3
  Of　the　psychic　powers　above　enumerated　some　kinds　of　living　things；　as　we　have　said；　possess　all；　some　less　than　all；　others　one　only。　Those　we　have　mentioned　are　the　nutritive；　the　appetitive；　the　sensory；　the　locomotive；　and　the　power　of　thinking。　Plants　have　none　but　the　first；　the　nutritive；　while　another　order　of　living　things　has　this　plus　the　sensory。　If　any　order　of　living　things　has　the　sensory；　it　must　also　have　the　appetitive；　for　appetite　is　the　genus　of　which　desire；　passion；　and　wish　are　the　species；　now　all　animals　have　one　sense　at　least；　viz。　touch；　and　whatever　has　a　sense　has　the　capacity　for　pleasure　and　pain　and　therefore　has　pleasant　and　painful　objects　present　to　it；　and　wherever　these　are　present；　there　is　desire；　for　desire　is　just　appetition　of　what　is　pleasant。　Further；　all　animals　have　the　sense　for　food　（for　touch　is　the　sense　for　food）；　the　food　of　all　living　things　consists　of　what　is　dry；　moist；　hot；　cold；　and　these　are　the　qualities　apprehended　by　touch；　all　other　sensible　qualities　are　apprehended　by　touch　only　indirectly。　Sounds；　colours；　and　odours　contribute　nothing　to　nutriment；　flavours　fall　within　the　field　of　tangible　qualities。　Hunger　and　thirst　are　forms　of　desire；　hunger　a　desire　for　what　is　dry　and　hot；　thirst　a　desire　for　what　is　cold　and　moist；　flavour　is　a　sort　of　seasoning　added　to　both。　We　must　later　clear　up　these　points；　but　at　present　it　may　be　enough　to　say　that　all　animals　that　possess　the　sense　of　touch　have　also　appetition。　The　case　of　imagination　is　obscure；　we　must　examine　it　later。　Certain　kinds　of　animals　possess　in　addition　the　power　of　locomotion；　and　still　another　order　of　animate　beings；　i。e。　man　and　possibly　another　order　like　man　or　superior　to　him；　the　power　of　thinking；　i。e。　mind。　It　is　now　evident　that　a　single　definition　can　be　given　of　soul　only　in　the　same　sense　as　one　can　be　given　of　figure。　For；　as　in　that　case　there　is　no　figure　distinguishable　and　apart　from　triangle；　&c。；　so　here　there　is　no　soul　apart　from　the　forms　of　soul　just　enumerated。　It　is　true　that　a　highly　general　definition　can　be　given　for　figure　which　will　fit　all　figures　without　expressing　the　peculiar　nature　of　any　figure。　So　here　in　the　case　of　soul　and　its　specific　forms。　Hence　it　is　absurd　in　this　and　similar　cases　to　demand　an　absolutely　general　definition　which　will　fail　to　express　the　peculiar　nature　of　anything　that　is；　or　again；　omitting　this；　to　look　for　separate　definitions　corresponding　to　each　infima　species。　The　cases　of　figure　and　soul　are　exactly　parallel；　for　the　particulars　subsumed　under　the　common　name　in　both　cases…figures　and　living　beings…constitute　a　series；　each　successive　term　of　which　potentially　contains　its　predecessor；　e。g。　the　square　the　triangle；　the　sensory　power　the　self…nutritive。　Hence　we　must　ask　in　the　case　of　each　order　of　living　things；　What　is　its　soul；　i。e。　What　is　the　soul　of　plant；　animal；　man？　Why　the　terms　are　related　in　this　serial　way　must　form　the　subject　of　later　examination。　But　the　facts　are　that　the　power　of　perception　is　never　found　apart　from　the　power　of　self…nutrition；　while…in　plants…the　latter　is　found　isolated　from　the　former。　Again；　no　sense　is　found　apart　from　that　of　touch；　while　touch　is　found　by　itself；　many　animals　have　neither　sight；　hearing；　nor　smell。　Again；　among　living　things　that　possess　sense　some　have　the　power　of　locomotion；　some　not。　Lastly；　certain　living　beings…a　small　minority…possess　calculation　and　thought；　for　（among　mortal　beings）　those　which　possess　calculation　have　all　the　other　powers　above　mentioned；　while　the　converse　does　not　hold…indeed　some　live　by　imagination　alone；　while　others　have　not　even　imagination。　The　mind　that　knows　with　immediate　intuition　presents　a　different　problem。　　　It　is　evident　that　the　way　to　give　the　most　adequate　definition　of　soul　is　to　seek　in　the　case　of　each　of　its　forms　for　the　most　appropriate　definition。
  4
  It　is　necessary　for　the　student　of　these　forms　of　soul　first　to　find　a　definition　of　each；　expressive　of　what　it　is；　and　then　to　investigate　its　derivative　properties；　&c。　But　if　we　are　to　express　what　each　is；　viz。　what　the　thinking　power　is；　or　the　perceptive；　or　the　nutritive；　we　must　go　farther　back　and　first　give　an　account　of　thinking　or　perceiving；　for　in　the　order　of　investigation　the　question　of　what　an　agent　does　precedes　the　question；　what　enables　it　to　do　what　it　does。　If　this　is　correct；　we　must　on　the　same　ground　go　yet　another　step　farther　back　and　have　some　clear　view　of　the　objects　of　each；　thus　we　must　start　with　these　objects；　e。g。　with　food；　with　what　is　perceptible；　or　with　what　is　intelligible。　　　It　follows　that　first　of　all　we　must　treat　of　nutrition　and　reproduction；　for　the　nutritive　soul　is　found　along　with　all　the　others　and　is　the　most　primitive　and　widely　distributed　power　of　soul；　being　indeed　that　one　in　virtue　of　which　all　are　said　to　have　life。　The　acts　in　which　it　manifests　itself　are　reproduction　and　the　use　of　food…reproduction；　I　say；　because　for　any　living　thing　that　has　reached　its　normal　development　and　which　is　unmutilated；　and　whose　mode　of　generation　is　not　spontaneous；　the　most　natural　act　is　the　production　of　another　like　itself；　an　animal　producing　an　animal；　a　plant　a　plant；　in　order　that；　as　far　as　its　nature　allows；　it　may　partake　in　the　eternal　and　divine。　That　is　the　goal　towards　which　all　things　strive；　that　for　the　sake　of　which　they　do　whatsoever　their　nature　renders　possible。　The　phrase　'for　the　sake　of　which'　is　ambiguous；　it　may　mean　either　（a）　the　end　to　achieve　which；　or　（b）　the　being　in　whose　interest；　the　act　is　done。　Since　then　no　living　thing　is　able　to　partake　in　what　is　eternal　and　divine　by　uninterrupted　continuance　（for　nothing　perishable　can　for　ever　remain　one　and　the　same）；　it　tries　to　achieve　that　end　in　the　only　way　possible　to　it；　and　success　is　possible　in　varying　degrees；　so　it　remains　not　indeed　as　the　self…same　individual　but　continues　its　existence　in　something　like　itself…not　numerically　but　specifically　one。　　　The　soul　is　the　cause　or　source　of　the　living　body。　The　terms　cause　and　source　have　many　senses。　But　the　soul　is　the　cause　of　its　body　alike　in　all　three　senses　which　we　explicitly　recognize。　It　is　（a）　the　source　or　origin　of　movement；　it　is　（b）　the　end；　it　is　（c）　the　essence　of　the　whole　living　body。　　　That　it　is　the　last；　is　clear；　for　in　everything　the　essence　is　identical　with　the　ground　of　its　being；　and　here；　in　the　case　of　living　things；　their　being　is　to　live；　and　of　their　being　and　their　living　the　soul　in　them　is　the　cause　or　source。　Further；　the　actuality　of　whatever　is　potential　is　identical　with　its　formulable　essence。　　　It　is　manifest　that　the　soul　is　also　the　final　cause　of　its　body。　For　Nature；　like　mind；　always　does　whatever　it　does　for　the　sake　of　something；　which　something　is　its　end。　To　that　something　corresponds　in　the　case　of　animals　the　soul　and　in　this　it　follows　the　order　of　nature；　all　natural　bodies　are　organs　of　the　soul。　This　is　true　of　those　that　enter　into　the　constitution　of　plants　as　well　as　of　those　which　enter　into　that　of　animals。　This　shows　that　that　the　sake　of　which　they　are　is　soul。　We　must　here　recall　the　two　senses　of　'that　for　the　sake　of　which'；　viz。　（a）　the　end　to　achieve　which；　and　（b）　the　being　in　whose　interest；　anything　is　or　is　done。　　　We　must　maintain；　further；　that　the　soul　is　also　the　cause　of　the　living　body　as　the　original　source　of　local　movement。　The　power　of　locomotion　is　not　found；　however；　in　all　living　things。　But　change　of　quality　and　change　of　quantity　are　also　due　to　the　soul。　Sensation　is　held　to　be　a　qualitative　alteration；　and　nothing　except　what　has　soul　in　it　is　capable　of　sensation。　The　same　holds　of　the　quantitative　changes　which　constitute　growth　and　decay；　nothing　grows　or　decays　naturally　except　what　feeds　itself；　and　nothing　feeds　itself　except　what　has　a　share　of　soul　in　it。　　　Empedocles　is　wrong　in　adding　that　growth　in　plants　is　to　be　explained；　the　downward　rooting　by　the　natural　tendency　of　earth　to　travel　downwards；　and　the　upward　branching　by　the　similar　natural　tendency　of　fire　to　travel　upwards。　For　he　misinterprets　up　and　down；　up　and　down　are　not　for　all　things　what　they　are　for　the　whole　Cosmos：　if　we　are　to　distinguish　and　identify　organs　according　to　their　functions；　the　roots　of　plants　are　analogous　to　the　head　in　animals。　Further；　we　must　ask　what　is　the　force　that　holds　together　the　earth　and　the　fire　which　tend　to　travel　in　contrary　directions；　if　there　is　no　counteracting　force；　they　will　be　torn　asunder；　if　there　is；　this　must　be　the　soul　and　the　cause　of　nutrition　and　growth。　By　some　the　element　of　fire　is　held　to　be　the　cause　of　nutrition　and　growth；　for　it　alone　of　the　primary　bodies　or　elements　is　observed　to　feed　and　increase　itself。　Hence　the　suggestion　that　in　both　plants　and　animals　it　is　it　which　is　the　operative　force。　A　concurrent　cause　in　a　sense　it　certainly　is；　but　not　the　principal　cause；　that　is　rather　the　soul；　for　while　the　growth　of　fire　goes　on　without　limit　so　long　as　there　is　a　supply　of　fuel；　in　the　case　of　all　complex　wholes　formed　in　the　course　of　nature　there　is　a　limit　or　ratio　which　determines