darwin and modern science-第137部分

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he　hereditary　and　the　acquired　factors　in　the　mental　lifeis　the　task　which　lies　before　genetic　and　comparative　psychology。　　They　interact　throughout　the　whole　of　life；　and　their　interactions　are　very　complex。　　No　one　can　read　the　chapters　of　〃The　Descent　of　Man〃　which　Darwin　devotes　to　a　consideration　of　the　mental　characters　of　man　and　animals　without　noticing；　on　the　one　hand；　how　sedulous　he　is　in　his　search　for　hereditary　foundations；　and；　on　the　other　hand；　how　fully　he　realises　the　importance　of　acquired　habits　of　mind。　　The　fact　that　educability　itself　has　innate　tendenciesis　in　fact　a　partially　differentiated　educabilityrenders　the　unravelling　of　the　factors　of　mental　progress　all　the　more　difficult。

In　his　comparison　of　the　mental　powers　of　men　and　animals　it　was　essential　that　Darwin　should　lay　stress　on　points　of　similarity　rather　than　on　points　of　difference。　　Seeking　to　establish　a　doctrine　of　evolution；　with　its　basal　concept　of　continuity　of　process　and　community　of　character；　he　was　bound　to　render　clear　and　to　emphasise　the　contention　that　the　difference　in　mind　between　man　and　the　higher　animals；　great　as　it　is；　is　one　of　degree　and　not　of　kind。　　To　this　end　Darwin　not　only　recorded　a　large　number　of　valuable　observations　of　his　own；　and　collected　a　considerable　body　of　information　from　reliable　sources；　he　presented　the　whole　subject　in　a　new　light　and　showed　that　a　natural　history　of　mind　might　be　written　and　that　this　method　of　study　offered　a　wide　and　rich　field　for　investigation。　　Of　course　those　who　regarded　the　study　of　mind　only　as　a　branch　of　metaphysics　smiled　at　the　philosophical　ineptitude　of　the　mere　man　of　science。　　But　the　investigation；　on　natural　history　lines；　has　been　prosecuted　with　a　large　measure　of　success。　　Much　indeed　still　remains　to　be　done；　for　special　training　is　required；　and　the　workers　are　still　few。　　Promise　for　the　future　is　however　afforded　by　the　fact　that　investigation　is　prosecuted　on　experimental　lines　and　that　something　like　organised　methods　of　research　are　taking　form。　　There　is　now　but　little　reliance　on　casual　observations　recorded　by　those　who　have　not　undergone　the　necessary　discipline　in　these　methods。　　There　is　also　some　change　of　emphasis　in　formulating　conclusions。　　Now　that　the　general　evolutionary　thesis　is　fully　and　freely　accepted　by　those　who　carry　on　such　researches；　more　stress　is　laid　on　the　differentiation　of　the　stages　of　evolutionary　advance　than　on　the　fact　of　their　underlying　community　of　nature。　　The　conceptual　intelligence　which　is　especially　characteristic　of　the　higher　mental　procedure　of　man　is　more　firmly　distinguished　from　the　perceptual　intelligence　which　he　shares　with　the　lower　animalsdistinguished　now　as　a　higher　product　of　evolution；　no　longer　as　differing　in　origin　or　different　in　kind。　　Some　progress　has　been　made；　on　the　one　hand　in　rendering　an　account　of　intelligent　profiting　by　experience　under　the　guidance　of　pleasure　and　pain　in　the　perceptual　field；　on　lines　predetermined　by　instinctive　differentiation　for　biological　ends；　and　on　the　other　hand　in　elucidating　the　method　of　conceptual　thought　employed；　for　example；　by　the　investigator　himself　in　interpreting　the　perceptual　experience　of　the　lower　animals。

Thus　there　is　a　growing　tendency　to　realise　more　fully　that　there　are　two　orders　of　educabilityfirst　an　educability　of　the　perceptual　intelligence　based　on　the　biological　foundation　of　instinct；　and　secondly　an　educability　of　the　conceptual　intelligence　which　refashions　and　rearranges　the　data　afforded　by　previous　inheritance　and　acquisition。　　It　is　in　relation　to　this　second　and　higher　order　of　educability　that　the　cerebrum　of　man　shows　so　large　an　increase　of　mass　and　a　yet　larger　increase　of　effective　surface　through　its　rich　convolutions。　　It　is　through　educability　of　this　order　that　the　human　child　is　brought　intellectually　and　affectively　into　touch　with　the　ideal　constructions　by　means　of　which　man　has　endeavoured；　with　more　or　less　success；　to　reach　an　interpretation　of　nature；　and　to　guide　the　course　of　the　further　evolution　of　his　raceideal　constructions　which　form　part　of　man's　environment。

It　formed　no　part　of　Darwin's　purpose　to　consider；　save　in　broad　outline；　the　methods；　or　to　discuss　in　any　fulness　of　detail　the　results　of　the　process　by　which　a　differentiation　of　the　mental　faculties　of　man　from　those　of　the　lower　animals　has　been　brought　abouta　differentiation　the　existence　of　which　he　again　and　again　acknowledges。　　His　purpose　was　rather　to　show　that；　notwithstanding　this　differentiation；　there　is　basal　community　in　kind。　　This　must　be　remembered　in　considering　his　treatment　of　the　biological　foundations　on　which　man's　systems　of　ethics　are　built。　　He　definitely　stated　that　he　approached　the　subject　〃exclusively　from　the　side　of　natural　history。〃　　（〃Descent　of　Man〃；　Vol。　I。　page　149。）　　His　general　conclusion　is　that　the　moral　sense　is　fundamentally　identical　with　the　social　instincts；　which　have　been　developed　for　the　good　of　the　community；　and　he　suggests　that　the　concept　which　thus　enables　us　to　interpret　the　biological　ground…plan　of　morals　also　enables　us　to　frame　a　rational　ideal　of　the　moral　end。　　〃As　the　social　instincts；〃　he　says　（Ibid。　page　185。）；　〃both　of　man　and　the　lower　animals　have　no　doubt　been　developed　by　nearly　the　same　steps；　it　would　be　advisable；　if　found　practicable；　to　use　the　same　definition　in　both　cases；　and　to　take　as　the　standard　of　morality；　the　general　good　or　welfare　of　the　community；　rather　than　the　general　happiness。〃　　But　the　kind　of　community　for　the　good　of　which　the　social　instincts　of　animals　and　primitive　men　were　biologically　developed　may　be　different　from　that　which　is　the　product　of　civilisation；　as　Darwin　no　doubt　realised。　　Darwin's　contention　was　that　conscience　is　a　social　instinct　and　has　been　evolved　because　it　is　useful　to　the　tribe　in　the　struggle　for　existence　against　other　tribes。　　On　the　other　hand；　J。S。　Mill　urged　that　the　moral　feelings　are　not　innate　but　acquired；　and　Bain　held　the　same　view；　believing　that　the　moral　sense　is　acquired　by　each　individual　during　his　life…time。　　Darwin；　who　notes　（Ibid。　page　150　（footnote）。）　their　opinion　with　his　usual　candour；　adds　that　〃on　the　general　theory　of　evolution　this　is　at　least　extremely　improbable。　　It　is　impossible　to　enter　into　the　question　here：　　much　turns　on　the　exact　connotation　of　the　terms　〃conscience〃　and　〃moral　sense；〃　and　on　the　meaning　we　attach　to　the　statement　that　the　moral　sense　is　fundamentally　identical　with　the　social　instincts。

Presumably　the　majority　of　those　who　approach　the　subjects　discussed　in　the　third；　fourth　and　fifth　chapters　of　〃The　Descent　of　Man〃　in　the　full　conviction　that　mental　phenomena；　not　less　than　organic　phenomena；　have　a　natural　genesis；　would；　without　hesitation；　admit　that　the　intellectual　and　moral　systems　of　civilised　man　are　ideal　constructions；　the　products　of　conceptual　thought；　and　that　as　such　they　are；　in　their　developed　form；　acquired。　　The　moral　sentiments　are　the　emotional　analogues　of　highly　developed　concepts。　　This　does　not　however　imply　that　they　are　outside　the　range　of　natural　history　treatment。　　Even　though　it　may　be　desirable　to　differentiate　the　moral　conduct　of　men　from　the　social　behaviour　of　animals　（to　which　some　such　term　as　〃pre…moral〃　or　〃quasi…moral〃　may　be　applied）；　still　the　fact　remains　that；　as　Darwin　showed；　there　is　abundant　evidence　of　the　occurrence　of　such　social　behavioursocial　behaviour　which；　even　granted　that　it　is　in　large　part　intelligently　acquired；　and　is　itself　so　far　a　product　of　educability；　is　of　survival　value。　　It　makes　for　that　integration　without　which　no　social　group　could　hold　together　and　escape　elimination。　　Furthermore；　even　if　we　grant　that　such　behaviour　is　intelligently　acquired；　that　is　to　say　arises　through　the　modification　of　hereditary　instincts　and　emotions；　the　fact　remains　that　only　through　these　instinctive　and　emotional　data　is　afforded　the　primary　tissue　of　the　experience　which　is　susceptible　of　such　modification。

Darwin　sought　to　show；　and　succeeded　in　showing；　that　for　the　intellectual　and　moral　life　there　are　instinctive　foundations　which　a　biological　treatment　alone　can　disclose。　　It　is　true　that　he　did　not　in　all　cases　analytically　distinguish　the　foundations　from　the　superstructure。　　Even　to…　day　we　are　scarcely　in　a　position　to　do　so　adequately。　　But　his　treatment　was　of　great　value　in　giving　an　impetus　to　further　research。　　This　value　indeed　can　scarcely　be　overestimated。　　And　when　the　natural　history　of　the　mental　operations　shall　have　been　written；　the　cardinal　fact　will　stand　forth；　that　the　instinctive　and　emotional　foundations　are　the　outcome　of　biological　evolution　and　have　been　ingrained　in　the　race　through　natural　selection。　　We　shall　more　clearly　realise　that　educability　itself　is　a　product　of　natural　selection；　though　the　specific　results　acquired　through　cerebral　modifications　are　not　transmitted　through　heredity。　　It　will；　perhaps；　also　be　realised　that　the　instinctive　foundations　of　social　behaviour　are；　for　us；　somewhat　out　of　date　and　have　undergone　but　little　change　throughout　the　progress　of　civilisation；　because　natural　selection　has　long　since　ceased　to　be　the　domi