728 THE POPULAR SCIENCE MONTHLY. 



ject that, in a pre-eminent degree, it calls for the exercise of imagina- 

 tion. "That is just what we have always said," the scoffers at politi- 

 cal economy say at once ; " so does novel-writing call for imagination, 

 and a novelist is about as well fitted for the economist's position as 

 the usual abstract thinker who masquerades as a teacher of political 

 economy." To this it is to be replied that imagination is one of the 

 chief requisites for mathematical study also ; that a novelist is not 

 necessarily a good mathematician, goes without saying. The simplest 

 propositions of solid geometry require the exercise of imagination, as, 

 for example, in the picturing of forms and solids with intersecting 

 planes. The most logical student of the severest mathematical pro- 

 cesses is called on for the exercise of this species of imagination. And 

 so it is in political economy. In learning the subject, the perception 

 of a simple general principle is often absurdly easy, but, for its assimi- 

 lation into our own thinking, it is necessary that it should have become 

 an interpreter of facts everywhere about us. To this end, it is essen- 

 tial for us to apply the abstraction, or general principle, in every pos- 

 sible case, to some concrete phenomenon. Very often, in order to 

 show the action of this single principle operating by itself, we must 

 separate all conflicting agencies from the situation — just as the physi- 

 cist experiments in a vacuum exhausted of air, for the purpose of 

 learning the full effect of a force, like gravity, when acting by itself. 

 The economist, however, is not able to reproduce a given situation to 

 the eye or ear, as is the physicist. He can not pile before him the 

 exports of the United States or England, or summon before him the 

 laboring-class or the capitalists of a country ; he must, therefore, pict- 

 ure to himself the actual facts, just as the geometrician does the solid, 

 and see how the operating principle works. This is very far from 

 " theoretical dreaming." It is at once a most difficult process, and a 

 most excellent discipline in learning how to think on such subjects. 

 To illustrate my meaning in a simple way, it is one thing to say that 

 in order to have value a commodity must satisfy some desire, and be 

 hard to get ; and quite another thing to be able to call up in the mind 

 an image which will show the application of the principle. For ex- 

 ample, to a shipwrecked sailor on a rocky island a bag of gold has no 

 value, for it can not keep him alive. It is largely by such mental ex- 

 ercise as this that a student best succeeds in assimilating the body of 

 principles which make up the science of political economy. It has 

 been frequently said to me, " I can understand the statements of the 

 writer easily, but I do not seem to be able to use the idea when called 

 upon to explain things in a different connection," This is exactly the 

 difficulty, as it is also, by struggling with the difficulty, the disciplin- 

 ary gain of our study. To understand an abstract principle, without 

 the ability to see it in the concrete form, and test its truth, is of little 

 gain to any one. This would in truth make a " doctrinaire." The 

 only " practical man," in any conceivable sense, is he who, while seeing 



