ChapterIV
Weshouldnowseehowessencesexistinseparatedsubstances，thatis，inthesoul，intheintelligences，andinthefirstcause。Now，whileeveryoneconcedesthesimplicityofthefirstcause，somepeoplehavetriedtointroduceintotheintelligencesandthesoulacompositionofformandmatter，apositionthatseemstohavebegunwithAvicebron，theauthorofthebookcalledFonsVitae。Butthisviewisrepugnanttothecommonteachingofthephilosophers，fortheycallthesethingssubstancesseparatedfrommatter，andtheyprovethemtobewhollywithoutmatter。Themostcogentdemonstrationofthisproceedsfromtheexcellenceofunderstandingfoundinthesesubstances。Forweseethatformsarenotactuallyintelligibleexceptastheyareseparatedfrommatteranditsconditions，andformsarenotmadeactuallyintelligibleexceptbyvirtueofanintelligentsubstance，whicheducestheformsandreceivestheminitself。Hence，inanyintelligentsubstancethereisacompleteabsenceofmatterinsuchawaythatthesubstancehasneitheramaterialpartitselfnorevenisthesubstancelikeaformimpressedinmatter，asisthecasewithmaterialforms。
Norcansomeonesaythatonlycorporealmatter，andnotsomeotherkindofmatter，impedesintelligibility。For，ifitwereonlycorporealmaterthatimpedesintelligibility，thensincematteriscalledcorporealonlyinsofarasitexistsunderacorporealform，matter’simpedingintelligibilitywouldcomefromthecorporealform；andthisisimpossible，forthecorporealformisactuallyintelligiblejustlikeanyotherform，insofarasitisabstractedfrommatter。Hence，innowayisthereacompositionofmatterandformineitherthesoulortheintelligences，suchthatanessenceisreceivedintheseasincorporealsubstances。Nevertheless，inseparatesubstancesthereisacompositionofformandexistence，andsointheLiberdeCausis，prop。9，com。，itissaidthattheintelligenceshaveformandexistence，andinthisplaceformistakeninthesenseofasimplequiddityornature。
Itiseasytoseehowthisisthecase。Whenevertwothingsarerelatedtoeachothersuchthatoneisthecauseoftheother，theonethatisthecausecanhaveexistencewithouttheother，butnotconversely。Now，wefindthatmatterandformarerelatedinsuchawaythatformgivesexistencetomatter，andthereforeitisimpossiblethatmatterexistwithoutaform；butitisnotimpossiblethataformexistwithoutmatter，foraform，insofarasitisaform，isnotdependentonmatter。Whenwefindaformthatcannotexistexceptinmatter，thishappensbecausesuchformsaredistantfromthefirstprinciple，whichisprimaryandpureact。Hence，thoseformsthatarenearestthefirstprinciplearesubsistingformsessentiallywithoutmatter，fornotthewholegenusofformsrequiresmatter，assaidabove，andtheintelligencesareformsofthistype。Thus，theessencesorquidditiesofthesesubstancesarenototherthantheformsthemselves。
Therefore，theessenceofacompositesubstanceandthatofasimplesubstancedifferinthattheessenceofacompositesubstanceisnotformalonebutembracesbothformandmatter，whiletheessenceofasimplesubstanceisformalone。Andfromthistwootherdifferencesarise。Oneisthattheessenceofacompositesubstancecanbesignifiedasawholeorasapart，whichhappensbecauseofthedesignationofthematter，assaidabove。Hence，inoneway，theessenceofacompositethingisnotpredicatedofthecompositethingitself，forwecannotsaythatamanishisownquiddity。Buttheessenceofasimplething，whichisitsform，cannotbesignifiedexceptasawhole，asinthiscasethereisnothingbeyondtheformthatmightreceivethequiddity，andso，howeverwetaketheessenceofasimplething，theessenceispredicatedofit。Hence，AvicennasaysinMetaphysicaeV，cap。5that\"thequiddityofasimplethingisthesimplethingitself，\"becausethereisnootherthingtoreceivetheform。Theseconddifferenceisthattheessencesofcompositethings，becausetheyarereceivedindesignatematter，aremultipliedaccordingtothedivisionofmatter，andsoithappensthatsomethingsarethesameinspeciesbutdifferentinnumber。Butsincetheessenceofasimplethingisnotreceivedinmatter，therecanbenosuchmultiplicationinthiscase，andsoamongsuchsubstanceswedonotfindmanyindividualsofthesamespecies，asAvicennaexpresslysaysinMetaphysicaeV，cap。