philosophy　and　to　such　rules　of　diet　in　his　daily　life　as　will　give
  him　inward　sobriety　and　therewith　quickness　in　learning；　a　good
  memory；　and　reasoning　power；　the　kind　of　life　which　is　opposed　to　this
  he　consistently　hates。　Those　who　have　not　the　true　philosophic　temper；
  but　a　mere　surface　colouring　of　opinions　penetrating；　like　sunburn；
  only　skin　deep；　when　they　see　how　great　the　range　of　studies　is；　how
  much　labour　is　involved　in　it；　and　how　necessary　to　the　pursuit　it
  is　to　have　an　orderly　regulation　of　the　daily　life；　come　to　the
  conclusion　that　the　thing　is　difficult　and　impossible　for　them；　and
  are　actually　incapable　of　carrying　out　the　course　of　study；　while　some
  of　them　persuade　themselves　that　they　have　sufficiently　studied　the
  whole　matter　and　have　no　need　of　any　further　effort。　This　is　the
  sure　test　and　is　the　safest　one　to　apply　to　those　who　live　in　luxury
  and　are　incapable　of　continuous　effort；　it　ensures　that　such　a　man
  shall　not　throw　the　blame　upon　his　teacher　but　on　himself；　because
  he　cannot　bring　to　the　pursuit　all　the　qualities　necessary　to　it。　Thus
  it　came　about　that　I　said　to　Dionysios　what　I　did　say　on　that
  occasion。
  I　did　not；　however；　give　a　complete　exposition；　nor　did　Dionysios
  ask　for　one。　For　he　professed　to　know　many；　and　those　the　most
  important；　points；　and　to　have　a　sufficient　hold　of　them　through
  instruction　given　by　others。　I　hear　also　that　he　has　since　written
  about　what　he　heard　from　me；　composing　what　professes　to　be　his　own
  handbook；　very　different；　so　he　says；　from　the　doctrines　which　he
  heard　from　me；　but　of　its　contents　I　know　nothing；　I　know　indeed
  that　others　have　written　on　the　same　subjects；　but　who　they　are；　is
  more　than　they　know　themselves。　Thus　much　at　least；　I　can　say　about
  all　writers；　past　or　future；　who　say　they　know　the　things　to　which　I
  devote　myself；　whether　by　hearing　the　teaching　of　me　or　of　others；
  or　by　their　own　discoveries…that　according　to　my　view　it　is　not
  possible　for　them　to　have　any　real　skill　in　the　matter。　There
  neither　is　nor　ever　will　be　a　treatise　of　mine　on　the　subject。　For
  it　does　not　admit　of　exposition　like　other　branches　of　knowledge；
  but　after　much　converse　about　the　matter　itself　and　a　life　lived
  together；　suddenly　a　light；　as　it　were；　is　kindled　in　one　soul　by　a
  flame　that　leaps　to　it　from　another；　and　thereafter　sustains　itself。
  Yet　this　much　I　know…that　if　the　things　were　written　or　put　into
  words；　it　would　be　done　best　by　me；　and　that；　if　they　were　written
  badly；　I　should　be　the　person　most　pained。　Again；　if　they　had　appeared
  to　me　to　admit　adequately　of　writing　and　exposition；　what　task　in　life
  could　I　have　performed　nobler　than　this；　to　write　what　is　of　great
  service　to　mankind　and　to　bring　the　nature　of　things　into　the　light
  for　all　to　see？　But　I　do　not　think　it　a　good　thing　for　men　that
  there　should　be　a　disquisition；　as　it　is　called；　on　this
  topic…except　for　some　few；　who　are　able　with　a　little　teaching　to　find
  it　out　for　themselves。　As　for　the　rest；　it　would　fill　some　of　them
  quite　illogically　with　a　mistaken　feeling　of　contempt；　and　others　with
  lofty　and　vain…glorious　expectations；　as　though　they　had　learnt
  something　high　and　mighty。
  On　this　point　I　intend　to　speak　a　little　more　at　length；　for
  perhaps；　when　I　have　done　so；　things　will　be　clearer　with　regard　to　my
  present　subject。　There　is　an　argument　which　holds　good　against　the　man
  ventures　to　put　anything　whatever　into　writing　on　questions　of　this
  nature；　it　has　often　before　been　stated　by　me；　and　it　seems　suitable
  to　the　present　occasion。
  For　everything　that　exists　there　are　three　instruments　by　which
  the　knowledge　of　it　is　necessarily　imparted；　fourth；　there　is　the
  knowledge　itself；　and；　as　fifth；　we　must　count　the　thing　itself
  which　is　known　and　truly　exists。　The　first　is　the　name；　the；　second
  the　definition；　the　third。　the　image；　and　the　fourth　the　knowledge。　If
  you　wish　to　learn　what　I　mean；　take　these　in　the　case　of　one　instance；
  and　so　understand　them　in　the　case　of　all。　A　circle　is　a　thing
  spoken　of；　and　its　name　is　that　very　word　which　we　have　just
  uttered。　The　second　thing　belonging　to　it　is　its　definition；　made　up
  names　and　verbal　forms。　For　that　which　has　the　name　〃round；〃
  〃annular；〃　or；　〃circle；〃　might　be　defined　as　that　which　has　the
  distance　from　its　circumference　to　its　centre　everywhere　equal。　Third；
  comes　that　which　is　drawn　and　rubbed　out　again；　or　turned　on　a　lathe
  and　broken　up…none　of　which　things　can　happen　to　the　circle
  itself…to　which　the　other　things；　mentioned　have　reference；　for　it
  is　something　of　a　different　order　from　them。　Fourth；　comes
  knowledge；　intelligence　and　right　opinion　about　these　things。　Under
  this　one　head　we　must　group　everything　which　has　its　existence；　not　in
  words　nor　in　bodily　shapes；　but　in　souls…from　which　it　is　dear　that　it
  is　something　different　from　the　nature　of　the　circle　itself　and　from
  the　three　things　mentioned　before。　Of　these　things　intelligence
  comes　closest　in　kinship　and　likeness　to　the　fifth；　and　the　others　are
  farther　distant。
  The　same　applies　to　straight　as　well　as　to　circular　form；　to
  colours；　to　the　good；　the；　beautiful；　the　just；　to　all　bodies
  whether　manufactured　or　coming　into　being　in　the　course　of　nature；
  to　fire；　water；　and　all　such　things；　to　every　living　being；　to
  character　in　souls；　and　to　all　things　done　and　suffered。　For　in　the
  case　of　all　these；　no　one；　if　he　has　not　some　how　or　other　got　hold　of
  the　four　things　first　mentioned；　can　ever　be　completely　a　partaker
  of　knowledge　of　the　fifth。　Further；　on　account　of　the　weakness　of
  language；　these　（i。e。；　the　four）　attempt　to　show　what　each　thing　is
  like；　not　less　than　what　each　thing　is。　For　this　reason　no　man　of
  intelligence　will　venture　to　express　his　philosophical　views　in
  language；　especially　not　in　language　that　is　unchangeable；　which　is
  true　of　that　which　is　set　down　in　written　characters。
  Again　you　must　learn　the　point　which　comes　next。　Every　circle；　of
  those　which　are　by　the　act　of　man　drawn　or　even　turned　on　a　lathe；
  is　full　of　that　which　is　opposite　to　the　fifth　thing。　For　everywhere
  it　has　contact　with　the　straight。　But　the　circle　itself；　we　say；　has
  nothing　in　either　smaller　or　greater；　of　that　which　is　its　opposite。
  We　say　also　that　the　name　is　not　a　thing　of　permanence　for　any　of
  them；　and　that　nothing　prevents　the　things　now　called　round　from　being
  called　straight；　and　the　straight　things　round；　for　those　who　make
  changes　and　call　things　by　opposite　names；　nothing　will　be　less
  permanent　（than　a　name）。　Again　with　regard　to　the　definition；　if　it　is
  made　up　of　names　and　verbal　forms；　the　same　remark　holds　that　there　is
  no　sufficiently　durable　permanence　in　it。　And　there　is　no　end　to　the
  instances　of　the　ambiguity　from　which　each　of　the　four　suffers；　but
  the　greatest　of　them　is　that　which　we　mentioned　a　little　earlier；
  that；　whereas　there　are　two　things；　that　which　has　real　being；　and
  that　which　is　only　a　quality；　when　the　soul　is　seeking　to　know；　not
  the　quality；　but　the　essence；　each　of　the　four；　presenting　to　the　soul
  by　word　and　in　act　that　which　it　is　not　seeking　（i。e。；　the　quality）；　a
  thing　open　to　refutation　by　the　senses；　being　merely　the　thing
  presented　to　the　soul　in　each　particular　case　whether　by　statement
  or　the　act　of　showing；　fills；　one　may　say；　every　man　with　puzzlement
  and　perplexity。
  Now　in　subjects　in　which；　by　reason　of　our　defective　education；　we
  have　not　been　accustomed　even　to　search　for　the　truth；　but　are
  satisfied　with　whatever　images　are　presented　to　us；　we　are　not　held　up
  to　ridicule　by　one　another；　the　questioned　by　questioners；　who　can
  pull　to　pieces　and　criticise　the　four　things。　But　in　subjects　where　we
  try　to　compel　a　man　to　give　a　clear　answer　about　the　fifth；　any　one　of
  those　who　are　capable　of　overthrowing　an　antagonist　gets　the　better　of
  us；　and　makes　the　man；　who　gives　an　exposition　in　speech　or　writing　or
  in　replies　to　questions；　appear　to　most　of　his　hearers　to　know　nothing
  of　the　things　on　which　he　is　attempting　to　write　or　speak；　for　they
  are　sometimes　not　aware　that　it　is　not　the　mind　of　the　writer　or
  speaker　which　is　proved　to　be　at　fault；　but　the　defective　nature　of
  each　of　the　four　instruments。　The　process　however　of　dealing　with
  all　of　these；　as　the　mind　moves　up　and　down　to　each　in　turn；　does
  after　much　effort　give　birth　in　a　well…constituted　mind　to　knowledge
  of　that　which　is　well　constituted。　But　if　a　man　is　ill…constituted
  by　nature　（as　the　state　of　the　soul　is　naturally　in　the　majority
  both　in　its　capacity　for　learning　and　in　what　is　called　moral
  character）…or　it　may　have　become　so　by　deterioration…not　even
  Lynceus　could　endow　such　men　with　the　power　of　sight。
  In　one　word；　the　man　who　has　no　natural　kinship　with　this　matter
  cannot　be　made　akin　to　it　by　quickness　of　learning　or　memory；　for　it
  cannot　be　engendered　at　all　in　natures　which　are　foreign　to　it。
  Therefore；　if　men　are　not　by　nature　kinship