第17章

’Potency’means(1)asourceofmovementorchange，whichisin

anotherthingthanthethingmovedorinthesamethingquaother；

e。g。theartofbuildingisapotencywhichisnotinthethingbuilt，

whiletheartofhealing，whichisapotency，maybeintheman

healed，butnotinhimquahealed。’Potency’thenmeansthesource，in

general，ofchangeormovementinanotherthingorinthesamething

quaother，andalso(2)thesourceofathing’sbeingmovedbyanother

thingorbyitselfquaother。Forinvirtueofthatprinciple，in

virtueofwhichapatientsuffersanything，wecallit’capable’of

suffering；andthiswedosometimesifitsuffersanythingatall，

sometimesnotinrespectofeverythingitsuffers，butonlyifit

suffersachangeforthebetter——(3)Thecapacityofperformingthis

welloraccordingtointention；forsometimeswesayofthosewho

merelycanwalkorspeakbutnotwellornotastheyintend，thatthey

cannotspeakorwalk。Sotoo(4)inthecaseofpassivity——(5)The

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’thing)inanotherthingorinitselfquaother；and

inonesensethatoverwhichsomethingelsehassuchapotency；andin

onesensethatwhichhasapotencyofchangingintosomething，whether

fortheworseorforthebetter(foreventhatwhichperishesis

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

quantum(for’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’means(1)thedifferentiaoftheessence，e。g。manisan

animalofacertainqualitybecauseheistwo-footed，andthehorseis

sobecauseitisfour-footed；andacircleisafigureofparticular

qualitybecauseitiswithoutangles，-whichshowsthattheessential

differentiaisaquality-This，then，isonemeaningofquality-the

differentiaoftheessence，but(2)thereisanothersenseinwhichit

appliestotheunmovableobjectsofmathematics，thesenseinwhich

thenumbershaveacertainquality，e。g。thecompositenumberswhich

arenotinonedimensiononly，butofwhichtheplaneandthesolid

arecopies(thesearethosewhichhavetwoorthreefactors)；andin

generalthatwhichexistsintheessenceofnumbersbesidesquantity

isquality；fortheessenceofeachiswhatitisonce，e。g。thatof

isnotwhatitistwiceorthrice，butwhatitisonce；for6is

once6。

(3)Allthemodificationsofsubstancesthatmove(e。g。heatand

cold，whitenessandblackness，heavinessandlightness，andtheothers

ofthesort)invirtueofwhich，whentheychange，bodiesaresaid

toalter。(4)Qualityinrespectofvirtueandvice，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’(1)asdoubletohalf，andtrebletoa

third，andingeneralthatwhichcontainssomethingelsemanytimesto

thatwhichiscontainedmanytimesinsomethingelse，andthatwhich

exceedstothatwhichisexceeded；(2)asthatwhichcanheatto

thatwhichcanbeheated，andthatwhichcancuttothatwhichcan

becut，andingeneraltheactivetothepassive；(3)asthe

measurabletothemeasure，andtheknowabletoknowledge，andthe

perceptibletoperception。

(1)Relativetermsofthefirstkindarenumericallyrelated

eitherindefinitelyordefinitely，tonumbersthemselvesorto1。E。g。

thedoubleisinadefinitenumericalrelationto1，andthatwhichis

’manytimesasgreat’isinanumerical，butnotadefinite，

relationto1，i。e。notinthisorinthatnumericalrelationtoit；

therelationofthatwhichishalfasbigagainassomethingelseto

thatsomethingisadefinitenumericalrelationtoanumber；that

whichisn+I/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。

(2)Thingsthatareactiveorpassiveimplyanactiveorapassive

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；but(3)thatwhichismeasurableorknowableorthinkableis

calledrelativebecausesomethingelseinvolvesareferencetoit。For

’thatwhichisthinkable’impliesthatthethoughtofitis