Moreover，toestablishaview，youshouldlookandseeifthegenusispredicatedinthecategoryofessenceofthosethingsofwhichithasbeenrenderedasthegenus，supposingthespeciesrenderedtobenotonesinglespeciesbutseveraldifferentones：
forthenclearlyitwillbethegenus。If，ontheother，thespeciesrenderedbesingle，lookandseewhetherthegenusbepredicatedinthecategoryofessenceofotherspeciesaswell：forthen，again，theresultwillbethatitispredicatedofseveraldifferentspecies。
Sincesomepeoplethinkthatthedifferentia，too，isapredicateofthevariousspeciesinthecategoryofessence，youshoulddistinguishthegenusfromthedifferentiabyemployingtheaforesaidelementaryprinciples—（a）thatthegenushasawiderdenotationthanthedifferentia；（b）thatinrenderingtheessenceofathingitismorefittingtostatethegenusthanthedifferentia：foranyonewhosaysthat’man’isan’animal’showswhatmanisbetterthanhewhodescribeshimas’walking’；also（c）thatthedifferentiaalwayssignifiesaqualityofthegenus，whereasthegenusdoesnotdothisofthedifferentia：forhewhosays’walking’describesananimalofacertainquality，whereashewhosays’animal’describesananimalofacertainquality，whereashewhosays’animal’doesnotdescribeawalkingthingofacertainquality。
Thedifferentia，then，shouldbedistinguishedfromthegenusinthismanner。Nowseeingitisgenerallyheldthatifwhatismusical，inbeingmusical，possessesknowledgeinsomerespect，thenalso’music’isaparticularkindof’knowledge’；andalsothatifwhatwalksismovedinwalking，then’walking’isaparticularkindof’movement’；youshouldthereforeexamineintheaforesaidmanneranygenusinwhichyouwanttoestablishtheexistenceofsomething；
e。g。ifyouwishtoprovethat’knowledge’isaformof’conviction’，seewhethertheknowerinknowingisconvinced：forthenclearlyknowledgewouldbeaparticularkindofconviction。Youshouldproceedinthesamewayalsoinregardtotheothercasesofthiskind。