Take the case of the diving-bell, and consider how the parties to the supposed bargain manage to estimate the value of the ‹service› rendered by the one to the other in supplying him with atmospheric air. We must have a point of comparison, and that point of comparison can only be in the ‹service› which the diver renders in return. Their reciprocal demands will depend on their relative situation, on the intensity of their desires, on the greater or less need they have of each other, and on a multitude of circumstances which demonstrate that the value is in the Service, since it increases with the service. The reader may easily vary the hypothesis, so as to convince himself that the Value is not necessarily proportionate to the intensity of the efforts,—a remark which I set down here as a connecting link in the chain of reasoning, and of which I shall afterwards have occasion to make use; for my object is to prove that Value no more resides in labour than it does in utility. Nature has so constituted me that I must die if I am deprived of an opportunity, from time to time, of quenching my thirst, and the well is a league from the village. For this reason, I take the trouble every morning to go thither to fetch the water of which I have need, for in water I have recognised those ‹useful› qualities which are calculated to assuage the suffering called thirst. Want, Effort, Satisfaction—we have them all here. I have found Utility—I have not yet found Value. But, as my neighbour goes also to the fountain, I say to him—“‹Save me the pains› of this journey—‹render me the service› of bringing me water. During the time you are so occupied, I shall do something for you, I shall teach your child to spell.” This arrangement suits us both. Here is an exchange of two services, and we are enabled to pronounce that the one is ‹worth› the other. The things compared here are two efforts, not two wants and two [p139] satisfactions; for by what common standard should we compare the benefit of drinking water and that of learning to spell? By-and-by I say to my neighbour—“Your child troubles me—I should like better to do something else for you. You shall continue to bring me water, and I shall give you twopence.” If the proposal is agreed to, the Economist may, without fear of mistake, pronounce that ‹the service› «IS WORTH» ‹twopence›. Afterwards, my neighbour no longer waits to be requested. He knows by experience that every day I want water. He anticipates my wishes. At the same time, he provides water for the other villagers. In short, he becomes a water merchant. It is then that we begin to say, ‹the water› «IS WORTH» ‹twopence›.