\"Withrespecttoimmortality，nothingshowsme[soclearly]howstrongandalmostinstinctiveabeliefitis，astheconsiderationoftheviewnowheldbymostphysicists，namely，thatthesunwithalltheplanetswillintimegrowtoocoldforlife，unlessindeedsomegreatbodydashesintothesun，andthusgivesitfreshlife。BelievingasIdothatmaninthedistantfuturewillbeafarmoreperfectcreaturethanhenowis，itisanintolerablethoughtthatheandallothersentientbeingsaredoomedtocompleteannihilationaftersuchlong—continuedslowprogress。Tothosewhofullyadmittheimmortalityofthehumansoul，thedestructionofourworldwillnotappearsodreadful。
\"AnothersourceofconvictionintheexistenceofGod，connectedwiththereason，andnotwiththefeelings，impressesmeashavingmuchmoreweight。
Thisfollowsfromtheextremedifficultyorratherimpossibilityofconceivingthisimmenseandwonderfuluniverse，includingmanwithhiscapacityoflookingfarbackwardsandfarintofuturity，astheresultofblindchanceornecessity。WhenthusreflectingIfeelcompelledtolooktoaFirstCausehavinganintelligentmindinsomedegreeanalogoustothatofman;andIdeservetobecalledaTheist。Thisconclusionwasstronginmymindaboutthetime，asfarasIcanremember，whenIwrotethe’OriginofSpecies;’anditissincethattimethatithasverygradually，withmanyfluctuations，becomeweaker。Butthenarisesthedoubt，canthemindofman，whichhas，asIfullybelieve，beendevelopedfromamindaslowasthatpossessedbythelowestanimals，betrustedwhenitdrawssuchgrandconclusions？
\"Icannotpretendtothrowtheleastlightonsuchabstruseproblems。Themysteryofthebeginningofallthingsisinsolublebyus;andIforonemustbecontenttoremainanAgnostic。\"
ThefollowinglettersrepeattosomeextentwhathasbeengivenfromtheAutobiography。Thefirstonerefersto’TheBoundariesofScience，aDialogue，’publishedin’Macmillan’sMagazine，’forJuly1861。]