’Nature’means(1)thegenesisofgrowingthings-themeaningwhich
wouldbesuggestedifoneweretopronouncethe’u’inphusislong。
(2)Thatimmanentpartofagrowingthing，fromwhichitsgrowthfirst
proceeds。(3)Thesourcefromwhichtheprimarymovementineach
naturalobjectispresentinitinvirtueofitsownessence。Those
thingsaresaidtogrowwhichderiveincreasefromsomethingelseby
contactandeitherbyorganicunity，orbyorganicadhesionasin
thecaseofembryos。Organicunitydiffersfromcontact；forinthe
lattercasethereneednotbeanythingbesidesthecontact，butin
organicunitiesthereissomethingidenticalinbothparts，which
makesthemgrowtogetherinsteadofmerelytouching，andbeonein
respectofcontinuityandquantity，thoughnotofquality-(4)
’Nature’meanstheprimarymaterialofwhichanynaturalobject
consistsoroutofwhichitismade，whichisrelativelyunshaped
andcannotbechangedfromitsownpotency，ase。g。bronzeissaid
tobethenatureofastatueandofbronzeutensils，andwoodthe
natureofwoodenthings；andsoinallothercases；forwhenaproduct
ismadeoutofthesematerials，thefirstmatterispreserved
throughout。Foritisinthiswaythatpeoplecalltheelementsof
naturalobjectsalsotheirnature，somenamingfire，othersearth，
othersair，otherswater，otherssomethingelseofthesort，and
somenamingmorethanoneofthese，andothersallofthem-(5)
’Nature’meanstheessenceofnaturalobjects，aswiththosewhosay
thenatureistheprimarymodeofcomposition，orasEmpedoclessays:-
Nothingthatishasanature，
Butonlymixingandpartingofthemixed，
Andnatureisbutanamegiventhembymen。
Henceasregardsthethingsthatareorcometobebynature，though
thatfromwhichtheynaturallycometobeorareisalreadypresent，
wesaytheyhavenottheirnatureyet，unlesstheyhavetheirform
orshape。Thatwhichcomprisesbothoftheseexistsbynature，e。g。
theanimalsandtheirparts；andnotonlyisthefirstmatternature
(andthisintwosenses，eitherthefirst，countingfromthething，or
thefirstingeneral；e。g。inthecaseofworksinbronze，bronzeis
firstwithreferencetothem，butingeneralperhapswaterisfirst，
ifallthingsthatcanbemeltedarewater)，butalsotheformor
essence，whichistheendoftheprocessofbecoming-(6)Byan
extensionofmeaningfromthissenseof’nature’everyessencein
generalhascometobecalleda’nature’，becausethenatureofa
thingisonekindofessence。
Fromwhathasbeensaid，then，itisplainthatnatureinthe
primaryandstrictsenseistheessenceofthingswhichhavein
themselves，assuch，asourceofmovement；forthematteriscalled
thenaturebecauseitisqualifiedtoreceivethis，andprocessesof
becomingandgrowingarecallednaturebecausetheyaremovements
proceedingfromthis。Andnatureinthissenseisthesourceofthe
movementofnaturalobjects，beingpresentinthemsomehow，either
potentiallyorincompletereality。
Wecall’necessary’(1)(a)thatwithoutwhich，asacondition，
athingcannotlive；e。g。breathingandfoodarenecessaryforan
animal；foritisincapableofexistingwithoutthese；(b)the
conditionswithoutwhichgoodcannotbeorcometobe，orwithout
whichwecannotgetridorbefreedofevil；e。g。drinkingthe
medicineisnecessaryinorderthatwemaybecuredofdisease，and
aman’ssailingtoAeginaisnecessaryinorderthathemaygethis
money-(2)Thecompulsoryandcompulsion，i。e。thatwhichimpedes
andtendstohinder，contrarytoimpulseandpurpose。Forthe
compulsoryiscallednecessary(whencethenecessaryispainful，as
Evenussays:’Foreverynecessarythingiseverirksome’)，and
compulsionisaformofnecessity，asSophoclessays:’Butforce
necessitatesmetothisact’。Andnecessityisheldtobesomething
thatcannotbepersuaded-andrightly，foritiscontrarytothe
movementwhichaccordswithpurposeandwithreasoning-(3)Wesay
thatthatwhichcannotbeotherwiseisnecessarilyasitis。And
fromthissenseof’necessary’alltheothersaresomehowderived；for
athingissaidtodoorsufferwhatisnecessaryinthesenseof
compulsory，onlywhenitcannotactaccordingtoitsimpulsebecause
ofthecompellingforces-whichimpliesthatnecessityisthat
becauseofwhichathingcannotbeotherwise；andsimilarlyasregards
theconditionsoflifeandofgood；forwhenintheonecasegood，
intheotherlifeandbeing，arenotpossiblewithoutcertain
conditions，thesearenecessary，andthiskindofcauseisasortof
necessity。Again，demonstrationisanecessarythingbecausethe
conclusioncannotbeotherwise，iftherehasbeendemonstrationinthe
unqualifiedsense；andthecausesofthisnecessityarethefirst
premisses，i。e。thefactthatthepropositionsfromwhichthe
syllogismproceedscannotbeotherwise。
Nowsomethingsowetheirnecessitytosomethingotherthan
themselves；othersdonot，butarethemselvesthesourceof
necessityinotherthings。Thereforethenecessaryintheprimary
andstrictsenseisthesimple；forthisdoesnotadmitofmorestates
thanone，sothatitcannotevenbeinonestateandalsoin
another；forifitdiditwouldalreadybeinmorethanone。If，then，
thereareanythingsthatareeternalandunmovable，nothing
compulsoryoragainsttheirnatureattachestothem。
’One’means(1)thatwhichisonebyaccident，(2)thatwhichis
onebyitsownnature。(1)Instancesoftheaccidentallyoneare
’Coriscusandwhatismusical’，and’musicalCoriscus’(foritis
thesamethingtosay’Coriscusandwhatismusical’，and’musical
Coriscus’)，and’whatismusicalandwhatisjust’，and’musical
CoriscusandjustCoriscus’。Forallofthesearecalledonebyvirtue
ofanaccident，’whatisjustandwhatismusical’becausetheyare
accidentsofonesubstance，’whatismusicalandCoriscus’becausethe
oneisanaccidentoftheother；andsimilarlyinasense’musical
Coriscus’isonewith’Coriscus’becauseoneofthepartsofthe
phraseisanaccidentoftheother，i。e。’musical’isanaccidentof
Coriscus；and’musicalCoriscus’isonewith’justCoriscus’because
onepartofeachisanaccidentofoneandthesamesubject。The
caseissimilariftheaccidentispredicatedofagenusorofany
universalname，e。g。ifonesaysthatmanisthesameas’musical
man’；forthisiseitherbecause’musical’isanaccidentofman，
whichisonesubstance，orbecausebothareaccidentsofsome
individual，e。g。Coriscus。Both，however，donotbelongtohimin
thesameway，butonepresumablyasgenusandincludedinhis
substance，theotherasastateoraffectionofthesubstance。
Thethings，then，thatarecalledoneinvirtueofanaccident，
arecalledsointhisway。(2)Ofthingsthatarecalledoneinvirtue
oftheirownnaturesome(a)aresocalledbecausetheyare
continuous，e。g。abundleismadeonebyaband，andpiecesofwood
aremadeonebyglue；andaline，evenifitisbent，iscalledoneif
itiscontinuous，aseachpartofthebodyis，e。g。thelegorthe
arm。Ofthesethemselves，thecontinuousbynaturearemoreonethan
thecontinuousbyart。Athingiscalledcontinuouswhichhasbyits
ownnatureonemovementandcannothaveanyother；andthemovementis
onewhenitisindivisible，anditisindivisibleinrespectof
time。Thosethingsarecontinuousbytheirownnaturewhichareone
notmerelybycontact；forifyouputpiecesofwoodtouchingone
another，youwillnotsaytheseareonepieceofwoodoronebodyor
onecontinuumofanyothersort。Things，then，thatarecontinuous
inanywaycalledone，eveniftheyadmitofbeingbent，andstill
morethosewhichcannotbebent；e。g。theshinorthethighismore
onethantheleg，becausethemovementofthelegneednotbeone。And
thestraightlineismoreonethanthebent；butthatwhichisbent
andhasananglewecallbothoneandnotone，becauseitsmovement
maybeeithersimultaneousornotsimultaneous；butthatofthe
straightlineisalwayssimultaneous，andnopartofitwhichhas
magnituderestswhileanothermoves，asinthebentline。
(b)(i)Thingsarecalledoneinanothersensebecausetheir
substratumdoesnotdifferinkind；itdoesnotdifferinthecase
ofthingswhosekindisindivisibletosense。Thesubstratummeant
iseitherthenearestto，orthefarthestfrom，thefinalstate。
For，onetheonehand，wineissaidtobeoneandwaterissaidto
beone，quaindivisibleinkind；and，ontheotherhand，alljuices，
e。g。oilandwine，aresaidtobeone，andsoareallthingsthat
canbemelted，becausetheultimatesubstratumofallisthesame；for
allofthesearewaterorair。
(ii)Thosethingsalsoarecalledonewhosegenusisonethough
distinguishedbyoppositedifferentiae-thesetooareallcalledone
becausethegenuswhichunderliesthedifferentiaeisone(e。g。horse，
man，anddogformaunity，becauseallareanimals)，andindeedina
waysimilartothatinwhichthematterisone。Thesearesometimes
calledoneinthisway，butsometimesitisthehighergenusthatis
saidtobethesame(iftheyareinfimaespeciesoftheirgenus)-the
genusabovetheproximategenera；e。g。theisoscelesandthe
equilateralareoneandthesamefigurebecausebotharetriangles；
buttheyarenotthesametriangles。
(c)Twothingsarecalledone，whenthedefinitionwhichstates
theessenceofoneisindivisiblefromanotherdefinitionwhich
showsustheother(thoughinitselfeverydefinitionisdivisible)。
Thuseventhatwhichhasincreasedorisdiminishingisone，because
itsdefinitionisone，as，inthecaseofplanefigures，isthe
definitionoftheirform。Ingeneralthosethingsthethoughtofwhose
essenceisindivisible，andcannotseparatethemeitherintimeor
inplaceorindefinition，aremostofallone，andofthese
especiallythosewhicharesubstances。Foringeneralthosethings
thatdonotadmitofdivisionarecalledoneinsofarastheydo
notadmitofit；e。g。iftwothingsareindistinguishablequaman，
theyareonekindofman；ifquaanimal，onekindofanimal；ifqua
magnitude，onekindofmagnitude-Nowmostthingsarecalledone
becausetheyeitherdoorhaveorsufferorarerelatedtosomething
elsethatisone，butthethingsthatareprimarilycalledoneare
thosewhosesubstanceisone，-andoneeitherincontinuityorin
formorindefinition；forwecountasmorethanoneeitherthings
thatarenotcontinuous，orthosewhoseformisnotone，orthose
whosedefinitionisnotone。
Whileinasensewecallanythingoneifitisaquantityand
continuous，inasensewedonotunlessitisawhole，i。e。unless
ithasunityofform；e。g。ifwesawthepartsofashoeput
togetheranyhowweshouldnotcallthemoneallthesame(unless
becauseoftheircontinuity)；wedothisonlyiftheyareputtogether
soastobeashoeandtohavealreadyacertainsingleform。This
iswhythecircleisofalllinesmosttrulyone，becauseitis
wholeandcomplete。
(3)Theessenceofwhatisoneistobesomekindofbeginning
ofnumber；forthefirstmeasureisthebeginning，sincethatbywhich
wefirstknoweachclassisthefirstmeasureoftheclass；theone，
then，isthebeginningoftheknowableregardingeachclass。Butthe
oneisnotthesameinallclasses。Forhereitisaquarter-tone，and
thereitisthevowelortheconsonant；andthereisanotherunitof
weightandanotherofmovement。Buteverywheretheoneis
indivisibleeitherinquantityorinkind。Nowthatwhichis
indivisibleinquantityiscalledaunitifitisnotdivisibleinany
dimensionandiswithoutposition，apointifitisnotdivisiblein
anydimensionandhasposition，alineifitisdivisibleinone
dimension，aplaneifintwo，abodyifdivisibleinquantityin
all——i。e。inthree——dimensions。And，reversingtheorder，thatwhich
isdivisibleintwodimensionsisaplane，thatwhichisdivisible
inonealine，thatwhichisinnowaydivisibleinquantityisa
pointoraunit，-thatwhichhasnotpositionaunit，thatwhichhas
positionapoint。
Again，somethingsareoneinnumber，othersinspecies，othersin
genus，othersbyanalogy；innumberthosewhosematterisone，in
speciesthosewhosedefinitionisone，ingenusthosetowhichthe
samefigureofpredicationapplies，byanalogythosewhicharerelated
asathirdthingistoafourth。Thelatterkindsofunityare
alwaysfoundwhentheformerare；e。g。thingsthatareoneinnumber
arealsooneinspecies，whilethingsthatareoneinspeciesare
notalloneinnumber；butthingsthatareoneinspeciesareall
oneingenus，whilethingsthataresoingenusarenotallonein
speciesbutareallonebyanalogy；whilethingsthatareoneby
analogyarenotalloneingenus。
Evidently’many’willhavemeaningsoppositetothoseof’one’；
somethingsaremanybecausetheyarenotcontinuous，othersbecause
theirmatter-eithertheproximatematterortheultimate-is
divisibleinkind，othersbecausethedefinitionswhichstatetheir
essencearemorethanone。
