he may know how to make a wise and intelligent decision. If he knows chemistry, physics, geology, and other sciences, he will know what he must encounter of obstacle or help in Nature in what he proposes to do. If he knows physiology and hygiene, he will know what effects on health he must expect in one course or another. If he knows political economy, he will know what effect on wealth and on the welfare of society one course or another will produce. There is no injunction, no "ought" in political economy at all. It does not assume to tell man what he ought to do, any more than chemistry tells us that we ought to mix things, or mathematics that we ought to solve equations. It only gives one element necessary to an intelligent decision, and in every practical and concrete case the responsibility of deciding what to do rests on the man who has to act. The economist, therefore, does not say to any one, You ought never to give money to charity. He contradicts anybody who says, You ought to give money to charity; and, in opposition to any such person, he says, Let me show you what difference it makes to you, to others, to society, whether you give money to charity or not, so that you
