their　attributes。
  Again；　it　is　not　true　that　the　basic　truths　are　much　fewer　than
  the　conclusions；　for　the　basic　truths　are　the　premisses；　and　the
  premisses　are　formed　by　the　apposition　of　a　fresh　extreme　term　or
  the　interposition　of　a　fresh　middle。　Moreover；　the　number　of
  conclusions　is　indefinite；　though　the　number　of　middle　terms　is
  finite；　and　lastly　some　of　the　basic　truths　are　necessary；　others
  variable。
  Looking　at　it　in　this　way　we　see　that；　since　the　number　of
  conclusions　is　indefinite；　the　basic　truths　cannot　be　identical　or
  limited　in　number。　If；　on　the　other　hand；　identity　is　used　in
  another　sense；　and　it　is　said；　e。g。　'these　and　no　other　are　the
  fundamental　truths　of　geometry；　these　the　fundamentals　of　calculation；
  these　again　of　medicine'；　would　the　statement　mean　anything　except
  that　the　sciences　have　basic　truths？　To　call　them　identical　because
  they　are　self…identical　is　absurd；　since　everything　can　be
  identified　with　everything　in　that　sense　of　identity。　Nor　again　can
  the　contention　that　all　conclusions　have　the　same　basic　truths　mean
  that　from　the　mass　of　all　possible　premisses　any　conclusion　may　be
  drawn。　That　would　be　exceedingly　naive；　for　it　is　not　the　case　in
  the　clearly　evident　mathematical　sciences；　nor　is　it　possible　in
  analysis；　since　it　is　the　immediate　premisses　which　are　the　basic
  truths；　and　a　fresh　conclusion　is　only　formed　by　the　addition　of　a　new
  immediate　premiss：　but　if　it　be　admitted　that　it　is　these　primary
  immediate　premisses　which　are　basic　truths；　each　subject…genus　will
  provide　one　basic　truth。　If；　however；　it　is　not　argued　that　from　the
  mass　of　all　possible　premisses　any　conclusion　may　be　proved；　nor　yet
  admitted　that　basic　truths　differ　so　as　to　be　generically　different
  for　each　science；　it　remains　to　consider　the　possibility　that；　while
  the　basic　truths　of　all　knowledge　are　within　one　genus；　special
  premisses　are　required　to　prove　special　conclusions。　But　that　this
  cannot　be　the　case　has　been　shown　by　our　proof　that　the　basic　truths
  of　things　generically　different　themselves　differ　generically。　For
  fundamental　truths　are　of　two　kinds；　those　which　are　premisses　of
  demonstration　and　the　subject…genus；　and　though　the　former　are　common；
  the　latter…number；　for　instance；　and　magnitude…are　peculiar。
  33
  Scientific　knowledge　and　its　object　differ　from　opinion　and　the
  object　of　opinion　in　that　scientific　knowledge　is　commensurately
  universal　and　proceeds　by　necessary　connexions；　and　that　which　is
  necessary　cannot　be　otherwise。　So　though　there　are　things　which　are
  true　and　real　and　yet　can　be　otherwise；　scientific　knowledge　clearly
  does　not　concern　them：　if　it　did；　things　which　can　be　otherwise
  would　be　incapable　of　being　otherwise。　Nor　are　they　any　concern　of
  rational　intuition…by　rational　intuition　I　mean　an　originative
  source　of　scientific　knowledge…nor　of　indemonstrable　knowledge；
  which　is　the　grasping　of　the　immediate　premiss。　Since　then　rational
  intuition；　science；　and　opinion；　and　what　is　revealed　by　these
  terms；　are　the　only　things　that　can　be　'true'；　it　follows　that　it　is
  opinion　that　is　concerned　with　that　which　may　be　true　or　false；　and
  can　be　otherwise：　opinion　in　fact　is　the　grasp　of　a　premiss　which　is
  immediate　but　not　necessary。　This　view　also　fits　the　observed　facts；
  for　opinion　is　unstable；　and　so　is　the　kind　of　being　we　have　described
  as　its　object。　Besides；　when　a　man　thinks　a　truth　incapable　of　being
  otherwise　he　always　thinks　that　he　knows　it；　never　that　he　opines
  it。　He　thinks　that　he　opines　when　he　thinks　that　a　connexion；　though
  actually　so；　may　quite　easily　be　otherwise；　for　he　believes　that
  such　is　the　proper　object　of　opinion；　while　the　necessary　is　the
  object　of　knowledge。
  In　what　sense；　then；　can　the　same　thing　be　the　object　of　both
  opinion　and　knowledge？　And　if　any　one　chooses　to　maintain　that　all
  that　he　knows　he　can　also　opine；　why　should　not　opinion　be
  knowledge？　For　he　that　knows　and　he　that　opines　will　follow　the　same
  train　of　thought　through　the　same　middle　terms　until　the　immediate
  premisses　are　reached；　because　it　is　possible　to　opine　not　only　the
  fact　but　also　the　reasoned　fact；　and　the　reason　is　the　middle　term；　so
  that；　since　the　former　knows；　he　that　opines　also　has　knowledge。
  The　truth　perhaps　is　that　if　a　man　grasp　truths　that　cannot　be　other
  than　they　are；　in　the　way　in　which　he　grasps　the　definitions　through
  which　demonstrations　take　place；　he　will　have　not　opinion　but
  knowledge：　if　on　the　other　hand　he　apprehends　these　attributes　as
  inhering　in　their　subjects；　but　not　in　virtue　of　the　subjects'
  substance　and　essential　nature　possesses　opinion　and　not　genuine
  knowledge；　and　his　opinion；　if　obtained　through　immediate　premisses；
  will　be　both　of　the　fact　and　of　the　reasoned　fact；　if　not　so　obtained；
  of　the　fact　alone。　The　object　of　opinion　and　knowledge　is　not　quite
  identical；　it　is　only　in　a　sense　identical；　just　as　the　object　of　true
  and　false　opinion　is　in　a　sense　identical。　The　sense　in　which　some
  maintain　that　true　and　false　opinion　can　have　the　same　object　leads
  them　to　embrace　many　strange　doctrines；　particularly　the　doctrine　that
  what　a　man　opines　falsely　he　does　not　opine　at　all。　There　are　really
  many　senses　of　'identical'；　and　in　one　sense　the　object　of　true　and
  false　opinion　can　be　the　same；　in　another　it　cannot。　Thus；　to　have　a
  true　opinion　that　the　diagonal　is　commensurate　with　the　side　would
  be　absurd：　but　because　the　diagonal　with　which　they　are　both　concerned
  is　the　same；　the　two　opinions　have　objects　so　far　the　same：　on　the
  other　hand；　as　regards　their　essential　definable　nature　these
  objects　differ。　The　identity　of　the　objects　of　knowledge　and　opinion
  is　similar。　Knowledge　is　the　apprehension　of；　e。g。　the　attribute
  'animal'　as　incapable　of　being　otherwise；　opinion　the　apprehension
  of　'animal'　as　capable　of　being　otherwise…e。g。　the　apprehension　that
  animal　is　an　element　in　the　essential　nature　of　man　is　knowledge；
  the　apprehension　of　animal　as　predicable　of　man　but　not　as　an
  element　in　man's　essential　nature　is　opinion：　man　is　the　subject　in
  both　judgements；　but　the　mode　of　inherence　differs。
  This　also　shows　that　one　cannot　opine　and　know　the　same　thing
  simultaneously；　for　then　one　would　apprehend　the　same　thing　as　both
  capable　and　incapable　of　being　otherwise…an　impossibility。　Knowledge
  and　opinion　of　the　same　thing　can　co…exist　in　two　different　people
  in　the　sense　we　have　explained；　but　not　simultaneously　in　the　same
  person。　That　would　involve　a　man's　simultaneously　apprehending；　e。g。
  （1）　that　man　is　essentially　animal…i。e。　cannot　be　other　than
  animal…and　（2）　that　man　is　not　essentially　animal；　that　is；　we　may
  assume；　may　be　other　than　animal。
  Further　consideration　of　modes　of　thinking　and　their　distribution
  under　the　heads　of　discursive　thought；　intuition；　science；　art；
  practical　wisdom；　and　metaphysical　thinking；　belongs　rather　partly
  to　natural　science；　partly　to　moral　philosophy。
  34
  Quick　wit　is　a　faculty　of　hitting　upon　the　middle　term
  instantaneously。　It　would　be　exemplified　by　a　man　who　saw　that　the
  moon　has　her　bright　side　always　turned　towards　the　sun；　and　quickly
  grasped　the　cause　of　this；　namely　that　she　borrows　her　light　from　him；
  or　observed　somebody　in　conversation　with　a　man　of　wealth　and
  divined　that　he　was　borrowing　money；　or　that　the　friendship　of　these
  people　sprang　from　a　common　enmity。　In　all　these　instances　he　has　seen
  the　major　and　minor　terms　and　then　grasped　the　causes；　the　middle
  terms。
  Let　A　represent　'bright　side　turned　sunward'；　B　'lighted　from　the
  sun'；　C　the　moon。　Then　B；　'lighted　from　the　sun'　is　predicable　of　C；
  the　moon；　and　A；　'having　her　bright　side　towards　the　source　of　her
  light'；　is　predicable　of　B。　So　A　is　predicable　of　C　through　B。
  Book　II
  1
  THE　kinds　of　question　we　ask　are　as　many　as　the　kinds　of　things
  which　we　know。　They　are　in　fact　four：…（1）　whether　the　connexion　of
  an　attribute　with　a　thing　is　a　fact；　（2）　what　is　the　reason　of　the
  connexion；　（3）　whether　a　thing　exists；　（4）　What　is　the　nature　of　the
  thing。　Thus；　when　our　question　concerns　a　complex　of　thing　and
  attribute　and　we　ask　whether　the　thing　is　thus　or　otherwise
  qualified…whether；　e。g。　the　sun　suffers　eclipse　or　not…then　we　are
  asking　as　t