Somethingsareonlyactually，somepotentially，some
　　potentiallyandactually，whattheyare，viz。inonecaseaparticular
　　reality，inanother，characterizedbyaparticularquantity，orthe
　　like。Thereisnomovementapartfromthings；forchangeisalways
　　accordingtothecategoriesofbeing，andthereisnothingcommonto
　　theseandinnoonecategory。Buteachofthecategoriesbelongsto
　　allitssubjectsineitheroftwowayse。g。’this-ness’-forone
　　kindofitis’positiveform’，andtheotheris’privation’；andas
　　regardsqualityonekindis’white’andtheother’black’，andas
　　regardsquantityonekindis’complete’andtheother’incomplete’，
　　andasregardsspatialmovementoneis’upwards’andtheother
　　’downwards’，oronethingis’light’andanother’heavy’；sothat
　　thereareasmanykindsofmovementandchangeasofbeing。There
　　beingadistinctionineachclassofthingsbetweenthepotential
　　andthecompletelyreal，Icalltheactualityofthepotentialas
　　such，movement。Thatwhatwesayistrue，isplainfromthe
　　followingfacts。Whenthe’buildable’，insofarasitiswhatwemean
　　by’buildable’，existsactually，itisbeingbuilt，andthisisthe
　　processofbuilding。Similarlywithlearning，healing，walking，
　　leaping，ageing，ripening。Movementtakeswhenthecompletereality
　　itselfexists，andneitherearliernorlater。Thecompletereality，
　　then，ofthatwhichexistspotentially，whenitiscompletelyrealand
　　actual，notquaitself，butquamovable，ismovement。ByquaImean
　　this:bronzeispotentiallyastatue；butyetitisnotthecomplete
　　realityofbronzequabronzethatismovement。Foritisnotthe
　　samethingtobebronzeandtobeacertainpotency。Ifitwere
　　absolutelythesameinitsdefinition，thecompleterealityof
　　bronzewouldhavebeenamovement。Butitisnotthesame。Thisis
　　evidentinthecaseofcontraries；fortobecapableofbeingwelland
　　tobecapableofbeingillarenotthesame-foriftheywere，being
　　wellandbeingillwouldhavebeenthesame-itisthatwhichunderlies
　　andishealthyordiseased，whetheritismoistureorblood，thatis
　　oneandthesame。Andsinceitisnot。thesame，ascolourandthe
　　visiblearenotthesame，itisthecompleterealityofthepotential，
　　andaspotential，thatismovement。Thatitisthis，andthatmovement
　　takesplacewhenthecompleterealityitselfexists，andneither
　　earliernorlater，isevident。Foreachthingiscapableofbeing
　　sometimesactual，sometimesnot，e。g。thebuildablequabuildable；and
　　theactualityofthebuildablequabuildableisbuilding。Forthe
　　actualityiseitherthis-theactofbuilding-orthehouse。Butwhen
　　thehouseexists，itisnolongerbuildable；thebuildableiswhat
　　isbeingbuilt。Theactuality，then，mustbetheactofbuilding，
　　andthisisamovement。Andthesameaccountappliestoallother
　　movements。
　　Thatwhatwehavesaidisrightisevidentfromwhatallothers
　　sayaboutmovement，andfromthefactthatitisnoteasytodefineit
　　otherwise。Forfirstlyonecannotputitinanyclass。Thisisevident
　　fromwhatpeoplesay。Somecallitothernessandinequalityandthe
　　unreal；noneofthese，however，isnecessarilymoved，andfurther，
　　changeisnoteithertotheseorfromtheseanymorethanfromtheir
　　opposites。Thereasonwhypeopleputmovementintheseclassesisthat
　　itisthoughttobesomethingindefinite，andtheprinciplesinoneof
　　thetwo’columnsofcontraries’areindefinitebecausetheyare
　　privative，fornoneofthemiseithera’this’ora’such’orinany
　　oftheothercategories。Andthereasonwhymovementisthoughtto
　　beindefiniteisthatitcannotbeclassedeitherwiththepotency
　　ofthingsorwiththeiractuality；forneitherthatwhichiscapable
　　ofbeingofacertainquantity，northatwhichisactuallyofa
　　certainquantity，isofnecessitymoved，andmovementisthoughttobe
　　anactuality，butincomplete；thereasonisthatthepotential，
　　whoseactualityitis，isincomplete。Andthereforeitishardto
　　graspwhatmovementis；foritmustbeclassedeitherunder
　　privationorunderpotencyorunderabsoluteactuality，but
　　evidentlynoneoftheseispossible。Thereforewhatremainsisthatit
　　mustbewhatwesaid-bothactualityandtheactualitywehave
　　described-whichishardtodetectbutcapableofexisting。
　　Andevidentlymovementisinthemovable；foritisthecomplete
　　realizationofthisbythatwhichiscapableofcausingmovement。
　　Andtheactualityofthatwhichiscapableofcausingmovementisno
　　otherthanthatofthemovable。Foritmustbethecompleterealityof
　　both。Forwhileathingiscapableofcausingmovementbecauseit
　　candothis，itisamoverbecauseitisactive；butitisonthe
　　movablethatitiscapableofacting，sothattheactualityofbothis
　　one，justasthereisthesameintervalfromonetotwoasfromtwoto
　　one，andasthesteepascentandthesteepdescentareone，butthe
　　beingofthemisnotone；thecaseofthemoverandthemovedis
　　similar。
　　Theinfiniteiseitherthatwhichisincapableofbeing
　　traversedbecauseitisnotitsnaturetobetraversedthis
　　correspondstothesenseinwhichthevoiceis’invisible’，orthat
　　whichadmitsonlyofincompletetraverseorscarcelyadmitsof
　　traverse，orthatwhich，thoughitnaturallyadmitsoftraverse，is
　　nottraversedorlimited；further，athingmaybeinfinitein
　　respectofadditionorofsubtraction，orboth。Theinfinitecannotbe
　　aseparate，independentthing。Forifitisneitheraspatial
　　magnitudenoraplurality，butinfinityitselfisitssubstanceand
　　notanaccidentofit，itwillbeindivisible；forthedivisibleis
　　eithermagnitudeorplurality。Butifindivisible，itisnotinfinite，
　　exceptasthevoiceisinvisible；butpeopledonotmeanthis，norare
　　weexaminingthissortofinfinite，buttheinfiniteasuntraversable。
　　Further，howcananinfiniteexistbyitself，unlessnumberand
　　magnitudealsoexistbythemselvess-sinceinfinityisanattribute
　　ofthese？Further，iftheinfiniteisanaccidentofsomethingelse，
　　itcannotbequainfiniteanelementinthings，astheinvisibleis
　　notanelementinspeech，thoughthevoiceisinvisible。Andevidently
　　theinfinitecannotexistactually。Forthenanypartofitthatmight
　　betakenwouldbeinfinitefor’tobeinfinite’and’theinfinite’
　　arethesame，iftheinfiniteissubstanceandnotpredicatedofa
　　subject。Thereforeitiseitherindivisible，orifitispartible，it
　　isdivisibleintoinfinites；butthesamethingcannotbemany
　　infinitesasapartofairisair，soapartoftheinfinitewouldbe
　　infinite，iftheinfiniteissubstanceandaprinciple。Therefore
　　itmustbeimpartibleandindivisible。Buttheactuallyinfinite
　　cannotbeindivisible；foritmustbeofacertainquantity。Therefore
　　infinitybelongstoitssubjectincidentally。Butifso，thenaswe
　　havesaiditcannotbeitthatisaprinciple，butthatofwhichit
　　isanaccident-theairortheevennumber。
　　Thisinquiryisuniversal；butthattheinfiniteisnotamong
　　sensiblethings，isevidentfromthefollowingargument。Ifthe
　　definitionofabodyis’thatwhichisboundedbyplanes’，there
　　cannotbeaninfinitebodyeithersensibleorintelligible；nora
　　separateandinfinitenumber，fornumberorthatwhichhasanumberis
　　numerable。Concretely，thetruthisevidentfromthefollowing
　　argument。Theinfinitecanneitherbecompositenorsimple。Forait
　　cannotbeacompositebody，sincetheelementsarelimitedin
　　multitude。Forthecontrariesmustbeequalandnooneofthemmustbe
　　infinite；forifoneofthetwobodiesfallsatallshortoftheother
　　inpotency，thefinitewillbedestroyedbytheinfinite。Andthat
　　eachshouldbeinfiniteisimpossible。Forbodyisthatwhichhas
　　extensioninalldirections，andtheinfiniteistheboundlessly
　　extended，sothatiftheinfiniteisabodyitwillbeinfinitein
　　everydirection。Norbcantheinfinitebodybeoneand
　　simple-neither，assomesay，somethingapartfromtheelements，from
　　whichtheygeneratetheseforthereisnosuchbodyapartfromthe
　　elements；foreverythingcanberesolvedintothatofwhichit
　　consists，butnosuchproductofanalysisisobservedexceptthe
　　simplebodies，norfirenoranyotheroftheelements。Forapartfrom
　　thequestionhowanyofthemcouldbeinfinite，theAll，evenifitis
　　finite，cannoteitherbeorbecomeanyoneofthem，asHeraclitussays
　　allthingssometimebecomefire。Thesameargumentappliestothis
　　astotheOnewhichthenaturalphilosopherspositbesidesthe
　　elements。Foreverythingchangesfromcontrarytocontrary，e。g。
　　fromhottocold。
　　Further，asensiblebodyissomewhere，andwholeandparthavethe
　　sameproperplace，e。g。thewholeearthandpartoftheearth。
　　Thereforeifatheinfinitebodyishomogeneous，itwillbe
　　unmovableoritwillbealwaysmoving。Butthisisimpossible；forwhy
　　shoulditratherrest，ormove，down，up，oranywhere，ratherthan
　　anywhereelse？E。g。iftherewereaclodwhichwerepartofan
　　infinitebody，wherewillthismoveorrest？Theproperplaceofthe
　　bodywhichishomogeneouswithitisinfinite。Willtheclodoccupy
　　thewholeplace，then？Andhow？Thisisimpossible。Whatthenisits
　　restoritsmovement？Itwilleitherresteverywhere，andthenit
　　cannotmove；oritwillmoveeverywhere，andthenitcannotbe
　　still。ButbiftheAllhasunlikeparts，theproperplacesofthe
　　partsareunlikealso，and，firstly，thebodyoftheAllisnotone
　　exceptbycontact，and，secondly，thepartswillbeeitherfiniteor
　　infiniteinvarietyofkind。Finitetheycannotbe；forthenthose
　　ofonekindwillbeinfiniteinquantityandthoseofanotherwillnot
　　iftheAllisinfinite，e。g。fireorwaterwouldbeinfinite，but
　　suchaninfiniteelementwouldbedestructiontothecontrary
　　elements。Butifthepartsareinfiniteandsimple，theirplaces
　　alsoareinfiniteandtherewillbeaninfinitenumberofelements；
　　andifthisisimpossible，andtheplacesarefinite，theAllalso
　　mustbelimited。
　　Ingeneral，therecannotbeaninfinitebodyandalsoaproper
　　placeforbodies，ifeverysensiblebodyhaseitherweightor
　　lightness。Foritmustmoveeithertowardsthemiddleorupwards，
　　andtheinfiniteeitherthewholeorthehalfofit-cannotdo
　　either；forhowwillyoudivideit？Orhowwillpartoftheinfinite
　　bedownandpartup，orpartextremeandpartmiddle？Further，every
　　sensiblebodyisinaplace，andtherearesixkindsofplace，but
　　thesecannotexistinaninfinitebody。Ingeneral，iftherecannotbe
　　aninfiniteplace，therecannotbeaninfinitebody；andtherecannot
　　beaninfiniteplace，forthatwhichisinaplaceissomewhere，
　　andthismeanseitherupordownorinoneoftheotherdirections，
　　andeachoftheseisalimit。
　　Theinfiniteisnotthesameinthesensethatitisasingle
　　thingwhetherexhibitedindistanceorinmovementorintime，butthe
　　posterioramongtheseiscalledinfiniteinvirtueofitsrelation
　　totheprior；i。e。amovementiscalledinfiniteinvirtueofthe
　　distancecoveredbythespatialmovementoralterationorgrowth，
　　andatimeiscalledinfinitebecauseofthemovementwhichoccupies
　　it。