3. The Equivalent form of value.
We have seen that commodity A (the linen), by expressing its value in the use-value of a commodity differing in kind (the coat), at the same time impresses upon the latter a specific form of value, namely that of the equivalent. The commodity linen manifests its quality of having a value by the fact that the coat, without having assumed a value form different from its bodily form, is equated to the linen. The fact that the latter therefore has a value is expressed by saying that the coat is directly exchangeable with it. Therefore, when we say that a commodity is in the equivalent form, we express the fact that it is directly exchangeable with other commodities.
When one commodity, such as a coat, serves as the equivalent of another, such as linen, and coats consequently acquire the characteristic property of being directly exchangeable with linen, we are far from knowing in what proportion the two are exchangeable. The value of the linen being given in magnitude, that proportion depends on the value of the coat. Whether the coat serves as the equivalent and the linen as relative value, or the linen as the equivalent and the coat as relative value, the magnitude of the coat's value is determined, independently of its value form, by the labour time necessary for its production. But whenever the coat assumes in the equation of value, the position of equivalent, its value acquires no quantitative expression; on the contrary, the commodity coat now figures only as a definite quantity of some article.
For instance, 40 yards of linen are worth—what? 2 coats. Because the commodity coat here plays the part of equivalent, because the use-value coat, as opposed to the linen, figures as an embodiment of value, therefore a definite number of coats suffices to express the definite quantity of value in the linen. Two coats may therefore express the quantity of value of 40 yards of linen, but they can never express the quantity of their own value. A superficial observation of this fact, namely, that
tude relatively to the numbers 20, 50, 100, &c., continually diminishes. Therefore the great principle that the magnitude of a whole number, such as 10, is "regulated" by the number of times unity is contained in it, falls to the ground.—[The author explains in section 4 of this chapter, p. 93, note 1, what he understands by "Vulgar Economy."—Ed.]
