The difficulty exists solely because many single production goods, such for example as iron and wood, or pre-eminently common labor, enter into a variety of products. When several various products are related to one another by reason of the fact that a common production good enters into all of them, we may, following von Wieser, call them “cognate products.” If cognate products A, B, and C are made in part from the common production good P, P will derive its value from the values of A, B, and C, but the value of P itself will have a peculiar reactionary effect, yet to be described, upon the value of these products taken individually. This reaction is the phenomenon really at the foundation of the law of entrepreneur’s cost. For an instant permit a supposition quite contrary to fact. Suppose that A, B, and C are made entirely from P so that no other production good enters into them. Then the exchange values of A, B, and C will be derived solely from the “marginal” utility of these products, but their exchange values are peculiar in this, that they will be related, will be adjusted, each to the others by reason of their common origin in P. If a unit of P entering into A attains in that form a higher value that when entering into B or C, then more A’s will be made from P and less B’s and C’s. The increase in the supply of A’s will decrease their value _by decreasing the marginal utility_ of A’s.[227] This process keeps the values of A’s, B’s, and C’s in a mutual adjustment. If we carelessly confine our view to a part of this process of adjustment, we see what appears to be a determination of the value of A, the product, by the value of P, the production good. If the value of A is out of adjustment with its cost in P, and then the adjustment is effected, it is the value of A which seems to move to that of P. The value of P may seem to be the independently determining factor. As a matter of fact, in the first place, the value of A moves only when its marginal utility has been altered by a change of its supply, and in the second place, when it does move toward the value of P, that of P also moves toward it. It depends on the relative importance of A’s in comparison with all of the rest of the products of P, how far the value of A moves and how far the value of P moves in their mutual adjustment. If it is discovered that the two stars in a “double star” are approaching each other, we easily conceive that both take part in the moving. But when an apple falls to the earth it is more difficult to realize that the earth also falls toward the apple, moving its due proportion of the distance between them. In the same way, when we see that the value of some relatively unimportant product remains equal to its cost of production, we are inclined to state the case as one of pure determination of value by cost. But this “determination” is but a part, viewed by itself, of a larger process by which the supplies,