’Nature’means1thegenesisofgrowingthings-themeaningwhich
　　wouldbesuggestedifoneweretopronouncethe’u’inphusislong。
　　2Thatimmanentpartofagrowingthing，fromwhichitsgrowthfirst
　　proceeds。3Thesourcefromwhichtheprimarymovementineach
　　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-6Byan
　　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’1athatwithoutwhich，asacondition，
　　athingcannotlive；e。g。breathingandfoodarenecessaryforan
　　animal；foritisincapableofexistingwithoutthese；bthe
　　conditionswithoutwhichgoodcannotbeorcometobe，orwithout
　　whichwecannotgetridorbefreedofevil；e。g。drinkingthe
　　medicineisnecessaryinorderthatwemaybecuredofdisease，and
　　aman’ssailingtoAeginaisnecessaryinorderthathemaygethis
　　money-2Thecompulsoryandcompulsion，i。e。thatwhichimpedes
　　andtendstohinder，contrarytoimpulseandpurpose。Forthe
　　compulsoryiscallednecessarywhencethenecessaryispainful，as
　　Evenussays:’Foreverynecessarythingiseverirksome’，and
　　compulsionisaformofnecessity，asSophoclessays:’Butforce
　　necessitatesmetothisact’。Andnecessityisheldtobesomething
　　thatcannotbepersuaded-andrightly，foritiscontrarytothe
　　movementwhichaccordswithpurposeandwithreasoning-3Wesay
　　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’means1thatwhichisonebyaccident，2thatwhichis
　　onebyitsownnature。1Instancesoftheaccidentallyoneare
　　’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。2Ofthingsthatarecalledoneinvirtue
　　oftheirownnaturesomeaaresocalledbecausetheyare
　　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。
　　biThingsarecalledoneinanothersensebecausetheir
　　substratumdoesnotdifferinkind；itdoesnotdifferinthecase
　　ofthingswhosekindisindivisibletosense。Thesubstratummeant
　　iseitherthenearestto，orthefarthestfrom，thefinalstate。
　　For，onetheonehand，wineissaidtobeoneandwaterissaidto
　　beone，quaindivisibleinkind；and，ontheotherhand，alljuices，
　　e。g。oilandwine，aresaidtobeone，andsoareallthingsthat
　　canbemelted，becausetheultimatesubstratumofallisthesame；for
　　allofthesearewaterorair。
　　iiThosethingsalsoarecalledonewhosegenusisonethough
　　distinguishedbyoppositedifferentiae-thesetooareallcalledone
　　becausethegenuswhichunderliesthedifferentiaeisonee。g。horse，
　　man，anddogformaunity，becauseallareanimals，andindeedina
　　waysimilartothatinwhichthematterisone。Thesearesometimes
　　calledoneinthisway，butsometimesitisthehighergenusthatis
　　saidtobethesameiftheyareinfimaespeciesoftheirgenus-the
　　genusabovetheproximategenera；e。g。theisoscelesandthe
　　equilateralareoneandthesamefigurebecausebotharetriangles；
　　buttheyarenotthesametriangles。
　　cTwothingsarecalledone，whenthedefinitionwhichstates
　　theessenceofoneisindivisiblefromanotherdefinitionwhich
　　showsustheotherthoughinitselfeverydefinitionisdivisible。
　　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
　　togetheranyhowweshouldnotcallthemoneallthesameunless
　　becauseoftheircontinuity；wedothisonlyiftheyareputtogether
　　soastobeashoeandtohavealreadyacertainsingleform。This
　　iswhythecircleisofalllinesmosttrulyone，becauseitis
　　wholeandcomplete。
　　3Theessenceofwhatisoneistobesomekindofbeginning
　　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。