Money does not arise by convention, any more than the state does. It arises out of exchange, and arises naturally out of exchange; it is a product of the same.
money products
Money is itself a product of circulation.
Money is a crystal formed of necessity in the course of the exchanges, whereby different products of labour are practically equated to one another and thus by practice converted into commodities.
money necessity products
Communism deprives no man of the power to appropriate the products of society; all that it does is to deprive him of the power to subjugate the labour of others by means of such appropriation.
man power products society
The product of mental labor - science - always stands far below its value, because the labor-time necessary to reproduce it has no relation at all to the labor-time required for its original production.
labor products science thetimes time
An increase in the productivity of labour means nothing more than that the same capital creates the same value with less labour, or that less labour creates the same product with more capital.
products
So long as the product is sold, everything is taking its regular course from the standpoint of the capitalist producer.