’Potency’means1asourceofmovementorchange，whichisin
　　anotherthingthanthethingmovedorinthesamethingquaother；
　　e。g。theartofbuildingisapotencywhichisnotinthethingbuilt，
　　whiletheartofhealing，whichisapotency，maybeintheman
　　healed，butnotinhimquahealed。’Potency’thenmeansthesource，in
　　general，ofchangeormovementinanotherthingorinthesamething
　　quaother，andalso2thesourceofathing’sbeingmovedbyanother
　　thingorbyitselfquaother。Forinvirtueofthatprinciple，in
　　virtueofwhichapatientsuffersanything，wecallit’capable’of
　　suffering；andthiswedosometimesifitsuffersanythingatall，
　　sometimesnotinrespectofeverythingitsuffers，butonlyifit
　　suffersachangeforthebetter——3Thecapacityofperformingthis
　　welloraccordingtointention；forsometimeswesayofthosewho
　　merelycanwalkorspeakbutnotwellornotastheyintend，thatthey
　　cannotspeakorwalk。Sotoo4inthecaseofpassivity——5The
　　statesinvirtueofwhichthingsareabsolutelyimpassiveor
　　unchangeable，ornoteasilychangedfortheworse，arecalled
　　potencies；forthingsarebrokenandcrushedandbentandingeneral
　　destroyednotbyhavingapotencybutbynothavingoneandbylacking
　　something，andthingsareimpassivewithrespecttosuchprocesses
　　iftheyarescarcelyandslightlyaffectedbythem，becauseofa
　　’potency’andbecausethey’can’dosomethingandareinsomepositive
　　state。
　　’Potency’havingthisvarietyofmeanings，sotoothe’potent’
　　or’capable’inonesensewillmeanthatwhichcanbeginamovement
　　orachangeingeneral，foreventhatwhichcanbringthingsto
　　restisa’potent’thinginanotherthingorinitselfquaother；and
　　inonesensethatoverwhichsomethingelsehassuchapotency；andin
　　onesensethatwhichhasapotencyofchangingintosomething，whether
　　fortheworseorforthebetterforeventhatwhichperishesis
　　thoughttobe’capable’ofperishing，foritwouldnothaveperished
　　ifithadnotbeencapableofit；but，asamatteroffact，ithasa
　　certaindispositionandcauseandprinciplewhichfitsittosuffer
　　this；sometimesitisthoughttobeofthissortbecauseithas
　　something，sometimesbecauseitisdeprivedofsomething；butif
　　privationisinasense’having’or’habit’，everythingwillbe
　　capablebyhavingsomething，sothatthingsarecapablebothbyhaving
　　apositivehabitandprinciple，andbyhavingtheprivationofthis，
　　ifitispossibletohaveaprivation；andifprivationisnotina
　　sense’habit’，’capable’isusedintwodistinctsenses；anda
　　thingiscapableinanothersensebecauseneitheranyotherthing，nor
　　itselfquaother，hasapotencyorprinciplewhichcandestroyit。
　　Again，allofthesearecapableeithermerelybecausethething
　　mightchancetohappenornottohappen，orbecauseitmightdoso
　　well。Thissortofpotencyisfoundeveninlifelessthings，e。g。in
　　instruments；forwesayonelyrecanspeak，andanothercannotspeak
　　atall，ifithasnotagoodtone。
　　Incapacityisprivationofcapacity-i。e。ofsuchaprincipleas
　　hasbeendescribedeitheringeneralorinthecaseofsomething
　　thatwouldnaturallyhavethecapacity，orevenatthetimewhenit
　　wouldnaturallyalreadyhaveit；forthesensesinwhichweshould
　　callaboyandamanandaeunuch’incapableofbegetting’are
　　distinct-Again，toeitherkindofcapacitythereisanopposite
　　incapacity-bothtothatwhichonlycanproducemovementandtothat
　　whichcanproduceitwell。
　　Somethings，then，arecalledadunatainvirtueofthiskindof
　　incapacity，whileothersaresoinanothersense；i。e。bothdunaton
　　andadunatonareusedasfollows。Theimpossibleisthatofwhich
　　thecontraryisofnecessitytrue，e。g。thatthediagonalofa
　　squareiscommensuratewiththesideisimpossible，becausesucha
　　statementisafalsityofwhichthecontraryisnotonlytruebutalso
　　necessary；thatitiscommensurate，then，isnotonlyfalsebutalso
　　ofnecessityfalse。Thecontraryofthis，thepossible，isfound
　　whenitisnotnecessarythatthecontraryisfalse，e。g。thataman
　　shouldbeseatedispossible；forthatheisnotseatedisnotof
　　necessityfalse。Thepossible，then，inonesense，ashasbeensaid，
　　meansthatwhichisnotofnecessityfalse；inone，thatwhichis
　　true；inone，thatwhichmaybetrue-A’potency’or’power’in
　　geometryissocalledbyachangeofmeaning-Thesesensesof
　　’capable’or’possible’involvenoreferencetopotency。Butthe
　　senseswhichinvolveareferencetopotencyallrefertotheprimary
　　kindofpotency；andthisisasourceofchangeinanotherthingorin
　　thesamethingquaother。Forotherthingsarecalled’capable’，
　　somebecausesomethingelsehassuchapotencyoverthem，somebecause
　　ithasnot，somebecauseithasitinaparticularway。Thesameis
　　trueofthethingsthatareincapable。Thereforetheproperdefinition
　　oftheprimarykindofpotencywillbe’asourceofchangein
　　anotherthingorinthesamethingquaother’。
　　’Quantum’meansthatwhichisdivisibleintotwoormore
　　constituentpartsofwhicheachisbynaturea’one’anda’this’。A
　　quantumisapluralityifitisnumerable，amagnitudeifitisa
　　measurable。’Plurality’meansthatwhichisdivisiblepotentiallyinto
　　non-continuousparts，’magnitude’thatwhichisdivisibleinto
　　continuousparts；ofmagnitude，thatwhichiscontinuousinone
　　dimensionislength；intwobreadth，inthreedepth。Ofthese，limited
　　pluralityisnumber，limitedlengthisaline，breadthasurface，
　　depthasolid。
　　Again，somethingsarecalledquantainvirtueoftheirown
　　nature，othersincidentally；e。g。thelineisaquantumbyitsown
　　nature，themusicalisoneincidentally。Ofthethingsthatarequanta
　　bytheirownnaturesomearesoassubstances，e。g。thelineisa
　　quantumfor’acertainkindofquantum’ispresentinthe
　　definitionwhichstateswhatitis，andothersaremodifications
　　andstatesofthiskindofsubstance，e。g。muchandlittle，longand
　　short，broadandnarrow，deepandshallow，heavyandlight，andall
　　othersuchattributes。Andalsogreatandsmall，andgreaterand
　　smaller，bothinthemselvesandwhentakenrelativelytoeachother，
　　arebytheirownnatureattributesofwhatisquantitative；but
　　thesenamesaretransferredtootherthingsalso。Ofthingsthatare
　　quantaincidentally，somearesocalledinthesenseinwhichitwas
　　saidthatthemusicalandthewhitewerequanta，viz。becausethat
　　towhichmusicalnessandwhitenessbelongisaquantum，andsomeare
　　quantainthewayinwhichmovementandtimeareso；forthesealso
　　arecalledquantaofasortandcontinuousbecausethethingsofwhich
　　theseareattributesaredivisible。Imeannotthatwhichismoved，
　　butthespacethroughwhichitismoved；forbecausethatisaquantum
　　movementalsoisaquantum，andbecausethisisaquantumtimeisone。
　　’Quality’means1thedifferentiaoftheessence，e。g。manisan
　　animalofacertainqualitybecauseheistwo-footed，andthehorseis
　　sobecauseitisfour-footed；andacircleisafigureofparticular
　　qualitybecauseitiswithoutangles，-whichshowsthattheessential
　　differentiaisaquality-This，then，isonemeaningofquality-the
　　differentiaoftheessence，but2thereisanothersenseinwhichit
　　appliestotheunmovableobjectsofmathematics，thesenseinwhich
　　thenumbershaveacertainquality，e。g。thecompositenumberswhich
　　arenotinonedimensiononly，butofwhichtheplaneandthesolid
　　arecopiesthesearethosewhichhavetwoorthreefactors；andin
　　generalthatwhichexistsintheessenceofnumbersbesidesquantity
　　isquality；fortheessenceofeachiswhatitisonce，e。g。thatof
　　isnotwhatitistwiceorthrice，butwhatitisonce；for6is
　　once6。
　　3Allthemodificationsofsubstancesthatmovee。g。heatand
　　cold，whitenessandblackness，heavinessandlightness，andtheothers
　　ofthesortinvirtueofwhich，whentheychange，bodiesaresaid
　　toalter。4Qualityinrespectofvirtueandvice，andingeneral，
　　ofevilandgood。
　　Quality，then，seemstohavepracticallytwomeanings，andone
　　oftheseisthemoreproper。Theprimaryqualityisthedifferentiaof
　　theessence，andofthisthequalityinnumbersisapart；foritisa
　　differentiaofessences，buteithernotofthingsthatmoveornot
　　ofthemquamoving。Secondly，therearethemodificationsofthings
　　thatmove，quamoving，andthedifferentiaeofmovements。Virtueand
　　vicefallamongthesemodifications；fortheyindicatedifferentiaeof
　　themovementoractivity，accordingtowhichthethingsinmotion
　　actorareactedonwellorbadly；forthatwhichcanbemovedor
　　actinonewayisgood，andthatwhichcandosoinanother——the
　　contrary——wayisvicious。Goodandevilindicatequalityespeciallyin
　　livingthings，andamongtheseespeciallyinthosewhichhavepurpose。
　　Thingsare’relative’1asdoubletohalf，andtrebletoa
　　third，andingeneralthatwhichcontainssomethingelsemanytimesto
　　thatwhichiscontainedmanytimesinsomethingelse，andthatwhich
　　exceedstothatwhichisexceeded；2asthatwhichcanheatto
　　thatwhichcanbeheated，andthatwhichcancuttothatwhichcan
　　becut，andingeneraltheactivetothepassive；3asthe
　　measurabletothemeasure，andtheknowabletoknowledge，andthe
　　perceptibletoperception。
　　1Relativetermsofthefirstkindarenumericallyrelated
　　eitherindefinitelyordefinitely，tonumbersthemselvesorto1。E。g。
　　thedoubleisinadefinitenumericalrelationto1，andthatwhichis
　　’manytimesasgreat’isinanumerical，butnotadefinite，
　　relationto1，i。e。notinthisorinthatnumericalrelationtoit；
　　therelationofthatwhichishalfasbigagainassomethingelseto
　　thatsomethingisadefinitenumericalrelationtoanumber；that
　　whichisnI/ntimessomethingelseisinanindefiniterelationto
　　thatsomething，asthatwhichis’manytimesasgreat’isinan
　　indefiniterelationto1；therelationofthatwhichexceedstothat
　　whichisexceededisnumericallyquiteindefinite；fornumberis
　　alwayscommensurate，and’number’isnotpredicatedofthatwhichis
　　notcommensurate，butthatwhichexceedsis，inrelationtothatwhich
　　isexceeded，somuchandsomethingmore；andthissomethingis
　　indefinite；foritcan，indifferently，beeitherequalornotequalto
　　thatwhichisexceeded-Alltheserelations，then，arenumerically
　　expressedandaredeterminationsofnumber，andsoinanotherway
　　aretheequalandthelikeandthesame。Forallrefertounity。Those
　　thingsarethesamewhosesubstanceisone；thosearelikewhose
　　qualityisone；thoseareequalwhosequantityisone；and1isthe
　　beginningandmeasureofnumber，sothatalltheserelationsimply
　　number，thoughnotinthesameway。
　　2Thingsthatareactiveorpassiveimplyanactiveorapassive
　　potencyandtheactualizationsofthepotencies；e。g。thatwhichis
　　capableofheatingisrelatedtothatwhichiscapableofbeing
　　heated，becauseitcanheatit，and，again，thatwhichheatsis
　　relatedtothatwhichisheatedandthatwhichcutstothatwhichis
　　cut，inthesensethattheyactuallydothesethings。Butnumerical
　　relationsarenotactualizedexceptinthesensewhichhasbeen
　　elsewherestated；actualizationsinthesenseofmovementtheyhave
　　not。Ofrelationswhichimplypotencysomefurtherimplyparticular
　　periodsoftime，e。g。thatwhichhasmadeisrelativetothatwhich
　　hasbeenmade，andthatwhichwillmaketothatwhichwillbemade。
　　Foritisinthiswaythatafatheriscalledthefatherofhisson；
　　fortheonehasactedandtheotherhasbeenactedoninacertain
　　way。Further，somerelativetermsimplyprivationofpotency，i。e。
　　’incapable’andtermsofthissort，e。g。’invisible’。
　　Relativetermswhichimplynumberorpotency，therefore，areall
　　relativebecausetheirveryessenceincludesinitsnatureareference
　　tosomethingelse，notbecausesomethingelseinvolvesareference
　　toit；but3thatwhichismeasurableorknowableorthinkableis
　　calledrelativebecausesomethingelseinvolvesareferencetoit。For
　　’thatwhichisthinkable’impliesthatthethoughtofitis