Ofthingswhichchange，somechangeinanaccidentalsense，like
thatinwhich’themusical’maybesaidtowalk，andothersare
said，withoutqualification，tochange，becausesomethinginthem
changes，i。e。thethingsthatchangeinparts；thebodybecomes
healthy，becausetheeyedoes。Butthereissomethingwhichisby
itsownnaturemoveddirectly，andthisistheessentiallymovable。
Thesamedistinctionisfoundinthecaseofthemover；forit
causesmovementeitherinanaccidentalsenseorinrespectofa
partofitselforessentially。Thereissomethingthatdirectlycauses
movement；andthereissomethingthatismoved，alsothetimeinwhich
itismoved，andthatfromwhichandthatintowhichitismoved。
Buttheformsandtheaffectionsandtheplace，whicharethe
terminalsofthemovementofmovingthings，areunmovable，e。g。
knowledgeorheat；itisnotheatthatisamovement，butheating。
Changewhichisnotaccidentalisfoundnotinallthings，butbetween
contraries，andtheirintermediates，andbetweencontradictories。We
mayconvinceourselvesofthisbyinduction。
Thatwhichchangeschangeseitherfrompositiveintopositive，
orfromnegativeintonegative，orfrompositiveintonegative，or
fromnegativeintopositive。BypositiveImeanthatwhichis
expressedbyanaffirmativeterm。Thereforetheremustbethree
changes；thatfromnegativeintonegativeisnotchange，because
sincethetermsareneithercontrariesnorcontradictoriesthere
isnoopposition。Thechangefromthenegativeintothepositivewhich
isitscontradictoryisgeneration-absolutechangeabsolute
generation，andpartialchangepartialgeneration；andthechangefrom
positivetonegativeisdestruction-absolutechangeabsolute
destruction，andpartialchangepartialdestruction。If，then，’that
whichisnot’hasseveralsenses，andmovementcanattachneitherto
thatwhichimpliesputtingtogetherorseparating，nortothatwhich
impliespotencyandisopposedtothatwhichisinthefullsense
true，thenot-whiteornot-goodcanbemovedincidentally，forthe
not-whitemightbeaman；butthatwhichisnotaparticularthing
atallcaninnowisebemoved，thatwhichisnotcannotbemoved
andifthisisso，generationcannotbemovement；forthatwhichis
notisgenerated；forevenifweadmittothefullthatitsgeneration
isaccidental，yetitistruetosaythat’not-being’ispredicableof
thatwhichisgeneratedabsolutely。Similarlyrestcannotbelong
tothatwhichisnot。Theseconsequences，then，turnouttobe
awkward，andalsothis，thateverythingthatismovedisinaplace，
butthatwhichisnotisnotinaplace；forthenitwouldbe
somewhere。Norisdestructionmovement；forthecontraryofmovement
isrest，butthecontraryofdestructionisgeneration。Sinceevery
movementisachange，andthekindsofchangearethethreenamed
above，andofthesethoseinthewayofgenerationanddestructionare
notmovements，andthesearethechangesfromathingtoits
contradictory，itfollowsthatonlythechangefrompositiveinto
positiveismovement。Andthepositivesareeithercontraryor
intermediateforevenprivationmustberegardedascontrary，and
areexpressedbyanaffirmativeterm，e。g。’naked’or’toothless’or
Ifthecategoriesareclassifiedassubstance，quality，place，
actingorbeingactedon，relation，quantity，theremustbethree
kindsofmovement-ofquality，ofquantity，ofplace。Thereisno
movementinrespectofsubstancebecausethereisnothingcontraryto
substance，norofrelationforitispossiblethatifoneoftwo
thingsinrelationchanges，therelativetermwhichwastrueofthe
otherthingceasestobetrue，thoughthisotherdoesnotchangeat
all，-sothattheirmovementisaccidental，norofagentand
patient，ormoverandmoved，becausethereisnomovementof
movementnorgenerationofgeneration，nor，ingeneral，changeof
change。Fortheremightbemovementofmovementintwosenses；1
movementmightbethesubjectmoved，asamanismovedbecausehe
changesfrompaletodark，-sothatonthisshowingmovement，too，
maybeeitherheatedorcooledorchangeitsplaceorincrease。But
thisisimpossible；forchangeisnotasubject。Or2someother
subjectmightchangefromchangeintosomeotherformofexistence
e。g。amanfromdiseaseintohealth。Butthisalsoisnotpossible
exceptincidentally。Foreverymovementischangefromsomething
intosomething。Andsoaregenerationanddestruction；only，these
arechangesintothingsopposedincertainwayswhiletheother，
movement，isintothingsopposedinanotherway。Athingchanges，
then，atthesametimefromhealthintoillness，andfromthis
changeitselfintoanother。Clearly，then，ifithasbecomeill，it
willhavechangedintowhatevermaybetheotherchangeconcerned
thoughitmaybeatrest，and，further，intoadeterminatechange
eachtime；andthatnewchangewillbefromsomethingdefiniteinto
someotherdefinitething；thereforeitwillbetheoppositechange，
thatofgrowingwell。Weanswerthatthishappensonlyincidentally；
e。g。thereisachangefromtheprocessofrecollectiontothatof
forgetting，onlybecausethattowhichtheprocessattachesis
changing，nowintoastateofknowledge，nowintooneofignorance。
Further，theprocesswillgoontoinfinity，ifthereistobe
changeofchangeandcomingtobeofcomingtobe。Whatistrueofthe
later，then，mustbetrueoftheearlier；e。g。ifthesimplecomingto
bewasoncecomingtobe，thatwhichcomestobesomethingwasalso
oncecomingtobe；thereforethatwhichsimplycomestobesomething
wasnotyetinexistence，butsomethingwhichwascomingtobe
comingtobesomethingwasalreadyinexistence。Andthiswasonce
comingtobe，sothatatthattimeitwasnotyetcomingtobe
somethingelse。Nowsinceofaninfinitenumberoftermsthereis
notafirst，thefirstinthisserieswillnotexist，andthereforeno
followingtermexist。Nothing，then，caneithercometermwitobe
ormoveorchange。Further，thatwhichiscapableofamovementis
alsocapableofthecontrarymovementandrest，andthatwhichcomes
tobealsoceasestobe。Thereforethatwhichiscomingtobeis
ceasingtobewhenithascometobecomingtobe；foritcannotcease
tobeassoonasitiscomingtobecomingtobe，norafterithas
cometobe；forthatwhichisceasingtobemustbe。Further，there
mustbeamatterunderlyingthatwhichcomestobeandchanges。What
willthisbe，then，-whatisitthatbecomesmovementorbecoming，as
bodyorsoulisthatwhichsuffersalteration？And；again，whatis
itthattheymoveinto？Foritmustbethemovementorbecomingof
somethingfromsomethingintosomething。How，then，canthiscondition
befulfilled？Therecanbenolearningoflearning，andthereforeno
becomingofbecoming。Sincethereisnotmovementeitherof
substanceorofrelationorofactivityandpassivity，itremainsthat
movementisinrespectofqualityandquantityandplace；foreach
oftheseadmitsofcontrariety。ByqualityImeannotthatwhichisin
thesubstanceforeventhedifferentiaisaquality，butthepassive
quality，invirtueofwhichathingissaidtobeactedonortobe
incapableofbeingactedon。Theimmobileiseitherthatwhichis
whollyincapableofbeingmoved，orthatwhichismovedwith
difficultyinalongtimeorbeginsslowly，orthatwhichisofa
naturetobemovedandcanbemovedbutisnotmovedwhenandwhere
andasitwouldnaturallybemoved。ThisaloneamongimmobilesI
describeasbeingatrest；forrestiscontrarytomovement，sothat
itmustbeaprivationinthatwhichisreceptiveofmovement。
Thingswhichareinoneproximateplacearetogetherinplace，and
thingswhichareindifferentplacesareapart:thingswhose
extremesaretogethertouch:thatatwhichachangingthing，ifit
changescontinuouslyaccordingtoitsnature，naturallyarrivesbefore
itarrivesattheextremeintowhichitischanging，isbetween。
Thatwhichismostdistantinastraightlineiscontraryinplace。
Thatissuccessivewhichisafterthebeginningtheorderbeing
determinedbypositionorformorinsomeotherwayandhasnothing
ofthesameclassbetweenitandthatwhichitsucceeds，e。g。linesin
thecaseofaline，unitsinthatofaunit，orahouseinthatofa
house。Thereisnothingtopreventathingofsomeotherclassfrom
beingbetween。Forthesuccessivesucceedssomethingandissomething
later；’one’doesnotsucceed’two’，northefirstdayofthemonth
thesecond。Thatwhich，beingsuccessive，touches，iscontiguous。
Sinceallchangeisbetweenopposites，andtheseareeither
contrariesorcontradictories，andthereisnomiddletermfor
contradictories，clearlythatwhichisbetweenisbetweencontraries。
Thecontinuousisaspeciesofthecontiguous。Icalltwothings
continuouswhenthelimitsofeach，withwhichtheytouchandbywhich
theyarekepttogether，becomeoneandthesame，sothatplainlythe
continuousisfoundinthethingsoutofwhichaunitynaturally
arisesinvirtueoftheircontact。Andplainlythesuccessiveisthe
firstoftheseconceptsforthesuccessivedoesnotnecessarily
touch，butthatwhichtouchesissuccessive；andifathingis
continuous，ittouches，butifittouches，itisnotnecessarily
continuous；andinthingsinwhichthereisnotouching，thereisno
organicunity；thereforeapointisnotthesameasaunit；for
contactbelongstopoints，butnottounits，whichhaveonly
succession；andthereissomethingbetweentwooftheformer，but
notbetweentwoofthelatter。
Thesubjectofourinquiryissubstance；fortheprinciplesand
thecausesweareseekingarethoseofsubstances。Foriftheuniverse
isofthenatureofawhole，substanceisitsfirstpart；andifit
coheresmerelybyvirtueofserialsuccession，onthisviewalso
substanceisfirst，andissucceededbyquality，andthenbyquantity。
Atthesametimetheselatterarenotevenbeinginthefullsense，
butarequalitiesandmovementsofit，-orelseeventhenot-white
andthenot-straightwouldbebeing；atleastwesayeventheseare，
e。g。’thereisanot-white’。Further，noneofthecategoriesother
thansubstancecanexistapart。Andtheearlyphilosophersalsoin
practicetestifytotheprimacyofsubstance；foritwasof
substancethattheysoughttheprinciplesandelementsandcauses。The
thinkersofthepresentdaytendtorankuniversalsassubstancesfor
generaareuniversals，andthesetheytendtodescribeasprinciples
andsubstances，owingtotheabstractnatureoftheirinquiry；but
thethinkersofoldrankedparticularthingsassubstances，e。g。
fireandearth，notwhatiscommontoboth，body。
Therearethreekindsofsubstance-onethatissensibleof
whichonesubdivisioniseternalandanotherisperishable；thelatter
isrecognizedbyallmen，andincludese。g。plantsandanimals，of
whichwemustgrasptheelements，whetheroneormany；andanother
thatisimmovable，andthiscertainthinkersasserttobecapableof
existingapart，somedividingitintotwo，othersidentifyingthe
Formsandtheobjectsofmathematics，andotherspositing，ofthese
two，onlytheobjectsofmathematics。Theformertwokindsof
substancearethesubjectofphysicsfortheyimplymovement；but
thethirdkindbelongstoanotherscience，ifthereisnoprinciple
commontoitandtotheotherkinds。