnousrecognized。Andwhateverthingsweretobe，andwhateverthingswere，asmanyasarenow，andwhateverthingsshallbe，allthesenousarrangedinorder；

anditarrangedthatrotation，accordingtowhichnowrotatestarsandsunandmoonandairandaether，nowthattheyareseparated。Rotationitselfcausedtheseparation，andthedenseisseparatedfromtherare，thewarmfromthecold，thebrightfromthedark，thedryfromthemoist。Andwhennousbegantosetthingsinmotion，therewasseparationfromeverythingthatwasinmotion，allthiswasmadedistinct。Therotationofthethingsthatweremovedandmadedistinctcausedthemtobeyetmoredistinct。"[3]

Nous，then，asAnaxagorasconceivesit，is"themostrarefiedofallthings，andthepurest，andithasknowledgeinregardtoeverythingandthegreatestpower；overallthathaslife，bothgreaterandless，itrules。"Butthesearepostulantsofomnipresenceandomniscience。Inotherwords，nousisnothinglessthantheomnipotentartificerofthematerialuniverse。Itlacksnothingofthepowerofdeity，saveonlythatwearenotassuredthatitcreatedtheprimordialparticles。ThecreationoftheseparticleswasaconceptionthatforAnaxagoras，asforthemodernSpencer，laybeyondtherangeofimagination。Nousistheartificer，workingwith"uncreated"particles。Backofnousandtheparticleslies，foranAnaxagorasasforaSpencer，theUnknowable。Butnousitselfistheequivalentofthatuniversalenergyofmotionwhichsciencerecognizesasoperatingbetweentheparticlesofmatter，andwhichthetheologistpersonifiesasDeity。ItisPantheisticdeityasAnaxagorasconceivesit；hismaybecalledthefirstscientificconceptionofanon-

anthropomorphicgod。InelaboratingthisconceptionAnaxagorasprovedhimselfoneofthemostremarkablescientificdreamersofantiquity。TohavesubstitutedfortheGreekPantheonofanthropomorphicdeitiestheconceptionofanon-anthropomorphicimmaterialandetherealentity，ofallthingsintheworld"themostrarefiedandthepurest，"istohaveperformedafeatwhich，consideringtheageandtheenvironmentinwhichitwasaccomplished，staggerstheimagination。Asastrictlyscientificaccomplishmentthegreatthinker’sconceptionofprimordialelementscontainedagermofthetruthwhichwastoliedormantfor2200years，butwhichthen，asmodifiedandvitalizedbythegeniusofDalton，wastodominatethenewchemicalscienceofthenineteenthcentury。IfthereareintimationsthattheprimordialelementofAnaxagorasandofDaltonmayturnoutinthenearfuturetobeitselfacompound，therewillstillremaintheyetfinerparticlesofthenousofAnaxagorastobafflethemostsubtleanalysisofwhichto-day’ssciencegivesusanypre-vision。Allinall，then，theworkofAnaxagorasmuststandasthatofperhapsthemostfar-seeingscientificimaginationofpre-Socraticantiquity。

LEUCIPPUSANDDEMOCRITUS

Butwemustnotleavethisalluringfieldofspeculationastothenatureofmatterwithoutreferringtoanotherscientificguess，whichsoonfollowedthatofAnaxagorasandwasdestinedtogainevenwiderfame，andwhichinmoderntimeshasbeensomewhatunjustlyheldtoeclipsethegloryoftheotherachievement。Wemean，ofcourse，theatomictheoryofLeucippusandDemocritus。

Thistheoryreducedallmattertoprimordialelements，calledatomsbecausetheyarebyhypothesisincapableoffurtherdivision。Theseatoms，makinguptheentirematerialuniverse，areinthistheoryconceivedasqualitativelyidentical，differingfromoneanotheronlyinsizeandperhapsinshape。Theunionofdifferent-sizedatomsinendlesscombinationsproducesthediversesubstanceswithwhichoursensesmakeusfamiliar。

Beforewepasstoaconsiderationofthisalluringtheory，andparticularlytoacomparisonofitwiththetheoryofAnaxagoras，wemustcatchaglimpseofthepersonalityofthementowhomthetheoryowesitsorigin。Oneofthese，Leucippus，presentssouncertainafigureastobealmostmythical。Indeed，itwaslongquestionedwhethersuchamanhadactuallylived，orwhetherbewerenotreallyaninventionofhisallegeddisciple，Democritus。

Latterdayscholarship，however，acceptshimasarealpersonage，thoughknowingscarcelymoreofhimthanthathewastheauthorofthefamoustheorywithwhichhisnamewasassociated。Itissuggestedthathewasawanderer，likemostphilosophersofhistime，andthatlaterinlifehecametoAbdera，inThrace，andthroughthiscircumstancebecametheteacherofDemocritus。Thisfableanswersaswellasanother。WhatwereallyknowisthatDemocritushimself，throughwhosewritingsandteachingstheatomictheorygainedvogue，wasborninAbdera，abouttheyear460B。C——thatistosay，justaboutthetimewhenhisgreatprecursor，Anaxagoras，wasmigratingtoAthens。Democritus，likemostothersoftheearlyGreekthinkers，livesintraditionasapicturesquefigure。Itisvaguelyreportedthathetravelledforatime，perhapsintheEastandinEgypt，andthatthenhesettleddowntospendtheremainderofhislifeinAbdera。

WhetherornothevisitedAthensinthecourseofhiswanderingswedonotknow。AtAbderahewasreveredasasage，buthisinfluenceuponthepracticalcivilizationofthetimewasnotmarked。Hewaspre-eminentlyadreamerandawriter。Likehisconfreresoftheepoch，heenteredallfieldsofthought。Hewrotevoluminously，but，unfortunately，hiswritingshave，forthemostpart，perished。ThefablesandtraditionsofalaterdayassertedthatDemocritushadvoluntarilyputouthisowneyesthathemightturnhisthoughtsinwardwithmoreconcentration。

Doubtlessthisisfiction，yet，asusualwithsuchfictions，itcontainsagermoftruth；forwemaywellsupposethatthepromulgatoroftheatomictheorywasamanwhosemindwasattractedbythesubtletiesofthoughtratherthanbythetangibilitiesofobservation。Yettheterm"laughingphilosopher，"whichseemstohavebeenuniversallyappliedtoDemocritus，suggestsamindnotaltogetherwithdrawnfromtheworldofpracticalities。

SomuchforDemocritustheman。Letusreturnnowtohistheoryofatoms。Thistheory，itmustbeconfessed，madenoverygreatimpressionuponhiscontemporaries。Itfoundanexpositor，alittlelater，inthephilosopherEpicurus，andlaterstillthepoetLucretiusgaveitpopularexpression。Butitseemedscarcelymorethanthedreamofaphilosopherorthevagaryofapoetuntilthedaywhenmodernsciencebegantopenetratethemysteriesofmatter。When，finally，theresearchesofDaltonandhisfollowershadplacedtheatomictheoryonasurerfootingasthefoundationofmodernchemistry，theideasoftheoldlaughingphilosopherofAbdera，whichallalonghadbeenhalfderisivelyremembered，wererecalledwithanewinterest。Nowitappearedthattheseideashadcuriouslyforeshadowednineteenth-centuryknowledge。ItappearedthatawaybackinthefifthcenturyB。C。amanhaddreamedoutaconceptionoftheultimatenatureofmatterwhichhadwaitedallthesecenturiesforcorroboration。AndnowthehistoriansofphilosophybecamemorethananxioustodojusticetothememoryofDemocritus。

Itispossiblethatthiseffortatpoeticalrestitutionhascarriedtheenthusiasttoofar。Thereis，indeed，acurioussuggestivenessinthetheoryofDemocritus；thereisphilosophicalallurementinhisreductionofallmattertoasingleelement；itcontains，itmaybe，notmerelyagermofthescienceofthenineteenth-centurychemistry，butperhapsthegermsalsooftheyetundevelopedchemistryofthetwentiethcentury。YetwedaresuggestthatintheirenthusiasmfortheatomictheoryofDemocritusthehistoriansofourgenerationhavedonesomethinglessthanjusticetothatphilosopher’sprecursor，Anaxagoras。Andonesuspectsthatthemereaccidentofanamehasbeeninstrumentalinproducingthisresult。Democrituscalledhisprimordialelementanatom；Anaxagoras，too，conceivedaprimordialelement，buthecalleditmerelyaseedorthing；hefailedtochristenitdistinctively。Modernscienceadoptedthewordatomandgaveituniversalvogue。ItowedadebtofgratitudetoDemocritusforsupplyingittheword，butitsomewhatoverpaidthedebtintoocloselylinkingthenewmeaningofthewordwithitsoldoriginalone。For，letitbeclearlyunderstood，theDaltonianatomisnotpreciselycomparablewiththeatomofDemocritus。Theatom，asDemocritusconceivedit，wasmonistic；allatoms，accordingtothishypothesis，areofthesamesubstance；oneatomdiffersfromanothermerelyinsizeandshape，butnotatallinquality。ButtheDaltonianhypothesisconceived，andnearlyalltheexperimentaleffortsofthenineteenthcenturyseemedtoprove，thattherearenumerousclassesofatoms，eachdifferinginitsveryessencefromtheothers。

Asthecasestandsto-daythechemistdealswithseventy-oddsubstances，whichhecallselements。Eachoneofthesesubstancesis，asheconceivesit，madeupofelementaryatomshavingauniquepersonality，eachdifferinginqualityfromalltheothers。Asfarasexperimenthasthusfarsafelycarriedus，theatomofgoldisaprimordialelementwhichremainsanatomofgoldandnothingelse，nomatterwithwhatotheratomsitisassociated。So，too，oftheatomofsilver，orzinc，orsodium——inshort，ofeachandeveryoneoftheseventy-oddelements。Thereare，indeed，asweshallsee，experimentsthatsuggestthedissolutionoftheatom——thatsuggest，inshort，thattheDaltonianatomismisnamed，beingastructurethatmay，undercertainconditions，bebrokenasunder。Buttheseexperimentshave，asyet，thewarrantratherofphilosophythanofpurescience，andto-daywedemandthatthephilosophyofscienceshallbethehandmaidofexperiment。

WhenexperimentshallhavedemonstratedthattheDaltonianatomisacompound，andthatintruththereisbutasingletrueatom，which，combiningwithitsfellowsperhapsinvaryingnumbersandindifferentspecialrelations，producestheDaltonianatoms，thenthephilosophicaltheoryofmonismwillhavetheexperimentalwarrantwhichto-dayitlacks；thenweshallbeastepnearertotheatomofDemocritusinonedirection，astepfartherawayintheother。Weshallbenearer，inthattheconceptionofDemocrituswas，inasense，monistic；fartheraway，inthatalltheatomsofDemocritus，largeandsmallalike，wereconsideredaspermanentlyfixedinsize。Democrituspostulatedallhisatomsasofthesamesubstance，differingnotatallinquality；yethewasobligedtoconceivethatthevaryingsizeoftheatomsgavetothemvaryingfunctionswhichamountedtoqualitativedifferences。Hemightclaimforhislargestatomthesamequalityofsubstanceasforhissmallest，butsolongasheconceivedthatthelargeatoms，whenadjustedtogethertoformatangiblesubstance，formedasubstancedifferentinqualityfromthesubstancewhichthesmallatomswouldmakeupwhensimilarlygrouped，thisconcessionamountstothepredicationofdifferenceofqualitybetweentheatomsthemselves。Theentirequestionreducesitselfvirtuallytoaquibbleoverthewordquality，Solongasoneatomconceivedtobeprimordialandindivisibleisconcededtobeofsuchanatureasnecessarilytoproduceadifferentimpressiononoursenses，whengroupedwithitsfellows，fromtheimpressionproducedbyotheratomswhensimilarlygrouped，suchprimordialatomsdodifferamongthemselvesinpreciselythesamewayforallpracticalpurposesasdotheprimordialelementsofAnaxagoras。

Themonisticconceptiontowardswhichtwentieth-centurychemistryseemstobecarryingusmayperhapsshowthatalltheso-calledatomsarecompoundedofasingleelement。Allthetrueatomsmakingupthatelementmaythenproperlybesaidtohavethesamequality，butnonethelesswillitremaintruethatthecombinationsofthatelementthatgotomakeupthedifferentDaltonianatomsdifferfromoneanotherinqualityinpreciselythesamesenseinwhichsuchtangiblesubstancesasgold，andoxygen，andmercury，anddiamondsdifferfromoneanother。Inthelastanalysisofthemonisticphilosophy，thereisbutonesubstanceandonequalityintheuniverse。Inthewidestviewofthatphilosophy，goldandoxygenandmercuryanddiamondsareonesubstance，and，ifyouplease，onequality。Butsuchrefinementsofanalysisasthisareforthetranscendentalphilosopher，andnotforthescientist。Whatevertheallurementofsuchreasoning，wemustforthepurposeofscienceletwordshaveaspecificmeaning，normustweletamereword-juggleryblindustotheevidenceoffacts。ThatwastherockonwhichGreeksciencefoundered；itistherockwhichthemodernhelmsmansometimesfindsitdifficulttoavoid。Andifwemistakenot，thiscaseoftheatomofDemocritusispreciselyacaseinpoint。BecauseDemocritussaidthathisatomsdidnotdifferinquality，themodernphilosopherhasseeninhistheorytheessentialsofmonism；hasdiscoveredinitnotmerelyaforecastofthechemistryofthenineteenthcentury，butaforecastofthehypotheticalchemistryofthefuture。And，ontheotherhand，becauseAnaxagoraspredictedadifferentqualityforhisprimordialelements，thephilosopherofourdayhasdiscreditedtheprimordialelementofAnaxagoras。

Yetifouranalysisdoesnotleadusastray，thetheoryofDemocrituswasnottrulymonistic；hisindestructibleatoms，differingfromoneanotherinsizeandshape，utterlyincapableofbeingchangedfromtheformwhichtheyhadmaintainedfromthebeginning，wereinrealityastrulyandprimordiallydifferentasaretheprimordialelementsofAnaxagoras。Inotherwords，theatomofDemocritusisnothinglessthantheprimordialseedofAnaxagoras，alittlemoretangiblyvisualizedandgivenadistinctivename。Anaxagorasexplicitlyconceivedhiselementsasinvisiblysmall，asinfiniteinnumber，andasmadeupofanindefinitenumberofkinds——oneforeachdistinctivesubstanceintheworld。ButpreciselythesamepostulatesaremadeoftheatomofDemocritus。Thesealsoareinvisiblysmall；thesealsoareinfiniteinnumber；thesealsoaremadeupofanindefinitenumberofkinds，correspondingwiththeobserveddifferenceofsubstancesintheworld。"Primitiveseeds，"or"atoms，"werealikeconceivedtobeprimordial，un-changeable，andindestructible。Whereinthenliesthedifference？Weanswer，chieflyinaname；almostsolelyinthefactthatAnaxagorasdidnotattempttopostulatethephysicalpropertiesoftheelementsbeyondstatingthateachhasadistinctivepersonality，whileDemocritusdidattempttopostulatetheseproperties。He，too，admittedthateachkindofelementhasitsdistinctivepersonality，andheattemptedtovisualizeanddescribethecharacteristicsofthepersonality。

ThuswhileAnaxagorastellsusnothingofhiselementsexceptthattheydifferfromoneanother，Democrituspostulatesadifferenceinsize，imaginessomeelementsasheavierandsomeaslighter，andconceiveseventhattheelementsmaybeprovidedwithprojectinghooks，withtheaidofwhichtheylinkthemselvesonewithanother。Nooneto-daytakesthesecrudevisualizingsseriouslyastotheirdetails。Thesoleelementoftruthwhichthesedreamingscontain，asdistinguishingthemfromthedreamingsofAnaxagoras，isintheconceptionthatthevariousatomsdifferinsizeandweight。Here，indeed，isavaguefore-shadowingofthatchemistryofformwhichbegantocomeintoprominencetowardsthecloseofthenineteenthcentury。Tohaveforecastevendimlythisnewestphaseofchemicalknowledge，acrosstheabyssofcenturies，isindeedafeattoputDemocritusinthefrontrankofthinkers。Butthisestimateshouldnotblindustothefactthatthepre-visionofDemocrituswasbutaslightelaborationofatheorywhichhaditsoriginwithanotherthinker。TheassociationbetweenAnaxagorasandDemocrituscannotbedirectlytraced，butitisanassociationwhichthehistorianofideasshouldneverforamomentforget。Ifwearenottobemisledbymereword-jugglery，weshallrecognizethefounderoftheatomictheoryofmatterinAnaxagoras；itsexpositorsalongslightlydifferentlinesinLeucippusandDemocritus；itsre-discovererofthenineteenthcenturyinDalton。Allinall，then，justasAnaxagorasprecededDemocritusintime，somusthetakeprecedenceoverhimalsoasaninductivethinker，whocarriedtheuseofthescientificimaginationtoitsfarthestreach。

Ananalysisofthetheoriesofthetwomenleadstosomewhatthesameconclusionthatmightbereachedfromacomparisonoftheirlives。Anaxagoraswasasceptical，experimentalscientist，giftedalsowiththepropheticimagination。Hereasonedalwaysfromtheparticulartothegeneral，afterthemanneroftrueinduction，andhescarcelytookastepbeyondtheconfinesofsecureinduction。Truescientistthathewas，hecouldcontenthimselfwithpostulatingdifferentqualitiesforhiselements，withoutpretendingtoknowhowthesequalitiescouldbedefined。Hiselementswerebyhypothesisinvisible，hencehewouldnotattempttovisualizethem。Democritus，ontheotherhand，refusedtorecognizethisbarrier。Wherehecouldnotknow，hestilldidnothesitatetoguess。Justasheconceivedhisatomofadefiniteformwithadefinitestructure，evensoheconceivedthattheatmosphereabouthimwasfullofinvisiblespirits；heacceptedthecurrentsuperstitionsofhistime。LiketheaverageGreeksofhisday，heevenbelievedinsuchomensasthosefurnishedbyinspectingtheentrailsofafowl。Thesechancebitsofbiographyareweather-vanesofthemindofDemocritus。TheytendtosubstantiateourconvictionthatDemocritusmustrankbelowAnaxagorasasadevoteeofpurescience。But，afterall，suchcomparisonsandestimatesasthisareutterlyfutile。Theessentialfactforusisthathere，inthefifthcenturybeforeourera，wefindputforwardthemostpenetratingguessastotheconstitutionofmatterthatthehistoryofancientthoughthastopresenttous。Inonedirection，theavenueofprogressisbarred；therewillbenofartherstepthatwaytillwecomedownthecenturiestothetimeofDalton。

HIPPOCRATESANDGREEKMEDICINE

Thesestudiesoftheconstitutionofmatterhavecarriedustothelimitsofthefieldofscientificimaginationinantiquity；

letusnowturnsharplyandconsideradepartmentofscienceinwhichtheoryjoinshandswithpracticality。Letuswitnessthebeginningsofscientifictherapeutics。

MedicineamongtheearlyGreeks，beforethetimeofHippocrates，wasacrudemixtureofreligion，necromancy，andmysticism。

Templeswereerectedtothegodofmedicine，aesculapius，andsickpersonsmadetheirway，orwerecarried，tothesetemples，wheretheysoughttogainthefavorofthegodbysuitableofferings，andlearnthewaytoregaintheirhealththroughremediesormethodsrevealedtothemindreamsbythegod。Whenthepatienthadbeenthuscured，heplacedatabletinthetempledescribinghissickness，andtellingbywhatmethodthegodhadcuredhim。Heagainmadesuitableofferingsatthetemple，whichweresometimesintheformofgoldorsilverrepresentationsofthediseasedorgan——agoldorsilvermodelofaheart，hand，foot，etc。

Nevertheless，despitethisbeliefinthesupernatural，manydrugsandhealinglotionswereemployed，andtheGreekphysicianspossessedconsiderableskillindressingwoundsandbandaging。

Buttheydidnotdependuponthesesurgicaldressingsalone，usingwiththemcertainappropriateprayersandincantations，recitedovertheinjuredmemberatthetimeofapplyingthedressings。

EventheveryearlyGreekshadlearnedsomethingofanatomy。Thedailycontactwithwoundsandbrokenbonesmustofnecessityleadtoacrudeunderstandingofanatomyingeneral。ThefirstGreekanatomist，however，whoisrecognizedassuch，issaidtohavebeenAlcmaeon。Heissaidtohavemadeextensivedissectionsoftheloweranimals，andtohavedescribedmanyhithertounknownstructures，suchastheopticnerveandtheEustachiancanal——thesmalltubeleadingintothethroatfromtheear。Heiscreditedwithmanyuniqueexplanationsofnaturalphenomena，suchas，forexample，theexplanationthat"hearingisproducedbythehollowbonebehindtheear；forallhollowthingsaresonorous。"Hewasarationalist，andhetaughtthatthebrainistheorganofmind。

Thesourcesofourinformationabouthiswork，however，areunreliable。

Democedes，wholivedinthesixthcenturyB。C。，isthefirstphysicianofwhomwehaveanytrustworthyhistory。WelearnfromHerodotusthathecamefromCrotontoaegina，where，inrecognitionofhisskill，hewasappointedmedicalofficerofthecity。FromaeginahewascalledtoAthensatanincreasedsalary，andlaterwasinchargeofmedicalaffairsinseveralotherGreekcities。HewasfinallycalledtoSamosbythetyrantPolycrates，whoreignedtherefromabout536to522B。C。ButonthedeathofPolycrates，whowasmurderedbythePersians，Democedesbecameaslave。Hisfameasaphysician，however，hadreachedtheearsofthePersianmonarch，andshortlyafterhiscapturehewaspermittedtoshowhisskilluponKingDariushimself。ThePersianmonarchwassufferingfromasprainedankle，whichhisEgyptiansurgeonshadbeenunabletocure。DemocedesnotonlycuredtheinjuredmemberbutusedhisinfluenceinsavingthelivesofhisEgyptianrivals，whohadbeencondemnedtodeathbytheking。

Atanothertimeheshowedhisskillbycuringthequeen，whowassufferingfromachronicabscessoflongstanding。Thissopleasedthemonarchthatheofferedhimasarewardanythinghemightdesire，excepthisliberty。ButthecostlygiftsofDariusdidnotsatisfyhimsolongasheremainedaslave；anddeterminedtosecurehisfreedomatanycost，hevolunteeredtoleadsomePersianspiesintohisnativecountry，promisingtousehisinfluenceinconvertingsomeoftheleadingmenofhisnationtothePersiancause。LadenwiththewealththathadbeenheapeduponhimbyDarius，hesetforthuponhismission，butuponreachinghisnativecityofCrotonhethrewoffhismask，renouncedhisPersianmission，andbecameoncemoreafreeGreek。

WhilethestoryofDemocedesthrowslittlelightuponthemedicalpracticesofthetime，itshowsthatpaidcitymedicalofficersexistedinGreeceasearlyasthefifthandsixthcenturiesB。C。

Eventhenthereweredifferent"schools"ofmedicine，whosedisciplesdisagreedradicallyintheirmethodsoftreatingdiseases；andtherewerealsospecialistsincertaindiseases，quacks，andcharlatans。Somephysiciansdependedentirelyuponexternallotionsforhealingalldisorders；otherswere"hydrotherapeutists"or"bath-physicians"；whiletherewereahostofphysicianswhoadministeredagreatvarietyofherbsanddrugs。Therewerealsomagicianswhopretendedtohealbysorcery，andgreatnumbersofbone-setters，oculists，anddentists。

Manyofthewealthyphysicianshadhospitals，orclinics，wherepatientswereoperateduponandtreated。Theywerenothospitalsinourmodernunderstandingoftheterm，butweremorelikedispensaries，wherepatientsweretreatedtemporarily，butwerenotallowedtoremainforanylengthoftime。Certaincommunitiesestablishedandsupportedthesedispensariesforthecareofthepoor。

Butanythingapproachingarationalsystemofmedicinewasnotestablished，untilHippocratesofCos，the"fatherofmedicine，"

cameuponthescene。InanagethatproducedPhidias，Lysias，Herodotus，Sophocles，andPericles，itseemsbutnaturalthatthemedicalartshouldfindanexponentwhowouldriseabovesuperstitiousdogmasandlaythefoundationforamedicalscience。Hisrejectionofthesupernaturalalonestampsthegreatnessofhisgenius。But，besidesthis，heintroducedmoredetailedobservationofdiseases，anddemonstratedtheimportancethatattachestoprognosis。

HippocrateswasbornatCos，about460B。C。，butspentmostofhislifeatLarissa，inThessaly。Hewaseducatedasaphysicianbyhisfather，andtravelledextensivelyasanitinerantpractitionerforseveralyears。Histravelsindifferentclimatesandamongmanydifferentpeopleundoubtedlytendedtosharpenhiskeensenseofobservation。Hewasapracticalphysicianaswellasatheorist，and，withal，aclearandconcisewriter。"Lifeisshort，"hesays，"opportunityfleeting，judgmentdifficult，treatmenteasy，buttreatmentafterthoughtisproperandprofitable。"

Hisknowledgeofanatomywasnecessarilyveryimperfect，andwasgainedlargelyfromhispredecessors，towhomhegavefullcredit。Dissectionsofthehumanbodywereforbiddenhim，andhewasobligedtoconfinehisexperimentalresearchestooperationsontheloweranimals。Hisknowledgeofthestructureandarrangementofthebones，however，wasfairlyaccurate，buttheanatomyofthesoftertissues，asheconceivedit，wasaqueerjumblingtogetherofblood-vessels，muscles，andtendons。Hedoesreferto"nerves，"tobesure，butapparentlythestructuresreferredtoarethetendonsandligaments，ratherthanthenervesthemselves。Hewasbetteracquaintedwiththeprincipalorgansinthecavitiesofthebody，andknew，forexample，thattheheartisdividedintofourcavities，twoofwhichhesupposedtocontainblood，andtheothertwoair。

Hismostrevolutionarystepwashisdivorcingofthesupernaturalfromthenatural，andestablishingthefactthatdiseaseisduetonaturalcausesandshouldbetreatedaccordingly。Theeffectofsuchanattitudecanhardlybeover-estimated。Theestablishmentofsuchatheorywasnaturallyfollowedbyacloseobservationastothecourseofdiseasesandtheeffectsoftreatment。Tofacilitatethis，heintroducedthecustomofwritingdownhisobservationsashemadethem——the"clinicalhistory"ofthecase。Suchclinicalrecordsareinuseallovertheworldto-day，andtheirimportanceissoobviousthatitisalmostincomprehensiblethattheyshouldhavefallenintodisuseshortlyafterthetimeofHippocrates，andnotbroughtintogeneraluseagainuntilalmosttwothousandyearslater。

Butscarcelylessimportantthanhisrecognitionofdiseaseasanaturalphenomenonwastheimportanceheattributedtoprognosis。

Prognosis，inthesenseofprophecy，wascommonbeforethetimeofHippocrates。Butprognosis，ashepractiseditandasweunderstanditto-day，isprophecybasedoncarefulobservationofthecourseofdiseases——somethingmorethansuperstitiousconjecture。

AlthoughHippocraticmedicinerestedonthebeliefinnaturalcauses，nevertheless，dogmaandtheoryheldanimportantplace。

Thehumoraltheoryofdiseasewasanall-importantone，andsofullywasthistheoryacceptedthatitinfluencedthescienceofmedicineallthroughsucceedingcenturies。Accordingtothiscelebratedtheorytherearefourhumorsinthebody——blood，phlegm，yellowbile，andblackbile。Whenthesehumorsaremixedinexactproportionstheyconstitutehealth；butanydeviationsfromtheseproportionsproducedisease。Intreatingdiseasestheaimofthephysicianwastodiscoverwhichofthesehumorswereoutofproportionandtorestorethemtotheirnaturalequilibrium。Itwasinthemethodsemployedinthisrestitution，ratherthanadisagreementaboutthehumorsthemselves，thatresultedinthevarious"schools"ofmedicine。

InmanywaysthesurgeryofHippocratesshowedabetterunderstandingofthestructureoftheorgansthanoftheirfunctions。Someofthesurgicalproceduresasdescribedbyhimarefollowed，withslightmodifications，to-day。Manyofhismethodswereentirelylostsightofuntilmoderntimes，andone，thetreatmentofdislocationoftheouterendofthecollar-bone，wasnotreviveduntilsometimeintheeighteenthcentury。

Hippocrates，itseems，likemodernphysicians，sometimessufferedfromtheingratitudeofhispatients。"Thephysicianvisitsapatientsufferingfromfeverorawound，andprescribesforhim，"

hesays；"onthenextday，ifthepatientfeelsworsetheblameislaiduponthephysician；if，ontheotherhand，hefeelsbetter，natureisextolled，andthephysicianreapsnopraise。"

Theessenceofthishasbeenrepeatedinrhymeandprosebywritersineveryageandcountry，butthe"fatherofmedicine"

cautionsphysiciansagainstallowingittoinfluencetheirattitudetowardstheirprofession。

Doubtlessithasbeennoticedthatourearlierscientistswereasfarremovedaspossiblefromthelimitationsofspecialism。Inpointoffact，inthisearlyday，knowledgehadnotbeenclassifiedasitcametobelateron。Thephilosopherwas，ashisnameimplied，aloverofknowledge，andhedidnotfinditbeyondthereachofhiscapacitytoapplyhimselftoalldepartmentsofthefieldofhumaninvestigation。ItisnothingstrangetodiscoverthatAnaximanderandthePythagoreansandAnaxagorashavepropoundedtheoriesregardingthestructureofthecosmos，theoriginanddevelopmentofanimalsandman，andthenatureofmatteritself。Nowadays，soenormouslyinvolvedhasbecomethemassofmerefactsregardingeachofthesedepartmentsofknowledgethatnoonemanhasthetemeritytoattempttomasterthemall。Butitwasdifferentinthosedaysofbeginnings。Thenthemethodsofobservationwerestillcrude，anditwasquitethecustomforathinkerofforcefulpersonalitytofindaneagerfollowingamongdiscipleswhoneverthoughtofputtinghistheoriestothetestofexperiment。Thegreatlessonthattruescienceinthelastresortdependsuponobservationandmeasurement，uponcompassandbalance，hadnotyetbeenlearned，thoughhereandthereathinkerlikeAnaxagorashadgainedaninklingofit。

Forthemoment，indeed，thereinAttica，whichwasnow，thankstothatoutburstofPericleanculture，thecentreoftheworld’scivilization，thetrendofthoughtwastotakequiteanotherdirection。TheveryyearwhichsawthebirthofDemocritusatAbdera，andofHippocrates，markedalsothebirth，atAthens，ofanotherremarkableman，whoseinfluenceitwouldscarcelybepossibletoover-estimate。ThismanwasSocrates。Themainfactsofhishistoryarefamiliartoeveryone。ItwillberecalledthatSocratesspenthisentirelifeinAthens，minglingeverywherewiththepopulace；haranguing，sothetraditiongoes，everyonewhowouldlisten；inculcatingmorallessons，andfinallyincurringthedisapprobationofatleastavotingmajorityofhisfellow-citizens。HegatheredabouthimacompanyofremarkablemenwithPlatoattheirhead，butthiscouldnotsavehimfromthedisapprobationofthemultitudes，atwhosehandshesuffereddeath，legallyadministeredafterapublictrial。ThefactsatcommandastocertaincustomsoftheGreeksatthisperiodmakeitpossibletoraiseaquestionastowhetherthealleged"corruptionofyouth，"withwhichSocrateswascharged，maynothavehadadifferentimplicationfromwhatposterityhaspreferredtoascribetoit。Butthisthought，almostshockingtothemodernmindandseemingaltogethersacrilegioustomoststudentsofGreekphilosophy，neednotheredetainus；neitherhavewemuchconcerninthepresentconnectionwithanypartoftheteachingofthemartyredphilosopher。Forthehistorianofmetaphysics，Socratesmarksanepoch，butforthehistorianofscienceheisamuchlessconsequentialfigure。

SimilarlyregardingPlato，thearistocraticAthenianwhosatatthefeetofSocrates，andthroughwhosewritingstheteachingsofthemasterfoundwidestcurrency。SomestudentsofphilosophyfindinPlato"thegreatestthinkerandwriterofalltime。"[1]

Thestudentofsciencemustrecognizeinhimathinkerwhosepointofviewwasessentiallynon-scientific；onewhotendedalwaystoreasonfromthegeneraltotheparticularratherthanfromtheparticulartothegeneral。Plato’swritingscoveredalmosttheentirefieldofthought，andhisideaswerepresentedwithsuchliterarycharmthatsuccessivegenerationsofreadersturnedtothemwithunflagginginterest，andgavethemwidecurrencythroughcopiesthatfinallypreservedthemtoourowntime。Thuswearenotobligedinhiscase，asweareinthecaseofeveryotherGreekphilosopher，toestimatehisteachingslargelyfromhearsayevidence。Platohimselfspeakstousdirectly。Itistrue，theliteraryformwhichhealwaysadopted，namely，thedialogue，doesnotgivequitethesamecertaintyastowhenheisexpressinghisownopinionsthatamoredirectnarrativewouldhavegiven；yet，inthemain，thereislittledoubtastothetenorofhisownopinions——except，indeed，suchdoubtasalwaysattachestothephilosophicalreasoningoftheabstractthinker。

Whatischieflysignificantfromourpresentstandpointisthatthegreatethicalteacherhadnosignificantmessagetogivetheworldregardingthephysicalsciences。Heapparentlyhadnosharplydefinedopinionsastothemechanismoftheuniverse；noclearconceptionastotheoriginordevelopmentoforganicbeings；notangibleideasastotheproblemsofphysics；nofavoritedreamsastothenatureofmatter。Virtuallyhisbackwasturnedonthisentirefieldofthought。Hewasundertheswayofthoseinnateideaswhich，aswehaveurged，wereamongtheearliestinductionsofscience。Butheneverforamomentsuspectedsuchanoriginfortheseideas。Hesupposedhisconceptionsofbeing，hisstandardsofethics，toliebackofallexperience；forhimtheywerethemostfundamentalandmostdependableoffacts。HecriticisedAnaxagorasforhavingtendedtodeducegenerallawsfromobservation。Aswemodernsseeit，suchcriticismisthehighestpossiblepraise。Itisacriticismthatmarksthedistinctionbetweenthescientistwhoisalsoaphilosopherandthephilosopherwhohasbutavaguenotionofphysicalscience。Platoseemed，indeed，torealizethevalueofscientificinvestigation；hereferredtotheastronomicalstudiesoftheEgyptiansandChaldeans，andspokehopefullyoftheresultsthatmightaccrueweresuchstudiestobetakenupbythatGreekmindwhich，ashejustlyconceived，hadthepowertovitalizeandenrichallthatittouched。Buthetoldhereofwhathewouldhaveothersdo，notofwhathehimselfthoughtofdoing。

Hisvoicewasprophetic，butitstimulatednoworkerofhisowntime。

Platohimselfhadtravelledwidely。ItisafamiliarlegendthathelivedforyearsinEgypt，endeavoringtheretopenetratethemysteriesofEgyptianscience。Itissaideventhattherudimentsofgeometrywhichheacquiredthereinfluencedallhislaterteachings。Butbethatasitmay，thehistorianofsciencemustrecognizeinthefounderoftheAcademyamoralteacherandmetaphysicaldreamerandsociologist，butnot，inthemodernacceptanceoftheterm，ascientist。Thosewiderphasesofbiologicalsciencewhichfindtheirexpressioninmetaphysics，inethics，inpoliticaleconomy，liewithoutourpresentscope；andforthedevelopmentofthosesubjectswithwhichwearemoredirectlyconcerned，Plato，likehismaster，hasanegativesignificance。