PREFA TOR Y NO TE. 



ethics of teaching ? "Would any responsible scientific 

 teacher like to admit that he had not done his best 

 to separate facts from hypotheses in the minds of his 

 hearers ; and that he had not made it his chief business 

 to enable those whom he instructs to judge the latter 

 by their knowledge of the former ? 



More particularly does this obligation weigh upon 

 those who address the general public. It is indubit- 

 able, as Professor Virchow observes, that " he who 

 speaks to, or writes for, the public is doubly bound to 

 test the objective truth of that which he says." There 

 is a sect of scientific pharisees who thank God that 

 they are not as those publicans who address the public. 

 If this sect includes anybody who has attempted 

 the business without failing in it, I suspect that he 

 must have given up keeping a conscience. For 

 assuredly if a man of science, addressing the public, 

 bethinks him, as he ought to do, that the obligation 

 to be accurate to say no more than he has warranty 

 for, without clearly marking off so much as is hypo- 

 thetical is far heavier than if he were dealing with 

 experts, he will find his task a very admirable mental 

 exercise. For my own part, I am inclined to doubt 

 whether there is any method of self-discipline better 

 calculated to clear up one's own ideas about a difficult 

 subject, than that which arises out of the effort to put 

 them forth, with fulness and precision, in language 



