Therearemanysensesinwhichathingmaybesaidto’be’，but
allthat’is’isrelatedtoonecentralpoint，onedefinitekindof
thing，andisnotsaidto’be’byamereambiguity。Everythingwhich
ishealthyisrelatedtohealth，onethinginthesensethatit
preserveshealth，anotherinthesensethatitproducesit，anotherin
thesensethatitisasymptomofhealth，anotherbecauseitis
capableofit。Andthatwhichismedicalisrelativetothemedical
art，onethingbeingcalledmedicalbecauseitpossessesit，another
becauseitisnaturallyadaptedtoit，anotherbecauseitisa
functionofthemedicalart。Andweshallfindotherwordsused
similarlytothese。So，too，therearemanysensesinwhichathingis
saidtobe，butallrefertoonestarting-point；somethingsare
saidtobebecausetheyaresubstances，othersbecausetheyare
affectionsofsubstance，othersbecausetheyareaprocesstowards
substance，ordestructionsorprivationsorqualitiesofsubstance，or
productiveorgenerativeofsubstance，orofthingswhicharerelative
tosubstance，ornegationsofoneofthesethingofsubstance
itself。Itisforthisreasonthatwesayevenofnon-beingthatitis
nonbeing。As，then，thereisonesciencewhichdealswithall
healthythings，thesameappliesintheothercasesalso。Fornotonly
inthecaseofthingswhichhaveonecommonnotiondoesthe
investigationbelongtoonescience，butalsointhecaseofthings
whicharerelatedtoonecommonnature；foreventheseinasensehave
onecommonnotion。Itisclearthenthatitistheworkofonescience
alsotostudythethingsthatare，quabeing-Buteverywherescience
dealschieflywiththatwhichisprimary，andonwhichtheother
thingsdepend，andinvirtueofwhichtheygettheirnames。If，
then，thisissubstance，itwillbeofsubstancesthatthephilosopher
mustgrasptheprinciplesandthecauses。
Nowforeachoneclassofthings，asthereisoneperception，so
thereisonescience，asforinstancegrammar，beingonescience，
investigatesallarticulatesounds。Hencetoinvestigateallthe
speciesofbeingquabeingistheworkofasciencewhichis
genericallyone，andtoinvestigatetheseveralspeciesistheworkof
thespecificpartsofthescience。
If，now，beingandunityarethesameandareonethinginthe
sensethattheyareimpliedinoneanotherasprincipleandcauseare，
notinthesensethattheyareexplainedbythesamedefinition
thoughitmakesnodifferenceevenifwesupposethemtobelike
that-infactthiswouldevenstrengthenourcase；for’oneman’and
’man’arethesamething，andsoare’existentman’and’man’，andthe
doublingofthewordsin’onemanandoneexistentman’doesnot
expressanythingdifferentitisclearthatthetwothingsarenot
separatedeitherincomingtobeorinceasingtobe；andsimilarly
’oneexistentman’addsnothingto’existentman’，andthatitis
obviousthattheadditioninthesecasesmeansthesamething，and
unityisnothingapartfrombeing；andif，further，thesubstanceof
eachthingisoneinnomerelyaccidentalway，andsimilarlyisfrom
itsverynaturesomethingthatis:-allthisbeingso，theremustbe
exactlyasmanyspeciesofbeingasofunity。Andtoinvestigatethe
essenceoftheseistheworkofasciencewhichisgenericallyone-I
mean，forinstance，thediscussionofthesameandthesimilarandthe
otherconceptsofthissort；andnearlyallcontrariesmaybereferred
tothisorigin；letustakethemashavingbeeninvestigatedinthe
’SelectionofContraries’。
Andthereareasmanypartsofphilosophyastherearekindsof
substance，sothattheremustnecessarilybeamongthemafirst
philosophyandonewhichfollowsthis。Forbeingfallsimmediately
intogenera；forwhichreasonthesciencestoowillcorrespondto
thesegenera。Forthephilosopherislikethemathematician，asthat
wordisused；formathematicsalsohasparts，andthereisafirstand
asecondscienceandothersuccessiveoneswithinthesphereof
mathematics。
Nowsinceitistheworkofonesciencetoinvestigate
opposites，andpluralityisopposedtounity-anditbelongstoone
sciencetoinvestigatethenegationandtheprivationbecausein
bothcaseswearereallyinvestigatingtheonethingofwhichthe
negationortheprivationisanegationorprivationforweeither
saysimplythatthatthingisnotpresent，orthatitisnotpresent
insomeparticularclass；inthelattercasedifferenceispresent
overandabovewhatisimpliedinnegation；fornegationmeansjust
theabsenceofthethinginquestion，whileinprivationthereisalso
employedanunderlyingnatureofwhichtheprivationis
asserted:-inviewofallthesefacts，thecontrariesofthe
conceptswenamedabove，theotherandthedissimilarandtheunequal，
andeverythingelsewhichisderivedeitherfromtheseorfrom
pluralityandunity，mustfallwithintheprovinceofthescience
abovenamed。Andcontrarietyisoneoftheseconcepts；forcontrariety
isakindofdifference，anddifferenceisakindofotherness。
Therefore，sincetherearemanysensesinwhichathingissaidto
beone，thesetermsalsowillhavemanysenses，butyetitbelongs
toonesciencetoknowthemall；foratermbelongstodifferent
sciencesnotifithasdifferentsenses，butifithasnotonemeaning
anditsdefinitionscannotbereferredtoonecentralmeaning。And
sinceallthingsarereferredtothatwhichisprimary，asfor
instanceallthingswhicharecalledonearereferredtotheprimary
one，wemustsaythatthisholdsgoodalsoofthesameandtheother
andofcontrariesingeneral；sothatafterdistinguishingthevarious
sensesofeach，wemustthenexplainbyreferencetowhatisprimary
inthecaseofeachofthepredicatesinquestion，sayinghowtheyare
relatedtoit；forsomewillbecalledwhattheyarecalledbecause
theypossessit，othersbecausetheyproduceit，andothersinother
suchways。
Itisevident，then，thatitbelongstoonesciencetobeable
togiveanaccountoftheseconceptsaswellasofsubstancethiswas
oneofthequestionsinourbookofproblems，andthatitisthe
functionofthephilosophertobeabletoinvestigateallthings。
Forifitisnotthefunctionofthephilosopher，whoisitwhowill
inquirewhetherSocratesandSocratesseatedarethesamething，or
whetheronethinghasonecontrary，orwhatcontrarietyis，orhow
manymeaningsithas？Andsimilarlywithallothersuchquestions。
Since，then，theseareessentialmodificationsofunityquaunity
andofbeingquabeing，notquanumbersorlinesorfire，itis
clearthatitbelongstothissciencetoinvestigateboththe
essenceoftheseconceptsandtheirproperties。Andthosewhostudy
thesepropertieserrnotbyleavingthesphereofphilosophy，butby
forgettingthatsubstance，ofwhichtheyhavenocorrectidea，is
priortotheseotherthings。Fornumberquanumberhaspeculiar
attributes，suchasoddnessandevenness，commensurabilityand
equality，excessanddefect，andthesebelongtonumberseitherin
themselvesorinrelationtooneanother。Andsimilarlythesolid
andthemotionlessandthatwhichisinmotionandtheweightless
andthatwhichhasweighthaveotherpeculiarproperties。Sotoothere
arecertainpropertiespeculiartobeingassuch，anditisabout
thesethatthephilosopherhastoinvestigatethetruth-Anindication
ofthismaybementioned:dialecticiansandsophistsassumethesame
guiseasthephilosopher，forsophisticisWisdomwhichexistsonlyin
semblance，anddialecticiansembraceallthingsintheirdialectic，
andbeingiscommontoallthings；butevidentlytheirdialectic
embracesthesesubjectsbecausethesearepropertophilosophy-For
sophisticanddialecticturnonthesameclassofthingsas
philosophy，butthisdiffersfromdialecticinthenatureofthe
facultyrequiredandfromsophisticinrespectofthepurposeofthe
philosophiclife。Dialecticismerelycriticalwherephilosophyclaims
toknow，andsophisticiswhatappearstobephilosophybutisnot。
Again，inthelistofcontrariesoneofthetwocolumnsis
privative，andallcontrariesarereducibletobeingandnon-being，
andtounityandplurality，asforinstancerestbelongstounity
andmovementtoplurality。Andnearlyallthinkersagreethatbeing
andsubstancearecomposedofcontraries；atleastallnamecontraries
astheirfirstprinciples-somenameoddandeven，somehotandcold，
somelimitandtheunlimited，someloveandstrife。Andalltheothers
aswellareevidentlyreducibletounityandpluralitythisreduction
wemusttakeforgranted，andtheprinciplesstatedbyotherthinkers
fallentirelyundertheseastheirgenera。Itisobviousthenfrom
theseconsiderationstoothatitbelongstoonesciencetoexamine
beingquabeing。Forallthingsareeithercontrariesorcomposedof
contraries，andunityandpluralityarethestarting-pointsofall
contraries。Andthesebelongtoonescience，whethertheyhaveorhave
notonesinglemeaning。Probablythetruthisthattheyhavenot；
yetevenif’one’hasseveralmeanings，theothermeaningswillbe
relatedtotheprimarymeaningandsimilarlyinthecaseofthe
contraries，evenifbeingorunityisnotauniversalandthesamein
everyinstanceorisnotseparablefromtheparticularinstancesas
infactitprobablyisnot；theunityisinsomecasesthatof
commonreference，insomecasesthatofserialsuccession。Andfor
thisreasonitdoesnotbelongtothegeometertoinquirewhatis
contrarietyorcompletenessorunityorbeingorthesameorthe
other，butonlytopresupposetheseconceptsandreasonfromthis
starting-point——Obviouslythenitistheworkofonescienceto
examinebeingquabeing，andtheattributeswhichbelongtoitqua
being，andthesamesciencewillexaminenotonlysubstancesbut
alsotheirattributes，boththoseabovenamedandtheconcepts’prior’
and’posterior’，’genus’and’species’，’whole’and’part’，andthe
othersofthissort。
Wemuststatewhetheritbelongstooneortodifferentsciences
toinquireintothetruthswhichareinmathematicscalledaxioms，and
intosubstance。Evidently，theinquiryintothesealsobelongsto
onescience，andthatthescienceofthephilosopher；forthesetruths
holdgoodforeverythingthatis，andnotforsomespecialgenusapart
fromothers。Andallmenusethem，becausetheyaretrueofbeing
quabeingandeachgenushasbeing。Butmenusethemjustsofarasto
satisfytheirpurposes；thatis，asfarasthegenustowhichtheir
demonstrationsreferextends。Thereforesincethesetruthsclearly
holdgoodforallthingsquabeingforthisiswhatiscommonto
them，tohimwhostudiesbeingquabeingbelongstheinquiryinto
theseaswell。Andforthisreasonnoonewhoisconductinga
specialinquirytriestosayanythingabouttheirtruthor
falsity，-neitherthegeometernorthearithmetician。Somenatural
philosophersindeedhavedoneso，andtheirprocedurewasintelligible
enough；fortheythoughtthattheyalonewereinquiringaboutthe
wholeofnatureandaboutbeing。Butsincethereisonekindof
thinkerwhoisaboveeventhenaturalphilosopherfornatureis
onlyoneparticulargenusofbeing，thediscussionofthesetruths
alsowillbelongtohimwhoseinquiryisuniversalanddealswith
primarysubstance。PhysicsalsoisakindofWisdom，butitisnotthe
firstkind-Andtheattemptsofsomeofthosewhodiscussthetermson
whichtruthshouldbeaccepted，areduetoawantoftrainingin
logic；fortheyshouldknowthesethingsalreadywhentheycometoa
specialstudy，andnotbeinquiringintothemwhiletheyarelistening
tolecturesonit。
Evidentlythenitbelongstothephilosopher，i。e。tohimwhois
studyingthenatureofallsubstance，toinquirealsointothe
principlesofsyllogism。Buthewhoknowsbestabouteachgenusmust
beabletostatethemostcertainprinciplesofhissubject，sothat
hewhosesubjectisexistingthingsquaexistingmustbeabletostate
themostcertainprinciplesofallthings。Thisisthephilosopher，
andthemostcertainprincipleofallisthatregardingwhichitis
impossibletobemistaken；forsuchaprinciplemustbeboththe
bestknownforallmenmaybemistakenaboutthingswhichtheydonot
know，andnon-hypothetical。Foraprinciplewhicheveryonemusthave
whounderstandsanythingthatis，isnotahypothesis；andthat
whicheveryonemustknowwhoknowsanything，hemustalreadyhave
whenhecomestoaspecialstudy。Evidentlythensuchaprincipleis
themostcertainofall；whichprinciplethisis，letusproceedto
say。Itis，thatthesameattributecannotatthesametimebelongand
notbelongtothesamesubjectandinthesamerespect；wemust