SIR，——Theopinionwhich，inyourletterofJanuary24，youarepleasedtoaskofme，onthecomparativemeritsofthedifferentmethodsofclassificationadoptedbydifferentwritersonNaturalHistory，isonewhichIcouldnothavegivensatisfactorily，evenattheearlierperiodatwhichthesubjectwasmorefamiliar；stillless，afteralifeofcontinuedoccupationincivilconcernshassomuchwithdrawnmefromstudiesofthatkind。Ican，therefore，answerbutinaverygeneralway。Andthetextofthisanswerwillbefoundinanobservationinyourletter，where，speakingofnosologicalsystems，yousaythatdiseasehasbeenfoundtobeanunit。Naturehas，intruth，producedunitsonlythroughallherworks。Classes，orders，genera，species，arenotofherwork。Hercreationisofindividuals。Notwoanimalsareexactlyalike；notwoplants，noreventwoleavesorbladesofgrass；notwocrystallizations。Andifwemayventurefromwhatiswithinthecognizanceofsuchorgansasours，toconcludeonthatbeyondtheirpowers，wemustbelievethatnotwoparticlesofmatterareofexactresemblance。Thisinfinitudeofunitsorindividualsbeingfarbeyondthecapacityofourmemory，weareobliged，inaidofthat，todistributethemintomasses，throwingintoeachofthesealltheindividualswhichhaveacertaindegreeofresemblance；tosubdividetheseagainintosmallergroups，accordingtocertainpointsofdissimilitudeobservableinthem，andsoonuntilwehaveformedwhatwecallasystemofclasses，orders，generaandspecies。Indoingthis，wefixarbitrarilyonsuchcharacteristicresemblancesanddifferencesasseemtousmostprominentandinvariableintheseveralsubjects，andmostlikelytotakeastrongholdinourmemories。ThusRayformedoneclassificationonsuchlinesofdivisionasstruckhimmostfavorably；Kleinadoptedanother；Brissonathird，andothernaturalistsotherdesignations，tillLinnaeusappeared。Fortunatelyforscience，heconceivedinthethreekingdomsofnature，modesofclassificationwhichobtainedtheapprobationofthelearnedofallnations。Hissystemwasaccordinglyadoptedbyall，andunitedallinagenerallanguage。Itofferedthethreegreatdesiderata：First，ofaidingthememorytoretainaknowledgeoftheproductionsofnature。Secondly，ofrallyingalltothesamenamesforthesameobjects，sothattheycouldcommunicateunderstandinglyonthem。AndThirdly，ofenablingthem，whenasubjectwasfirstpresented，totraceitbyitscharacteruptotheconventionalnamebywhichitwasagreedtobecalled。Thisclassificationwasindeedliabletotheimperfectionofbringingintothesamegroupindividualswhich，thoughresemblinginthecharacteristicsadoptedbytheauthorforhisclassification，yethavestrongmarksofdissimilitudeinotherrespects。Buttothisobjectioneverymodeofclassificationmustbeliable，becausetheplanofcreationisinscrutabletoourlimitedfaculties。Naturehasnotarrangedherproductionsonasingleanddirectline。Theybranchateverystep，andineverydirection，andhewhoattemptstoreducethemintodepartments，islefttodoitbythelinesofhisownfancy。Theobjectionofbringingtogetherwhataredisparatainnature，liesagainsttheclassificationsofBlumenbachandofCuvier，aswellasthatofLinnaeus，andmustforeverlieagainstall。
　　Perhapsnotinequaldegree；onthisIdonotpronounce。ButneitheristhissoimportantaconsiderationasthatofunitingallnationsunderonelanguageinNaturalHistory。ThishadbeenhappilyeffectedbyLinnaeus，andcanscarcelybehopedforasecondtime。
　　Nothingindeedissodesperateastomakeallmankindagreeingivingupalanguagetheypossess，foronewhichtheyhavetolearn。TheattemptleadsdirectlytotheconfusionofthetonguesofBabel。
　　DisciplesofLinnaeus，ofBlumenbach，andofCuvier，exclusivelypossessingtheirownnomenclatures，cannolongercommunicateintelligiblywithoneanother。Howevermuch，therefore，weareindebtedtoboththesenaturalists，andtoCuvierespecially，forthevaluableadditionstheyhavemadetothesciencesofnature，Icannotsaytheyhaverenderedheraserviceinthisattempttoinnovateinthesettlednomenclatureofherproductions；onthecontrary，Ithinkitwillbeacheckontheprogressofscience，greaterorless，inproportionastheirschemesshallmoreorlessprevail。Theywouldhaverenderedgreaterservicebyholdingfasttothesystemonwhichwehadonceallagreed，andbyinsertingintothatsuchnewgenera，orders，orevenclasses，asnewdiscoveriesshouldcallfor。Theirsystems，too，andespeciallythatofBlumenbach，areliabletotheobjectionofgivingtoomuchintotheprovinceofanatomy。Itmaybesaid，indeed，thatanatomyisapartofnaturalhistory。Inthebroadsenseoftheword，itcertainlyis。Inthatsense，however，itwouldcomprehendallthenaturalsciences，everycreatedthingbeingasubjectofnaturalhistoryinextenso。Butinthesubdivisionsofgeneralscience，ashasbeenobservedintheparticularoneofnaturalhistory，ithasbeennecessarytodrawarbitrarylines，inordertoaccommodateourlimitedviews。Accordingtothese，assoonasthestructureofanynaturalproductionisdestroyedbyart，itceasestobeasubjectofnaturalhistory，andentersintothedomainascribedtochemistry，topharmacy，toanatomy，&c。Linnaeus’methodwasliabletothisobjectionsofarasitrequiredtheaidofanatomicaldissection，asoftheheart，forinstance，toascertaintheplaceofanyanimal，orofachemicalprocessforthatofamineralsubstance。Itwouldcertainlybebettertoadoptasmuchaspossiblesuchexteriorandvisiblecharacteristicsaseverytravelleriscompetenttoobserve，toascertainandtorelate。Butwiththisobjection，lyingbutinasmalldegree，Linnaeus’methodwasreceived，understood，andconventionallysettledamongthelearned，andwasevengettingintocommonuse。Todisturbitthenwasunfortunate。Thenewsystemattemptedinbotany，byJussieu，inmineralogy，byHauiy，aresubjectsofthesameregret，andsoalsotheno-systemofBuffon，thegreatadvocateofindividualisminoppositiontoclassification。HewouldcarryusbacktothedaysandtotheconfusionofAristotleandPliny，giveuptheimprovementsoftwentycenturies，andco-operatewiththeneologistsinrenderingthescienceofonegenerationuselesstothenextbyperpetualchangesofitslanguage。Inbotany，WildenowandPersoonhaveincorporatedintoLinnaeusthenewdiscoveredplants。Idonotknowwhetheranyonehasrenderedusthesameserviceastohisnaturalhistory。Itwouldbeaveryacceptableone。ThematerialsfurnishedbyHumboldt，andthosefromNewHollandparticularly，requiretobedigestedintotheCatholicsystem。Amongthese，theOrnithorhyncusmentionedbyyou，isanamusingexampleoftheanomaliesbywhichnaturesportswithourschemesofclassification。Althoughwithoutmammae，naturalistsareobligedtoplaceitintheclassofmammiferae；andBlumenbach，particularly，arrangesitinhisorderofPalmipedsandtoothlessgenus，withthewalrusandmanatie。InLinnaeus’systemitmightbeinsertedasanewgenusbetweentheanteaterandmanis，intheorderofBruta。Itseems，intruth，tohavestrongerrelationswiththatclassthananyotherintheconstructionoftheheart，itsredandwarmblood，hairyinteguments，inbeingquadrupedandviviparous，andmaywenotsay，inits_toutensemble_，whichBuffonmakeshissoleprincipleofarrangement?Themandible，asyouobserve，woulddrawittowardsthebirds，werenotthischaracteristicoverbalancedbytheweightieronesbeforementioned。ThatoftheCloacaisequivocal，becausealthoughacharacterofbirds，yetsomemammalia，asthebeaverandsloth，havetherectumandurinarypassageterminatingatacommonopening。Itsribsalso，bytheirnumberandstructure，arenearerthoseofthebirdthanofthemammalia。Itispossiblethatfurtheropportunitiesofexaminationmaydiscoverthemammae。ThoseoftheOpossumareasserted，bytheChevalierd’Aboville，fromhisownobservationsonthatanimal，madewhileherewiththeFrencharmy，tobenotdiscoverableuntilpregnancy，andtodisappearassoonastheyoungareweaned。TheDuckbillhasmanyadditionalparticularitieswhichlikenittoothergenera，andsomeentirelypeculiar。Itsdescriptionandhistoryneedsyetfurtherinformation。
　　InwhatIhavesaidonthemethodofclassing，IhavenotatallmeanttoinsinuatethatthatofLinnaeusisintrinsicallypreferabletothoseofBlumenbachandCuvier。IadheretotheLinneanbecauseitissufficientasaground-work，admitsofsupplementaryinsertionsasnewproductionsarediscovered，andmainlybecauseithasgotintosogeneralusethatitwillnotbeeasytodisplaceit，andstilllesstofindanotherwhichshallhavethesamesingularfortuneofobtainingthegeneralconsent。Duringtheattemptweshallbecomeunintelligibletooneanother，andsciencewillbereallyretardedbyeffortstoadvanceitmadebyitsmostfavoritesons。Iamnotmyselfapttobealarmedatinnovationsrecommendedbyreason。Thatdreadbelongstothosewhoseinterestsorprejudicesshrinkfromtheadvanceoftruthandscience。Myreluctanceistogiveupanuniversallanguageofwhichweareinpossession，withoutanassurnaceofgeneralconsenttoreceiveanother。Andthehigherthecharacteroftheauthorsrecommendingit，andthemoreexcellentwhattheyoffer，thegreaterthedangerofproducingschism。
　　Ishouldseemtoneedapologyfortheselongremarkstoyouwhoaresomuchmorerecentinthesestudies，butIfinditinyourparticularrequestandmyownrespectforit，andwiththatbepleasedtoaccepttheassuranceofmyesteemandconsideration。
　　THECENSORSHIPOFBOOKS
　　_ToN。G。Dufief_
　　_Monticello，April19，1814_
　　DEARSIR，——Yourfavorofthe6thinstantisjustreceived，andIshallwithequalwillingnessandtruth，statethedegreeofagencyyouhad，respectingthecopyofM。deBecourt’sbook，whichcametomyhands。Thatgentlemaninformedme，byletter，thathewasabouttopublishavolumeinFrench，”SurlaCreationduMonde，unSystemed’OrganisationPrimitive，”which，itstitlepromisedtobe，eitherageologicalorastronomicalwork。Isubscribed；and，whenpublished，hesentmeacopy；andasyouweremycorrespondentinthebooklineinPhiladelphia，Itookthelibertyofdesiringhimtocallonyoufortheprice，which，heafterwardsinformedme，youweresokindastopayhimforme，being，Ibelieve，twodollars。Butthesolecopywhichcametomewasfromhimselfdirectly，and，asfarasIknow，wasneverseenbyyou。
　　Iamreallymortifiedtobetoldthat，_intheUnitedStatesofAmerica_，afactlikethiscanbecomeasubjectofinquiry，andofcriminalinquirytoo，asanoffenceagainstreligion；thataquestionaboutthesaleofabookcanbecarriedbeforethecivilmagistrate。
　　Isthisthenourfreedomofreligion?andarewetohaveacensorwhoseimprimaturshallsaywhatbooksmaybesold，andwhatwemaybuy?Andwhoisthustodogmatizereligiousopinionsforourcitizens?Whosefootistobethemeasuretowhichoursarealltobecutorstretched?Isapriesttobeourinquisitor，orshallalayman，simpleasourselves，setuphisreasonastheruleforwhatwearetoread，andwhatwemustbelieve?Itisaninsulttoourcitizenstoquestionwhethertheyarerationalbeingsornot，andblasphemyagainstreligiontosupposeitcannotstandthetestoftruthandreason。IfM。deBecourt’sbookbefalseinitsfacts，disprovethem；iffalseinitsreasoning，refuteit。But，forGod’ssake，letusfreelyhearbothsides，ifwechoose。Iknowlittleofitscontents，havingbarelyglancedoverhereandthereapassage，andoverthetableofcontents。Fromthis，theNewtonianphilosophyseemedthechiefobjectofattack，theissueofwhichmightbetrustedtothestrengthofthetwocombatants；Newtoncertainlynotneedingtheauxiliaryarmofthegovernment，andstilllesstheholyauthorofourreligion，astowhatinitconcernshim。Ithoughttheworkwouldbeveryinnocent，andonewhichmightbeconfidedtothereasonofanyman；notlikelytobemuchreadifletalone，but，ifpersecuted，itwillbegenerallyread。EverymanintheUnitedStateswillthinkitadutytobuyacopy，invindicationofhisrighttobuy，andtoreadwhathepleases。IhavebeenjustreadingthenewconstitutionofSpain。Oneofitsfundamentalbasisisexpressedinthesewords：”The_RomanCatholic_religion，theonlytrueone，is，andalwaysshallbe，thatoftheSpanishnation。Thegovernmentprotectsitbywiseandjustlaws，andprohibitstheexerciseofanyotherwhatever。”NowIwishthispresentedtothosewhoquestionwhatyoumaysell，orwemaybuy，witharequesttostrikeoutthewords，”RomanCatholic，”andtoinsertthedenominationoftheirownreligion。Thiswouldascertainthecodeofdogmaswhicheachwishesshoulddomineerovertheopinionsofallothers，andbetaken，liketheSpanishreligion，underthe”protectionofwiseandjustlaws。”Itwouldshewtowhattheywishtoreducethelibertyforwhichonegenerationhassacrificedlifeandhappiness。Itwouldpresentourboastedfreedomofreligionasathingoftheoryonly，andnotofpractice，aswhatwouldbeapoorexchangeforthetheoreticthraldom，butpracticalfreedomofEurope。
　　ButitisimpossiblethatthelawsofPennsylvania，whichsetusthefirstexampleofthewholesomeandhappyeffectsofreligiousfreedom，canpermittheinquisitorialfunctionstobeproposedtotheircourts。Underthemyouaresurelysafe。
　　Atthedateofyoursofthe6th，youhadnotreceivedmineofthe3dinst。，askingacopyofaneditionofNewton’sPrincipia，whichIhadseenadvertised。Whenthecostofthatshallbeknown，itshallbeaddedtothebalanceof$4。93，andincorporatedwithalargerremittanceIhavetomaketoPhiladelphia。Accepttheassuranceofmygreatesteemandrespect。
　　THEMORALSENSE
　　_ToThomasLaw_
　　_PoplarForest，June13，1814_
　　DEARSIR，——ThecopyofyourSecondThoughtsonInstinctiveImpulses，withtheletteraccompanyingit，wasreceivedjustasIwassettingoutonajourneytothisplace，twoorthreedays’distantfromMonticello。Ibroughtitwithmeandreaditwithgreatsatisfaction，andwiththemoreasitcontainedexactlymyowncreedonthefoundationofmoralityinman。Itisreallycuriousthatonaquesionsofundamental，suchavarietyofopinionsshouldhaveprevailedamongmen，andthose，too，ofthemostexemplaryvirtueandfirstorderofunderstanding。ItshowshownecessarywasthecareoftheCreatorinmakingthemoralprinciplesomuchapartofourconstitutionasthatnoerrorsofreasoningorofspeculationmightleadusastrayfromitsobservanceinpractice。Ofallthetheoriesonthisquestion，themostwhimsicalseemstohavebeenthatofWollaston，whoconsiders_truth_asthefoundationofmorality。Thethiefwhostealsyourguineadoeswrongonlyinasmuchasheactsalieinusingyourguineaasifitwerehisown。Truthiscertainlyabranchofmorality，andaveryimportantonetosociety。Butpresentedasitsfoundation，itisasifatreetakenupbytheroots，haditsstemreversedintheair，andoneofitsbranchesplantedintheground。Somehavemadethe_loveofGod_thefoundationofmorality。This，too，isbutabranchofourmoralduties，whicharegenerallydividedintodutiestoGodanddutiestoman。IfwedidagoodactmerelyfromtheloveofGodandabeliefthatitispleasingtoHim，whencearisesthemoralityoftheAtheist?Itisidletosay，assomedo，thatnosuchbeingexists。
　　Wehavethesameevidenceofthefactasofmostofthoseweacton，to-wit：theirownaffirmations，andtheirreasoningsinsupportofthem。Ihaveobserved，indeed，generally，thatwhileinprotestantcountriesthedefectionsfromthePlatonicChristianityofthepriestsistoDeism，incatholiccountriestheyaretoAtheism。
　　Diderot，D’Alembert，D’Holbach，Condorcet，areknowntohavebeenamongthemostvirtuousofmen。Theirvirtue，then，musthavehadsomeotherfoundationthantheloveofGod。
　　The{Tochylon}ofothersisfoundedinadifferentfaculty，thatoftaste，whichisnotevenabranchofmorality。Wehaveindeedaninnatesenseofwhatwecallbeautiful，butthatisexercisedchieflyonsubjectsaddressedtothefancy，whetherthroughtheeyeinvisibleforms，aslandscape，animalfigure，dress，drapery，architecture，thecompositionofcolors，&c。，ortotheimaginationdirectly，asimagery，style，ormeasureinproseorpoetry，orwhateverelseconstitutesthedomainofcriticismortaste，afacultyentirelydistinctfromthemoralone。
　　Self-interest，orratherself-love，or_egoism_，hasbeenmoreplausiblysubstitutedasthebasisofmorality。ButIconsiderourrelationswithothersasconstitutingtheboundariesofmorality。
　　Withourselveswestandonthegroundofidentity，notofrelation，whichlast，requiringtwosubjects，excludesself-loveconfinedtoasingleone。Toourselves，instrictlanguage，wecanowenoduties，obligationrequiringalsotwoparties。Self-love，therefore，isnopartofmorality。Indeeditisexactlyitscounterpart。Itisthesoleantagonistofvirtue，leadingusconstantlybyourpropensitiestoself-gratificationinviolationofourmoraldutiestoothers。
　　Accordingly，itisagainstthisenemythatareerectedthebatteriesofmoralistsandreligionists，astheonlyobstacletothepracticeofmorality。Takefrommanhisselfishpropensities，andhecanhavenothingtoseducehimfromthepracticeofvirtue。Orsubduethosepropensitiesbyeducation，instructionorrestraint，andvirtueremainswithoutacompetitor。Egoism，inabroadersense，hasbeenthuspresentedasthesourceofmoralaction。Ithasbeensaidthatwefeedthehungry，clothethenaked，bindupthewoundsofthemanbeatenbythieves，pouroilandwineintothem，sethimonourownbeastandbringhimtotheinn，becausewereceiveourselvespleasurefromtheseacts。SoHelvetius，oneofthebestmenonearth，andthemostingeniousadvocateofthisprinciple，afterdefining”interest”