ation　of　an　actuality　to　that　of　which　it　is　the　actuality。　We　have　now　given　an　answer　to　the　question；　What　is　soul？…an　answer　which　applies　to　it　in　its　full　extent。　It　is　substance　in　the　sense　which　corresponds　to　the　definitive　formula　of　a　thing's　essence。　That　means　that　it　is　'the　essential　whatness'　of　a　body　of　the　character　just　assigned。　Suppose　that　what　is　literally　an　'organ'；　like　an　axe；　were　a　natural　body；　its　'essential　whatness'；　would　have　been　its　essence；　and　so　its　soul；　if　this　disappeared　from　it；　it　would　have　ceased　to　be　an　axe；　except　in　name。　As　it　is；　it　is　just　an　axe；　it　wants　the　character　which　is　required　to　make　its　whatness　or　formulable　essence　a　soul；　for　that；　it　would　have　had　to　be　a　natural　body　of　a　particular　kind；　viz。　one　having　in　itself　the　power　of　setting　itself　in　movement　and　arresting　itself。　Next；　apply　this　doctrine　in　the　case　of　the　'parts'　of　the　living　body。　Suppose　that　the　eye　were　an　animal…sight　would　have　been　its　soul；　for　sight　is　the　substance　or　essence　of　the　eye　which　corresponds　to　the　formula；　the　eye　being　merely　the　matter　of　seeing；　when　seeing　is　removed　the　eye　is　no　longer　an　eye；　except　in　name…it　is　no　more　a　real　eye　than　the　eye　of　a　statue　or　of　a　painted　figure。　We　must　now　extend　our　consideration　from　the　'parts'　to　the　whole　living　body；　for　what　the　departmental　sense　is　to　the　bodily　part　which　is　its　organ；　that　the　whole　faculty　of　sense　is　to　the　whole　sensitive　body　as　such。　　　We　must　not　understand　by　that　which　is　'potentially　capable　of　living'　what　has　lost　the　soul　it　had；　but　only　what　still　retains　it；　but　seeds　and　fruits　are　bodies　which　possess　the　qualification。　Consequently；　while　waking　is　actuality　in　a　sense　corresponding　to　the　cutting　and　the　seeing；　the　soul　is　actuality　in　the　sense　corresponding　to　the　power　of　sight　and　the　power　in　the　tool；　the　body　corresponds　to　what　exists　in　potentiality；　as　the　pupil　plus　the　power　of　sight　constitutes　the　eye；　so　the　soul　plus　the　body　constitutes　the　animal。　　　From　this　it　indubitably　follows　that　the　soul　is　inseparable　from　its　body；　or　at　any　rate　that　certain　parts　of　it　are　（if　it　has　parts）　for　the　actuality　of　some　of　them　is　nothing　but　the　actualities　of　their　bodily　parts。　Yet　some　may　be　separable　because　they　are　not　the　actualities　of　any　body　at　all。　Further；　we　have　no　light　on　the　problem　whether　the　soul　may　not　be　the　actuality　of　its　body　in　the　sense　in　which　the　sailor　is　the　actuality　of　the　ship。　　　This　must　suffice　as　our　sketch　or　outline　determination　of　the　nature　of　soul。
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  Since　what　is　clear　or　logically　more　evident　emerges　from　what　in　itself　is　confused　but　more　observable　by　us；　we　must　reconsider　our　results　from　this　point　of　view。　For　it　is　not　enough　for　a　definitive　formula　to　express　as　most　now　do　the　mere　fact；　it　must　include　and　exhibit　the　ground　also。　At　present　definitions　are　given　in　a　form　analogous　to　the　conclusion　of　a　syllogism；　e。g。　What　is　squaring？　The　construction　of　an　equilateral　rectangle　equal　to　a　given　oblong　rectangle。　Such　a　definition　is　in　form　equivalent　to　a　conclusion。　One　that　tells　us　that　squaring　is　the　discovery　of　a　line　which　is　a　mean　proportional　between　the　two　unequal　sides　of　the　given　rectangle　discloses　the　ground　of　what　is　defined。　　　We　resume　our　inquiry　from　a　fresh　starting…point　by　calling　attention　to　the　fact　that　what　has　soul　in　it　differs　from　what　has　not；　in　that　the　former　displays　life。　Now　this　word　has　more　than　one　sense；　and　provided　any　one　alone　of　these　is　found　in　a　thing　we　say　that　thing　is　living。　Living；　that　is；　may　mean　thinking　or　perception　or　local　movement　and　rest；　or　movement　in　the　sense　of　nutrition；　decay　and　growth。　Hence　we　think　of　plants　also　as　living；　for　they　are　observed　to　possess　in　themselves　an　originative　power　through　which　they　increase　or　decrease　in　all　spatial　directions；　they　grow　up　and　down；　and　everything　that　grows　increases　its　bulk　alike　in　both　directions　or　indeed　in　all；　and　continues　to　live　so　long　as　it　can　absorb　nutriment。　　　This　power　of　self…nutrition　can　be　isolated　from　the　other　powers　mentioned；　but　not　they　from　it…in　mortal　beings　at　least。　The　fact　is　obvious　in　plants；　for　it　is　the　only　psychic　power　they　possess。　　　This　is　the　originative　power　the　possession　of　which　leads　us　to　speak　of　things　as　living　at　all；　but　it　is　the　possession　of　sensation　that　leads　us　for　the　first　time　to　speak　of　living　things　as　animals；　for　even　those　beings　which　possess　no　power　of　local　movement　but　do　possess　the　power　of　sensation　we　call　animals　and　not　merely　living　things。　　　The　primary　form　of　sense　is　touch；　which　belongs　to　all　animals。　just　as　the　power　of　self…nutrition　can　be　isolated　from　touch　and　sensation　generally；　so　touch　can　be　isolated　from　all　other　forms　of　sense。　（By　the　power　of　self…nutrition　we　mean　that　departmental　power　of　the　soul　which　is　common　to　plants　and　animals：　all　animals　whatsoever　are　observed　to　have　the　sense　of　touch。）　What　the　explanation　of　these　two　facts　is；　we　must　discuss　later。　At　present　we　must　confine　ourselves　to　saying　that　soul　is　the　source　of　these　phenomena　and　is　characterized　by　them；　viz。　by　the　powers　of　self…nutrition；　sensation；　thinking；　and　motivity。　　　Is　each　of　these　a　soul　or　a　part　of　a　soul？　And　if　a　part；　a　part　in　what　sense？　A　part　merely　distinguishable　by　definition　or　a　part　distinct　in　local　situation　as　well？　In　the　case　of　certain　of　these　powers；　the　answers　to　these　questions　are　easy；　in　the　case　of　others　we　are　puzzled　what　to　say。　just　as　in　the　case　of　plants　which　when　divided　are　observed　to　continue　to　live　though　removed　to　a　distance　from　one　another　（thus　showing　that　in　their　case　the　soul　of　each　individual　plant　before　division　was　actually　one；　potentially　many）；　so　we　notice　a　similar　result　in　other　varieties　of　soul；　i。e。　in　insects　which　have　been　cut　in　two；　each　of　the　segments　possesses　both　sensation　and　local　movement；　and　if　sensation；　necessarily　also　imagination　and　appetition；　for；　where　there　is　sensation；　there　is　also　pleasure　and　pain；　and；　where　these；　necessarily　also　desire。　　　We　have　no　evidence　as　yet　about　mind　or　the　power　to　think；　it　seems　to　be　a　widely　different　kind　of　soul；　differing　as　what　is　eternal　from　what　is　perishable；　it　alone　is　capable　of　existence　in　isolation　from　all　other　psychic　powers。　All　the　other　parts　of　soul；　it　is　evident　from　what　we　have　said；　are；　in　spite　of　certain　statements　to　the　contrary；　incapable　of　separate　existence　though；　of　course；　distinguishable　by　definition。　If　opining　is　distinct　from　perceiving；　to　be　capable　of　opining　and　to　be　capable　of　perceiving　must　be　distinct；　and　so　with　all　the　other　forms　of　living　above　enumerated。　Further；　some　animals　possess　all　these　parts　of　soul；　some　certain　of　them　only；　others　one　only　（this　is　what　enables　us　to　classify　animals）；　the　cause　must　be　considered　later。'　A　similar　arrangement　is　found　also　within　the　field　of　the　senses；　some　classes　of　animals　have　all　the　senses；　some　only　certain　of　them；　others　only　one；　the　most　indispensable；　touch。　　　Since　the　expression　'that　whereby　we　live　and　perceive'　has　two　meanings；　just　like　the　expression　'that　whereby　we　know'…that　may　mean　either　（a）　knowledge　or　（b）　the　soul；　for　we　can　speak　of　knowing　by　or　with　either；　and　similarly　that　whereby　we　are　in　health　may　be　either　（a）　health　or　（b）　the　body　or　some　part　of　the　body；　and　since　of　the　two　terms　thus　contrasted　knowledge　or　health　is　the　name　of　a　form；　essence；　or　ratio；　or　if　we　so　express　it　an　actuality　of　a　recipient　matter…knowledge　of　what　is　capable　of　knowing；　health　of　what　is　capable　of　being　made　healthy　（for　the　operation　of　that　which　is　capable　of　originating　change　terminates　and　has　its　seat　in　what　is　changed　or　altered）；　further；　since　it　is　the　soul　by　or　with　which　primarily　we　live；　perceive；　and　think：…it　follows　that　the　soul　must　be　a　ratio　or　formulable　essence；　not　a　matter　or　subject。　For；　as　we　said；　word　substance　has　three　meanings　form；　matter；　and　the　complex　of　both　and　of　these　three　what　is　called　matter　is　potentiality；　what　is　called　form　actuality。　Since　then　the　complex　here　is　the　living　thing；　the　body　cannot　be　the　actuality　of　the　soul；　it　is　the　soul　which　is　the　actuality　of　a　certain　kind　of　body。　Hence　the　rightness　of　the　view　that　the　soul　cannot　be　without　a　body；　while　it　csnnot　he　a　body；　it　is　not　a　body　but　something　relative　to　a　body。　That　is　why　it　is　in　a　body；　and　a　body　of　a　definite　kind。　It　was　a　mistake；　therefore；　to　do　as　former　thinkers　did；　merely　to　fit　it　into　a　body　without　adding　a　definite　specification　of　the　kind　or　character　of　that　body。　Reflection　confirms　the　observed　fact；　the　actuality　of　any　given　thing　can　only　be　realized　in　what　is　already　potentially　that　thing；　i。e。　in　a　matter　of　its　own　appropriate　to　it。　From　all　this　it　follows　that　soul　is　an　actuality　or　formulable　essence　of　something　that　possesses　a　potentiality　of　being　besouled。
  3
  Of　the　psychic　powers　above　enumerated　some　kinds　of　living　things；　as　we　have　said；　possess　all；　some