Claim: Law of value is an important idea in Karl Marx's criticism of political economy.
Evidence: The law of value -LRB- German : Wertgesetz -RRB- is a central concept in Karl Marx 's critique of political economy , first expounded in his polemic The Poverty of Philosophy -LRB- 1847 -RRB- against Pierre-Joseph Proudhon , with reference to David Ricardo 's economics.See Marx , The Poverty of Philosophy , chapter 1 part 2 where Marx refers to Proudhon 's own `` law of value '' and chapter 3 , titled `` Application of the Law of the Proportionality of Value ''.