Inthesamewaydifferentmannersareassignedtothedifferentperiodswhichmarkhumanlife。Inyouthwelookforthatsensibility，gaiety，andvivacitywhichexperienceteachesustoexpectatthatage；andattheextremeoflife，acertaingravityandsedatenessisthecharacterwhichcustomteachesusisbothmostnaturalandmostrespectable。
Butneverthelessitisnecessarynottoexaggeratetheeffectsofcustomandfashiononourmoralsentiments；foritismoreconcerningtheproprietyorimproprietyofparticularusagesthanaboutthingsofthegreatestimportancethattheirin-fluenceismostapttocauseperversionofjudgment。\"Weexpecttruthandjusticefromanoldmanaswellasfromayoung，fromaclergymanaswellasfromanofficer；anditisinmattersofsmallmomentonlythatwelookforthedistinguishingmarksoftheirrespectivecharacters。\"
Nosocietycouldsubsistamomentifcustomcouldexercisesuchperversionoverourmoralsentiments，withregardtothegeneralstyleofconductandbehaviour，asitexerciseswithregardtotheproprietyofparticularusages。UninterruptedcustompreventedthephilosophersofAthensrecognizingtheevilofinfanticide；andtosaythatathingiscommonlydoneisdailyofferedasanapologyforwhatinitselfisthemostunjustandunreasonableconduct。
CHAPTERVI。THEORYOFCONSCIENCEANDDUTY。
ThetheoryofHutcheson，thatthereexistsinmankindaninwardmoralsenseconcernedwiththedirectperceptionofmoralqualitiesinactionsjustasthesenseofhearingorseeingisconcernedwiththedirectperceptionofsoundsorobjects，orthetheoryofShaftesburythatwhatwecallconscienceisaprimaryprincipleofhumannatureirresolubleintootherfacts，isverydifferentfromthetheoryofAdamSmith，whorefersourmoralperceptivitytotheworkingsoftheinstinctofsympathy。