darwin and modern science-第141节

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ased　on　the　general　principles　of　human　thought。　　The　evolution　hypothesis　presupposes；　then；　human　thought　and　its　principles。　　And　not　only　the　abstract　logical　principles　are　thus　presupposed。　　The　evolution　hypothesis　purports　to　be　not　only　a　formal　arrangement　of　phenomena；　but　to　express　also　the　law　of　a　real　process。　　It　supposes；　then；　that　the　real　dataall　that　in　our　knowledge　which　we　do　not　produce　ourselves；　but　which　we　in　the　main　simply　receiveare　subjected　to　laws　which　are　at　least　analogous　to　the　logical　relations　of　our　thoughts；　in　other　words；　it　assumes　the　validity　of　the　principle　of　causality。　　If　organic　species　could　arise　without　cause　there　would　be　no　use　in　framing　hypotheses。　　Only　if　we　assume　the　principle　of　causality；　is　there　a　problem　to　solve。

Though　Darwinism　has　had　a　great　influence　on　philosophy　considered　as　a　striving　after　a　scientific　view　of　the　world；　yet　here　is　a　point　of　view　the　epistemologicalwhere　philosophy　is　not　only　independent　but　reaches　beyond　any　result　of　natural　science。　　Perhaps　it　will　be　said：　　the　powers　and　functions　of　organic　beings　only　persist　（perhaps　also　only　arise）　when　they　correspond　sufficiently　to　the　conditions　under　which　the　struggle　of　life　is　to　go　on。　　Human　thought　itself　is；　then；　a　variation　（or　a　mutation）　which　has　been　able　to　persist　and　to　survive。　　Is　not；　then；　the　problem　of　knowledge　solved　by　the　evolution　hypothesis？　　Spencer　had　given　an　affirmative　answer　to　this　question　before　the　appearance　of　〃The　Origin　of　Species〃。　　For　the　individual；　he　said；　there　is　an　a　priori；　original；　basis　（or　Anlage）　for　all　mental　life；　but　in　the　species　all　powers　have　developed　in　reciprocity　with　external　conditions。　　Knowledge　is　here　considered　from　the　practical　point　of　view；　as　a　weapon　in　the　struggle　for　life；　as　an　〃organon〃　which　has　been　continuously　in　use　for　generations。　　In　recent　years　the　economic　or　pragmatic　epistemology；　as　developed　by　Avenarius　and　Mach　in　Germany；　and　by　James　in　America；　points　in　the　same　direction。　　Science；　it　is　said；　only　maintains　those　principles　and　presuppositions　which　are　necessary　to　the　simplest　and　clearest　orientation　in　the　world　of　experience。　　All　assumptions　which　cannot　be　applied　to　experience　and　to　practical　work；　will　successively　be　eliminated。

In　these　views　a　striking　and　important　application　is　made　of　the　idea　of　struggle　for　life　to　the　development　of　human　thought。　　Thought　must；　as　all　other　things　in　the　world；　struggle　for　life。　　But　this　whole　consideration　belongs　to　psychology；　not　to　the　theory　of　knowledge　（epistemology）；　which　is　concerned　only　with　the　validity　of　knowledge；　not　with　its　historical　origin。　　Every　hypothesis　to　explain　the　origin　of　knowledge　must　submit　to　cross…examination　by　the　theory　of　knowledge；　because　it　works　with　the　fundamental　forms　and　principles　of　human　thought。　　We　cannot　go　further　back　than　these　forms　and　principles；　which　it　is　the　aim　of　epistemology　to　ascertain　and　for　which　no　further　reason　can　be　given。　　（The　present　writer；　many　years　ago；　in　his　〃Psychology〃　（Copenhagen；　1882；　English　translation　London；　1891）；　criticised　the　evolutionistic　treatment　of　the　problem　of　knowledge　from　the　Kantian　point　of　view。）

But　there　is　another　side　of　the　problem　which　is；　perhaps；　of　more　importance　and　which　epistemology　generally　overlooks。　　If　new　variations　can　arise；　not　only　in　organic　but　perhaps　also　in　inorganic　nature；　new　tasks　are　placed　before　the　human　mind。　　The　question　is；　then；　if　it　has　forms　in　which　there　is　room　for　the　new　matter？　　We　are　here　touching　a　possibility　which　the　great　master　of　epistemology　did　not　bring　to　light。　Kant　supposed　confidently　that　no　other　matter　of　knowledge　could　stream　forth　from　the　dark　source　which　he　called　〃the　thing…in…itself；〃　than　such　as　could　be　synthesised　in　our　existing　forms　of　knowledge。　　He　mentions　the　possibility　of　other　forms　than　the　human；　and　warns　us　against　the　dogmatic　assumption　that　the　human　conception　of　existence　should　be　absolutely　adequate。　　But　he　seems　to　be　quite　sure　that　the　thing…in…　itself　works　constantly；　and　consequently　always　gives　us　only　what　our　powers　can　master。　　This　assumption　was　a　consequence　of　Kant's　rationalistic　tendency；　but　one　for　which　no　warrant　can　be　given。　　Evolutionism　and　systematism　are　opposing　tendencies　which　can　never　be　absolutely　harmonised　one　with　the　other。　　Evolution　may　at　any　time　break　some　form　which　the　system…monger　regards　as　finally　established。　　Darwin　himself　felt　a　great　difference　in　looking　at　variation　as　an　evolutionist　and　as　a　systematist。　　When　he　was　working　at　his　evolution　theory；　he　was　very　glad　to　find　variations；　but　they　were　a　hindrance　to　him　when　he　worked　as　a　systematist；　in　preparing　his　work　on　Cirripedia。　　He　says　in　a　letter：　　〃I　had　thought　the　same　parts　of　the　same　species　more　resemble　（than　they　do　anyhow　in　Cirripedia）　objects　cast　in　the　same　mould。　　Systematic　work　would　be　easy　were　it　not　for　this　confounded　variation；　which；　however；　is　pleasant　to　me　as　a　speculatist；　though　odious　to　me　as　a　systematist。〃　　（〃Life　and　Letters〃；　Vol。　II。　page　37。）　　He　could　indeed　be　angry　with　variations　even　as　an　evolutionist；　but　then　only　because　he　could　not　explain　them；　not　because　he　could　not　classify　them。　　〃If；　as　I　must　think；　external　conditions　produce　little　DIRECT　effect；　what　the　devil　determines　each　particular　variation？〃　　（Ibid。　page　232。）　　What　Darwin　experienced　in　his　particular　domain　holds　good　of　all　knowledge。　　All　knowledge　is　systematic；　in　so　far　as　it　strives　to　put　phenomena　in　quite　definite　relations；　one　to　another。　　But　the　systematisation　can　never　be　complete。　　And　here　Darwin　has　contributed　much　to　widen　the　world　for　us。　　He　has　shown　us　forces　and　tendencies　in　nature　which　make　absolute　systems　impossible；　at　the　same　time　that　they　give　us　new　objects　and　problems。　　There　is　still　a　place　for　what　Lessing　called　〃the　unceasing　striving　after　truth；〃　while　〃absolute　truth〃　（in　the　sense　of　a　closed　system）　is　unattainable　so　long　as　life　and　experience　are　going　on。

There　is　here　a　special　remark　to　be　made。　　As　we　have　seen　above；　recent　research　has　shown　that　natural　selection　or　struggle　for　life　is　no　explanation　of　variations。　　Hugo　de　Vries　distinguishes　between　partial　and　embryonal　variations；　or　between　variations　and　mutations；　only　the　last…　named　being　heritable；　and　therefore　of　importance　for　the　origin　of　new　species。　　But　the　existence　of　variations　is　not　only　of　interest　for　the　problem　of　the　origin　of　species；　it　has　also　a　more　general　interest。　　An　individual　does　not　lose　its　importance　for　knowledge；　because　its　qualities　are　not　heritable。　　On　the　contrary；　in　higher　beings　at　least；　individual　peculiarities　will　become　more　and　more　independent　objects　of　interest。　　Knowledge　takes　account　of　the　biographies　not　only　of　species；　but　also　of　individuals：　　it　seeks　to　find　the　law　of　development　of　the　single　individual。　　（The　new　science　of　Ecology　occupies　an　intermediate　position　between　the　biography　of　species　and　the　biography　of　individuals。　Compare　〃Congress　of　Arts　and　Science〃；　St　Louis；　Vol。　V。　1906　（the　Reports　of　Drude　and　Robinson）　and　the　work　of　my　colleague　E。　Warming。）　　As　Leibniz　said　long　ago；　individuality　consists　in　the　law　of　the　changes　of　a　being。　　〃La　loi　du　changement　fait　l'individualite　de　chaque　substance。〃　　Here　is　a　world　which　is　almost　new　for　science；　which　till　now　has　mainly　occupied　itself　with　general　laws　and　forms。　　But　these　are　ultimately　only　means　to　understand　the　individual　phenomena；　in　whose　nature　and　history　a　manifold　of　laws　and　forms　always　cooperate。　　The　importance　of　this　remark　will　appear　in　the　sequel。

V。

To　many　people　the　Darwinian　theory　of　natural　selection　or　struggle　for　existence　seemed　to　change　the　whole　conception　of　life；　and　particularly　all　the　conditions　on　which　the　validity　of　ethical　ideas　depends。　　If　only　that　has　persistence　which　can　be　adapted　to　a　given　condition；　what　will　then　be　the　fate　of　our　ideals；　of　our　standards　of　good　and　evil？　　Blind　force　seems　to　reign；　and　the　only　thing　that　counts　seems　to　be　the　most　heedless　use　of　power。　　Darwinism；　it　was　said；　has　proclaimed　brutality。　　No　other　difference　seems　permanent　save　that　between　the　sound；　powerful　and　happy　on　the　one　side；　the　sick；　feeble　and　unhappy　on　the　other；　and　every　attempt　to　alleviate　this　difference　seems　to　lead　to　general　enervation。　　Some　of　those　who　interpreted　Darwinism　in　this　manner　felt　an　aesthetic　delight　in　contemplating　the　heedlessness　and　energy　of　the　great　struggle　for　existence　and　anticipated　the　realisation　of　a　higher　human　type　as　the　outcome　of　it：　　so　Nietzsche　and　his　followers。　　Others　recognising　the　same　consequences　in　Darwinism　regarded　these　as　one　of　the　strongest　objections　against　it；　so　Duhring　and　Kropotkin　（in　his　earlier　works）。

This　interpretation　of　Darwinism　was　frequent　in　the　interval　between　the　two　main　works　of　Darwin〃The　Origin　of　Species〃　and　〃The　Descent　of　Man〃。　　But　even　during　this　interval　it　was　evident　to　an　attentive　reader　that　Darwin　himself　did　not　found　his　stand