Definition.com
Exchange-value is not something that any chemis has every discovered, neither in a pearl or a diamond.
Definition.com
Exchange-value is a way for marx to explain how the capitalist mode of production managed to extract, out of peoples and histories that were all different, a homogenous and common unit for measuring human activity.
Definition.com
Exchange-value is nothing else but the living labour of man transformed into an alien force submitted on the market to the anonymous laws of exchange. It is man himself in his objectified and alienated form taking the shape of an autonomous anti-human power.
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