Nowourauthorsveryproperlyrefusetocommitthemselvestotheopinionthatmindistheproductofmatter，buttheirargumentneverthelessimpliesthatsomesortofmaterialvehicleisnecessaryforthecontinuanceofmindinafuturestateofexistence。Thismaterialvehicletheyseektosupplyinthetheorywhichconnectsbyinvisiblebondsoftransmittedenergytheperishablematerialbodywithitscounterpartintheworldofether。Thematerialismoftheargumentisindeedpartlyveiledbytheterminologyinwhichthiscounterpartiscalleda“spiritualbody，“butinthisnoveluseorabuseofscripturallanguagethereseemstometobeastrangeconfusionofideas。Bearinmindthatthe“invisibleuniverse“intowhichenergyisconstantlypassingissimplytheluminiferousether，whichourauthors，tosuittherequirementsoftheirhypothesis，havegratuitouslyendowedwithacomplexityandvarietyofstructureanalogoustothatofthevisibleworldofmatter。Theirlanguageisnotalwaysquitesopreciseasonecoulddesire，forwhiletheysometimesspeakoftheetheritselfasthe“unseenuniverse，“theysometimesalludetoaprimordialmediumyetsubtlerinconstitutionandpresumablymoreimmaterial。Hereinliestheconfusion。Whyshouldtheluminiferousether，oranyprimordialmediuminwhichitmayhavebeengenerated，beregardedasinanyway“spiritual“？Greatphysicists，likelesstrainedthinkers，aresometimesliabletobeunconsciouslyinfluencedbyoldassociationsofideaswhich，ostensiblyrepudiated，stilllurkundercoverofthewordsweuse。Ifearthattheoldassociationswhichledtheancientstodescribethesoulasabreathorashadow，andwhichaccountfortheetymologiesofsuchwordsas“ghost“and“spirit，“havehadsomethingtodowiththisspiritualizationoftheinterstellarether。SomesharemayalsohavebeencontributedbythePlatonicnotionofthe“grossness“or“bruteness“oftangiblematter，——anotionwhichhassurvivedinChristiantheology，andwhicheducatedmenofthepresentdayhavebynomeansuniversallyoutgrown。Saveforsomesucholdassociationsasthese，whyshoulditbesupposedthatmatterbecomes“spriritualized“asitdiminishesinapparentsubstantiality？Whyshouldmatterbepronouncedrespectableintheinverseratioofitsdensityorponderability？Whyisadiamondanymorechargeablewith“grossness“thanacubiccentimetreofhydrogen？Obviouslysuchfanciesarepurelyofmythologicparentage。Nowtheluminiferousether，uponwhichourauthorsmakesuchextensivedemands，maybephysically“ethereal“enough，inspiteoftheenormouselasticitywhichleadsProfessorJevonstocharacterizeitas“adamantine“；
butmostassuredlywehavenottheslightestreasonforspeakingofitas“immaterial“or“spiritual。“Thoughweareunabletoweighitinthebalance，weatleastknowitasatransmitterofundulatorymovements，thesizeandshapeofwhichwecanaccuratelymeasure。Itsforce-relationswithponderablematterarenotonlyuniversallyandincessantlymaintained，buttheyhavethatpreciselyquantitativecharacterwhichimpliesanessentialidentitybetweentheinnermostnaturesofthetwosubstances。Wehaveseenreasonforthinkingitprobablethatetherandordinarymatterarealikecomposedofvortex-ringsinaquasi-frictionlessfluid；butwhateverbethefateofthissubtlehypothesis，wemaybesurethatnotheorywilleverbeentertainedinwhichtheanalysisofethershallrequiredifferentsymbolsfromthatofordinarymatter。Inourauthors’
theory，therefore，theputtingonofimmortalityisinnowisethepassagefromamaterialtoaspiritualstate。Itisthepassagefromonekindofmateriallyconditionedstatetoanother。
Thetheorythusappealsdirectlytoourexperiencesofthebehaviourofmatter；andinderivingsolittlesupportasitdoesfromtheseexperiences，itremainsanessentiallyweakspeculation，whateverwemaythinkofitsingenuity。Forsolongasweareaskedtoacceptconclusionsdrawnfromourexperiencesofthematerialworld，wearejustifiedindemandingsomethingmorethanmereunconditionedpossibility。Werequiresomepositiveevidence，beiteversolittleinamount；andnotheorywhichcannotfurnishsuchpositiveevidenceislikelytocarrytoourmindsmuchpracticalconviction。
ThisiswhatImeantbysayingthatthegreatweaknessofthehypothesisherecriticizedliesinitsmaterialisticcharacter。