_Final Utility and Labor Cost._--On the supposition that a small store of roots and nuts were incapable of being replaced by any amount of effort and that no other food were to be had, the utility of it would be indefinitely great, since the man's life would depend on this one increment of food alone. A man would value that life-sustaining good for what it would do for him and without any reference to the amount of work he had performed in order to get it, or to the amount he would have to perform in order to get another store like it. On the supposition that by labor the man could replace this essential supply, the effective utility of it would be gauged by the sacrifice he would have to make in order to replace it. The effective utility of any unit of a good that an hour's labor will produce can never be more than enough to offset the disutility of a marginal or final hour of labor; and thus even a single unit of replaceable food stuff, even when it stands alone and constitutes the whole supply, is valued according to the cost of getting another one like it. A man will prize it according to his dread of the sacrifice involved in getting the duplicate. If he gets this by adding an hour of labor to his day's work, this fact is an evidence that the importance of the original supply of the food is measured and expressed by this personal cost of replacement; and as any similar quantity in a large supply of food can be duplicated by the same amount of labor, it appears that, by a standard based on cost, the _effective_ utilities of all units are equal, that of each one is measured by the "disutility" of an hour's labor and that of the whole supply is this amount multiplied by the number of units that this supply contains.[4] [4] [Illustration]