The
law of value (German:
Wertgesetz) is a central concept in
Karl Marx's critique of
political economy, first expounded in his polemic
The Poverty of Philosophy (1847) against
Pierre-Joseph Proudhon, with reference to
David Ricardo's economics. Most generally, it refers to a regulative principle of the economic exchange of the products of human work: the relative
exchange-values of those products in trade, usually expressed by money-prices, are proportional to the average amounts of human labor-time which are currently socially necessary to produce them.