Hitherto we have spoken of economics as a science, which it is; yet like all other sciences it has an art side, which, in the minds of many, is by far the most important. The physicist, to draw another illustration from the physical sciences, is primarily concerned with the purely scientific aspects of his subject; but his labors would be largely in vain if he or some one else did not apply to the industrial arts the scientific laws and principles which he formulates in the laboratory. Discovery of the principle of air pressure is one thing, its application to a common cistern pump is another. One is science; the other, art. The same distinction occurs in economics. One of the best known economic laws is that the wants of any individual have varying degrees of intensity. Thus, any one of us may, at a given moment, desire a hat more than a pair of shoes, the shoes more than a fountain pen, and the pen more than a week-end excursion to some resort. There is no assurance, however, that we shall make our purchases in the order named. The hatter, the shoe merchant, the stationer, and the resort-owner, each presents his wares in the most attractive manner, usually by displays and advertising, in order to force the demand for his particular commodity or service to the fore - that is, to make the want for it more intense than it otherwise would have been. It may easily happen, then, that we shall forego the hat, the shoes, and the pen in order to be able to enjoy the week-end vacation. The law of the intensity of want, and its application to business in the form of attractive advertising, though intimately connected, are distinct aspects of the same thing. One is science, the other is art.