Sensiblesubstanceischangeable。Nowifchangeproceedsfrom
　　oppositesorfromintermediates，andnotfromalloppositesforthe
　　voiceisnot-white，butitdoesnotthereforechangetowhite，
　　butfromthecontrary，theremustbesomethingunderlyingwhich
　　changesintothecontrarystate；forthecontrariesdonotchange。
　　Further，somethingpersists，butthecontrarydoesnotpersist；
　　thereis，then，somethirdthingbesidesthecontraries，viz。the
　　matter。Nowsincechangesareoffourkinds-eitherinrespectofthe
　　’what’orofthequalityorofthequantityoroftheplace，and
　　changeinrespectof’thisness’issimplegenerationand
　　destruction，andchangeinquantityisincreaseanddiminution，and
　　changeinrespectofanaffectionisalteration，andchangeofplace
　　ismotion，changeswillbefromgivenstatesintothosecontraryto
　　themintheseseveralrespects。Thematter，then，whichchangesmust
　　becapableofbothstates。Andsincethatwhich’is’hastwosenses，
　　wemustsaythateverythingchangesfromthatwhichispotentially
　　tothatwhichisactually，e。g。frompotentiallywhitetoactually
　　white，andsimilarlyinthecaseofincreaseanddiminution。Therefore
　　notonlycanathingcometobe，incidentally，outofthatwhichis
　　not，butalsoallthingscometobeoutofthatwhichis，butis
　　potentially，andisnotactually。Andthisisthe’One’ofAnaxagoras；
　　forinsteadof’allthingsweretogether’-andthe’Mixture’of
　　EmpedoclesandAnaximanderandtheaccountgivenbyDemocritus-itis
　　bettertosay’allthingsweretogetherpotentiallybutnotactually’。
　　Thereforethesethinkersseemtohavehadsomenotionofmatter。Now
　　allthingsthatchangehavematter，butdifferentmatter；andof
　　eternalthingsthosewhicharenotgenerablebutaremovablein
　　spacehavematter-notmatterforgeneration，however，butformotion
　　fromoneplacetoanother。
　　Onemightraisethequestionfromwhatsortofnon-being
　　generationproceeds；for’non-being’hasthreesenses。If，then，one
　　formofnon-beingexistspotentially，stillitisnotbyvirtueofa
　　potentialityforanyandeverything，butdifferentthingscomefrom
　　differentthings；norisitsatisfactorytosaythat’allthings
　　weretogether’；fortheydifferintheirmatter，sinceotherwisewhy
　　didaninfinityofthingscometobe，andnotonething？For
　　’reason’isone，sothatifmatteralsowereone，thatmusthave
　　cometobeinactualitywhichthematterwasinpotency。Thecauses
　　andtheprinciples，then，arethree，twobeingthepairof
　　contrariesofwhichoneisdefinitionandformandtheotheris
　　privation，andthethirdbeingthematter。
　　Note，next，thatneitherthematternortheformcomestobe-andI
　　meanthelastmatterandform。Foreverythingthatchangesis
　　somethingandischangedbysomethingandintosomething。Thatby
　　whichitischangedistheimmediatemover；thatwhichischanged，the
　　matter；thatintowhichitischanged，theform。Theprocess，then，
　　willgoontoinfinity，ifnotonlythebronzecomestoberoundbut
　　alsotheroundorthebronzecomestobe；thereforetheremustbea
　　stop。
　　Note，next，thateachsubstancecomesintobeingoutof
　　somethingthatsharesitsname。Naturalobjectsandotherthingsboth
　　rankassubstances。Forthingscomeintobeingeitherbyartorby
　　natureorbyluckorbyspontaneity。Nowartisaprincipleof
　　movementinsomethingotherthanthethingmoved，natureisa
　　principleinthethingitselfformanbegetsman，andtheother
　　causesareprivationsofthesetwo。
　　Therearethreekindsofsubstance-thematter，whichisa’this’
　　inappearanceforallthingsthatarecharacterizedbycontactand
　　not，byorganicunityarematterandsubstratum，e。g。fire，flesh，
　　head；fortheseareallmatter，andthelastmatteristhematterof
　　thatwhichisinthefullsensesubstance；thenature，whichisa
　　’this’orpositivestatetowardswhichmovementtakesplace；and
　　again，thirdly，theparticularsubstancewhichiscomposedofthese
　　two，e。g。SocratesorCallias。Nowinsomecasesthe’this’doesnot
　　existapartfromthecompositesubstance，e。g。theformofhouse
　　doesnotsoexist，unlesstheartofbuildingexistsapartnoris
　　theregenerationanddestructionoftheseforms，butitisin
　　anotherwaythatthehouseapartfromitsmatter，andhealth，and
　　allidealsofart，existanddonotexist；butifthe’this’exists
　　apartfromtheconcretething，itisonlyinthecaseofnatural
　　objects。AndsoPlatowasnotfarwrongwhenhesaidthatthereareas
　　manyFormsastherearekindsofnaturalobjectifthereareForms
　　distinctfromthethingsofthisearth。Themovingcausesexistas
　　thingsprecedingtheeffects，butcausesinthesenseofdefinitions
　　aresimultaneouswiththeireffects。Forwhenamanishealthy，then
　　healthalsoexists；andtheshapeofabronzesphereexistsatthe
　　sametimeasthebronzesphere。Butwemustexaminewhetherany
　　formalsosurvivesafterwards。Forinsomecasesthereisnothingto
　　preventthis；e。g。thesoulmaybeofthissort-notallsoulbutthe
　　reason；forpresumablyitisimpossiblethatallsoulshouldsurvive。
　　Evidentlythenthereisnonecessity，onthisgroundatleast，forthe
　　existenceoftheIdeas。Formanisbegottenbyman，agivenmanby
　　anindividualfather；andsimilarlyinthearts；forthemedicalart
　　istheformalcauseofhealth。
　　Thecausesandtheprinciplesofdifferentthingsareinasense
　　different，butinasense，ifonespeaksuniversallyandanalogically，
　　theyarethesameforall。Foronemightraisethequestionwhether
　　theprinciplesandelementsaredifferentorthesameforsubstances
　　andforrelativeterms，andsimilarlyinthecaseofeachofthe
　　categories。Butitwouldbeparadoxicaliftheywerethesameforall。
　　Forthenfromthesameelementswillproceedrelativetermsand
　　substances。Whatthenwillthiscommonelementbe？For1athere
　　isnothingcommontoanddistinctfromsubstanceandtheother
　　categories，viz。thosewhicharepredicated；butanelementisprior
　　tothethingsofwhichitisanelement。Butagainbsubstanceis
　　notanelementinrelativeterms，norisanyoftheseanelementin
　　substance。Further，2howcanallthingshavethesameelements？For
　　noneoftheelementscanbethesameasthatwhichiscomposedof
　　elements，e。g。boracannotbethesameasba。None，therefore，of
　　theintelligibles，e。g。beingorunity，isanelement；fortheseare
　　predicableofeachofthecompoundsaswell。Noneoftheelements，
　　then，willbeeitherasubstanceorarelativeterm；butitmustbe
　　oneorother。Allthings，then，havenotthesameelements。
　　Or，aswearewonttoputit，inasensetheyhaveandina
　　sensetheyhavenot；e。g。perhapstheelementsofperceptiblebodies
　　are，asform，thehot，andinanothersensethecold，whichisthe
　　privation；and，asmatter，thatwhichdirectlyandofitself
　　potentiallyhastheseattributes；andsubstancescompriseboththese
　　andthethingscomposedofthese，ofwhichthesearetheprinciples，
　　oranyunitywhichisproducedoutofthehotandthecold，e。g。flesh
　　orbone；fortheproductmustbedifferentfromtheelements。These
　　thingsthenhavethesameelementsandprinciplesthoughspecifically
　　differentthingshavespecificallydifferentelements；butallthings
　　havenotthesameelementsinthissense，butonlyanalogically；
　　i。e。onemightsaythattherearethreeprinciples-theform，the
　　privation，andthematter。Buteachoftheseisdifferentforeach
　　class；e。g。incolourtheyarewhite，black，andsurface，andinday
　　andnighttheyarelight，darkness，andair。
　　Sincenotonlytheelementspresentinathingarecauses，but
　　alsosomethingexternal，i。e。themovingcause，clearlywhile
　　’principle’and’element’aredifferentbotharecauses，and
　　’principle’isdividedintothesetwokinds；andthatwhichactsas
　　producingmovementorrestisaprincipleandasubstance。Therefore
　　analogicallytherearethreeelements，andfourcausesandprinciples；
　　buttheelementsaredifferentindifferentthings，andthe
　　proximatemovingcauseisdifferentfordifferentthings。Health，
　　disease，body；themovingcauseisthemedicalart。Form，disorder
　　ofaparticularkind，bricks；themovingcauseisthebuildingart。
　　Andsincethemovingcauseinthecaseofnaturalthingsis-forman，
　　forinstance，man，andintheproductsofthoughttheformorits
　　contrary，therewillbeinasensethreecauses，whileinasense
　　therearefour。Forthemedicalartisinsomesensehealth，andthe
　　buildingartistheformofthehouse，andmanbegetsman；further，
　　besidesthesethereisthatwhichasfirstofallthingsmovesall
　　things。
　　Somethingscanexistapartandsomecannot，anditisthe
　　formerthataresubstances。Andthereforeallthingshavethesame
　　causes，because，withoutsubstances，modificationsandmovementsdo
　　notexist。Further，thesecauseswillprobablybesoulandbody，or
　　reasonanddesireandbody。
　　Andinyetanotherway，analogicallyidenticalthingsare
　　principles，i。e。actualityandpotency；butthesealsoarenotonly
　　differentfordifferentthingsbutalsoapplyindifferentwaysto
　　them。Forinsomecasesthesamethingexistsatonetimeactuallyand
　　atanotherpotentially，e。g。wineorfleshormandoesso。And
　　thesetoofallundertheabove-namedcauses。Fortheformexists
　　actually，ifitcanexistapart，andsodoesthecomplexofformand
　　matter，andtheprivation，e。g。darknessordisease；butthematter
　　existspotentially；forthisisthatwhichcanbecomequalifiedeither
　　bytheformorbytheprivation。Butthedistinctionofactualityand
　　potentialityappliesinanotherwaytocaseswherethematterofcause
　　andofeffectisnotthesame，insomeofwhichcasestheformis
　　notthesamebutdifferent；e。g。thecauseofmanis1the
　　elementsinmanviz。fireandearthasmatter，andthepeculiar
　　form，andfurther2somethingelseoutside，i。e。thefather，and
　　3besidesthesethesunanditsobliquecourse，whichareneither
　　matternorformnorprivationofmannorofthesamespecieswithhim，
　　butmovingcauses。
　　Further，onemustobservethatsomecausescanbeexpressedin
　　universalterms，andsomecannot。Theproximateprinciplesofall
　　thingsarethe’this’whichisproximateinactuality，andanother
　　whichisproximateinpotentiality。Theuniversalcauses，then，of
　　whichwespokedonotexist。Foritistheindividualthatisthe
　　originativeprincipleoftheindividuals。Forwhilemanisthe
　　originativeprincipleofmanuniversally，thereisnouniversalman，
　　butPeleusistheoriginativeprincipleofAchilles，andyourfather
　　ofyou，andthisparticularbofthisparticularba，thoughbin
　　generalistheoriginativeprincipleofbatakenwithout
　　qualification。
　　Further，ifthecausesofsubstancesarethecausesofallthings，
　　yetdifferentthingshavedifferentcausesandelements，aswas
　　said；thecausesofthingsthatarenotinthesameclass，e。g。of
　　coloursandsounds，ofsubstancesandquantities，aredifferentexcept
　　inananalogicalsense；andthoseofthingsinthesamespeciesare
　　different，notinspecies，butinthesensethatthecausesof
　　differentindividualsaredifferent，yourmatterandformandmoving
　　causebeingdifferentfrommine，whileintheiruniversaldefinition
　　theyarethesame。Andifweinquirewhataretheprinciplesor
　　elementsofsubstancesandrelationsandqualities-whethertheyare
　　thesameordifferent-clearlywhenthenamesofthecausesareusedin
　　severalsensesthecausesofeacharethesame，butwhenthesenses
　　aredistinguishedthecausesarenotthesamebutdifferent，except
　　thatinthefollowingsensesthecausesofallarethesame。They
　　are1thesameoranalogousinthissense，thatmatter，form，
　　privation，andthemovingcausearecommontoallthings；and2
　　thecausesofsubstancesmaybetreatedascausesofallthingsin
　　thissense，thatwhensubstancesareremovedallthingsareremoved；
　　further，3thatwhichisfirstinrespectofcompleterealityisthe
　　causeofallthings。Butinanothersensetherearedifferentfirst
　　causes，viz。allthecontrarieswhichareneithergenericnor
　　ambiguousterms；and，further，themattersofdifferentthingsare
　　different。Wehavestated，then，whataretheprinciplesofsensible
　　thingsandhowmanytheyare，andinwhatsensetheyarethesame
　　andinwhatsensedifferent。