6 SCIENCE PRIMERS. [NATURE AND 



that the sensations are the effects of these causes. 

 For example, if we hear a certain sound, we say it is 

 caused by a carriage going along the road, or that it is 

 the effect, or the consequence, of a carriage passing 

 along. If there is a strong smell of burning, we believe 

 it to be the effect of something on fire, and look about 

 anxiously for the cause of the smell. If we see a tree, 

 we believe that there is a thing, or object, which is the 

 cause of that appearance in our field of view. 



3. The reason "Why. Explanation. 



In the case of the smell of burning, when we find 

 on looking about, that something actually is on fire, 

 we say indifferently either that we have found out the 

 cause of the smell, or that we know the reason why 

 we perceive that smell ; or that we have explained 

 it. So that to know the reason why of anything, or to 

 explain it, is to know the cause of it. But that which 

 is the cause of one thing is the effect of another. 

 Thus, suppose we find some smouldering straw to be 

 the cause of the smell of burning, we immediately ask 

 what set it on fire, or what is the cause of its burning ? 

 Perhaps we find that a lighted lucifer match has been 

 thrown into the straw, and then we say that the lighted 

 match was the cause of the fire. But a lucifer match 

 would not be in that place unless some person had 

 put it there. That is to say, the presence of the 

 lucifer match is an effect produced by somebody as 

 cause. So we ask why did any one put the match 

 there ? Was it done carelessly, or did the person who 

 put it there intend to do so ? And if so, what was 

 his motive, or the cause which led him to do such a 

 thing? And what was the reason for his having such 



