as an embodiment of universal social labor-time is expressed in its equivalence to an endless variety of use-values.
We have seen that the exchange value of a commodity varies with the quantity of labor-time directly contained in it. Its realized exchange value, i. e., its exchange value expressed in the use-values of other commodities, must also depend on the proportion in which the labor-time spent on the production of all other commodities is changing. If, e. g., the labor-time required for the production of a bushel of wheat remained constant, while that required for the production of all other commodities doubled, the exchange value of a bushel of wheat expressed in its equivalents would become half as large as before. The result would be practically the same as if the amount of time necessary for the production of one bushel of wheat had been reduced by one-half, and that required for all other commodities had remained unchanged. The value of commodities is determined by the proportion in which they can be produced in the same labor-time. In order to see what possible changes this proportion may undergo, let us take two commodities, A and B.