Asallpotenciesareeitherinnate，likethesenses，orcomeby
practice，likethepowerofplayingtheflute，orbylearning，like
artisticpower，thosewhichcomebypracticeorbyrationalformulawe
mustacquirebypreviousexercisebutthisisnotnecessarywiththose
whicharenotofthisnatureandwhichimplypassivity。
Sincethatwhichis’capable’iscapableofsomethingandat
sometimeinsomewaywithalltheotherqualificationswhichmustbe
presentinthedefinition，andsincesomethingscanproducechange
accordingtoarationalformulaandtheirpotenciesinvolvesucha
formula，whileotherthingsarenonrationalandtheirpotenciesare
non-rational，andtheformerpotenciesmustbeinalivingthing，
whilethelattercanbebothinthelivingandinthelifeless；as
regardspotenciesofthelatterkind，whentheagentandthepatient
meetinthewayappropriatetothepotencyinquestion，theonemust
actandtheotherbeactedon，butwiththeformerkindofpotency
thisisnotnecessary。Forthenonrationalpotenciesareall
productiveofoneeffecteach，buttherationalproducecontrary
effects，sothatiftheyproducedtheireffectsnecessarilytheywould
producecontraryeffectsatthesametime；butthisisimpossible。
Theremust，then，besomethingelsethatdecides；Imeanbythis，
desireorwill。Forwhicheveroftwothingstheanimaldesires
decisively，itwilldo，whenitispresent，andmeetsthepassive
object，inthewayappropriatetothepotencyinquestion。Therefore
everythingwhichhasarationalpotency，whenitdesiresthatfor
whichithasapotencyandinthecircumstancesinwhichithasthe
potency，mustdothis。Andithasthepotencyinquestionwhenthe
passiveobjectispresentandisinacertainstate；ifnotitwill
notbeabletoact。Toaddthequalification’ifnothingexternal
preventsit’isnotfurthernecessary；forithasthepotencyonthe
termsonwhichthisisapotencyofacting，anditisthisnotin
allcircumstancesbutoncertainconditions，amongwhichwillbethe
exclusionofexternalhindrances；forthesearebarredbysomeof
thepositivequalifications。Andsoevenifonehasarational
wish，oranappetite，todotwothingsorcontrarythingsatthe
sametime，onewillnotdothem；foritisnotonthesetermsthatone
hasthepotencyforthem，norisitapotencyofdoingbothatthe
sametime，sinceonewilldothethingswhichitisapotencyof
doing，onthetermsonwhichonehasthepotency。
Sincewehavetreatedofthekindofpotencywhichisrelatedto
movement，letusdiscussactuality-what，andwhatkindofthing，
actualityis。Forinthecourseofouranalysisitwillalsobecome
clear，withregardtothepotential，thatwenotonlyascribe
potencytothatwhosenatureitistomovesomethingelse，ortobe
movedbysomethingelse，eitherwithoutqualificationorinsome
particularway，butalsousethewordinanothersense，whichisthe
reasonoftheinquiryinthecourseofwhichwehavediscussedthese
previoussensesalso。Actuality，then，istheexistenceofathingnot
inthewaywhichweexpressby’potentially’；wesaythatpotentially，
forinstance，astatueofHermesisintheblockofwoodandthe
half-lineisinthewhole，becauseitmightbeseparatedout，andwe
calleventhemanwhoisnotstudyingamanofscience，ifheis
capableofstudying；thethingthatstandsincontrasttoeachof
theseexistsactually。Ourmeaningcanbeseenintheparticularcases
byinduction，andwemustnotseekadefinitionofeverythingbutbe
contenttograsptheanalogy，thatitisasthatwhichisbuilding
istothatwhichiscapableofbuilding，andthewakingtothe
sleeping，andthatwhichisseeingtothatwhichhasitseyesshutbut
hassight，andthatwhichhasbeenshapedoutofthemattertothe
matter，andthatwhichhasbeenwroughtuptotheunwrought。Let
actualitybedefinedbyonememberofthisantithesis，andthe
potentialbytheother。Butallthingsarenotsaidinthesame
sensetoexistactually，butonlybyanalogy-asAisinBortoB，C
isinDortoD；forsomeareasmovementtopotency，andtheothers
assubstancetosomesortofmatter。
Butalsotheinfiniteandthevoidandallsimilarthingsaresaid
toexistpotentiallyandactuallyinadifferentsensefromthatwhich
appliestomanyotherthings，e。g。tothatwhichseesorwalksoris
seen。Forofthelatterclassthesepredicatescanatsometimebe
alsotrulyassertedwithoutqualification；fortheseenissocalled
sometimesbecauseitisbeingseen，sometimesbecauseitiscapableof
beingseen。Buttheinfinitedoesnotexistpotentiallyinthesense
thatitwilleveractuallyhaveseparateexistence；itexists
potentiallyonlyforknowledge。Forthefactthattheprocessof
dividingnevercomestoanendensuresthatthisactivityexists
potentially，butnotthattheinfiniteexistsseparately。
Sinceoftheactionswhichhavealimitnoneisanendbutallare
relativetotheend，e。g。theremovingoffat，orfat-removal，andthe
bodilypartsthemselveswhenoneismakingthemthinareinmovement
inthiswayi。e。withoutbeingalreadythatatwhichthemovement
aims，thisisnotanactionoratleastnotacompleteoneforitis
notanend；butthatmovementinwhichtheendispresentisan
action。E。g。atthesametimeweareseeingandhaveseen，are
understandingandhaveunderstood，arethinkingandhavethought
whileitisnottruethatatthesametimewearelearningandhave
learnt，orarebeingcuredandhavebeencured。Atthesametimewe
arelivingwellandhavelivedwell，andarehappyandhavebeen
happy。Ifnot，theprocesswouldhavehadsometimetocease，asthe
processofmakingthinceases:but，asthingsare，itdoesnot
cease；wearelivingandhavelived。Oftheseprocesses，then，wemust
calltheonesetmovements，andtheotheractualities。Forevery
movementisincomplete-makingthin，learning，walking，building；these
aremovements，andincompleteatthat。Foritisnottruethatat
thesametimeathingiswalkingandhaswalked，orisbuildingand
hasbuilt，oriscomingtobeandhascometobe，orisbeingmoved
andhasbeenmoved，butwhatisbeingmovedisdifferentfromwhathas
beenmoved，andwhatismovingfromwhathasmoved。Butitisthesame
thingthatatthesametimehasseenandisseeing，seeing，oris
thinkingandhasthought。Thelattersortofprocess，then，Icall
anactuality，andtheformeramovement。
What，andwhatkindofthing，theactualis，maybetakenas
explainedbytheseandsimilarconsiderations。Butwemustdistinguish
whenathingexistspotentiallyandwhenitdoesnot；foritisnotat
anyandeverytime。E。g。isearthpotentiallyaman？No-butrather
whenithasalreadybecomeseed，andperhapsnoteventhen。Itisjust
asitiswithbeinghealed；noteverythingcanbehealedbythe
medicalartorbyluck，butthereisacertainkindofthingwhich
iscapableofit，andonlythisispotentiallyhealthy。And1the
delimitingmarkofthatwhichasaresultofthoughtcomestoexistin
completerealityfromhavingexistedpotentiallyisthatifthe
agenthaswilledititcomestopassifnothingexternalhinders，
whiletheconditionontheotherside-viz。inthatwhichis
healed-isthatnothinginithinderstheresult。Itisonsimilar
termsthatwehavewhatispotentiallyahouse；ifnothinginthe
thingactedon-i。e。inthematter-preventsitfrombecomingahouse，
andifthereisnothingwhichmustbeaddedortakenawayor
changed，thisispotentiallyahouse；andthesameistrueofall
otherthingsthesourceofwhosebecomingisexternal。And2in
thecasesinwhichthesourceofthebecomingisintheverything
whichcomestobe，athingispotentiallyallthosethingswhichit
willbeofitselfifnothingexternalhindersit。E。g。theseedisnot
yetpotentiallyaman；foritmustbedepositedinsomethingother
thanitselfandundergoachange。Butwhenthroughitsownmotive
principleithasalreadygotsuchandsuchattributes，inthisstate
itisalreadypotentiallyaman；whileintheformerstateitneeds
anothermotiveprinciple，justasearthisnotyetpotentiallya
statueforitmustfirstchangeinordertobecomebrass。
Itseemsthatwhenwecallathingnotsomethingelsebut
’thaten’-e。g。acasketisnot’wood’but’wooden’，andwoodisnot
’earth’but’earthen’，andagainearthwillillustrateourpointifit
issimilarlynotsomethingelsebut’thaten’-thatotherthingis
alwayspotentiallyinthefullsenseofthatwordthethingwhich
comesafteritinthisseries。E。g。acasketisnot’earthen’nor
’earth’，but’wooden’；forthisispotentiallyacasketandthisis
thematterofacasket，woodingeneralofacasketingeneral，and
thisparticularwoodofthisparticularcasket。Andifthereisa
firstthing，whichisnolonger，inreferencetosomethingelse，
called’thaten’，thisisprimematter；e。g。ifearthis’airy’andair
isnot’fire’but’fiery’，fireisprimematter，whichisnota
’this’。Forthesubjectorsubstratumisdifferentiatedbybeinga
’this’ornotbeingone；i。e。thesubstratumofmodificationsis，e。g。
aman，i。e。abodyandasoul，whilethemodificationis’musical’
or’pale’。Thesubjectiscalled，whenmusiccomestobepresentin
it，not’music’but’musical’，andthemanisnot’paleness’but
’pale’，andnot’ambulation’or’movement’but’walking’or
’moving’，-whichisakintothe’thaten’。Whereverthisisso，then，
theultimatesubjectisasubstance；butwhenthisisnotsobutthe
predicateisaformanda’this’，theultimatesubjectismatterand
materialsubstance。Anditisonlyrightthat’thaten’shouldbe
usedwithreferencebothtothematterandtotheaccidents；for
bothareindeterminates。
Wehavestated，then，whenathingistobesaidtoexist
potentiallyandwhenitisnot。
Fromourdiscussionofthevarioussensesof’prior’，itis
clearthatactualityispriortopotency。AndImeanbypotencynot
onlythatdefinitekindwhichissaidtobeaprincipleofchangein
anotherthingorinthethingitselfregardedasother，butingeneral
everyprincipleofmovementorofrest。Fornaturealsoisinthesame
genusaspotency；foritisaprincipleofmovement-not，however，in
somethingelsebutinthethingitselfquaitself。Toallsuch
potency，then，actualityispriorbothinformulaandin
substantiality；andintimeitispriorinonesense，andinanother
not。
1Clearlyitispriorinformula；forthatwhichisinthe
primarysensepotentialispotentialbecauseitispossibleforit
tobecomeactive；e。g。Imeanby’capableofbuilding’thatwhich
canbuild，andby’capableofseeing’thatwhichcansee，andby
’visible’thatwhichcanbeseen。Andthesameaccountappliesto
allothercases，sothattheformulaandtheknowledgeoftheonemust
precedetheknowledgeoftheother。
2Intimeitispriorinthissense:theactualwhichis
identicalinspeciesthoughnotinnumberwithapotentially
existingthingistoit。Imeanthattothisparticularmanwhonow
existsactuallyandtothecornandtotheseeingsubjectthematter
andtheseedandthatwhichiscapableofseeing，whichare
potentiallyamanandcornandseeing，butnotyetactuallyso，are
priorintime；butpriorintimetotheseareotheractually
existingthings，fromwhichtheywereproduced。Forfromthe
potentiallyexistingtheactuallyexistingisalwaysproducedbyan
actuallyexistingthing，e。g。manfromman，musicianbymusician；
thereisalwaysafirstmover，andthemoveralreadyexists
actually。Wehavesaidinouraccountofsubstancethateverything
thatisproducedissomethingproducedfromsomethingandby
something，andthatthesameinspeciesasit。
Thisiswhyitisthoughtimpossibletobeabuilderifonehas
builtnothingoraharperifonehasneverplayedtheharp；forhewho
learnstoplaytheharplearnstoplayitbyplayingit，andallother
learnersdosimilarly。Andthencearosethesophisticalquibble，
thatonewhodoesnotpossessasciencewillbedoingthatwhichis
theobjectofthescience；forhewhoislearningitdoesnot
possessit。Butsince，ofthatwhichiscomingtobe，somepartmust
havecometobe，and，ofthatwhich，ingeneral，ischanging，some
partmusthavechangedthisisshowninthetreatiseonmovement，he
whoislearningmust，itwouldseem，possesssomepartofthescience。
Butheretoo，then，itisclearthatactualityisinthissense
also，viz。inorderofgenerationandoftime，priortopotency。
But3itisalsopriorinsubstantiality；firstly，abecause
thethingsthatareposteriorinbecomingarepriorinformandin
substantialitye。g。manispriortoboyandhumanbeingtoseed；
fortheonealreadyhasitsform，andtheotherhasnot，and
becauseeverythingthatcomestobemovestowardsaprinciple，i。e。an
endforthatforthesakeofwhichathingis，isitsprinciple，
andthebecomingisforthesakeoftheend，andtheactualityisthe
end，anditisforthesakeofthisthatthepotencyisacquired。
Foranimalsdonotseeinorderthattheymayhavesight，butthey