Yes；　he　said。
  Now　then；　I　said；　making　an　offering　of　the　third　or　last　argument　to　Zeus
  the　Saviour；　let　us　begin　again；　and　ask；　in　the　first　place；　whether　it　is
  or　is　not　possible　for　a　person　to　know　that　he　knows　and　does　not　know
  what　he　knows　and　does　not　know；　and　in　the　second　place；　whether；　if
  perfectly　possible；　such　knowledge　is　of　any　use。
  That　is　what　we　have　to　consider；　he　said。
  And　here；　Critias；　I　said；　I　hope　that　you　will　find　a　way　out　of　a
  difficulty　into　which　I　have　got　myself。　　Shall　I　tell　you　the　nature　of
  the　difficulty？
  By　all　means；　he　replied。
  Does　not　what　you　have　been　saying；　if　true；　amount　to　this：　　that　there
  must　be　a　single　science　which　is　wholly　a　science　of　itself　and　of　other
  sciences；　and　that　the　same　is　also　the　science　of　the　absence　of　science？
  Yes。
  But　consider　how　monstrous　this　proposition　is；　my　friend：　　in　any　parallel
  case；　the　impossibility　will　be　transparent　to　you。
  How　is　that？　and　in　what　cases　do　you　mean？
  In　such　cases　as　this：　　Suppose　that　there　is　a　kind　of　vision　which　is　not
  like　ordinary　vision；　but　a　vision　of　itself　and　of　other　sorts　of　vision；
  and　of　the　defect　of　them；　which　in　seeing　sees　no　colour；　but　only　itself
  and　other　sorts　of　vision：　　Do　you　think　that　there　is　such　a　kind　of
  vision？
  Certainly　not。
  Or　is　there　a　kind　of　hearing　which　hears　no　sound　at　all；　but　only　itself
  and　other　sorts　of　hearing；　or　the　defects　of　them？
  There　is　not。
  Or　take　all　the　senses：　　can　you　imagine　that　there　is　any　sense　of　itself
  and　of　other　senses；　but　which　is　incapable　of　perceiving　the　objects　of
  the　senses？
  I　think　not。
  Could　there　be　any　desire　which　is　not　the　desire　of　any　pleasure；　but　of
  itself；　and　of　all　other　desires？
  Certainly　not。
  Or　can　you　imagine　a　wish　which　wishes　for　no　good；　but　only　for　itself　and
  all　other　wishes？
  I　should　answer；　No。
  Or　would　you　say　that　there　is　a　love　which　is　not　the　love　of　beauty；　but
  of　itself　and　of　other　loves？
  I　should　not。
  Or　did　you　ever　know　of　a　fear　which　fears　itself　or　other　fears；　but　has
  no　object　of　fear？
  I　never　did；　he　said。
  Or　of　an　opinion　which　is　an　opinion　of　itself　and　of　other　opinions；　and
  which　has　no　opinion　on　the　subjects　of　opinion　in　general？
  Certainly　not。
  But　surely　we　are　assuming　a　science　of　this　kind；　which；　having　no
  subject…matter；　is　a　science　of　itself　and　of　the　other　sciences？
  Yes；　that　is　what　is　affirmed。
  But　how　strange　is　this；　if　it　be　indeed　true：　　we　must　not　however　as　yet
  absolutely　deny　the　possibility　of　such　a　science；　let　us　rather　consider
  the　matter。
  You　are　quite　right。
  Well　then；　this　science　of　which　we　are　speaking　is　a　science　of　something；
  and　is　of　a　nature　to　be　a　science　of　something？
  Yes。
  Just　as　that　which　is　greater　is　of　a　nature　to　be　greater　than　something
  else？　　（Socrates　is　intending　to　show　that　science　differs　from　the　object
  of　science；　as　any　other　relative　differs　from　the　object　of　relation。　　But
  where　there　is　comparisongreater；　less；　heavier；　lighter；　and　the　likea
  relation　to　self　as　well　as　to　other　things　involves　an　absolute
  contradiction；　and　in　other　cases；　as　in　the　case　of　the　senses；　is　hardly
  conceivable。　　The　use　of　the　genitive　after　the　comparative　in　Greek；
  （Greek）；　creates　an　unavoidable　obscurity　in　the　translation。）
  Yes。
  Which　is　less；　if　the　other　is　conceived　to　be　greater？
  To　be　sure。
  And　if　we　could　find　something　which　is　at　once　greater　than　itself；　and
  greater　than　other　great　things；　but　not　greater　than　those　things　in
  comparison　of　which　the　others　are　greater；　then　that　thing　would　have　the
  property　of　being　greater　and　also　less　than　itself？
  That；　Socrates；　he　said；　is　the　inevitable　inference。
  Or　if　there　be　a　double　which　is　double　of　itself　and　of　other　doubles；
  these　will　be　halves；　for　the　double　is　relative　to　the　half？
  That　is　true。
  And　that　which　is　greater　than　itself　will　also　be　less；　and　that　which　is
  heavier　will　also　be　lighter；　and　that　which　is　older　will　also　be　younger：
  and　the　same　of　other　things；　that　which　has　a　nature　relative　to　self　will
  retain　also　the　nature　of　its　object：　　I　mean　to　say；　for　example；　that
  hearing　is；　as　we　say；　of　sound　or　voice。　　Is　that　true？
  Yes。
  Then　if　hearing　hears　itself；　it　must　hear　a　voice；　for　there　is　no　other
  way　of　hearing。
  Certainly。
  And　sight　also；　my　excellent　friend；　if　it　sees　itself　must　see　a　colour；
  for　sight　cannot　see　that　which　has　no　colour。
  No。
  Do　you　remark；　Critias；　that　in　several　of　the　examples　which　have　been
  recited　the　notion　of　a　relation　to　self　is　altogether　inadmissible；　and　in
  other　cases　hardly　credibleinadmissible；　for　example；　in　the　case　of
  magnitudes；　numbers；　and　the　like？
  Very　true。
  But　in　the　case　of　hearing　and　sight；　or　in　the　power　of　self…motion；　and
  the　power　of　heat　to　burn；　this　relation　to　self　will　be　regarded　as
  incredible　by　some；　but　perhaps　not　by　others。　　And　some　great　man；　my
  friend；　is　wanted；　who　will　satisfactorily　determine　for　us；　whether　there
  is　nothing　which　has　an　inherent　property　of　relation　to　self；　or　some
  things　only　and　not　others；　and　whether　in　this　class　of　self…related
  things；　if　there　be　such　a　class；　that　science　which　is　called　wisdom　or
  temperance　is　included。　　I　altogether　distrust　my　own　power　of　determining
  these　matters：　　I　am　not　certain　whether　there　is　such　a　science　of　science
  at　all；　and　even　if　there　be；　I　should　not　acknowledge　this　to　be　wisdom　or
  temperance；　until　I　can　also　see　whether　such　a　science　would　or　would　not
  do　us　any　good；　for　I　have　an　impression　that　temperance　is　a　benefit　and　a
  good。　　And　therefore；　O　son　of　Callaeschrus；　as　you　maintain　that
  temperance　or　wisdom　is　a　science　of　science；　and　also　of　the　absence　of
  science；　I　will　request　you　to　show　in　the　first　place；　as　I　was　saying
  before；　the　possibility；　and　in　the　second　place；　the　advantage；　of　such　a
  science；　and　then　perhaps　you　may　satisfy　me　that　you　are　right　in　your
  view　of　temperance。
  Critias　heard　me　say　this；　and　saw　that　I　was　in　a　difficulty；　and　as　one
  person　when　another　yawns　in　his　presence　catches　the　infection　of　yawning
  from　him；　so　did　he　seem　to　be　driven　into　a　difficulty　by　my　difficulty。
  But　as　he　had　a　reputation　to　maintain；　he　was　ashamed　to　admit　before　the
  company　that　he　could　not　answer　my　challenge　or　determine　the　question　at
  issue；　and　he　made　an　unintelligible　attempt　to　hide　his　perplexity。　　In
  order　that　the　argument　might　proceed；　I　said　to　him；　Well　then　Critias；　if
  you　like；　let　us　assume　that　there　is　this　science　of　science；　whether　the
  assumption　is　right　or　wrong　may　hereafter　be　investigated。　　Admitting　the
  existence　of　it；　will　you　tell　me　how　such　a　science　enables　us　to
  distinguish　what　we　know　or　do　not　know；　which；　as　we　were　saying；　is
  self…knowledge　or　wisdom：　　so　we　were　saying？
  Yes；　Socrates；　he　said；　and　that　I　think　is　certainly　true：　　for　he　who　has
  this　science　or　knowledge　which　knows　itself　will　become　like　the　knowledge
  which　he　has；　in　the　same　way　that　he　who　has　swiftness　will　be　swift；　and
  he　who　has　beauty　will　be　beautiful；　and　he　who　has　knowledge　will　know。
  In　the　same　way　he　who　has　that　knowledge　which　is　self…knowing；　will　know
  himself。
  I　do　not　doubt；　I　said；　that　a　man　will　know　himself；　when　he　possesses
  that　which　has　self…knowledge：　　but　what　necessity　is　there　that；　having
  this；　he　should　know　what　he　knows　and　what　he　does　not　know？
  Because；　Socrates；　they　are　the　same。
  Very　likely；　I　said；　but　I　remain　as　stupid　as　ever；　for　still　I　fail　to
  comprehend　how　this　knowing　what　you　know　and　do　not　know　is　the　same　as
  the　knowledge　of　self。
  What　do　you　mean？　he　said。
  This　is　what　I　mean；　I　replied：　　I　will　admit　that　there　is　a　science　of
  science；can　this　do　more　than　determine　that　of　two　things　one　is　and　the
  other　is　not　science　or　knowledge？
  No；　just　that。
  But　is　knowledge　or　want　of　knowledge　of　health　the　same