byThomasAquinasPrologueAsmallerrorattheoutsetcanleadtogreaterrorsinthefinalconclusions，asthePhilosophersaysinIDeCaeloetMundocap。5（271b8—13），andthus，sincebeingandessencearethethingsfirstconceivedofbytheintellect，asAvicennasaysinMetaphysicaeI，cap。6，inordertoavoiderrorsarisingfromignoranceaboutthesetwothings，weshouldresolvethedifficultiessurroundingthembyexplainingwhatthetermsbeingandessenceeachsignifyandbyshowinghoweachmaybefoundinvariousthingsandhoweachisrelatedtothelogicalintentionsofgenus，species，anddifference。
Sinceweoughttoacquireknowledgeofsimplethingsfromcompositeonesandcometoknowthepriorfromtheposterior，ininstructingbeginnersweshouldbeginwithwhatiseasier，andsoweshallbeginwiththesignificationofbeingandproceedfromtheretothesignificationofessence。Chapter1
AsthePhilosophersaysinVMetaphysicaecap。7（1017a22—35），beinghastwosenses。Inonesense，beingsignifiesthatwhichisdividedintothetencategories；inanothersense，thatwhichsignifiesthetruthofpropositions。Thedifferencebetweentheseisthat，inthesecondsense，anythingcanbecalledabeingaboutwhichanaffirmativepropositioncanbeformed，evenifthethingpositsnothinginreality。Inthisway，privationsandnegationsarecalledbeings，aswhenwesaythataffirmationisopposedtonegation，orthatblindnessisintheeye。Butinthefirstsense，nothingcanbecalledabeingunlessitpositssomethinginreality，andthusinthisfirstsenseblindnessandsimilarthingsarenotbeings。
Thetermessenceisnottakenfrombeinginthesecondsense，forinthissensesomethingsarecalledbeingsthathavenoessence，asisclearwithprivations。Rather，thetermessenceistakenfrombeinginthefirstsense。ThusinMetaphysicaeV，com。14，theCommentatorexplainsthecitedtextfromAristotlebysayingthatbeing，inthefirstsense，iswhatsignifiestheessenceofathing。Andsince，assaidabove，beinginthissenseisdividedintothetencategories，essencesignifiessomethingcommontoallnaturesthroughwhichthevariousbeingsareplacedinthevariousgeneraandspecies，ashumanityistheessenceofman，andsoon。
Sincethatthroughwhichathingisconstitutedinitspropergenusorspeciesiswhatissignifiedbythedefinitionindicatingwhatthethingis，philosophersintroducedthetermquidditytomeanthesameasthetermessence；andthisisthesamethingthatthePhilosopherfrequentlytermswhatitistobeathing，thatis，thatthroughwhichsomethinghasbeingasaparticularkindofthing。Essenceisalsocalledform，forthecertitudeofeverythingissignifiedthroughitsform，asAvicennasaysinhisMetaphysicaeI，cap。6。Thesamethingisalsocallednature，takingnatureinthefirstofthefoursensesthatBoethiusdistinguishesinhisbookDePersonaetDuabusNaturiscap。1（PL64，1341B），inthesense，inotherwords，thatnatureiswhatwecalleverythingthatcaninanywaybecapturedbytheintellect，forathingisnotintelligibleexceptthroughitsdefinitionandessence。AndsothePhilosophersaysinVMetaphysicaecap。
4（1014b36）thateverysubstanceisanature。Butthetermnatureusedinthiswayseemstosignifytheessenceofathingasitisorderedtotheproperoperationofthething，fornothingiswithoutitsproperoperation。
Thetermquiddity，surely，istakenfromthefactthatthisiswhatissignifiedbythedefinition。Butthesamethingiscalledessencebecausethebeinghasexistencethroughitandinit。
Butbecausebeingisabsolutelyandprimarilysaidofsubstances，andonlysecondarilyandinacertainsensesaidofaccidents，essencetooisproperlyandtrulyinsubstancesandisinaccidentsonlyinacertainwayandinacertainsense。Nowsomesubstancesaresimpleandsomearecomposite，andessenceisinboth，thoughinthesimplesubstancesinatruerandmorenobleway，asthesehaveexistenceinanoblerway:indeed，thesimplesubstancesarethecauseofthecompositeones，oratleastthisistruewithrespecttothefirstsimplesubstance，whichisGod。
Butbecausetheessencesofthesesubstancesaremorehiddenfromus，weoughttobeginwiththeessencesofcompositesubstances，aslearningiseasierwhenwebeginwiththeeasierthings。ChapterII
Incompositesubstanceswefindformandmatter，asinmantherearesoulandbody。Wecannotsay，however，thateitheroftheseistheessenceofthething。Thatmatteraloneisnottheessenceofthethingisclear，foritisthroughitsessencethatathingisknowableandisplacedinaspeciesorgenus。Butmatterisnotaprincipleofcognition；norisanythingdeterminedtoagenusorspeciesaccordingtoitsmatterbutratheraccordingtowhatsomethingisinact。Norisformalonetheessenceofacompositething，howevermuchcertainpeoplemaytrytoassertthis。
Fromwhathasbeensaid，itisclearthattheessenceisthatwhichissignifiedbythedefinitionofthething。Thedefinitionofanaturalsubstance，however，containsnotonlyformbutalsomatter；otherwise，thedefinitionsofnaturalthingsandmathematicaloneswouldnotdiffer。Norcanitbesaidthatmatterisplacedinthedefinitionofanaturalsubstanceassomethingaddedtotheessenceorassomebeingbeyondtheessenceofthething，forthattypeofdefinitionismorepropertoaccidents，whichdonothaveaperfectessenceandwhichincludeintheirdefinitionsasubjectbeyondtheirowngenus。Therefore，theessenceclearlycomprisesbothmatterandform。
Norcanitbesaidthatessencesignifiestherelationbetweenthematterandtheformorsomethingsuperaddedtothese，forthentheessencewouldofnecessitybeanaccidentandextraneoustothething，andthethingwouldnotbeknownthroughitsessence，contrarytowhatpertainstoanessence。Throughtheform，surely，whichistheactofthematter，thematterismadeabeinginactandacertainkindofthing。Thus，somethingthatsupervenesdoesnotgivetothematterexistenceinactsimply，butratherexistenceinactinacertainway，justasaccidentsdo，aswhenwhitenessmakessomethingactuallywhite。Hence，whensuchaformisacquired，wedonotsaythatthethingisgeneratedsimplybutonlyinacertainway。
Theonlypossibility，therefore，isthatthetermessence，usedwithrespecttocompositesubstances，signifiesthatwhichiscomposedofmatterandform。ThisconclusionisconsistentwithwhatBoethiussaysinhiscommentaryontheCategories，namely，thatousiasignifieswhatiscomposite；ousia，ofcourse，isfortheGreekswhatessenceisforus，asBoethiushimselfsaysinhisbookDePersonaetDuabusNaturis。[[3]]Avicennaevensays，MetaphysicaeV，cap。5，thatthequiddityofacompositesubstanceistheverycompositionoftheformandthematter。AndcommentingonBookVIIofAristotle’sMetaphysicae，theCommentatorsays，"Thenaturethatspeciesingenerablethingshaveissomethinginthemiddle；thatis，itiscomposedofmatterandform。"MetaphysicaeVII，com。27。
Moreover，reasonsupportsthisview，fortheexistenceofacompositesubstanceisneitherformalonenormatteralonebutisrathercomposedofthese。
Theessenceisthataccordingtowhichthethingissaidtoexist；hence，itisrightthattheessencebywhichathingisdenominatedabeingisneitherformalonenotmatteralonebutboth，albeitthatexistenceofthiskindiscausedbytheformandnotbythematter。Similarly，weseethatinotherthingsthatareconstitutedfrommanyprinciples，thethingisnotdenominatedfromjustoneortheotheroftheprinciplesbutratherfromthatwhichembracesboth。Thus，withrespecttoflavors，sweetnessiscausedbytheactionofawarmanimalbodydigestingwhatiswet，andalbeitthatinthiswaywarmthisthecauseofthesweetness，neverthelessabodyisnotcalledsweetbyreasonofthewarmth，butratherbyreasonoftheflavor，whichembracesboththewarmthandthewetness。
Butbecausematteristheprincipleofindividuation，itwouldperhapsseemtofollowthatessence，whichembracesinitselfsimultaneouslybothformandmatter，ismerelyparticularandnotuniversal。Fromthisitwouldfollowthatuniversalshavenodefinitions，assumingthatessenceiswhatissignifiedbythedefinition。Thus，wemustpointoutthatmatterunderstoodinthewaywehavethusfarunderstooditisnottheprincipleofindividuation；
onlysignatematteristheprincipleofindividuation。Icallsignatemattermatterconsideredunderdeterminatedimensions。Signatematterisnotincludedinthedefinitionofmanasman，butsignatematterwouldbeincludedinthedefinitionofSocratesifSocrateshadadefinition。Inthedefinitionofman，however，isincludednon—signatematter:inthedefinitionofmanwedonotincludethisboneandthisfleshbutonlyboneandfleshabsolutely，whicharethenon—signatematterofman。
Hence，theessenceofmanandtheessenceofSocratesdonotdifferexceptasthesignatediffersfromthenon—signate，andsotheCommentatorsays，inMetaphysicaeVII，com。20，"Socratesisnothingotherthananimalityandrationality，whicharehisquiddity。"Similarly，theessenceofagenusandtheessenceofaspeciesdifferassignatefromnon—signate，althoughinthecaseofgenusandspeciesadifferentmodeofdesignationisusedwithrespecttoboth。For，thedesignationoftheindividualwithrespecttothespeciesisthroughmatterdeterminedbydimensions，whilethedesignationofthespecieswithrespecttothegenusisthroughtheconstitutivedifference，whichistakenfromtheformofthething。Thisdeterminationordesignation，however，whichismadeinthespecieswithrespecttothegenus，isnotthroughsomethingthatexistsintheessenceofthespeciesbutinnowayexistsintheessenceofthegenus。Onthecontrary，whateverisinthespeciesisalsointhegenusasundetermined。
Ifanimalwerenotallthatmanisbutratheronlyapartofhim，thenanimalwouldnotbepredicatedofman，fornointegralpartispredicatedofitswhole。
Wecanseehowthishappensbyconsideringhowbodyasapartofanimaldiffersfrombodyasthegenusofanimal。Inthewaybodyisthegenusofanimalitcannotbeanintegralpartofanimal，andthusthetermbodycanbeacceptedinseveralways。Bodyissaidtobeinthegenusofsubstanceinthatithasanaturesuchthatthreedimensionscanbedesignatedinthebody。Thesethreedesignateddimensionsarethebodythatisinthegenusofquantity。Now，itsometimeshappensthatwhathasoneperfectionmayattaintoafurtherperfectionaswell，asisclearinman，whohasasensitivenatureand，further，anintellectiveone。Similarly，abovethisperfectionofhavingaformsuchthatthreedimensionscanbedesignatedinit，therecanbejoinedanotherperfection，aslifeorsomesimilarthing。Thistermbody，therefore，cansignifyacertainthingthathasaformsuchthatfromtheformtherefollowsinthethingdesignatabilityinthreedimensionsandnothingmore，suchthat，inotherwords，fromthisformnofurtherperfectionfollows，butifsomeotherthingissuperadded，itisbeyondthesignificationofbodythusunderstood。Andunderstoodinthisway，bodywillbeanintegralandmaterialpartoftheanimal，becauseinthiswaythesoulwillbebeyondwhatissignifiedbythetermbody，anditwillsuperveneonthebodysuchthatfromthesetwo，namelythesoulandthebody，theanimalisconstitutedasfromparts。
Thistermbodycanalsobeunderstoodassignifyingacertainthingthathasaformsuchthatthreedimensionscanbedesignatedinit，whateverformthismaybe，andsuchthateitherfromtheformsomefurtherperfectioncanproceedornot。Understoodinthisway，bodywillbethegenusofanimal，fortherewillbeunderstoodinanimalnothingthatisnotimplicitlycontainedinbody。Now，thesoulisaformthroughwhichtherecanbedesignatedinthethingthreedimensions，andtherefore，whenwesaythatbodyiswhathasaformfromwhichthreedimensionscanbedesignatedinthebody，weunderstandthereissomekindofformofthistype，whethersoul，orlapideousness，orwhateverotherform。Andthustheformofanimalisimplicitlycontainedintheformofbody，justasbodyisitsgenus。
Therelationofanimaltomanisthesame。Forifanimalnamedjustacertainthingthathasaperfectionsuchthatitcansenseandmovebyaprincipleexistinginitself，withoutanyotherperfection，thenwhateverfurtherperfectionmaysupervenewouldberelatedtoanimalasacomponentpart，andnotasimplicitlycontainedinthenotionofanimal；andinthiswayanimalwouldnotbeagenus。Butanimalisagenusinthatitsignifiesacertainthingfromtheformofwhichsensationandmotioncanproceed，whateverthisformmaybe，whetherasensiblesoulonly，orasoulbothsensibleandrational。
Therefore，thegenussignifiesindeterminatelythewholethatisinthespeciesanddoesnotsignifymatteralone。Similarly，thedifferencealsosignifiesthewholeanddoesnotsignifytheformalone，andthedefinition，oreventhespecies，signifiesthewhole。Buttheseneverthelesssignifythesamethingindifferentways。Forthegenussignifiesthewholeasacertaindenominationdeterminingthatwhichismaterialinthethingwithoutadeterminationofitsproperform，whencethegenusistakenfromthematter，althoughitisnotthematter。Thisisclearinthecaseofbodies，aswecallsomethingabodyinthatthethinghasaperfectionsuchthatinthethingthreedimensionscanbedesignated，andthisperfectionisrelatedmateriallytosomefurtherperfection。Conversely，thedifferenceislikeacertaindenominationtakenfromthedeterminedform，beyondthefirstconceptionoftheformbywhichthematterisdetermined。So，whenwesaysomethingisanimated（that，inotherwords，ithasasoul），thisdoesnotdeterminewhatthethingis，whetheritisabodyorsomeotherthing。Hence，Avicennasays，MetaphysicaeV，cap。6，thatthegenusisnotunderstoodinthedifferenceasapartofitsessencebutonlyasabeingbeyonditsessence，evenasasubjectiswithrespecttotheconceptofapassion。Andthusthegenusisnotpredicatedperseofthedifference，asthePhilosophersaysinIIIMetaphysicaecap。8（998b24）andinIVTopicorumcap。2（122b22—26），unlessperhapsasasubjectispredicatedofapassion。Butthedefinitionorthespeciescomprehendsboth，namely，thedeterminedmatterthatthetermgenusdesignatesandthedeterminedformthatthetermdifferencedesignates。
Fromthisisitclearwhythegenus，thedifference，andthespeciesarerelatedproportionallytothematter，theform，andthecompositeinnature，althoughtheyarenotthesameasthesethings。For，thegenusisnotthematter，thoughitistakenfromthematterassignifyingthewhole；noristhedifferencetheform，thoughitistakenfromtheformassignifyingthewhole。Thuswesaythatmanisarationalanimal，butnotcomposedoftheanimalandtherationalinthesensethatwesaythatmaniscomposedofsoulandbody:manissaidtobecomposedofsoulandbodyasfromtwothingsfromwhichathirdthingisconstituteddifferentfromeachofthetwo。Man，surely，isneitherbodynorsoul。Butifmanissaidinsomesensetobecomposedoftheanimalandtherational，itwillnotbeasathirdthingcomposedfromthesetwothings，butasathirdconceptcomposedfromthesetwoconcepts。Theconceptofanimaliswithoutdeterminationofaspecialformandexpresses，withrespecttotheultimateperfection，thenatureofthethingfromthatwhichismaterial；theconceptofthedifference，rational，consistsinthedeterminationofthespecialform。Fromthesetwoconceptsareconstitutedtheconceptofthespeciesorthedefinition。Thus，justasathingconstitutedfromotherthingsdoesnothavepredicatedofittheseotherthings，sotooaconceptdoesnothavepredicatedofittheconceptsofwhichitisconstituted:clearly，wedonotsaythatthedefinitioniseitherthegenusorthedifference。
Althoughthegenusmaysignifythewholeessenceofthespecies，neverthelessthereisnotjustoneessenceofthevariousspeciesunderonegenus，fortheunityofthegenusproceedsfromitsveryindeterminationorundifferentiation。
Norisitthecasethatwhatissignifiedthroughthegenusisnumericallyonenatureinthevariousspeciessuchthattoittheresupervenessomeotherthing，whichisthedifferencethatdeterminesit，asaformdeterminesmatter，whichisnumericallyone。Rather，thegenussignifiessomeform（thoughnotdeterminatelythisoneorthatone），whichthedifferenceexpressesdeterminately，theveryonethatissignifiedindeterminatelythroughthegenus。AndthustheCommentatorsaysinMetaphysicaeXII，[[4]]com。14，thatprimematteriscalledonebytheremovalofallforms，butthegenusiscalledonethroughthecommonalityofformssignified。Hence，theindetermination，whichwasthecauseoftheunityofthegenus，havingbeenremovedthroughtheadditionofthedifference，thespeciesremainessentiallydiverse。
Furthermore，since，assaidabove，thenatureofthespeciesisindeterminatewithrespecttotheindividualjustasthenatureofthegenusiswithrespecttothespecies，andsince，further，thegenus，aspredicatedofthespecies，includesinitssignification（althoughindistinctly）everythingthatisinthespeciesdeterminately，sotoodoesthespecies，aspredicatedoftheindividual，signifyeverythingthatisintheindividualessentially，althoughitsignifiesthisindistinctly。Inthisway，theessenceofthespeciesissignifiedbythetermman，andsomanispredicatedofSocrates。
If，however，thenatureofthespeciesissignifiedinsuchawayastoexcludedesignatematter，whichistheprincipleofindividuation，thenthespeciesisrelatedtotheindividualasapart；andthisishowthetermhumanitysignifies，forhumanitysignifiesthatbywhichamanisaman。Designatematter，however，isnotthatbywhichamanisaman，anditisinnowaycontainedamongthosethingsthatmakeamanaman。
Since，therefore，theconceptofhumanityincludesonlythosethingsbywhichamanisaman，designatematterisexcludedorpretermitted，andsinceapartisnotpredicatedofitswhole，humanityispredicatedneitherofmannorofSocrates。ThusAvicennasays，MetaphysicaeV，cap。
5，thatthequiddityofacompositethingisnotthecompositethingofwhichitisthequiddity，eventhoughthequiddityitselfiscomposite，ashumanity，whilecomposite，isnotman。Onthecontrary，itmustbereceivedinsomethingthatisdesignatematter。
Butsince，assaidabove，thedesignationofthespecieswithrespecttothegenusisthroughtheform，andthedesignationoftheindividualwithrespecttothespeciesisthroughmatter，thetermsignifyingthatfromwhichthenatureofthegenusistakenthusexcludesthedeterminateformthatcompletesthespeciesandsignifiesthematerialpartofthewhole，asthebodyisthematerialpartoftheman。However，thetermsignifyingthatfromwhichthenatureofthespeciesistaken，excludingdesignatematter，signifiestheformalpart。Thus，humanityissignifiedasacertainform，anditissaidthatitistheformofthewhole，not，certainly，asaformsuperaddedtotheessentialparts（theformandthematter），butratherastheformofahouseissuperaddedtoitsintegralparts；
andthatisbettercalledtheformwhichisthewhole，inotherwords，thatwhichembracestheformandthematter，albeitexcludingthosethingsthroughwhichthedesignatabilityofmatterarises。
Therefore，thetermmanandthetermhumanitybothsignifytheessenceofman，thoughindiverseways，assaidabove。Thetermmansignifiestheessenceasawhole，inotherwords，insofarastheessencedoesnotexcludedesignationofmatterbutimplicitlyandindistinctlycontainsit，inthewayinwhichwesaidthatthegenuscontainsthedifference。Hence，thetermmanispredicatedofindividuals。Butthetermhumanitysignifiestheessenceofmanasapartbecauseitcontainsinitssignificationonlywhatbelongstomaninsofarasheisman，anditexcludesalldesignation，andsoitisnotpredicatedofindividualmen。Andforthisreasonthetermessenceissometimesfoundpredicatedofthething，aswhenwesaythatSocratesisacertainessence；andsometimesthetermessenceisdeniedofthething，aswhenwesaythattheessenceofSocratesisnotSocrates。ChapterIII
Havingseenwhatthetermessencesignifiesincompositesubstances，weoughtnextseeinwhatwayessenceisrelatedtothelogicalintentionsofgenus，species，anddifference。Sincethattowhichtheintentionsofgenusorspeciesordifferenceisappropriateispredicatedofthissignatesingular，itisimpossiblethatauniversalintention，likethatofthespeciesorgenus，shouldbeappropriatetotheessenceifthegenusorspeciesissignifiedasapart，asinthetermhumanityoranimality。Thus，Avicennasays，MetaphysicaeV，cap。6，thatrationalityisnotthedifferencebuttheprincipleofthedifference。Forthesamereason，humanityisnotaspecies，andanimalityisnotagenus。Similarly，wecannotsaythattheintentionofspeciesorgenusisappropriatetotheessenceastoacertainthingexistingbeyondsingulars，asthePlatonistsusedtosuppose，forthenthespeciesandthegenuswouldnotbepredicatedofanindividual:wesurelycannotsaythatSocratesissomethingthatisseparatedfromhim，norwouldthatseparatethingadvanceourknowledgeofthissingularthing。Andsotheonlyremainingpossibilityisthattheintentionofgenusorspeciesisappropriatetotheessenceastheessenceissignifiedasawhole，asthetermmanoranimalimplicitlyandindistinctlycontainsthewholethatisintheindividual。
Thenature，however，ortheessencethusunderstoodcanbeconsideredintwoways。First，wecanconsideritaccordingtoitspropernotion，andthisistoconsideritabsolutely。Inthisway，nothingistrueoftheessenceexceptwhatpertainstoitabsolutely:thuseverythingelsethatmaybeattributedtoitwillbeattributedfalsely。Forexample，toman，inthatwhichheisaman，pertainsanimalandrationalandtheotherthingsthatfallinhisdefinition；whiteorblackorwhateverelseofthiskindthatisnotinthenotionofhumanitydoesnotpertaintomaninthatwhichheisaman。Hence，ifitisaskedwhetherthisnature，consideredinthisway，canbesaidtobeoneormany，weshouldconcedeneitheralternative，forbotharebeyondtheconceptofhumanity，andeithermaybefalltheconceptionofman。Ifpluralitywereintheconceptofthisnature，itcouldneverbeone，butneverthelessitisoneasitexistsinSocrates。
Similarly，ifunitywereinthenotionofthisnature，thenitwouldbeoneandthesameinSocratesandPlato，anditcouldnotbemademanyinthemanyindividuals。Second，wecanalsoconsidertheexistencetheessencehasinthisthingorinthat:inthiswaysomethingcanbepredicatedoftheessenceaccidentallybyreasonofwhattheessenceisin，aswhenwesaythatmaniswhitebecauseSocratesiswhite，althoughthisdoesnotpertaintomaninthatwhichheisaman。
Thenatureconsideredinthisway，however，hasadoubleexistence。
Itexistsinsingularsontheonehand，andinthesoulontheother，andfromeachofthesetherefollowaccidents。Insingulars，furthermore，theessencehasamultipleexistenceaccordingtothemultiplicityofsingulars。
Nevertheless，ifweconsidertheessenceinthefirst，orabsolute，sense，noneofthesepertaintotheessence。Foritisfalsetosaythattheessenceofman，consideredabsolutely，hasexistenceinthissingular，becauseifexistenceinthissingularpertainedtomaninsofarasheisman，manwouldneverexistoutsidethissingular。Similarly，ifitpertainedtomaninsofarasheismannottoexistinthissingular，thentheessencewouldneverexistinthesingular。Butitistruetosaythatman，butnotinsofarasheisman，haswhatevermaybeinthissingularorinthatone，orelseinthesoul。Therefore，thenatureofmanconsideredabsolutelyabstractsfromeveryexistence，thoughitdoesnotexcludetheexistenceofanythingeither。Andthenaturethusconsideredistheonepredicatedofeachindividual。
Nevertheless，thenatureunderstoodinthiswayisnotauniversalnotion，becauseunityandcommonalityareinthenotionofauniversal，andneitherofthesepertainstohumannatureconsideredabsolutely。Forifcommonalitywereintheconceptofman，theninwhateverhumanitywerefound，therewouldbefoundcommonality，andthisisfalse，becausenocommonalityisfoundinSocrates，butratherwhateverisinhimisindividuated。Similarly，thenotionofgenusorspeciesdoesnotpertaintohumannatureasanaccidentarisingfromtheexistencethatthenaturehasinindividuals，forhumannatureisnotfoundinindividualsaccordingtoitsunitysuchthatitwillbeonethinginalltheindividuals，whichthenotionoftheuniversaldemands。Theonlypossibility，therefore，isthatthenotionofspeciespertainstohumannatureaccordingtotheexistencehumannaturehasintheintellect。
Humannaturehasintheintellectexistenceabstractedfromallindividuals，andthusitisrelateduniformlytoallindividualsthatexistoutsidethesoul，asitisequallysimilartoallofthem，anditleadstoknowledgeofallinsofarastheyaremen。Sincethenatureintheintellecthasthisrelationtoeachindividual，theintellectinventsthenotionofspeciesandattributesittoitself。Hence，theCommentator，inDeAnimaI，com。8，says，"Theintellectiswhatmakesuniversalityinthings，"
andAvicennasaysthesameinhisMetaphysicaeV，cap。2。Althoughthisnatureunderstoodintheintellecthasthenotionofauniversalinrelationtothingsoutsidethesoul（becauseitisonelikenessofthemall），asthenaturehasexistenceinthisintellectorinthatone，itisacertainparticularunderstoodspecies。TheCommentator，therefore，isinerrorinDeAnimaIII，com。5，whenhewantstoinfertheunityofintellectinallmenfromtheuniversalityoftheunderstoodform，becausetheuniversalityoftheformdoesnotarisefromtheexistencetheformhasintheintellectbutratherfromitsrelationtothingsasalikenessofsuchthings。Itisasiftherewereacorporealstatuerepresentingmanymen；thatimageorspeciesofstatuewouldhaveasingularandproperexistenceinsofarasitexistsinthismatter，butitwouldhaveanaspectofcommonalityinsofarasitwasacommonrepresentativeofmany。
Sincehumannature，consideredabsolutely，isproperlypredicatedofSocrates，andsincethenotionofspeciesdoesnotpertaintohumannatureconsideredabsolutelybutonlyaccidentallybecauseoftheexistencethenaturehasintheintellect，thetermspeciesisnotpredicatedofSocrates，forwedonotsaythatSocratesisaspecies。WewouldhavetosaythatSocratesisaspeciesifthenotionofspeciespertainedtomanarisingfromtheexistencethatthenaturehasinSocratesorfromthenatureconsideredabsolutely，thatis，insofarasmanisman。ForwhateverpertainstomaninsofarasheismanispredicatedofSocrates。
Buttobepredicatedpertainstoagenusperse，becausebeingpredicatedisplacedinitsdefinition。Now，predicationiscompletedbytheactionoftheintellectincompoundinganddividing，andithasasitsbasistheunityofthosethingsoneofwhichissaidofanother。Hence，thenotionofpredicabilitycanbesubsumedinthenotionofthisintentionthatisthegenus，whichisitselfcompletedbyanactoftheintellect。Still，whentheintellectattributestheintentionofpredicabilitytosomethingbycompoundingitwithanother，thisintentionisnotthatofgenus；itisratherthattowhichtheintellectattributestheintentionofgenus，as，forinstance，towhatissignifiedbythetermanimal。
Wehavethusmadeclearhowtheessenceornatureisrelatedtothenotionofspecies，forthenotionofspeciesisnotamongthosethatpertaintotheessenceconsideredabsolutely；norisitamongtheaccidentsthatfollowfromtheexistencethattheessencehasoutsidethesoul，aswhitenessorblackness。Rather，thenotionofspeciesisamongtheaccidentsthatfollowfromtheexistencetheessencehasintheintellect。Andinthiswayaswelldothenotionsofgenusordifferencepertaintoessences。