III. It follows from what has been said that the value of a good is almost never measured by the utility it actually affords,—its utility to _me_,—but by a foreign utility. In our first illustration of the two biscuits, the utilities actually afforded by the biscuits were, the satisfaction of a man’s hunger and the satisfaction of a dog’s hunger; but the value of the particular biscuit which actually satisfied the man’s hunger was measured by the use of the biscuit to the dog. In modern circumstances, where the existence of money and the presence of stock permit of goods being instantly exchanged for other goods, we can—and do almost unconsciously—change the disposition of our resources so as to shift the loss (which will define our marginal utility) to the least sensitive part. Suppose that a thrifty housewife has laid in her winter stock of butter, and that by some accident it gets spoiled. Will she be likely to do without butter for the rest of the winter? She will, of course, replace the butter, and do without some comfort or luxury which she would otherwise have allowed herself. That is to say, she will shift the loss to the least sensitive part of her total expenditure. Some part of the total satisfaction must be given up, and this will always be the least in her particular scale. In the circumstances, the satisfaction she now denies herself indicates her least urgent want. Not—be it remembered—her last conceivable want, or her last actually felt want, but the last want that was satisfied when she had the means, or the first that was deprived of its satisfaction when she had to curtail her expenses; in short, the last want satisfied. Similarly, if I am calculating the loss of value which I suffer from a horse going hopelessly lame, I do not estimate it by the satisfactions of riding and driving I am likely to lose. I replace the horse by economising in other things—perhaps by doing without my summer holiday—and the value of the horse is measured by the “foreign” utility of the summer holiday.