ual ▁oblig ations , ▁conditional ities , ▁inclus ions / ex clus ions ▁as ▁well ▁as ▁relationships ▁between ▁economic ▁actors . ▁D ifferent ▁kinds ▁of ▁prices ▁express ▁different ▁kinds ▁of ▁trad ing ▁relationships . ▁Marx ▁noted ▁that ▁the ▁forms ▁prices ▁take ▁are ▁highly ▁var ieg ated , ▁and ▁he ▁drew ▁a ▁sharp ▁distinction ▁between ▁real ▁prices ▁and ▁ideal ▁prices . ▁That ▁is ▁why ▁business men ▁assumed ▁a ▁theory ▁of ▁value , ▁even ▁if ▁they ▁were ▁not ▁aware ▁that ▁they ▁were ▁doing ▁it . ▁The ▁scientific ▁theory ▁merely ▁made ▁explicit ▁what ▁they ▁were ▁implicitly ▁assuming ▁for ▁the ▁purpose ▁of ▁doing ▁business . ▁ ▁The ▁econom ists ▁assumed ▁all ▁sorts ▁of ▁things ▁about ▁an ▁economy ▁and ▁economic ▁actors , ▁in ▁order ▁to ▁build ▁models ▁of ▁price ▁behaviour ; ▁Marx ▁thought ▁those ▁assumptions ▁themselves ▁needed ▁to ▁be ▁looked ▁at ▁and ▁the or ised ▁consist ently , ▁based ▁on ▁insight ▁into ▁the ▁historical ▁formation ▁of ▁economic ▁categories . ▁ ▁However , ▁his ▁critics ▁claim ▁that ▁his ▁own ▁approach ▁has ▁hidden ▁assumptions ▁as ▁well , ▁and ▁that ▁these ▁assumptions ▁contradict ▁pra xe ology . ▁Marx ▁anticip ated ▁this ▁criticism , ▁which ▁he ▁regarded ▁as ▁very ▁shall ow . ▁In ▁his ▁pam ph let ▁W ages , ▁price ▁and ▁profit ▁( 1 8 6 5 ), ▁Marx ▁arg ues ▁that ▁the ▁way ▁economic ▁relationships ▁observ ably ▁appear ▁to ▁the ▁individual ▁is ▁often ▁the ▁inverse ▁of ▁the ▁real ▁process , ▁considered ▁as ▁a ▁whole . ▁It ▁is ▁perfectly ▁possible ▁not ▁only ▁to ▁particip ate ▁in ▁market ▁trade ▁without ▁much ▁knowledge