posterior analytics- 第20部分

not　further　divisible…i。e。　that　as　soon　as　we　have　taken　the　last



differentia　to　form　the　concrete　totality；　this　totality　admits　of



no　division　into　species。　For　it　is　clear　that　there　is　no　superfluous



addition；　since　all　these　terms　we　have　selected　are　elements　in　the



definable　form；　and　nothing　lacking；　since　any　omission　would　have



to　be　a　genus　or　a　differentia。　Now　the　primary　term　is　a　genus；　and



this　term　taken　in　conjunction　with　its　differentiae　is　a　genus：



moreover　the　differentiae　are　all　included；　because　there　is　now　no



further　differentia；　if　there　were；　the　final　concrete　would　admit



of　division　into　species；　which；　we　said；　is　not　the　case。



　　To　resume　our　account　of　the　right　method　of　investigation：　We



must　start　by　observing　a　set　of　similar…i。e。　specifically



identical…individuals；　and　consider　what　element　they　have　in



common。　We　must　then　apply　the　same　process　to　another　set　of



individuals　which　belong　to　one　species　and　are　generically　but　not



specifically　identical　with　the　former　set。　When　we　have　established



what　the　common　element　is　in　all　members　of　this　second　species；



and　likewise　in　members　of　further　species；　we　should　again　consider



whether　the　results　established　possess　any　identity；　and　persevere



until　we　reach　a　single　formula；　since　this　will　be　the　definition



of　the　thing。　But　if　we　reach　not　one　formula　but　two　or　more；



evidently　the　definiendum　cannot　be　one　thing　but　must　be　more　than



one。　I　may　illustrate　my　meaning　as　follows。　If　we　were　inquiring　what



the　essential　nature　of　pride　is；　we　should　examine　instances　of　proud



men　we　know　of　to　see　what；　as　such；　they　have　in　common；　e。g。　if



Alcibiades　was　proud；　or　Achilles　and　Ajax　were　proud；　we　should



find　on　inquiring　what　they　all　had　in　common；　that　it　was　intolerance



of　insult；　it　was　this　which　drove　Alcibiades　to　war；　Achilles



wrath；　and　Ajax　to　suicide。　We　should　next　examine　other　cases；



Lysander；　for　example；　or　Socrates；　and　then　if　these　have　in　common



indifference　alike　to　good　and　ill　fortune；　I　take　these　two　results



and　inquire　what　common　element　have　equanimity　amid　the



vicissitudes　of　life　and　impatience　of　dishonour。　If　they　have　none；



there　will　be　two　genera　of　pride。　Besides；　every　definition　is　always



universal　and　commensurate：　the　physician　does　not　prescribe　what　is



healthy　for　a　single　eye；　but　for　all　eyes　or　for　a　determinate



species　of　eye。　It　is　also　easier　by　this　method　to　define　the



single　species　than　the　universal；　and　that　is　why　our　procedure



should　be　from　the　several　species　to　the　universal　genera…this　for



the　further　reason　too　that　equivocation　is　less　readily　detected　in



genera　than　in　infimae　species。　Indeed；　perspicuity　is　essential　in



definitions；　just　as　inferential　movement　is　the　minimum　required　in



demonstrations；　and　we　shall　attain　perspicuity　if　we　can　collect



separately　the　definition　of　each　species　through　the　group　of



singulars　which　we　have　established　e。g。　the　definition　of



similarity　not　unqualified　but　restricted　to　colours　and　to　figures；



the　definition　of　acuteness；　but　only　of　sound…and　so　proceed　to　the



common　universal　with　a　careful　avoidance　of　equivocation。　We　may



add　that　if　dialectical　disputation　must　not　employ　metaphors；　clearly



metaphors　and　metaphorical　expressions　are　precluded　in　definition：



otherwise　dialectic　would　involve　metaphors。







　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　14







　　In　order　to　formulate　the　connexions　we　wish　to　prove　we　have　to



select　our　analyses　and　divisions。　The　method　of　selection　consists　in



laying　down　the　common　genus　of　all　our　subjects　of　investigation…if



e。g。　they　are　animals；　we　lay　down　what　the　properties　are　which



inhere　in　every　animal。　These　established；　we　next　lay　down　the



properties　essentially　connected　with　the　first　of　the　remaining



classes…e。g。　if　this　first　subgenus　is　bird；　the　essential



properties　of　every　bird…and　so　on；　always　characterizing　the



proximate　subgenus。　This　will　clearly　at　once　enable　us　to　say　in



virtue　of　what　character　the　subgenera…man；　e。g。　or　horse…possess



their　properties。　Let　A　be　animal；　B　the　properties　of　every　animal；　C



D　E　various　species　of　animal。　Then　it　is　clear　in　virtue　of　what



character　B　inheres　in　D…namely　A…and　that　it　inheres　in　C　and　E　for



the　same　reason：　and　throughout　the　remaining　subgenera　always　the



same　rule　applies。



　　We　are　now　taking　our　examples　from　the　traditional　class…names；　but



we　must　not　confine　ourselves　to　considering　these。　We　must　collect



any　other　common　character　which　we　observe；　and　then　consider　with



what　species　it　is　connected　and　what。properties　belong　to　it。　For



example；　as　the　common　properties　of　horned　animals　we　collect　the



possession　of　a　third　stomach　and　only　one　row　of　teeth。　Then　since　it



is　clear　in　virtue　of　what　character　they　possess　these



attributes…namely　their　horned　character…the　next　question　is；　to　what



species　does　the　possession　of　horns　attach？



　　Yet　a　further　method　of　selection　is　by　analogy：　for　we　cannot



find　a　single　identical　name　to　give　to　a　squid's　pounce；　a　fish's



spine；　and　an　animal's　bone；　although　these　too　possess　common



properties　as　if　there　were　a　single　osseous　nature。







　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　15







　　Some　connexions　that　require　proof　are　identical　in　that　they



possess　an　identical　'middle'　e。g。　a　whole　group　might　be　proved



through　'reciprocal　replacement'…and　of　these　one　class　are



identical　in　genus；　namely　all　those　whose　difference　consists　in



their　concerning　different　subjects　or　in　their　mode　of　manifestation。



This　latter　class　may　be　exemplified　by　the　questions　as　to　the　causes



respectively　of　echo；　of　reflection；　and　of　the　rainbow：　the



connexions　to　be　proved　which　these　questions　embody　are　identical



generically；　because　all　three　are　forms　of　repercussion；　but



specifically　they　are　different。



　　Other　connexions　that　require　proof　only　differ　in　that　the　'middle'



of　the　one　is　subordinate　to　the　'middle'　of　the　other。　For　example：



Why　does　the　Nile　rise　towards　the　end　of　the　month？　Because　towards



its　close　the　month　is　more　stormy。　Why　is　the　month　more　stormy



towards　its　close？　Because　the　moon　is　waning。　Here　the　one　cause　is



subordinate　to　the　other。







　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　16







　　The　question　might　be　raised　with　regard　to　cause　and　effect　whether



when　the　effect　is　present　the　cause　also　is　present；　whether；　for



instance；　if　a　plant　sheds　its　leaves　or　the　moon　is　eclipsed；　there



is　present　also　the　cause　of　the　eclipse　or　of　the　fall　of　the



leaves…the　possession　of　broad　leaves；　let　us　say；　in　the　latter　case；



in　the　former　the　earth's　interposition。　For；　one　might　argue；　if　this



cause　is　not　present；　these　phenomena　will　have　some　other　cause：　if



it　is　present；　its　effect　will　be　at　once　implied　by　it…the　eclipse　by



the　earth's　interposition；　the　fall　of　the　leaves　by　the　possession　of



broad　leaves；　but　if　so；　they　will　be　logically　coincident　and　each



capable　of　proof　through　the　other。　Let　me　illustrate：　Let　A　be



deciduous　character；　B　the　possession　of　broad　leaves；　C　vine。　Now



if　A　inheres　in　B　（for　every　broad…leaved　plant　is　deciduous）；　and　B



in　C　（every　vine　possessing　broad　leaves）；　then　A　inheres　in　C



（every　vine　is　deciduous）；　and　the　middle　term　B　is　the　cause。　But



we　can　also　demonstrate　that　the　vine　has　broad　leaves　because　it　is



deciduous。　Thus；　let　D　be　broad…leaved；　E　deciduous；　F　vine。　Then　E



inheres　in　F　（since　every　vine　is　deciduous）；　and　D　in　E　（for　every



deciduous　plant　has　broad　leaves）：　therefore　every　vine　has　broad



leaves；　and　the　cause　is　its　deciduous　character。　If；　however；　they



cannot　each　be　the　cause　of　the　other　（for　cause　is　prior　to　effect；



and　the　earth's　interposition　is　the　cause　of　the　moon's　eclipse　and



not　the　eclipse　of　the　interposition）…if；　then；　demonstration



through　the　cause　is　of　the　reasoned　fact　and　demonstration　not



through　the　cause　is　of　the　bare　fact；　one　who　knows　it　through　the



eclipse　knows　the　fact　of　the　earth's　interposition　but　not　the



reasoned　fact。　Moreover；　that　the　eclipse　is　not　the　cause　of　the



interposition；　but　the　interposition　of　the　eclipse；　is　obvious



because　the　interposition　is　an　element　in　the　definition　of



eclipse；　which　shows　that　the　eclipse　is　known　through　the



interposition　and　not　vice　versa。



　　On　the　other　hand；　can　a　single　effect　have　more　than　one　cause？　One



might　argue　as　follows：　if　the　same　attribute　is　predicable　of　more



than　one　thing　as　its　primary　subject；　let　B　be　a　primary　subject　in



which　A　inheres；　and　C　another　primary　subject　of　A；　and　D　and　E



primary　subjects　of　B　and　C　respectively。　A　will　then　inhere　in　D



and　E；　and　B　will　be　the　cause　of　A's　inherence　in　D；　C　of　A's



inherence　in　E。　The　presence　of　the　cause　thus　necessitates　that　of



the　effect；　but　the　presence　of　the　effect　necessitates　the　presence



not　of　all　that　may　cause　it　but　only　of　a　cause　which　yet　need　not　be



the　whole　cause。　We　may；　however；　suggest　that　if　the　connexion　to



be　proved　is　always　universal　and　commensurate；　not　only　will　the



cause　be　a　whole　but　also　the　effect　will　be　universal　and



commensurate。　For　instance；　deciduous　character　will　belong



exclusively　to　a　subject　which　is　a　whole；　and；　if　this　whole　has



species；　universally　and　commensurately　to　those　species…i。e。　either