is；　as　we　saw；　an　activity　of　what　is　imperfect；　activity　in　the　unqualified　sense；　i。e。　that　of　what　has　been　perfected；　is　different　from　movement。　　　To　perceive　then　is　like　bare　asserting　or　knowing；　but　when　the　object　is　pleasant　or　painful；　the　soul　makes　a　quasi…affirmation　or　negation；　and　pursues　or　avoids　the　object。　To　feel　pleasure　or　pain　is　to　act　with　the　sensitive　mean　towards　what　is　good　or　bad　as　such。　Both　avoidance　and　appetite　when　actual　are　identical　with　this：　the　faculty　of　appetite　and　avoidance　are　not　different；　either　from　one　another　or　from　the　faculty　of　sense…perception；　but　their　being　is　different。　　　To　the　thinking　soul　images　serve　as　if　they　were　contents　of　perception　（and　when　it　asserts　or　denies　them　to　be　good　or　bad　it　avoids　or　pursues　them）。　That　is　why　the　soul　never　thinks　without　an　image。　The　process　is　like　that　in　which　the　air　modifies　the　pupil　in　this　or　that　way　and　the　pupil　transmits　the　modification　to　some　third　thing　（and　similarly　in　hearing）；　while　the　ultimate　point　of　arrival　is　one；　a　single　mean；　with　different　manners　of　being。　　　With　what　part　of　itself　the　soul　discriminates　sweet　from　hot　I　have　explained　before　and　must　now　describe　again　as　follows：　That　with　which　it　does　so　is　a　sort　of　unity；　but　in　the　way　just　mentioned；　i。e。　as　a　connecting　term。　And　the　two　faculties　it　connects；　being　one　by　analogy　and　numerically；　are　each　to　each　as　the　qualities　discerned　are　to　one　another　（for　what　difference　does　it　make　whether　we　raise　the　problem　of　discrimination　between　disparates　or　between　contraries；　e。g。　white　and　black？）。　Let　then　C　be　to　D　as　is　to　B：　it　follows　alternando　that　C：　A：：　D：　B。　If　then　C　and　D　belong　to　one　subject；　the　case　will　be　the　same　with　them　as　with　and　B；　and　B　form　a　single　identity　with　different　modes　of　being；　so　too　will　the　former　pair。　The　same　reasoning　holds　if　be　sweet　and　B　white。　　　The　faculty　of　thinking　then　thinks　the　forms　in　the　images；　and　as　in　the　former　case　what　is　to　be　pursued　or　avoided　is　marked　out　for　it；　so　where　there　is　no　sensation　and　it　is　engaged　upon　the　images　it　is　moved　to　pursuit　or　avoidance。　E。g。。　perceiving　by　sense　that　the　beacon　is　fire；　it　recognizes　in　virtue　of　the　general　faculty　of　sense　that　it　signifies　an　enemy；　because　it　sees　it　moving；　but　sometimes　by　means　of　the　images　or　thoughts　which　are　within　the　soul；　just　as　if　it　were　seeing；　it　calculates　and　deliberates　what　is　to　come　by　reference　to　what　is　present；　and　when　it　makes　a　pronouncement；　as　in　the　case　of　sensation　it　pronounces　the　object　to　be　pleasant　or　painful；　in　this　case　it　avoids　or　persues　and　so　generally　in　cases　of　action。　　　That　too　which　involves　no　action；　i。e。　that　which　is　true　or　false；　is　in　the　same　province　with　what　is　good　or　bad：　yet　they　differ　in　this；　that　the　one　set　imply　and　the　other　do　not　a　reference　to　a　particular　person。　　　The　so…called　abstract　objects　the　mind　thinks　just　as；　if　one　had　thought　of　the　snubnosed　not　as　snub…nosed　but　as　hollow；　one　would　have　thought　of　an　actuality　without　the　flesh　in　which　it　is　embodied：　it　is　thus　that　the　mind　when　it　is　thinking　the　objects　of　Mathematics　thinks　as　separate　elements　which　do　not　exist　separate。　In　every　case　the　mind　which　is　actively　thinking　is　the　objects　which　it　thinks。　Whether　it　is　possible　for　it　while　not　existing　separate　from　spatial　conditions　to　think　anything　that　is　separate；　or　not；　we　must　consider　later。
  8
  Let　us　now　summarize　our　results　about　soul；　and　repeat　that　the　soul　is　in　a　way　all　existing　things；　for　existing　things　are　either　sensible　or　thinkable；　and　knowledge　is　in　a　way　what　is　knowable；　and　sensation　is　in　a　way　what　is　sensible：　in　what　way　we　must　inquire。　　　Knowledge　and　sensation　are　divided　to　correspond　with　the　realities；　potential　knowledge　and　sensation　answering　to　potentialities；　actual　knowledge　and　sensation　to　actualities。　Within　the　soul　the　faculties　of　knowledge　and　sensation　are　potentially　these　objects；　the　one　what　is　knowable；　the　other　what　is　sensible。　They　must　be　either　the　things　themselves　or　their　forms。　The　former　alternative　is　of　course　impossible：　it　is　not　the　stone　which　is　present　in　the　soul　but　its　form。　　　It　follows　that　the　soul　is　analogous　to　the　hand；　for　as　the　hand　is　a　tool　of　tools；　so　the　mind　is　the　form　of　forms　and　sense　the　form　of　sensible　things。　　　Since　according　to　common　agreement　there　is　nothing　outside　and　separate　in　existence　from　sensible　spatial　magnitudes；　the　objects　of　thought　are　in　the　sensible　forms；　viz。　both　the　abstract　objects　and　all　the　states　and　affections　of　sensible　things。　Hence　（1）　no　one　can　learn　or　understand　anything　in　the　absence　of　sense；　and　（when　the　mind　is　actively　aware　of　anything　it　is　necessarily　aware　of　it　along　with　an　image；　for　images　are　like　sensuous　contents　except　in　that　they　contain　no　matter。　　　Imagination　is　different　from　assertion　and　denial；　for　what　is　true　or　false　involves　a　synthesis　of　concepts。　In　what　will　the　primary　concepts　differ　from　images？　Must　we　not　say　that　neither　these　nor　even　our　other　concepts　are　images；　though　they　necessarily　involve　them？
  9
  The　soul　of　animals　is　characterized　by　two　faculties；　（a）　the　faculty　of　discrimination　which　is　the　work　of　thought　and　sense；　and　（b）　the　faculty　of　originating　local　movement。　Sense　and　mind　we　have　now　sufficiently　examined。　Let　us　next　consider　what　it　is　in　the　soul　which　originates　movement。　Is　it　a　single　part　of　the　soul　separate　either　spatially　or　in　definition？　Or　is　it　the　soul　as　a　whole？　If　it　is　a　part；　is　that　part　different　from　those　usually　distinguished　or　already　mentioned　by　us；　or　is　it　one　of　them？　The　problem　at　once　presents　itself；　in　what　sense　we　are　to　speak　of　parts　of　the　soul；　or　how　many　we　should　distinguish。　For　in　a　sense　there　is　an　infinity　of　parts：　it　is　not　enough　to　distinguish；　with　some　thinkers；　the　calculative；　the　passionate；　and　the　desiderative；　or　with　others　the　rational　and　the　irrational；　for　if　we　take　the　dividing　lines　followed　by　these　thinkers　we　shall　find　parts　far　more　distinctly　separated　from　one　another　than　these；　namely　those　we　have　just　mentioned：　（1）　the　nutritive；　which　belongs　both　to　plants　and　to　all　animals；　and　（2）　the　sensitive；　which　cannot　easily　be　classed　as　either　irrational　or　rational；　further　（3）　the　imaginative；　which　is；　in　its　being；　different　from　all；　while　it　is　very　hard　to　say　with　which　of　the　others　it　is　the　same　or　not　the　same；　supposing　we　determine　to　posit　separate　parts　in　the　soul；　and　lastly　（4）　the　appetitive；　which　would　seem　to　be　distinct　both　in　definition　and　in　power　from　all　hitherto　enumerated。　　　It　is　absurd　to　break　up　the　last…mentioned　faculty：　as　these　thinkers　do；　for　wish　is　found　in　the　calculative　part　and　desire　and　passion　in　the　irrational；　and　if　the　soul　is　tripartite　appetite　will　be　found　in　all　three　parts。　Turning　our　attention　to　the　present　object　of　discussion；　let　us　ask　what　that　is　which　originates　local　movement　of　the　animal。　　　The　movement　of　growth　and　decay；　being　found　in　all　living　things；　must　be　attributed　to　the　faculty　of　reproduction　and　nutrition；　which　is　common　to　all：　inspiration　and　expiration；　sleep　and　waking；　we　must　consider　later：　these　too　present　much　difficulty：　at　present　we　must　consider　local　movement；　asking　what　it　is　that　originates　forward　movement　in　the　animal。　　　That　it　is　not　the　nutritive　faculty　is　obvious；　for　this　kind　of　movement　is　always　for　an　end　and　is　accompanied　either　by　imagination　or　by　appetite；　for　no　animal　moves　except　by　compulsion　unless　it　has　an　impulse　towards　or　away　from　an　object。　Further；　if　it　were　the　nutritive　faculty；　even　plants　would　have　been　capable　of　originating　such　movement　and　would　have　possessed　the　organs　necessary　to　carry　it　out。　Similarly　it　cannot　be　the　sensitive　faculty　either；　for　there　are　many　animals　which　have　sensibility　but　remain　fast　and　immovable　throughout　their　lives。　　　If　then　Nature　never　makes　anything　without　a　purpose　and　never　leaves　out　what　is　necessary　（except　in　the　case　of　mutilated　or　imperfect　growths；　and　that　here　we　have　neither　mutilation　nor　imperfection　may　be　argued　from　the　facts　that　such　animals　（a）　can　reproduce　their　species　and　（b）　rise　to　completeness　of　nature　and　decay　to　an　end）；　it　follows　that；　had　they　been　capable　of　originating　forward　movement；　they　would　have　possessed　the　organs　necessary　for　that　purpose。　Further；　neither　can　the　calculative　faculty　or　what　is　called　'mind'　be　the　cause　of　such　movement；　for　mind　as　speculative　never　thinks　what　is　practicable；　it　never　says　anything　about　an　object　to　be　avoided　or　pursued；　while　this　movement　is　always　in　something　which　is　avoiding　or　pursuing　an　object。　No；　not　even　when　it　is　aware　of　such　an　object　does　it　at　once　enjoin　pursuit　or　avoidance　of　it；　e。g。　the　mind　often　thinks　of　something　terrifying　or　pleasant　without　enjoining　the　emotion　of　fear。　It　is　the　heart　that　is　moved　（or　in　the　case　of　a　pleasant　object　some　other　part）。　Further；　even　when　the　mind　does　command　and　thought　bids　us　pursue　or　avoid