Choice between Different Uses of the Same Thing. Immediate and Deferred Uses

The primitive housewife finding that she has a limited number of hanks of yarn from the year’s shearing, considers all the domestic wants for clothing and tries to distribute the yarn between them in such a way as to contribute as much as possible to the family wellbeing. She will think she has failed if, when it is done, she has reason to regret that she did not apply more to making, say, socks, and less to vests. That would mean that she had miscalculated the points at which to suspend the making of socks and vests respectively; that she had gone too far in the case of vests, and not far enough in that of socks; and that therefore at the points at which she actually did stop, the utility of yarn turned into socks was greater than that of yarn turned into vests. But if, on the other hand, she hit on the right points to stop at, then she made just so many socks and vests that she got an equal amount of good out of the last bundle of yarn that she applied to socks, and the last she applied to vests. This illustrates a general principle, which may be expressed thus:—