whatever　may　bridge　the　gap。　　　　　The　knowledge；　then；　is　realized　by　means　of　bodily　organs：　through　these；　which　＇in　the　embodied　soul＇　are　almost　of　one　growth　with　it；　being　at　least　its　continuations；　it　comes　into　something　like　unity　with　the　alien；　since　this　mutual　approach　brings　about　a　certain　degree　of　identity　＇which　is　the　basis　of　knowledge＇。　　　　　Admitting；　then；　that　some　contact　with　an　object　is　necessary　for　knowing　it；　the　question　of　a　medium　falls　to　the　ground　in　the　case　of　things　identified　by　any　form　of　touch；　but　in　the　case　of　sight…　we　leave　hearing　over　for　the　present…　we　are　still　in　doubt；　is　there　need　of　some　bodily　substance　between　the　eye　and　the　illumined　object？　　　　　No：　such　an　intervening　material　may　be　a　favouring　circumstance；　but　essentially　it　adds　nothing　to　seeing　power。　！　　　　Dense　bodies；　such　as　clay；　actually　prevent　sight；　the　less　material　the　intervening　substance　is；　the　more　clearly　we　see；　the　intervening　substance；　then；　is　a　hindrance；　or；　if　not　that；　at　least　not　a　help。　　　　　It　will　be　objected　that　vision　implies　that　whatever　intervenes　between　seen　and　seer　must　first　＇and　progressively＇　experience　the　object　and　be；　as　it　were；　shaped　to　it；　we　will　be　reminded　that　＇vision　is　not　a　direct　and　single　relation　between　agent　and　object；　but　is　the　perception　of　something　radiated　since＇　anyone　facing　to　the　object　from　the　side　opposite　to　ourselves　sees　it　equally；　we　will　be　asked　to　deduce　that　if　all　the　space　intervening　between　seen　and　seer　did　not　carry　the　impression　of　the　object　we　could　not　receive　it。　　　　　But　all　the　need　is　met　when　the　impression　reaches　that　which　is　adapted　to　receive　it；　there　is　no　need　for　the　intervening　space　to　be　impressed。　If　it　is；　the　impression　will　be　of　quite　another　order：　the　rod　between　the　fisher's　hand　and　the　torpedo　fish　is　not　affected　in　the　same　way　as　the　hand　that　feels　the　shock。　And　yet　there　too；　if　rod　and　line　did　not　intervene；　the　hand　would　not　be　affected…　though　even　that　may　be　questioned；　since　after　all　the　fisherman；　we　are　told；　is　numbed　if　the　torpedo　merely　lies　in　his　net。　　　　　The　whole　matter　seems　to　bring　us　back　to　that　sympathy　of　which　we　have　treated。　If　a　certain　thing　is　of　a　nature　to　be　sympathetically　affected　by　another　in　virtue　of　some　similitude　between　them；　then　anything　intervening；　not　sharing　in　that　similitude；　will　not　be　affected；　or　at　least　not　similarly。　If　this　be　so；　anything　naturally　disposed　to　be　affected　will　take　the　impression　more　vividly　in　the　absence　of　intervening　substance；　even　of　some　substance　capable；　itself；　of　being　affected。　　　　　2。　If　sight　depends　upon　the　linking　of　the　light　of　vision　with　the　light　leading　progressively　to　the　illumined　object；　then；　by　the　very　hypothesis；　one　intervening　substance；　the　light；　is　indispensable：　but　if　the　illuminated　body；　which　is　the　object　of　vision；　serves　as　an　agent　operating　certain　changes；　some　such　change　might　very　well　impinge　immediately　upon　the　eye；　requiring　no　medium；　this　all　the　more；　since　as　things　are　the　intervening　substance；　which　actually　does　exist；　is　in　some　degree　changed　at　the　point　of　contact　with　the　eye　＇and　so　cannot　be　in　itself　a　requisite　to　vision＇。　　　　　Those　who　have　made　vision　a　forth…going　act　＇and　not　an　in…coming　from　the　object＇　need　not　postulate　an　intervening　substance…　unless；　indeed；　to　provide　against　the　ray　from　the　eye　failing　on　its　path…　but　this　is　a　ray　of　light　and　light　flies　straight。　Those　who　make　vision　depend　upon　resistance　are　obliged　to　postulate　an　intervening　substance。　　　　　The　champions　of　the　image；　with　its　transit　through　a　void；　are　seeking　the　way　of　least　resistance；　but　since　the　entire　absence　of　intervenient　gives　a　still　easier　path　they　will　not　oppose　that　hypothesis。　　　　　So；　too；　those　that　explain　vision　by　sympathy　must　recognize　that　an　intervening　substance　will　be　a　hindrance　as　tending　to　check　or　block　or　enfeeble　that　sympathy；　this　theory；　especially；　requires　the　admission　that　any　intervenient；　and　particularly　one　of　kindred　nature；　must　blunt　the　perception　by　itself　absorbing　part　of　the　activity。　Apply　fire　to　a　body　continuous　through　and　through；　and　no　doubt　the　core　will　be　less　affected　than　the　surface：　but　where　we　are　dealing　with　the　sympathetic　parts　of　one　living　being；　there　will　scarcely　be　less　sensation　because　of　the　intervening　substance；　or；　if　there　should　be；　the　degree　of　sensation　will　still　be　proportionate　to　the　nature　of　the　separate　part；　with　the　intervenient　acting　merely　as　a　certain　limitation；　this；　though；　will　not　be　the　case　where　the　element　introduced　is　of　a　kind　to　overleap　the　bridge。　　　　　But　this　is　saying　that　the　sympathetic　quality　of　the　universe　depends　upon　its　being　one　living　thing；　and　that　our　amenability　to　experience　depends　upon　our　belonging　integrally　to　that　unity；　would　it　not　follow　that　continuity　is　a　condition　of　any　perception　of　a　remote　object？　　　　　The　explanation　is　that　continuity　and　its　concomitant；　the　bridging　substance；　come　into　play　because　a　living　being　must　be　a　continuous　thing；　but　that；　none　the　less；　the　receiving　of　impression　is　not　an　essentially　necessary　result　of　continuity；　if　it　were；　everything　would　receive　such　impression　from　everything　else；　and　if　thing　is　affected　by　thing　in　various　separate　orders；　there　can　be　no　further　question　of　any　universal　need　of　intervening　substance。　　　　　Why　it　should　be　especially　requisite　in　the　act　of　seeing　would　have　to　be　explained：　in　general；　an　object　passing　through　the　air　does　not　affect　it　beyond　dividing　it；　when　a　stone　falls；　the　air　simply　yields；　nor　is　it　reasonable　to　explain　the　natural　direction　of　movement　by　resistance；　to　do　so　would　bring　us　to　the　absurdity　that　resistance　accounts　for　the　upward　movement　of　fire；　which　on　the　contrary；　overcomes　the　resistance　of　the　air　by　its　own　essentially　quick　energy。　If　we　are　told　that　the　resistance　is　brought　more　swiftly　into　play　by　the　very　swiftness　of　the　ascending　body；　that　would　be　a　mere　accidental　circumstance；　not　a　cause　of　the　upward　motion：　in　trees　the　upthrust　from　the　root　depends　on　no　such　external　propulsion；　we；　too；　in　our　movements　cleave　the　air　and　are　in　no　wise　forwarded　by　its　resistance；　it　simply　flows　in　from　behind　to　fill　the　void　we　make。　　　　　If　the　severance　of　the　air　by　such　bodies　leaves　it　unaffected；　why　must　there　be　any　severance　before　the　images　of　sight　can　reach　us？　　　　　And；　further；　once　we　reject　the　theory　that　these　images　reach　us　by　way　of　some　outstreaming　from　the　objects　seen；　there　is　no　reason　to　think　of　the　air　being　affected　and　passing　on　to　us；　in　a　progression　of　impression；　what　has　been　impressed　upon　itself。　　　　　If　our　perception　is　to　depend　upon　previous　impressions　made　upon　the　air；　then　we　have　no　direct　knowledge　of　the　object　of　vision；　but　know　it　only　as　through　an　intermediary；　in　the　same　way　as　we　are　aware　of　warmth　where　it　is　not　the　distant　fire　itself　that　warms　us；　but　the　warmed　intervening　air。　That　is　a　matter　of　contact；　but　sight　is　not　produced　by　contact：　the　application　of　an　object　to　the　eye　would　not　produce　sight；　what　is　required　is　the　illumination　of　the　intervening　medium；　for　the　air　in　itself　is　a　dark　substance：　If　it　were　not　for　this　dark　substance　there　would　probably　be　no　reason　for　the　existence　of　light：　the　dark　intervening　matter　is　a　barrier；　and　vision　requires　that　it　be　overcome　by　light。　Perhaps　also　the　reason　why　an　object　brought　close　to　the　eye　cannot　be　seen　is　that　it　confronts　us　with　a　double　obscuration；　its　own　and　that　of　the　air。　　　　　3。　For　the　most　convincing　proof　that　vision　does　not　depend　upon　the　transmission　of　impressions　of　any　kind　made　upon　the　air；　we　have　only　to　consider　that　in　the　darkness　of　night　we　can　see　a　fire　and　the　stars　and　their　very　shapes。　　　　　No　one　will　pretend　that　these　forms　are　reproduced　upon　the　darkness　and　come　to　us　in　linked　progression；　if　the　fire　thus　rayed　out　its　own　form；　there　would　be　an　end　to　the　darkness。　In　the　blackest　night；　when　the　very　stars　are　hidden　and　show　no　gleam　of　their　light；　we　can　see　the　fire　of　the　beacon…stations　and　of　maritime　signal…towers。　　　　　Now　if；　in　defiance　of　all　that　the　senses　tell　us；　we　are　to　believe　that　in　these　examples　the　fire　＇as　light＇　traverses　the　air；　then；　in　so　far　as　anything　is　visible；　it　must　be　that　dimmed　reproduction　in　the　air；　not　the　fire　itself。　But　if　an　object　can　be　seen　on　the　other　side　of　some　intervening　darkness；　much　more　would　it　be　visible　with　nothing　intervening。　　　　　We　may　hold　one　thing　certain：　the　impossibility　of　vision　without　an　intervening　substance　does　not　depend　upon　that　absence　in　itself：　the　sole　reason　is　that；　with　the　absence；　there　would　be　an　end　to　the　sympathy　reigning　in　the　living　whole　and　relating　the　parts　to　each　other　in　an　existent　unity。　　　　　Perception　of　every　kind　seems　to　depend　on　the　fact　that　our　universe　is　a　whole　sympathetic　to　itself：　that　it　is　so；　appears　from　the　universal　participation　in　power　from　member　to　member；　and　especially　in　remote　power。　　　　　No　doubt　it　would　be　worth　enquiry…　though　we　pass　it　for　the　present…　wha