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