What，then，istheconductwhichPurityforbidsfortheprincipleismoreeasilydiscussedinitsnegativeaspect？Asthenormalandobviousendofsexualintercourseisthepropagationofthespecies，somehavethoughtthatallindulgenceofappetite，exceptasameanstothisend，shouldbeprohibited。ButthisdoctrinewouldleadtoarestrictionofconjugalintercoursefartoosevereforCommonSense。Shallwesay，then，thatPurityforbidssuchindulgenceexceptundertheconditionsofconjugaluniondefinedbyLaw？Butthisanswer，again，furtherreflectionshowstobeunsatisfactory。For，first，weshouldnot，onconsideration，callaconjugalunionimpure，merelybecausethepartieshadwilfullyomittedtofulfillegalconditions，andhadmadeacontractwhichthelawdeclinedtoenforce。Wemightcondemntheirconduct，butweshouldnotapplytoitthisnotion。And，secondly，wefeelthatpositivelawmaybeunfavourabletoPurity，andthatinfactPurity，likeJustice，issomethingwhichthelawoughttomaintain，butdoesnotalways。Wehavetoask，then，whatkindofsexualrelationswearetocallessentiallyimpure，whethercountenancedornotbyLawandCustom？Thereappeartobenodistinctprinciples，havinganyclaimtoself-evidence，uponwhichthequestioncanbeansweredsoastocommandgeneralassent。Itwouldbedifficulteventostatesuchaprinciplefordeterminingthedegreeofconsanguinitybetweenhusbandandwifewhichconstitutesaunionincestuous；althoughtheaversionwithwhichsuchunionsarecommonlyregardedisapeculiarlyintensemoralsentiment；andthedifficultybecomesindefinitelygreaterwhenweconsidertherationaleofprohibiteddegreesofaffinity。Again，probablyfewwouldstigmatisealegalpolygynousconnexionasimpure，howevertheymightdisapproveofthelawandofthestateofsocietyinwhichsuchalawwasestablished:
butiflegalPolygynyisnotimpure，isPolyandry，whenlegalandcustomary——asisnotunfrequentlythecaseamongthelowerracesofman——tobesocharacterised？
andifnot，onwhatrationalprinciplecanthenotionbeappliedtoinstitutionsandconduct？Again，wheredivorcebymutualconsent，withsubsequentmarriage，islegalised，wedonotcallthisanoffenceagainstPurity:andyetiftheprincipleoffreechangebeonceadmitted，itseemsparadoxicaltodistinguishpurityfromimpuritymerelybylessrapidityoftransition；
andtocondemnasimpureeven`FreeLove’，insofarasitisearnestlyadvocatedasameanstoacompleterharmonyofsentimentbetweenmenandwomen，andnottomeresensuallicense。
Shallwe，then，fallbackuponthepresenceofmutualaffectionasdistinguishedfrommereappetiteasconstitutingtheessenceofpuresexualrelations？Butthis，again，whiletoolaxfromonepointofview，seemsfromanothertoosevereforCommonSense:aswedonotcondemnmarriageswithoutaffectionasimpure，althoughwedisapproveofthemasproductiveofunhappiness。Suchmarriages，indeed，aresometimesstigmatisedas``legalisedprostitution’’，butthephraseisfelttobeextravagantandparadoxical；anditisevendoubtfulwhetherwedodisapproveofthemunderallcircumstances；ase。g。inthecaseofroyalalliances。