In that case, the price expression is imaginary, like certain magnitudes used in mathematical calculations. Gold can serve as an ideal measure of value only because, in the process of exchange, it has already established itself as the money commodity. Behind the ideal measure of value lurks the hard cash. . . . Money acquires its function as a medium of circulation through being the instrument whereby the circulation of commodities is effected. . . . In so far as they really become current in place of the above-named sums of money, they mirror once more in their movement the laws of the currency of money. . . .
Paper money is a token representing gold or money.
The relation between it and the values of commodities is this, that the latter are ideally represented in the same quantities of gold as are symbolically represented in the paper. Just as all the qualitative differences between commodities are effaced in money, so money, on its part, a radical leveller, effaces all distinctions. But money is itself a commodity, an external object, capable of becoming the private property of any individual. Thus social power becomes a private power in the hands of a private person. That was why the ancients denounced money as subversive of the economic and moral order of things.