第17章

Thefactofchiefsignificanceforushere，isthatorganizationis，under

oneofitsaspects，asetofappliancesforthemultiplicationofenergies

——applianceswhich，bytheirsuccessiveactions，maketheenergyeventually

givenoutenormousascomparedwiththeenergywhichliberatedit。Aphysical

stimulusaffectinganorganofsense，isinsomecasesmultipliedbylocal

nervousagents;theaugmentedenergyisagainmultipliedinsomepartof

thespinalcordorinsomehigherganglion;andthisusuallyagainmultiplied

inthecerebrumanddischargedtothemuscles，isthereenormouslymultiplied

inthecontractingfibres。OfthesetransformationsOnlysomecarriedon

centrallyhaveaccompanyingstatesofconsciousness;sothat，manifestly，

therecanbenoquantitativeequivalenceeitherbetweenthesensationand

theoriginalstimulus，orbetweenitandtheeventualmotion。Allwecan

sayisthat，otherthingsequal，thethreevarytogether;sothatifinone

casesuccessivestagesofincreaseare1，9，27，270theyinanothercase

be2，18，54，540。Thiskindofcorrelationisallwhichtheforegoingfacts

imply。Butnowletusglanceattheindirectevidenceswhichconfirmthe

viewthatmentalandphysicalforcesareconnected，thoughinanindirectway。Nowadaysnoonedoubtsthatmentalprocessesandtheresultingactions

arecontingentonthepresenceofanervoussystem;andthat，greatlyobscured

asitisbynumerousandinvolvedconditions，ageneralrelationmaybetraced

betweenthesizeofthissystemandthequantityofmentalactionasmeasured

byitsresults。Further，thisnervousapparatushasachemicalconstitution

onwhichitsactivity，depends;andthereisoneelementinitbetweenthe

amountofwhichandtheamountoffunctionperformed，thereisanascertained

connexion:theproportionofphosphoruspresentinthebrainbeingthesmallest

ininfancy，oldage，andidiotcy，andthegreatestduringtheprimeoflife。

Note，next，thattheevolutionofthoughtandemotionvaries，otherthings

equal，withthesupplyofbloodtothebrain。Ontheonehand，anarrest

ofthecerebralcirculationfromstoppageoftheheart，immediatelyentails

unconsciousness。Ontheotherhand，excessofcerebralcirculation（unless

itissuchastocauseunduepressure）resultsinunusualexcitement。Not

thequantityonlybutalsothecondition，ofthebloodpassingthroughthe

brain，influencesthementalmanifestations。Thearterialcurrentsmustbe

dulyaerated，toproducethenormalamountofcerebration。Ifthebloodis

notallowedtoexchangeitscarbondioxideforoxygen，thereresultsasphyxia，

withitsaccompanyingstoppageofideasandfeelings。Thatthequantityof

consciousnessis，otherthingsequal，determinedbytheconstituentsofthe

blood，isunmistakablyseenintheexaltationwhichcertainvegeto—alkalies

commonlyproducewhentakenintoit。Thegentleexhilarationwhichteaand

coffeecreate，isfamiliartoall;andthoughthegorgeousimaginationsand

intensefeelingsproducedbyopiumandhashish，havebeenexperiencedby

few（inthiscountryatleast），thetestimonyofthosewhohaveexperienced

themissufficientlyconclusive。Yetanotherproofthatthegenesisofthe

mentalenergiesdependsonchemicalchange，isaffordedbythefactthat

theeffeteproductsseparatedfromthebloodbythekidneys，varyincharacter

withtheamountofcerebralaction。Excessiveactivityofmindisaccompaniedbyexcretionofanunusualquantityofthealkalinephosphates。§71b。Butnowafterrecognizingtheclassesoffactswhichunite

toprovethatthelawofmetamorphosis，andinapartialwaythelawofequivalence，

holdsbetweenphysicalenergiesandnervousenergies，letusenteruponthe

ultimatequestion——Whatisthenatureoftherelationbetweennervousenergies

andmentalstates？howarewetoconceivemolecularchangesinthebrain

asproducingfeelings，orfeelingsasproducingmolecularchangeswhichendinmotion？InhislectureonAnimalAutomatism，Prof。Huxleysetforththeproofs

thatalikeinanimalsandinMan，thegreatmassofthosecomplexactions

whichweassociatewithpurposeandintelligencemaybeperformedautomatically:

andcontendedthattheconsciousnesswhichordinarilyaccompaniesthemis

outsidetheseriesofchangesconstitutingthenervouscoordination——does

notformalinkinthechainbutissimplya"concomitant"ora

"collateralproduct。"Insofarasitcorrelatesthenervousactions

bywhichourbodilyandmentalactivitiesarecarriedon，withphysicalforces

ingeneral，Prof。Huxley\'sconclusionaccordswiththeconclusionsabove

setforth;butinsofarasitregardstheaccompanyingstatesofconsciousness

ascollateralproductsonly，andnotasfactorsinanydegree，itdiffers

fromthem。HereIcannotdomorethanindicatethesetofevidencesbywhichIthinkmyownconclusionissupportedifnotjustified。Oneofthemwehaveinthefactsofhabit，whichprovethatstatesof

consciousnesswhichwereatfirstaccompanimentsofsensoryimpressionsand

resultingmotions，graduallyceasetobeconcomitants。Thelittleboywho

isbeingtaughttoreadhasdefiniteperceptionsandthoughtsabouttheform

andsoundofeachletter，butinmaturityallthesehavelapsed，sothat

onlythewordsareconsciouslyrecognized:eachletterproducesitseffect

automatically。So，too，thegirllearningtoknitisabsorbedinthinking

ofeachmovementmadeunderthedirectionofhereyes，buteventuallythe

movementscometobeperformedalmostlikethoseofamachinewhilehermind

isotherwiseoccupied。Suchcasesseematvariancewiththebeliefthatconsciousness

isoutsidethelinesofnervouscommunication，andsuggest，ratherthatit

existsinanylineofcommunicationincourseofestablishmentanddisappears

whenthecommunicationbecomesperfect。Ifitisnotalinkintheline，itisnoteasytoseehowthesechangescanarise。Sundryfactsappeartoimplythatconsciousnessisneedfulasaninitiator

incaseswheretherearenoexternalstimulitosetuptheco—ordinatednervous

changes:thenervousstructures，thoughcapableofdoingeverythingrequired

ifsetgoing，arenotsetgoingunlesstherearisesanidea。Nowthisimplies

thatanidea，orco—ordinatedsetoffeelings，hasthepowerofworkingchanges

inthenervouscentresandsettingupmotions:thestateofconsciousnessisafactor。Thenwhatwemaycallpassiveemotions——emotionswhichdonotinitiate

actions——apparentlyimplythatbetweenfeelingsandnervouschangesthere

isnotmerelyaconcomitancebutaphysicalnexus。Intensegrieforanxiety

inonewhoremainsmotionless，isshowntobedirectlydependentonnervous

changesbythefactthatthereisanunusualexcretionofphosphatesbythe

kidneys。Nowunlesswesupposethatinsuchcasesthereisgreatactivity

ofcertainnervousplexusesendinginnothing，wemustsaythatthefeelingisaproductofthemolecularchangesinthem。Oncemorethereisthequestion——iffeelingisnotafactorhowisits

existencetobeaccountedfor？ToanyonewhoholdsinfulltheCartesian

doctrinethatanimalsareautomata，andthatahowlnomoreimpliesfeeling

thandoesthebarkofatoydog，Ihavenothingtosay。Butwhoeverdoes

notholdthis，isobligedtoholdthatasweascribedangerandaffection

toourfellow—men，thoughweliterallyknownosuchfeelingssaveinourselves，

somustweascribethemtoanimalsunderlikeconditions，ifso，however

——iffeelingsarenotfactorsandtheappropriateactionsmightbeautomatically

performedwithoutthem——then，onthesupernaturalhypothesisitmustbe

assumedthatfeelingsweregiventoanimalsfornopurpose，andonthenaturalhypothesisitmustbeassumedthattheyhavearisentodonothing。§71c。Butwhetherfeelingisonlyaconcomitantofcertainnervous

actions，orwhetheritis，asconcludedabove，afactorinsuchactions，

theconnexionbetweenthetwoisinscrutable。Ifwesupposethatinwhich

consciousnessinherestobeanimmaterialsomething，notimplicatedinthese

nervousactionsbutneverthelessaffectedbytheminsuchwayastoproduce

feeling，thenweareobligedtoconceiveofcertainmaterialchanges——molecular

motions——asproducingchangesinsomethinginwhichthereisnothingto

bemoved;andthiswecannotconceive。If，ontheotherhand，weregardthis

somethingcapableofconsciousness，assorelatedtocertainnervouschanges

thatthefeelingsarisinginitjottheminproducingmuscularmotions，then

wemeetthesamedifficultyunderitsconverseaspect。Wehavetothinkof

animmaterialsomething——asomethingwhichisnotmolecularmotion——which

iscapableofaffectingmolecularmotions:wehavetoendowitwiththepower

toworkeffectswhich，sofarasourknowledgegoes，canbeworkedonlybymaterialforces。Sothatthisalternative，too，isinthelastresortinconceivable。Theonlysuppositionhavingconsistencyisthatthatinwhichconsciousness

inheresistheall—pervadingether。Thisweknowcanbeaffectedbymolecules

ofmatterinmotionandconverselycanaffectthemotionsofmolecules;as

witnesstheactionoflightontheretina。Inpursuanceofthissupposition

wemayassumethattheetherwhichpervadesnotonlyallspacebutallmatter，

is，underspecialconditionsincertainpartsofthenervoussystem，capable

ofbeingaffectedbythenervouschangesinsuchwayastoresultinfeeling，

andisreciprocallycapableundertheseconditionsofaffectingthenervous

changes。Butifweacceptthisexplanationwemustassumethatthepotentiality

offeelingisuniversal，andthattheevolutionoffeelingintheethertakes

placeonlyundertheextremelycomplexconditionsoccurringincertainnervous

centres。This，however，isbutasemblanceofanexplanation，sinceweknow

notwhattheetheris，andsince，bytheconfessionofthosemostcapable

ofjudging，nohypothesisthathasbeenframedaccountsforallitspowers。

Suchanexplanationmaybesaidtodonomorethansymbolizethephenomenabysymbolsofunknownnatures。Thusthoughthefactsobligeustosaythatphysicalandpsychicalactions

arecorrelated，andinacertainindirectwayquantitativelycorrelated，

soastosuggesttransformation，yethowthematerialaffectsthemental

andhowthementalaffectsthematerial，aremysterieswhichitisimpossible

tofathom。Buttheyarenotprofoundermysteriesthanthetransformations

ofthephysicalforcesintooneanother。Theyarenotmorecompletelybeyond

ourcomprehensionthanthenaturesofMindandMatter。Theyhavesimplythe

sameinsolubilityasallotherultimatequestions。Wecanlearnnothingmorethanthathereisoneoftheuniformitiesintheorderofphenomena。§72。Ifthegenerallawoftransformationandequivalenceholdsof

theforcesweclassasvitalandmental，itmustholdalsoofthosewhich

weclassassocial。Whatevertakesplaceinasocietyresultseitherfrom

theundirectedphysicalenergiesaround，fromtheseenergiesasdirectedbymen，orfromtheenergiesofthementhemselves。While，asamongprimitivetribes，men\'sactionsaremainlyindependent

ofoneanother，socialforcescanscarcelybesaidtoexist:theycomeinto

existencealongwithco—operation。Theeffectswhichcanbeachievedonly

bythejointactionsofmany，wemaydistinguishassocial。Atfirstthese

areobviouslyduetoaccumulatedindividualefforts，butasfastassocieties

becomelargeandhighlyorganized，theyacquiresuchseparatenessfromindividual

effortsastogivethemacharacteroftheirown。Thenetworkofroadsand

railwaysandtelegraphwires——agenciesintheformationofwhichindividual

laboursweresomergedastobepracticallylost——servetocarryonasocial

lifethatisnolongerthoughtofascausedbytheindependentdoingsof

citizens。Thepricesofstocks，theratesofdiscount，thereporteddemand

forthisorthatcommodity，andthecurrentsofmenandthingssettingto

andfromvariouslocalities，showuslargemovementsandchangesscarcely

atallaffectedbythelivesanddeathsanddeedsofpersons。Buttheseand

multitudinoussocialactivitiesdisplayedinthegrowthoftowns，thestreams

oftrafficintheirstreets，thedailyissueanddistributionofnewspapers，

thedeliveryoffoodatpeople\'sdoors，etc。，areunquestionablytransformed

individualenergies，andhavethesamesourceastheseenergies——thefood

whichthepopulationconsumes。Thecorrelationofthesocialwiththephysical

forcesthroughtheintermediationofthevitalones，is，however，bestshown

inthedifferentamountsofactivitydisplayedbythesamesocietyaccording

asitsmembersaresuppliedwithdifferentamountsofforcefromtheexternal

world。Averybadharvestisfollowedbyadiminutionofbusiness。Factories

areworkedhalf—timerailwaytrafficfalls;retailersfindtheirsaleslessened;

andifthescarcityrisestofamine，athinningofthepopulationstillmore

diminishestheindustrialvivacity。Conversely，anunusuallyabundantsupply

offood，occurringunderconditionsnototherwiseunfavourable，bothexcites

theoldproducinganddistributingagenciesandsetsupnewones。Thesurplus

socialenergyfindsventinspeculativeenterprises。Labourisexpendedin

openingnewchannelsofcommunication。Thereisincreasedencouragementto

thosewhofurnishtheluxuriesoflifeandministertotheaestheticfaculties。

Therearemoremarriages，andagreaterrateofincreaseinpopulation。Thus

thesocietygrowslarger，morecomplex，andmoreactive。Whenthewholeof

thematerialsforsubsistencearenotdrawnfromtheareainhabited，but

arepartlyimported，thepeoplearestillsupportedbycertainharvestselsewhere

grownattheexpenseofcertainphysicalforces，andtheenergiestheyexpendoriginatefromthem。Ifweaskwhencecomethesephysicalforces，thereplyisofcourseas

heretofore——theSun\'srays。Basedasthelifeofasocietyisonanimal

andvegetalproducts，anddependentastheseareonthelightandheatof

theSun，itfollowsthatthechangeswroughtbymenassociallyorganized，

areeffectsofforceshavingacommonoriginwiththosewhichproduceall

theotherordersofchangeswehaveanalyzed。Notonlyistheenergyextended

bythehorseharnessedtotheplough，andbythelabourerguidingit，derived

fromthesamereservoirasistheenergyofthecataractandthehurricane;

buttothissamereservoiraretraceablethosesubtlerandmorecomplexmanifestations

ofenergywhichhumanity，associallyembodied，evolves。Theassertionisstartlingbutitisanunavoidablededuction。Ofthephysicalforcesthataredirectlytransformedintosocialones，

thelikeistobesaid。Currentsofairandwater，whichbeforetheuseof

steamweretheonlyagentsbroughtinaidofmusculareffortforperforming

industrialprocesses，are，aswehaveseen，generatedbysolarheat。And

theinanimatepowerthatnow，tosovastanextent，supplementshumanlabour，

issimilarlyderived。SirJohnHerschelwasthefirsttorecognizethetruth

thattheforceimpellingalocomotive，originallyemanatedfromtheSun。

Stepbystepwegoback——fromthemotionofthepistontotheevaporation

ofthewater;thencetotheheatevolvedduringtheburningofcoal;thence

totheassimilationofcarbonbytheplantsofwhoseimbeddedproductscoal

consists;thencetothecarbondi—oxidefromwhichtheircarbonwasobtained;

andthencetotheraysoflightwhicheffectedthede—oxidation。Solarforces

millionsofyearsagoexpendedontheEarth\'svegetation，andsincelocked

upindeep—seatedstrata，nowsmeltthemetalsrequiredforourmachines，

turnthelathesbywhichthemachinesareshaped，workthemwhenputtogether，

anddistributethefabricstheyproduce。Andsinceeconomyoflabourmakes

possiblealargerpopulation，givesasurplusofhumanpowerthatwouldelse

beabsorbedinmanualoccupations，andthusfacilitatesthedevelopmentof

higherkindsofactivity;thesesocialforceswhicharedirectlycorrelated

withPhysicalforcesancientlyderivedfromtheSun，areonlylessimportant

thanthoseofwhichthecorrelatesarethevitalforcesrecentlyderivedfromit。§73。Manywhoadmitthatamongphysicalphenomenaatlarge，transformation

offorcesisnowestablished，willprobablysaythatinquiryhasnotyet

gonefarenoughtoenableustoassertequivalence。Andinrespectofthe

forcesclassedasvital，mental，andsocial，theevidenceassignedtheywillconsiderbynomeansconclusiveevenoftransformation，muchlessofequivalence。Buttheuniversaltruthabovefollowedoutunderitsvariousaspects，

isacorollaryfromthepersistenceofforce。Fromthepropositionthatforce

canneithercomeintoexistencenorceasetoexist，theseveralforegoing

conclusionsinevitablyfollow。Eachmanifestationofforcecanbeinterpreted

onlyastheeffectofsomeantecedentforce;nomatterwhetheritbeaninorganic

action，ananimalmovement，athought，orafeeling。Eitherbodilyandmental

energies，aswellasinorganicones，arequantitativelycorrelatedtocertain

energiesexpendedintheirproduction，andtocertainotherenergieswhich

theyinitiate;orelsenothingmustbecomesomethingandsomethingmustbecome

nothing。Thealternativesare，todenythepersistenceofforce，ortoadmit

thatfromgivenamountsofantecedentenergiesneithermorenorlessthan

certainphysicalandpsychicalchangescanresult。Thiscorollarycannot

indeedbemademorecertainbyaccumulatingillustrations。Whateverproof

ofcorrelationandequivalenceisreachedbyexperimentalinquiry，isbased

onmeasurementoftheforcesexpendedandtheforcesproduced。But，aswas

showninthelastchapter，anysuchprocessimpliestheuseofsomeunit

offorcewhichisassumedtoremainconstant;anditsconstancycanbeassumed

onlyasbeingacorollaryfromthepersistenceofforce。Howthencanany

reasoningbasedonthiscorollary，provetheequallydirectcorollarythat

whenagivenquantityofforceceasestoexistunderoneform，anequalquantitymustcomeintoexistenceundersomeotherformorforms？"What，then，"itmaybeasked，"istheuseofinvestigations

bywhichtransformationsandequivalenceofforcesissoughttobeinductively

established？Ifthecorrelationcannotbemademorecertainbythemthan

itisalreadydoesnottheiruselessnessnecessarilyfollow？"No。They

areofvalueasdisclosingthemanyparticularimplicationswhichthegeneral

truthdoesnotspecify。Theyareofvalueasteachingushowmuchofone

modeofforceistheequivalentofsomuchofanothermode。Theyareofvalue

asdetectingunderwhatconditionseachmetamorphosisoccurs。Andtheyare

ofvalueasleadingustoinquireinwhatshapetheremnantofforcehas

escaped，whentheapparentresultsarenotequivalenttothecause。

Chapter9TheDirectionofMotion§74。TheAbsoluteCauseofchanges，nomatterwhatmaybetheirspecial

natures，isnotlessincomprehensibleinrespectoftheunityorduality

ofitsaction，thaninallotherrespects。Arephenomenaduetothevariously—conditioned

workingsofasingleforce，oraretheyduetotheconflictoftwoforces？

Whethereverythingisexplicableonthehypothesisofuniversalpressure，

whenceso—calledtensionresultsdifferentiallyfrominequalitiesofpressure;

orwhetherthingsaretobeexplainedonthehypothesisofuniversaltension，

fromwhichpressureisadifferentialresult;orwhether，asmostphysicists

hold，pressureandtensioneverywhereco—exist;arequestionswhichitis

impossibletosettle。Eachofthesethreesuppositionsmakesthefactscomprehensible，

onlybypostulatinganinconceivability。Toassumeauniversalpressure，

confessedlyrequiresustoassumeaninfiniteplenum——anunlimitedspace

fullofsomethingwhichiseverywherepressedbysomethingbeyond;andthis

assumptioncannotbementallyrealized。Thatuniversaltensionistheagency，

isanideaopentoaparallelandequallyfatalobjection。Andverballyintelligible

asisthepropositionthatpressureandtensioneverywhereco—exist，yet

wecannottrulyrepresenttoourselvesoneultimateunitofmatterasdrawinganotherwhileresistingit。Nevertheless，thislastbeliefwearecompelledtoentertain。Mattercannot

beconceivedexceptasmanifestingforcesofattractionandrepulsion。In

ourconsciousness，BodyisdistinguishedfromSpacebyitsoppositionto

ourmuscularenergies;andthisoppositionwefeelunderthetwofoldform

ofacohesionwhichhindersoureffortstorend，andaresistancewhichhinders

oureffortstocompress。Withoutresistancetherecanbenothingbutempty

extension。Withoutcohesiontherecanbenoresistance。Probablythisconception

ofantagonisticforcesoriginatesfromtheantagonismofourflexorandextensor

muscles。Butbethisasitmayweareobligedtothinkofallobjectsas

madeupofpartsthatattractandrepeloneanother，sincethisistheformofourexperienceofallobjects。Byahigherabstractionresultstheconceptionofattractiveandrepulsive

forcespervadingspace。Wecannotdissociateforcefromoccupiedextension，

oroccupiedextensionfromforce，becausewehaveneveranimmediateconsciousness

ofeitherintheabsenceoftheother。Nevertheless，wehaveabundantproof

thatforceisexercisedthroughwhatappearstooursensesavacuity。Mentally

torepresentthisexercise，wearehenceobligedtofilltheapparentvacuity

withaspeciesofmatter——anetherealmedium。Theconstitutionweassign

tothisetherealmedium，however，isnecessarilyanabstractoftheimpressions

receivedfromtangiblebodies。Theoppositiontopressurewhichatangible

bodyofferstous，isnotshowninonedirectiononly，butinalldirections;

andsolikewiseisitstenacity。Supposecountlesslinesradiatingfromits

centre，anditresistsalongeachoftheselinesandcoheresalongeachof

theselines。Hencetheconstitutionofthoseultimateunitsthroughtheinstrumentality

ofwhichphenomenaareinterpreted。Betheymoleculesofponderablematter

ormoleculesofether，thepropertiesweconceivethemtopossessarenothing

elsethantheseperceptiblepropertiesidealized。Centresofforceattracting

andrepellingoneanotherinalldirections，aresimplyinsensibleportions

ofmatterhavingtheendowmentscommontosensibleportionsofmatter——

endowmentsofwhichwecannotbyanymentaleffortdivestthem。Inbrief，

theyaretheinvariableelementsoftheconceptionofmatter，abstracted

fromitsvariableelements——size，form，quality，etc。Andsotointerpret

manifestationsofforcewhichcannotbetactuallyexperienced，weusethe

termsofthoughtsuppliedbyourtactualexperiences，andthisforthesufficientreasonthatwemustusetheseornone。###第18章Itneedsscarcelybesaidthattheseuniversallyco—existentforcesof

attractionandrepulsion，mustnotbetakenasrealities，butasoursymbols

ofthereality。TheyaretheformsunderwhichtheworkingsoftheUnknowable

arecognizablebyus——modesoftheUnconditionedaspresentedunderthe

conditionsofourconsciousness。Howtheseideasstandrelatedtotheabsolute

truthwecannotknow，butwemayunreservedlysurrenderourselvestothem

asrelativelytrue，andmayproceedtoevolveaseriesofdeductionshavingalikerelativetruth。§75。Universallyco—existentforcesofattractionandrepulsion，

implycertainlawsofdirectionofallmovement。Whereattractiveforces

aloneareconcerned，orratherarealoneappreciable，movementtakesplace

inthedirectionoftheirresultant;whichmay，inasense，becalledthe

lineofgreatesttraction。Whererepulsiveforcesaloneareconcerned，or

ratherarealoneappreciable，movementtakesplacealongtheirresultant;

whichisusuallyknownasthelineofleastresistance。Andwherebothattractive

andrepulsiveforcesareconcerned，andareappreciable，movementtakesplace

alongtheresultantofthetractionsandresistances。Strictlyspeakingthis

lastisthesolelaw;since，bythehypothesis，bothforcesareeverywhere

inaction。Butveryfrequentlytheonekindofforceissoimmenselyinexcess，

thattheeffectoftheotherkindmaybeleftoutofconsideration。Practically，

wemaysaythatabodyfallingtotheEarthfollowsthelineofgreatest

traction;since，thoughtheresistanceoftheairmust，ifthebodybeirregular，

causesomedivergencefromthisline（quiteperceptiblewithfeathersand

leaves），yet，ordinarilythedivergenceissoslightthatwemaydisregard

it。Inthesamemannerthoughthecoursestakenbysteamfromanexploding

boiler，differsomewhatfromthosewhichitwouldtakeweregravitationout

ofthequestion;yet，asgravitationaffectsitscoursesonlyinfinitesimally，

wearejustifiedinsayingthattheescapingsteamgoesalonglinesofleast

resistance。Motion，then，alwaysfollowsthelineofgreatesttraction，or

thelineofleastresistance，ortheresultantofthetwo;andthoughthe

lastisalonestrictlytrue，theothersareinmanycasessufficientlynearthetruthforpracticalpurposes。Motionsetupinanydirectionisitselfacauseoffurthermotionin

thatdirection，sinceitisthemanifestationofasurplusforceinthat

direction。Thisholdsequallywiththetransitofmatterthroughspace，the

transitofmatterthroughmatter，andthetransitthroughmatterofanykind

ofvibration。Inthecaseofmattermovingthroughspace，thisprinciple

isexpressedinthelawofinertia——alawwhichallthecalculationsof

physicalastronomyassume。Inthecaseofmattermovingthroughmatter，we

tracethesametruthunderthefamiliarexperiencethatanybreachmadeby

onesolidthroughanother，oranychannelformedbyafluidthroughasolid，

becomesaroutealongwhich，otherthingsequal，subsequentmovementsof

likenaturemostreadilytakeplace。Andinthecaseofmotionpassingthrough

matterundertheformofanimpulsecommunicatedfromparttopart，thefacts

ofmagnetizationappeartoimplythattheestablishmentofundulationsalongcertainlines，determinestheircontinuancealongthoselines。Itfurtherfollowsfromtheconditions，thatthedirectionofmovement

canrarelyifeverbeperfectlystraight。Formatterinmotiontopursue

continuouslytheexactlineinwhichitsetsout，theforcesofattraction

andrepulsionmustbesymmetricallydisposedarounditspath;andthechances

againstthisareinfinitelygreat。Itmaybeaddedthatinproportionas

theforcesatworkarenumerousandvaried，thelineamovingbodydescribes

isnecessarilycomplex:witnessthecontrastbetweentheflightofanarrowandthegyrationsofasticktossedaboutbybreakers。Asasteptowardsunificationofknowledge，wehavenowtotracethesegenerallawsthroughoutthevariousordersofchangeswhichtheCosmosexhibits。§76。IntheSolarSystemtheprinciplesthusbrieflysummarizedare

everyinstantexemplified。Eachplanetaidsatellitehasamomentumwhich

would，ifactingalone，carryitforwardinthedirectionitisatanyinstant

pursuing——amomentumwhichwouldmakeastraightlineitslineofleast

resistance。Eachplanetandsatellite，however，isdrawnbyaforcewhich，

ifitactedalone，wouldtakeitinastraightlinetowardsitsprimary。

Andtheresultantofthesetwoforcesisthatcurvewhichitdescribes——

acurveconsequentontheunsymmetricaldistributionoftheforcesaround。

Whenmorecloselyexamined，itspathsuppliesfurtherillustrations。For

itisnotanexactcircleorellipse;whichitwouldbewerethetangential

andcentripetalforcestheonlyonesconcerned。AdjacentmembersoftheSolar

System，evervaryingintheirrelativepositions，causeperturbations;that

is，slightdivergencesfromthatcircleorellipsewhichthetwochiefforces

wouldproduce。Theseperturbationsseverallyshowusinminordegrees，how

thelineofmovementistheresultantofalltheforcesengaged;andhowthislinebecomesmorecomplicatedinproportionastheforcesaremultiplied。Ifinsteadofthemotionsoftheplanetsandsatellitesaswholes，we

considerthemotionsoftheirparts，wemeetwithcomparativelycomplexillustrations。

EveryportionoftheEarth\'ssubstanceinitsdailyrotation;describesa

curvewhichisinthemainaresultantofthatresistancewhichchecksits

nearerapproachtothecentreofgravity，thatmomentumwhichwouldcarry

itoffatatangent，andthoseforcesofgravitationandcohesionwhichkeep

itfrombeingsocarriedoff。Whenwiththisaxialmotioniscontemplated

theorbitalmotion，thecourseofeachpartisseentobeamuchmoreinvolved

one。Andwefindittohaveastillgreatercomplicationontakingintoaccount

thatlunarattractionwhichmainlyproducesthetidesandtheprecessionoftheequinoxes。§77。Wecomenexttoterrestrialchanges:presentonesasobserved，

andpastonesasinferredbygeologists。Letussetoutwiththeunceasing

movementsintheEarth\'satmosphere;descendtotheslowalterationsinprogressonitssurface;andthentothestillsloweronesgoingonbeneath。MassesofairabsorbingheatfromsurfaceswarmedbytheSun，expand，

andascend:theresistancebeinglessthantheresistancetolateralmovement。

Adjacentatmosphericmasses，movinginthedirectionsofthediminishedresistance，

displacetheexpandedair。When，again，bytheascentofheatedairfrom

greattractslikethetorridzone，thereisproducedattheuppersurface

oftheatmosphereaprotuberance——whentheairformingthisprotuberance

overflowslaterallytowardsthepoles;itdoessobecause，whilethetractive

forceoftheEarthisnearlythesame，thelateralresistanceisdiminished。

Andthroughoutthecourseofeachcurrentthusgenerated，aswellasthroughout

thecourseofeachcounter—currentflowingintothespacevacated，thedirection

isalwaystheresultantoftheEarth\'stractiveforceandtheresistance

offeredbythesurroundingmassesofair:modifiedonlybyconflictwith

othercurrentssimilarlygenerated，andbycollisionwithprominenceson

theEarth\'scrust。Themovementsofwater，inbothitsgaseousandliquid

states，furnishfurtherexamples。Evaporationistheescapeofparticles

ofwaterinthedirectionofleastresistance;andastheresistance（which

isduetogaseouspressure）diminishes，theevaporationincreases。Onthe

otherhandcondensation，whichtakesplacewhenanyportionofatmospheric

vapourhasitstemperaturemuchlowered，maybeinterpretedasadiminution

ofthemutualpressureamongthecondensingparticles，whilethepressure

ofsurroundingparticlesremainsthesame;andsoisamotiontakingplace

inthedirectionoflessenedresistance。Inthecoursefollowedbytheresulting

raindrops，wehaveoneofthesimplestinstancesofthejointeffectofthe

twoantagonistforces。TheEarth\'sattraction，andtheresistanceofatmospheric

currentsevervaryingindirectionandintensity，giveastheirresultants，

lineswhichinclinetothehorizonincountlessdifferentdegreesandundergo

perpetualvariations。Inthecoursetherain—dropstakewhiletricklingover

thesurface，ineveryrill，ineverylargerstream，andineveryriver，we

seethemdescendingasstraightastheantagonismofsurroundingobjects

permits。Sofarfromacascadefurnishinganexception，itfurnishesbut

anotherillustration。Forthoughallsolidobstaclestoaverticalfallof

thewaterareremoved，yetthewater\'shorizontalmomentumisanobstacle;

andtheparabolainwhichthestreamleapsfromtheprojectingledgeisgeneratedbythecombinedgravitationandmomentum。TheEarth\'ssolidcrustundergoeschangeswhichsupplyanothergroupof

illustrations。Thedenudationoflandsandthedepositingoftheremoved

sedimentinnewstrataatthebottomsofseasandlakes，isaprocessthroughout

whichmotionisobviouslydeterminedinthesamewayasisthatofthewater

effectingthetransport。Again，thoughwehavenodirectinductiveproof

thattheforcesclassedasigneousexpendthemselvesalonglinesofleast

resistance，yetwhatlittleweknowofthemisinharmonywiththebelief

thattheydoso。Earthquakescontinuallyrevisitthesamelocalities，and

specialtractsundergoforlongperiodstogethersuccessiveelevationsor

subsidences:factswhichimplythatalready—fracturedportionsoftheEarth\'s

crustarethosemostpronetoyieldunderthepressurecausedbyfurther

contractions。Thedistributionofvolcanoesalongcertainlines，aswell

asthefrequentrecurrenceoferuptionsfromthesamevents，arefactsoflikemeaning。§78。Thatorganicgrowthtakesplaceinthedirectionofleastresistance，

isapropositionsetforthandillustratedbyMr。JamesHinton，intheMedico—Chirurgical

ReviewforOctober，1858。Afterdetailingafewoftheearlyobservations

whichledhimtothisgeneralization，heformu1atesitthus:——

"Organicformistheresultofmotion。"

"Motiontakesthedirectionofleastresistance。""Thereforeorganicformistheresultofmotioninthedirectionofleastresistance。"Afteranelucidationanddefenceofthisposition，Mr。Hintonproceeds

tointerpret，inconformitywithit，sundryphenomenaofdevelopment。Shakingofplants，hesays:——"Theformationoftherootfurnishesabeautifulillustrationof

thelawofleastresistance，foritgrowsbyinsinuatingitself，cellby

cell，throughtheintersticesofthesoil;itisbysuchminuteadditions

thatitincreases，windingandtwistingwhithersoevertheobstaclesitmeets

initspathdetermine，andgrowingtheremost，wherethenutritivematerials

areaddedtoitmostabundantly。Aswelookontherootsofamightytree，

itappearstousasiftheyhadforcedthemselveswithgiantviolenceinto

thesolidearth。Butitisnotso;theywereledongentlycelladdedto

cell，softlyasthedewsdescended，andtheloosenedearthmadeway。Once

formed，indeed，theyexpandwithanenormouspower，butthespongycondition

ofthegrowingradiclesutterlyforbidsthesuppositionthattheyareforced

intotheearth。Isitnotprobable，indeed，thattheenlargementoftheroots

alreadyformedmaycrackthesurroundingsoil，andhelptomaketheintersticesintowhichthenewrootletsgrow？***"Throughoutalmostthewholeoforganicnaturethespiralformis

moreorlessdistinctlymarked。Now，motionunderresistancetakesaspiral

direction，beseenbythemotionofabodyrisingorfallingthroughwater。

Abubblerisingrapidlyinwaterdescribesaspiralcloselyresemblinga

corkscrew，andabodyofmoderatespecificgravitydroppedintowatermay

beseentofallinacurveddirection，thespiraltendencyofwhichmaybe

distinctlyobserved。***Inthisprevailingspiralformoforganicbodies，

therefore，itappearstome，thatthereispresentedastrongprimafacie

casefortheviewIhavemaintained。***Thespiralformofthebranches

ofmanytreesisveryapparent，andtheuniversallyspiralarrangementof

theleavesaroundthestemofplantsneedsonlytobereferredto。***

Theheartcommencesasaspiralturn，andinitsperfectformamanifest

spiralmaybetracedthroughtheleftventricle，rightventricle，rightauricle，

leftauricle，andappendix。Andwhatisthespiralturninwhichtheheart

commencesbutanecessaryresultofthelengthening，underalimit，ofthecellularmassofwhichitthenconsists？***"Everyonemusthavenoticedthepeculiarcurlingupoftheyoung

leavesofthecommonfern。Theappearanceisasiftheleafwererolledup，

butintruththisformismerelyaphenomenonofgrowth。Thecurvatureresults

fromtheincreaseoftheleaf，itisonlyanotherformofthewrinklingup，orturningatrightanglesbyextensionunderlimit。"Therollinguporimbricationofthepetalsinmanyflower—buds

isasimilarthing;atanearlyperiodthesmallpetalsmaybeseenlying

sidebyside;afterwardsgrowingwithinthecapsule，theybecomefoldedroundoneanother。***"Ifaflower—budbeopenedatasufficientlyearlyperiod，thestamens

willbefoundasifmouldedinthecavitybetweenthepistilandthecorolla，

whichcavitytheanthersexactlyfill;thestalkslengthenatanafterperiod。

Ihavenoticedalsoinafewinstances，thatinthoseflowersinwhichthe

petalsareimbricated，ortwistedtogether，thepistilistaperingasgrowing

upbetweenthepetals;insomeflowerswhichhavethepetalssoarranged

inthebudastoformadome（asthehawthorn;e。g。），thepistilisflattened

attheapex，andinthebudoccupiesaspacepreciselylimitedbythestamens

below，andtheenclosingpetalsaboveandatthesides。Ihavenot，however，satisfiedmyselfthatthisholdsgoodinallcases。"WithoutendorsingallMr。Hinton\'sillustrations，hisconclusionmaybe

acceptedasalargeinstalmentofthetruth。Butinthecaseoforganicgrowth，

asinallothercases，thelineofmovementisinstrictnesstheresultant

oftractiveandresistantforces;andthetractiveforceshereformsoconsiderable

anelementthattheformulaisnotcompletewithoutthem。Theshapesofplants

aremanifestlymodifiedbygravitation。Thedirectionofeachbranchisnot

whatitwouldhavebeenintheabsenceofthepullexercisedbytheEarth;

andeveryflowerandleafissomewhatalteredinthecourseofdevelopment

bytheweightofitsparts。Thoughinanimalssucheffectsarelessconspicuous，

yettheinstancesinwhichflexibleorganshavetheirdirectionsingreat

measuredeterminedbygravity，justifytheassertionthatthroughoutthewholeorganismtheformsofpartsmustbeaffectedbythisforce。Theorganicmovementswhichconstitutegrowth，arenot，however，theonly

organicmovementstobeinterpreted。Therearealsothosewhichconstitute

function;andthroughoutthesethesamegeneralprinciplesarediscernible。

Thatthevesselsandductsalongwhichblood，lymph，bile，andallthesecretions，

findtheirways，arechannelsofleastresistance，isanillustrationalmost

tooconspicuoustobenamed。Lessconspicuous，however，isthetruththat

thecurrentssettingalongthesevesselsareaffectedbythetractiveforce

oftheEarth;witnessvaricoseveins;witnesstherelieftoaninflamedpart

obtainedbyraisingit;witnessthecongestionofheadandfaceproduced

bystooping。Andinthefactsthatdropsyinthelegsgetsgreaterbyday

anddecreasesatnight，while，converselythatoedematousfullnessunder

theeyescommonindebility，growsworseduringthehoursofrecliningand

decreasesaftergettingup，weseehowthetransudationofliquidthrough

thewallsofthecapillaries，variesaccordingaschangeofpositionchangestheeffectofgravityindifferentpartsofthebody。Itmaybewelljusttonotethebearingoftheprincipleonthedevelopment

ofspecies。Fromadynamicpointofview，"naturalselection"implies

structuralchangesalonglinesofleastresistance。Themultiplicationof

anykindofplantoranimalinlocalitiesthatarefavourabletoit，isa

growthwheretheantagonisticforcesarelessthanelsewhere。Andthepreservation

ofvarietieswhichsucceedbetterthantheiralliesincopingwithsurrounding

conditions，isthecontinuanceofvitalmovementsinthosedirectionswheretheobstaclestothemaremosteluded。§79。Throughoutmentalphenomenathelawenunciatedisnotreadily

established。Inalargepartofthem，asthoseofthoughtandemotion，there

isnoperceptiblemovement。Eveninsensationandaction，whichshowusin

onepartofthebodyaneffectproducedbyaforceappliedtoanotherpart，

theintermediatemovementisinferentialonly。Somesuggestionsmaybemadehowever。Astimulationimpliesaforceaddedto，orevolvedin，thatpartofthe

organismwhichisitsseat;whileamechanicalmovementimpliesanexpenditure

orlossofforceinthatpartoftheorganismwhichisitsseat:implying

sometensionofmolecularstatebetweenthetwolocalities。Henceif，in

thelifeofaminuteanimal，therearecircumstancesinvolvingthatastimulation

inoneparticularplaceishabituallyfollowedbyacontractioninanother

particularplace——ifthereisthusarepeatedmotionthroughsomeline

ofleastresistancebetweentheseplaces;whatmustbetheresultasrespects

theline？Ifthisline——thischannel——isaffectedbythedischarge——

iftheobstructiveactionofthetissuestraversed，involvesanyreaction。

uponthem，deductingfromtheirobstructivepower;thenasubsequentmotion

betweenthesetwopointswillmeetwithlessresistancealongthischannel

thanthepreviousmotionmetwith，andwillconsequentlytakethischannel

stillmoredecidedly。Everyrepetitionwillfurtherdiminishtheresistance

offered;andthuswillgraduallybeformedapermanentlineofcommunication，

differinggreatlyfromthesurroundingtissueinrespectoftheeasewith

whichforcetraversesit。Henceinsmallcreaturesmayresultrudimentary

nervousconnexions。Onlyanadumbrationofnervousprocessesthushinted

asconformingtothegenerallaw，isherepossible。Buttheeffectsofassociations

betweenimpressionsandmotionsasseeninhabits，allyieldillustrations。

Inknitting，inreadingaloud，intheperformanceoftheskilledpianist

whotalkswhileheplays，wehaveexamplesofthewayinwhichchannelsof

nervouscommunicationareeventuallymadesopermeablebyperpetualdischarges

alongthemastobringaboutastatealmostautomaticorreflex:illustrating

atoncethefactthatmolecularmotionfollowslinesofleastresistance，

andthefactthatmotionalongsuchlines，bydiminishingtheresistance，

furtherfacilitatesthemotion。Thoughqualificationsarisinginthesame

mannerasthoseindicatedinthelastchaptercomplicatethesenervo—motor

processesinwayswhichcannotherebefollowed，theydonotconflictwith

thelawsetforth。Moreovertheyarecongruouswiththeprinciplethatin

proportiontothefrequencywithwhichanyexternalconnexionofphenomena

isexperienced，willbethestrengthoftheansweringinternalconnexion

ofnervousstates。Inthiswaywillarisealldegreesofcohesionamongnervous

states，astherearealldegreesofcommonnessamongthesurroundingco—existences

andsequencesthatgeneratethem。Whencemustresultageneralcorrespondencebetweenassociatedideasandassociatedactionsintheenvironment。（*）

setforthintheMedico—ChirurgicalReviewforJanuary，1859（pp。

189and190）;andcontainsthegermoftheintendedfifthpartofthePrinciples

ofPsychology，whichwaswithheldforreasonsgivenintheprefacetothatwork。>Therelationbetweenemotionsandactionsmaybesimilarlyconstrued。

Observewhathappenswithemotionswhichareundirectedbyvolitions。As

waspointedoutinthelastchapter，thereresultmovementsoftheinvoluntary

andvoluntarymuscles，thataregreatinproportionastheemotionsarestrong。

Itremainsheretoaddthattheorderinwhichthesemusclesareaffected

conformstotheprinciple。Apleasurableorpainfulfeelingofbutslight

intensitydoeslittlemorethanincreasetheactionoftheheart。Why？For

thereasonthattherelationbetweennervousexcitementandcardiaccontraction，

beingcommontoeveryspeciesoffeeling，istheoneofmostfrequentrepetition;

thathencethenervousconnexionofferingtheleastresistancetoadischarge，

istheonealongwhichafeebleforceproducesmotion。Astrongersentiment

affectsnotonlytheheartbutthemusclesoftheface，andespeciallythose

aroundthemouth。Herethelikeexplanationapplies;sincethesemuscles，

beingbothcomparativelysmalland，forpurposesofspeech，perpetuallyused，

offerlessresistancethanothervoluntarymusclestothenervo—motorforces。

Byafurtherincreaseofemotiontherespiratoryandvocalmusclesbecome

perceptiblyexcited。Finally，underviolentpassion，themusclesofthetrunk

andlimbsarestronglycontracted。Thesingleinstanceoflaughter，which

isanundirecteddischargeoffeelingthataffectsfirstthemusclesround

themouth，thenthoseofthevocalandrespiratoryapparatus，thenthose

ofthelimbs，andthenthoseofthespine;sufficestoshowthatwhenno

specialrouteisopenedforit，aforceevolvedinthenervouscentresproduces

motionalongchannelswhichoffertheleastresistance，andifistoogreat

toescapebythese，producesmotionalongchannelsofferingsuccessivelygreaterresistance。*<*Fordetailsseeapaperon"ThePhysiologyofLaughter，"publishedinMacmillan\'sMagazineforMarch，1860，andreprintedinEssays，vol。II。>Probablyitwillbethoughtimpossibletoextendthisreasoningsoas

toincludevoluntaryacts。Yetwearenotwithoutevidencethatthetransition

fromspecialdesirestospecialmuscularmotions，conformstothesameprinciple。

Thementalantecedentsofavoluntarymovement，aresuchastemporarilymake

thelinethroughwhichthismovementisinitiated，thelineofleastresistance。

Foravolition，suggestedasitisbysomepreviousthoughtjoinedwithit

byassociationsthatdeterminethetransition，isitselfarepresentation

ofthemovementswhicharewilled，andoftheirsequences。Buttorepresent

inconsciousnesscertainofourownmovements，ispartiallytoarousethe

sensationsaccompanyingsuchmovements，inclusiveofthoseofmusculartension

——ispartiallytoexcitetheappropriatemotor—nervesandalltheother

nervesimplicated。Thatistosay，thevolitionisitselfanincipientdischarge

alongalinewhichpreviousexperienceshaverenderedalineofleastresistance。Andthepassingofvolitionintoactionissimplyacompletionofthedischarge。###第19章Onecorollarymustbenoted;namelythattheparticularsetofmovements

bywhichanobjectofdesireisreached，areusuallymovementsimplyingthe

smallesttotalofforcestobeovercome。Asthemotioninitiatedbyeach

feelingtakesthelineofleastresistance，itisinferablethatagroup

offeelingsconstitutingamoreorlesscomplexdesirewillinitiatemotions

alongaseriesoflinesofleastresistance;thatis，thedesiredendwill

beachievedwiththesmallesteffort。Doubtlessthroughwantofknowledge

orwantofskillorwantofresolutiontomakeimmediateexertion，aman

oftentakesthemorelaboriousoftwocourses。Butitremainstruethatrelatively

tohismentalstateatthetime，hiscourseistheeasiesttohim——theoneleastresistedbytheaggregateofhisfeelings。§80。Aswithindividualmensoisitwithaggregationsofmen。Social

changestakedirectionsthatareduetothejointactionsofcitizens，determinedasarethoseofallotherchangeswroughtbycompositionofforces。Thuswhenwenotethedirectionofanation\'sgrowth，wefindittobe

thatinwhichtheaggregateofopposingforcesisleast。Itsunitshaveenergies

tobeexpendedinself—maintenanceandreproduction。Theseenergiesaremet

byvariousantagonisticenergies——thoseofgeologicorigin，thoseofclimate，

ofwildanimals，ofotherhumanraceswithwhomthereisenmityorcompetition。

Andthetractsthesocietyspreadsover，arethoseinwhichthereisthe

smallesttotalofantagonismswhiletheyyieldthebestsupplyoffoodand

othermaterialswhichfurtherthegenesisofenergies。Forthesereasons

ithappensthatfertilevalleyswherewaterandvegetalproductsabound，

areearlypeopled。Sea—shores，too，supplyingmucheasily—gatheredfood，

arelinesalongwhichmankindhavecommonlyspread。Thegeneralfactthat，

sofaraswecanjudgefromthetracesleftbythem，largesocietiesfirst

appearedinthosewarmregionswherethefruitsoftheearthareobtainable

withcomparativelylittleexertion，andwherethecostofmaintainingbodily

heatisbutslight，isafactoflikemeaning。Andtotheseinstancesmay

beaddedthealliedonedailyfurnishedbyemigration，whichweseegoing

ontowardscountriespresentingthefewestobstaclestotheself—preservation

ofindividuals，andthereforetonationalgrowth。Similarlywiththatresistance

tothemovementsofasocietywhichneighbouringsocietiesoffer。Eachof

thetribesornationsinhabitinganyregion，increasesinnumbersuntilit

outgrowsitsmeansofsubsistence。Ineachthereisthusaforceeverpressing

outwardsontoadjacentareas——aforceantagonizedbylikeforcesinthe

tribesornationsoccupyingthoseareas。Andthewarsthatresult——the

conquestsofweakertribesornations，andtheoverrunningoftheirterritories

bythevictors，areinstancesofsocialmovementstakingplaceinthedirections

ofleastresistance。Nordotheconqueredpeoples，whentheyescapeextermination

orenslavement，failtoshowusmovementswhicharesimilarlydetermined。

For，migratingastheydotolessfertileregions——takingrefugeindeserts

oramongmountains——movingindirectionswheretheresistancestosocial

growtharecomparativelygreat;theystilldothisonlyunderanexcessof

pressureinallotherdirections:thephysicalobstaclestoself—preservation

theyencounter;beingreallylessthantheobstaclesofferedbytheenemiesfromwhomtheyfly。Internalsocialmovementsalsomaybethusinterpreted。Localitiesnaturally

fittedforproducingparticularcommodities——thatis，localitiesinwhich

suchcommoditiesaregotattheleastcostofenergy——thatis，localities

inwhichthedesiresforthesecommoditiesmeetwiththeleastresistance;

becomelocalitiesdevotedtotheobtainmentofthesecommodities。Wheresoil

andclimaterenderwheataprofitablecrop，oracropfromwhichthegreatest

amountoflife—sustainingpowerisgainedbyagivenquantityofeffort，

thegrowthofwheatbecomesadominantindustry。Wherewheatcannotbeeconomically

produced，oats，orrye，ormaize，orpotatoes，orrice，istheagricultural

staple。Alongsea—shoresmensupportthemselveswithleasteffortbycatching

fish，andhencefishingbecomestheoccupation。Andinplaceswhicharerich

incoalormetallicores，thepopulation，findingthatlabourexpendedin

raisingthesematerialsbringsalargerreturnoffoodandclothingthan

whenotherwiseexpended，becomesapopulationofminers。Thislastinstance

introducesustothephenomenaofexchange，whichequallyillustratethe

generallaw。Forthepracticeofbarterbeginsassoonasitfacilitates

thefulfilmentofmen\'sdesires，bydiminishingtheexertionneededtoreach

theobjectsofthosedesires。Wheninsteadofgrowinghisowncorn，weaving

hisowncloth，sewinghisownshoes，eachmanbegantoconfinehimselfto

farming，orweaving，orshoemaking;itwasbecauseeachfounditmorelaborious

tomakeeverythinghewanted，thantomakeagreatquantityofonething

andbarterthesurplusforotherthings。Moreover，indecidingwhatcommodity

toproduce，eachcitizenwas，asheisatthepresentday，guidedinthe

samemanner。Inchoosingthoseformsofactivitywhichtheirspecialcircumstances

andspecialfacultiesdictate，thesocialunitsseverallymovetowardsthe

objectsoftheirdesiresinthedirectionswhichpresenttothemthefewest

obstacles。Theprocessoftransferwhichcommercepresupposes，suppliesanother

seriesofexamples。Solongastheforcestobeovercomeinprocuringany

necessaryoflifeinthedistrictwhereitisconsumed，arelessthanthe

forcestobeovercomeinprocuringitfromanadjacentdistrict，exchange

doesnottakeplace。Butwhentheadjacentdistrictproducesitwithaneconomy

thatisnotoutbalancedbycostoftransit——whenthedistanceissosmall

andtheroutesoeasythatthelabourofconveyanceplusthelabourofproduction

islessthanthelabourofproductionintheconsumingdistrict，transfer

commences。Movementinthedirectionofleastresistanceisalsoseenin

theestablishmentofthechannelsalongwhichintercoursetakesplace。At

theoutset，whengoodsarecarriedonthebacksofmenandhorses，thepaths

chosenarethosewhichcombineshortnesswithlevelnessandfreedomfrom

obstacles——thosewhichareachievedwiththesmallestexertion。Andin

thesubsequentformationofeachhighway，thecoursetakenisthatwhich

deviateshorizontallyfromastraightlinesofaronlyasisneedfultoavoid

verticaldeviationsentailinggreaterlabourindraught。Thesmallesttotal

ofobstructiveforcesdeterminestheroute，eveninseeminglyexceptional

cases;aswhereadetourismadetoavoidtheoppositionofalandowner。

Allsubsequentimprovements，endinginmacadamizedroads，canals，andrailways，

whichreducetheantagonismoffrictionandgravitytoaminimum，exemplify

thesametruth。Aftertherecomestobeachoiceofroadsbetweenonepoint

andanother，westillseethattheroadchosenisthatalongwhichthecost

oftransitistheleast:costbeingthemeasureofresistance。Whenthere

arisesamarkedlocalizationofindustries，therelativegrowthsofthepopulations

devotedtothemmaybeinterpretedonthesameprinciple。Theinfluxofpeople

toeachindustrialcentreisdeterminedbythepaymentforlabour——that

is，bythequantityofcommoditieswhichagivenamountofeffortwillobtain。

Tosaythatartisansflocktoplaceswhere，inconsequenceoffacilities

forproduction，anextraproportionofproducecanbegivenintheshape

ofwages，istosaythattheyflocktoplaceswheretherearethesmallest

obstaclestotheSupportofthemselvesandfamilies;andsogrowthofthesocialorganismtakesplacewheretheresistanceisleast。Noristhelawlessclearlytobetracedinthosefunctionalchangesdaily

goingon。Theflowofcapitalintobusinessesyieldingthelargestreturns，

thebuyinginthecheapestmarketandsellinginthedearest，theintroduction

ofmoreeconomicalmodesofmanufacture，thedevelopmentofbetteragencies

fordistribution，exhibitmovementstakingplaceindirectionswherethey

aremetbythesmallesttotalsofopposingforces。Forifweanalyzeeach

ofthesechanges——ifinsteadofinterestoncapitalwereadsurplusof

productswhichremainsaftermaintenanceoflabourers——ifwethusinterpret

largeinterestorlargesurplustoimplylabourexpendedwiththegreatest

results——andiflabourexpendedwiththegreatestresultsmeansmuscular

actionsodirectedastoevadeobstaclesasfaraspossible;weseethat

allthesecommercialphenomenaimplycomplicatedmotionssetupalonglinesofleastresistance。Socialmovementsofthesevariousordersseverallyconformtothetwo

derivativeprinciplesnamedattheoutset。Inthefirstplaceweseethat，

oncesetupingivendirections，suchmovements，likeallothers，tendto

producecontinuanceinthesedirections。Acommercialmaniaorpanic，acurrent

ofcommodities，asocialcustom，apoliticalagitation，orapopulardelusion，

maintainsitscourselongafteritsoriginalcausehasceased，andrequires

antagonisticforcestoarrestit。Inthesecondplaceitistobenotedthat

inproportiontothecomplexityofsocialforcesisthetortuousnessofsocial

movements。Theinvolvedseriesofvariousprocessesthroughwhichamanis

returnedtoParliament，orthroughwhichafterwards，byanActhefinallygetspassed，certaindoingsofhisfellow—citizensarechanged，showthis。§81。Andnowofthegeneraltruthabovesetforthwhatisourultimate

evidence？Mustweacceptitsimplyasanempiricalgeneralization？ormay

itbeestablishedasacorollaryfromastilldeepertruth？Thereaderwillanticipatetheanswer。Supposeseveraltractiveforces，variouslydirected，tobeactingona

givenbody。Bywhatisknownasthecompositionofforces，theremaybefound

foranytwoofthese，asingleforceofsuchamountanddirectionastoproduce

onthebodyanexactlyequaleffect。Sucharesultantforce，asitiscalled，

maybefoundforanypairofforcesthroughoutthegroup。Similarly，for

anypairofresultantsasingleresultantmaybefound。Andbyrepeating

thiscourse，allofthemmaybereducedtotwo。Ifthesetwoareequaland

opposite——thatis，ifthereisnolineofgreatesttraction，motiondoes

notarise。Iftheyareoppositebutnotequal，motionarisesinthedirection

ofthegreater。Iftheyareneitherequalnoropposite，motionarisesin

thedirectionoftheirresultant。Forineitherofthesecasesthereisan

unantagonizedforceinonedirection。Andthisresiduaryforcemustmove

thebodyinthedirectioninwhichitisacting。Toassertthecontraryis

toassertthataforcecanbeexpendedwithouteffect;andthisinvolves

adenialofthepersistenceofforce。Ifinplaceoftractionswetakeresistances，

theargumentequallyholds;anditholdsalsowherebothtractionsandresistances

areconcerned。Thusthelawthatmotionfollowsthelineofgreatesttraction，

orthelineofleastresistance，ortheresultantofthetwo，isanecessarydeductionfromthatprimordialtruthwhichtranscendsproof。Reducethepropositiontoitssimplestform，anditstruthbecomesstill

moreobvious。Supposetwoweightssuspendedoverapulley，orsupposetwo

menpullingagainsteachother。Theheavierweightwilldescend，andthe

strongermanwilldrawtheweakertowardshim。Ifaskedhowweknowwhich

istheheavierweightorthestrongerman，wecanonlyreplythatitisthe

oneproducingmotioninthedirectionofitspull。Butifoftwoopposing

tractionswecanknowoneasgreaterthantheotheronlybythemotionit

generatesinitsowndirection，thentheassertionthatmotionoccursin

thedirectionofgreatesttractionisatruism。When，goingastepfurther

back，weseekawarrantfortheassumptionthatofthetwoconflictingforces，

theonewhichproducesmotioninitsowndirectionisthegreatest，wefind

nootherthantheconsciousnessthatsuchpartofthegreaterforceasis

unneutralizedbythelesser，mustproduceitseffect——theconsciousness

thatthisresiduaryforcecannotdisappear，butmustmanifestitselfinsome

equivalentchange——theconsciousnessthatforceispersistent。Heretoo，

asbefore，itmayberemarkedthatnonumberofvariedillustrations，like

thoseofwhichthischaptermainlyconsists，cangivegreatercertaintyto

theconclusionthusimmediatelydrawnfromtheultimatedatumofconsciousness。

Forinallcases，asinthesimpleonesjustgiven，wecanidentifythegreatestforceonlybytheresultingmotion。Fromthissameprimordialtruth，too，maybededucedtheprinciplethat

motiononcesetupalonganyline，becomesitselfacauseofsubsequentmotion

alongthatline。Themechanicalaxiomthat，iflefttoitself，mattermoving

inanydirectionwillcontinueinthatdirectionwithundiminishedvelocity，

isbutanindirectassertionofthepersistenceofthatkindofforcecalled

energy;sinceitisanassertionthattheenergymanifestedinthetransfer

ofabodyalongacertainlengthofacertainlineinacertaintime，cannot

disappearwithoutproducingsomeequalmanifestation:amanifestationwhich，

intheabsenceofconflictingforces，mustbeafurthertransferinthesame

directionatthesamevelocity。Inthecaseofmattertraversingmattera

likeinferenceisnecessitated。Herehowevertheactionsarecomplicated。

Aliquidthatfollowsacertainchannelthroughoroverasolid，aswater

alongtheEarth\'ssurface，losespartofitsmotionintheshapeofheat，

throughfrictionandcollisionwiththemattersformingitsbed。Afurther

amountmaybeabsorbedinovercomingtheforcesitliberates;aswhenit

loosensamasswhichfallsintoitschannel。Butafterthesedeductions，

anyfurtherdeductionfromtheenergyembodiedinthemotionofthewater，

isattheexpenseofareactiononthechannelwhichdiminishesitsobstructive

power:suchreactionbeingshowninthemotionacquiredbythedetachedportions

carriedaway。Thecuttingoutofriver—coursesperpetuallyillustratesthis

truth。Stillmoreinvolvedisthecaseofmotionpassingthroughmatterby

impulsefromparttopart;asanervousdischargethroughanimaltissue。

Thereareconceivableanomalies。Somechemicalchangewroughtalongtheroute

traversed，mayrenderitlessfitthanbeforeforconveyingacurrent。Or

someobstructiveformofforcemaybegenerated;asinmetals，theconducting

powerofwhichis，forthetime，decreasedbytheheatwhichtheelectric

currentproduces。Therealquestionis，however，whatstructuralmodification，

ifany，isproducedthroughoutthemattertraversed，apartfromincidental

disturbingforces——apartfromeverythingbutthenecessaryresistanceof

thematter:that，namelywhichresultsfromtheinertiaofitsunits。If

weconfineourattentiontothatpartofthemotionwhich，escapingtransformation，

continuesitscourse，thenthepersistenceofforcenecessitatesthatas

muchofitasistakenupinchangingthepositionsoftheunits，mustleavethesebysomuchlessabletoobstructsubsequentmotioninthesamedirection。ThusinallthechangesdisplayedbytheSolarSystem，inallthosewhich

aregoingonintheEarth\'scrust，inallprocessesoforganicdevelopment

andfunction，inallmentalactionsandtheeffectstheyworkonthebody，

andinallmodificationsofstructureandactivityinsocieties，theimplied

movementsareofnecessitydeterminedinthemannerabovesetforth。The

truthsetforthholdsnotonlyofoneclass，orofsomeclasses，ofphenomena，

butitisamongthoseuniversaltruthsbywhichourknowledgeofphenomena

ingeneralisunified。

Chapter10TheRhythmofMotion§82。Whenthepennantofavessellyingbecalmedshowsthecoming

breeze，itdoessobygentleundulationswhichtravelfromitsfixedtoits

freeend。Presentlythesailsbegintoflap;andtheirblowsagainstthe

mastincreaseinrapidityasthebreezerises。Evenwhen，beingfullybellied

out，theyareingreatpartsteadiedbythestrainoftheyardsandcordage，

theirfreeedgestremblewitheachstrongergust。Andshouldtherecomea

gale，thejarthatisfeltonlayingholdoftheshroudsshowsthattherigging

vibrates;whilethewhistleofthewindprovesthatinit，also，rapidundulations

aregenerated。Ashoretheconflictbetweenthecurrentofairandthethings

itmeetsresultsinalikerhythmicalaction。Theleavesallshiverinthe

blast;eachbranchoscillates;andeveryexposedtreeswaystoandfro。The

bladesofgrassanddriedbentsinthemeadows，andstillbetterthestalks

intheneighbouringcorn—fields，exhibitthesamerisingandfallingmovements。

Nordothemorestableobjectsfailtodothelike，thoughinalessmanifest

fashion;aswitnesstheshudderthatmaybefeltthroughoutahouseduring

theparoxysmsofaviolentstorm。Streamsofwaterproduceinopposingobjects

thesamegeneraleffectsasdostreamsofair。Submergedweedsgrowingin

themiddleofabrook，undulatefromendtoend。Branchesbroughtdownby

thelastflood，andleftentangledatthebottomwherethecurrentisrapid，

arethrownintoastateofupanddownmovementthatissloworquicktproportion

astheyarelargeorsmall;andwhere，asingreatriversliketheMississippi，

wholetreesarethusheld，thename"sawyers，"bywhichtheyare

locallyknown，sufficientlydescribestherhythmproducedinthem。Note，

again，theeffectoftheantagonismbetweenthecurrentanditschannel。

Inshallowplaces，wheretheactionofthebottomonthewaterflowingover

itisvisible，weseearippleproduced——aseriesofundulations。Ifwe

studytheactionandreactiongoingonbetweenthemovingfluidanditsbanks，

westillfindtheprincipleillustrated，thoughinadifferentway。Forin

everyrivulet，asinthemapped—outcourseofeverygreatriver，thebends

ofthestreamfromsidetosidethroughoutitstortuouscourseconstitute

alateralundulation——anundulationsoinevitablethatevenanartificially—straightened

channeliseventuallychangedintoaserpentineone。Kindredphenomenamay

beobservedwhenthewaterisstationaryandthesolidmattermoving。Astick

drawnlaterallythroughthewaterwithmuchforce，provesbythethrobwhich

itcommunicatestothehandthatitisinastateofvibration。Evenwhere

themovingbodyismassive，itonlyrequiresthatgreatforceshouldbeapplied

togetasensibleeffectoflikekind:instancethescrewofascrew—steamer

[oftheprimitivetype]，whichinsteadofasmoothrotationfallsintoa

rapidrhythmthatsendsatremorthroughthewholevessel。Thesoundproduced

whenabowisdrawnoveraviolin—string，showsusvibrationsaccompanying

themovementofasolid。Inlathesandplaningmachines，theattempttotake

offathickshavingcausesaviolentjarofthewholeapparatus，andthe

productionofaseriesofwavesontheironorwoodthatiscut。Everyboy

inscrapinghisslate—pencilfindsitscarcelypossibletohelpmakinga

ridgedsurface。Ifyourollaballalongthegroundorovertheice，there

isalwaysmoreorlessupanddownmovement——amovementthatisvisible

whilethevelocityisconsiderable，butbecomestoosmallandrapidtobe

seenbytheunaidedeyeasthevelocitydiminishes。Howeversmooththerails，

andhoweverperfectlybuiltthecarriages，arailway—traininevitablyacquires

oscillations，bothlateralandvertical。Evenwhereamovingmassissuddenly

arrestedbycollision，thelawisstillillustrated;forboththebodystriking

andthebodystruckaremadetotremble;andtremblingisrhythmicalmovement。

Littleaswehabituallyobserveit，itisyetcertainthattheimpulsesour

actionsimpressfrommomenttomomentonsurroundingobjects，arepropagated

throughtheminvibrations。Itneedsbuttolookthroughatelescopeofhigh

power，placedonatable，tobeconvincedthateachpulsationoftheheart

givesajartosurroundingthings。Motionsofanotherorder——thosenamely

oftheetherealmedium——teachusthesamething。Everyfreshdiscovery

confirmsthehypothesisthatlightconsistsofundulations，andthatthe

raysofheathavealikefundamentalnature:theirundulationsdiffering

fromthoseoflightonlyintheircomparativelengths。Nordothemovements

ofelectricityfailtofurnishuswithillustrations;thoughofadifferent

order。Thenorthernauroramayoftenbeobservedtopulsatewithwavesof

greaterbrightness;andtheelectricdischargethroughavacuumshowsby

itsstratifiedappearancethatthecurrentisnotuniform，butcomesingushes

ofgreaterandlesserintensity。Shoulditbesaidthattherearesomemotions，

asthoseofprojectiles，whicharenotrhythmical，thereplyisthatthe

exceptionisapparentonly，andthatthesemotionswouldberhythmicalif

theywerenotinterrupted。Itiscommontoassertthatthetrajectoryof

acannon—ballisaparabola;anditistruethat（omittingatmosphericresistance）

thecurvedescribeddifferssoslightlyfromaparabolathatitmaypractically

beregardedasone。But，strictlyspeaking，itisaportionofanextremely

eccentricellipse，havingtheEarth\'scentreofgravityforitsremoterfocus;

andbutforitsarrestbythesubstanceoftheEarth，thecannon—ballwould

travelroundthatfocusandreturntothepointwhenceitstarted;again

torepeatthisslowrhythm。Indeed，whileseemingtodothereverse，the

dischargeofacannonfurnishesoneofthebestillustrationsoftheprinciple

enunciated。Theexplosionproducesviolentundulationsinthesurrounding

air。Thewhizzoftheshot，asitfliestowardsitsmark，isduetoanother

seriesofatmosphericundulations。AndtheeccentricmovementroundtheEarth\'s

centre，whichthecannon—ballisbeginningtoperform，beingcheckedbysolid

matter，istransformedintoarhythmofanotherorder;namely，thevibration

whichtheblowsendsthroughneighbouringbodies。*<*Afterhavingfor

someyearssupposedmyselfaloneinthebeliefthatallmotionisrhythmical，IdiscoveredthatmyfriendProfessorTyndallalsoheldthisdoctrine。>Rhythmisverygenerallynotsimplebutcompound。Thereareusuallyat

workvariousforces，causingundulationsdifferinginrapidity;andhence

besidestheprimaryrhythmstherearisesecondaryrhythms，producedbythe

periodiccoincidenceandoppositionoftheprimaryones。Double，triple，

andevenquadruplerhythms，arethusgenerated。Oneofthesimplestinstances

isaffordedbywhatinacousticsareknownas"beats":recurring

intervalsofsoundandsilencewhichareperceivedwhentwonotesofnearly

thesamepitcharestrucktogetherandwhichareduetothealternatecorrespondence

andantagonismoftheatmosphericwaves。