146 ON SCIENCE AND ART 



the absolutely necessary condition, and yet that it 

 was insisted upon more than two hundred years ago 

 by one of the greatest men science ever possessed in 

 this country, William Harvey. 6 Harvey wrote, or at 

 least published, only two small books, one of which is 

 the well-known treatise on the circulation of the blood. 

 The other, the "Exercitationes de Generatione," is less 

 known, but not less remarkable. And not the least 

 valuable part of it is the preface, in which there occurs 

 this passage: "Those who, reading the words of authors, 

 do not form sensible images of the things referred to, 

 obtain no true ideas, but conceive false imaginations and 

 inane phantasms." You see, William Harvey's words 

 are just the same in substance as those of Mr. Freeman, 

 only they happen to be rather more than two centuries 

 older. So that what I am now saying has its application 

 elsewhere than in science; but assuredly in science the 

 condition of knowing, of your own knowledge, things 

 which you talk about, is absolutely imperative. 



I remember, in my youth, there were detestable books 

 which ought to have been burned by the hands of the 

 common hangman, for they contained questions, and 

 answers to be learned by heart, of this sort, "What is 

 a horse? The horse is termed Equus caballus; belongs 

 to the class Mammalia; order, Pachydermata ; family, 

 Solidungula." Was any human being wiser for learning 

 that magic formula? Was he not more foolish, inas- 

 much as he was deluded into taking words for knowl- 

 edge? It is that kind of teaching that one wants to 

 get rid of, and banished out of science. Make it as 

 little as you like, but, unless that which is taught is 

 based on actual observation and familiarity with facts, 

 it is better left alone. 



There are a great many people who imagine that ele- 

 8 See On Improving Natural Knowledge, p. 22. 



