Necessity is blind until it becomes conscious. Freedom is the consciousness of necessity. - Karl Marx

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.

All mysteries which lead theory to mysticism find their rational solution in human practice and in the comprehension of this practice.

"A use-value, or useful article, therefore, has value only because abstract human labour is objectified or materialized in it. How, then, is the magnitude of value to be measured? By means of the quantity of the "value-forming substance", the labour, contained in the article. This quantity is measured by its duration, and the labour-time is itself measured on the particular scale of hours, days etc."