Buteveninsuchcase，thefallinthevalueoflabour—powerwouldcauseacorrespondingriseofsurplus—value，andthustheabyssbetweenthelabourer’spositionandthatofthecapitalistwouldkeepwidening。[3]
Ricardowasthefirstwhoaccuratelyformulatedthethreelawswehaveabovestated。Buthefallsintothefollowingerrors:（1）helooksuponthespecialconditionsunderwhichtheselawsholdgoodasthegeneralandsoleconditionsofcapitalistproduction。Heknowsnochange，eitherinthelengthoftheworking—day，orintheintensityoflabour;consequentlywithhimtherecanbeonlyonevariablefactor，viz。，theproductivenessoflabour;（2），andthiserrorvitiateshisanalysismuchmorethan（1），hehasnot，anymorethanhavetheothereconomists，investigatedsurplus—valueassuch，i。e。，independentlyofitsparticularforms，suchasprofit，rent，&c。Hethereforeconfoundstogetherthelawsoftherateofsurplus—valueandthelawsoftherateofprofit。Therateofprofitis，aswehavealreadysaid，theratioofthesurplus—valuetothetotalcapitaladvanced;therateofsurplus—valueistheratioofthesurplus—valuetothevariablepartofthatcapital。AssumethatacapitalCof£500ismadeupofrawmaterial，instrumentsoflabour，&c。（c）totheamountof£400;
andofwages（v）totheamountof£100;andfurther，thatthesurplus—value（s）=£100。Thenwehaverateofsurplus—values/v=£100/£100
=100%。Buttherateofprofits/c=£100/£500=20%。Itis，besides，obviousthattherateofprofitmaydependoncircumstancesthatinnowayaffecttherateofsurplus—value。IshallshowinBookIII。that，withagivenrateofsurplus—value，wemayhaveanynumberofratesofprofit，andthatvariousratesofsurplus—valuemay，undergivenconditions，expressthemselvesinasinglerateofprofit。
SECTION2WORKING—DAYCONSTANT。PRODUCTIVENESSOFLABOURCONSTANT。INTENSITYOFLABOUR