This last case suggests what is very forcibly impressed on any one who studies the cases,--that, after all, the most important element of decision is not any technical, or even any general principle of contracts, but a consideration of the nature of the particular transaction as a practical matter. A promises B to do a day's work for two dollars, and B promises A to pay two dollars for a day's work. There the two promises cannot be performed at the same time. The work will take all day, the payment half a minute. How are you to decide which is to be done first, that is to say, which promise is dependent upon performance on the other side? It is only by reference to the habits of the community and to convenience. It is not enough to say that on the principle of equivalency a man is not presumed to intend to pay for a thing until he has it. The work is payment for the money, as much as the [338] money for the work, and one must be paid in advance. The question is, why, if one man is not presumed to intend to pay money until he has money's worth, the other is presumed to intend to give money's worth before he has money. An answer cannot be obtained from any general theory. The fact that employers, as a class, can be trusted for wages more safely than the employed for their labor, that the employers have had the power and have been the law-makers, or other considerations, it matters not what, have determined that the work is to be done first. But the grounds of decision are purely practical, and can never be elicited from grammar or from logic.