This，then，musteitherbeeternaloritmustbedestructible
withoutbeingeverincourseofbeingdestroyed，andmusthavecometo
bewithouteverbeingincourseofcomingtobe。Butithasbeen
provedandexplainedelsewherethatnoonemakesorbegetstheform，
butitistheindividualthatismade，i。e。thecomplexofformand
matterthatisgenerated。Whetherthesubstancesofdestructible
thingscanexistapart，isnotyetatallclear；exceptthatobviously
thisisimpossibleinsomecases-inthecaseofthingswhichcannot
existapartfromtheindividualinstances，e。g。houseorutensil。
Perhaps，indeed，neitherthesethingsthemselves，noranyoftheother
thingswhicharenotformedbynature，aresubstancesatall；for
onemightsaythatthenatureinnaturalobjectsistheonlysubstance
tobefoundindestructiblethings。
Thereforethedifficultywhichusedtoberaisedbytheschool
ofAntisthenesandothersuchuneducatedpeoplehasacertain
timeliness。Theysaidthatthe’what’cannotbedefinedforthe
definitionsocalledisa’longrigmarole’butofwhatsorta
thing，e。g。silver，is，theythoughtitpossibleactuallyto
explain，notsayingwhatitis，butthatitisliketin。Thereforeone
kindofsubstancecanbedefinedandformulated，i。e。thecomposite
kind，whetheritbeperceptibleorintelligible；buttheprimaryparts
ofwhichthisconsistscannotbedefined，sinceadefinitoryformula
predicatessomethingofsomething，andonepartofthedefinitionmust
playthepartofmatterandtheotherthatofform。
Itisalsoobviousthat，ifsubstancesareinasensenumbers，
theyaresointhissenseandnot，assomesay，asnumbersofunits。
Foradefinitionisasortofnumber；for1itisdivisible，and
intoindivisiblepartsfordefinitoryformulaearenotinfinite，and
numberalsoisofthisnature。And2as，whenoneofthepartsof
whichanumberconsistshasbeentakenfromoraddedtothenumber，it
isnolongerthesamenumber，butadifferentone，evenifitisthe
verysmallestpartthathasbeentakenawayoradded，sothe
definitionandtheessencewillnolongerremainwhenanythinghas
beentakenawayoradded。And3thenumbermustbesomethingin
virtueofwhichitisone，andthisthesethinkerscannotstate，
whatmakesitone，ifitisoneforeitheritisnotonebutasort
ofheap，orifitis，weoughttosaywhatitisthatmakesoneoutof
many；andthedefinitionisone，butsimilarlytheycannotsaywhat
makesitone。Andthisisanaturalresult；forthesamereasonis
applicable，andsubstanceisoneinthesensewhichwehaveexplained，
andnot，assomesay，bybeingasortofunitorpoint；eachisa
completerealityandadefinitenature。And4asnumberdoesnot
admitofthemoreandtheless，neitherdoessubstance，inthesense
ofform，butifanysubstancedoes，itisonlythesubstancewhich
involvesmatter。Letthis，then，sufficeforanaccountofthe
generationanddestructionofso-calledsubstancesinwhatsenseitis
possibleandinwhatsenseimpossible——andofthereductionof
thingstonumber。
Regardingmaterialsubstancewemustnotforgetthatevenifall
thingscomefromthesamefirstcauseorhavethesamethingsfor
theirfirstcauses，andifthesamematterservesasstarting-point
fortheirgeneration，yetthereisamatterpropertoeach，e。g。for
phlegmthesweetorthefat，andforbilethebitter，orsomething
else；thoughperhapsthesecomefromthesameoriginalmatter。And
therecometobeseveralmattersforthesamething，whentheone
matterismatterfortheother；e。g。phlegmcomesfromthefatand
fromthesweet，ifthefatcomesfromthesweet；anditcomesfrom
bilebyanalysisofthebileintoitsultimatematter。Foronething
comesfromanotherintwosenses，eitherbecauseitwillbefoundata
laterstage，orbecauseitisproducediftheotherisanalysedinto
itsoriginalconstituents。Whenthematterisone，differentthings
maybeproducedowingtodifferenceinthemovingcause；e。g。from
woodmaybemadebothachestandabed。Butsomedifferentthings
musthavetheirmatterdifferent；e。g。asawcouldnotbemadeof
wood，noristhisinthepowerofthemovingcause；foritcouldnot
makeasawofwoolorofwood。Butif，asamatteroffact，thesame
thingcanbemadeofdifferentmaterial，clearlytheart，i。e。the
movingprinciple，isthesame；forifboththematterandthemoving
causeweredifferent，theproductwouldbesotoo。
Whenoneinquiresintothecauseofsomething，oneshould，since
’causes’arespokenofinseveralsenses，stateallthepossible
causes。whatisthematerialcauseofman？Shallwesay’themenstrual
fluid’？Whatismovingcause？Shallwesay’theseed’？Theformal
cause？Hisessence。Thefinalcause？Hisend。Butperhapsthelatter
twoarethesame-Itistheproximatecauseswemuststate。Whatis
thematerialcause？Wemustnamenotfireorearth，butthematter
peculiartothething。
Regardingthesubstancesthatarenaturalandgenerable，ifthe
causesarereallytheseandofthisnumberandwehavetolearnthe
causes，wemustinquirethus，ifwearetoinquirerightly。Butinthe
caseofnaturalbuteternalsubstancesanotheraccountmustbe
given。Forperhapssomehavenomatter，ornotmatterofthissortbut
onlysuchascanbemovedinrespectofplace。Nordoesmatter
belongtothosethingswhichexistbynaturebutarenotsubstances；
theirsubstratumisthesubstance。E。gwhatisthecauseofeclipse？
Whatisitsmatter？Thereisnone；themoonisthatwhichsuffers
eclipse。Whatisthemovingcausewhichextinguishedthelight？The
earth。Thefinalcauseperhapsdoesnotexist。Theformalprincipleis
thedefinitoryformula，butthisisobscureifitdoesnotincludethe
cause。E。g。whatiseclipse？Deprivationoflight。Butifweadd’by
theearth’scominginbetween’，thisistheformulawhichincludesthe
cause。Inthecaseofsleepitisnotclearwhatitisthat
proximatelyhasthisaffection。Shallwesaythatitistheanimal？
Yes，buttheanimalinvirtueofwhat，i。e。whatistheproximate
subject？Theheartorsomeotherpart。Next，bywhatisitproduced？
Next，whatistheaffection-thatoftheproximatesubject，notof
thewholeanimal？Shallwesaythatitisimmobilityofsuchand
suchakind？Yes，buttowhatprocessintheproximatesubjectisthis
due？
Sincesomethingsareandarenot，withoutcomingtobeand
ceasingtobe，e。g。points，iftheycanbesaidtobe，andin
generalformsforitisnot’white’comestobe，butthewoodcomes
tobewhite，ifeverythingthatcomestobecomesfromsomethingand
comestobesomething，notallcontrariescancomefromone
another，butitisindifferentsensesthatapalemancomesfroma
darkman，andpalecomesfromdark。Norhaseverythingmatter，but
onlythosethingswhichcometobeandchangeintooneanother。
Thosethingswhich，withouteverbeingincourseofchanging，areor
arenot，havenomatter。
Thereisdifficultyinthequestionhowthematterofeachthing
isrelatedtoitscontrarystates。E。g。ifthebodyispotentially
healthy，anddiseaseiscontrarytohealth，isitpotentiallyboth
healthyanddiseased？Andiswaterpotentiallywineandvinegar？We
answerthatitisthematterofoneinvirtueofitspositivestate
anditsform，andoftheotherinvirtueoftheprivationofits
positivestateandthecorruptionofitcontrarytoitsnature。It
isalsohardtosaywhywineisnotsaidtobethematterofvinegar
norpotentiallyvinegarthoughvinegarisproducedfromit，and
whyalivingmanisnotsaidtobepotentiallydead。Infactthey
arenot，butthecorruptionsinquestionareaccidental，anditisthe
matteroftheanimalthatisitselfinvirtueofitscorruptionthe
potencyandmatterofacorpse，anditiswaterthatisthematter
ofvinegar。Forthecorpsecomesfromtheanimal，andvinegarfrom
wine，asnightfromday。Andallthethingswhichchangethusintoone
anothermustgobacktotheirmatter；e。g。iffromacorpseis
producedananimal，thecorpsefirstgoesbacktoitsmatter，andonly
thenbecomesananimal；andvinegarfirstgoesbacktowater，andonly
thenbecomeswine。
Toreturntothedifficultywhichhasbeenstatedwithrespect
bothtodefinitionsandtonumbers，whatisthecauseoftheir
unity？Inthecaseofallthingswhichhaveseveralpartsandinwhich
thetotalityisnot，asitwere，amereheap，butthewholeis
somethingbesidetheparts，thereisacause；foreveninbodies
contactisthecauseofunityinsomecases，andinothersviscosity
orsomeothersuchquality。Andadefinitionisasetofwordswhich
isonenotbybeingconnectedtogether，liketheIliad，butbydealing
withoneobject-Whatthen，isitthatmakesmanone；whyisheone
andnotmany，e。g。animalbiped，especiallyifthereare，assome
say，ananimal-itselfandabiped-itself？WhyarenotthoseForms
themselvestheman，sothatmenwouldexistbyparticipationnotin
man，norin-oneForm，butintwo，animalandbiped，andingeneralman
wouldbenotonebutmorethanonething，animalandbiped？
Clearly，then，ifpeopleproceedthusintheirusualmannerof
definitionandspeech，theycannotexplainandsolvethedifficulty。
Butif，aswesay，oneelementismatterandanotherisform，and
oneispotentiallyandtheotheractually，thequestionwillnolonger
bethoughtadifficulty。Forthisdifficultyisthesameaswould
ariseif’roundbronze’werethedefinitionof’cloak’；forthis
wordwouldbeasignofthedefinitoryformula，sothatthequestion
is，whatisthecauseoftheunityof’round’and’bronze’？The
difficultydisappears，becausetheoneismatter，theotherform。
What，then，causesthis-thatwhichwaspotentiallytobe
actually-except，inthecaseofthingswhicharegenerated，theagent？
Forthereisnoothercauseofthepotentialsphere’sbecoming
actuallyasphere，butthiswastheessenceofeither。Ofmatter
someisintelligible，someperceptible，andinaformulathereis
alwaysanelementofmatteraswellasoneofactuality；e。g。the
circleis’aplanefigure’。Butofthethingswhichhavenomatter，
eitherintelligibleorperceptible，eachisbyitsnature
essentiallyakindofunity，asitisessentiallyakindof
being-individualsubstance，quality，orquantityandsoneither
’existent’nor’one’ispresentintheirdefinitions，andtheessence
ofeachofthemisbyitsverynatureakindofunityasitisa
kindofbeing-andsononeofthesehasanyreasonoutsideitself，
forbeingone，norforbeingakindofbeing；foreachisbyits
natureakindofbeingandakindofunity，notasbeinginthe
genus’being’or’one’norinthesensethatbeingandunitycanexist
apartfromparticulars。
Owingtothedifficultyaboutunitysomespeakof’participation’，
andraisethequestion，whatisthecauseofparticipationandwhatis
ittoparticipate；andothersspeakof’communion’，asLycophron
saysknowledgeisacommunionofknowingwiththesoul；andotherssay
lifeisa’composition’or’connexion’ofsoulwithbody。Yetthesame
accountappliestoallcases；forbeinghealthy，too，willonthis
showingbeeithera’communion’ora’connexion’ora’composition’of
soulandhealth，andthefactthatthebronzeisatrianglewillbe
a’composition’ofbronzeandtriangle，andthefactthatathingis
whitewillbea’composition’ofsurfaceandwhiteness。Thereason
isthatpeoplelookforaunifyingformula，andadifference，
betweenpotencyandcompletereality。But，ashasbeensaid，the
proximatematterandtheformareoneandthesamething，theone
potentially，andtheotheractually。Thereforeitislikeasking
whatingeneralisthecauseofunityandofathing’sbeingone；
foreachthingisaunity，andthepotentialandtheactualare
somehowone。Thereforethereisnoothercausehereunlessthereis
somethingwhichcausedthemovementfrompotencyintoactuality。And
allthingswhichhavenomatterarewithoutqualification
essentiallyunities。