P.-J. Proudhon, System of Economical Contradictions…
“ Whence it follows that the products of human industry are, in relation to each other, genera and species, and that they form a series from the simple to the composite, according to the number and proportion of the elements, all equivalent to each other, which constitute each product. It matters little, for the present, that this series, as well as the equivalence of its elements, is expressed in practice more or less exactly by the equilibrium of wages and fortunes; our first business is with the relation of things, the economic law. ”
