Fromthesefactswemaysufficientlyperceivethemeaningofthe
　　ancientswhosaidtheelementsofnatureweremorethanone；butthere
　　aresomewhospokeoftheuniverseasifitwereoneentity，though
　　theywerenotallalikeeitherintheexcellenceoftheirstatementor
　　initsconformitytothefactsofnature。Thediscussionofthemisin
　　nowayappropriatetoourpresentinvestigationofcauses，for。they
　　donot，likesomeofthenaturalphilosophers，assumebeingtobe
　　oneandyetgenerateitoutoftheoneasoutofmatter，butthey
　　speakinanotherway；thoseothersaddchange，sincetheygeneratethe
　　universe，butthesethinkerssaytheuniverseisunchangeable。Yet
　　thismuchisgermanetothepresentinquiry:Parmenidesseemsto
　　fastenonthatwhichisoneindefinition，Melissusonthatwhichis
　　oneinmatter，forwhichreasontheformersaysthatitislimited，
　　thelatterthatitisunlimited；whileXenophanes，thefirstof
　　thesepartisansoftheOneforParmenidesissaidtohavebeenhis
　　pupil，gavenoclearstatement，nordoesheseemtohavegrasped
　　thenatureofeitherofthesecauses，butwithreferencetothe
　　wholematerialuniversehesaystheOneisGod。Nowthesethinkers，as
　　wesaid，mustbeneglectedforthepurposesofthepresentinquiry-two
　　ofthementirely，asbeingalittletoonaive，viz。Xenophanesand
　　Melissus；butParmenidesseemsinplacestospeakwithmoreinsight。
　　For，claimingthat，besidestheexistent，nothingnon-existentexists，
　　hethinksthatofnecessityonethingexists，viz。theexistentand
　　nothingelseonthiswehavespokenmoreclearlyinourworkon
　　nature，butbeingforcedtofollowtheobservedfacts，and
　　supposingtheexistenceofthatwhichisoneindefinition，butmore
　　thanoneaccordingtooursensations，henowpositstwocausesandtwo
　　principles，callingthemhotandcold，i。e。fireandearth；andof
　　theseherangesthehotwiththeexistent，andtheotherwiththe
　　non-existent。
　　Fromwhathasbeensaid，then，andfromthewisemenwhohave
　　nowsatincouncilwithus，wehavegotthusmuch-ontheonehandfrom
　　theearliestphilosophers，whoregardthefirstprincipleascorporeal
　　forwaterandfireandsuchthingsarebodies，andofwhomsome
　　supposethatthereisonecorporealprinciple，othersthatthereare
　　morethanone，butbothputtheseundertheheadofmatter；andonthe
　　otherhandfromsomewhopositboththiscauseandbesidesthisthe
　　sourceofmovement，whichwehavegotfromsomeassingleandfrom
　　othersastwofold。
　　DowntotheItalianschool，then，andapartfromit，
　　philosophershavetreatedthesesubjectsratherobscurely，except
　　that，aswesaid，theyhaveinfactusedtwokindsofcause，andone
　　ofthese-thesourceofmovement-sometreatasoneandothersastwo。
　　ButthePythagoreanshavesaidinthesamewaythattherearetwo
　　principles，butaddedthismuch，whichispeculiartothem，that
　　theythoughtthatfinitudeandinfinitywerenotattributesofcertain
　　otherthings，e。g。offireorearthoranythingelseofthiskind，but
　　thatinfinityitselfandunityitselfwerethesubstanceofthethings
　　ofwhichtheyarepredicated。Thisiswhynumberwasthesubstance
　　ofallthings。Onthissubject，then，theyexpressedthemselves
　　thus；andregardingthequestionofessencetheybegantomake
　　statementsanddefinitions，buttreatedthemattertoosimply。For
　　theybothdefinedsuperficiallyandthoughtthatthefirstsubject
　　ofwhichagivendefinitionwaspredicablewasthesubstanceofthe
　　thingdefined，asifonesupposedthat’double’and’2’werethesame，
　　because2isthefirstthingofwhich’double’ispredicable。But
　　surelytobedoubleandtobe2arenotthesame；iftheyare，one
　　thingwillbemany-aconsequencewhichtheyactuallydrew。Fromthe
　　earlierphilosophers，then，andfromtheirsuccessorswecanlearn
　　thusmuch。
　　AfterthesystemswehavenamedcamethephilosophyofPlato，
　　whichinmostrespectsfollowedthesethinkers，buthad
　　pecullaritiesthatdistinguisheditfromthephilosophyofthe
　　Italians。For，havinginhisyouthfirstbecomefamiliarwithCratylus
　　andwiththeHeracliteandoctrinesthatallsensiblethingsare
　　everinastateoffluxandthereisnoknowledgeaboutthem，these
　　viewsheheldeveninlateryears。Socrates，however，wasbusying
　　himselfaboutethicalmattersandneglectingtheworldofnatureas
　　awholebutseekingtheuniversalintheseethicalmatters，and
　　fixedthoughtforthefirsttimeondefinitions；Platoacceptedhis
　　teaching，butheldthattheproblemappliednottosensiblethingsbut
　　toentitiesofanotherkind-forthisreason，thatthecommon
　　definitioncouldnotbeadefinitionofanysensiblething，asthey
　　werealwayschanging。Thingsofthisothersort，then，hecalled
　　Ideas，andsensiblethings，hesaid，wereallnamedafterthese，and
　　invirtueofarelationtothese；forthemanyexistedby
　　participationintheIdeasthathavethesamenameasthey。Onlythe
　　name’participation’wasnew；forthePythagoreanssaythatthings
　　existby’imitation’ofnumbers，andPlatosaystheyexistby
　　participation，changingthename。Butwhattheparticipationorthe
　　imitationoftheFormscouldbetheyleftanopenquestion。
　　Further，besidessensiblethingsandFormshesaystherearethe
　　objectsofmathematics，whichoccupyanintermediateposition，
　　differingfromsensiblethingsinbeingeternalandunchangeable，from
　　Formsinthattherearemanyalike，whiletheFormitselfisineach
　　caseunique。
　　SincetheFormswerethecausesofallotherthings，hethought
　　theirelementsweretheelementsofallthings。Asmatter，thegreat
　　andthesmallwereprinciples；asessentialreality，theOne；forfrom
　　thegreatandthesmall，byparticipationintheOne，comethe
　　Numbers。
　　ButheagreedwiththePythagoreansinsayingthattheOneis
　　substanceandnotapredicateofsomethingelse；andinsayingthat
　　theNumbersarethecausesoftherealityofotherthingsheagreed
　　withthem；butpositingadyadandconstructingtheinfiniteoutof
　　greatandsmall，insteadoftreatingtheinfiniteasone，is
　　peculiartohim；andsoishisviewthattheNumbersexistapart
　　fromsensiblethings，whiletheysaythatthethingsthemselvesare
　　Numbers，anddonotplacetheobjectsofmathematicsbetweenFormsand
　　sensiblethings。HisdivergencefromthePythagoreansinmakingthe
　　OneandtheNumbersseparatefromthings，andhisintroductionof
　　theForms，wereduetohisinquiriesintheregionofdefinitionsfor
　　theearlierthinkershadnotinctureofdialectic，andhismakingthe
　　otherentitybesidestheOneadyadwasduetothebeliefthatthe
　　numbers，exceptthosewhichwereprime，couldbeneatlyproducedout
　　ofthedyadasoutofsomeplasticmaterial。Yetwhathappensisthe
　　contrary；thetheoryisnotareasonableone。Fortheymakemany
　　thingsoutofthematter，andtheformgeneratesonlyonce，butwhat
　　weobserveisthatonetableismadefromonematter，whiletheman
　　whoappliestheform，thoughheisone，makesmanytables。Andthe
　　relationofthemaletothefemaleissimilar；forthelatteris
　　impregnatedbyonecopulation，butthemaleimpregnatesmany
　　females；yettheseareanaloguesofthosefirstprinciples。
　　Plato，then，declaredhimselfthusonthepointsinquestion；it
　　isevidentfromwhathasbeensaidthathehasusedonlytwocauses，
　　thatoftheessenceandthematerialcausefortheFormsarethe
　　causesoftheessenceofallotherthings，andtheOneisthecauseof
　　theessenceoftheForms；anditisevidentwhattheunderlying
　　matteris，ofwhichtheFormsarepredicatedinthecaseofsensible
　　things，andtheOneinthecaseofForms，viz。thatthisisadyad，
　　thegreatandthesmall。Further，hehasassignedthecauseofgood
　　andthatofeviltotheelements，onetoeachofthetwo，aswesay
　　someofhispredecessorssoughttodo，e。g。EmpedoclesandAnaxagoras。
　　Ourreviewofthosewhohavespokenaboutfirstprinciplesand
　　realityandofthewayinwhichtheyhavespoken，hasbeenconciseand
　　summary；butyetwehavelearntthismuchfromthem，thatofthosewho
　　speakabout’principle’and’cause’noonehasmentionedanyprinciple
　　exceptthosewhichhavebeendistinguishedinourworkonnature，
　　butallevidentlyhavesomeinklingofthem，thoughonlyvaguely。
　　Forsomespeakofthefirstprincipleasmatter，whetherthey
　　supposeoneormorefirstprinciples，andwhethertheysupposethisto
　　beabodyortobeincorporeal；e。g。Platospokeofthegreatand
　　thesmall，theItaliansoftheinfinite，Empedoclesoffire，earth，
　　water，andair，Anaxagorasoftheinfinityofthingscomposedof
　　similarparts。These，then，haveallhadanotionofthiskindof
　　cause，andsohaveallwhospeakofairorfireorwater，orsomething
　　denserthanfireandrarerthanair；forsomehavesaidtheprime
　　elementisofthiskind。
　　Thesethinkersgraspedthiscauseonly；butcertainothershave
　　mentionedthesourceofmovement，e。g。thosewhomakefriendshipand
　　strife，orreason，orlove，aprinciple。
　　Theessence，i。e。thesubstantialreality，noonehasexpressed
　　distinctly。ItishintedatchieflybythosewhobelieveintheForms；
　　fortheydonotsupposeeitherthattheFormsarethematterof
　　sensiblethings，andtheOnethematteroftheForms，orthattheyare
　　thesourceofmovementfortheysaythesearecausesratherof
　　immobilityandofbeingatrest，buttheyfurnishtheFormsasthe
　　essenceofeveryotherthing，andtheOneastheessenceoftheForms。
　　Thatforwhosesakeactionsandchangesandmovementstake
　　place，theyasserttobeacauseinaway，butnotinthisway，i。e。
　　notinthewayinwhichitisitsnaturetobeacause。Forthose
　　whospeakofreasonorfriendshipclassthesecausesasgoods；theydo
　　notspeak，however，asifanythingthatexistseitherexistedor
　　cameintobeingforthesakeofthese，butasifmovementsstarted
　　fromthese。InthesamewaythosewhosaytheOneortheexistentis
　　thegood，saythatitisthecauseofsubstance，butnotthat
　　substanceeitherisorcomestobeforthesakeofthis。Therefore
　　itturnsoutthatinasensetheybothsayanddonotsaythegood
　　isacause；fortheydonotcallitacausequagoodbutonly
　　incidentally。
　　Allthesethinkersthen，astheycannotpitchonanothercause，
　　seemtotestifythatwehavedeterminedrightlybothhowmanyandof
　　whatsortthecausesare。Besidesthisitisplainthatwhenthe
　　causesarebeinglookedfor，eitherallfourmustbesoughtthusor
　　theymustbesoughtinoneofthesefourways。Letusnextdiscussthe
　　possibledifficultieswithregardtothewayinwhicheachofthese
　　thinkershasspoken，andwithregardtohissituationrelativelyto
　　thefirstprinciples。