_Cost and Utility._--A ripe consumers' good, in exhausting itself on man, benefits him; but during the period in which it is being prepared for use, when it is receiving utilities at the hands of successive producers, it has an opposite relation to the men who handle it. In making the material useful a man confines and tires himself. He is willing to do it if the reward that he expects will more than pay for the sacrifice, but not otherwise. Moreover, this sacrifice itself has to be estimated specifically in a way that is akin to the method of measuring utilities which determines the values of goods. It is necessary for a man to gauge the sacrifice which is entailed on him, not by his labor as a whole, but by a specific part of it. He finds himself in the evening feeling the fatigue and the sense of confinement which the day of labor has imposed and asks himself how much it would burden him to work a little longer. If what he can get by this means pays for the extra sacrifice involved in thus getting it, he will work for the few minutes, but otherwise he will not. His objection to a few minutes of additional work measures what we may call the specific disutility of labor; and men, whether they be primitive or civilized, are forever making such measurements. They consider how much it will cost them to add slightly to the length of their working day or how much it will benefit them to shorten it. In this way they measure the _specific disutility_ of labor rather than the _total disutility_ of it, since they do not gauge the relief that it would afford to cease working altogether. _The Increasing Cost of Successive Periods of Labor._--It is easy to work when one is not tired, and the first hour or two of labor may even afford a pleasure that largely offsets the burden that it entails; but it is hard to work when one is tired and painfully conscious of the confinement of the shop. Adding anything to the length of a working day imposes on a man the necessity of working at the time when the burden is greatest; and shortening his day, for a like reason, relieves him of some of his most costly toil. _The Natural Length of the Working Day._--Any laborer, as his work goes on, hour after hour, is certain to reach a point at which it is unprofitable to go farther. However greatly he may need more goods, he will not need them as much as he needs rest and change. It may be that he has worked twelve hours, and that, by working longer, he can improve his wardrobe, his food, or his furnishings; but if he has a tolerable supply of such things, he will hardly choose to add to it by staying in the shop when his strength has been exhausted and he is eager to reach his home.