| 1 yard of linen | = | ½ lb. of tea, |
| 1 yard of linen | = | 2 lbs. of coffee, |
| 1 yard of linen | = | 8 lbs. of bread, |
| 1 yard of linen | = | 6 yards of calico, |
may be represented as follows:
1 yard of linen = ⅛ lb. of tea + ½ lb. of coffee + 2 lbs. of bread + 1½ yards of calico.
Therefore, if we had before us the sum total of the equations, in which the value of a yard of linen is exhaustively expressed, we could represent its exchange value in the form of a series. As a matter of fact, the series is an endless one, since the circle of commodities, constantly expanding, can never be closed up. But while the exchange value of one commodity is thus measured by the use-values of all other commodities, the exchange values of all the other commodities are, in their turn, measured by the use-value of this one commodity.11
If the exchange value of one yard of linen is expressed in ½ lb. of tea, or 2 lbs. of coffee, or 6 yards of calico, or 8 lbs. of bread, etc., it follows that coffee, tea, calico, bread, etc., are equal to each other if taken in the same proportion in which they are equal to the third article, linen; consequently, linen serves as the common measure of their exchange values. Every commodity, as the embodiment of universal labor-time, i.e., as a certain quantity of universal labor-time, expresses in turn its exchange value in definite quantities of the use-values of all other commodities, and the exchange values of all the other commodities are, on the other hand, measured by the use-value of this one exclusive commodity. But as an exchange value, every commodity is at the same time the one exclusive commodity that serves as a common measure of the exchange values of all other commodities; and, on the other hand, it is but one of the many commodities in the entire series of which every commodity expresses directly its exchange value.
The value of a commodity is not affected by the number of commodities of other kinds. But the length of the series of equations in which its exchange value is realized does depend upon the greater or less variety of other commodities. The series of equations in which the value of coffee, e.g., is represented, indicates the extent to which it is exchangeable, the limits within which it performs the function of an exchange value. The exchange value of a commodity 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.
First case. Let the labor-time required for the production of commodity B remain unchanged. In that case the exchange value of A, expressed in terms of B, rises and falls with the rise and fall of the labor-time required for the production of A.
Second case. Let the labor-time required for the production of commodity A remain constant. Then the exchange value of A, expressed in terms of B, falls and rises in an inverse ratio with the rise and fall of the labor-time required for the production of B.
Third case. Let the labor-time required for the production of commodities A and B rise and fall in equal proportion. Then the expression of equivalence of A and B remains unchanged. If through some cause the productivity of all kinds of labor were to decline uniformly, so that the production of all commodities would require an equally increased quantity of labor-time, then the value of all commodities would rise, though the expression of their exchange values would remain unchanged, and the actual wealth of society would decrease, because it would have to expend more labor-time on the production of the same stock of use-values.
Fourth case. Let the labor-time required for the production of A and B rise and fall, but not uniformly; that is to say, the labor-time required for the production of A may rise, while that required for B may fall, or vice versa. All of which can be reduced to the simple case where the labor-time required for the production of one commodity remains unchanged, while that required for the other rises or falls.
The exchange value of any commodity is expressed in the use-value of any other commodity, be it in integral units or in fractions thereof. As exchange value, every commodity is capable of subdivision, like the labor-time embodied in it. The equivalence of commodities is independent of their physical divisibility as use-values, just as the sum of the exchange values of commodities is indifferent to the change of form which use-values have to undergo when converted into a single new commodity.
So far we have considered commodities from a two-fold point of view, as use-values and exchange values alternately. But a commodity as such is a direct combination of use-value and exchange value; and it is a commodity only in relation to other commodities. The actual relation between commodities constitutes the process of their exchange. It is a social process participated in by individuals independent of each other but the part they take in it is that of owners of commodities only. Their mutual relations are those of their commodities, and thus they really appear as conscious factors of the process of exchange.
A commodity is a use-value, wheat, linen, a diamond, a machine, etc., but as a commodity it is, at the same time, not a use-value. If it were a use-value for its owner, i.e., a direct means for the satisfaction of his own wants, then it would not be a commodity. To him it is rather a non-use-value; it is merely the material depository of exchange-value, or simply a means of exchange; as an active bearer of exchange value, use-value becomes a means of exchange. To the owner it is a use-value only in so far as it constitutes exchange value.12
It has yet to become a use-value, viz., to others. Not being a use-value to its owner, it is a use-value to the owners of other commodities. If it is not, then the labor expended on it was useless labor, and the result of that labor is not a commodity. On the other hand, the commodity must become a use-value to the owner himself, because his means of existence lie outside of it in the use-values of commodities not belonging to him. In order to become a use-value, the