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。