first　of　all　that　is。　　　All；　both　those　who　assert　that　the　soul；　because　of　its　knowledge　or　perception　of　what　is　compounded　out　of　the　elements；　and　is　those　who　assert　that　it　is　of　all　things　the　most　originative　of　movement；　fail　to　take　into　consideration　all　kinds　of　soul。　In　fact　（1）　not　all　beings　that　perceive　can　originate　movement；　there　appear　to　be　certain　animals　which　stationary；　and　yet　local　movement　is　the　only　one；　so　it　seems；　which　the　soul　originates　in　animals。　And　（2）　the　same　object…on　holds　against　all　those　who　construct　mind　and　the　perceptive　faculty　out　of　the　elements；　for　it　appears　that　plants　live；　and　yet　are　not　endowed　with　locomotion　or　perception；　while　a　large　number　of　animals　are　without　discourse　of　reason。　Even　if　these　points　were　waived　and　mind　admitted　to　be　a　part　of　the　soul　（and　so　too　the　perceptive　faculty）；　still；　even　so；　there　would　be　kinds　and　parts　of　soul　of　which　they　had　failed　to　give　any　account。　　　The　same　objection　lies　against　the　view　expressed　in　the　'Orphic'　poems：　there　it　is　said　that　the　soul　comes　in　from　the　whole　when　breathing　takes　place；　being　borne　in　upon　the　winds。　Now　this　cannot　take　place　in　the　case　of　plants；　nor　indeed　in　the　case　of　certain　classes　of　animal；　for　not　all　classes　of　animal　breathe。　This　fact　has　escaped　the　notice　of　the　holders　of　this　view。　　　If　we　must　construct　the　soul　out　of　the　elements；　there　is　no　necessity　to　suppose　that　all　the　elements　enter　into　its　construction；　one　element　in　each　pair　of　contraries　will　suffice　to　enable　it　to　know　both　that　element　itself　and　its　contrary。　By　means　of　the　straight　line　we　know　both　itself　and　the　curved…the　carpenter's　rule　enables　us　to　test　both…but　what　is　curved　does　not　enable　us　to　distinguish　either　itself　or　the　straight。　Certain　thinkers　say　that　soul　is　intermingled　in　the　whole　universe；　and　it　is　perhaps　for　that　reason　that　Thales　came　to　the　opinion　that　all　things　are　full　of　gods。　This　presents　some　difficulties：　Why　does　the　soul　when　it　resides　in　air　or　fire　not　form　an　animal；　while　it　does　so　when　it　resides　in　mixtures　of　the　elements；　and　that　although　it　is　held　to　be　of　higher　quality　when　contained　in　the　former？　（One　might　add　the　question；　why　the　soul　in　air　is　maintained　to　be　higher　and　more　immortal　than　that　in　animals。）　Both　possible　ways　of　replying　to　the　former　question　lead　to　absurdity　or　paradox；　for　it　is　beyond　paradox　to　say　that　fire　or　air　is　an　animal；　and　it　is　absurd　to　refuse　the　name　of　animal　to　what　has　soul　in　it。　The　opinion　that　the　elements　have　soul　in　them　seems　to　have　arisen　from　the　doctrine　that　a　whole　must　be　homogeneous　with　its　parts。　If　it　is　true　that　animals　become　animate　by　drawing　into　themselves　a　portion　of　what　surrounds　them；　the　partisans　of　this　view　are　bound　to　say　that　the　soul　of　the　Whole　too　is　homogeneous　with　all　its　parts。　If　the　air　sucked　in　is　homogeneous；　but　soul　heterogeneous；　clearly　while　some　part　of　soul　will　exist　in　the　inbreathed　air；　some　other　part　will　not。　The　soul　must　either　be　homogeneous；　or　such　that　there　are　some　parts　of　the　Whole　in　which　it　is　not　to　be　found。　　　From　what　has　been　said　it　is　now　clear　that　knowing　as　an　attribute　of　soul　cannot　be　explained　by　soul's　being　composed　of　the　elements；　and　that　it　is　neither　sound　nor　true　to　speak　of　soul　as　moved。　But　since　（a）　knowing；　perceiving；　opining；　and　further　（b）　desiring；　wishing；　and　generally　all　other　modes　of　appetition；　belong　to　soul；　and　（c）　the　local　movements　of　animals；　and　（d）　growth；　maturity；　and　decay　are　produced　by　the　soul；　we　must　ask　whether　each　of　these　is　an　attribute　of　the　soul　as　a　whole；　i。e。　whether　it　is　with　the　whole　soul　we　think；　perceive；　move　ourselves；　act　or　are　acted　upon；　or　whether　each　of　them　requires　a　different　part　of　the　soul？　So　too　with　regard　to　life。　Does　it　depend　on　one　of　the　parts　of　soul？　Or　is　it　dependent　on　more　than　one？　Or　on　all？　Or　has　it　some　quite　other　cause？　　　Some　hold　that　the　soul　is　divisible；　and　that　one　part　thinks；　another　desires。　If；　then；　its　nature　admits　of　its　being　divided；　what　can　it　be　that　holds　the　parts　together？　Surely　not　the　body；　on　the　contrary　it　seems　rather　to　be　the　soul　that　holds　the　body　together；　at　any　rate　when　the　soul　departs　the　body　disintegrates　and　decays。　If；　then；　there　is　something　else　which　makes　the　soul　one；　this　unifying　agency　would　have　the　best　right　to　the　name　of　soul；　and　we　shall　have　to　repeat　for　it　the　question：　Is　it　one　or　multipartite？　If　it　is　one；　why　not　at　once　admit　that　'the　soul'　is　one？　If　it　has　parts；　once　more　the　question　must　be　put：　What　holds　its　parts　together；　and　so　ad　infinitum？　　　The　question　might　also　be　raised　about　the　parts　of　the　soul：　What　is　the　separate　role　of　each　in　relation　to　the　body？　For；　if　the　whole　soul　holds　together　the　whole　body；　we　should　expect　each　part　of　the　soul　to　hold　together　a　part　of　the　body。　But　this　seems　an　impossibility；　it　is　difficult　even　to　imagine　what　sort　of　bodily　part　mind　will　hold　together；　or　how　it　will　do　this。　　　It　is　a　fact　of　observation　that　plants　and　certain　insects　go　on　living　when　divided　into　segments；　this　means　that　each　of　the　segments　has　a　soul　in　it　identical　in　species；　though　not　numerically　identical　in　the　different　segments；　for　both　of　the　segments　for　a　time　possess　the　power　of　sensation　and　local　movement。　That　this　does　not　last　is　not　surprising；　for　they　no　longer　possess　the　organs　necessary　for　self…maintenance。　But；　all　the　same；　in　each　of　the　bodily　parts　there　are　present　all　the　parts　of　soul；　and　the　souls　so　present　are　homogeneous　with　one　another　and　with　the　whole；　this　means　that　the　several　parts　of　the　soul　are　indisseverable　from　one　another；　although　the　whole　soul　is　divisible。　It　seems　also　that　the　principle　found　in　plants　is　also　a　kind　of　soul；　for　this　is　the　only　principle　which　is　common　to　both　animals　and　plants；　and　this　exists　in　isolation　from　the　principle　of　sensation；　though　there　nothing　which　has　the　latter　without　the　former。
  Book　II　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　1
  LET　the　foregoing　suffice　as　our　account　of　the　views　concerning　the　soul　which　have　been　handed　on　by　our　predecessors；　let　us　now　dismiss　them　and　make　as　it　were　a　completely　fresh　start；　endeavouring　to　give　a　precise　answer　to　the　question；　What　is　soul？　i。e。　to　formulate　the　most　general　possible　definition　of　it。　　　We　are　in　the　habit　of　recognizing；　as　one　determinate　kind　of　what　is；　substance；　and　that　in　several　senses；　（a）　in　the　sense　of　matter　or　that　which　in　itself　is　not　'a　this'；　and　（b）　in　the　sense　of　form　or　essence；　which　is　that　precisely　in　virtue　of　which　a　thing　is　called　'a　this'；　and　thirdly　（c）　in　the　sense　of　that　which　is　compounded　of　both　（a）　and　（b）。　Now　matter　is　potentiality；　form　actuality；　of　the　latter　there　are　two　grades　related　to　one　another　as　e。g。　knowledge　to　the　exercise　of　knowledge。　　　Among　substances　are　by　general　consent　reckoned　bodies　and　especially　natural　bodies；　for　they　are　the　principles　of　all　other　bodies。　Of　natural　bodies　some　have　life　in　them；　others　not；　by　life　we　mean　self…nutrition　and　growth　（with　its　correlative　decay）。　It　follows　that　every　natural　body　which　has　life　in　it　is　a　substance　in　the　sense　of　a　composite。　　　But　since　it　is　also　a　body　of　such　and　such　a　kind；　viz。　having　life；　the　body　cannot　be　soul；　the　body　is　the　subject　or　matter；　not　what　is　attributed　to　it。　Hence　the　soul　must　be　a　substance　in　the　sense　of　the　form　of　a　natural　body　having　life　potentially　within　it。　But　substance　is　actuality；　and　thus　soul　is　the　actuality　of　a　body　as　above　characterized。　Now　the　word　actuality　has　two　senses　corresponding　respectively　to　the　possession　of　knowledge　and　the　actual　exercise　of　knowledge。　It　is　obvious　that　the　soul　is　actuality　in　the　first　sense；　viz。　that　of　knowledge　as　possessed；　for　both　sleeping　and　waking　presuppose　the　existence　of　soul；　and　of　these　waking　corresponds　to　actual　knowing；　sleeping　to　knowledge　possessed　but　not　employed；　and；　in　the　history　of　the　individual；　knowledge　comes　before　its　employment　or　exercise。　　　That　is　why　the　soul　is　the　first　grade　of　actuality　of　a　natural　body　having　life　potentially　in　it。　The　body　so　described　is　a　body　which　is　organized。　The　parts　of　plants　in　spite　of　their　extreme　simplicity　are　'organs'；　e。g。　the　leaf　serves　to　shelter　the　pericarp；　the　pericarp　to　shelter　the　fruit；　while　the　roots　of　plants　are　analogous　to　the　mouth　of　animals；　both　serving　for　the　absorption　of　food。　If；　then；　we　have　to　give　a　general　formula　applicable　to　all　kinds　of　soul；　we　must　describe　it　as　the　first　grade　of　actuality　of　a　natural　organized　body。　That　is　why　we　can　wholly　dismiss　as　unnecessary　the　question　whether　the　soul　and　the　body　are　one：　it　is　as　meaningless　as　to　ask　whether　the　wax　and　the　shape　given　to　it　by　the　stamp　are　one；　or　generally　the　matter　of　a　thing　and　that　of　which　it　is　the　matter。　Unity　has　many　senses　（as　many　as　'is'　has）；　but　the　most　proper　and　fundamental　sense　of　both　is　the　relation　of　an　actuality　to　that　of　which　it　is　the　actuality。　We　have　now　given　an　answer　to　the　quest