prior analytics-第14节

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For　some　things　are　peculiar　to　the　species　as　distinct　from　the



genus；　for　species　being　distinct　there　must　be　attributes　peculiar　to



each。　Nor　must　we　take　as　things　which　the　superior　term　follows；



those　things　which　the　inferior　term　follows；　e。g。　take　as　subjects　of



the　predicate　'animal'　what　are　really　subjects　of　the　predicate



'man'。　It　is　necessary　indeed；　if　animal　follows　man；　that　it　should



follow　all　these　also。　But　these　belong　more　properly　to　the　choice　of



what　concerns　man。　One　must　apprehend　also　normal　consequents　and



normal　antecedents…；　for　propositions　which　obtain　normally　are



established　syllogistically　from　premisses　which　obtain　normally；　some



if　not　all　of　them　having　this　character　of　normality。　For　the



conclusion　of　each　syllogism　resembles　its　principles。　We　must　not



however　choose　attributes　which　are　consequent　upon　all　the　terms：　for



no　syllogism　can　be　made　out　of　such　premisses。　The　reason　why　this　is



so　will　be　clear　in　the　sequel。







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　　If　men　wish　to　establish　something　about　some　whole；　they　must



look　to　the　subjects　of　that　which　is　being　established　（the



subjects　of　which　it　happens　to　be　asserted）；　and　the　attributes　which



follow　that　of　which　it　is　to　be　predicated。　For　if　any　of　these



subjects　is　the　same　as　any　of　these　attributes；　the　attribute



originally　in　question　must　belong　to　the　subject　originally　in



question。　But　if　the　purpose　is　to　establish　not　a　universal　but　a



particular　proposition；　they　must　look　for　the　terms　of　which　the



terms　in　question　are　predicable：　for　if　any　of　these　are　identical；



the　attribute　in　question　must　belong　to　some　of　the　subject　in



question。　Whenever　the　one　term　has　to　belong　to　none　of　the　other；



one　must　look　to　the　consequents　of　the　subject；　and　to　those



attributes　which　cannot　possibly　be　present　in　the　predicate　in



question：　or　conversely　to　the　attributes　which　cannot　possibly　be



present　in　the　subject；　and　to　the　consequents　of　the　predicate。　If



any　members　of　these　groups　are　identical；　one　of　the　terms　in



question　cannot　possibly　belong　to　any　of　the　other。　For　sometimes　a



syllogism　in　the　first　figure　results；　sometimes　a　syllogism　in　the



second。　But　if　the　object　is　to　establish　a　particular　negative



proposition；　we　must　find　antecedents　of　the　subject　in　question　and



attributes　which　cannot　possibly　belong　to　the　predicate　in



question。　If　any　members　of　these　two　groups　are　identical；　it　follows



that　one　of　the　terms　in　question　does　not　belong　to　some　of　the



other。　Perhaps　each　of　these　statements　will　become　clearer　in　the



following　way。　Suppose　the　consequents　of　A　are　designated　by　B；　the



antecedents　of　A　by　C；　attributes　which　cannot　possibly　belong　to　A　by



D。　Suppose　again　that　the　attributes　of　E　are　designated　by　F；　the



antecedents　of　E　by　G；　and　attributes　which　cannot　belong　to　E　by　H。



If　then　one　of　the　Cs　should　be　identical　with　one　of　the　Fs；　A　must



belong　to　all　E：　for　F　belongs　to　all　E；　and　A　to　all　C；



consequently　A　belongs　to　all　E。　If　C　and　G　are　identical；　A　must



belong　to　some　of　the　Es：　for　A　follows　C；　and　E　follows　all　G。　If　F



and　D　are　identical；　A　will　belong　to　none　of　the　Es　by　a



prosyllogism：　for　since　the　negative　proposition　is　convertible；　and　F



is　identical　with　D；　A　will　belong　to　none　of　the　Fs；　but　F　belongs　to



all　E。　Again；　if　B　and　H　are　identical；　A　will　belong　to　none　of　the



Es：　for　B　will　belong　to　all　A；　but　to　no　E：　for　it　was　assumed　to



be　identical　with　H；　and　H　belonged　to　none　of　the　Es。　If　D　and　G



are　identical；　A　will　not　belong　to　some　of　the　Es：　for　it　will　not



belong　to　G；　because　it　does　not　belong　to　D：　but　G　falls　under　E：



consequently　A　will　not　belong　to　some　of　the　Es。　If　B　is　identical



with　G；　there　will　be　a　converted　syllogism：　for　E　will　belong　to



all　A　since　B　belongs　to　A　and　E　to　B　（for　B　was　found　to　be　identical



with　G）：　but　that　A　should　belong　to　all　E　is　not　necessary；　but　it



must　belong　to　some　E　because　it　is　possible　to　convert　the



universal　statement　into　a　particular。



　　It　is　clear　then　that　in　every　proposition　which　requires　proof　we



must　look　to　the　aforesaid　relations　of　the　subject　and　predicate　in



question：　for　all　syllogisms　proceed　through　these。　But　if　we　are



seeking　consequents　and　antecedents　we　must　look　for　those　which　are



primary　and　most　universal；　e。g。　in　reference　to　E　we　must　look　to



KF　rather　than　to　F　alone；　and　in　reference　to　A　we　must　look　to　KC



rather　than　to　C　alone。　For　if　A　belongs　to　KF；　it　belongs　both　to　F



and　to　E：　but　if　it　does　not　follow　KF；　it　may　yet　follow　F。　Similarly



we　must　consider　the　antecedents　of　A　itself：　for　if　a　term　follows



the　primary　antecedents；　it　will　follow　those　also　which　are



subordinate；　but　if　it　does　not　follow　the　former；　it　may　yet　follow



the　latter。



　　It　is　clear　too　that　the　inquiry　proceeds　through　the　three　terms



and　the　two　premisses；　and　that　all　the　syllogisms　proceed　through　the



aforesaid　figures。　For　it　is　proved　that　A　belongs　to　all　E；



whenever　an　identical　term　is　found　among　the　Cs　and　Fs。　This　will



be　the　middle　term；　A　and　E　will　be　the　extremes。　So　the　first



figure　is　formed。　And　A　will　belong　to　some　E；　whenever　C　and　G　are



apprehended　to　be　the　same。　This　is　the　last　figure：　for　G　becomes　the



middle　term。　And　A　will　belong　to　no　E；　when　D　and　F　are　identical。



Thus　we　have　both　the　first　figure　and　the　middle　figure；　the　first；



because　A　belongs　to　no　F；　since　the　negative　statement　is



convertible；　and　F　belongs　to　all　E：　the　middle　figure　because　D



belongs　to　no　A；　and　to　all　E。　And　A　will　not　belong　to　some　E；



whenever　D　and　G　are　identical。　This　is　the　last　figure：　for　A　will



belong　to　no　G；　and　E　will　belong　to　all　G。　Clearly　then　all



syllogisms　proceed　through　the　aforesaid　figures；　and　we　must　not



select　consequents　of　all　the　terms；　because　no　syllogism　is



produced　from　them。　For　（as　we　saw）　it　is　not　possible　at　all　to



establish　a　proposition　from　consequents；　and　it　is　not　possible　to



refute　by　means　of　a　consequent　of　both　the　terms　in　question：　for　the



middle　term　must　belong　to　the　one；　and　not　belong　to　the　other。



　　It　is　clear　too　that　other　methods　of　inquiry　by　selection　of　middle



terms　are　useless　to　produce　a　syllogism；　e。g。　if　the　consequents　of



the　terms　in　question　are　identical；　or　if　the　antecedents　of　A　are



identical　with　those　attributes　which　cannot　possibly　belong　to　E；



or　if　those　attributes　are　identical　which　cannot　belong　to　either



term：　for　no　syllogism　is　produced　by　means　of　these。　For　if　the



consequents　are　identical；　e。g。　B　and　F；　we　have　the　middle　figure



with　both　premisses　affirmative：　if　the　antecedents　of　A　are　identical



with　attributes　which　cannot　belong　to　E；　e。g。　C　with　H；　we　have　the



first　figure　with　its　minor　premiss　negative。　If　attributes　which



cannot　belong　to　either　term　are　identical；　e。g。　C　and　H；　both



premisses　are　negative；　either　in　the　first　or　in　the　middle　figure。



But　no　syllogism　is　possible　in　this　way。



　　It　is　evident　too　that　we　must　find　out　which　terms　in　this



inquiry　are　identical；　not　which　are　different　or　contrary；　first



because　the　object　of　our　investigation　is　the　middle　term；　and　the



middle　term　must　be　not　diverse　but　identical。　Secondly；　wherever　it



happens　that　a　syllogism　results　from　taking　contraries　or　terms　which



cannot　belong　to　the　same　thing；　all　arguments　can　be　reduced　to　the



aforesaid　moods；　e。g。　if　B　and　F　are　contraries　or　cannot　belong　to



the　same　thing。　For　if　these　are　taken；　a　syllogism　will　be　formed



to　prove　that　A　belongs　to　none　of　the　Es；　not　however　from　the



premisses　taken　but　in　the　aforesaid　mood。　For　B　will　belong　to　all



A　and　to　no　E。　Consequently　B　must　be　identical　with　one　of　the　Hs。



Again；　if　B　and　G　cannot　belong　to　the　same　thing；　it　follows　that　A



will　not　belong　to　some　of　the　Es：　for　then　too　we　shall　have　the



middle　figure：　for　B　will　belong　to　all　A　and　to　no　G。　Consequently



B　must　be　identical　with　some　of　the　Hs。　For　the　fact　that　B　and　G



cannot　belong　to　the　same　thing　differs　in　no　way　from　the　fact　that　B



is　identical　with　some　of　the　Hs：　for　that　includes　everything　which



cannot　belong　to　E。



　　It　is　clear　then　that　from　the　inquiries　taken　by　themselves　no



syllogism　results；　but　if　B　and　F　are　contraries　B　must　be　identical



with　one　of　the　Hs；　and　the　syllogism　results　through　these　terms。



It　turns　out　then　that　those　who　inquire　in　this　ma