prior analytics-第15部分

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necessary；　but　not　everything　which　is　necessary　is　a　syllogism。



Consequently；　though　something　results　when　certain　propositions　are



assumed；　we　must　not　try　to　reduce　it　directly；　but　must　first　state



the　two　premisses；　then　divide　them　into　their　terms。　We　must　take



that　term　as　middle　which　is　stated　in　both　the　remisses：　for　it　is



necessary　that　the　middle　should　be　found　in　both　premisses　in　all　the



figures。



　　If　then　the　middle　term　is　a　predicate　and　a　subject　of　predication；



or　if　it　is　a　predicate；　and　something　else　is　denied　of　it；　we



shall　have　the　first　figure：　if　it　both　is　a　predicate　and　is　denied



of　something；　the　middle　figure：　if　other　things　are　predicated　of　it；



or　one　is　denied；　the　other　predicated；　the　last　figure。　For　it　was



thus　that　we　found　the　middle　term　placed　in　each　figure。　It　is　placed



similarly　too　if　the　premisses　are　not　universal：　for　the　middle



term　is　determined　in　the　same　way。　Clearly　then；　if　the　same　term



is　not　stated　more　than　once　in　the　course　of　an　argument；　a　syllogism



cannot　be　made：　for　a　middle　term　has　not　been　taken。　Since　we　know



what　sort　of　thesis　is　established　in　each　figure；　and　in　which　the



universal；　in　what　sort　the　particular　is　described；　clearly　we　must



not　look　for　all　the　figures；　but　for　that　which　is　appropriate　to　the



thesis　in　hand。　If　the　thesis　is　established　in　more　figures　than　one；



we　shall　recognize　the　figure　by　the　position　of　the　middle　term。







　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　33







　　Men　are　frequently　deceived　about　syllogisms　because　the　inference



is　necessary；　as　has　been　said　above；　sometimes　they　are　deceived　by



the　similarity　in　the　positing　of　the　terms；　and　this　ought　not　to



escape　our　notice。　E。g。　if　A　is　stated　of　B；　and　B　of　C：　it　would　seem



that　a　syllogism　is　possible　since　the　terms　stand　thus：　but　nothing



necessary　results；　nor　does　a　syllogism。　Let　A　represent　the　term



'being　eternal'；　B　'Aristomenes　as　an　object　of　thought'；　C



'Aristomenes'。　It　is　true　then　that　A　belongs　to　B。　For　Aristomenes　as



an　object　of　thought　is　eternal。　But　B　also　belongs　to　C：　for



Aristomenes　is　Aristomenes　as　an　object　of　thought。　But　A　does　not



belong　to　C：　for　Aristomenes　is　perishable。　For　no　syllogism　was



made　although　the　terms　stood　thus：　that　required　that　the　premiss



AB　should　be　stated　universally。　But　this　is　false；　that　every



Aristomenes　who　is　an　object　of　thought　is　eternal；　since



Aristomenes　is　perishable。　Again　let　C　stand　for　'Miccalus'；　B　for



'musical　Miccalus'；　A　for　'perishing　to…morrow'。　It　is　true　to



predicate　B　of　C：　for　Miccalus　is　musical　Miccalus。　Also　A　can　be



predicated　of　B：　for　musical　Miccalus　might　perish　to…morrow。　But　to



state　A　of　C　is　false　at　any　rate。　This　argument　then　is　identical



with　the　former；　for　it　is　not　true　universally　that　musical



Miccalus　perishes　to…morrow：　but　unless　this　is　assumed；　no



syllogism　（as　we　have　shown）　is　possible。



　　This　deception　then　arises　through　ignoring　a　small　distinction。　For



if　we　accept　the　conclusion　as　though　it　made　no　difference　whether　we



said　'This　belong　to　that'　or　'This　belongs　to　all　of　that'。







　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　34







　　Men　will　frequently　fall　into　fallacies　through　not　setting　out



the　terms　of　the　premiss　well；　e。g。　suppose　A　to　be　health；　B　disease；



C　man。　It　is　true　to　say　that　A　cannot　belong　to　any　B　（for　health



belongs　to　no　disease）　and　again　that　B　belongs　to　every　C　（for



every　man　is　capable　of　disease）。　It　would　seem　to　follow　that



health　cannot　belong　to　any　man。　The　reason　for　this　is　that　the　terms



are　not　set　out　well　in　the　statement；　since　if　the　things　which　are



in　the　conditions　are　substituted；　no　syllogism　can　be　made；　e。g。　if



'healthy'　is　substituted　for　'health'　and　'diseased'　for　'disease'。



For　it　is　not　true　to　say　that　being　healthy　cannot　belong　to　one



who　is　diseased。　But　unless　this　is　assumed　no　conclusion　results；



save　in　respect　of　possibility：　but　such　a　conclusion　is　not



impossible：　for　it　is　possible　that　health　should　belong　to　no　man。



Again　the　fallacy　may　occur　in　a　similar　way　in　the　middle　figure：　'it



is　not　possible　that　health　should　belong　to　any　disease；　but　it　is



possible　that　health　should　belong　to　every　man；　consequently　it　is



not　possible　that　disease　should　belong　to　any　man'。　In　the　third



figure　the　fallacy　results　in　reference　to　possibility。　For　health　and



diseae　and　knowledge　and　ignorance；　and　in　general　contraries；　may



possibly　belong　to　the　same　thing；　but　cannot　belong　to　one　another。



This　is　not　in　agreement　with　what　was　said　before：　for　we　stated　that



when　several　things　could　belong　to　the　same　thing；　they　could



belong　to　one　another。



　　It　is　evident　then　that　in　all　these　cases　the　fallacy　arises　from



the　setting　out　of　the　terms：　for　if　the　things　that　are　in　the



conditions　are　substituted；　no　fallacy　arises。　It　is　clear　then　that



in　such　premisses　what　possesses　the　condition　ought　always　to　be



substituted　for　the　condition　and　taken　as　the　term。







　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　35







　　We　must　not　always　seek　to　set　out　the　terms　a　single　word：　for　we



shall　often　have　complexes　of　words　to　which　a　single　name　is　not



given。　Hence　it　is　difficult　to　reduce　syllogisms　with　such　terms。



Sometimes　too　fallacies　will　result　from　such　a　search；　e。g。　the



belief　that　syllogism　can　establish　that　which　has　no　mean。　Let　A



stand　for　two　right　angles；　B　for　triangle；　C　for　isosceles



triangle。　A　then　belongs　to　C　because　of　B：　but　A　belongs　to　B　without



the　mediation　of　another　term：　for　the　triangle　in　virtue　of　its　own



nature　contains　two　right　angles；　consequently　there　will　be　no　middle



term　for　the　proposition　AB；　although　it　is　demonstrable。　For　it　is



clear　that　the　middle　must　not　always　be　assumed　to　be　an　individual



thing；　but　sometimes　a　complex　of　words；　as　happens　in　the　case



mentioned。







　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　36







　　That　the　first　term　belongs　to　the　middle；　and　the　middle　to　the



extreme；　must　not　be　understood　in　the　sense　that　they　can　always　be



predicated　of　one　another　or　that　the　first　term　will　be　predicated　of



the　middle　in　the　same　way　as　the　middle　is　predicated　of　the　last



term。　The　same　holds　if　the　premisses　are　negative。　But　we　must



suppose　the　verb　'to　belong'　to　have　as　many　meanings　as　the　senses　in



which　the　verb　'to　be'　is　used；　and　in　which　the　assertion　that　a



thing　'is'　may　be　said　to　be　true。　Take　for　example　the　statement　that



there　is　a　single　science　of　contraries。　Let　A　stand　for　'there



being　a　single　science'；　and　B　for　things　which　are　contrary　to　one



another。　Then　A　belongs　to　B；　not　in　the　sense　that　contraries　are　the



fact　of　there　being　a　single　science　of　them；　but　in　the　sense　that　it



is　true　to　say　of　the　contraries　that　there　is　a　single　science　of



them。



　　It　happens　sometimes　that　the　first　term　is　stated　of　the　middle；



but　the　middle　is　not　stated　of　the　third　term；　e。g。　if　wisdom　is



knowledge；　and　wisdom　is　of　the　good；　the　conclusion　is　that　there



is　knowledge　of　the　good。　The　good　then　is　not　knowledge；　though



wisdom　is　knowledge。　Sometimes　the　middle　term　is　stated　of　the　third；



but　the　first　is　not　stated　of　the　middle；　e。g。　if　there　is　a



science　of　everything　that　has　a　quality；　or　is　a　contrary；　and　the



good　both　is　a　contrary　and　has　a　quality；　the　conclusion　is　that



there　is　a　science　of　the　good；　but　the　good　is　not　science；　nor　is



that　which　has　a　quality　or　is　a　contrary；　though　the　good　is　both



of　these。　Sometimes　neither　the　first　term　is　stated　of　the　middle；



nor　the　middle　of　the　third；　while　the　first　is　sometimes　stated　of



the　third；　and　sometimes　not：　e。g。　if　there　is　a　genus　of　that　of



which　there　is　a　science；　and　if　there　is　a　science　of　the　good；　we



conclude　that　there　is　a　genus　of　the　good。　But　nothing　is



predicated　of　anything。　And　if　that　of　which　there　is　a　science　is　a



genus；　and　if　there　is　a　science　of　the　good；　we　conclude　that　the



good　is　a　genus。　The　first　term　then　is　predicated　of　the　extreme；　but



in　the　premisses　one　thing　is　not　stated　of　another。



　　The　same　holds　good　where　the　relation　is　negative。　For　'that　does



not　belong　to　this'　does　not　always　mean　that　'this　is　not　that'；



but　sometimes　that　'this　is　not　of　that'　or　'for　that'；　e。g。　'there　is



not　a　motion　of　a　motion　or　a　becoming　of　a　becoming；　but　there　is　a



becoming　of　pleasure：　so　pleasure　is　not　a　becoming。'　Or　again　it



may　be　said　that　there　is　a　sign　of　laughter；　but　there　is　not　a



sign　of　a　sign；　consequently　laughter　is　not　a　sign。　This　holds　in　the



other　cases　too；　in　which　the　thesis　is　refuted　because　the　genus　is



asserted　in　a　particular　way；　in　relation　to　the　terms　of　the



thesis。　Again　take　the　inference　'opportunity　is　not　the　right　time：



for　opportunity　belongs　to　God；　but　the　right　time　does　not；　since



nothing　is　useful　to　God'。　We　must　take　as　terms　opportunity…right



time…God：　but　the　premiss　must　be　understood　according　to　the　case



of　the　noun。　For　we　state　this　universally　without　qualification；　that



the　terms　ought　always　to　be　stated　in　the　nominative；　e。g。　man；　good；



contraries；　not　in　oblique　cases；　e。g。　of　man；　of　a　good；　of



contraries；　but　the　premisses　ought　to　be　understood　with　reference　to



the　cases　of　each　term…either　the　dative；　e。g。　'equal　to　this'；　or　the



genitive；　e。g。　'double　of　this'；　or　the　ac