And thus we are confronted with a new difficulty, that on the one hand commodities must enter the process of exchange as embodiments of universal labor-time, while, on the other hand, this embodiment of the labor-time of individuals as social labor-time is itself a result of the process of exchange.
Every commodity becomes an exchange value by divesting itself of its use-value, or of its original nature. The commodity must therefore assume a double capacity in the process of exchange. But that second capacity of exchange value can appear only in the shape of another commodity, because only commodities confront each other in the process of exchange. How is a particular commodity to represent directly materialized universal labor-time, or—to put it differently—how is individual labor-time, which is embodied in a particular commodity to be made directly universal in character? The concrete expression of the exchange value of a commodity, i. e., of every commodity as a universal equivalent, is represented in an endless series of equations, such as: