Cause and Effect g 



have taken place? " but the further question " How come 

 changes? " 



This brings us to the second assumption, the principle 

 of causation. 



Cause and Effect 



One aspect of the idea of evolution, namely, that *' one 

 thing leads to another," has been thought by people for 

 thousands of years. At some time or other every person, 

 every child who thinks at all, wonders about the connection 

 between the past and the present. Even little children get 

 the notion that things which are happening now must some- 

 how have gotten started in what has happened before. We 

 may not hold to this idea permanently, or consistently; but 

 we all get it. For example, a boy finds a horseshoe and takes 

 it home, in accordance with the superstitions of his neighbor- 

 hood, hoping that it will bring him " good luck." Yet many 

 a child of six years has sense enough to ask, " How can find- 

 ing a horseshoe have anything to do with what is going to 

 happen to you? " 



Common experience suggests that everything that hap- 

 pens is related to something that happened before. Every- 

 thing that happens makes something else happen which 

 otherwise would not have happened. This idea is sometimes 

 spoken of as the principle of causation, and it is as old as the 

 records of human thought. Now frankly, we cannot say 

 exactly how one event makes another one* take place. We 

 all have noticed, however, that certain kinds of events always 

 do follow others without fail. A hole in the rain barrel will 

 " cause " the water to leak out. A break in the rope of the 

 painter's scaffold will " cause " the scaffold to drop. A col- 

 lision between a trolley car and an automobile will " cause " 

 damage to one or the other, or both. A spark applied to 

 gunpowder will start something. A drouth will somehow 

 interfere with the growth of the crop, and so on. 



While the principle of causation is part of our daily 



