TheancientpolicyofEuropeendeavouredinthismannertoregulateagriculture，thegreattradeofthecountry，bymaximsquitedifferentfromthosewhichitestablishedwithregardtomanufactures，thegreattradeofthetowns。Byleavingthefarmernoothercustomersbuteithertheconsumersortheirimmediatefactors，thekiddersandcarriersofcorn，itendeavouredtoforcehimtoexercisethetrade，notonlyofafarmer，butofacornmerchantorcornretailer。Onthecontrary，itinmanycasesprohibitedthemanufacturerfromexercisingthetradeofashopkeeper，orfromsellinghisowngoodsbyretail。Itmeantbytheonelawtopromotethegeneralinterestofthecountry，ortorendercorncheap，without，perhaps，itsbeingwellunderstoodhowthiswastobedone。Bytheotheritmeanttopromotethatofaparticularorderofmen，theshopkeepers，whowouldbesomuchundersoldbythemanufacturer，itwassupposed，thattheirtradewouldberuinedifhewasallowedtoretailatall。
Themanufacturer，however，thoughhehadbeenallowedtokeepashop，andtosellhisowngoodsbyretail，couldnothaveundersoldthecommonshopkeeper。Whateverpartofhiscapitalhemighthaveplacedinhisshop，hemusthavewithdrawnitfromhismanufacture。Inordertocarryonhisbusinessonalevelwiththatofotherpeople，ashemusthavehadtheprofitofamanufacturerontheonepart，sohemusthavehadthatofashopkeeperupontheother。Letussuppose，forexample，thatintheparticulartownwherehelived，tenpercentwastheordinaryprofitbothofmanufacturingandshopkeepingstock;hemustinthiscasehavechargeduponeverypieceofhisowngoodswhichhesoldinhisshop，aprofitoftwentypercent。Whenhecarriedthemfromhisworkhousetohisshop，hemusthavevaluedthematthepriceforwhichhecouldhavesoldthemtoadealerorshopkeeper，whowouldhaveboughtthembywholesale。Ifhevaluedthemlower，helostapartoftheprofitofhismanufacturingcapital。Whenagainhesoldthemfromhisshop，unlesshegotthesamepriceatwhichashopkeeperwouldhavesoldthem，helostapartoftheprofitofhisshopkeepingcapital。Thoughhemightappear，therefore，tomakeadoubleprofituponthesamepieceofgoods，yetasthesegoodsmadesuccessivelyapartoftwodistinctcapitals，hemadebutasingleprofituponthewholecapitalemployedaboutthem;andifhemadelessthanhisprofit，hewasaloser，ordidnotemployhiswholecapitalwiththesameadvantageasthegreaterpartofhisneighbours。
Whatthemanufacturerwasprohibitedtodo，thefarmerwasinsomemeasureenjoinedtodo;todividehiscapitalbetweentwodifferentemployments;tokeeponepartofitinhisgranariesandstackyard，forsupplyingtheoccasionaldemandsofthemarket;andtoemploytheotherinthecultivationofhisland。
Butashecouldnotaffordtoemploythelatterforlessthantheordinaryprofitsoffarmingstock，sohecouldaslittleaffordtoemploytheformerforlessthantheordinaryprofitsofmercantilestock。Whetherthestockwhichreallycarriedonthebusinessofthecornmerchantbelongedtothepersonwhowascalledafarmer，ortothepersonwhowascalledacornmerchant，anequalprofitwasinbothcasesrequisiteinordertoindemnifyitsownerforemployingitinthismanner;inordertoputhisbusinessuponalevelwithothertrades，andinordertohinderhimfromhavinganinteresttochangeitassoonaspossibleforsomeother。Thefarmer，therefore，whowasthusforcedtoexercisethetradeofacornmerchant，couldnotaffordtosellhiscorncheaperthananyothercornmerchantwouldhavebeenobligedtodointhecaseofafreecompetition。
Thedealerwhocanemployhiswholestockinonesinglebranchofbusinesshasanadvantageofthesamekindwiththeworkmanwhocanemployhiswholelabourinonesingleoperation。