bject　some　other　part）。　Further；　even　when　the　mind　does　command　and　thought　bids　us　pursue　or　avoid　something；　sometimes　no　movement　is　produced；　we　act　in　accordance　with　desire；　as　in　the　case　of　moral　weakness。　And；　generally；　we　observe　that　the　possessor　of　medical　knowledge　is　not　necessarily　healing；　which　shows　that　something　else　is　required　to　produce　action　in　accordance　with　knowledge；　the　knowledge　alone　is　not　the　cause。　Lastly；　appetite　too　is　incompetent　to　account　fully　for　movement；　for　those　who　successfully　resist　temptation　have　appetite　and　desire　and　yet　follow　mind　and　refuse　to　enact　that　for　which　they　have　appetite。
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  These　two　at　all　events　appear　to　be　sources　of　movement：　appetite　and　mind　（if　one　may　venture　to　regard　imagination　as　a　kind　of　thinking；　for　many　men　follow　their　imaginations　contrary　to　knowledge；　and　in　all　animals　other　than　man　there　is　no　thinking　or　calculation　but　only　imagination）。　　　Both　of　these　then　are　capable　of　originating　local　movement；　mind　and　appetite：　（1）　mind；　that　is；　which　calculates　means　to　an　end；　i。e。　mind　practical　（it　differs　from　mind　speculative　in　the　character　of　its　end）；　while　（2）　appetite　is　in　every　form　of　it　relative　to　an　end：　for　that　which　is　the　object　of　appetite　is　the　stimulant　of　mind　practical；　and　that　which　is　last　in　the　process　of　thinking　is　the　beginning　of　the　action。　It　follows　that　there　is　a　justification　for　regarding　these　two　as　the　sources　of　movement；　i。e。　appetite　and　practical　thought；　for　the　object　of　appetite　starts　a　movement　and　as　a　result　of　that　thought　gives　rise　to　movement；　the　object　of　appetite　being　it　a　source　of　stimulation。　So　too　when　imagination　originates　movement；　it　necessarily　involves　appetite。　　　That　which　moves　therefore　is　a　single　faculty　and　the　faculty　of　appetite；　for　if　there　had　been　two　sources　of　movement…mind　and　appetite…they　would　have　produced　movement　in　virtue　of　some　common　character。　As　it　is；　mind　is　never　found　producing　movement　without　appetite　（for　wish　is　a　form　of　appetite；　and　when　movement　is　produced　according　to　calculation　it　is　also　according　to　wish）；　but　appetite　can　originate　movement　contrary　to　calculation；　for　desire　is　a　form　of　appetite。　Now　mind　is　always　right；　but　appetite　and　imagination　may　be　either　right　or　wrong。　That　is　why；　though　in　any　case　it　is　the　object　of　appetite　which　originates　movement；　this　object　may　be　either　the　real　or　the　apparent　good。　To　produce　movement　the　object　must　be　more　than　this：　it　must　be　good　that　can　be　brought　into　being　by　action；　and　only　what　can　be　otherwise　than　as　it　is　can　thus　be　brought　into　being。　That　then　such　a　power　in　the　soul　as　has　been　described；　i。e。　that　called　appetite；　originates　movement　is　clear。　Those　who　distinguish　parts　in　the　soul；　if　they　distinguish　and　divide　in　accordance　with　differences　of　power；　find　themselves　with　a　very　large　number　of　parts；　a　nutritive；　a　sensitive；　an　intellective；　a　deliberative；　and　now　an　appetitive　part；　for　these　are　more　different　from　one　another　than　the　faculties　of　desire　and　passion。　　　Since　appetites　run　counter　to　one　another；　which　happens　when　a　principle　of　reason　and　a　desire　are　contrary　and　is　possible　only　in　beings　with　a　sense　of　time　（for　while　mind　bids　us　hold　back　because　of　what　is　future；　desire　is　influenced　by　what　is　just　at　hand：　a　pleasant　object　which　is　just　at　hand　presents　itself　as　both　pleasant　and　good；　without　condition　in　either　case；　because　of　want　of　foresight　into　what　is　farther　away　in　time）；　it　follows　that　while　that　which　originates　movement　must　be　specifically　one；　viz。　the　faculty　of　appetite　as　such　（or　rather　farthest　back　of　all　the　object　of　that　faculty；　for　it　is　it　that　itself　remaining　unmoved　originates　the　movement　by　being　apprehended　in　thought　or　imagination）；　the　things　that　originate　movement　are　numerically　many。　　　All　movement　involves　three　factors；　（1）　that　which　originates　the　movement；　（2）　that　by　means　of　which　it　originates　it；　and　（3）　that　which　is　moved。　The　expression　'that　which　originates　the　movement'　is　ambiguous：　it　may　mean　either　（a）　something　which　itself　is　unmoved　or　（b）　that　which　at　once　moves　and　is　moved。　Here　that　which　moves　without　itself　being　moved　is　the　realizable　good；　that　which　at　once　moves　and　is　moved　is　the　faculty　of　appetite　（for　that　which　is　influenced　by　appetite　so　far　as　it　is　actually　so　influenced　is　set　in　movement；　and　appetite　in　the　sense　of　actual　appetite　is　a　kind　of　movement）；　while　that　which　is　in　motion　is　the　animal。　The　instrument　which　appetite　employs　to　produce　movement　is　no　longer　psychical　but　bodily：　hence　the　examination　of　it　falls　within　the　province　of　the　functions　common　to　body　and　soul。　To　state　the　matter　summarily　at　present；　that　which　is　the　instrument　in　the　production　of　movement　is　to　be　found　where　a　beginning　and　an　end　coincide　as　e。g。　in　a　ball　and　socket　joint；　for　there　the　convex　and　the　concave　sides　are　respectively　an　end　and　a　beginning　（that　is　why　while　the　one　remains　at　rest；　the　other　is　moved）：　they　are　separate　in　definition　but　not　separable　spatially。　For　everything　is　moved　by　pushing　and　pulling。　Hence　just　as　in　the　case　of　a　wheel；　so　here　there　must　be　a　point　which　remains　at　rest；　and　from　that　point　the　movement　must　originate。　　　To　sum　up；　then；　and　repeat　what　I　have　said；　inasmuch　as　an　animal　is　capable　of　appetite　it　is　capable　of　self…movement；　it　is　not　capable　of　appetite　without　possessing　imagination；　and　all　imagination　is　either　（1）　calculative　or　（2）　sensitive。　In　the　latter　an　animals；　and　not　only　man；　partake。
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  We　must　consider　also　in　the　case　of　imperfect　animals；　sc。　those　which　have　no　sense　but　touch；　what　it　is　that　in　them　originates　movement。　Can　they　have　imagination　or　not？　or　desire？　Clearly　they　have　feelings　of　pleasure　and　pain；　and　if　they　have　these　they　must　have　desire。　But　how　can　they　have　imagination？　Must　not　we　say　that；　as　their　movements　are　indefinite；　they　have　imagination　and　desire；　but　indefinitely？　　　Sensitive　imagination；　as　we　have　said；　is　found　in　all　animals；　deliberative　imagination　only　in　those　that　are　calculative：　for　whether　this　or　that　shall　be　enacted　is　already　a　task　requiring　calculation；　and　there　must　be　a　single　standard　to　measure　by；　for　that　is　pursued　which　is　greater。　It　follows　that　what　acts　in　this　way　must　be　able　to　make　a　unity　out　of　several　images。　　　This　is　the　reason　why　imagination　is　held　not　to　involve　opinion；　in　that　it　does　not　involve　opinion　based　on　inference；　though　opinion　involves　imagination。　Hence　appetite　contains　no　deliberative　element。　Sometimes　it　overpowers　wish　and　sets　it　in　movement：　at　times　wish　acts　thus　upon　appetite；　like　one　sphere　imparting　its　movement　to　another；　or　appetite　acts　thus　upon　appetite；　i。e。　in　the　condition　of　moral　weakness　（though　by　nature　the　higher　faculty　is　always　more　authoritative　and　gives　rise　to　movement）。　Thus　three　modes　of　movement　are　possible。　　　The　faculty　of　knowing　is　never　moved　but　remains　at　rest。　Since　the　one　premiss　or　judgement　is　universal　and　the　other　deals　with　the　particular　（for　the　first　tells　us　that　such　and　such　a　kind　of　man　should　do　such　and　such　a　kind　of　act；　and　the　second　that　this　is　an　act　of　the　kind　meant；　and　I　a　person　of　the　type　intended）；　it　is　the　latter　opinion　that　really　originates　movement；　not　the　universal；　or　rather　it　is　both；　but　the　one　does　so　while　it　remains　in　a　state　more　like　rest；　while　the　other　partakes　in　movement。
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  The　nutritive　soul　then　must　be　possessed　by　everything　that　is　alive；　and　every　such　thing　is　endowed　with　soul　from　its　birth　to　its　death。　For　what　has　been　born　must　grow；　reach　maturity；　and　decay…all　of　which　are　impossible　without　nutrition。　Therefore　the　nutritive　faculty　must　be　found　in　everything　that　grows　and　decays。　　　But　sensation　need　not　be　found　in　all　things　that　live。　For　it　is　impossible　for　touch　to　belong　either　（1）　to　those　whose　body　is　uncompounded　or　（2）　to　those　which　are　incapable　of　taking　in　the　forms　without　their　matter。　　　But　animals　must　be　endowed　with　sensation；　since　Nature　does　nothing　in　vain。　For　all　things　that　exist　by　Nature　are　means　to　an　end；　or　will　be　concomitants　of　means　to　an　end。　Every　body　capable　of　forward　movement　would；　if　unendowed　with　sensation；　perish　and　fail　to　reach　its　end；　which　is　the　aim　of　Nature；　for　how　could　it　obtain　nutriment？　Stationary　living　things；　it　is　true；　have　as　their　nutriment　that　from　which　they　have　arisen；　but　it　is　not　possible　that　a　body　which　is　not　stationary　but　produced　by　generation　should　have　a　soul　and　a　discerning　mind　without　also　having　sensation。　（Nor　yet　even　if　it　were　not　produced　by　generation。　Why　should　it　not　have　sensation？　Because　it　were　better　so　either　for　the　body　or　for　the　soul？　But　clearly　it　would　not　be　better　for　either：　the　absence　of　sensation　will　not　enable　the　one　to　think　better　or　the　other　to　exist　better。）　Therefore　no　body　which　is　not　stationary　has　soul　without　sensation。　　　But　if　a　body　has　sensation；　it　must　be　either　sim