evidence　of　mathematical　truths　is　that　all　the　argument　is　on　one
  side。　There　are　no　objections；　and　no　answers　to　objections。　But　on
  every　subject　on　which　difference　of　opinion　is　possible；　the　truth
  depends　on　a　balance　to　be　struck　between　two　sets　of　conflicting
  reasons。　Even　in　natural　philosophy；　there　is　always　some　other
  explanation　possible　of　the　same　facts；　some　geocentric　theory　instead
  of　heliocentric；　some　phlogiston　instead　of　oxygen；　and　it　has　to　be
  shown　why　that　other　theory　cannot　be　the　true　one：　and　until　this
  is　shown；　and　until　we　know　how　it　is　shown；　we　do　not　understand
  the　grounds　of　our　opinion。
  But　when　we　turn　to　subjects　infinitely　more　complicated；　to　morals；
  religion；　politics；　social　relations；　and　the　business　of　life；
  three…fourths　of　the　arguments　for　every　disputed　opinion　consist　in
  dispelling　the　appearances　which　favour　some　opinion　different　from
  it。　The　greatest　orator；　save　one；　of　antiquity；　has　left　it　on　record
  that　he　always　studied　his　adversary's　case　with　as　great；　if　not
  still　greater；　intensity　than　even　his　own。　What　Cicero　practised　as
  the　means　of　forensic　success　requires　to　be　imitated　by　all　who　study
  any　subject　in　order　to　arrive　at　the　truth。　He　who　knows　only　his　own
  side　of　the　case；　knows　little　of　that。　His　reasons　may　be　good；　and
  no　one　may　have　been　able　to　refute　them。　But　if　he　is　equally
  unable　to　refute　the　reasons　on　the　opposite　side；　if　he　does　not　so
  much　as　know　what　they　are；　he　has　no　ground　for　preferring　either
  opinion。　The　rational　position　for　him　would　be　suspension　of
  judgment；　and　unless　he　contents　himself　with　that；　he　is　either　led
  by　authority；　or　adopts；　like　the　generality　of　the　world；　the　side　to
  which　he　feels　most　inclination。　Nor　is　it　enough　that　he　should
  hear　the　arguments　of　adversaries　from　his　own　teachers；　presented
  as　they　state　them；　and　accompanied　by　what　they　offer　as　refutations。
  That　is　not　the　way　to　do　justice　to　the　arguments；　or　bring　them　into
  real　contact　with　his　own　mind。　He　must　be　able　to　hear　them　from
  persons　who　actually　believe　them；　who　defend　them　in　earnest；　and
  do　their　very　utmost　for　them。　He　must　know　them　in　their　most
  plausible　and　persuasive　form；　he　must　feel　the　whole　force　of　the
  difficulty　which　the　true　view　of　the　subject　has　to　encounter　and
  dispose　of；　else　he　will　never　really　possess　himself　of　the　portion
  of　truth　which　meets　and　removes　that　difficulty。
  Ninety…nine　in　a　hundred　of　what　are　called　educated　men　are　in　this
  condition；　even　of　those　who　can　argue　fluently　for　their　opinions。
  Their　conclusion　may　be　true；　but　it　might　be　false　for　anything
  they　know：　they　have　never　thrown　themselves　into　the　mental
  position　of　those　who　think　differently　from　them；　and　considered　what
  such　persons　may　have　to　say；　and　consequently　they　do　not；　in　any
  proper　sense　of　the　word；　know　the　doctrine　which　they　themselves
  profess。　They　do　not　know　those　parts　of　it　which　explain　and
  justify　the　remainder；　the　considerations　which　show　that　a　fact　which
  seemingly　conflicts　with　another　is　reconcilable　with　it；　or　that；
  of　two　apparently　strong　reasons；　one　and　not　the　other　ought　to　be
  preferred。　All　that　part　of　the　truth　which　turns　the　scale；　and
  decides　the　judgment　of　a　completely　informed　mind；　they　are　strangers
  to；　nor　is　it　ever　really　known；　but　to　those　who　have　attended
  equally　and　impartially　to　both　sides；　and　endeavoured　to　see　the
  reasons　of　both　in　the　strongest　light。　So　essential　is　this
  discipline　to　a　real　understanding　of　moral　and　human　subjects；　that
  if　opponents　of　all　important　truths　do　not　exist；　it　is　indispensable
  to　imagine　them；　and　supply　them　with　the　strongest　arguments　which
  the　most　skilful　devil's　advocate　can　conjure　up。
  To　abate　the　force　of　these　considerations；　an　enemy　of　free
  discussion　may　be　supposed　to　say；　that　there　is　no　necessity　for
  mankind　in　general　to　know　and　understand　all　that　can　be　said　against
  or　for　their　opinions　by　philosophers　and　theologians。　That　it　is
  not　needful　for　common　men　to　be　able　to　expose　all　the
  misstatements　or　fallacies　of　an　ingenious　opponent。　That　it　is　enough
  if　there　is　always　somebody　capable　of　answering　them；　so　that　nothing
  likely　to　mislead　uninstructed　persons　remains　unrefuted。　That
  simple　minds；　having　been　taught　the　obvious　grounds　of　the　truths
  inculcated　on　them；　may　trust　to　authority　for　the　rest；　and　being
  aware　that　they　have　neither　knowledge　nor　talent　to　resolve　every
  difficulty　which　can　be　raised；　may　repose　in　the　assurance　that　all
  those　which　have　been　raised　have　been　or　can　be　answered；　by　those
  who　are　specially　trained　to　the　task。
  Conceding　to　this　view　of　the　subject　the　utmost　that　can　be　claimed
  for　it　by　those　most　easily　satisfied　with　the　amount　of　understanding
  of　truth　which　ought　to　accompany　the　belief　of　it；　even　so；　the
  argument　for　free　discussion　is　no　way　weakened。　For　even　this
  doctrine　acknowledges　that　mankind　ought　to　have　a　rational
  assurance　that　all　objections　have　been　satisfactorily　answered；　and
  how　are　they　to　be　answered　if　that　which　requires　to　be　answered　is
  not　spoken？　or　how　can　the　answer　be　known　to　be　satisfactory；　if
  the　objectors　have　no　opportunity　of　showing　that　it　is
  unsatisfactory？　If　not　the　public；　at　least　the　philosophers　and
  theologians　who　are　to　resolve　the　difficulties；　must　make
  themselves　familiar　with　those　difficulties　in　their　most　puzzling
  form；　and　this　cannot　be　accomplished　unless　they　are　freely　stated；
  and　placed　in　the　most　advantageous　light　which　they　admit　of。　The
  Catholic　Church　has　its　own　way　of　dealing　with　this　embarrassing
  problem。　It　makes　a　broad　separation　between　those　who　can　be
  permitted　to　receive　its　doctrines　on　conviction；　and　those　who　must
  accept　them　on　trust。　Neither；　indeed；　are　allowed　any　choice　as　to
  what　they　will　accept；　but　the　clergy；　such　at　least　as　can　be　fully
  confided　in；　may　admissibly　and　meritoriously　make　themselves
  acquainted　with　the　arguments　of　opponents；　in　order　to　answer　them；
  and　may；　therefore；　read　heretical　books；　the　laity；　not　unless　by
  special　permission；　hard　to　be　obtained。　This　discipline　recognises
  a　knowledge　of　the　enemy's　case　as　beneficial　to　the　teachers；　but
  finds　means；　consistent　with　this；　of　denying　it　to　the　rest　of　the
  world：　thus　giving　to　the　elite　more　mental　culture；　though　not　more
  mental　freedom；　than　it　allows　to　the　mass。　By　this　device　it　succeeds
  in　obtaining　the　kind　of　mental　superiority　which　its　purposes
  require；　for　though　culture　without　freedom　never　made　a　large　and
  liberal　mind；　it　can　make　a　clever　nisi　prius　advocate　of　a　cause。　But
  in　countries　professing　Protestantism；　this　resource　is　denied；
  since　Protestants　hold；　at　least　in　theory；　that　the　responsibility
  for　the　choice　of　a　religion　must　be　borne　by　each　for　himself；　and
  cannot　be　thrown　off　upon　teachers。　Besides；　in　the　present　state　of
  the　world；　it　is　practically　impossible　that　writings　which　are　read
  by　the　instructed　can　be　kept　from　the　uninstructed。　If　the　teachers
  of　mankind　are　to　be　cognisant　of　all　that　they　ought　to　know；
  everything　must　be　free　to　be　written　and　published　without　restraint。
  If；　however；　the　mischievous　operation　of　the　absence　of　free
  discussion；　when　the　received　opinions　are　true；　were　confined　to
  leaving　men　ignorant　of　the　grounds　of　those　opinions；　it　might　be
  thought　that　this；　if　an　intellectual；　is　no　moral　evil；　and　does
  not　affect　the　worth　of　the　opinions；　regarded　in　their　influence　on
  the　character。　The　fact；　however；　is；　that　not　only　the　grounds　of　the
  opinion　are　forgotten　in　the　absence　of　discussion；　but　too　often
  the　meaning　of　the　opinion　itself。　The　words　which　convey　it　cease
  to　suggest　ideas；　or　suggest　only　a　small　portion　of　those　they　were
  originally　employed　to　communicate。　Instead　of　a　vivid　conception
  and　a　living　belief；　there　remain　only　a　few　phrases　retained　by　rote；
  or；　if　any　part；　the　shell　and　husk　only　of　the　meaning　is　retained；
  the　finer　essence　being　lost。　The　great　chapter　in　human　history　which
  this　fact　occupies　and　fills；　cannot　be　too　earnestly　studied　and
  meditated　on。
  It　is　illustrated　in　the　experience　of　almost　all　ethical
  doctrines　and　religious　creeds。　They　are　all　full　of　meaning　and
  vitality　to　those　who　originate　them；　and　to　the　direct　disciples　of
  the　originators。　Their　meaning　continues　to　be　felt　in　undiminished
  strength；　and　is　perhaps　brought　out　into　even　fuller　consciousness；
  so　long　as　the　struggle　lasts　to　give　the　doctrine　or　creed　an
  ascendancy　over　other　creeds。　At　last　it　either　prevails；　and
  becomes　the　general　opinion；　or　i