Sincetheexchange—valueofcommoditiesisindeednothingbutamutualrelationbetweenvariouskindsoflabourofindividualsregardedasequalanduniversallabour,i。e。,nothingbutamaterialexpressionofaspecificsocialformoflabour,itisatautologytosaythatlabouristheonlysourceofexchange—valueandaccordinglyofwealthinsofarasthisconsistsofexchange—value。Itisequallyatautologytosaythatmaterialinitsnaturalstatedoesnothaveexchange—value[5]sinceitcontainsnolabour,andthatexchange—valueassuchincludesnomaterialinanaturalstate。ItistruethatWilliamPettycalls\"labourthefatherandearththemotherofwealth\",BishopBerkeleyasks\"whetherthefourelements,andman\'slabourtherein,benotthetruesourceofwealth\",[6]
andtheAmericanThomasCooperexplainsinpopularform:
\"Takeawayfromapieceofbreadthelabourbestowedbythebakerontheflour,bythemilleronthegrainbroughttohim,bythefarmerinploughing,sowing,tending,gathering,threshing,cleaningandtransportingtheseed,andwhatwillremain？Afewgrainsofgrass,growingwildinthewoods,andunfitforanyhumanpurpose。\"[7]
Butalltheseobservationsareconcernednotwithabstractlabour,whichisthesourceofexchange—value,butwithconcretelabourasthesourceofmaterialwealth,inshortwithlabourinsofarasitproducesuse—values。
Sincetheuse—valueofthecommodityispostulated,thespecificutilityandthedefiniteusefulnessofthelabourexpendedonitisalsopostulated;