ON　THE　SOUL
  by　Aristotle
  translated　by　J。　A。　Smith
  Book　I
  1
  HOLDING　as　we　do　that；　while　knowledge　of　any　kind　is　a　thing　to　be　honoured　and　prized；　one　kind　of　it　may；　either　by　reason　of　its　greater　exactness　or　of　a　higher　dignity　and　greater　wonderfulness　in　its　objects；　be　more　honourable　and　precious　than　another；　on　both　accounts　we　should　naturally　be　led　to　place　in　the　front　rank　the　study　of　the　soul。　The　knowledge　of　the　soul　admittedly　contributes　greatly　to　the　advance　of　truth　in　general；　and；　above　all；　to　our　understanding　of　Nature；　for　the　soul　is　in　some　sense　the　principle　of　animal　life。　Our　aim　is　to　grasp　and　understand；　first　its　essential　nature；　and　secondly　its　properties；　of　these　some　are　taught　to　be　affections　proper　to　the　soul　itself；　while　others　are　considered　to　attach　to　the　animal　owing　to　the　presence　within　it　of　soul。　　　To　attain　any　assured　knowledge　about　the　soul　is　one　of　the　most　difficult　things　in　the　world。　As　the　form　of　question　which　here　presents　itself；　viz。　the　question　'What　is　it？'；　recurs　in　other　fields；　it　might　be　supposed　that　there　was　some　single　method　of　inquiry　applicable　to　all　objects　whose　essential　nature　（as　we　are　endeavouring　to　ascertain　there　is　for　derived　properties　the　single　method　of　demonstration）；　in　that　case　what　we　should　have　to　seek　for　would　be　this　unique　method。　But　if　there　is　no　such　single　and　general　method　for　solving　the　question　of　essence；　our　task　becomes　still　more　difficult；　in　the　case　of　each　different　subject　we　shall　have　to　determine　the　appropriate　process　of　investigation。　If　to　this　there　be　a　clear　answer；　e。g。　that　the　process　is　demonstration　or　division；　or　some　known　method；　difficulties　and　hesitations　still　beset　us…with　what　facts　shall　we　begin　the　inquiry？　For　the　facts　which　form　the　starting…points　in　different　subjects　must　be　different；　as　e。g。　in　the　case　of　numbers　and　surfaces。　　　First；　no　doubt；　it　is　necessary　to　determine　in　which　of　the　summa　genera　soul　lies；　what　it　is；　is　it　'a　this…somewhat；　'a　substance；　or　is　it　a　quale　or　a　quantum；　or　some　other　of　the　remaining　kinds　of　predicates　which　we　have　distinguished？　Further；　does　soul　belong　to　the　class　of　potential　existents；　or　is　it　not　rather　an　actuality？　Our　answer　to　this　question　is　of　the　greatest　importance。　　　We　must　consider　also　whether　soul　is　divisible　or　is　without　parts；　and　whether　it　is　everywhere　homogeneous　or　not；　and　if　not　homogeneous；　whether　its　various　forms　are　different　specifically　or　generically：　up　to　the　present　time　those　who　have　discussed　and　investigated　soul　seem　to　have　confined　themselves　to　the　human　soul。　We　must　be　careful　not　to　ignore　the　question　whether　soul　can　be　defined　in　a　single　unambiguous　formula；　as　is　the　case　with　animal；　or　whether　we　must　not　give　a　separate　formula　for　each　of　it；　as　we　do　for　horse；　dog；　man；　god　（in　the　latter　case　the　'universal'　animal…and　so　too　every　other　'common　predicate'…being　treated　either　as　nothing　at　all　or　as　a　later　product）。　Further；　if　what　exists　is　not　a　plurality　of　souls；　but　a　plurality　of　parts　of　one　soul；　which　ought　we　to　investigate　first；　the　whole　soul　or　its　parts？　（It　is　also　a　difficult　problem　to　decide　which　of　these　parts　are　in　nature　distinct　from　one　another。）　Again；　which　ought　we　to　investigate　first；　these　parts　or　their　functions；　mind　or　thinking；　the　faculty　or　the　act　of　sensation；　and　so　on？　If　the　investigation　of　the　functions　precedes　that　of　the　parts；　the　further　question　suggests　itself：　ought　we　not　before　either　to　consider　the　correlative　objects；　e。g。　of　sense　or　thought？　It　seems　not　only　useful　for　the　discovery　of　the　causes　of　the　derived　properties　of　substances　to　be　acquainted　with　the　essential　nature　of　those　substances　（as　in　mathematics　it　is　useful　for　the　understanding　of　the　property　of　the　equality　of　the　interior　angles　of　a　triangle　to　two　right　angles　to　know　the　essential　nature　of　the　straight　and　the　curved　or　of　the　line　and　the　plane）　but　also　conversely；　for　the　knowledge　of　the　essential　nature　of　a　substance　is　largely　promoted　by　an　acquaintance　with　its　properties：　for；　when　we　are　able　to　give　an　account　conformable　to　experience　of　all　or　most　of　the　properties　of　a　substance；　we　shall　be　in　the　most　favourable　position　to　say　something　worth　saying　about　the　essential　nature　of　that　subject；　in　all　demonstration　a　definition　of　the　essence　is　required　as　a　starting…point；　so　that　definitions　which　do　not　enable　us　to　discover　the　derived　properties；　or　which　fail　to　facilitate　even　a　conjecture　about　them；　must　obviously；　one　and　all；　be　dialectical　and　futile。　　　A　further　problem　presented　by　the　affections　of　soul　is　this：　are　they　all　affections　of　the　complex　of　body　and　soul；　or　is　there　any　one　among　them　peculiar　to　the　soul　by　itself？　To　determine　this　is　indispensable　but　difficult。　If　we　consider　the　majority　of　them；　there　seems　to　be　no　case　in　which　the　soul　can　act　or　be　acted　upon　without　involving　the　body；　e。g。　anger；　courage；　appetite；　and　sensation　generally。　Thinking　seems　the　most　probable　exception；　but　if　this　too　proves　to　be　a　form　of　imagination　or　to　be　impossible　without　imagination；　it　too　requires　a　body　as　a　condition　of　its　existence。　If　there　is　any　way　of　acting　or　being　acted　upon　proper　to　soul；　soul　will　be　capable　of　separate　existence；　if　there　is　none；　its　separate　existence　is　impossible。　In　the　latter　case；　it　will　be　like　what　is　straight；　which　has　many　properties　arising　from　the　straightness　in　it；　e。g。　that　of　touching　a　bronze　sphere　at　a　point；　though　straightness　divorced　from　the　other　constituents　of　the　straight　thing　cannot　touch　it　in　this　way；　it　cannot　be　so　divorced　at　all；　since　it　is　always　found　in　a　body。　It　therefore　seems　that　all　the　affections　of　soul　involve　a　body…passion；　gentleness；　fear；　pity；　courage；　joy；　loving；　and　hating；　in　all　these　there　is　a　concurrent　affection　of　the　body。　In　support　of　this　we　may　point　to　the　fact　that；　while　sometimes　on　the　occasion　of　violent　and　striking　occurrences　there　is　no　excitement　or　fear　felt；　on　others　faint　and　feeble　stimulations　produce　these　emotions；　viz。　when　the　body　is　already　in　a　state　of　tension　resembling　its　condition　when　we　are　angry。　Here　is　a　still　clearer　case：　in　the　absence　of　any　external　cause　of　terror　we　find　ourselves　experiencing　the　feelings　of　a　man　in　terror。　From　all　this　it　is　obvious　that　the　affections　of　soul　are　enmattered　formulable　essences。　　　Consequently　their　definitions　ought　to　correspond；　e。g。　anger　should　be　defined　as　a　certain　mode　of　movement　of　such　and　such　a　body　（or　part　or　faculty　of　a　body）　by　this　or　that　cause　and　for　this　or　that　end。　That　is　precisely　why　the　study　of　the　soul　must　fall　within　the　science　of　Nature；　at　least　so　far　as　in　its　affections　it　manifests　this　double　character。　Hence　a　physicist　would　define　an　affection　of　soul　differently　from　a　dialectician；　the　latter　would　define　e。g。　anger　as　the　appetite　for　returning　pain　for　pain；　or　something　like　that；　while　the　former　would　define　it　as　a　boiling　of　the　blood　or　warm　substance　surround　the　heart。　The　latter　assigns　the　material　conditions；　the　former　the　form　or　formulable　essence；　for　what　he　states　is　the　formulable　essence　of　the　fact；　though　for　its　actual　existence　there　must　be　embodiment　of　it　in　a　material　such　as　is　described　by　the　other。　Thus　the　essence　of　a　house　is　assigned　in　such　a　formula　as　'a　shelter　against　destruction　by　wind；　rain；　and　heat'；　the　physicist　would　describe　it　as　'stones；　bricks；　and　timbers'；　but　there　is　a　third　possible　description　which　would　say　that　it　was　that　form　in　that　material　with　that　purpose　or　end。　Which；　then；　among　these　is　entitled　to　be　regarded　as　the　genuine　physicist？　The　one　who　confines　himself　to　the　material；　or　the　one　who　restricts　himself　to　the　formulable　essence　alone？　Is　it　not　rather　the　one　who　combines　both　in　a　single　formula？　If　this　is　so；　how　are　we　to　characterize　the　other　two？　Must　we　not　say　that　there　is　no　type　of　thinker　who　concerns　himself　with　those　qualities　or　attributes　of　the　material　which　are　in　fact　inseparable　from　the　material；　and　without　attempting　even　in　thought　to　separate　them？　The　physicist　is　he　who　concerns　himself　with　all　the　properties　active　and　passive　of　bodies　or　materials　thus　or　thus　defined；　attributes　not　considered　as　being　of　this　character　he　leaves　to　others；　in　certain　cases　it　may　be　to　a　specialist；　e。g。　a　carpenter　or　a　physician；　in　others　（a）　where　they　are　inseparable　in　fact；　but　are　separable　from　any　particular　kind　of　body　by　an　effort　of　abstraction；　to　the　mathematician；　（b）　where　they　are　separate　both　in　fact　and　in　thought　from　body　altogether；　to　the　First　Philosopher　or　metaphysician。　But　we　must　return　from　this　digression；　and　repeat　that　the　affections　of　soul　are　inseparable　from　the　material　substratum　of　animal　life；　to　which　we　have　seen　that　such　affections；　e。g。　passion　and　fear；　attach；　and　have　not　the　same　mode　of　being　as　a　line　or　a　plane。