VII SCIENCE AND ART AND EDUCATION 171 



out by teachers provided with only elementary 

 knowledge. Let me assure you that that is the 

 profoundest mistake in the world. There is noth- 

 ing so difhcult to do as to write a good elementary 

 book, and there is nobody so hard to teach proper- 

 ly and well as people who know nothing about a 

 subject, and I will tell you why. If I address an 

 audience of persons who are occupied in the same 

 line of work as myself, I can assume that they 

 know a vast deal, and that they can find out the 

 blunders I make. If they don't it is their fault 

 and not mine; but when I appear before a body of 

 people who knoAV nothing about the matter, who 

 take for gospel whatever I say, surely it becomes 

 needful that I consider what I say, make sure that 

 it will bear examination, and that I do not impose 

 upon the credulity of those who have faith in me. 

 In the second place, it involves that difficult pro- 

 cess of knowing what you know so well that you 

 can talk about it as you can talk about your ordi- 

 nary business. A man can always talk about his 

 own business. He can always make it plain; but, if 

 his knowledge is hearsay, he is afraid to go beyond 

 what he has recollected, and put it before those 

 that are ignorant in such a sliape that they shall 

 comprehend it. That is why, to be a good elemen- 

 tary teacher, to teach the elements of any subject, 

 requires most careful consideration, if you are a 

 master of the subject; and, if you are not a master 

 of it, it is needful vou should familiarise vourself 



