_How Isolated Men measure Final Utility._--If a cave dweller possesses a store of one hundred measures of nuts, he measures the final utility and the value of this store in the manner which we have described. If he were to be deprived of the whole stock, he might starve, but this fact does not afford the basis of the value which he puts on the nuts. He measures the importance of this consumers' wealth specifically. He tests the effect of losing one measure and no more, and finds that he could lose the single measure without suffering greatly. The difference between having an appetite fully satiated and having it very nearly so is not serious. [Illustration] Let _AD_ represent the savage's total supply of food. _AB_ will represent the utility of the first unit; _CD_ of the hundredth. If we supply the food unit by unit, the utility of the successive increments will decline along the curve _BC_. When the man has a hundred units of food, no one unit of it is worth any more than the last one, since if any one were taken away, the last one could be put in the place of it. The _total absolute utility_ of the food is measured by the area _ABCD_, but the total _value_ will be represented by the rectangle _ADCE_. The area _EBC_ measures the surplus of utility contained in the earlier units in the series. _The Motive for measuring Values in Primitive Life._--Even the cave dweller would have to measure values, and would thus have to apply the principle of final utility, because he would need to spend his limited productive energies in the way that would do him the most good. When he is nearly satiated with food, he needs other things more than he does food stuffs. If he has secured so much of one product that any additional amount that he may get by an hour's labor would be of less use to him than what he could get of some other product by the same amount of labor, it is important for him to change his occupation and produce that thing of which an additional unit--which will perhaps be the final unit of this more desirable article--has the higher degree of usefulness.